JP7594516B2 - ENDOSCOPE DEVICE, LIGHTING METHOD, AND LIGHTING CONTROL PROGRAM - Google Patents

Description

The present invention relates to an endoscope device, a lighting method, and a lighting control program for use in an endoscope system.

In recent years, endoscopes have been used in a variety of fields, including the medical and industrial fields. Some of these endoscopes are equipped with an imaging section that captures an image of a subject. An optical image from the subject passes through an optical system provided in the insertion section and is focused on the imaging surface of an imaging element that constitutes the imaging section. The imaging element photoelectrically converts the incident optical image to obtain an imaging signal.

However, endoscopes used to observe the inside of a lumen or the like require a light source device that illuminates the subject. The illumination light generated by the light source device is irradiated onto the subject to be observed from the tip, where the imaging unit is located, via a light guide inserted through the insertion section of the endoscope. The amount of this illumination light is automatically adjusted according to the brightness of the endoscopic image generated based on the imaging signal. Patent Document 1 discloses a technology that obtains an appropriate light distribution according to the zoom state of the observation optical system.

JP 2014-230708 A

A switching stereo endoscope having two optical systems is sometimes used. In the switching stereo endoscope, the return light of the illumination light reflected by the subject passes through optical paths formed by the two optical systems (stereo optical systems) and enters a single image sensor in a time-division manner. The optical axes of the two optical systems are both decentered from the center of the image sensor's image pickup surface.
For this reason, in endoscopes employing a stereo optical system, there has been a problem in that shading (brightness gradient) occurs in the acquired image due to a mismatch between the characteristics of the image pickup element and the angle of incidence of light.
An object of the present invention is to provide an endoscope apparatus, an illumination method, and an illumination control program that can suppress the occurrence of shading.

An endoscopic device according to one aspect of the present invention includes an observation unit having two incident light paths through two optical systems whose optical axes are decentered with respect to the imaging center of a sensor and equipped with a mechanism capable of switching between the two incident light paths, an illumination unit capable of illumination in illumination modes corresponding to each of the two incident light paths, and a control unit that controls the switching of the illumination mode in response to switching of the two incident light paths , wherein the illumination unit provides illumination in an illumination mode in which a light distribution is set that corrects shading occurring in the output of the sensor in response to a difference between the angle of incidence of incident light that passes through one of the two incident light paths and enters the sensor and the incidence angle characteristics of the sensor, and an illumination mode in which a light distribution is set that corrects shading occurring in the output of the sensor in response to a difference between the angle of incidence of incident light that passes through the other of the two incident light paths and enters the sensor and the incidence angle characteristics of the sensor.

An illumination method according to one aspect of the present invention is an illumination method for an endoscopic device that includes an observation unit having two incident optical paths through two optical systems whose optical axes are decentered with respect to the imaging center of a sensor and equipped with a mechanism for switching between the two incident optical paths, an illumination unit capable of illumination in illumination modes corresponding to each of the two incident optical paths, and a control unit , wherein the illumination unit performs illumination in an illumination mode in which a light distribution is set that corrects shading occurring in the output of the sensor in accordance with a difference between an incident angle of incident light that passes through one of the two incident optical paths and enters the sensor and an incident angle characteristic of the sensor, and an illumination mode in which a light distribution is set that corrects shading occurring in the output of the sensor in accordance with a difference between an incident angle of incident light that passes through the other of the two incident optical paths and enters the sensor and an incident angle characteristic of the sensor, and the control unit controls the observation unit to enable the passage of light in one of the two incident optical paths, and controls the illumination unit to illuminate a subject in the illumination mode that corresponds to the incident optical path through which the light passes.

An illumination control program according to one aspect of the present invention is an illumination control program for controlling the illumination of an endoscopic device having an observation unit having two incident optical paths through two optical systems whose optical axes are decentered with respect to the imaging center of a sensor and equipped with a mechanism for switching between the two incident optical paths, and an illumination unit capable of illumination in illumination modes corresponding to each of the two incident optical paths, the illumination control program causes a computer to execute the steps of: performing illumination in an illumination mode in which a light distribution is set that corrects shading occurring in an output of the sensor in accordance with a difference between an incident angle of incident light that passes through one of the two incident optical paths and enters the sensor and an incident angle characteristic of the sensor, and performing illumination in an illumination mode in which a light distribution is set that corrects shading occurring in an output of the sensor in accordance with a difference between an incident angle of incident light that passes through the other of the two incident optical paths and enters the sensor and an incident angle characteristic of the sensor; controlling the observation unit to enable the passage of light in one of the two incident optical paths; and controlling the illumination unit to illuminate a subject in the illumination mode corresponding to the incident optical path through which the light passes.
An endoscopic device according to another aspect of the present invention comprises an observation unit having two incident light paths by two optical systems whose optical axes are decentered with respect to the imaging center of a sensor and equipped with a mechanism capable of switching between the two incident light paths, and an illumination unit capable of illumination in illumination modes corresponding to each of the two incident light paths, wherein the illumination unit performs illumination in an illumination mode in which a light distribution is set that corrects shading occurring in the output of the sensor in accordance with a difference between the angle of incidence of incident light that passes through one of the two incident light paths and enters the sensor and the incident angle characteristics of the sensor, and an illumination mode in which a light distribution is set that corrects shading occurring in the output of the sensor in accordance with a difference between the angle of incidence of incident light that passes through the other of the two incident light paths and enters the sensor and the incident angle characteristics of the sensor.

The present invention has the effect of suppressing the occurrence of shading.

FIG. 1 is a configuration diagram showing a configuration of an endoscope apparatus according to a first embodiment. FIG. 2 is a block diagram showing an example of the configuration of a tip portion 11 of an insertion portion 5 and a device main body 2. FIG. 2 is an explanatory diagram showing a schematic configuration of an observation optical system 21 and an image sensor 23. FIG. 1 is an explanatory diagram for explaining a cause of shading. 1 is a graph showing the illumination intensity at each position of the subject, with the illumination intensity on the horizontal axis and the position of the subject on the vertical axis. 13 is a graph showing the difference in incidence angle between the incident angle characteristic ray and the actual incident ray at each position on the imaging surface 44, with the difference in incidence angle on the horizontal axis and the position on the imaging surface 44 on the vertical axis. 1 is a graph showing the change in luminance value at each position on the imaging surface 44, with the luminance value on the horizontal axis and the position on the imaging surface 44 on the vertical axis. 5 is an explanatory diagram for explaining the function of the LED unit 26 in a manner similar to that of FIG. 4 . 13 is a graph showing the illumination intensity of the LED unit 26 at each position on the subject, with the illumination intensity on the horizontal axis and the position of the subject on the vertical axis. 13 is a graph showing the difference in incidence angle between the incident angle characteristic ray and the actual incident ray at each position on the imaging surface 44, with the difference in incidence angle on the horizontal axis and the position on the imaging surface 44 on the vertical axis. 1 is a graph showing the change in luminance value at each position on the imaging surface 44, with the luminance value on the horizontal axis and the position on the imaging surface 44 on the vertical axis. 9 is a diagram for explaining an example of an incident angle characteristic different from that shown in FIG. 8, using a description method similar to that of FIG. 8; 5 is a graph showing the illumination intensity of the LED unit 26 at each position of the subject. 6 is a graph showing the difference in the angle of incidence between the incident angle characteristic ray and the actual incident ray at each position on the imaging surface 44. 6 is a graph showing changes in luminance value at each position on the imaging surface 44. 4A to 4C are explanatory diagrams showing two examples of the arrangement of the LED unit 26. FIG. 9 is an explanatory diagram for explaining an example of switching an optical path using a description method similar to that of FIG. 8 . FIG. 9 is an explanatory diagram for explaining an example of switching an optical path using a description method similar to that of FIG. 8 . FIG. 4 is an explanatory diagram showing a configuration example of an LED unit 26 for obtaining a biased light distribution. 4 is a flowchart for explaining the operation of the first embodiment. 4 is a flowchart for explaining the operation of the first embodiment. FIG. 11 is a block diagram showing a second embodiment of the present invention. 1A and 1B are explanatory diagrams showing three examples of arranging a plurality of auxiliary light sources such as LED units 51 and 52. FIG. 9 is an explanatory diagram for explaining an example of switching an optical path using a description method similar to that of FIG. 8 . FIG. 9 is an explanatory diagram for explaining an example of switching an optical path using a description method similar to that of FIG. 8 . 10 is a flowchart for explaining the operation of the second embodiment. 10 is a flowchart for explaining the operation of the second embodiment. FIG. 11 is a block diagram showing a third embodiment of the present invention. 1A and 1B are explanatory diagrams showing three examples of arranging a plurality of auxiliary light sources such as LED units 61 and 62. FIG. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 33 is an explanatory diagram showing an example of an arrangement of LED units corresponding to FIG. 32 . FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 25 is an explanatory diagram showing an example of the arrangement of light sources 83a to 83c corresponding to FIG. 24. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 37 is a perspective view showing a cylindrical lens 86 in FIG. 36 . FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 39 is a perspective view showing a Fresnel lens 87 in FIG. 38 . FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 41 is a perspective view showing the wedge prisms 88a and 88b in FIG. 40 . FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. 5 is an explanatory diagram showing the function of a liquid crystal lens 92. FIG. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. FIG. 13 is an explanatory diagram showing an example of a configuration of a light source for obtaining a biased light distribution. 5 is a flowchart showing shading correction that can be adopted in each of the above embodiments. 11 is a graph for explaining shading correction.

(First embodiment)
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(First embodiment)
Fig. 1 is a diagram showing the configuration of an endoscope device according to a first embodiment. This embodiment makes it possible to suppress the occurrence of shading by adjusting the light distribution of illumination light that illuminates an object according to the state of eccentricity from the center in the parallax direction of the optical axes of two optical systems and the imaging surface of an imaging element (hereinafter also referred to as the imaging center). For example, in this embodiment, in addition to the main light source, an auxiliary light source for adjusting the light distribution may be adopted.

As shown in FIG. 1, the endoscope device 1 is configured to have a device main body 2 equipped with functions such as a video processor, and an endoscope 3 connected to the device main body 2. The device main body 2 has a display unit 4, such as a liquid crystal panel (LCD), on which an endoscopic image, an operation menu, etc. are displayed. This display unit 4 may be provided with a touch panel.

The endoscope 3 is composed of an insertion section 5 that serves as an endoscope insertion section that is inserted into the subject, an operation section 6 that is connected to the base end of the insertion section 5, and a universal cord 7 that extends from the operation section 6. The endoscope 3 is detachable from the device body 2 via the universal cord 7.

