JP2746615B2 - Endoscope image processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endoscope image processing apparatus provided with means for decomposing an image into a plurality of color signals and independently varying the output level of the decomposed color signals. .

[Related Art] In recent years, by inserting an elongated insertion portion into a body cavity, it is possible to observe an affected part or the like in the body cavity without performing an incision, and to perform a therapeutic treatment using a treatment tool if necessary. Endoscopes have become widely used.

In addition to optical endoscopes (fiberscopes) that use image guides as image transmission means, recent endoscopes
Electronic endoscopes using solid-state imaging means such as D (hereinafter referred to as electronic endoscopes or electronic scopes) have come into practical use.

There is also a type in which an imaging camera using a solid-state imaging device such as a CCD is connected to an eyepiece of a fiber scope so that color display can be performed on a monitor.

FIG. 19 shows almost the same configuration as the preceding example proposed by the present applicant in Japanese Patent Application No. 61-207432.

The image signal output from the CCD 1 forming the image pickup means is input to the amplifier 2 and amplified in a predetermined range of voltage level. After that, it enters the γ correction circuit 3 and is γ corrected. In the case of the RGB plane sequential system, the signal after the γ correction is converted into a digital quantity by an analog-digital converter (A / D converter) 4 and then passed through a changeover switch 5 to memories 6R, 6G,
Recorded at 6B. The image data recorded in these memories 6R, 6G, and 6B are simultaneously read out by the application of the timing signal output from the control signal generation unit 7, and are respectively read by the D / A
The color signals R, G, and B are converted into analog color signals by the converter 8 and output from the image output terminal 9. The color signals R, G, B output from the image output terminal 9 and the synchronization signal generation circuit 1
The image of the subject is displayed on the display screen of the monitor by the synchro signal output from 0.

On the other hand, the field sequential illumination means for performing the field sequential imaging performs the rotary filter by passing the white light of the white lamp 11 through a rotary filter 13 driven to rotate by a motor 12.
13 color transmission filters 14R, 1 that transmit light of each wavelength of R, G, B
By 4G, 14B, it becomes R, G, B illumination light and light guide 15
Irradiation. Then, the other end of the light guide 15 is sequentially illuminated toward the subject with light of R, G, B wavelengths, and a subject image is formed on the imaging surface of the CCD 1 under this illumination.

In the above prior example, the input / output characteristics are the same for all the R, G, B signals. The effect of such a system on the reproducibility of an endoscopic image will be described below with reference to FIG.

 FIG. 20A shows the distribution of the luminance level of the subject.

In general, the luminance level of a subject in an endoscope is mostly based on a red component, and is less based on a blue component.

FIG. 20 (B) shows a histogram of output values after digital conversion for luminance levels in the range shown in FIG.
This is shown for each of G and B. Since the characteristics at the time of input are determined based on the average luminance level of the subject, the deviation of the luminance level of the subject is output as it is.

As is clear from this, the G signal is output in a normal distribution. However, the R signal tends to saturate at a high level. On the other hand, the B signal is biased to a low level and is easily buried in noise.

[Problems to be Solved by the Invention] As is apparent from FIG. 20, in the prior art, the characteristics at the time of input are adapted to the average luminance level of the subject. For this reason, there is a disadvantage that the R signal is biased toward a high level and the B signal is biased toward a low level. Such drawbacks reduce the amount of useful information that an image has. In addition, since the R signal is biased toward a high level, there is a problem in that a signal of a very small level is masked, making it difficult to identify the signal.

The present invention has been made in view of the above points, and has as its object to provide an endoscope image processing apparatus capable of obtaining an effective amount of information even in a wavelength range that is difficult to use effectively.

