JP2984010B2 - Exposure control device for endoscope imaging system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control device for an endoscope imaging system that automatically controls an exposure time.

[Conventional technology]

In general, an endoscope is capable of not only observing a body cavity but also taking a photograph. At the time of this photographing, the output of the light receiving element that receives the reflected light from the subject is integrated while maximizing the illuminating light beam supplied to the endoscope. The exposure time is controlled by closing a mechanical shutter provided in the illumination light path.

However, since a mechanical shutter requires time from receiving a signal for closing until actually closing the shutter, the exposure is excessive due to the delay. The exposure time ΔT corresponding to the excessive exposure is constant irrespective of the length of the total exposure time T at that time. Therefore, the total exposure time T
Is short, that is, when the subject is bright, such as during close-up photography, the effect of ΔT is large, resulting in significant overexposure.

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 larger than the reference value, the brightness of the illumination light supplied from the light source device to the endoscope is reduced. The total exposure time T is lengthened by reducing to the observation state level, and the degree of influence of ΔT is reduced (Japanese Patent Publication No. 61-36928).

[Problems to be solved by the invention]

However, even with the overexposure countermeasures described above, the illumination light flux is once maximized at the time of photographing, so that the correction of the illumination light flux may not be completed in close proximity shooting or when using a high sensitivity film. Overexposure occurred. In addition, since the brightness of the illumination light is simply reduced to the level at the time of observation after the correction, fine control is not performed, and the exposure time becomes too long, causing a problem such as blurring.

The present invention solves such a conventional drawback, and can finely adjust the brightness of illumination light at the time of shooting,
It is an object of the present invention to provide an exposure control apparatus of an endoscope imaging system capable of performing ideal exposure control with less overexposure and blur.

[Means for solving the problem]

In order to achieve the above object, an exposure control device of an endoscope imaging system according to the present invention includes a light source that supplies illumination light for illuminating a subject to an endoscope, as shown in FIG. Exposure index setting means for setting an exposure index for determining an exposure amount to be exposed on an imaging surface of an imaging device after being reflected by the subject, and brightness of illumination light supplied to the endoscope in an observation state. Setting of the observation light brightness, the exposure index set by the exposure index setting means, and the illumination light brightness at the time of observation set by the observation light brightness setting means. And control means for calculating the brightness and controlling the brightness of the illumination light supplied to the endoscope at the time of photographing to the calculated brightness.

[Action]

From the exposure index set by the exposure index setting means and the illumination light brightness at the time of observation set by the observation light brightness setting means, the optimal illumination light brightness at the time of shooting is calculated and supplied to the endoscope at the time of shooting. The exposure time is controlled after the brightness of the illumination light to be controlled is controlled to the calculated brightness.

〔Example〕

 Embodiments will be described with reference to the drawings.

FIG. 2 shows an imaging system of the endoscope. Reference numeral 1 denotes an endoscope, and a camera (photographing 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 a 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.

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

Then, the illumination light is transmitted by the light guide fiber 12, and is irradiated on the subject 100 from the distal end 13 of the insertion portion of the endoscope. The light reflected by the subject 100 is transmitted by an image guide fiber (not shown) and exposes a film surface (photographing surface) 25 of the camera 2. The shutter (camera shutter) 22 in the camera 2 opens for a certain 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 section 14 for converting a light beam exposed on the film surface 25 into an electric signal, and its output voltage is integrated by a light measuring circuit (integrating circuit) 16 to obtain an integrated state. The value is output from the photometry circuit 16. The photometric circuit 16 may be provided in the light source device 4 or may be provided in the endoscope 1.

Reference numeral 45 denotes an exposure index setting switch provided on an operation panel 46 on the surface of the light source device 4 for setting an exposure index EI for determining an exposure amount exposed on the photographing surface 25 of the camera. For example, as shown in FIG. 3, it is provided so that the exposure amount can be adjusted in 0.5 EV units.