The insertion section 5 is configured to have, in order from the tip side, a tip section 11, a curved section 12, and a long flexible section 13. The curved section 12 is connected to the base end of the tip section 11 and is configured to bend freely, for example, in the up, down, left, and right directions. The flexible section 13 is connected to the base end of the curved section 12 and is flexible.

An imaging element 23 (see FIG. 2), such as a CMOS image sensor, is built into the tip 11 of the insertion portion 5. The imaging element 23 receives incident light that is incident on an observation window provided at the tip 11 of the insertion portion 5.

The operation unit 6 is provided with a bending joystick 6a for bending the bending portion 12 in the up, down, left, and right directions. The user can bend the bending portion 12 in a desired direction by tilting the bending joystick 6a. In addition to the bending joystick 6a, the operation unit 6 is also provided with various operation buttons for instructing the endoscope functions, such as a freeze button, a bending lock button, and a recording instruction button.

The display section 4 of the device body 2 displays an endoscopic image captured by an imaging element 23 (see FIG. 2) of an imaging unit provided in the tip section 11. Inside the device body 2, various circuits are provided, such as a control section 31 (see FIG. 2) that processes images and performs various controls, and a recording device that records processed images on a recording medium (not shown).

The operation unit 6 is further provided with image switching buttons 6b1 and 6b2 for selecting whether an image of the right eye or the left eye is to be acquired, as described below. If the display unit 4 is configured with a touch panel, the user may operate the touch panel to instruct various operations of the endoscope device 1.

Figure 2 is a block diagram showing an example of the configuration of the tip 11 of the insertion section 5 and the device body 2. Also, Figure 3 is an explanatory diagram showing the schematic configuration of the observation optical system 21 and the image sensor 23. The configuration of the tip 11 and the device body 2 will be explained using Figures 2 and 3.

The device main body 2 is configured with a control unit 31, an image sensor drive circuit 32, a light source device 33, a light source drive circuit 34, an optical path switching drive circuit 35, an LED drive circuit 36, an image processing circuit 37, a display unit 4, an operation unit 38, and a memory 39.

The control unit 31 may be configured with a processor using a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array). The control unit 31 may operate according to a program stored in the memory 39 to control each part, or may realize some or all of its functions with hardware electronic circuits. The control unit 31 controls each part of the device body 2 and also controls the overall operation of the endoscope device 1.

The imaging element drive circuit 32 generates various drive signals for driving the imaging element 23 and supplies them to the imaging element 23. The image processing circuit 37 receives the imaging signal from the imaging element 23, performs various image processing, generates an endoscopic image signal, and outputs the endoscopic image signal to the control unit 31. The control unit 31 provides the endoscopic image signal to the display unit 4, which displays an endoscopic image on the display screen of the display unit 4. The image processing circuit 37 may record the generated endoscopic image signal in the memory 39.

The light source device 33 constituting the main light source is composed of, for example, a xenon lamp, an LED, a laser diode, etc. A light guide 25a is inserted into the device body 2, the endoscope 3, and the tip portion 11, and the light source device 33 is arranged opposite the base end surface of the light guide 25a. The light source drive circuit 34 is controlled by the control unit 31 to drive the light source device 33. The light source device 33 causes illumination light to enter the base end surface of the light guide 25a under the control of the light source drive circuit 34. The illumination light entered the base end surface of the light guide 25a is emitted from an illumination window (not shown) on the tip surface of the tip portion 11, and the illumination light is irradiated onto the subject. Note that the light source device 33 is provided in the device body 2, but may be provided, for example, in the operation unit 6 of the endoscope 3.

The operation unit 38 provided on the device main body 2 is composed of various operation devices such as switches and buttons, and receives user operations on the control unit 31 and outputs operation signals to the control unit 31.

The tip 11 is provided with a stereo optical system 20, an optical path switching shutter 22, and an image sensor 23. The stereo optical system 20, the optical path switching shutter 22, and the image sensor 23 constitute an observation section (observation device). The tip 11 has a removable optical adapter 11a. As shown in FIG. 3, the stereo optical system 20 is composed of two right and left observation optical systems, a first optical system 21R and a second optical system 21L (hereinafter, when there is no need to distinguish between these, they will be referred to as the observation optical system 21), and an imaging optical system 22.

Note that FIG. 3 shows an example in which an optical adapter 11a is attached to the tip portion 11, and the optical adapter 11a is configured to include a portion of the observation optical system 21 and the imaging optical system 22, but the optical adapter 11a may be omitted, and the configuration within the optical adapter 11a may be configured at the tip of the tip portion 11.

The first optical system 21R is composed of lenses 21aR and 21bR, and the second optical system 21L is composed of lenses 21aL and 21bL. The imaging optical system 22 is composed of lenses 22a and 22b. An optical path switching shutter 24 is provided between the lenses 21bR and 21bL of the observation optical system 21 and the lens 22a of the imaging optical system 22.

The lenses 21aR, 21bR of the first optical system 21R and the lenses 21aL, 21bL of the second optical system 21L are arranged spaced apart from each other in the parallax direction. The optical axis of the first optical system 21R and the optical axis of the second optical system 21L are spaced apart in the parallax direction, and both of these optical axes extend in a direction perpendicular to the parallax direction. The optical axes of the lenses 22a, 22b constituting the imaging optical system 22 are configured to pass through the center of the imaging surface of the imaging element 23, be parallel to the optical axes of the first optical system 21R and the second optical system 21L, and pass through a position midway between the optical axes of the first optical system 21R and the second optical system 21L.

With this configuration, the return light reflected from the subject passes through an observation window (not shown) provided on the tip surface of the tip portion 11 (tip surface of the optical adapter 11a) and enters the first optical system 21R and the second optical system 21L. The optical path of the return light passing through the first optical system 21R to the imaging surface of the image sensor 23 (hereinafter also referred to as the first optical path) and the optical path of the return light passing through the second optical system 21L to the imaging surface of the image sensor 23 (hereinafter also referred to as the second optical path) are mutually different and can be switched by the optical path switching shutter 24 described later. The light passing through the first optical path and the second optical path forms an image on the imaging surface of the image sensor 23.

In FIG. 2, the image sensor 23 is connected to an image sensor drive circuit 32 and an image processing circuit 37 of the device body 2 via an image sensor cable 23s. The image sensor drive circuit 32 generates various signals for driving the image sensor 23 and provides them to the image sensor 23. The image sensor 23 is controlled by the image sensor drive circuit 32 to photoelectrically convert the optical image formed on the imaging surface to obtain an image signal. This image signal is supplied to the image processing circuit 37 via the image sensor cable 23s.

The optical path switching shutter 24 constitutes the apertures of the first and second optical paths. For example, the optical path switching shutter 24 may be configured with a blocking member that blocks the passage of light through one of the first and second optical paths and a moving mechanism that moves the blocking member to a position that blocks one of the first or second optical paths. For example, such a moving mechanism may be configured with a coil and a magnet, and configured to move the blocking member by electromagnetic action of the coil and the magnet. In this way, the optical path switching shutter 24 blocks the passage of light through one of the first and second optical paths, and forms an image on the imaging surface of the imaging element 23 only of the light that has passed through the first optical path, or forms an image on the imaging surface of the imaging element 23 only of the light that has passed through the second optical path.

For example, when switching the optical path using the optical path switching shutter 24, the user operates the operation unit 6 connected to the device body 2. As shown in FIG. 1, the operation unit 6 is provided with an image switching button 6b1 for acquiring a right eye image for blocking the passage of light from the second optical system 21L using the optical path switching shutter 24 in order to acquire a right eye image using the first optical system 21R, and an image switching button 6b2 for acquiring a left eye image for blocking the passage of light from the first optical system 21R using the optical path switching shutter 24 in order to acquire a left eye image using the second optical system 21L.

The user operates either the image switching button 6b1 for acquiring a right eye image or the image switching button 6b2 for acquiring a left eye image as desired. When the image switching button 6b1 is operated, a left eye blocking instruction signal is output from the operation unit 6 to the optical path switching drive circuit 35 via the control unit 31, and when the image switching button 6b2 is operated, a right eye blocking instruction signal is output from the operation unit 6 to the optical path switching drive circuit 35 via the control unit 31. The optical path switching shutter 24 may be switched using the operation unit 38 of the device main body 2 or the touch panel of the display unit 4. In response to the left eye blocking instruction signal or the right eye blocking instruction signal, the optical path switching drive circuit 35 outputs a drive signal to the LED unit 26 via the signal line 24s to drive the blocking member, and blocks the first optical path by the first optical system 21R or the second optical path by the second optical system 21L. In this way, an optical image having parallax via the first optical path or the second optical path is formed on the imaging surface of the imaging element 23. This allows the endoscope device 1 to form a stereo measurement or stereo observation endoscope device.

In addition, by using optical systems with different focal lengths as the first optical system 21R and the second optical system 21L, the endoscope device 1 can be used for purposes other than stereo measurement or stereo observation. In other words, by selecting an observation optical system with a desired focal length, observation at different focal lengths is possible. This embodiment is also effective when used for such purposes.

The optical adapter 11a is provided with an illumination optical system 25 having an entrance surface facing the exit surface of the light guide 25a and an exit surface facing the illumination window. The illumination optical system 25 is composed of various optical elements such as lenses such as rod lenses and prisms, and illuminates the subject with illumination light from the light source device 33 with a predetermined light distribution. In other words, the light distribution of the illumination light from the main light source is determined by the illumination optical system 25. If illumination were performed only with illumination light from the main light source, shading would occur in the image captured by the image sensor 23 due to misalignment of the optical axes of the first optical system 21R and the second optical system 21L.

(Relationship between stereo optical system and shading)
Fig. 4 is an explanatory diagram for explaining the cause of shading. Fig. 5 is a graph showing the illumination intensity at each position of the subject, with the illumination intensity on the horizontal axis and the position of the subject on the vertical axis. Fig. 6 is a graph showing the difference in incidence angle between the incidence angle characteristic ray and the actual incident ray at each position of the imaging surface 44, with the difference in incidence angle on the horizontal axis and the position of the imaging surface 44 on the vertical axis. Fig. 7 is a graph showing the change in luminance value at each position of the imaging surface 44, with the luminance value on the horizontal axis and the position of the imaging surface 44 on the vertical axis.

The first optical path 41 and the second optical path 42 are, for example, optical paths formed by the first optical system 21R and the optical system 21L. As described above, the optical axes of the first optical system 21R and the second optical system 21L are arranged at a predetermined distance in the parallax direction (the vertical direction on the paper surface of FIG. 4). Light reflected by the subject 43 passes through the first optical path 41 or the second optical path 42 and is incident on the imaging surface 44 that constitutes the image sensor 23.

