JPH0483218A - Exposure controller of photography system for endoscope - Google Patents

Abstract

PURPOSE:To control an exposure time to an ideal time over a wide range by calculating the brightness and exposure time of illumination light at the time of photography from the integral state value of observation light which is sampled right before the photography. CONSTITUTION:The brightness of light to which a photographic surface 25 is exposed is converted into an electric signal by a photoelectric converting means 15, whose output is integrated by an integrating means 16 to output the integral state value. Then a control means calculates the brightness and exposure time of the illumination light at the time of the photography from the integral state value which is outputted by the integrating means 16 right before the photography, and the brightness and exposure time of the illumination light which is supplied from the light source 40 to the endoscope 1 at the time of the photography are controlled according to the calculated value. Consequently, ideal exposure time control which is small both in overexposure and underexposure and in blurring can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exposure control device for an endoscope imaging system that automatically controls exposure time.

[Conventional technology]

Endoscopes are generally capable of not only observing the inside of a body cavity but also taking photographs. The exposure time during photographing is determined by integrating the output of the light receiving element that receives the reflected light from the subject illuminated by the light source, and when the integrated voltage reaches the set voltage, controlled by closing a mechanical shutter.

However, since a mechanical shutter requires time from receiving a closing signal to actually closing the shutter, overexposure occurs due to the delay. The exposure time ΔT for the amount of 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 during close-up photography, the influence of ΔT increases, resulting in significant overexposure.

Conventionally, therefore, the rise of the output of an integral state value obtained by integrating the output of the light receiving element is differentially detected, and when this differential output value is equal to or higher than a reference value, the brightness of the illumination light supplied from the light source device to the endoscope is detected. The total exposure time T was increased by reducing the exposure time to the observation state level, thereby reducing the degree of influence of ΔT (Japanese Patent Publication No. 36928/1983).

[Problem to be solved by the invention]

In an endoscope imaging system, when the exposure time is short, overexposure occurs as described above, but since the subject is a constantly moving living body, when the exposure time is slightly longer, blurring occurs.

Therefore, the ideal exposure time with minimal overexposure and blurring is within a very narrow range.

However, as mentioned above, in the exposure control device of the conventional endoscope imaging system, when the exposure time becomes significantly short, the brightness of the illumination light supplied to the endoscope from the light source device is simply adjusted to match the observation state. Since the exposure time was simply reduced to a certain level and the exposure time was extended, the exposure time was not specifically controlled to fall within a certain range. Therefore, even if the exposure time falls within the ideal range, it is by chance, and overexposure or blurring often occurs.

It is an object of the present invention to provide an exposure control device for an endoscope imaging system that can eliminate such conventional drawbacks and perform ideal exposure time control with less overexposure and less blurring. .

[Means to solve the problem]

In order to achieve the above object, an exposure control device for 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.
A photoelectric conversion means that converts the brightness of the light exposed on the photographing surface of the photographing device after being reflected by the subject into an electrical signal, and an output signal from the photoelectric conversion means is repeatedly transmitted at short intervals during observation state. An integrating means that integrates and outputs the integral state value, and calculates the brightness and exposure time of the illumination light at the time of photographing from the integral state value output from the integral state value immediately before photographing, and calculates the brightness and exposure time of the illumination light at the time of photographing. The present invention is characterized by further comprising a control means for controlling the brightness and exposure time of the illumination light supplied to the endoscope in accordance with the calculated values.

[Effect]

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

〔Example〕

Examples will be described with reference to the drawings.

FIG. 2 shows an endoscope imaging system.

2 is an endoscope, and a camera (photographing device) 2 is detachably attached to the eyepiece 14 of the endoscope via an adapter 3.

4 is a light source device, to which the connector 11 of the endoscope I is detachably connected. Illumination light emitted from the light source (lamp) 40 is collected by a condensing lens 41 and supplied to the light guide fiber 12 of the endoscope.

In the illumination optical path between the light source 40 and the light guide fiber 12, there are provided a shutter (light source shutter) 42 that can be freely opened and closed to fully open or close the illumination optical path, and an aperture 43 that changes the area through which the illumination light passes. It is being

The illumination light is transmitted by the light guide fiber 12 and is irradiated onto the subject 100 from the insertion section distal end 13 of the endoscope. The light reflected by the subject 100 enters the endoscope l, is transmitted by an imager (not shown), and exposes the film surface (photographing surface) 25 of the camera 2. Shutter inside camera 2 (camera shutter) 2
2, only when synchro switch 21 is turned on,
Open for a certain period of time (for example, 0.25 seconds).

Reference numeral 15 denotes a light receiving element provided in the eyepiece 14 to convert the light beam exposed onto the film surface 25 into an electric signal, and its output voltage is integrated by a photometric circuit (integrator circuit) 16 to obtain an integral state. The value is output from the photometric circuit 16.

This photometry circuit 16 may be provided within the light source device 4, but may also be provided within the endoscope 1.

Reference numeral 45 denotes an exposure index setting switch provided on the operation panel 46 on the surface of the light source device 4 in order to set an exposure index that determines the amount of light exposed to the photographing surface 25 of the camera. 47 is a brightness setting switch that sets the brightness of illumination light supplied to the endoscope in the observation state.

50 is a control unit incorporating a microcomputer.

FIG. 3 is a block diagram showing the electrical configuration of the embodiment,
Inside the control unit 50, a ROM (read-only memory) 53 and a RAM (random access memory) are connected to a system bus 52 connected to a central processing unit (CP[J) 51].
54 are connected. The CPU 51 is manually inputted with an output signal from the synchro switch 2I.