[Means for Solving Problems and Action] The present invention stores a first color signal, a second color signal, and a third color signal of a data amount corresponding to an image size of an imaging unit for imaging an endoscope image. Possible memory means and maximum and minimum density levels in the histogram for the histograms of the respective density levels of the first color signal, the second color signal and the third color signal stored in the memory means , The number of levels between the detected maximum value and the minimum value is expanded to a predetermined level number, and the first color signal, the second color signal, and the third
Density tone conversion means for generating a color signal of the first color signal, the second color signal, and the third color signal which have been subjected to the density tone conversion. Flattening processing means for flattening the histogram; and displaying the color information on the display means based on the first color signal, the second color signal, and the third color signal whose histogram has been flattened by the flattening processing means. Signal processing means for generating a signal capable of displaying an endoscope image.

Also, the present invention provides a memory means capable of storing a first color signal, a second color signal, and a third color signal of a data amount corresponding to an image size of an imaging means for imaging an endoscope image;
Average value calculating means for calculating an average value of the density levels in the respective histograms with respect to the histogram relating to the density levels of the first color signal, the second color signal and the third color signal stored in the memory means; ,
A density conversion table calculating means for calculating a density conversion table for the first color signal, the second color signal, and the third color signal having the average value at an inflection point based on the respective average values; Density conversion means for converting the first color signal, the second color signal, and the third color signal based on the respective density conversion tables calculated by the conversion table calculation means; Signal processing means for generating a signal capable of displaying a color endoscopic image on a display means based on the converted first color signal, second color signal, and third color signal. It is assumed that.

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

First, before describing embodiments of the present invention, an endoscope image processing apparatus to which the present invention is applied will be described.

1 to 8 relate to an endoscope image processing apparatus of the present invention, FIG. 1 is a configuration diagram of an endoscope image processing apparatus, FIG. 2 is an overall configuration diagram, and FIG. FIG. 4 is a characteristic diagram showing an example of a calculated histogram, FIG. 5 is a characteristic diagram showing a histogram of an image obtained by performing density conversion from the calculated histogram, and FIG. FIG. 7 is a characteristic diagram showing a histogram of an image obtained by performing density conversion on the density level of a point, FIG. 7 is a flowchart for performing flattening characteristic conversion, and FIG. 8 is a diagram of an image obtained by the processing of FIG. It is a characteristic view showing a histogram.

As shown in FIG. 2, an (endoscope) image processing device 21 is an electronic endoscope in which an elongated insertion portion 23 is inserted into a body cavity of a living body 22.
24, a connector 25A of the universal cord 25 of the electronic endoscope 24 is connected, an observation device 26 having a function of processing a video signal, and a color monitor 27 connected to the observation device 26 and displaying a video signal in color. A suction device 29 connected to the electronic endoscope 24 via a suction cable 28 branched from the connector 25A, and connected to the observation device 26, R, G, B
The image processing apparatus 30 generates a histogram from the color signals and converts or adjusts the gradation characteristics of the density for each color signal.

In the electronic endoscope 24, as shown in FIG. 1, a light guide 31 for transmitting illumination light is inserted into an elongated insertion portion 23, and a rear end of the light guide 31 inserted through the insertion portion 23. The side is further inserted through the universal cord 25 shown in FIG. Thus, illumination light is supplied from the light source unit 32 by connecting the connector 25A to the observation device 26.

That is, the light source unit 32 irradiates the illumination end of the light guide 31 with the white illumination light of the white lamp 33 via the rotary filter 35 driven to rotate by the motor 34. The rotating filters 35 include filters 36R, 36G, and 35 that transmit light of each wavelength of red, green, and blue.
Since B is provided, light of each wavelength of red, green, and blue (that is, illumination light of R, G, and B) is sequentially supplied to the incident end of the light guide 31 by passing through the rotary filter 35. Then, the light is transmitted to the other end by the light guide 31 and R, G,
The illumination light of B is emitted. The subject illuminated with the light of R, G, B is provided by an objective lens 37 disposed in the distal end of the insertion section 23,
An image is formed on the imaging surface of the CCD 38 disposed on the focal plane of the objective lens 37. The CCD 38 outputs an electric signal that has been photoelectrically converted by applying a drive signal from the driver 39. This CC
The image signal output from D38 is input to the amplifier 41,
After being amplified to a predetermined range of electric signals (for example, 0 to 1 volt), the signals are input to an A / D converter 44 forming a signal processing unit 43 in the observation device 26 via a signal cable 42. The digital signal is converted into a quantized digital signal by the A / D converter 44, and is input to the memory unit 46 via the changeover switch 45.