Now, assume that the subject 43 is illuminated with a substantially uniform amount of light by the illumination optical system 25, which emits illumination light from the light source device 33, which is the main light source. An example will be described in which the return light from the subject 43 passes through the first optical path 41 and enters the imaging surface 44 of the image sensor 23. The solid lines in Figure 4 indicate that the light from points A', B', and C' on the subject 43 is imaged at points A, B, and C on the imaging surface 44.

Generally, when an image sensor receives light from a point light source in front of the imaging center, shading occurs, where the amount of light is less at the periphery of the imaging surface than at the center of the imaging surface. Some image sensors change the arrangement and amplification characteristics of microlenses according to the pixel position in accordance with the angle of incidence of light incident on the imaging surface, making it possible to receive light at the periphery with the same sensitivity as at the center. In this way, the characteristics of the light incidence angle set for each imaging surface position so that light can be received with uniform sensitivity regardless of the position within the imaging surface are called incidence angle characteristics.

The dashed lines in FIG. 4 show such incident angle characteristics by rays showing incident angles based on the incident angle characteristics (hereinafter referred to as incident angle characteristic rays), and show characteristics similar to the incident angle characteristics set in a general imaging element. The incident angle characteristics shown in FIG. 4 are such that, for example, when light is incident at an incident angle perpendicular to the imaging surface 44 at the center of the imaging surface 44 and at an incident angle of a predetermined angle at the periphery of the imaging surface 44, the light receiving sensitivity becomes uniform within the imaging surface 44, enabling optimal imaging. In other words, when light is incident at the same incident angle as the incident angle characteristic rays at all positions on the imaging surface 44, uniform sensitivity is obtained regardless of the position on the imaging surface 44.

However, such incident angle characteristics assume that the optical axis of the observation optical system is not decentered from the imaging center for a single imaging element. However, in a stereo optical system, two observation optical systems shifted in the parallax direction are used, and the optical axes of these observation optical systems are decentered from the imaging center of the imaging element 23. As a result, the difference in incident angle between the incident angle characteristic ray at positions A, B, and C of the imaging surface 44 and the actual incident light ray at positions A, B, and C of the imaging surface 44 differs for each position. At each position on the imaging surface 44, the greater the difference in incident angle, the lower the light receiving sensitivity. If the difference in incident angle between the incident angle characteristic ray and the incident light ray at positions A, B, and C are θA, θB, and θC, respectively, in the example of FIG. 4, θA<θB<θC, as shown in FIG. 6. Therefore, when a uniform amount of reflected light is obtained from each position on the subject 43 as shown in FIG. 5, the captured image 45 obtained by the image sensor 23 has shading in which the area corresponding to position A is the brightest and gradually becomes darker toward the area of position C, as shown in FIG. 7.

(auxiliary light source)
Therefore, in this embodiment, an auxiliary light source that suppresses the occurrence of shading is adopted.

In FIG. 2, the LED unit 26 constitutes an auxiliary light source. The LED unit 26, which constitutes the illumination section (illumination device), is composed of an LED (light emitting diode) (not shown) and an illumination optical system. The illumination optical system of the LED unit 26 is composed of various optical elements such as lenses and prisms, and illuminates the subject with illumination light generated by the LED with a predetermined light distribution.

The LED unit 26 is connected to an LED drive circuit 36 in the device body 2 by wiring 26s. The LED drive circuit 36 is controlled by the control unit 31 to drive the LED unit 26. This allows the LED unit 26 to emit illumination light in various illumination modes. That is, the LED unit 26 is configured so that the intensity of the emitted illumination light can be changed, and as described below, is configured so that illumination with a predetermined light distribution can be provided. Note that the LED unit 26 may also be configured so that the light distribution can be changed.

Next, the operation of the embodiment configured in this manner will be described with reference to Figs. 8 to 11. Fig. 8 is an explanatory diagram for explaining the operation of the LED unit 26 in the same manner as Fig. 4. Fig. 9 is a graph showing the illumination intensity of the LED unit 26 at each position of the subject, with the illumination intensity on the horizontal axis and the position of the subject on the vertical axis. Fig. 10 is a graph showing the difference in incidence angle between the incidence angle characteristic ray and the actual incident ray at each position of the imaging surface 44, with the difference in incidence angle on the horizontal axis and the position of the imaging surface 44 on the vertical axis. Fig. 11 is a graph showing the change in luminance value at each position of the imaging surface 44, with the luminance value on the horizontal axis and the position of the imaging surface 44 on the vertical axis.

The first optical path 41 formed by the first optical system 21R and the second optical path 42 formed by the second optical system 21L are arranged with their optical axes spaced a predetermined distance apart in the parallax direction (the vertical direction on the paper). The subject 43 is illuminated with a substantially uniform amount of light by the illumination optical system 25, which emits illumination light from the light source device 33, which is the main light source.

In the example of FIG. 8, the LED unit 26, which is an auxiliary light source, is disposed approximately in the center between the optical axis of the first optical path 41 and the optical axis of the second optical path 42 in the parallax direction. In FIG. 8, the approximate illumination range of the LED unit 26 is shown by a straight line extending from the LED unit 26. The LED unit 26 provides illumination with a light distribution such that the amount of light is greatest at position C' of the subject 43, and decreases from position C' to position A'.

Now, suppose that the subject 43 is illuminated by the illumination optical system 25 constituting the main light source and the LED unit 26 constituting the auxiliary light source, and the return light from the subject 43 passes through the first optical path 41 and is incident on the imaging surface 44 of the image sensor 23. The solid lines in Figure 8 indicate that the light from points A', B', and C' on the subject 43 is imaged at points A, B, and C on the imaging surface 44. The dashed lines in Figure 8 indicate the incident angle characteristic rays.

As described above, if the difference in the incidence angle between the incident angle characteristic ray and the incident ray at positions A, B, and C is θA, θB, and θC, respectively, in the example of Figure 8, θA < θB < θC, as shown in Figure 10. Therefore, as in the example of Figure 4, if a uniform amount of reflected light is obtained from each position of the subject 43, shading will occur in the captured image 45 obtained by the image sensor 23, where the area corresponding to position A is the brightest and gradually becomes darker toward the area of position C.

In contrast, in this embodiment, as shown in FIG. 9, if the illumination intensity (light amount) at positions C', B', and A' of the subject 43 by the LED unit 26 is LC', LB', and LA', respectively, then LC'>LB'>LA'. That is, the light distribution of the LED unit 26 has a characteristic that the illumination intensity is strongest at position C', and the illumination intensity decreases as it moves away from position C' toward position A'. That is, the light distribution of the LED unit 26 is given a characteristic that the area corresponding to position C on the imaging surface 44 is brightened, and the area gradually becomes darker as it moves away from position C toward the area of position A. As a result, as shown in FIG. 11, a uniform brightness can be obtained over the entire area including positions A and C on the imaging surface 44. That is, by appropriately setting the light distribution of the LED unit 26, it is possible to make the sensitivity at each position on the imaging surface 44 uniform within the imaging surface 44. In this way, as shown in FIG. 8, shading of the captured image 45a obtained by the imaging element 23 is eliminated.

Note that in FIG. 8, an example is described in which the return light from the subject 43 passes through the first optical path 41. However, even when the return light from the subject 43 passes through the second optical path 42, it is clear that the occurrence of shading can be suppressed by appropriately setting the light distribution of the LED unit 26.

In the above explanation, the LED unit 26 is disposed approximately in the center between the optical axis of the first optical path 41 and the optical axis of the second optical path 42 in the parallax direction, and the light distribution is described as having the strongest illumination intensity at position C', and the illumination intensity decreases as it moves away from position C' toward position A'. However, the light distribution of the LED unit 26 is not limited to this, and is set according to the incident angle characteristics of the imaging element 23, and the position at which the LED unit 26 is provided is not particularly limited as long as the desired light distribution can be obtained.

(Another example of incident angle characteristics) (Straight incident angle characteristics)
Fig. 12 is an explanatory diagram for explaining an example of an incident angle characteristic different from that of Fig. 8, using the same description method as Fig. 8. Also, Figs. 13 to 15 are graphs for explaining the example of Fig. 12, using the same description method as Figs. 9 to 11, respectively. That is, Fig. 13 is a graph showing the illumination intensity of the LED unit 26 at each position of the subject, Fig. 14 is a graph showing the difference in incident angle between the incident angle characteristic light beam and the actual incident light beam at each position of the imaging surface 44, and Fig. 15 is a graph showing the change in luminance value at each position of the imaging surface 44.

In the example of FIG. 12, the LED unit 26, which is an auxiliary light source, is disposed at the end of the first optical path 41 that is the furthest from the second optical path 42 in the parallax direction. The LED unit 26 in FIG. 12 provides illumination with a light distribution such that the amount of light is greatest at position A' on the subject 43, and the amount of light decreases from position A' to position C'.

Now, suppose that the subject 43 is illuminated by the illumination optical system 25 constituting the main light source and the LED unit 26 constituting the auxiliary light source, and the return light from the subject 43 passes through the first optical path 41 and is incident on the imaging surface 44 of the image sensor 23. The solid lines in FIG. 12 indicate that the light from each of points A', B', and C' on the subject 43 is imaged at points A, B, and C on the imaging surface 44. The dashed lines in FIG. 12 indicate the incident angle characteristic light rays. That is, the example in FIG. 12 shows an example in which an element that can obtain uniform light receiving sensitivity at each position on the imaging surface 44 when light rays are incident on the entire imaging surface 44 from a direction perpendicular to the imaging surface is used as the imaging element 23.

If the difference in the incidence angle between the incident angle characteristic ray and the incident ray at positions A, B, and C is θA, θB, and θC, respectively, in the example of FIG. 12, θA>θB>θC, as shown in FIG. 14. Therefore, when a uniform amount of reflected light is obtained from each position of the subject 43, as in the example of FIG. 4, the captured image 47 obtained by the image sensor 23 will have shading, with the area corresponding to position A being the darkest and gradually becoming brighter toward the area corresponding to position C.

In contrast, in this embodiment, as shown in FIG. 13, if the illumination intensity (light amount) at positions A', B', and C' of the subject 43 by the LED unit 26 is LA', LB', and LC', respectively, then LA'>LB'>LC'. That is, the light distribution of the LED unit 26 has a characteristic that the illumination intensity is strongest at position A', and the illumination intensity decreases as it moves away from position A' toward position C'. That is, in the example of FIG. 12, the light distribution of the LED unit 26 is given a characteristic that the area corresponding to position A on the imaging surface 44 is brightened, and the area corresponding to position C is gradually darkened as it moves away from position A. As a result, as shown in FIG. 15, a uniform brightness can be obtained over the entire area including positions A and C on the imaging surface 44. That is, by appropriately setting the light distribution of the LED unit 26, it is possible to make the sensitivity at each position on the imaging surface 44 uniform within the imaging surface 44. In this way, as shown in FIG. 12, shading of the captured image 47 obtained by the imaging element 23 is eliminated.

