JPH02262114A - Electron endoscope device - Google Patents

Abstract

PURPOSE:To improve the color reproducibility and picture quality of a color image by selecting one or two of surface sequential chrominance signals of R, G, and B and outputting the surface sequential chrominance signals through a nonlinear circuit. CONSTITUTION:A B selecting knee circuit outputs the surface sequential chrominance signals of red(R) and green(G) through emitter followers TR1 and TR2. The surface sequential chrominance signal of blue(B), on the other hand, is outputted through the emitter followers TR1 and TR2 and when a switch SW is turned on and its signal level exceeds the level VE at a knee point, a part of the signal flows to the emitter of an emitter follower TR3 through a variable resistor R1, a diode D, and the switch SW. Thus, the surface sequential chrominance signals of R, G, and B are outputted through the knee circuit to nearly equalize the level ratio of the surface sequential chrominance signals of R, G, and B irrelevantly to variation in the quantity of irradiating light. Consequently, the reproducibility of colors of an object and the picture quality are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic endoscope device, and particularly to an electronic endoscope device that captures images in a frame sequential manner.

[Conventional technology]

Electronic endoscope devices used for medical and industrial purposes use a single solid-state image sensor (hereinafter referred to as CCD) to reduce the diameter of the endoscope body (electronic scope). It is inserted into the human body, etc., and red, green, and blue illumination light is sequentially irradiated toward the observation target from the illumination device built into the ProSensor, and the reflected image from the observation target is captured on a CCD.
By performing photoelectric conversion, RSG and B frame-sequential color signals are obtained.

The frame-sequential color signals are then transmitted to a processor, where signal processing such as simultaneous conversion is performed, and then added to a display device, where the image of the observed area is displayed in color. be done.

[Problem to be solved by the invention]

Generally, when capturing an image of a white subject, it is preferable that the R and GSB sequential color signals sequentially output from the CCD be at approximately the same level in order to faithfully reproduce colors. The long wavelength sensitivity of this region tends to be high, and the short wavelength sensitivity of blue light tends to be low. Also, C
CD R,G.

Since the r characteristics of photoelectric conversion for B light are different, the level ratio of the RSC, B CCD output signals changes depending on the intensity of the irradiated light, resulting in a problem that the color balance is disrupted.

In particular, the change in the B signal among the signal level ratios is remarkable; as shown in Figure 6, when the illuminance is low, the B signal is smaller than the other RSG signals, and when the illumination is high, the RSG signal is smaller than the other RSG signals.
It tends to be larger than the SG signal.

If the color balance is disrupted, the colors will not be faithfully reproduced when the observation target portion is displayed on the display device, resulting in deterioration of image quality.

The present invention has been made in view of these circumstances, and it is possible to always use R and G regardless of changes in the amount of irradiated light.

It is an object of the present invention to provide an electronic endoscope device that can maintain the level ratio of B frame sequential color signals almost constant, and can improve the color reproducibility of color images and improve the image quality.

[Means to solve problems]

In order to achieve the above object, the present invention irradiates a subject with time-series color-separated light from the tip of an endoscope, and captures the reflected image from the subject using a solid-state image sensor disposed at the tip of the endoscope. An electronic endoscope that receives light, obtains RlG and B frame-sequential color signals from the solid-state imaging device, and converts the frame-sequential color signals into simultaneous color signals through a memory means to obtain a color video signal. In the device, one color or two colors are selected from the R and GSB field sequential color signals, and the field sequential color signals of the selected colors are outputted via a non-linear circuit, so that changes in the amount of irradiated light can be controlled. It is characterized in that the level ratio of the RSGSB frame sequential color signal is made almost equal regardless of the color signal.