The changeover switch 45 has the same number of changeover contacts as the number of the color transmission filters 35R, 35G, and 35B of the rotary filter 35 (that is, 3 contacts).
), And the contacts are sequentially switched by the switching signal of the control signal generator 47. These contacts are sequentially connected to three memories 46R, 46G, 46B forming a memory section 46, and digital signals are recorded in the memories 46R, 46G, 46B via the turned-on contacts.

The memories 46R, 46G, 46B are connected to the image processing device 30. The image processing device 30 includes a working memory 51, an arithmetic processing device 52, an auxiliary storage device 53, an external output device 54, and an analog switch 50, and these are memories 46R and 46.
G, 46B.

When the image processing is performed by the image processing device 30, the work memory 51 receives necessary signal data from the memories 46R, 46G, and 46B by a control signal that controls a transfer timing from the control signal generation unit 47. Will be transferred. This working memory 51
The signal data transferred to the processing unit 52 is subjected to a process of generating a histogram, a characteristic conversion process of the density distribution in the obtained color signal data, and the like by the arithmetic processing unit 52, and transfers the result to the working memory 51. Further, the signal data subjected to the characteristic conversion processing can be stored in the auxiliary storage device 53 as necessary, and a histogram or the like can be printed out by an external output device 54 such as a print.

When the image processing is not performed, the analog switch 50 is turned on, and the signal data stored in the memories 46R, 46G, 46B is simultaneously output to the D / A converters 55a, 55b, 55c.

The analog color signals converted by the respective D / A converters 55a, 55b, 55c are further gamma-corrected by gamma correction circuits 56a, 56b, 56c, output to the monitor 27 from the output terminal 57, and displayed in color. .

Further, the control signal generator 47 outputs a timing signal to the synchronization signal generation circuit 58, and the synchronization signal generation circuit 58 outputs a SY
Output NC signal.

The control signal generator 47 also outputs a signal for controlling the rotation of the motor 34 that rotates the rotation filter 35. The control signal generator 47 controls the on / off operation of the analog switch 50, sends a timing signal to the processor 52, and sends a signal from the processor 52 to the control signal generator 47. In this way, data can be efficiently transferred.

The operation of the thus configured endoscope image processing apparatus will be described below.

As shown in FIG. 1, the image signal from the CCD 38 is amplified by an amplifier 41 to a voltage in a predetermined range, for example, a voltage from 0 volt to 1 volt. This image signal is digitized by the A / D converter 44 at a certain quantization level (for example, 8 bits). This digital signal is sent to an R signal memory 46R based on a control signal from a control signal generator 47 via a changeover switch 45 when the image signal captured by the CCD 38 is under red (R) illumination. When it is under green (G) illumination, it is stored in the G signal memory 46G, and when it is under blue (B) illumination, it is stored in the B signal memory 46B. The memories 46R, 46G, and 46B have independent inputs and outputs, and can perform input and output at their own timing.

The image signal data stored in each of the memories 46R, 46G, 46B is input to the image processing device 30. In this case, in a mode in which image processing is not performed (for example, the mode can be selected by a selection switch or the like), the image processing apparatus 30 indicates to the control signal generation unit 47 that image processing is not performed. Signal, the analog switch 50 is turned on based on this signal, and the image signal data stored in the memories 46R and 46 are simultaneously input to the D / A converters 55a, 55b and 55c and are converted into analog color signals. . At that time, the gamma correction circuits 56a, 56b,
Converted into color signals R, G, B having predetermined γ characteristics at 56c,
The signal is output to the monitor 27 from the output terminal 57 together with the SYNC signal of the synchronization signal generation circuit 58, and the monitor 27 performs color display.