Note that in FIG. 12, an example is described in which the return light from the subject 43 passes through the first optical path 41. However, even when the return light from the subject 43 passes through the second optical path 42, it is clear that the occurrence of shading can be suppressed by appropriately setting the light distribution of the LED unit 26.

(Example of auxiliary light source placement)
FIG. 16 is an explanatory diagram showing two examples of the arrangement of the LED units 26. In FIG.

Figure 16 shows the tip surface of the optical adapter 11a. The tip surface of the optical adapter 11a faces the exit surface of the illumination optical system 25, the entrance surface of the first optical system 21R, and the entrance surface of the second optical system 21L. The example in the upper part of Figure 16 shows that the exit surface of the illumination optical system 26a constituting the LED unit 26 faces the tip surface of the optical adapter 11a. The exit surface of the illumination optical system 26a has an arc shape of a predetermined width along the circumference of the optical adapter 11a, and has a shape that is line-symmetrical with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

The example in the lower part of Figure 16 shows that the exit surface of the illumination optical system 26b constituting the LED unit 26 faces the tip surface of the optical adapter 11a. The exit surface of the illumination optical system 26b is provided at a position midway between the optical axes of the optical systems 21R and 21L in the parallax direction, has a rectangular shape, and is configured in a shape that is line-symmetrical with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

(Switching of optical path)
17 and 18 are explanatory diagrams for explaining an example of switching an optical path, using the same description method as in FIG.

In the examples of Figures 17 and 18, the LED unit 26, which is an auxiliary light source, is capable of illumination in first and second lighting modes that have mutually different light distributions. For example, the LED unit 26 is capable of changing the light distribution by changing the positional relationship between the light-emitting surface of the LED and the lighting optical system facing this light-emitting surface. For example, by providing a movement mechanism that moves the relative position between the lighting optical system and the light-emitting surface of the LED, and driving this movement mechanism by the LED drive circuit 36, it is possible to obtain different light distributions.

In the examples of Figs. 17 and 18, the LED unit 26, which is an auxiliary light source, is disposed in the parallax direction approximately in the center between the optical axis of the first optical path 41 and the optical axis of the second optical path 42. In the example of Fig. 17, the LED unit 26 provides illumination in a first illumination mode having a light distribution in which the amount of light is greatest at position C' of the subject 43 and decreases from position C' to position A'.

As shown in FIG. 17, subject 43 is illuminated by illumination optical system 25 constituting the main light source and LED unit 26 constituting the auxiliary light source, and the return light from subject 43 passes through first optical path 41 and enters imaging surface 44 of image sensor 23. The solid lines in FIG. 17 indicate that in this case, light from points A', B', and C' on subject 43 is imaged at points A, B, and C on imaging surface 44. The dashed lines in FIG. 17 indicate incident angle characteristic rays.

If the difference in incidence angle between the incident light and the incident angle characteristic light ray at positions A, B, and C is θA, θB, and θC, respectively, in the example of Figure 17, θA < θB < θC. Therefore, as in the example of Figure 4, when a uniform amount of reflected light is obtained from each position of the subject 43, shading occurs in the captured image 48 obtained by the image sensor 23, where the area corresponding to position A is the brightest and gradually becomes darker toward the area corresponding to position C.

In contrast, in the example of FIG. 17, if the illumination intensity (light amount) at positions A', B', and C' of the subject 43 by the LED unit 26 is LA', LB', and LC', respectively, then LA'<LB'<LC'. That is, the light distribution of the LED unit 26 has a characteristic that the illumination intensity is strongest at position C', and the illumination intensity decreases as the distance from position C' increases toward position A'. That is, in the example of FIG. 17, the light distribution of the LED unit 26 darkens the area corresponding to position A on the imaging surface 44, and gradually brightens the area corresponding to position C as the distance from position A increases. This makes it possible to obtain uniform brightness over the entire area including positions A to C on the imaging surface 44. That is, by appropriately setting the light distribution of the LED unit 26, it is possible to make the sensitivity at each position on the imaging surface 44 uniform within the imaging surface 44. In this way, as shown in FIG. 17, shading of the captured image 48 obtained by the imaging element 23 is eliminated.

On the other hand, in the example of FIG. 18, the LED unit 26 performs illumination in a second illumination mode having a light distribution in which the amount of light at position D' of the subject 43 is the largest and the amount of light decreases from position D' to position F'. Now, as shown in FIG. 18, the subject 43 is illuminated by the illumination optical system 25 constituting the main light source and the LED unit 26 constituting the auxiliary light source, and the return light from the subject 43 passes through the second optical path 42 and enters the imaging surface 44 of the imaging element 23. The solid lines in FIG. 18 indicate that the light from each of points D', E', and F' on the subject 43 is imaged at points D, E, and F on the imaging surface 44. The dashed lines in FIG. 18 indicate the incident angle characteristic light rays.

If the differences in the incidence angles between the incident angle characteristic ray and the incident ray at positions D, E, and F are θD, θE, and θF, respectively, then in the example of Figure 18, θD>θE>θF. Therefore, as in the example of Figure 4, when a uniform amount of reflected light is obtained from each position of the subject 43, the captured image 49 obtained by the image sensor 23 will have shading in which the area corresponding to position D is the darkest and gradually becomes brighter toward the area corresponding to position F.

In contrast, in the example of FIG. 18, if the illumination intensity (light amount) of the LED unit 26 at positions D', E', and F' of the subject 43 is LD', LE', and LF', respectively, then LD'>LE'>LF'. That is, the light distribution of the LED unit 26 has a characteristic that the illumination intensity is strongest at position D', and the illumination intensity decreases as it moves away from position D' toward position F'. That is, in the example of FIG. 18, the light distribution of the LED unit 26 is given a characteristic that the area corresponding to position D on the imaging surface 44 is brightened, and the area corresponding to position F is gradually darkened as it moves away from position D. As a result, a uniform brightness can be obtained over the entire area including positions A to C of the imaging surface 44. That is, by appropriately setting the light distribution of the LED unit 26, it is possible to make the sensitivity at each position of the imaging surface 44 uniform within the imaging surface 44. In this way, as shown in FIG. 18, shading of the captured image 49 obtained by the imaging element 23 is eliminated.

In this way, in the examples of Figures 17 and 18, even when the first optical system 21R and the second optical system 21L are switched for stereo measurement or stereo observation, the illumination mode of the LED unit 26 can be switched between the first illumination mode and the second illumination mode in response to switching between the first optical system 21R and the second optical system 21L, thereby making the sensitivity at each position on the imaging surface 44 uniform across the imaging surface 44 and suppressing the occurrence of shading.

(Biased light distribution)
In this way, the LED unit 26 can obtain a biased light distribution in the parallax direction. The biased light distribution is a distribution of illumination intensity in which the illumination intensity changes, for example, from bright illumination to dark illumination from one side of the illumination range to the other side in the parallax direction. For example, the LED unit 26 may form a biased light distribution that is not line-symmetrical with respect to a straight line parallel to each optical axis on a plane parallel to a plane including the optical axes of the first optical system 21R and the second optical system 21L.

Figure 19 is an explanatory diagram showing an example of the configuration of an LED unit 26 for obtaining a biased light distribution. The LED unit 26 shown in the upper part of Figure 19 shows an example in which a prism 26p is arranged opposite a hemispherical light exit surface 26c. The bottom surface of the light exit surface 26c is arranged so as to be perpendicular to the optical axis of the optical systems 21R and 21L. A biased light distribution can be obtained by the action of the prism 26p.

The LED unit 26 shown in the middle of Figure 19 shows an example in which a lens 26r is arranged opposite a hemispherical light exit surface 26c. The bottom surface of the light exit surface 26c is arranged so as to be perpendicular to the optical axis of the optical systems 21R and 21L. The optical axis of the lens 26r is offset from the center of the bottom surface of the light exit surface 26c and is decentered in the parallax direction. This allows the LED unit 26 in the middle of Figure 19 to obtain a biased light distribution.

The LED unit 26 shown in the lower part of Figure 19 has a hemispherical light exit surface 26c with a line perpendicular to the bottom surface tilted with respect to the optical axis of the optical systems 21R and 21L. This allows the LED unit 26 in the lower part of Figure 19 to obtain a biased light distribution.

Next, the operation of the embodiment configured in this manner will be described with reference to Figs. 20 and 21. Figs. 20 and 21 are flow charts for explaining the operation of the first embodiment. Note that Fig. 20 shows an example in which a user performs an optical path switching operation, and Fig. 21 shows an example in which optical path switching is performed automatically for stereo measurement, etc.

First, we will explain the case where the user performs an optical path switching operation.

The control unit 31 determines whether or not an optical path switching operation has occurred in step S1 of FIG. 20. For example, it is assumed that the user operates an operation button (not shown) for switching the optical path. When the control unit 31 detects the user's optical path switching operation (YES judgment in S1), it determines in step S2 whether or not the optical path through which the current return light is incident is the first optical path 41 by the first optical system 21R. If the current optical path is the first optical path 41 by the first optical system 21R (YES judgment in S2), that is, in the state of FIG. 17, the control unit 31 instructs the optical path switching drive circuit 35 to switch to the second optical path 42 by the second optical system 21L and instructs the LED drive circuit 36 to illuminate in the second lighting mode.

As a result, the optical path switching drive circuit 35 blocks the optical path of the first optical system 21R by the optical path switching shutter 24. Also, the LED drive circuit 36 switches the illumination mode of the LED unit 26 from the first illumination mode to the second illumination mode. This results in the state shown in FIG. 18, where an optical image of the subject is captured using the second optical system 21L, and an imaging signal is output from the imaging element 23. The image processing circuit 37 performs image processing on the imaging signal from the imaging element 23, and provides the captured image to the display unit 4 for display. In this way, an endoscopic image is displayed on the display screen of the display unit 4. The occurrence of shading in this endoscopic image is suppressed by the LED unit 26, which is an auxiliary light source, and a high-quality image is displayed on the display screen of the display unit 4.

On the other hand, in step S2, if the control unit 31 determines that the current optical path is not the first optical path 41 by the first optical system 21R (NO determination in S2), that is, in the state shown in FIG. 18, the control unit 31 instructs the optical path switching drive circuit 35 to switch to the first optical path 41 by the first optical system 21R, and instructs the LED drive circuit 36 to illuminate in the first lighting mode.

As a result, the optical path switching drive circuit 35 blocks the optical path of the second optical system 21L by the optical path switching shutter 24. Also, the LED drive circuit 36 switches the illumination mode of the LED unit 26 from the second illumination mode to the first illumination mode. This results in the state shown in FIG. 17, where an optical image of the subject is captured using the first optical system 21R, and an imaging signal is output from the imaging element 23. The image processing circuit 37 performs image processing on the imaging signal from the imaging element 23, and provides the captured image to the display unit 4 for display. In this way, an endoscopic image is displayed on the display screen of the display unit 4. The occurrence of shading in this endoscopic image is suppressed by the LED unit 26, which is an auxiliary light source, and a high-quality image is displayed on the display screen of the display unit 4.

