JP2988666B2 - Color enhancement processing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color enhancement processing circuit that suppresses enhancement near a color enhancement reference value.

[Related Art] In recent years, by inserting an elongated insertion part, it is not necessary to make an incision, and it is possible to diagnose an affected part in a body cavity or to perform a treatment by inserting a processing tool as necessary. Endoscopes are widely used.

The endoscope forms an image of a target site such as a diseased part by an imaging lens disposed on the distal end side of the insertion portion, and the formed optical image is at hand by an optical image transmission means such as a fiber bundle. Side, and can be magnified with an eyepiece lens system.

By the way, even in an endoscope, an optical image is formed on an imaging surface of a solid-state imaging device such as a CCD by an imaging lens without using the above-described optical image transmission means, and the electric image converted by the solid-state imaging device is photoelectrically converted. An electronic endoscope (hereinafter, referred to as an electronic scope) that displays various image signals on a monitor screen is easy to record and reproduce images, and is in a state of being widely used in the future.

Also in this electronic scope, an image of an affected part in a body cavity or the like is represented by a vector sum with a color vector Ai in which each pixel changes in a hue plane defined by a luminance signal vector Y as shown in a conceptual diagram of FIG. If expressed, the color vector Ai (i = 1, 2, 3,...) Of most pixels is concentrated near the red color vector _R0 .

If the color vector Ai is concentrated in the vicinity of red, it is difficult to distinguish, for example, a normal pink mucous membrane from a hyperemic ulcer from the display image by the electronic scope. For this reason, in the conventional electronic scope, it is necessary to pay sufficient attention to a subtle color change in a display image, and there is a problem that a burden on a diagnostician increases. Further, in the initial symptoms, the color change is small and may be overlooked. In particular, it is desired that cancer or the like be easily detected at an early stage.

For this reason, the present applicant has proposed a conventional example in which color enhancement is performed around an average color in Japanese Patent Application Laid-Open No. 62-13091.

[Problems to be Solved by the Invention] In the above-described conventional example, a hue emphasis is applied to a portion where the hue is slightly shifted from the hue of the reference color based on the average color.

Therefore, the hue enhancement is almost applied to the vicinity of the part selected as the reference color, and the hue enhancement is not applied to only the very narrow part of the reference color. I don't know why.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a color emphasis processing circuit that can identify a color used as a reference for emphasis processing even when color emphasis is performed.

Means and Action for Solving the Problems The present invention relates to a color enhancement processing circuit for performing color enhancement processing of an image signal obtained by capturing an image of a subject, and a reference color to be subjected to the color enhancement processing and a color in the vicinity thereof. And first emphasis processing data that performs non-emphasis processing on a color signal representing the color signal, and second emphasis processing data that performs enhancement processing on a color signal representing a color excluding the reference color and its neighboring colors. Enhancement processing data storage means for storing enhancement processing data; color signal separation means for separating the image signal into color signals; and color signals separated by the color signal separation means and stored in the enhancement processing data storage means. Enhancement processing means for enhancing the color signal based on the enhancement processing data, and video signal generation means for generating a video signal that can be displayed on the display means based on the color signal enhanced by the enhancement processing means, It is characterized by having.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to the drawings.

1 to 9 relate to a first embodiment of the present invention. FIG. 1 is a block diagram showing a configuration of a function converter according to the first embodiment. FIG. 2 is a color enhancement processing circuit according to the first embodiment. FIG. 3 is a block diagram of an electronic endoscope apparatus having the first embodiment, FIG. 4 is an explanatory diagram of operation of each part of a color enhancement processing circuit, and FIG. 5 is an operation of a window comparator. Explanatory diagram,
FIG. 6 is a characteristic diagram showing the input / output characteristics of the function converter, FIG. 7 is an explanatory diagram showing the color enhancement function, FIG. 8 is a characteristic diagram showing the input / output characteristics of the function converter of FIG. FIG. 9 is an explanatory diagram showing that hue enhancement is not performed in the vicinity of the reference hue.