On the other hand, when the image processing apparatus 30 is set to the image processing mode, a histogram generation process shown in FIG. 3 is performed.

The process of calculating the histogram will be described with reference to FIG.

The calculation of the histogram will be described with reference to FIG. Now, when an image is represented by a two-dimensional array Image (X_size, Y_size), X_size indicates an image size in the X direction, and Y_size indicates an image size in the Y direction. When the histogram is represented by a one-dimensional array Hist (Level), Level means the number of density levels (for example, 256 levels from 0 to 255 if the quantization level is 8 bits).

First, the image Image (X_size, Y_size) to be processed is transferred to the working memory 51, and a memory content for storing the calculated histogram (for example, provided in the working memory 51, this memory content is stored in the Hist (Represented by (Level))
Is initialized (substituted with 0). Further, x is a variable indicating a position in the X direction, and y is a variable indicating a position in the Y direction.
Is prepared as a variable representing the density level of the image,
Each is initialized (0 is substituted).

 Then, the following processing is performed.

(1) Increment y by one.

(2) Initialize x (substitute 0).

(3) x is counted up by one.

(4) The density level of the image Image (x, y) at the position indicated by x and y is substituted for l.

(5) Hist (l) is counted up by one.

(6) If x <X_size, return to (3), otherwise proceed to (7).

(7) If y <Y_size, return to (1); otherwise, end.

Through the processes (1) to (7) above, the one-dimensional array Hi
A histogram is created at st.

FIG. 4 shows an example of a histogram obtained in this manner. The horizontal axis is the density level (0 to 0 in this example).
255), and the vertical axis represents frequency.

Next, from the histogram generated by the above process,
As the histogram conversion, for example, a process of density gradation conversion will be described with reference to FIG.

The steps (1) to (7) are performed in the memories 46R, 46G, 46B.
5 (a), (b),
A histogram as shown in (c) is obtained. These histograms are for a normal endoscopic image, and as can be seen from (a), (b), and (c), the histograms have the permitted number of density levels (the quantization level is 8 bits). Then, only a part of 0 to 255) is distributed. Such images have low contrast and are difficult to distinguish. Now, the quantization level is 8 bits, the maximum density level in the histogram is l max, and the minimum density level is l min
And the original image is represented by Image (x, y). Image Image '(x, y) after performing density gradation conversion F
Is obtained by the following equation.

Image ′ (x, y) = 255 (Image (x, y) −l min) / (l ma
x−l min) (1) where 1 ≦ x ≦ X_size and 1 ≦ y ≦ Y_size.

This allows the usual narrow concentration level range [l min, l ma
x] Image of FIGS. 5 (a), (b) and (c)
(X, y) are the same as in (a '), (b'),
The density level range [l min, l max] as in (c ')
Is expanded and translated so that it is distributed at all density levels [0,255], and the contrast is enhanced.
In addition, wavelength ranges (R, B) that have not been effectively used in the past
Thus, an effective amount of information can be obtained.

FIG. 6 shows an example in which two points l ₁ and l ₂ are designated in place of the above-mentioned density level range [l min, l max] and the specified density level range [l ₁ , l ₂ ] Is obtained by performing the density gradation conversion of the expression (1).

Next, the process of flattening the histogram using the above-described apparatus will be described. This is to convert the histogram so that the height of the histogram is the same at all densities. Assuming now that the quantization level is 8 bits, the number of pixels Dot that one density value should have can be obtained by the following equation.

Dot = (X_sizexY_size) / 256 (2) The cumulative density function CD (i) in the histogram, 0 ≦
i ≦ 255 is obtained by the following equation.

In order to perform the above-mentioned flattening process, the process shown in the flowchart of FIG. 7 is performed.

