JPH071343B2 - Exposure control device for imaging system for endoscope - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exposure control device for an endoscope imaging system that automatically controls exposure time.

[Conventional technology]

An endoscope is generally adapted not only to observe the inside of a body cavity but also to take a photograph. The exposure time at the time of taking a picture is set in the illumination optical path in the light source device when the output of the light receiving element that receives the reflected light from the subject illuminated by the light source is integrated and the integrated voltage reaches the set voltage. It is controlled by closing a mechanical shutter.

However, since a mechanical shutter requires a time from receiving a signal for closing to actually closing it, overexposure occurs due to the delay. The exposure time ΔT for this overexposure is constant regardless of the length of the total exposure time T at that time. Therefore, when the total exposure time T is short, that is, when the subject is bright such as in close-up photography, the influence of ΔT is large and the amount of overexposure is significant.

Therefore, conventionally, the rise of the output of the integrated state value obtained by integrating the output of the light receiving element is differentially detected, and when the differential output value is equal to or greater than the reference value, the brightness of the illumination light supplied from the light source device to the endoscope is adjusted. The total exposure time T was lengthened by reducing the observation state level to reduce the influence of ΔT (Japanese Patent Publication No. 61-36928).

[Problems to be Solved by the Invention]

In the imaging system of the endoscope, when the exposure time is short, the overexposure occurs as described above, but since the subject is a living body that constantly moves, the problem of blurring occurs when the exposure time becomes slightly longer. Therefore, the ideal exposure time with both overexposure and blurring is in a very narrow range.

However, as described above, in the exposure control device of the conventional endoscope imaging system, when the exposure time is significantly shortened, the brightness of the illumination light supplied from the light source device to the endoscope is simply observed. The exposure time was not specifically controlled to fall within a certain range because it was only reduced to the level and the exposure time was extended. Therefore, even if the exposure time sometimes falls within the ideal range, it is a coincidence, and overexposure or blurring often occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exposure control device for an endoscope imaging system, which eliminates such conventional drawbacks and can perform ideal exposure time control with less overexposure and less blur. .

[Means for Solving the Problems]

In order to achieve the above object, the exposure control device of the endoscope imaging system of the present invention, as shown in FIG. 1, is a light source that supplies illumination light for illuminating a subject to the endoscope,
A photoelectric conversion unit that converts the brightness of light that is exposed on the shooting surface of the shooting device after being reflected by the subject into an electric signal,
An integrating unit that integrates the output from the photoelectric converting unit and outputs the integrated state value, and an estimated exposure time calculating unit that detects the time change rate of the output from the integrating unit and calculates the expected exposure time from the detected value. Means and the output from the expected exposure time calculation means, and controls the brightness of the illumination light supplied from the light source to the endoscope so that the exposure time of the photographing surface falls within a predetermined range. And a control means for controlling the exposure time.

[Action]

The brightness of the light exposed on the photographing surface is converted into an electric signal by the photoelectric conversion means, the output thereof is integrated by the integration means, and the integrated state value is output. Then, the expected exposure time is calculated by the expected exposure time calculation means from the time change rate of the integrated state value, and the exposure time falls within a predetermined ideal range based on the output from the expected exposure time calculation means. As described above, the brightness of the illumination light supplied from the light source to the endoscope is controlled by the control means.

〔Example〕

 An embodiment will be described with reference to the drawings.

FIG. 2 shows an imaging system of an endoscope. Reference numeral 1 denotes an endoscope, and a camera (imaging device) 2 is detachably attached to an eyepiece portion 14 of the endoscope via an adapter 3.

Reference numeral 4 denotes a light source device, to which the connector 11 of the endoscope 1 is detachably connected. Then, the illumination light emitted from the light source 40 is condensed by the condenser lens 41 and supplied to the light guide fiber 12 of the endoscope.

In the illumination light path between the light source 40 and the light guide fiber 12, an openable / closable shutter (light source shutter) 42 for fully opening or closing the illumination light path, and a diaphragm 43 for varying the passing area of the illumination light are provided. Has been.

Then, the illumination light is transmitted by the light guide fiber 12 and is irradiated onto the subject 100 from the tip 13 of the insertion portion of the endoscope. The light reflected by the subject 100 is transmitted by an image guide fiber (not shown) to expose the film surface (shooting surface) 25 of the camera 2. The shutter (camera shutter) 22 in the camera 2 opens for a fixed time (for example, 0.25 seconds) only when the synchro switch 21 is turned on.

Reference numeral 15 denotes a light receiving element provided in the eyepiece 14 for converting the brightness of light exposed on the film surface 25 (hereinafter referred to as “light flux”) into an electric signal, and the output voltage of the light receiving element 15 Circuit) 16 and the integrated state value is integrated by the photometric circuit.
It is output from 16. The photometric circuit 16 may be provided in the light source device 4, but may be provided in the endoscope 1.

45 is an exposure index setting switch provided on the operation panel 46 on the surface of the light source device 4. Reference numeral 50 is a control unit that incorporates a microcomputer.

FIG. 3 is a block diagram showing an electrical configuration of the embodiment. In the control unit 50, a system bus 52 connected to a central processing unit (CPU) 51 is provided with a ROM 53, a RAM 54 and a programmable program for counting elapsed time. An interval timer (PIT) 55 is connected. The output signal from the synchro switch 21 is interrupted and input to the CPU 51.

Further, the system bus 52 is connected to first to third input / output ports 56, 57, 58, and an exposure index setting switch 45 is connected to an input end of the first input / output port 56.
The output from the light receiving element 15 is integrated by the photometric circuit (integrating circuit) 16, and the integrated state value (integrated output voltage V) is input to the input end of the second input / output port 57 via the analog-digital converter 17. Is connected to. The output terminals of the third input / output port 58 are connected to drive circuits 40a, 42a, 43a for controlling various operations such as the light emission brightness of the light source 40, the opening / closing of the light source shutter 42, and the opening of the diaphragm 43.

Further, an initial shutter closing signal generating means for generating a signal for keeping the light source shutter 42 closed for a predetermined short time in synchronization with the turning on of the synchro switch 21, and the synchro switch
There is provided means for generating an all-operation period signal that limits the all-operation period of the device in conjunction with turning on of 21, and the output signals thereof are input to the control unit 50, but they are not shown. Omitted.

FIG. 4 is a time chart showing the operation of the above embodiment.

When the synchro switch 21 of the camera 2 is turned on, the shutter (camera shutter) 22 of the camera 2 opens slightly later,
It closes after a fixed time (for example, 0.25 seconds) has elapsed. Further, at the same time when the synchro switch 21 is turned on, the light source shutter 42 in the light source device 4 is once closed by the initial shutter closing signal, and the signal for the entire operation period is turned on.

Then, when the initial shutter closing signal falls after a lapse of a predetermined short time, at the same time, the light source shutter 42 starts to open.

At that time, the brightness (luminous flux) Φ of the illumination light supplied to the endoscope, which is determined by the emission brightness of the light source 40 and the aperture of the diaphragm 43.
Maintains the illumination luminous flux Φ ₀ in the observation state, and the integrated output voltage output from the photometry circuit 16 starts to rise as the light source shutter 42 opens.

Then, the CPU 51 starts the opening of the light source shutter 42 (t ₀
= 0), the time rate of change of the integrator output voltage V at the short time _{dt = t 1 -t 0 = t} 1 ( differential value) dV / dt = c · V 1 / t 1 is detected, expected from the detected value The exposure time T'is calculated. Where V ₁ is the integrated output voltage at t ₁ . c is a correction coefficient larger than 1.

The expected exposure time T'is calculated using the set voltage Vr as a reference, and the set voltage Vr is automatically set according to the exposure index input from the exposure index setting switch 45. Expected exposure time T '
Is specifically calculated as T ′ = (Vr−V ₁ ) dt / dV + t ₁ .

Therefore, in this embodiment, for example, three reference exposure times T ₁ , T ₂ , and T ₃ are set as the exposure time. Specifically, T ₁ = 0.01 seconds T ₂ = 0.015 seconds T ₃ = 0.03 seconds.

Then, by controlling one or both of the light source 40 and the diaphragm 43, the illumination luminous flux Φ is controlled as follows.

T when '<time _{T 1 Φ = Φ 0/3} T 1 ≦ T'< When _{Φ = Φ 0 T 2 ≦ T'T} 3 when _{T 2 Φ = 3Φ 0/2} T 3 ≦ T 'Φ = Maximum By controlling in this way, the exposure time can be set to the range of T _{1 to} T ₃ in most cases, that is, the ideal range of 0.01 to 0.03 seconds.

FIG. 5 shows the above case, that is, the expected exposure time T ′ is too short, so that the illumination luminous flux Φ is reduced to one-third of the observation time so that the exposure time T falls within the ideal range. Shows. The dotted line shows the case where the control of the present invention is not performed, and the solid line shows the case where the control of the present invention is performed.

Further, FIG. 6 shows that in the above case, that is, since the expected exposure time T ′ is within the ideal range but is a relatively long time, the illumination luminous flux Φ is increased by 1.5 times as much as that at the time of observation, and the exposure time T is ideal. The case where control is performed within a relatively short time within the range is shown. The dotted line shows the case where the control of the present invention is not performed, and the solid line shows the case where the control of the present invention is performed.

In order to make the above control more accurate, after the light source shutter 42 is fully opened, the integral output is differentially detected again to calculate the expected exposure time, and the illumination light flux Φ supplied to the endoscope is calculated. Control again. This is because, at the time of control immediately after the starting point t ₀ described above, since the light source shutter 42 is opening, the rise of the integrated output voltage V is not linear with time, and dV / dt is not a definite value. Or, because the value of dV is small, a calculation error is likely to occur.

Therefore, with t ₂ after elapse of time ΔT or more required for the light source shutter 42 to fully open from t ₀ as the next starting point, the time of the integrated output voltage V during a predetermined short time (t ₃ −t ₂ ). Detect the rate of change. Then, the remaining exposure time Tx at time t ₃ is calculated as Tx = (Vr−V ₃ ) dt−dV. V ₃ is the integrated output voltage at t ₃ .

Then, assuming that the time from t ₃ to T ₃ is T ₄ , when Tx> T ₄ , that is, when the total exposure time exceeds T ₃ (0.03 seconds), the illumination luminous flux Φ is maximized.

When the exposure time control is performed in this way and the signal during the entire operation period is turned off, the system returns to the state before photographing, that is, the observation state.

7 to 9 are control units for performing the above control.
It is a processing flow chart of 50, and FIGS. 7 and 8 show the case where the control is performed only once. s indicates a step.

This process starts when the initial shutter closing signal falls, the light source shutter 42 is opened at s1, and at the same time as the opening, the integrated output voltage V is input from the photometric circuit 16 at s2. Then in s3, Tara smaller than V is set voltage Vr, at s4, it determines whether it has reached a predetermined elapsed time t ₁ to time t elapsed after starting to open source shutter 42 detects the time rate of change.

When t has not reached t ₁ , the process returns to s 2 and a new integrated output voltage V is input. When V becomes equal to or higher than the set voltage Vr in s3, the process proceeds to s12, and in s14, the light source shutter 42 is closed and the process ends. When the elapsed time t reaches t ₁ at s4, dV / dt = C · V ₁ / t ₁ is calculated at s5, and then T ′ = (Vr−V ₁ ) dt / dV + t ₁ is calculated.

Then, in s6 to s8, T ′ is compared with T ₁ , T ₂ and T _3, and when T ′ <T _{1 in} s6, the illumination luminous flux Φ in s9 is 1 / of the illumination luminous flux Φ ₀ during observation. When s7 is T ′ <T ₂ , Φ is maintained at Φ ₀ as it is, and when s8 is T ′ <T ₃ , Φ3 is maintained.
And Φ _0/2, T '<not equal T ₃ (i.e. T' when ≧ T ₃₎ is to maximize the illumination light flux [Phi.

In this way, the illumination luminous flux Φ is set to an appropriate value, and at s12,
When the integrated output voltage V is input, it is determined in s13 whether V has reached the set voltage Vr. If it has not reached, the process returns to s12 and the same operation is repeated, and when the integrated output voltage V reaches the set voltage Vr. , S14, the light source shutter 42 is closed and the process ends.

FIG. 9 is a processing flow in the case of performing the second control after the light source shutter 42 is fully opened, which is performed following the processing flow of FIG. 7.

Here, after the first control is completed, the integrated output voltage V is input from the photometric circuit 16 in s21. And in s22,
If V is smaller than the set voltage Vr, the elapsed time t is reached in s23.
Determines whether has reached t ₂ .

Then, when t has not reached t ₂ , the process returns to s 21 and the new integrated output voltage V is input. In s22, V is the set voltage V
When it becomes r or more, the process proceeds to s32, the light source shutter 42 is closed at s34, and the process ends. In s23, When t reaches t _2, in s24, stores the integrated output signal at the time of t = t ₂ as V _2.

Next, in s25 to s28, similarly to s21 to s24, t =
The integrated output voltage at t ₃ is stored as V ₃ . And s2
In 9, dV = dt = calculates _{(V 3 -V 2) / (} t 3 -t 2), followed by calculating the _{Tx = (Vr-V 3)} dt / dV.

Then, in s30, by comparing the Tx and T _4, without changing it in the illumination light flux [Phi when not Tx> T _4, when the Tx> T ₄ to maximize the illumination light flux [Phi.

In this way, the illumination luminous flux Φ is re-controlled, the integrated output voltage V is input at s32, and it is determined at s33 whether V has reached the set voltage Vr. If not, the process returns to s32 and the same. The operation is repeated, and when the integrated output voltage V reaches the set voltage Vr, the light source shutter 42 is closed in s34, and the process ends.

In the above embodiment, the control of the illumination luminous flux Φ is controlled in four stages including the illumination luminous flux Φ ₀ at the time of observation, but this may be controlled in any number of stages. Further, the second control need not necessarily be performed, and the light amount control may be performed three or more times.

〔The invention's effect〕

According to the exposure control device of the endoscope imaging system of the present invention, the illumination light flux supplied from the light source device to the endoscope is controlled so that the exposure time for imaging falls within a predetermined range set in advance. Therefore, it is possible to always perform shooting with an ideal exposure time, and it is possible to stably perform high-quality shooting with less overexposure and less blurring.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of the present invention, FIG. 2 is a schematic configuration diagram of an embodiment, FIG. 3 is a circuit block diagram of the embodiment, and FIG. 4 is a time chart diagram showing the operation of the embodiment. 5 and 6 are diagrams showing an operation example of the embodiment, and FIGS. 7 to 9 are control processing flowcharts of the embodiment. 1 ... endoscope, 2 ... camera (imaging device), 4 ... light source device,
12 ... Light guide fiber, 15 ... Light receiving element (photoelectric conversion means), 16 ... Photometric circuit (integrating means), 25 ... Shooting surface, 40 ... Light source, 42 ... Light source shutter, 43 ... Aperture, 50 ... Control section.

Continuation of front page (56) Reference JP-A-57-150940 (JP, A) JP-A-52-10127 (JP, A) JP-A-57-53736 (JP, A) JP-A-57-64041 (JP , A) JP-A-62-161338 (JP, A)

Claims (1)

[Claims] 1. A light source that supplies illumination light for illuminating a subject to an endoscope, and the brightness of light that is reflected on the subject and is exposed on a photographing surface of a photographing device is converted into an electric signal. A photoelectric conversion unit, an integration unit that integrates the output from the photoelectric conversion unit and outputs the integrated state value, a time change rate of the output from the integration unit is detected, and the expected exposure time is calculated from the detected value. The expected exposure time calculation means for calculating, and the output from the expected exposure time calculation means,
Control means for controlling the exposure time by controlling the brightness of the illumination light supplied from the light source to the endoscope so that the exposure time of the photographing surface falls within a predetermined range. Exposure control device for imaging system for endoscope.