Next, we will explain the case where automatic optical path switching is performed.

In step S5 of FIG. 21, the control unit 31 starts executing the stereo measurement mode. In step S6, the control unit 31 instructs the optical path switching drive circuit 35 to switch to the first optical path 41 by the first optical system 21R, and instructs the LED drive circuit 36 to illuminate in the first illumination mode. This results in the state shown in FIG. 17, where an optical image of the subject is formed on the image sensor 23 via the first optical path 41. The control unit 31 obtains an imaging signal from the image sensor 23 to obtain an image (first image) (step S7).

Next, in step S8, the control unit 31 instructs the optical path switching drive circuit 35 to switch to the second optical path 42 by the second optical system 21L, and instructs the LED drive circuit 36 to illuminate in the second illumination mode. This results in the state shown in FIG. 18, where an optical image of the subject is formed on the image sensor 23 via the second optical path 42. The control unit 31 obtains an imaging signal from the image sensor 23 to obtain an image (second image) (step S9).

The control unit 31 performs measurements using the acquired first and second images. The occurrence of shading in both the first and second images is suppressed by the LED unit 26, which serves as an auxiliary light source, and highly accurate measurement results can be obtained.

When performing stereoscopic observation, steps S6 to S9 are repeated to obtain a stereoscopic image using the first and second images.

Second Embodiment
Fig. 22 is a block diagram showing a second embodiment of the present invention. In Fig. 12, the same components as those in Fig. 2 are given the same reference numerals and the description thereof will be omitted. This embodiment differs from the configuration of the tip 11 of the insertion part in Fig. 2 in that two LED units 51 and 52 are used instead of the LED unit 26. In the first embodiment, an example in which one auxiliary light source is used has been described, but this embodiment employs multiple auxiliary light sources.

Each of the LED units 51 and 52 constitutes an auxiliary light source. Although FIG. 22 shows an example in which two auxiliary light sources are used, three or more auxiliary light sources may be used. The LED units 51 and 52 have the same configuration as the LED unit 26. Both of the LED units 51 and 52 are composed of LEDs and an illumination optical system (not shown). The illumination optical system of the LED units 51 and 52 is composed of various optical elements such as lenses and prisms, and illuminates the subject with illumination light generated by the LEDs with a predetermined light distribution.

The LED units 51 and 52 are driven by an LED drive circuit 53 in the device body 2. The LED drive circuit 53 is controlled by the control unit 31 to drive the LED units 51 and 52. This allows the LED units 51 and 52 to emit illumination light in the illumination mode specified by the LED drive circuit 53. In other words, the LED units 51 and 52 are designed to independently control the light distribution of the illumination light they emit. For example, the LED drive circuit 53 may perform illumination control such that the LED unit 51 is turned on in a first illumination mode corresponding to the first optical path 41, and the LED unit 52 is turned on in a second illumination mode corresponding to the second optical path 42.

(Example of auxiliary light source placement)
FIG. 23 is an explanatory diagram showing three examples of arranging a plurality of auxiliary light sources such as LED units 51 and 52. In FIG.

Figure 23 shows the tip surface of the optical adapter 11a. The tip surface of the optical adapter 11a faces the exit surface of the illumination optical system 25, the entrance surface of the first optical system 21R, and the entrance surface of the second optical system 21L. The example in the upper part of Figure 23 shows that the exit surface of the illumination optical system 27a constituting the LED unit 51 and the exit surface of the illumination optical system 27b constituting the LED unit 52 face the tip surface of the optical adapter 11a. The exit surfaces of the illumination optical systems 27a and 27b are arranged side by side in the parallax direction near the entrance surface of the second optical system 21L and the entrance surface of the first optical system 21R, respectively, on the central side of the parallax direction of the tip surface of the optical adapter 11a. That is, the illumination optical systems 27a and 27b are arranged in line symmetry with each other with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

The example in the middle of Figure 23 shows that the exit surfaces of the illumination optical systems 28a and 28b constituting the LED units 51 and 52 face the tip surface of the optical adapter 11a. The exit surfaces of the illumination optical systems 28a and 28b are disposed near the circumference of the optical adapter 11a near the entrance surface of the first optical system 21R and the entrance surface of the second optical system 21L, respectively. That is, the illumination optical systems 28a and 28b are disposed symmetrically with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

The example in the lower part of Fig. 23 shows that the exit surface of the illumination optical system 29 faces outside the illumination optical systems 28a and 28b shown in the middle part of Fig. 23. The exit surface of the illumination optical system 29 is provided at a position midway between the optical axes of the optical systems 21R and 21L in the parallax direction, has a rectangular shape, and is configured in a shape that is line-symmetrical with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

(Switching of optical path)
24 and 25 are explanatory diagrams for explaining an example of switching an optical path, using the same description method as in FIG. 8. In FIG.

24 and 25, of the LED units 51 and 52 serving as auxiliary light sources, the LED unit 51 can provide illumination in a first illumination mode with a light distribution corresponding to the first light path 41, and the LED unit 52 can provide illumination in a second illumination mode with a light distribution corresponding to the second light path 42. That is, the LED drive circuit 53 causes the LED unit 51 to provide illumination in a first illumination mode having a light distribution such that the amount of light is greatest at position C' of the subject 43 and decreases from position C' to position A' (FIG. 24). The LED unit 52 is controlled by the LED drive circuit 53 to provide illumination in a second illumination mode having a light distribution such that the amount of light is greatest at position D' of the subject 43 and decreases from position D' to position F' (FIG. 25).

As shown in FIG. 24, the subject 43 is illuminated by the illumination optical system 25 constituting the main light source and the LED unit 51 constituting the auxiliary light source, and the return light from the subject 43 passes through the first optical path 41 and is incident on the imaging surface 44 of the image sensor 23. The solid lines in FIG. 24 indicate that in this case, light from points A', B', and C' on the subject 43 is imaged at points A, B, and C on the imaging surface 44. The dashed lines in FIG. 24 indicate the incident angle characteristic rays.

If the difference in the incidence angle between the incident light and the incident angle characteristic light at positions A, B, and C is θA, θB, and θC, respectively, in the example of Figure 24, θA < θB < θC. Therefore, as in the example of Figure 4, when a uniform amount of reflected light is obtained from each position of the subject 43, shading occurs in the captured image 50a obtained by the image sensor 23, where the area corresponding to position A is the brightest and gradually becomes darker toward the area corresponding to position C.

24, the LED unit 52 is off and the LED unit 51 is turned on. If the illumination intensities (light amounts) of the LED unit 51 at positions A', B', and C' of the subject 43 are LA', LB', and LC', respectively, then LA'<LB'<LC'. That is, the light distribution of the LED unit 51 has a characteristic that the illumination intensity is strongest at position C', and the illumination intensity decreases as it moves away from position C' toward position A'. That is, in the example of FIG. 24, the light distribution of the LED unit 51 darkens the area corresponding to position A on the imaging surface 44, and gradually brightens the area corresponding to position C as it moves away from position A. This makes it possible to obtain uniform brightness over the entire area including positions A to C of the imaging surface 44. That is, by appropriately setting the light distribution of the LED unit 26, it is possible to make the sensitivity at each position of the imaging surface 44 uniform within the imaging surface 44. In this way, shading in the captured image 50a obtained by the imaging element 23 is eliminated, as shown in FIG. 24.

On the other hand, in the example of FIG. 25, the LED unit 51 is off and the LED unit 52 is on. The LED unit 52 performs illumination in a second illumination mode having a light distribution in which the amount of light at the position D' of the subject 43 is the largest and the amount of light decreases from the position D' to the position F'. Now, as shown in FIG. 25, the subject 43 is illuminated by the illumination optical system 25 constituting the main light source and the LED unit 52 constituting the auxiliary light source, and the return light from the subject 43 passes through the second optical path 42 and enters the imaging surface 44 of the imaging element 23. The solid lines in FIG. 25 indicate that the light from each point D', E', F' on the subject 43 is imaged at the points D, E, F on the imaging surface 44. The dashed lines in FIG. 25 indicate the incident angle characteristic light rays.

If the difference in incidence angle between the incident angle characteristic ray and the incident ray at positions D, E, and F is θD, θE, and θF, respectively, then in the example of Figure 25, θD>θE>θF. Therefore, when a uniform amount of reflected light is obtained from each position of the subject 43 as in the example of Figure 4, the captured image 50b obtained by the image sensor 23 will have shading in which the area corresponding to position D is the darkest and gradually becomes brighter toward the area corresponding to position F.

In contrast, in the example of FIG. 25, if the illumination intensity (light quantity) at positions D', E', and F' of the subject 43 by the LED unit 52 is LD', LE', and LF', respectively, then LD'>LE'>LF'. That is, the light distribution of the LED unit 52 has a characteristic that the illumination intensity is strongest at position D', and the illumination intensity decreases as it moves away from position D' toward position F'. That is, in the example of FIG. 25, the light distribution of the LED unit 52 is given a characteristic that the area corresponding to position D on the imaging surface 44 is brightened, and the area corresponding to position F is gradually darkened as it moves away from position D. As a result, a uniform brightness can be obtained over the entire area including positions A to C of the imaging surface 44. That is, by appropriately setting the light distribution of the LED unit 26, it is possible to make the sensitivity at each position of the imaging surface 44 uniform within the imaging surface 44. In this way, as shown in FIG. 25, shading of the captured image 50b obtained by the imaging element 23 is eliminated.

Next, the operation of the embodiment configured in this manner will be described with reference to Figs. 26 and 27. Figs. 26 and 27 are flow charts for explaining the operation of the second embodiment. Note that Fig. 26 shows an example in which a user performs an optical path switching operation, and Fig. 27 shows an example in which optical path switching is performed automatically for stereo measurement, etc.

First, we will explain the case where the user performs an optical path switching operation.

In step S11 of FIG. 26, the control unit 31 determines whether or not an optical path switching operation has occurred. For example, it is assumed that the user operates an operation button (not shown) for switching the optical path. When the control unit 31 detects the user's optical path switching operation (YES judgment in S11), it determines in step S12 whether or not the optical path through which the current return light is incident is the first optical path 41 by the first optical system 21R. If the current optical path is the first optical path 41 by the first optical system 21R (YES judgment in S12), that is, in the state of FIG. 24, the control unit 31 instructs the optical path switching drive circuit 35 to switch to the second optical path 42 by the second optical system 21L and instructs the LED drive circuit 36 to illuminate in the second lighting mode.