[Effect]

According to the present invention, R sequentially output from the solid-state image sensor,
One or two specific colors are selected from the G and B field sequential color signals. When a frame sequential color signal of the selected color is output, the frame sequential color signal is passed through a predetermined non-linear circuit, and a frame sequential color signal of RSG and B is generated regardless of changes in the amount of irradiated light. The level ratios are kept almost equal. This improves the reproducibility of the colors of the subject and improves the image quality.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of an electronic endoscope device according to the present invention, in which light from an illumination lamp 10 is transmitted through a near-infrared removal filter 11, an aperture 12, a lens 13, a color filter disk 14, and a light guide. A subject 18 is illuminated from the distal end of the endoscope via the endoscope 16 . That is, the color filter disk 14 has a red filter, a green filter, and a blue filter, each having a central angle of 120@, and is rotated by a motor 20 at a predetermined rotational speed (for example, 2 Qrps).

Thereby, the light from the illumination lamp 10 passes through the rotating color filter disk 14, and the illumination light of each color of red (R), green (G), and blue (B) changes sequentially at a cycle of 1/60 seconds. and is applied to the subject 18 via the light guide 16. Note that the aperture 12 is controlled by an automatic light amount control circuit 15 so that the average level of a signal output from a white balance adjustment circuit 32, which will be described later, becomes a desired level.

The imaging lens 22 provided at the tip of the endoscope has R, G,
image the subject 18 illuminated by each illumination light of B;
This is imaged on the light receiving section of the CCD 24. The CCD 24 is driven by a CCD drive circuit 31 that outputs a CCD drive signal in synchronization with a timing pulse applied from a synchronization circuit 30. The CCD 24 is driven by a CCD drive circuit 31 that outputs a CCD drive signal in synchronization with a timing pulse applied from a synchronization circuit 30. 26
The signal is output to the knee circuit 28 via.

The knee circuit 28 selects only the B plane sequential color signal,
The selected signal is at a predetermined knee point.
When the knee circuit 28 is exceeded, the human input signal is compressed and output. FIG. 2 is a circuit diagram showing an example of the knee circuit 28.

As shown in the figure, this knee circuit 28 mainly includes emitter ho'7 Tri, Tr2, Tr3, resistor R1, variable resistor R1, diode D1, switch SW and switch U,
-M V, etc. The switch SW is turned ON only when the B enable signal B0 is applied from the synchronization circuit 30, and the knee point voltage level V of the emitter follower Tr and the polyneem V can be set.

In the knee circuit 28 having the above configuration, the RlG frame-sequential color signal is outputted via the emitter follower Tri 5Tr2. On the other hand, the B plane sequential color signal is output via the emitter followers Tr1 and Tr2, and when the signal level exceeds the knee point level V2 by turning on the switch SW, a part of the signal is transferred to the variable resistor. R
1. Flows to the emitter of the emitter follower Tr3 via the diode D1 switch SW.

That is, as shown in FIG. 3, the screen sequential color signal of B is
Knee point level V. Until then, voltage is applied to diode D with the opposite polarity, and the output has the same human output characteristics as other colors, but when the knee point level V6 is exceeded, the polarity of diode D changes to the forward direction and is compressed to a predetermined slope. Output.

Note that the level Vi of the knee point can be adjusted by the polyneem V, and the inclination of the slope can be adjusted by the resistance value of the variable resistor R1.

By outputting R, G, and B color signals sequentially through the knee circuit 28, the RSG signal shown in FIG.
The curve of the signal B is made to match the curve of the signal B.

Next, in FIG. 1, the R, G, and B sequential color signals outputted from the knee circuit 28 are applied to a white balance adjustment circuit 32. White balance adjustment circuit 3
Reference numeral 2 amplifies R, G, 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.

RSGS output from the white balance adjustment circuit 32
The B frame-sequential color signal is subjected to gamma correction in the gamma correction circuit 34, and then converted into a digital signal by the A/D converter 36 and added to the field memories 40, 42, and 44.

Field memories 40, 42, and 44 are R, G.

It is for converting the B frame-sequential color signal into a simultaneous color signal, and is driven and controlled by the memory control circuit 38. That is, the memory control circuit 38 is connected to the R
Enable signal REHS synchronized with each illumination light of ,G,B
GEN% GEM is operated manually, and in order to store the color signal corresponding to each illumination light in the field memory corresponding to that color, write signals are sequentially output to each field memory 40, 42, 44, and the field memory is stored. Update the contents. These field memories 40.42.4
The color signals stored in 4 are simultaneously read out and output via D/A converters 50, 52, and 54, respectively.

Then, R, G, which has been converted into a simultaneous equation as described above,
The B simultaneous color signal is converted into a composite color video signal via a color encoder 56, and is added to a color TV and reproduced as a color image.

In the above embodiment, the conventional electronic endoscope apparatus is provided with a separate knee circuit 28 that applies only the knee to the B plane sequential color signal. Functions equivalent to those of 28 may be added.

FIG. 4 is a circuit diagram showing an embodiment of a gamma correction circuit including the above-mentioned functions according to the present invention. As shown in the figure, this gamma correction circuit performs gamma correction by polygonal line approximation using a plurality of dyes D1 to D3, and a variable resistor R2' and a switch SW+ are provided in parallel with the resistor R2. A variable resistor R3' and a switch SW2 are provided in parallel with R3. In addition, these switches SW
1, SW2 is turned ON only when the B enable signal BtN is applied.

When the gamma correction circuit receives an RSGO plane sequential color signal, it performs a predetermined gamma correction and outputs it, as shown by the solid line in FIG. On the other hand, when inputting the screen sequential color signal of B, the switches sw, , SW2 are set to O.
When the output voltage becomes N and the output voltage is in the range of E2 to E, the variable resistor R2/ is connected in parallel, and when it is E3 or more, the variable resistors R, / and R3/ are connected in parallel. It is compressed as shown by the chain line. The degree of compression is set so that the curve of the B signal almost matches the curve of the RSG signal shown in FIG.

In this embodiment, only the B frame-sequential color signal is passed through the nonlinear circuit so that the R, G, and B signal level ratios are approximately equal regardless of changes in illuminance; however, the present invention is not limited to this. The RSG
, B may be kept constant.

〔Effect of the invention〕

As explained above, according to the electronic endoscope device according to the present invention, the level ratio of the RSGSB frame-sequential color signal can always be kept almost constant regardless of the change in the amount of irradiated light, so that color images can be imaged. It has good color reproducibility and can improve image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an electronic endoscope device according to the present invention, FIG. 2 is a circuit diagram showing details of the knee circuit in FIG. 1, and FIG. 3 is a circuit diagram explaining FIG. 2. Figure 4 is a circuit diagram of a gamma correction circuit to which the present invention is applied; Figure 5 is a graph used to explain Figure 4; Figure 6 is a diagram of a conventional electronic endoscope device. This is a graph used to explain the problem. 10... Illumination lamp, 14... Color filter disk, 24... Solid-state imaging device (CCD), 28.
・Knee circuit, 32... White balance adjustment circuit, 34... Gamma correction circuit, 40.42.44.
...Field memo IJ, R1, R2, R3...Variable resistor, DSDl, D2, D3...Diode, SW
S SW, , SW2...Switch.

Claims (4)

[Claims] (1) A subject is irradiated with time-series color-separated light from the end of the endoscope, and the reflected image from the subject is received by a solid-state image sensor installed at the end of the endoscope. R,G
, B, and converts the field sequential color signal into a simultaneous color signal through a memory means to obtain a color video signal, comprising: By selecting one or two colors from the field-sequential color signals of , and outputting the field-sequential color signals of the selected colors through a nonlinear circuit, R, G, and B can be displayed regardless of changes in the amount of irradiated light. An electronic endoscope device characterized in that the level ratios of the frame sequential color signals are made almost equal. (2) Claim (1) wherein the non-linear circuit is a knee circuit.
The electronic endoscope device described. (3) The electronic endoscope device includes a white balance adjustment circuit that controls the gains of the R, G, and B field sequential color signals, and performs gamma correction on the R, G, and B field sequential color signals. The electronic endoscope device according to claim 2, further comprising a gamma correction circuit. (4) The electronic endoscope apparatus according to claim 1, wherein the nonlinear circuit is incorporated into a gamma correction circuit that performs gamma correction on R, G, and B sequential color signals.