The image to be processed, Image (X_size, Y_size), is transferred to the working memory, and the converted image Image ′ (X_size, Y_siz
e) Initialize the storage memory. Also, as shown in FIGS. 5 (a), (b) and (c), it is assumed that the histogram of the image exists in Hist (Level). further,
X is prepared as a variable indicating the position in the X direction, y is set as a variable indicating the position in the Y direction, and i1, i2, j1, j2 are prepared as working variables, and each is initialized.

Next, the following switch processes (1) to (7) are performed.

(1) i2 is incremented by one.

(2) If i2> 255, proceed to (7). If i2 ≦ 255, proceed to (3).

(3) Calculate a new density level and substitute it for j2.

(4) If j2-j1 <1, return to (1), otherwise go to (5).

(5) For all x and y satisfying i1 ≦ Image (x, y) <i2, j2-1 is substituted into Image ′ (x, y).

(6) Substitute i2 for i1 and j2 for j1, and return to (1).

(7) j2-1 is substituted into Image '(x, y) for all x and y satisfying i1≤Image (x, y) <i2.

Through the above steps (1) to (7), Image ′ (X
An image in which the histogram is flattened for _size and Y_size is created. Thereby, as shown in FIG.
Each image Im of the histogram shown in (a), (b), and (c)
The age (x, y) is converted into a flattened image Image '(x, y) as shown in FIGS. 7 (a'), (b '), and (c').

That is, a portion with a fine density distribution (a peak in the histogram)
Is expanded, and a portion having a sparse density distribution (a valley in the histogram) is compressed. Since a fine portion has a larger number of pixels than a sparse portion, the number of pixels to be expanded as a whole image increases, and the contrast is enhanced.

In the above device, the output signal level is changed for each color signal, so that the color balance is lost. Although optimal for performing image processing, it does not produce natural colors when output to a motor as it is. For this reason, the image processing device 30 does not normally operate, and operates under the control of the control signal generator 47 only when necessary. As a result, normally, it is possible to display a natural color on a monitor as in the conventional example.

The converted image can be stored in the auxiliary storage device 53, and the histogram can be output to an external output device 54 such as a printer.

In the above-described apparatus, the description has been given of the field sequential type electronic endoscope using RGB signals. However, the present invention can be similarly applied to a single-plate type electronic endoscope that decodes a composite video signal.

Next, a first embodiment of the present invention will be described. According to this embodiment, the effect of the histogram conversion can be obtained while maintaining the existing color tone by the endoscope.

The configuration of the first embodiment is the same as that of the endoscope image processing apparatus shown in FIG. 1 and FIG. In this embodiment, the image processing method of the image processing apparatus 30 in the image processing mode is different.
According to the flow shown in FIG. 11, the processed image of FIG. 12C is obtained through FIGS. 12A and 12B.

That is, when the image processing apparatus 30 shown in FIG. 1 is set to the image processing mode, the data in the memories 46R, 46G, 46B is sequentially transferred to the working memory 51. For example, for the R data transferred to the working memory 51, the arithmetic processing unit 52
Two pieces of pixel data are fetched and compared to leave a large value (small value), and the maximum value (minimum value) is detected by performing this comparison operation on the entire R data.
The same comparison operation is performed for the other G data and B data to detect the maximum value max and the minimum value min of each of R, G, and B shown in FIG.

The level between the maximum value max and the minimum value min is set to an appropriate number of levels to determine which level the data sequentially read from the working memory 51 corresponds to, and to determine a histogram calculation counter corresponding to the level. The count value is incremented by one. By performing this process on the entire R data, a histogram for the R signal can be calculated. Similarly, by performing on other G data and B data,
Histograms as shown in the second processing in FIG. 11 or in FIG. 12 ((a) and FIG. 12 (b)) are obtained.

Next, the above-described flattening process is performed on the range between the maximum value max and the minimum value min in the R data. The flattening process is similarly performed on the other G data and B data, and a flattened histogram is obtained for the R, G, and B signals as shown in FIG. Then, the analog switch 50 is turned on, and the flattened R, G, B data is supplied from the working memory 51 to the monitor 27 via the D / A converters 55a, 55b, 55c.
(See FIG. 2).