Further, first to third input/output ports 56, 57, 58 are connected to the system lotus 52, and an exposure index setting switch 45 and a brightness setting switch 45 are connected to the input end of the first input/output port 56. A switch 47 is connected.

In addition, the output from the light receiving element 15 is connected to a photometry circuit (integrator circuit).
16 and its output, an integral state value (integrated output voltage V), is connected to be input from the multiplexer 61 via the analog-to-digital converter 17 to the second input/output port 57.

Further, the integrated output of the photometric circuit 16 is output from the sample holding circuit 62.
During observation, the highest value of the integral state values is selected from the sample holding circuit 62 by the multiplexer 61 and input to the second input/output port 57.

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

The output end of the third input/output port 58 is connected to drive circuits 40a, 42a, and 43a that control various operations such as the brightness of light emitted by the light source 40, the opening/closing of the light source shutter 42, and the opening degree of the aperture 43.

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

When the synchronization switch 21 of the camera 2 is turned on, the shutter (camera shutter) 22 of the camera 2 opens and closes after a certain period of time (for example, 0.25 seconds) has elapsed. Further, the light source shutter 42 in the light source device 4 is temporarily closed at the same time as the synchro switch 2I is turned on, and after a predetermined short time (initial shutter closing time T) has elapsed, the light source shutter 42 is opened again. The initial shirt closure time T1 is, for example, 0.035.
Seconds.

Before the synchro switch 21 of the camera 2 is turned on, that is, during observation, the output voltage from the light receiving element I5 is integrated every time the sampling pulse is at a low level, and the peak value via the sample holding circuit 62 is selected by the multiplexer 61. is input to the CPU 51.

Then, the time rate of change dV/dt is calculated using the sampling pulse (2), and the exposure time T is calculated based on that value, and when the time T has elapsed, the light source shutter 42 is closed.

The integration execution time by the sampling pulse is TS, its integrated output voltage is ■5, the aperture value of the aperture 43 at that time is f,
shall be. However, f5 is thicker than 0 and less than l, and when the aperture 43 is fully open, f=■. In addition, the reference voltage determined by the exposure index setting switch 45 is
If the ideal exposure time is T (for example, T = 0.01 seconds) and the exposure time is T (when the aperture 43 is fully opened), then d
V/dt=V5/TS T=f5·V,/(dV/dt) (1) When T≧T, the aperture 43 is fully opened and the exposure time T is the value of the above equation.

(2) However, in the case of TNT, the aperture is f, = T/T
, and so on. By changing the opening degree of the diaphragm 43, T becomes T=T.

In either case, the light source shutter 42 is kept open only during this exposure time T, and when the exposure time T has elapsed, the light source shutter 42 is closed.

Next, until the full operation end time T2 is reached, the illumination light supplied to the endoscope is blocked by the light source shutter 42, and nothing is done. Then, when the entire operation end time T2 comes, all the states return to the original observation state. Note that T2 is, for example, 0.5 seconds.

FIG. 5 is a process flow diagram in the control section 50 for performing the operation of the above embodiment. S indicates a step.

This process is performed by pressing the synchro switch 2 of camera 2 during observation.
An interrupt is started when s is turned on, and first, s
Close the light source shutter 42 at t, input the integrated output voltage ■3 from the sampling pulse immediately before photographing at S2, and
The time change rate dV/dt of the integrated output voltage ■ and the exposure time T
Calculate.

Then, in s4, when the exposure time T is equal to or greater than the ideal exposure time 1, the aperture 43 is opened in s5, that is, f=1, and s6
Proceed to. If the exposure time T is shorter than the ideal exposure time T in s4, the aperture 43 is multiplied by T/T in s7, that is, f=T.
/T, substitute T1 for the exposure time T in s8, and proceed to s6.

In s6, the process waits until the initial shutter closing time T has elapsed, and then opens the light source shutter 42 in s9. Then, at slO, it waits until the exposure time T has elapsed since the light source shutter 42 started opening, and then closes the light source shutter 42 at sll.

At the same time, in s12, the aperture 43 is returned to the aperture value f=f5 in the original observation state.

Next, in s13, the process waits until the entire operation end time T2 has elapsed, and in st4, the light source shutter 42 is opened and the process ends.

[Brief explanation of the drawing]

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. 4 is a time chart showing the operation of the embodiment; FIG. 5 is a flow diagram of software that performs control processing in the embodiment. [Effects of the Invention] 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 integral state value of the observation light sampled immediately before imaging. Since the brightness of the illumination light during shooting can be extremely precisely controlled to the optimum condition for shooting, the exposure time is already calculated before shooting, so you can easily adjust the exposure time. It has the excellent effect of controlling the exposure time to an ideal time over a wide range without being influenced by the above, and allowing clear, high-quality photography with less overexposure and less blurring. l... Endoscope, 2... Camera (imaging device), 4... Light source device, 12-... Light guide fiber, 13... Insertion section tip, 15... Light receiving element (photoelectric conversion (Means), 16...Photometry circuit (integration means), 25...-Photographing surface, 40...Light source, 50...Control unit, ■00...Subject.

Claims (1)

[Scope of Claims] A light source that supplies illumination light to an endoscope to illuminate a subject, and converts the brightness of the light that is reflected by the subject and then exposed to the photographing surface of a photographing device into an electrical signal. an integrating means that repeatedly integrates an output signal from the photoelectric converting means in a short period during an observation state and outputs an integral state value thereof; Control that calculates the brightness and exposure time of illumination light during photographing from the state value, and controls the brightness and exposure time of illumination light supplied from the light source to the endoscope during photographing in accordance with the calculated values. 1. An exposure control device for an endoscope imaging system, characterized by comprising: means.