47 is a brightness index setting switch for setting the brightness of illumination light (hereinafter referred to as “luminous flux”) to be supplied to the endoscope in the observation state according to the distance from the insertion end 13 to the subject 100 and the like. Specifically, as shown in FIG. 4, for example, the brightness at the time of observation (that is, the luminous flux supplied to the endoscope) can be adjusted by a brightness index BI of 0.5 EV unit. it can.

The Te number and Tb number shown in FIGS. 3 and 4 are integer values used in the present embodiment to simplify the calculation.

Reference numeral 50 denotes a control unit incorporating a microcomputer.

FIG. 5 is a block diagram showing an electrical configuration,
In 50, a ROM 53 and a RAM 54 are connected to a system bus 52 connected to a central processing unit (CPU) 51. CPU51
, An output signal from the synchro switch 21 is interrupted.

Further, first to third input / output ports 56, 57, 58 are connected to the system bus 52.
Are connected to an exposure index setting switch 45 and a brightness index setting switch 47. In the present embodiment, the brightness index BI is set by a manual operation according to the distance to the subject or the like, but may be automatically set.

The output from the light receiving element 15 is a photometric circuit (integrating circuit).
The second input / output port 57 is connected so that it is integrated at 16 and the integrated state value (integrated output voltage V) is input to the input terminal of the second input / output port 57 via the analog / digital converter 17. Drive circuits 40a, 42a, 43a for controlling operations such as light emission brightness of the light source 40, opening and closing of the light source shutter 42, and opening of the aperture 43 are connected to the output terminal of the third input / output port 58.

Also, an initial shutter closing signal generating means for generating a signal for keeping the light source shutter closed for a predetermined short period in conjunction with the turning on of the synchro switch 21; Means for generating an entire operation period signal for limiting the period are provided, and their output signals are input to the control unit 50, but these are not shown.

FIG. 6 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 with a slight delay, and closes after a certain time (for example, 0.25 seconds). Also,
Simultaneously with the turning on of the synchro switch 21, the light source shutter 42 in the light source device 4 is once closed by the initial shutter closing signal, and the entire operation period signal is turned on.

When the initial shutter closing signal falls after a predetermined short time has elapsed, the light source shutter 42 starts to open at the same time.

Before that, when the light source shutter 42 is closed, one or both of the light emission brightness of the light source 40 and the opening degree of the aperture 43 are changed, and the illumination light flux Φ at the time of shooting is controlled.

The illumination light flux Φ at the time of shooting is calculated from the above-described exposure index EI and brightness index BI. If this is shown in a specific example, as shown in FIGS. 3 and 4, the setting range of the exposure index EI of the light source device is set to 0 to 9, and the setting range of the brightness index BI is set to 0 to 9. And the standard exposure index
When EI = 5, brightness index BI = 5, and the subject 100 is at a standard distance (for example, 20 mm from the insertion portion distal end 13) and the illumination light beam supplied to the endoscope at the time of photographing is the standard brightness Φs, the proper exposure is performed. It is assumed that the opening time of the light source shutter 42 for obtaining the target value is an ideal value (for example, 0.01 second). Under such a premise, the brightness Φ of the illumination light beam at the time of photographing is set as Φ = Φs · 2 ^{(5-EI) / 2} · 2 ^{(BI−5) / 2k} . Here, k is a constant of k ≧ 1.

By calculating Φ in this manner and controlling the illuminating light flux to that value, Φ = Φs in the above-described standard state.
The light source shutter 42 closes in 0.01 seconds.

When the exposure index EI is higher than the standard state (that is, when the exposure is properly exposed with a small amount of exposure) and the brightness index
When BI is small (that is, when the distance to the subject 100 is short and the illumination light flux at the time of observation is reduced), Φ becomes small, so that the exposure time does not become short and the overexposure does not occur.

Conversely, when the exposure index EI is smaller than the standard state (that is, when a large amount of exposure is required for proper exposure shooting)
When the brightness index BI is large (that is, when the distance to the subject 100 is long and the illumination light flux at the time of observation is large), Φ becomes large, so that the exposure time is not extended and blur occurs. do not do.

The reason why k in the equation for calculating Φ is a constant of 1 or more is as follows.

