JP2958065B2 - 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. The exposure time at the time of this photographing is obtained by integrating the output of the light receiving element that receives the reflected light from the object illuminated by the light source, and providing the integrated voltage to the illumination light path in the light source device when the integrated voltage reaches the set voltage. Controlled by closing the mechanical shutter.

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 becomes large, resulting in remarkable excessive exposure.

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]

In an imaging system for an endoscope, when the exposure time is short, the overexposure occurs as described above. However, since the subject is a living body that constantly moves, a problem of blurring occurs when the exposure time is slightly increased. Therefore, the ideal exposure time in which both overexposure and blur are small is in a very narrow range.

However, as described above, in the exposure control apparatus of the conventional endoscope imaging system, when the exposure time becomes extremely short, the brightness of the illumination light supplied from the light source device to the endoscope is simply changed to the observation state. Since the exposure time was extended only by reducing the exposure time to a level, the exposure time is not specifically controlled to be within a certain range. Therefore, even if the exposure time 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 apparatus for an endoscope imaging system that can solve such conventional drawbacks and can perform ideal exposure time control with less overexposure and less 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. Photoelectric conversion means for converting the brightness of light, which is reflected on the photographing surface of the photographing device after being reflected by the subject, into an electric signal; and repeating an output signal from the photoelectric conversion means in a short cycle in an observation state. Integrating means for integrating and outputting the integrated state value, and calculating the brightness and exposure time of the illuminating light at the time of shooting from the integrated state value output from the integrating means immediately before shooting, and Control means for controlling the brightness and the exposure time of the illumination light supplied to the endoscope in accordance with the calculated value is provided.

[Action]

The brightness of the light exposed on the photographing surface is converted into an electric signal by the photoelectric conversion means, and the output is integrated by the integration means to output an integrated state value. Then, in the control means, the brightness and the exposure time of the illuminating light at the time of shooting are calculated from the integration state value output from the integrating means immediately before the shooting, and the illuminating light supplied to the endoscope from the light source at the time of shooting. The brightness and the exposure time are controlled according to the calculated values.

〔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 (lamp) 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 illuminating light is transmitted by the light guide fiber 12, and is applied to the subject 100 from the distal end 13 of the insertion portion of the endoscope. The light reflected by the subject 100 enters the endoscope 1 and is transmitted by an image guide fiber (not shown) to expose the 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 for determining an exposure amount to be exposed on the photographing surface 25 of the camera.
Reference numeral 47 denotes a brightness setting switch for setting the brightness of the illumination light supplied to the endoscope in the observation state.

Reference numeral 50 denotes a control unit incorporating a microcomputer.

FIG. 3 is a block diagram showing an electrical configuration of the embodiment. In a control unit 50, a ROM (read only memory) 53 is connected to a system bus 52 connected to a central processing unit (CPU) 51.
And a random access memory (RAM) 54 are connected. An output signal from the synchro switch 21 is interrupted to the CPU 51.

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 setting switch 47.

The output from the light receiving element 15 is a photometric circuit (integrating circuit).
The second input / output port 57 is connected so that the integrated state value (integrated output voltage V) which is integrated at 16 and output from the multiplexer 61 is input to the second input / output port 57 via the analog / digital converter 17.

Further, the integrated output of the photometric circuit 16 is also input to the sample holding circuit 62, and at the time of observation, the highest value of the integrated state value is selected by the multiplexer 61 from the sample holding circuit 62 and input to the second input / output port 57. It has become.

The clock signal output from the timer 63 connected to the system bus 52 is input to the sampling circuit 64, and a sampling pulse is output to the photometry circuit 16 in synchronization with the clock. Then, at the time of observation, when the sampling pulse is at a low level, the photometry circuit 16 performs integration, and when the sampling pulse is at a high level, the integrated output becomes zero (that is, V = 0). The sampling frequency is set to, for example, about 500 Hz.

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.

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 and closes after a certain time (for example, 0.25 seconds). Further, the light source shutter 42 in the light source device 4 is once closed simultaneously with the turning on of the synchro switch 21, and after a predetermined short time (the desired shutter closing time T ₁ ) elapses, the light source shutter 42 is opened again. Desired shutter closing time T ₁ is, for example, 0.035 seconds.

Before the synchro switch 21 of the camera 2 is turned on, that is, at the time of observation, the output voltage from the light receiving element 15 is integrated every time the sampling pulse is at a low level, and the peak value passed through the sample holding circuit 62 is selected by the multiplexer 61. It is input to CPU51.

Then, according to the peak value, the time change rate dV / d
The exposure time T is calculated based on t, and the light source shutter 42 is closed when the time T has elapsed.