By performing the flattening process, the average value M of the color signals R, G, and B shown in FIG. 12A is compared with the average value of the processed image obtained by the flattening process shown in FIG. The value M 'does not change much.

Therefore, in the apparatus shown in FIGS. 1 and 2 in which the levels of the R, G, and B histograms after conversion are substantially the same, the entire image becomes white (or whitish), and the image of the endoscope before the processing is obtained. In contrast to this, the color tone becomes far apart, but in this embodiment, the conventional color tone is maintained and the advantage of the histogram conversion is obtained. In the first embodiment, the contrast can be enhanced by simple processing.

In the first embodiment, the flattening process may be performed so that the average value M of the image before the calculation of the histogram and the average value M ′ after the flattening process hardly change.

FIG. 13 shows a flow of image processing in the second embodiment of the present invention.

The structure of the first embodiment is the same as that of the apparatus shown in FIGS. 1 and 2 and the image processing is different.

As shown in FIG. 13, the average value of each of the R, G, and B images is calculated. This calculation is performed by transferring the R, G, B data of the memory unit 46 to the working memory 51, and by the arithmetic processing unit, each R, G, B
Is obtained, and the average value M is obtained by dividing by the number of sections of the maximum and minimum levels.

Then, Thus, a conversion table having the inflection point with the average value M is created. In this case, the average value M is set to the average value m for the signal range of 0 to 1.

That is, the signal range is 0 to 1, the average value is m, the input is x, the output is y, and p is a real number, for example, p = 4. The characteristics of the conversion table in this case are
A graph with characteristics as shown in FIG. 14 is obtained.

By performing the density conversion using the conversion table, the R, G, and B data in FIG. 15A can be obtained by image processing as shown in FIG. 15C.

Also in the second embodiment, density conversion is performed so that the average values of R, G, and B do not substantially change.

FIG. 16 shows an endoscope image processing apparatus 81 according to a third embodiment of the present invention.
Is shown.

This device 81 has a configuration in which a conversion processing unit 82 is provided between the D / A converter 8 and the image output terminal 9 in the prior example shown in FIG. Other configurations are the same as those of the preceding example shown in FIG.

 The configuration of the conversion processing unit 82 is shown in FIG.

The R, G, B signals analogized by the D / A converter 8 are input to the window circuit 91 and the first amplifier 92 as input signals. The window circuit 91 is a circuit that passes only a valid image signal portion, for example, a value of 10 to 254. An output of the window circuit 91 is input to an average value calculation circuit 93, and the average value signal is output from the circuit 93. It is applied to the gain control terminals of the first amplifier 92 and the second amplifier 94. The first amplifier 92 performs gain control based on the average value signal so that the average value is at the center of the signal level. On the other hand, the second amplifier 94
Performs a gain control that restores the gain control of the first amplifier 92.

The output of the first amplifier 92 is input to an A / D converter 95,
After being converted into a digital signal, the digital signal is applied to an address end of a table 96 composed of a ROM, and the memory content written at that address is read. The data read from the table 96 is input to the D / A converter 97, converted into an analog signal, amplified by the second amplifier 94, and output from the output terminal 9.

In the table 96, data of density conversion characteristics as shown in FIG. 18 (c) is written.

The A / D converter 95, the table 96, and the D / A converter 97 perform A / D conversion by the clock from the clock generator 98,
And the timing of D / A conversion is controlled.

 The operation of the third embodiment will be described below.

The operation up to the D / A converter 8 is the same as that in FIG. 19, and a description thereof will be omitted.

Thus, the input signals, that is, the R, G, B signals are respectively input to the conversion processing unit 82 via the D / A converter 8.
When the input signal level is set to 0 to 255 by the window circuit 91, the input signal passes only 10 to 245. That is, particularly bright portions and particularly dark image portions are removed.

