JPH02291516A - Automatic light quantity control circuit for electronic endoscope device - Google Patents

Abstract

PURPOSE:To improve the gradation of a highlight part in the somatic cavity and to prevent the inner part of the somatic cavity from being hard to see by providing a means which extracts a signal above a white-peak side prescribed level from an electric signal obtained from a solid-state image pickup element and amplifies it and a means which applies the amplified signal to a detecting circuit. CONSTITUTION:The circuit 62 extracts the signal above the white-peak side prescribed level, i.e. the signal above the saturation level of the solid-state image pickup element from the electric signal obtained from the solid-state image pickup element and the means 63 amplifies the extracted signal. The extracted and amplified signal is applied to the detecting circuit 64 to increase the DC level of the detecting circuit 64 forcibly. Consequently, feedback control is so performed that the quantity of illumination light emitted from the tip of an endoscope decreases, namely, the DC level of the detecting circuit 64 reaches a specific reference level. Consequently, the quantity of illumination light can be made larger than before and the gradation of the highlight part in the somatic cavity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic light amount control circuit, and more particularly to an automatic light amount control circuit for an electronic endoscope device that automatically controls the amount of illumination light emitted from the tip of an endoscope. .

[Conventional technology]

FIG. 1 is a block diagram showing an example of an electronic endoscope device, in which light from an illumination lamp 10 is filtered through a near-infrared removal filter l1.
, a subject l8 from the end of the endoscope via the aperture 12, lens l3, color filter disk 14 and light guide l6.
to illuminate. That is, the color filter disk l4 has a red filter, a green filter, and a blue filter, each having a central angle of 120 degrees, and is rotated by the motor 20 at a predetermined rotational speed (for example, 20 rps). As a result, the light from the illumination lamp 1O passes through the rotating color filter disk 14 and changes red (R) sequentially at a cycle of 1/60 seconds.
), green (G), and blue (B), and is applied to the subject l8 via the light guide 16.

The imaging lens 22 provided at the tip of the endoscope includes RSG,
Image the subject l8 illuminated by each illumination light of B,
This is imaged on the light receiving section of a solid state imaging device (CCD) 24. The CCD 24 is driven by a CCD drive circuit 3l that outputs a CCD drive signal in synchronization with a timing pulse applied from a synchronization circuit 30, and sequentially outputs R, G, and B color signals corresponding to each of the R, G, and B illumination lights. White balance adjustment circuit 2 via low-pass filter 25 and amplifier 26
Output to 8.

The white balance adjustment circuit 28 amplifies the RXG and B sequential color signals with predetermined gains, and in particular, the gains for the R and B signals can be adjusted respectively. Note that the gains for the R and B signals are adjusted so that, for example, when a white image is captured in advance, a white reproduced image is obtained.

R, G, output from the white balance adjustment circuit 28,
The B frame-sequential color signal is subjected to gamma correction in a gamma correction circuit 34, and then converted into a digital signal by an A/D converter 36 and added to field memories 40, 42, and 44.

The field memories 40, 42, and 44 are for converting R, G, and B sequential color signals into simultaneous color signals, and are driven and controlled by the memory control circuit 38. That is, the memory control circuit 38 receives the RSGSB from the synchronization circuit 30.
Enable signal REN% synchronized with each illumination light of GEN
SBEN is input, and in order to store the color signal corresponding to each illumination light in the field memory corresponding to that color, a write signal is sequentially output to each field memory 40, 42, 44, and two fields of video information are stored. memory,
The contents of the field memory are updated in the third field. Digital information of R, G, and B color signals simultaneously read out from these field memories 40, 42, and 44 are converted into analog signals via D/Δ converters 50, 52, and 54, respectively, and output. Then, the R, G, and B simultaneous color signals converted into simultaneous signals as described above are converted into composite color video signals via the color encoder 56, and are added to a color monitor and reproduced as a color image. Ru.

Incidentally, the amount of light irradiated from the tip of the endoscope to the illumination destination is adjusted by the aperture 12, and the aperture amount of the aperture 12 is controlled by an automatic light amount control circuit (ALC circuit).

That is, the conventional ALC circuit is composed of an amplifier 1, a detection circuit 2, a differential amplifier 3, a level setter 4, and a drive circuit 5, as shown in FIG. The R, G, and B color signals applied from the circuit shown in FIG. 1 are amplified by an amplifier 1 and then applied to a detection circuit 2. The DC level detected by this detection circuit 2 is
A predetermined reference level is added to the negative power of the differential amplifier 3, and a predetermined reference level is added to the positive power of the differential amplifier 3 from a level setter 4.

The differential amplifier 3 amplifies the deviation between the two forces and outputs the drive circuit 5.
The drive circuit 5 drives the diaphragm mechanism and controls opening and closing of the diaphragm 12 in accordance with the human power signal.