As shown in FIG. 3, an electronic endoscope apparatus 1 having the first embodiment includes an electronic endoscope (electronic scope) 2, a signal processing circuit 3 for performing signal processing of the electronic scope 2, and the electronic endoscope. It comprises a light source device 4 for supplying illumination light to the scope 2 and a color monitor 5 for displaying video signals output from the signal processing circuit 3 in color.

The electronic scope 2 is provided with an imaging lens 8 on the distal end side of an elongated insertion portion 7 that can be inserted into a body cavity or the like, and a CCD 9 as a solid-state imaging device is provided on a focal plane of the imaging lens 8.
And an imaging means is formed. In addition, the insertion portion 7
A light guide fiber 11 is inserted through the light guide fiber 11 to transmit the illumination light of the external light source device 4.
Then, the illumination light can be radiated to the object side through.

The light source device 4 converts the illumination light of the light source lamp 13 into a concave mirror 14.
The reflected light is condensed and radiated through the condenser lens 15 to the incident end of the light guide cable through which the light guide fiber is inserted. When this light is focused,
A three-primary-color transmission filter is provided around a rotation axis and passes through a rotation filter 17 that is driven to rotate by a motor 16.
Illuminated with primary color illumination light. Therefore, the object is sequentially illuminated with the illumination light of each of the three primary colors.

By the way, the pixel signal of the optical image photoelectrically converted by the CCD 9 is amplified by a preamplifier 21 having a low noise figure, transmitted by a signal cable, converted into digital signal data by an A / D converter 22, and then passed through a multiplexer 23. One frame under illumination of each color is sequentially recorded in the frame memories 24R, 24G, and 24B. These frame memories 24R,
The signals recorded by 24G and 24B are read out at the same time, converted into analog color signals R, G and B by a D / A converter 25, respectively, and further passed through a matrix circuit 26 to a luminance signal Y and two color difference signals R-G. Y, BY are extracted.

The luminance signal Y and the color difference signals RY and BY are input to the color enhancement processing circuit 31 of the first embodiment. The hue and saturation of the desired hue are enhanced by the color enhancement processing circuit 31, and the luminance signal Y and the two color difference signals (R-
Y) ", (BY)" are output.

The luminance signal Y and the color difference signals (RY) ", (B-
Y) "is input to the NTSC encoder 32, converted into a composite video signal, and displayed on the color monitor 5 in color.

By the way, the signal R-
Y and BY are input to the quadrature modulation circuit 33 as shown in FIG.

The color difference signals RY, B-
Y is multiplied by signals of sin θ and cos θ by multipliers 34 and 35, respectively, added by an adder 36, and output as a quadrature phase modulation signal A (φ _A ). In this case, sinθ, cosθ
It is convenient to use the 3.58 MHz signal used in the NTSC encoder 32 because the existing circuit can be diverted, and the output signal A (φ _A ) of the adder 36 is sin as shown in FIG.
As shown in FIG. Becomes Note that this phase angle is φ _A = tan ⁻¹ (RY) /
(BY).

On the other hand, the emphasis color designating circuit 37 is constituted by a phase shift circuit 38, and outputs a hue signal M (φ _M ) to be emphasized. This output waveform is shown in FIG.

The output signal A of the quadrature modulation circuit 33 and the output signal M of the phase shifter 38 are compared with a comparator 4 forming a hue difference detection circuit 39.
Signals 1 and 42 are input, and a signal compared with the 0 potential is output. The output signal A is applied to the non-inverting input terminal of the comparator 41, and outputs a signal having a waveform as shown in FIG. 4D. The output signal M of the phase shifter 38 is applied to the inverting input terminal of the comparator 42. And outputs the waveform shown in FIG. 4 (c). The reason for using the inverted output in the comparator 42 is to obtain the hue difference from -180 ° to 180 °.