The output of the window circuit 91 is input to an average value calculation circuit 93, where the signal is integrated, and the average brightness of the image is calculated. That is, the average of the brightness for the effective portion of the image is calculated. The output of the average value calculation circuit 93 is applied to the gain control terminal of the first amplifier 92, and the gain of the amplifier 92 is adjusted so that the average value is at the center of the signal level. As a result, the gain is adjusted to the level distribution of the output signal as shown in FIG. 18B with respect to the level distribution of the input signal shown in FIG. 18A.

The output of the first amplifier 92 is digitized by an A / D converter 95. This conversion is performed in synchronization with the clock of the clock generator 98. Thus, the output of A / D converter 95 is
The voltage is applied to the address end of the table 96, and density conversion is performed with the conversion characteristics shown in FIG. 18 (c).

The signal subjected to the density conversion by the table 96 is returned to an analog signal again by the next-stage D / A converter 97, and the level distribution of the signal in this case is as shown in FIG. 18 (d). .

The output of the D / A converter 97 is input to a second amplifier 94, and the second amplifier 94 reversely adjusts the gain adjusted by the first amplifier 92. Thus, the signal shown in FIG.

The signals R, G, and B that have undergone the above conversion processing are converted by the conversion processing unit 82.
Output from

Also according to the third embodiment, the average values of the densities of R, G, and B before and after the conversion processing become substantially equal.

Each of the above embodiments is not limited to an image obtained by an electronic endoscope, and may be applied to an image obtained by a fiberscope (or a rigid endoscope).

In the first embodiment, the maximum value and the minimum value are calculated from the density distribution. At this time, a predetermined number of all pixels, for example, 5%
May be set as the maximum value and the minimum value.

Also, the density level may be 5 steps (0 to 255), and the density value from the center may be the maximum value and the minimum value.

In the second and third embodiments, the conversion table is constituted by smooth curves, but may be approximated by two or more straight lines.

In the third embodiment, the conversion processing unit 82 is provided after the gamma circuit 3.
, But the gamma circuit 3 may be disposed on the contrary.

In the third embodiment, an analog signal is used for a part of the conversion processing unit 82, but all the signals may be digital signals.

Although the RGB signal is used in the embodiment of the present invention, it may be a color difference signal or a lightness / saturation / hue signal.

P that determines the characteristics of the conversion table in the second and third embodiments
May be different for each of the RGB signals.

In the first to third embodiments, it is possible to obtain an image in which colors and the like are emphasized without changing the original tone of the endoscope without substantially changing the average value of the original signal.

FIG. 9 shows a main part in a modification of the present invention.

In this modified example, in the endoscope image processing apparatus shown in FIG. 1 described above, by operating a newly provided switch 71, an ON signal of the switch 71 is detected by, for example, the control signal generation unit 47, and the light source unit 32 Is controlled to change the amount of illumination light.

That is, after illuminating with the normal illumination light amount, the control signal generator 47 outputs a control command for reducing the illumination light amount to the aperture control circuit 72, and the aperture blade 73 and the aperture that rotates the aperture blade 73. The aperture of the aperture device 75 including the motor 74 is increased. In this state, if an image of one frame is taken,
Next, the control signal generator 47 outputs a control command for increasing the illumination light amount to the aperture control circuit 72, reduces the amount of light shielding of the aperture blade 73, and performs imaging under a large illumination light amount. In addition,
Signals captured with different illumination light amounts are stored in the working memory
The image is transferred to 51 and image processing is performed.

The imaging with the normal illumination light amount is the same as that of the apparatus shown in FIG. That is, the distribution of the R, G, and B color signals is as shown in FIG.

On the other hand, when the illumination light amount is reduced, the histogram of the image captured under the red illumination light has a characteristic close to a normal distribution, as shown in FIG. 10 (b).

Further, when the illumination light amount is increased, FIG. 10 (c)
, The blue histogram is close to a normal distribution. Therefore, it is possible to obtain the information amount of the portion missing in the case of a normal image.