The integration execution time by the sampling pulse is T _S , the integrated output voltage is V _S , and the aperture value of the aperture 43 at that time is f _S. However, f _S is 1 greater than 0 and less than or equal, when diaphragm 43 is fully opened is f _S = 1. The reference voltage determined by the exposure index setting switch 45 is V _r , and the ideal exposure time is
Assuming that T _i (for example, T _i = 0.01 second) and the exposure time is T (when the aperture 43 is fully opened), dV / dt = V _S / T _S T = f _S · V _r / (dV / dt) Yes, (1) when the T ≧ T _i, the exposure time the aperture 43 fully opened T
Is the value of the above equation.

(2) However, when T <T _i , the aperture is set to f _S = T / T _i . By changing the opening of the throttle 43, T becomes T = T _i .

In any case, the light source shutter 42 is opened only during the exposure time T, and the light source shutter 42 after the exposure time T has elapsed is closed.

Then, until reaching the total operating end time T ₂ are, illumination light supplied to the endoscope is blocked by the light source shutter 42 is the time nothing done. When it goes the entire operating period end time T _2, all of the state returns to the original observation state. Incidentally, T ₂ is, for example, 0.5 seconds.

FIG. 5 is a processing flow chart in the control unit 50 for performing the operation of the above embodiment. s indicates a step.

This processing is performed by the sync switch 21 of the camera 2 during observation.
Is started by turning on, and first, s1
Then, the light source shutter 42 is closed, the integrated output voltage V _S by the sampling pulse immediately before photographing is input at s2, and the time change rate dV / dt of the integrated output voltage V and the exposure time T are calculated at s3.

Then at s4, when the exposure time T is equal to or greater than the ideal exposure time T _i releases the 43 stop at s5, i.e. proceeds to s6 in the f = 1. When the exposure time T is shorter than the ideal exposure time T _{i in} s4,
At s7, the aperture 43 is set to T / T _i times, that is, f = T / T _i , and at s8, T _i is substituted for the exposure time T, and the process proceeds to s6.

In s6, wait until the initial shutter closing time T ₁ is passed, opening the light source shutter 42 at s9. Then, in s10, the process waits until the exposure time T elapses from the start of opening of the light source shutter 42, and then closes the light source shutter 42 in s11. And at the same time, s
12 returns the diaphragm 43 to the aperture value f = f _S of the original observation state.

Then in s13, wait until the entire operating end time T ₂ has elapsed, at s14, ends open source shutter 42.

〔The invention's effect〕

According to the exposure control device of the endoscope imaging system of the present invention, the brightness of the illumination light at the time of imaging is calculated from the integrated state value of the observation light sampled immediately before imaging, and is controlled to the brightness. Therefore, the brightness of the illuminating light at the time of shooting can be controlled very accurately to the optimum state for shooting, and the exposure time is already calculated before shooting, so it is completely affected by the length of exposure time etc. Without this, there is an excellent effect that the exposure time is controlled to an ideal time in a wide range so that clear and high quality photographing with less overexposure and blur can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the configuration of the present invention, FIG. 2 is a schematic diagram of the configuration of the embodiment, FIG. 3 is a circuit block diagram of the embodiment, FIG. FIG. 5 is a flowchart of software for performing control processing of the embodiment. DESCRIPTION OF SYMBOLS 1 ... Endoscope, 2 ... Camera (photographing apparatus), 4 ... Light source apparatus, 12 ... Light guide fiber, 13 ... Tip of insertion part, 15 ... Light receiving element (photoelectric conversion means), 16 ... Photometry circuit (integrating means), 25: shooting surface, 40: light source, 50: control unit, 100: subject.

──────────────────────────────────────────────────続 き Continued on the front page (72) Tadashi Takahashi Inventor Asahi Kogaku Kogyo Co., Ltd. 2-36-9 Maeno-cho, Itabashi-ku, Tokyo (56) References JP-A-54-132380 (JP, A) 1984-204028 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G02B 23/26

Claims (1)

(57) [Claims] 1. A light source for supplying illumination light for illuminating a subject to an endoscope, and converting the brightness of light, which is reflected by the subject and is exposed on a photographing surface of a photographing apparatus, into an electric signal. An exposure control apparatus for an endoscope imaging system, comprising: a photoelectric conversion unit that performs the above operation; and an integration unit that periodically and repeatedly integrates an output signal from the photoelectric conversion unit and outputs an integrated state value. The brightness and the exposure time of the illumination light at the time of shooting are calculated from the integration state value output from the integration means, and the brightness and the exposure time of the illumination light supplied to the endoscope from the light source at the time of shooting are calculated as described above. An exposure control apparatus for an endoscope imaging system, further comprising control means for performing control in accordance with a calculated value.