The output of the comparator 42 is applied to the set terminal of the flip-flop 43 and makes the output of the flip-flop 43 high when the signal rises. The output of the comparator 41 is applied to the reset terminal of the flip-flop 43, and makes the output of the flip-flop 43 low when the signal rises. The output of the flip-flop 43 is phi _A as shown in FIG. 4 (f) - has a square wave having a pulse width corresponding to (phi _M -180 °), at slice circuit 44,
By passing the subsequent low-pass filter 45 is sliced into a predetermined amplitude, pulse width phi _A - is converted into a voltage signal proportional to (phi _M -180 °). The reason why the slice circuit 44 slices at a constant amplitude is that the slice circuit 44 can be constituted by a differential amplifier, and a circuit stable in temperature can be obtained. The output of the low pass filter 45 is the way, φ _A - (φ _M -180 °) = φ _A -φ _M
+180 DC voltage E fraction by calculator 36 from a ° corresponds to 180 ° component is subtracted, the voltage corresponding to φ _A -φ _M. The output of the subtractor 46 is supplied to a window comparator 47.
And the processing shown in FIG. 5 is performed.

That is, the output φ of the low-pass filter 45 through the subtractor 46
To _A -.phi _M, it is set to 0 level near to indicate levels compared to FIG. 5 (a), in the range phi _A -.phi _M
Is present, the window comparator 47 outputs a pulse as shown in FIG. This pulse is multiplied by a luminance signal passed through a function converter 49 having input / output characteristics shown in FIG. 6 by a multiplier 48, and then divided by a variable resistor 50 in series with the voltage V.

The signal divided by the variable resistor 50 is added to the DC voltage Vr by an adder 51 to form a signal for setting a value for performing the saturation enhancement, thereby forming a saturation enhancement circuit 52.
It is input to 54,54.

The reason why the luminance signal is multiplied by the output of the window comparator 47 will be described below. Red, which is the hue at which the endoscope image is most concentrated, is a color with low luminance. The relationship between the luminance and the hue where the luminance is low is as shown in FIG. 7, and the saturation corresponds to the value B in the radial direction. If the saturation of red with low luminance is enhanced and the saturation of red is saturated, the saturation becomes too conspicuous, making it difficult to see the difference in structural change due to the difference in luminance. The saturation saturation is determined by the luminance shown in FIG. 7 and the distance in the normal direction to the luminance, and the distance in the normal direction corresponds to B or B 'in the figure. The values of B and B 'are different depending on the luminance. That is, in a portion where the luminance is low, the value at which the luminance and the normal direction are saturated also increases. By multiplying the saturation enhancement signal by the luminance component, the saturation enhancement amount at low luminance is reduced, thereby reducing saturation of the saturation. Further, the effect is enhanced by appropriately selecting the gamma characteristic of the luminance to be multiplied by the function converter 49.

The output of the subtractor 46 is input to a function converter 61 forming the hue enhancement circuit 60.

 FIG. 1 shows the configuration of the function converter 61.

That is, the input signal is converted into, for example, an 8-bit digital signal by the A / D converter 62 and applied to the address end of the ROM 63. For example, at the address end of the upper 5 bits of the ROM 63, the 5
A bit conversion curve selection signal is applied. This conversion curve selection circuit 64 is provided with a switch SI (I = 1, 2,... 5).
Is grounded, and the other end is connected to a high-level power supply terminal Vcc via a resistor R.

In the ROM 63, in response to an input signal applied to the address end, function data of an input / output characteristic for outputting an output signal shown in FIG. 8 is written. By selecting ON and OFF, a curve of the input / output characteristics can be selected, for example, as shown in FIGS. 8 (a) and 8 (b).

That is, the output level is constant within the range D near the input level of the reference hue M so that hue emphasis is not applied. If the value deviates from this range D, hue emphasis is applied. It is to be done. This curve and the value of the range D can be changed, for example, in ²⁵ ways by selecting ON and OFF of the switch SI.
FIG. 8 shows the two cases.

The digital data read from the ROM 63 is converted into an analog signal by the D / A converter 65. The A / D converter 62 and the D / A converter 65 are supplied with a conversion clock from a clock generation circuit 66.

The output signal of the function converter 61 has a phase difference of -180 °, 0 °, +180 at a pulse width modulation circuit (PWM) 67 shown in FIG.
The feature of the first embodiment is that the pulse width is not changed at the time of ゜ and the pulse width is not changed even when the phase difference is between 0 ° and ± α °.