[Effects of the Invention] As described above, according to the present invention, a means for generating a histogram for each of a plurality of color signals constituting an image is provided, and each color signal is independently determined based on the histogram data. Since a means for converting the characteristics is provided, an effective information amount can be obtained even from a wavelength range that has been difficult to use until now.

[Brief description of the drawings]

1 to 8 relate to an endoscope image processing apparatus of the present invention, FIG. 1 is a configuration diagram of an endoscope image processing apparatus, FIG. 2 is an overall configuration diagram, and FIG. FIG. 4 is a flow chart, FIG. 4 is a characteristic diagram showing an example of a calculated histogram, FIG. 5 is a characteristic diagram showing a histogram of an image obtained by performing density conversion from the calculated histogram, and FIG.
FIG. 7 is a characteristic diagram showing a histogram of an image obtained by performing density conversion on arbitrary two density levels, FIG. 7 is a flowchart for performing flattening characteristic conversion, and FIG.
FIG. 9 is a characteristic diagram showing a histogram of an image obtained by the processing of FIG. 9, FIG. 9 is a configuration diagram showing a main part of a modified example of the endoscope image processing apparatus of the present invention, and FIG. 11 and 12 relate to the first embodiment of the present invention, and FIG. 11 is a flowchart of image processing in the third embodiment.
FIG. 12 is an explanatory diagram showing R, G, B images obtained by image processing, and FIGS. 13 to 15 relate to a second embodiment of the present invention.
FIG. 13 is a flowchart of image processing in the second embodiment, FIG. 14 is a characteristic diagram showing functions for performing density characteristics, and FIG. 15 shows R, G, and B images obtained by the image processing in the second embodiment. FIGS. 16 to 18 relate to a third embodiment of the present invention.
FIG. 16 is a block diagram showing the configuration of the third embodiment, FIG. 17 is a block diagram showing the configuration of the image processing unit in the third embodiment, FIG. 18 is a characteristic diagram for explaining the operation of the fifth embodiment, and FIG. FIG. 19 is a configuration diagram of the prior art, and FIG. 20 is a characteristic diagram showing a luminance distribution and a color signal level distribution in the prior art. 21: Endoscope image processing device 22: Electronic endoscope, 26: Observation device 27: Monitor, 30: Image processing device 32: Light source unit, 51: Working memory 52: Calculation processing Device, 53: Auxiliary storage device 54: External output device

Claims (2)

(57) [Claims] 1. A memory means capable of storing a first color signal, a second color signal, and a third color signal having a data amount corresponding to an image size of an image pickup means for picking up an endoscope image, and the memory means , Detecting the maximum value and the minimum value of the density level in the histogram with respect to the density level of each of the first color signal, the second color signal, and the third color signal, and detecting the detected maximum value And a density gradation conversion means for expanding the number of levels between the minimum value and the predetermined number of levels to generate a first color signal, a second color signal, and a third color signal subjected to density gradation conversion, Flattening processing means for flattening the histogram between the maximum value and the minimum value of the density level of each of the first color signal, the second color signal, and the third color signal whose density gradation has been converted; Conversion Signal processing means for generating a signal capable of displaying a color endoscopic image on the display means based on the first color signal, the second color signal, and the third color signal whose histogram has been flattened by the means; An endoscope image processing apparatus comprising: 2. A memory means capable of storing a first color signal, a second color signal, and a third color signal having a data amount corresponding to an image size of an imaging means for imaging an endoscope image; Average value calculating means for calculating an average value of the density levels in each of the histograms relating to the density levels of the first color signal, the second color signal, and the third color signal stored in the means; Density conversion table calculation means for calculating a density conversion table for the first color signal, the second color signal, and the third color signal having the average value at an inflection point based on the respective average values; Density conversion means for density-converting each of the first color signal, the second color signal and the third color signal based on each density conversion table calculated by the table calculation means; Signal processing means for generating a signal capable of displaying a color endoscopic image on a display means based on the first color signal, the second color signal, and the third color signal whose density has been converted by the density conversion means; An endoscope image processing apparatus comprising: