JP2884587B2 - Electronic endoscope device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic endoscope apparatus, and more particularly, to an electronic endoscope apparatus that performs image capturing in a frame sequential method.

[Prior art] An electronic endoscope device used for medical or industrial use uses a single solid-state imaging device (hereinafter referred to as a CCD) to reduce the diameter of an endoscope body (electronic scope). The insertion part of the scope is inserted into the inside of the human body, etc., and red, green, and blue illumination light are sequentially emitted from the illumination device built into the processor toward the observation target portion, and the reflected image from the observation target portion is subjected to CCD. The photoelectric conversion is performed to obtain an R, G, B plane sequential color signal.

The frame-sequential color signal is transmitted to a processor, subjected to signal processing such as simultaneous conversion in the processor, and then applied to a display device. The image of the observation target portion is displayed on the display device in color. Is done.

[Problems to be solved by the invention]

Generally, when a white subject is imaged, it is preferable that the R, G, and B plane-sequential color signals sequentially output from the CCD have substantially the same level in order to faithfully reproduce colors. The long wavelength sensitivity in the infrared region tends to be high, and the short wavelength sensitivity to blue light tends to be low. Also, CCD
Since the γ characteristics of the photoelectric conversion for the R, G, and B light are different, the level ratio of the CCD output signals of R, G, and B changes depending on the intensity of the irradiation light, and the color balance is broken.

In particular, among the signal level ratios, the change of the B signal is remarkable. As shown in FIG. 6, when the illuminance is small, the B signal is smaller than the other R and G signals, and when the illuminance is large,
It tends to be larger than the R and G signals.

If the color balance is lost, the color is not faithfully reproduced when the observation target portion is displayed on the display device, and the image quality is degraded.

The present invention has been made in view of such circumstances, and can always keep the level ratio of the R, G, and B plane-sequential color signals substantially constant regardless of the change in the amount of irradiation light. It is an object of the present invention to provide an electronic endoscope apparatus which has good color reproducibility and can improve image quality.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a solid-state imaging device in which light subjected to color separation in a time series from a distal end portion of an endoscope is applied to a subject, and a reflected image from the subject is disposed at the distal end portion of the endoscope. Receiving light, obtaining R, G, B plane-sequential color signals from the solid-state imaging device; converting the plane-sequential color signals into simultaneous color signals via a memory means to obtain a color video signal; An endoscope apparatus, comprising: a white balance adjustment circuit for controlling the gains of the R, G, B plane-sequential color signals, and a gamma correction circuit for performing gamma correction on the R, G, B plane-sequential color signals. In the electronic endoscope apparatus having the above, one of the R, G, B plane-sequential color signals
A color or two colors are selected, and a plane-sequential color signal of the selected color is a level before the saturation level is reached, and R, G, and B planes obtained when imaging by changing the amount of irradiation light. When the level ratio of the color signal sequentially exceeds a predetermined level that deviates first, a non-linear circuit for compressing and outputting a signal exceeding the predetermined input level is provided, and is acquired when imaging by changing the amount of irradiation light. It is characterized in that the level ratio of the R, G, B plane sequential color signal is made substantially equal over the entire input level.

[Action]

According to the present invention, one or two specific colors are selected from the R, G, and B plane sequential color signals sequentially output from the solid-state imaging device. Then, when the plane-sequential color signal of the selected color is output, the plane-sequential color signal is passed through a predetermined non-linear circuit, and the R, G, B plane-sequential is output regardless of the change in the amount of irradiation light. The level ratios of the color signals are made substantially equal. As a result, the color reproducibility of the subject is improved, and the image quality is improved.

〔Example〕

Hereinafter, preferred embodiments of an electronic endoscope apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of an electronic endoscope apparatus according to the present invention. Light from an illumination lamp 10 is a near-infrared elimination filter 11, an aperture 12, a lens 13, a color filter disk 14, and a light guide. The subject 18 is illuminated from the distal end portion of the endoscope via 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 a predetermined rotation speed (for example,
20 rps). As a result, 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) sequentially changes at a period of 1/60 second. Become a light guide
It is added to the subject 18 via 16. The aperture 12 is controlled by the automatic light amount control circuit 15 so that the average level of a signal output from a white balance adjustment circuit 32 described later becomes a desired level.