In the pulse width modulation circuit 67, the sine wave is made a rectangular wave to be a reference wave, and the pulse width of the wave is changed by an input signal. The output of the pulse width modulation circuit 67 is input to a monostable multivibrator (MMB) 68a and is converted into a thin strobe pulse for sample and hold (see FIG. 9). In parallel with this, the output of the pulse width modulation circuit 67 receives a delay corresponding to a phase angle of 90 ° on a delay line 69, and similarly outputs the monostable multivibrator 68a by a monostable multivibrator 68b. The output is converted into a thin strobe pulse 90 ° out of phase. These pulses are input to sample and hold circuits 70 and 71, respectively, and sample and hold the output of the quadrature modulation circuit 33. The outputs of the sample and hold circuits 70 and 71 are input to sample and hold circuits 72 and 73, respectively, in order to make the sampling period constant, and sample and hold are performed again.

The sample pulses of the sample and hold circuits 72 and 73 are generated by a monostable multivibrator 74 that outputs a pulse having a constant phase from a sine wave. The pulse width modulation circuit 67 is reset by a reset pulse at an angle of 0 °.

By the above operation, color difference signals (RY) 'and (BY)' in which hue enhancement is applied to the RY and BY signals are obtained.

Thus, the multiplier 5 forming the saturation enhancement circuit 52
The color difference signal (R-
Y) ", (BY)" are output.

According to the first embodiment, the hue around the reference hue M set by the emphasis color designation circuit 37 can be emphasized, and hue enhancement is not performed for the hue range D near the reference hue M. This prevents the reference hue from being lost due to the emphasis.

That is, when the reference hue M is designated as shown in FIG. 9, in this reference hue M and its vicinity A1, A1 ',
As shown on the right side, the strobe pulse sampled and held by the sample and hold circuit 70 (or 71) through the pulse width modulation circuit 67 has a fixed timing, and the hue is not emphasized. This reference hue M and its hues A1, A
In the hues A2 and A2 'deviated from 1', the timing of the strobe pulse to be sampled and held is shifted and the hue is enhanced.

The user can select a desired hue enhancement characteristic curve or range D by using the conversion curve selection circuit 64. Note that a coring circuit may be used to suppress color enhancement near the reference hue.

FIG. 10 is an electronic endoscope apparatus having a second embodiment of the present invention.
81 is shown.

An objective lens 83 is provided at the tip of the electronic scope 82,
At the focal plane of the objective lens 83, a CCD 84 is provided. The signal from the CCD 84 is input to the TV circuit 85, where a color video signal is generated and input to the encoder 86.
The encoder 86 converts the signals into R, G, B signals, and outputs the signals to the A / D converter 87. The A / D converter 87 converts the signals into digital R, G, B signals.

The digital R, G, and B signals are for R, G, and R image memories.
8R, 88G and 88B are input and temporarily stored. The digital R, G, and B signals read from the image memories 88R, 88G, and 88B are converted into analog R, G, and B signals by a D / A converter 89, and displayed in color on a color monitor 90. The digital R, G, B signals are input to a conversion circuit 91, which converts these three attributes of color, hue (H), saturation (S), and brightness (V).
, And input to the image memories 93H, 93S, 93V for hue, saturation, and lightness which form the image enhancement circuit 92.

The image enhancement circuit 92 includes the image memories 93H, 93S, 93V
, A saturation emphasizing circuit 94, and a control console 95.

The control console 95 is provided in, for example, an operation unit of the electronic scope 82, and outputs a conversion command to the conversion circuit 91 based on a user's input, and outputs a command for enhancement processing to the saturation enhancement circuit 94.

The image memories 93H, 93S, and 93V store the H, S, and V images converted by the conversion circuit 91, respectively.
The image with the saturation emphasized in step 4 is stored.

The H, S, and V images read from the image memories 93H, 93S, and 93V are input to an inverse conversion circuit 96, which converts them into R ', G', and B 'color signals, and outputs the image signals 97R, 97G, and 97B. To be stored temporarily. The three primary color signals read from the image memories 97R, 97G, and 97B, that is, the R ', G', and B 'signals in which the saturation is emphasized, are converted into analog signals by the D / A converter 98, and then are converted to a color monitor. 99
Is displayed in color.

Incidentally, the configuration of the saturation emphasizing circuit 94 is shown in FIG.

The input signal is input to the variable gain amplifier 101 and the integration circuit 102. Variable gain amplifier according to the signal level corresponding to the saturation of the previous screen integrated by this integration circuit 102
The gain of 101 is variably controlled.

The output signal of this variable gain amplifier 101 is an A / D converter
The image data is input to a look-up table 104 composed of a ROM or the like via a 103, and the input saturation is output with an enhanced saturation. This look-up table 104 shows the input / output characteristics of the conversion curve as shown in FIG. 12 (a), and in the vicinity D of the reference color saturation, the inclination becomes 45 ° so that the saturation is not enhanced. . The conversion curve of this look-up table 104 can be selected by the console 95. The output of the table 104 is output via the D / A converter 105.

Therefore, for example, when there is an input signal as shown in FIG. 12 (b), the output of the portion D near the reference color saturation changes as shown by the solid line in FIG. 12 (c). Output without In a portion deviating from the portion D, saturation enhancement is applied, and the waveform becomes elongated as shown by a broken line.

Also in this embodiment, since saturation is not emphasized near the reference value when performing saturation enhancement, it is possible to prevent the reference value from being lost.

The present invention is not limited to the above-described embodiment, and can be applied to a case where only the hue is emphasized. When the hue and the saturation are enhanced as in the first embodiment, the saturation can be prevented from being applied near the reference value (the input / output characteristics in FIG. 7 may be changed).

Further, the hue, the saturation, and the like may be reduced in the vicinity of the reference value with the emphasis amount suppressed.

[Effects of the Invention] As described above, according to the present invention, the amount of enhancement is suppressed in the vicinity of the reference value when color enhancement is performed. It can be prevented from being lost.

[Brief description of the drawings]

FIGS. 1 to 9 relate to a first embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of a function converter according to the first embodiment, FIG. 2 is a block diagram showing the configuration of a color enhancement processing circuit according to the first embodiment, and FIG. FIG. 4 is a diagram illustrating the operation of each part of the color enhancement processing circuit, FIG. 5 is a diagram illustrating the operation of a window comparator, FIG. 6 is a characteristic diagram illustrating input / output characteristics of a function converter, FIG. FIG. 7 is an explanatory diagram showing a function of color enhancement, FIG. 8 is a characteristic diagram showing input / output characteristics of the function converter of FIG. 1, FIG. 9 is an explanatory diagram showing that hue enhancement is not performed near a reference hue, FIG. 10 is a configuration diagram of an endoscope apparatus having a second embodiment of the present invention,
FIG. 11 is a block diagram showing the configuration of a saturation emphasizing circuit of the second embodiment, FIG. 12 is an explanatory diagram of the operation of the second embodiment, and FIG. DESCRIPTION OF SYMBOLS 1 ... Electronic endoscope apparatus, 2 ... Electronic scope 3 ... Signal processing circuit, 4 ... Light source apparatus 5 ... Color monitor, 31 ... Color enhancement processing circuit 61 ... Function converter, 63 ... ROM 64 Conversion circuit selection circuit

Claims (1)

(57) [Claims] 1. A color enhancement processing circuit for performing color enhancement processing on an image signal obtained by imaging a subject image, wherein a color signal representing a reference color to be subjected to the color enhancement processing and a color signal representing a color adjacent thereto are not enhanced. First emphasis processing data to be processed,
And enhancement processing data storage means for storing enhancement processing data including second enhancement processing data for performing enhancement processing on a color signal excluding the reference color and a color other than the reference color, and a color signal A color signal separating unit that separates the color signal into a plurality of color signals; an enhancement processing unit that enhances the color signal based on the color signal separated by the color signal separation unit and the enhancement processing data stored in the enhancement processing data storage unit; A video signal generating means for generating a video signal that can be displayed on the display means based on the color signal emphasized by the processing means.