That is, when the DC level detected by the detection circuit 2 is higher than a predetermined reference level, the diaphragm 12 is driven in the direction of closing to reduce the amount of illumination light, so that the DC level is higher than the predetermined reference level. If it is small, drive the aperture 12 in the direction of opening to increase the amount of illumination light, thereby
The amount of light incident on the CD 24 is optimized.

[Problem to be solved by the invention]

However, the lattice code of a solid-state image sensor is narrow, and when the aperture is opened, objects in front of the body cavity become saturated as soon as the solid-state image sensor is saturated, and when the aperture is slightly closed,
There is a problem in that the interior of the body cavity is so dark that it becomes difficult to see, significantly degrading the image quality of the monitor display. Conventionally, S in the body cavity
In order to obtain a clear image with good / It had the disadvantage of easily collapsing.

The present invention has been made in view of the above circumstances, and is an electronic internal device that can be used with a larger amount of illumination light than before, and that can improve the whitening of highlighted areas in body cavities. The purpose is to provide a viewing device.

[Means to solve problems]

In order to achieve the above object, the present invention includes a detection circuit that detects an electrical signal obtained from a solid-state image sensor disposed at the tip of an endoscope, and the signal detected by the detection circuit reaches a predetermined reference level. In the automatic light amount control circuit of an electronic endoscope device that controls the amount of illumination light emitted from the tip of the endoscope, a signal that is higher than a specified level on the white peak side of the electrical signals obtained from the solid-state image sensor is It is characterized by comprising means for extracting and amplifying the signal, and means for applying the extracted and amplified signal to the detection circuit.

[Effect]

According to the present invention, from among the electric signals obtained from the solid-state image sensor, a signal that is higher than a specified level on the white peak side, for example, a signal that is higher than the saturation level of the solid-state image sensor is extracted and amplified. Then, by applying this extracted and amplified signal to the detection circuit, the DC level of the detection circuit is forcibly increased. As a result, feedback control is performed so that the amount of illumination light emitted from the endoscope tip is reduced, that is, the DC level of the detection circuit is brought to a predetermined reference level. Thereby, the solid-state image sensor is controlled so that a signal higher than a specified level on the white peak side is not outputted, and an image without white collapse is obtained.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an automatic light amount control circuit for an electronic endoscope apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a block diagram showing an embodiment of an automatic light amount control circuit for an electronic endoscope device according to the present invention.

This ALC circuit is an ALC circuit applied to the electronic endoscope device shown in FIG. It is composed of a setting device 66 and a drive circuit 67.

In the above ALC circuit, white balance adjustment circuit 2
8 (FIG. 1) are amplified by an amplifier 60 and added to a summing point 61. On the other hand, the R and GSB color signals are processed by the white level extraction circuit 6.
It has been added to 2.

The white level extraction circuit 62 clips and extracts signals of R, G, and B color signals that are higher than a specified level on the white peak side, for example, G and B color signals that are higher than the R saturation level.

The reason why the above prescribed level is the saturation level of R is that
is saturated first, and even if only R out of the three colors R, G, and B is saturated on the monitor display screen, there is little impression of washed out whites.
This is because it is not until the GSB is saturated that the whites appear washed out.

The signal extracted by the white level extraction circuit 62 is
After being amplified by an amplifier 63, it is added to a summing point 61.

The addition point 61 adds the two human input signals and outputs the result to the detection circuit 64, which performs average value detection or peak value detection on these human input signals.

The DC level detected by the detection circuit 64 is added to the power of the differential amplifier 65. A predetermined reference level is added to the negative power of the differential amplifier 65 from a level setter 66. Note that this reference level is appropriately set so that the amount of incident light corresponds to one step before saturation of the CCD 24 in order to obtain a clear image of the inside of the body cavity.

The differential amplifier 65 amplifies the difference between the two manual forces and outputs it to the drive circuit 67, and the drive circuit 67 drives, for example, an iris motor and controls the opening and closing of the aperture 12 in accordance with the human power signal. Thereby, the amount of illumination light is automatically controlled so that the DC level detected by the detection circuit 64 is always at a predetermined reference level.

Next, the operation of the ALC circuit having the above configuration will be explained.

First, in a shooting state below a specified level without white collapse, the white level extraction circuit 62 does not extract the signal, and the R and GSB color signals are added to the detection circuit 64 only from the route via the amplifier 60. It will be done. This results in
It operates in the same way as the conventional ALC circuit shown in FIG. 6, and when the DC level detected by the detection circuit 64 is higher than a predetermined reference level, the aperture 12 is driven in the direction of closing to reduce the amount of illumination light. When the DC level is lower than a predetermined reference level, the aperture 12 is driven in the direction of opening to increase the amount of illumination light, so that the amount of light incident on the CCD 24 is optimized.

On the other hand, when a part of the subject is close to the endoscope tip, the amount of incident light from the close part increases, causing whiteout. In a photographing state in which white collapse occurs, the white level extraction circuit 62 receives a signal higher than the R saturation level and extracts a signal higher than the saturation level. This extracted signal is amplified by an amplifier 63, and then added to the signal from the amplifier 60 at a summing point 6l and applied to a detection circuit v464.

As a result, the DC level output from the detection circuit 64 suddenly increases due to the signal applied via the white level extraction circuit 62 and the amplifier 63, and as a result, the aperture 12 is adjusted so that this DC level becomes a predetermined reference level. is controlled in the closing direction, and the whitening is immediately eliminated.

FIG. 3 shows a specific circuit example of the above ALC circuit.

The same parts as in Fig. 2 are given the same reference numerals.
A detailed explanation thereof will be omitted.

In FIG. 3, the RSG,B color signal is sent to the amplifier 70.
After being amplified, the signal is applied to the detection circuit 72. On the other hand, the transistor Tr, the clip level setter 74, etc. constitute a white level extraction circuit and an amplifier, and the RSG
, B are applied to the emitter of transistor Tr.

The clip level setter 74 sets the clip level to, for example, the saturation voltage level of R, and manually applies the clip level to the base of the transistor Tr.

Therefore, when the R, G, and B color signals applied to the emitter of the transistor Tr exceed the above-mentioned clip level, the transistor Tr turns on and applies a signal higher than the clip level to the detection circuit 72 via the diode D. .

Note that each resistor R is adjusted so that the power gain of the signal outputted to the detection circuit 72 via the transistor Tr is larger than that of the signal outputted to the detection circuit 72 via the amplifier 70.
Resistance values of 1 to R are selected.

FIGS. 4 and 5 are block diagrams showing other embodiments of the ALC circuit according to the present invention, respectively.

The same parts as in Fig. 2 are given the same reference numerals.
A detailed explanation thereof will be omitted.

The ALC circuit in Figure 4 is the summation point 6 of the ALC circuit in Figure 2.
1. This is different from the ALC circuit shown in FIG. 2 in that a maximum value detection circuit 76 is used instead of the detection circuit 64. That is, the maximum value detection circuit 76 shown in FIG. 4 selects and detects the largest signal from among the signals inputted to the input signal and the B input via the amplifiers 60 and 63, respectively.

The ALC circuit shown in FIG. 5 is second in that a pulse width modulation circuit 78 is provided between the amplifier 63 and the addition point 61.
This is different from the ALC circuit shown in the figure. That is, the pulse width modulation circuit 78 in FIG. 5 converts the signal applied from the amplifier 63 into a signal with a pulse width corresponding to the amplitude of the signal, and adds the signal to the addition point 61. Thereby, even if the DC component of the signal extracted by the white level extraction circuit 62 is small, it can be added as a signal that can easily change the DC level of the detection circuit 64.

In this embodiment, the saturation voltage level of R is used as the prescribed level on the white peak side, but the present invention is not limited to this, and any prescribed level may be used as long as the presence or absence of white collapse can be detected. Further, the present invention is not limited to an R, GSB frame sequential type electronic endoscope device, but can also be applied to a simultaneous type electronic endoscope device.

〔Effect of the invention〕

As explained above, according to the automatic light amount control circuit for the stomach equipped with an electronic endoscope according to the present invention, it is possible to improve the whitening of the highlight part in the body cavity, and it is also possible to use the aperture opened more than before. As a result, the problem of the interior of the body cavity becoming dark and visible can be alleviated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the overall configuration of an electronic endoscope device, FIG. 2 is a block diagram showing an example of an automatic control circuit for the electronic endoscope device according to the present invention, and FIG. FIG. 2 is a diagram showing a specific circuit side of the automatic light amount control circuit, and FIGS. 4 and 5 are block diagrams showing other embodiments of the automatic light amount control circuit for an electronic endoscope apparatus according to the present invention. FIG. 6 is a block diagram showing an example of an automatic light amount control circuit of a conventional electronic endoscope device. 12... Aperture, 24... Solid-state image sensor (CCD)
, 60, 63...Amplifier, 6l...Summing point, 6
2... White level extraction circuit, 64, 72... Detection circuit, 65... Differential amplifier, 66... Level setter, 67... Drive circuit, 74... Clip level setter, 76... Maximum value detection circuit, 78... Pulse width modulation circuit.

Claims (1)

[Claims] The endoscope has a detection circuit that detects an electrical signal obtained from a solid-state image sensor disposed at the tip of the endoscope, and the endoscope is configured so that the signal detected by the detection circuit reaches a predetermined reference level. In an automatic light amount control circuit of an electronic endoscope device that controls the amount of illumination light irradiated from the tip, a signal above a specified level on the white peak side is extracted from the electrical signals obtained from the solid-state image sensor and amplified. An automatic light amount control circuit for an electronic endoscope apparatus, comprising: means for applying the extracted and amplified signal to the detection circuit.