The imaging lens 22 provided at the end of the endoscope includes R, G,
An image of the subject 18 illuminated by each of the illumination lights B is taken, and the image is formed on the light receiving section of the CCD 24. The CCD 24 is driven by a CCD drive circuit 31 which outputs a CCD drive signal in synchronization with a timing pulse applied from a synchronization circuit 30, and outputs R, G, B plane-sequential color signals corresponding to R, G, B illumination light. Is output to the knee circuit 28 via the low-pass filter 25 and the amplifier 26.

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

As shown in the drawing, the knee circuit 28 mainly includes emitter followers Tr1, Tr2, Tr3, a resistor R, a variable resistor R1, a diode D1, a switch SW, a volume V, and the like. Switch SW is turned ON only when the synchronizing circuit 30 is applied the enable signal B _EN of B, also the emitter follower Tr and volume V is adapted to set the voltage level V _E of the knee point.

In the knee circuit 28 having the above structure, the R and G plane-sequential color signals are output through the emitter followers Tr1 and Tr2.
On the other hand, the plane-sequential color signal of B is represented by emitter followers Tr1 and T1.
is outputted through the r2, when the signal level by the switch SW is turned ON exceeds the level V _E of the knee point, a part of the signal is a variable resistor R1, a diode D, an emitter follower Tr3 via the switch SW To the emitter.

That is, as shown in FIG. 3, the field sequential color signal of B is up to the level V _E of the knee point, but the voltage in the opposite polarity applied is output at the same output characteristics as the other colors in the diode D,
Exceeding the level V _E of the knee point, the polarity of the diode D is outputted after being compressed to a predetermined slope becomes forward.
The level V _E of the knee point can be adjusted by the volume V, the slope of the slope can be adjusted by the resistance value of the variable resistor R1.

Then, by outputting the R, G, and B plane-sequential color signals through the knee circuit 28, the R, G, and R signals shown in FIG.
The curve of the signal B is matched with the curve of the signal B.

Next, in FIG. 1, the R, G, B frame sequential color signals output from the knee circuit 28 are applied to a white balance adjustment circuit 32. White balance adjustment circuit 32
Amplifies R, G, and B plane-sequential color signals with predetermined gains, respectively. In particular, the gain for the R and B signals can be adjusted. The gains for the R and B signals are adjusted so that a white reproduced image is obtained, for example, when a white image is captured in advance.

R, G, output from the white balance adjustment circuit 32,
The B-sequential color signal is gamma-corrected by a gamma correction circuit 34, converted to a digital signal by an A / D converter 36, and applied to field memories 40, 42, and 44.

The field memories 40, 42, and 44 are for converting R, G, and B frame sequential color signals into simultaneous color signals.
The drive is controlled by the memory control circuit 38. That is, the memory control circuit 38 receives the enable signals R _EN , G _EN , and G _EN synchronized with the respective illumination lights of R, G, and B from the synchronization circuit 30, and outputs the color signals corresponding to the respective illumination lights. A write signal is sequentially output to each of the field memories 40, 42, and 44 so as to be stored in the field memories corresponding to the colors, and the storage contents of the field memories are updated. The color signals stored in these field memories 40, 42, 44 are simultaneously read out and output via D / A converters 50, 52, 54, respectively. Then, R converted into a simultaneous expression as described above,
The simultaneous color signals of G and B are converted into a composite color video signal via a color encoder 56, applied to a color TV, and reproduced as a color image.

In the above-described embodiment, the conventional electronic endoscope apparatus is provided with a knee circuit 28 for applying only the color-sequential color signal of B separately. However, instead of the knee circuit 28, the gamma correction circuit is provided with a knee circuit. A function equivalent to 28 may be added.

FIG. 4 is a circuit diagram showing an embodiment of a gamma correction circuit including the above function according to the present invention. As shown in the figure, the gamma correction circuit, a polygonal line approximation using a plurality of Daidodo D ₁ to D _3, which performs gamma correction, the resistance R ₂
A variable resistor R ₂ ′ and a switch SW ₁ are provided in parallel with the resistor R _3, and a variable resistor R ₃ ′ and a switch SW ₂ are provided in parallel with the resistor R ₃ . These switches SW ₁ and SW ₂ are turned ON only when the B enable signal _BEN is applied.

When the R and G plane-sequential color signals are input, the gamma correction circuit performs predetermined gamma correction and outputs the signals as shown by the solid line in FIG. On the other hand, when the B-sequential color signal is input, the switches SW ₁ and SW ₂ are turned on, and when the output voltage is in the range of E _{2 to} E ₃ , the variable resistor R ₂ ′ is connected in parallel and E ₃ In the above case, since the variable resistors R ₂ ′ and R ₃ ′ are connected in parallel, they are compressed as shown by the dashed line in FIG. The degree of the compression is set so that the curve of the B signal substantially matches the curve of the R and G signals shown in FIG.

In this embodiment, only the B-sequential color signal is passed through the non-linear circuit so that the signal level ratios of R, G, and B are substantially equal regardless of the change in illuminance. By selecting two colors from among the R, G, and B plane-sequential color signals, and outputting a color signal of the selected color through a non-linear circuit corresponding to the color,
The G and B signal level ratios may be kept constant.

〔The invention's effect〕

As described above, according to the electronic endoscope apparatus according to the present invention, R, G, and B are always present regardless of the change in the amount of irradiation light.
Since the level ratio of the frame-sequential color signal can be kept substantially constant, the color reproducibility of a color image can be improved and the image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an electronic endoscope apparatus according to the present invention, FIG. 2 is a circuit diagram showing details of a knee circuit of FIG. 1, and FIG. 3 is for explaining FIG. Graph used for
FIG. 4 is a circuit diagram of a gamma correction circuit to which the present invention is applied, FIG. 5 is a graph used for explaining FIG. 4, and FIG. 6 is a diagram for explaining problems of a conventional electronic endoscope apparatus. 7 is a graph used in FIG. 10 illumination lamp, 14 color filter disk, 24 solid-state image sensor (CCD), 28 knee circuit, 32 white balance adjustment circuit, 34 gamma correction circuit, 40, 42, 44 field memory, R1, R ₂ ', R _3' ... variable _{resistor, D, D 1, D 2} , D 3
… Diode, SW, SW ₁ , SW ₂ … Switch.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-155689 (JP, A) JP-A-63-144677 (JP, A) JP-A-61-287393 (JP, A) JP-A-61-287393 258566 (JP, A) Fully open sho 64-25270 (JP, U) Fully open sho 61-195670 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 23/00 A61B 1 / 04 H04N 5/14-5/217

Claims (3)

(57) [Claims] An object is illuminated with light separated in time series from a distal end of an endoscope, and a reflected image from the subject is received by a solid-state imaging device disposed at the distal end of the endoscope. An electronic endoscope apparatus for obtaining R, G, B plane-sequential color signals from the elements, and converting the plane-sequential color signals into simultaneous color signals via a memory means to obtain a color video signal. An electronic endoscope having a white balance adjustment circuit for controlling the gains of the R, G, and B plane-sequential color signals, and a gamma correction circuit for performing gamma correction on the R, G, and B plane-sequential color signals. In the mirror device, one or two colors are selected from the R, G, and B plane-sequential color signals, and the plane-sequential color signal of the selected color is at a level before reaching a saturation level, and R, G acquired when imaging with changing light amount , B, when the level ratio of the color signal sequentially exceeds the predetermined level, a non-linear circuit for compressing and outputting a signal exceeding the predetermined input level is provided. Wherein the level ratio of the R, G, and B plane-sequential color signals obtained in step (b) is made substantially equal over the entire input level. 2. The electronic endoscope apparatus according to claim 1, wherein said non-linear circuit is a knee circuit. 3. The electronic endoscope apparatus according to claim 1, wherein said nonlinear circuit is incorporated in said gamma correction circuit.