That is, the exposure index EI may be obtained by exactly multiplying the exposure time by ^21/2 times or 2-1 ^/ 2 times each time the numerical value has a difference of "1". However, the value of the brightness index BI is not always directly reflected in the exposure time. In general, the effect of BI is smaller than the effect of EI. Therefore, when setting the illumination light flux Φ at the time of shooting, the influence of BI is made smaller than that of EI by setting k ≧ 1.

The value of k is determined from a photographing test or the like.
FIG. 4 shows the number of Tb in the case of 2 and FIG.
From the illustration of FIG. 5, the relationship of Tb = BI + 1 Te = 20−2 · EI is established. Therefore, when k = 2, Φ
Is calculated as Φ = Φs · 2 ^{(Te + Tb−16) / 4} .

FIG. 7 is a flowchart of a control process performed by the control unit 50 to perform the operation of the above embodiment. s indicates a step.

This process starts when the synchro switch 21 of the camera is turned on. First, the light source shutter 42 is closed in s1, then Φ is calculated in s2, and the light source shutter is set so that the value is actually obtained as the illumination light flux. One or both of the light emission brightness 40 and the aperture of the aperture 43 are controlled.

Then, the initial shutter close signal is input in s3, and if the signal is not low level in s4, the process returns to s3 and repeats from the initial shutter close signal input, and if the signal becomes low level in s4, the light source shutter 42 in s5. open.

Subsequently, the entire operation period signal is input in s6, and if the signal is not high level in s7, the process proceeds to s13. When the signal is at a high level, the integrated output voltage V is input at s8, and
Is determined to have reached the set voltage Vr.

If V ≧ Vr is not satisfied in s9, repeat from s6, and V ≧ Vr
, The light source shutter 42 is closed in s10. And s
If the signal is not at the low level in s12 when the signal is not at the low level in step 11, the operation is repeated from the signal input in the entire operation period in step s11.

Finally, the light source shutter 42 is opened in s13, and the illumination light flux is returned to the state before photographing in s14, and the processing ends.

〔The invention's effect〕

According to the exposure control apparatus of the imaging system for an endoscope of the present invention, the brightness of the illumination light at the time of imaging is calculated from the exposure index and the brightness of the illumination light at the time of observation, and the calculated brightness at the time of imaging. Control, the brightness of the illumination light during shooting can be finely controlled, and the exposure time can be controlled to the ideal time, and clear, high-quality shooting with less overexposure and blurring can be achieved. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a schematic diagram of the entire embodiment, FIGS. 3 and 4 are tables showing examples of setting of an exposure index and a brightness index, and FIG. FIG. 6 is a block diagram of an electric circuit, FIG. 6 is a time chart showing the operation of the embodiment, and FIG. 7 is a control processing flowchart of the embodiment. DESCRIPTION OF SYMBOLS 1 ... Endoscope, 2 ... Camera (photographing device), 4 ... Light source device, 12 ... Light guide fiber, 13 ... Insertion end, 45 ... Exposure index setting switch, 47 ... Brightness index Setting switch, 50 ... Control unit.

Continuation of the front page (56) References JP-A-58-75526 (JP, A) JP-A-61-13236 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 23 / 26 A61B 1/04 362

Claims (1)

(57) [Claims] A light source for supplying illumination light for illuminating a subject to an endoscope; and an exposure index for determining an exposure amount for exposing a photographic surface of a photographic device after being reflected by the subject. Exposure index setting means, observation light brightness setting means for setting the brightness of illumination light supplied to the endoscope in the observation state, exposure index set by the exposure index setting means, and the observation light brightness The brightness of the illumination light at the time of photographing is determined by the exposure index from the illumination light brightness at the time of observation, which is multiplied by a constant for reducing the influence on the calculation result from the exposure index, which is set by the length setting means. It is calculated to increase or decrease in accordance with the magnitude of the exposure amount to be performed and the brightness of the observation light during the observation, and the brightness of the illumination light supplied to the endoscope at the time of photographing is calculated. Control hand to control brightness The exposure control apparatus of the endoscopic imaging system characterized in that a and.