As a result, the optical path switching drive circuit 35 blocks the optical path of the first optical system 21R using the optical path switching shutter 24. The LED drive circuit 36 also turns off the LED unit 51 and turns on the LED unit 52 in the second illumination mode. This results in the state shown in FIG. 25, where an optical image of the subject is captured using the second optical system 21L and an image signal is output from the image sensor 23. The image processing circuit 37 performs image processing on the image signal from the image sensor 23 and provides the captured image to the display unit 4 for display. In this way, an endoscopic image is displayed on the display screen of the display unit 4. The occurrence of shading in this endoscopic image is suppressed by the LED unit 52, which is an auxiliary light source, and a high-quality image is displayed on the display screen of the display unit 4.

On the other hand, in step S12, if the control unit 31 determines that the current optical path is not the first optical path 41 by the first optical system 21R (NO determination in S12), that is, in the state shown in FIG. 25, the control unit 31 instructs the optical path switching drive circuit 35 to switch to the first optical path 41 by the first optical system 21R, and instructs the LED drive circuit 36 to illuminate in the first lighting mode.

As a result, the optical path switching drive circuit 35 blocks the optical path of the second optical system 21L using the optical path switching shutter 24. The LED drive circuit 36 also turns off the LED unit 52 and turns on the LED unit 51 in the first illumination mode. This results in the state shown in FIG. 24, where an optical image of the subject is captured using the first optical system 21R and an image signal is output from the image sensor 23. The image processing circuit 37 performs image processing on the image signal from the image sensor 23 and provides the captured image to the display unit 4 for display. In this way, an endoscopic image is displayed on the display screen of the display unit 4. The occurrence of shading in this endoscopic image is suppressed by the LED unit 51, which is an auxiliary light source, and a high-quality image is displayed on the display screen of the display unit 4.

Next, we will explain the case where automatic optical path switching is performed.

In step S15 of FIG. 27, the control unit 31 starts executing the stereo measurement mode. In step S16, the control unit 31 instructs the optical path switching drive circuit 35 to switch to the first optical path 41 by the first optical system 21R, and instructs the LED drive circuit 36 to illuminate in the first illumination mode. This results in the state shown in FIG. 24, where an optical image of the subject is formed on the image sensor 23 via the first optical path 41. The control unit 31 obtains an imaging signal from the image sensor 23 to obtain an image (first image) (step S17).

Next, in step S18, the control unit 31 instructs the optical path switching drive circuit 35 to switch to the second optical path 42 by the second optical system 21L, and instructs the LED drive circuit 36 to illuminate in the second illumination mode. This results in the state shown in FIG. 25, where an optical image of the subject is formed on the image sensor 23 via the second optical path 42. The control unit 31 obtains an imaging signal from the image sensor 23 to obtain an image (second image) (step S19).

The control unit 31 performs measurements using the acquired first and second images. The occurrence of shading in both the first and second images is suppressed by the LED units 51 and 52, which are auxiliary light sources, making it possible to obtain highly accurate measurement results.

When performing stereoscopic observation, steps S16 to S19 are repeated to obtain a stereoscopic image using the first and second images.

In this way, in this embodiment, by using multiple auxiliary light sources in addition to the main light source, the amount of light received by the imaging surface 44 can be made uniform across the surface, and shading can be suppressed.

Third Embodiment
Fig. 28 is a block diagram showing a third embodiment of the present invention. In Fig. 28, the same components as those in Fig. 22 are given the same reference numerals and the description thereof is omitted. This embodiment differs from the configuration of the tip 11 of the insertion part in Fig. 22 in that the main light source is omitted and LED units 61 and 62 are adopted instead of the LED units 51 and 52, respectively. In addition, this embodiment adopts a device main body 2A in which the light source device 33 and the light source driving circuit 34 are omitted from the device main body 2. In the first and second embodiments, examples in which a main light source and an auxiliary light source are adopted have been described, but this embodiment adopts a plurality of auxiliary light sources.

The LED units 61 and 62 each function as a main light source and an auxiliary light source. Although FIG. 28 shows an example in which two light sources are used, three or more light sources may be used. The LED units 61 and 62 have the same configuration as the LED units 51 and 52. Both LED units 61 and 62 are composed of LEDs and an illumination optical system (not shown). The illumination optical system of the LED units 61 and 62 is composed of various optical elements such as lenses and prisms, and illuminates the subject with illumination light generated by the LEDs with a predetermined light distribution.

The LED units 61 and 62 are driven by an LED drive circuit 63 in the device body 2. The LED drive circuit 63 is controlled by the control unit 31 to drive the LED units 61 and 62. This allows the LED units 61 and 62 to emit illumination light in the illumination mode specified by the LED drive circuit 63. That is, the LED units 61 and 62 are independently controlled in the light distribution of the illumination light they emit. For example, the LED drive circuit 63 lights up the ED unit 61 with a biased light distribution necessary to suppress shading caused by the optical axis of the first optical system 21R being eccentric from the imaging center of the imaging element 23. The LED drive circuit 63 also lights up the ED unit 62 with a biased light distribution necessary to suppress shading caused by the optical axis of the second optical system 21L being eccentric from the imaging center of the imaging element 23.

(Example of auxiliary light source placement)
FIG. 29 is an explanatory diagram showing three examples of arranging a plurality of auxiliary light sources such as LED units 61 and 62.

Figure 29 shows the tip surface of the optical adapter 11a. The tip surface of the optical adapter 11a faces the entrance surface of the first optical system 21R and the entrance surface of the second optical system 21L. The example in the upper part of Figure 29 shows that the exit surfaces of the illumination optical systems 65a and 65b constituting the LED units 61 and 62 face the tip surface of the optical adapter 11a. The exit surfaces of the illumination optical systems 65a and 65b are respectively arranged near the entrance surface of the first optical system 21R and near the circumference of the optical adapter 11a near the entrance surface of the second optical system 21L. That is, the illumination optical systems 65a and 65b are arranged symmetrically with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

The example in the middle of Figure 29 shows that the exit surfaces of the illumination optical systems 66a and 66b face the screen. The exit surfaces of the illumination optical systems 66a and 66b are both provided at midpoints between the optical axes of the optical systems 21R and 21L in the parallax direction. The illumination optical systems 66a and 66b have a rectangular shape, and are configured to be line-symmetrical with respect to a line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L, and to be line-symmetrical with respect to a line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

The example in the lower part of Figure 19 shows that the exit surfaces of the illumination optical systems 67a and 67b constituting the LED units 61 and 62 face the tip surface of the optical adapter 11a. The exit surfaces of the illumination optical systems 67a and 67b are arranged side by side in the parallax direction near the entrance surface of the second optical system 21L and the entrance surface of the first optical system 21R, respectively, on the central side in the parallax direction of the tip surface of the optical adapter 11a. That is, the illumination optical systems 27a and 27b are arranged symmetrically with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

In the embodiment, for example, the ED unit 61 enables illumination that combines illumination by the illumination optical system 25 constituting the main light source with illumination by the LED unit 51, and the ED unit 62 enables illumination that combines illumination by the illumination optical system 25 constituting the main light source with illumination by the LED unit 52.

Therefore, the operation of the third embodiment differs from that of the second embodiment only in that illumination is provided by the ED unit 61 instead of the illumination provided by the illumination optical system 25 and the LED unit 51 in the second embodiment, and illumination is provided by the ED unit 62 instead of the illumination provided by the illumination optical system 25 and the LED unit 52 in the second embodiment.

In this way, the same effects as those of the above embodiments can be obtained in this embodiment as well.

(Modification)
Fig. 30 is a block diagram showing a modified example. In Fig. 30, the same components as those in Fig. 28 are given the same reference numerals and the description thereof will be omitted. This embodiment differs from the configuration of the tip of the insertion part in Fig. 28 in that the main light source is omitted and an LED unit 71 is adopted instead of the LED units 61 and 62. In the second embodiment, an example in which the main light source is omitted and two auxiliary light sources are adopted is described, but this embodiment adopts one auxiliary light source.

The LED unit 71 functions as a main light source and an auxiliary light source. The LED unit 71 has the same configuration as the LED unit 26. The LED unit 71 is composed of an LED and an illumination optical system (not shown). The illumination optical system of the LED unit 71 is composed of various optical elements such as lenses and prisms, and illuminates the subject with the illumination light generated by the LED with a specified light distribution.

The LED unit 71 is driven by an LED drive circuit 72 in the device body 2. The LED drive circuit 72 is controlled by the control unit 31 to drive the LED unit 71. This allows the LED unit 71 to emit illumination light in an illumination mode specified by the LED drive circuit 72. That is, the LED unit 71 controls the light distribution of the emitted illumination light according to the illumination mode. For example, the LED drive circuit 72 lights up the ED unit 71 with a biased light distribution necessary to suppress shading caused by the optical axis of the first optical system 21R being eccentric from the center of the imaging surface 44 of the imaging element 23. The LED drive circuit 72 also lights up the ED unit 71 with a biased light distribution necessary to suppress shading caused by the optical axis of the second optical system 21L being eccentric from the center of the imaging surface 44 of the imaging element 23.

That is, in this embodiment, the ED unit 71 enables illumination by the LED unit 61 and illumination by the LED unit 62. Therefore, the operation of the third embodiment differs from the second embodiment only in that the illumination mode of the LED unit 71 is switched depending on the optical path used.

In this way, the same effects as those of the above embodiments can be obtained in this embodiment as well.

(Example of a specific configuration for obtaining a biased light distribution)
In the above embodiments, for convenience of explanation, a light source that generates a biased light distribution and is provided to avoid the above-mentioned shading problem is referred to as an auxiliary light source, and a general light source that does not consider the shading problem is referred to as a main light source, but illumination having such a biased light distribution can also be obtained by a single light source. Therefore, in the following explanation, the terms main light source and auxiliary light source will not be used, and the light source that generates a biased light distribution will also be described simply as a light source.

Figures 31 to 49 are explanatory diagrams showing examples of the configuration of a light source for obtaining a biased light distribution in each of the above embodiments. In addition, in Figures 31, 32, 34, 36, 38, 40, 42, 44, 46, 47, and 48, the direction parallel to the optical axis of the first optical system 21R and the second optical system 21L is taken as the horizontal direction of the paper. In addition, the parallax direction between the first optical system 21R and the second optical system 21L is taken as the vertical direction of the paper, and the first optical system 21R is arranged in the upper direction of the paper and the second optical system 21L is arranged in the lower direction of the paper. In the following, the upper side of the paper of the illumination range illuminated by the light source shown in each of these figures is described as the R (right) side, and the lower side of the paper is described as the L (left) side. In addition, the light distribution LD in each figure indicates the intensity in a direction parallel to the optical axis of the first optical system 21R and the second optical system 21L.

(Example 1)
The example of Fig. 31 shows an example in which two biased light distributions are obtained by using two light sources 81a and 81b. For example, as shown in the three examples of Fig. 29, this is an example in which two auxiliary light sources are adopted.

In FIG. 31, the illumination range of light source 81a is indicated by a solid arrow, and the illumination range of light source 81b is indicated by a dashed arrow. In the example of FIG. 31, the optical axes of light sources 81a and 81b are arranged at an angle from the optical axes of first optical system 21R and second optical system 21L. As a result, the light distribution LD (solid line) of light source 81a has a relatively high intensity on the R side of the illumination range, and the intensity decreases toward the L side of the illumination range. Note that the light distribution by light source 81b (not shown) has a line-symmetrical distribution with respect to the light distribution LD by light source 81a, which is perpendicular to the parallax direction. Note that light sources 81a and 81b can be configured relatively easily.

(Example 2)
The example of Fig. 32 shows an example in which a biased light distribution is obtained by using four light sources 82a, 82b, 82c, and 82d. Fig. 33 is an explanatory diagram showing an example of the arrangement of the LED units corresponding to Fig. 32.

Figure 33 shows the tip surface of the optical adapter 11a. The tip surface of the optical adapter 11a faces the entrance surface of the first optical system 21R and the entrance surface of the second optical system 21L. The exit surfaces of the light sources 82a to 82d are arranged adjacent to each other and lined up in the parallax direction at the circumferential end of the optical adapter 11a near the entrance surface of the first optical system 21R and near the entrance surface of the second optical system 21L. The exit surfaces of the light sources 82a and 82b and the exit surfaces of the light sources 82d and 82c are arranged symmetrically with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

In Figure 32, the thickness of the arrow segments indicates the intensity of the illumination light emitted from light sources 82a to 82d. For example, light sources 82a and 82d emit light with similar intensity, while light sources 82b and 82c emit light with a stronger intensity than light sources 82a and 82d. Furthermore, light sources 82b and 82c can change the intensity of each other, and the example in Figure 32 shows that the intensity of the light emitted by light source 82b is stronger than the intensity of the light emitted by light source 82c.

In this case, the light distribution LD of the light sources 82a to 82d has a relatively high intensity on the R side of the illumination range, and the intensity decreases toward the L side of the illumination range. If the intensity of the light emitted by the light source 82c is made stronger than the intensity of the light emitted by the light source 82b, the light distribution (not shown) by the light sources 82a to 82d will be symmetrical with respect to the illustrated light distribution LD about a straight line perpendicular to the parallax direction.

(Example 3)
The example of Fig. 34 shows an example in which a biased light distribution is obtained by using light sources 83a to 83c such as LED units arranged at the tip of the optical adapter 11a, and a light source 83c using a light source device 84a and a light guide 84b. Fig. 35 is an explanatory diagram showing an example of the arrangement of the light sources 83a to 83c corresponding to Fig. 24.

Figure 35 shows the tip surface of the optical adapter 11a. The tip surface of the optical adapter 11a faces the entrance surface of the first optical system 21R and the entrance surface of the second optical system 21L. The exit surfaces of the light sources 83a and 83d are arranged at the circumferential end of the optical adapter 11a near the entrance surface of the first optical system 21R and the entrance surface of the second optical system 21L, respectively, spaced apart from each other in the parallax direction. The light source 83c is arranged at the circumferential end of the optical adapter 11a near the entrance surface of the first optical system 21R and the entrance surface of the second optical system 21L, and is located at a position midway between the light sources 83a and 83b in the parallax direction. The exit surfaces of the light sources 83a to 83c are arranged symmetrically with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

In FIG. 34, the illumination ranges of light sources 83a and 83c are indicated by solid arrows, and the illumination range of light source 83b is indicated by dashed arrows. In FIG. 34, light source 83c is always illuminating, whereas light sources 83a and 83b are turned on or off depending on the illumination mode. The light distribution LD in FIG. 34 shows an example in which light sources 83a and 83c are turned on and light source 83b is turned off, as indicated by the solid arrows. In this case, the light distribution LD by light sources 83a and 83b has a relatively high intensity on the R side of the illumination range, and the intensity decreases toward the L side of the illumination range. Note that by turning on light sources 83c and 83b and turning off light source 83a, a distribution that is linearly symmetrical with respect to a straight line perpendicular to the parallax direction can be obtained for the light distribution LD shown in the figure.

The example in Figure 34 can also be achieved using light sources arranged as shown in the upper and middle rows of Figure 23.

A laser diode light source may be used as the light source device 84. A rod lens may be added to the light guide 84b.

(Example 4)
The example of Fig. 36 shows an example in which two biased light distributions are obtained by using two light sources 85a and 85b and a cylindrical lens 86. Fig. 37 is a perspective view showing the cylindrical lens 86 in Fig. 36.

As shown in FIG. 37, the cylindrical lens 86 is a cube with one surface formed in a cylindrical shape. As shown in FIG. 36, the light sources 85a and 85b are arranged to face the cylindrical surface of the cylindrical lens 86 and are shifted away from each other in the parallax direction from the optical axis of the cylindrical lens 86.

In FIG. 36, the illumination range of light source 85a is indicated by a solid arrow, and the illumination range of light source 85b is indicated by a dashed arrow. Due to the action of cylindrical lens 86, the light distribution LD (solid line) of light source 85a is a distribution in which the intensity is relatively high on the R side of the illumination range and decreases toward the L side of the illumination range. Note that the light distribution by light source 85b (not shown) has a linear symmetry with respect to the light distribution LD by light source 85a, which is perpendicular to the parallax direction.

In addition, since shading occurs to the left and right, which are the eccentric directions of the observation system, it is efficient to use a lens that has power in only one direction. Also, depending on the design, any desired light distribution can be achieved.

(Example 5)
The example of Fig. 38 shows an example in which two biased light distributions are obtained by using two light sources 85a and 85b and a Fresnel lens 87. Fig. 39 is a perspective view showing the Fresnel lens 87 in Fig. 38.

As shown in Figure 39, the Fresnel lens 87 has a cube shape with one face divided into multiple concentric regions, allowing for a thin design. As shown in Figure 38, the light sources 85a and 85b are arranged to face the cylindrical surface of the Fresnel lens 87 and are offset from each other in the parallax direction from the optical axis of the Fresnel lens 87.

In FIG. 38, the illumination range of light source 85a is indicated by a solid arrow, and the illumination range of light source 85b is indicated by a dashed arrow. Due to the action of Fresnel lens 87, the light distribution LD (solid line) of light source 85a is a distribution in which the intensity is relatively high on the R side of the illumination range and decreases toward the L side of the illumination range. Note that the light distribution by light source 85b (not shown) has a linear symmetry with respect to the light distribution LD by light source 85a, which is perpendicular to the parallax direction.

(Example 6)
The example of Fig. 40 shows an example in which two biased light distributions are obtained by using two light sources 85a, 85b and wedge prisms 88a, 88b. Fig. 41 is a perspective view showing the wedge prisms 88a, 88b in Fig. 40.

As shown in Figure 41, the wedge prisms 88a and 88b have a wedge shape in which one side of a cube is inclined with respect to the opposite surface, making one side narrower than the other. As shown in Figure 40, the wedge prisms 88a and 88b are arranged with their wide sides facing each other and the non-inclined surface in the line of sight, and light sources 85a and 85b are arranged facing the inclined surfaces of the wedge prisms 88a and 88b, respectively.

In FIG. 40, the illumination range of light source 85a is indicated by a solid arrow, and the illumination range of light source 85b is indicated by a dashed arrow. Due to the action of wedge prisms 88a and 88b, the light distribution LD (solid line) of light source 85a is a distribution in which the intensity is relatively high on the R side of the illumination range and decreases toward the L side of the illumination range. Note that the light distribution by light source 85b (not shown) has a linear symmetry with respect to the light distribution LD by light source 85a, which is perpendicular to the parallax direction.

The wedge-shaped prisms 88a and 88b have the advantage that they are easy to process and can be easily divided and arranged.

(Example 7)
The example of Fig. 42 shows an example in which two biased light distributions are obtained by using two light sources 85a, 85b and a concave lens 89 having negative power. Also, Fig. 43 shows an example of a Fresnel lens 91 or prisms 90a, 90b that can be used instead of the concave lens 89. The prisms 90a, 90b are disposed opposite the light sources 85a, 85b, respectively, in the same manner as in Fig. 40.

As shown in Figure 42, the concave lens 89 has one surface of a cube cut into a cylindrical shape. As shown in Figure 42, the light sources 85a and 85b are arranged to face the curved surface of the concave lens 89, with the optical axes of the light sources 85a and 85b and the optical axis of the concave lens 89 being decentered in the parallax direction.

In FIG. 42, the illumination range of light source 85a is indicated by a solid arrow, and the illumination range of light source 85b is indicated by a dashed arrow. Due to the action of concave lens 89, the light distribution LD (solid line) of light source 85a is a distribution in which the intensity is relatively high on the R side of the illumination range and decreases toward the L side of the illumination range. Note that the light distribution by light source 85b (not shown) has a linear symmetry with respect to the light distribution LD by light source 85a, which is perpendicular to the parallax direction.

In addition, instead of the concave lens 89, a Fresnel lens 91 or prisms 90a, 90b having similar characteristics may be used.

(Example 8)
The example of Fig. 44 shows an example in which two biased light distributions are obtained using two light sources 85a, 85b and a liquid crystal lens 92. Fig. 45 is an explanatory diagram showing the action of the liquid crystal lens 92. The left side of Fig. 45 shows a state in which no voltage is applied to the liquid crystal lens 92 (voltage V: OFF), and the right side shows a state in which a voltage is applied to the liquid crystal lens 92 (voltage V: ON). In the voltage V: OFF state, light travels linearly through the liquid crystal lens 92, whereas in the voltage V: ON state, the light travels in a deflected manner due to the light deflection effect of the liquid crystal lens 92.

As shown in FIG. 44, the light sources 85a and 85b are arranged opposite the liquid crystal lens 92, and the optical axes of the light sources 85a and 85b are arranged eccentrically from the center of the liquid crystal lens 92.

In FIG. 44, the illumination range of light source 85a is indicated by a solid arrow, and the illumination range of light source 85b is indicated by a dashed arrow. Due to the action of liquid crystal lens 92, the light distribution LD (solid line) of light source 85a is a distribution in which the intensity is relatively high on the R side of the illumination range and decreases toward the L side of the illumination range. Note that the light distribution by light source 85b (not shown) has a linear symmetry with respect to the light distribution LD by light source 85a, which is perpendicular to the parallax direction.

In this way, in this example, the light distribution can be electrically controlled.

(Example 9)
The example of Fig. 46 shows an example in which a biased light distribution is obtained by using a light source 85a and a gradation ND filter 94. Although the light source 85b in the above figures is omitted in Fig. 46, it is clear that a biased light distribution can be obtained by using the light source 85b and the gradation ND filter 94. The gradation ND filter 94 is an element having a transmittance gradient, and is disposed opposite the light source 85a so that the transmittance changes in the parallax direction.

The solid arrow in Figure 46 indicates the illumination range of light source 85a. Due to the action of gradation ND filter 94, the light distribution LD (solid line) of light source 85a is relatively high in intensity on the R side of the illumination range, and the intensity decreases toward the L side of the illumination range. As described above, by using light source 85b and gradation ND filter 94, it is also possible to make the light distribution by light source 85b linearly symmetrical with respect to the light distribution LD by light source 85a, with respect to a straight line perpendicular to the parallax direction.

In addition, by using the gradation ND filter 94, any desired light distribution pattern can be obtained relatively easily compared to using a lens.

(Example 10)
The example of Fig. 47 shows an example in which a biased light distribution is obtained by using a light source 85a and a diffusion element 95. Although the light source 85b in the above figures is omitted in Fig. 47, it is clear that a biased light distribution can be obtained by using the light source 85b and the diffusion element 95. The diffusion element 95 is an element with a different diffusion degree, and is disposed opposite the light source 85a so that the diffusion degree changes in the parallax direction.

As shown in FIG. 47, the illumination range of light source 85a is indicated by a solid arrow. Due to the action of diffusion element 95, the light distribution LD (solid line) of light source 85a is relatively high in intensity on the R side of the illumination range, and the intensity decreases toward the L side of the illumination range. As described above, by using light source 85b and diffusion element 95, it is also possible to make the light distribution by light source 85b symmetrical with respect to the light distribution LD by light source 85a with respect to a line perpendicular to the parallax direction.

In addition, in the above examples 1 to 10, the optical adapter 11a is not limited to an LED unit that serves as a light source, and light from the light source may be transmitted through a light guide and emitted through a lens.

Figure 48 is an explanatory diagram showing an example of this case. Also, Figure 49 is an explanatory diagram showing an example of the arrangement of the light source emission surface of the optical adapter 11a corresponding to Figure 48.

The light source 96a is a light source for the first optical system 21R, and the light source 96b is a light source for the second optical system 21L. The light emitted from the light sources 96a and 96b is guided to the optical adapter 11a by the light guides 97a and 97b, respectively. The light guides 97a and 97b have end faces facing the lenses 98a and 98b, respectively, and are arranged at positions eccentric from the centers of the lenses 98a and 98b in the direction away from each other in the parallax direction. This allows the light distribution of the illumination light by the light source 96a and the light distribution of the illumination light by the light source 96b to be biased light distributions that are linearly symmetrical with respect to a straight line perpendicular to the parallax direction.

Figure 49 shows the tip surface of the optical adapter 11a. The tip surface of the optical adapter 11a faces the entrance surface of the first optical system 21R and the entrance surface of the second optical system 21L. In the upper part of Figure 49, the exit surfaces of the lenses 98a and 98b have shapes that are line-symmetrical with respect to a straight line that passes through the center of the tip surface of the optical adapter 11a and is perpendicular to the parallax direction of the optical systems 21R and 21L.

The example in the lower part of Figure 49 shows an example in which, instead of lens 98, lenses 99a and 99b are arranged in the above-mentioned divided positions facing the respective emission surfaces of light guides 97a and 97b. A channel opening 99 such as a forceps port is provided in the optical adapter 11a, and the emission surfaces of the lenses 99a and 99b are arranged in positions that avoid this channel opening 99.

(Shading correction by image processing)
In the above-described embodiments, an example has been described in which shading caused by decentering between the optical axes of the first optical system 21R and the second optical system 21L and the center of the imaging surface 44 of the imaging element 23 is corrected by using a light source having a biased light distribution. Furthermore, in consideration of the fact that shading is not sufficient only by controlling the light distribution of the light source, it is also possible to perform shading correction by image processing.

Figure 50 is a flowchart showing the shading correction that can be employed in each of the above embodiments, and Figure 51 is a graph for explaining shading correction. Figure 51 shows the change in luminance value at each position on the imaging surface 44 in the example of Figure 4, with the luminance value on the horizontal axis and the position on the imaging surface 44 on the vertical axis. Now, for the sake of convenience of explanation, it will be assumed that even when illumination is performed with a biased light distribution by the LED unit 26 as shown in Figure 8, shading cannot be eliminated and the change in luminance value shown in Figure 51 occurs.

In step S21 of FIG. 50, the control unit 31 determines whether the first optical path 41 or the second optical path 42 is the incident optical path being used. The control unit 31 controls the path switching drive circuit 35 to switch the optical path using the optical path switching shutter 24, and is aware of the incident optical path. In step S21, the control unit 31 sets a correction target value for the luminance value (pixel value) at each pixel position on the imaging surface 44 of the image sensor 23.

The straight line with constant luminance value in Figure 51 indicates this correction target value. Shading correction is performed by setting the signal level at each pixel position on the imaging surface 44 to a constant correction target value.

That is, the control unit 31 controls the image processing circuit 37 to calculate the luminance value at each pixel position (step S23). The control unit 31 calculates, for each pixel, a gain value required to make the calculated luminance value the correction target value. The control unit 31 may store this gain value in the memory 39. The image processing circuit 37 performs shading correction by applying the gain value calculated by the control unit 31 to each pixel in image processing (step S24).

In this way, by adopting the flow in Figure 50, the occurrence of shading can be reliably prevented by controlling the light source's light distribution and correcting shading through image processing.

The present invention is not limited to the above-described embodiments, and in the implementation stage, the components can be modified to the extent that does not deviate from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiments. For example, some of the components shown in the embodiments may be deleted. Furthermore, components from different embodiments may be appropriately combined.

2...device main body, 11...tip portion, 20...stereo optical system, 22...optical path switching shutter, 23...image pickup element, 24..., 25...illumination optical system, 26...LED unit, 31...control unit, 32...image pickup element driving circuit, 33...light source device, 34...light source driving circuit, 35..., optical path switching driving circuit, 36...LED driving circuit, 37...image processing circuit.

Claims (8)

an observation unit having two incident light paths by two optical systems whose optical axes are decentered with respect to the imaging center of a sensor, the observation unit including a mechanism capable of switching between the two incident light paths;
an illumination unit capable of illuminating in illumination modes corresponding to the two incident light paths;
a control unit that controls switching of the illumination mode in response to switching of the two incident light paths ,
an illumination unit that performs illumination in an illumination mode in which a light distribution is set to correct shading occurring in the output of the sensor in accordance with a difference between an incident angle of incident light that passes through one of the two incident light paths and enters the sensor and an incident angle characteristic of the sensor, and an illumination mode in which a light distribution is set to correct shading occurring in the output of the sensor in accordance with a difference between an incident angle of incident light that passes through the other of the two incident light paths and enters the sensor and an incident angle characteristic of the sensor. The illumination unit includes a main light source and an auxiliary light source.
The endoscope apparatus according to claim 1 , wherein the control unit switches the illumination mode by switching a light distribution by the auxiliary light source. the illumination unit has a main light source and one auxiliary light source capable of illuminating with different light distributions or a plurality of auxiliary light sources capable of illuminating with mutually different light distributions ;
The endoscope apparatus according to claim 2 , wherein the control unit switches the illumination mode by switching a light distribution by the one auxiliary light source or the plurality of auxiliary light sources. The illumination unit has a main light source and a plurality of auxiliary light sources each capable of providing illumination with a different light distribution,
The endoscope apparatus according to claim 2 , wherein the control unit switches the illumination mode by switching an auxiliary light source to be used for illuminating the subject from among the plurality of auxiliary light sources. 5. An endoscope device according to claim 1, wherein the incident angle characteristic is perpendicular to the imaging surface of the sensor near the center thereof, and the inclination angle with respect to the imaging surface becomes smaller toward the end of the imaging surface of the sensor. An illumination method for an endoscope apparatus including an observation unit having two incident optical paths by two optical systems whose optical axes are decentered with respect to an imaging center of a sensor and a mechanism capable of switching between the two incident optical paths, an illumination unit capable of illumination in illumination modes corresponding to each of the two incident optical paths, and a control unit, comprising:
the illumination unit performs illumination in an illumination mode in which a light distribution is set to correct shading occurring in an output of the sensor in accordance with a difference between an incident angle of incident light that passes through one of the two incident light paths and enters the sensor and an incident angle characteristic of the sensor, and an illumination mode in which a light distribution is set to correct shading occurring in an output of the sensor in accordance with a difference between an incident angle of incident light that passes through the other of the two incident light paths and enters the sensor and an incident angle characteristic of the sensor,
An illumination method, wherein the control unit controls the observation unit to enable the passage of light in one of the two incident light paths, and controls the illumination unit to illuminate an object in an illumination mode corresponding to the incident light path through which the light passes. 1. An illumination control program for controlling illumination of an endoscope apparatus comprising: an observation unit having two incident optical paths by two optical systems whose optical axes are decentered with respect to an imaging center of a sensor, the observation unit having a mechanism capable of switching between the two incident optical paths; and an illumination unit capable of illumination in illumination modes corresponding to the two incident optical paths, the program comprising:
On the computer,
illumination is performed in an illumination mode in which a light distribution is set to correct shading occurring in an output of the sensor in accordance with a difference between an incident angle of incident light passing through one of the two incident light paths and entering the sensor and an incident angle characteristic of the sensor, and an illumination mode in which a light distribution is set to correct shading occurring in an output of the sensor in accordance with a difference between an incident angle of incident light passing through the other of the two incident light paths and entering the sensor and an incident angle characteristic of the sensor,
An illumination control program for executing a procedure of controlling the observation unit to enable the passage of light in one of the two incident light paths, and controlling the illumination unit to illuminate an object in an illumination mode corresponding to the incident light path through which the light passes. an observation unit having two incident light paths by two optical systems whose optical axes are decentered with respect to the imaging center of a sensor, the observation unit including a mechanism capable of switching between the two incident light paths;
an illumination unit capable of illumination in illumination modes corresponding to the two incident light paths,
an illumination unit that performs illumination in an illumination mode in which a light distribution is set to correct shading occurring in the output of the sensor in accordance with a difference between an incident angle of incident light that passes through one of the two incident light paths and enters the sensor and an incident angle characteristic of the sensor, and an illumination mode in which a light distribution is set to correct shading occurring in the output of the sensor in accordance with a difference between an incident angle of incident light that passes through the other of the two incident light paths and enters the sensor and an incident angle characteristic of the sensor.

Images