JPH05164976A - Electronic endoscope device - Google Patents

Abstract

(57) [Abstract] [Purpose] The metering system in the automatic light control mechanism can be automatically switched based on the image data to reduce the operational burden on the operator and enhance the inspection efficiency. [Structure] The video process circuit which receives the image signal from the CCD calculates a histogram of the image signal (steps 32 and 36 in FIG. 3). On this histogram, the threshold value of the image intensity is set, and the ratio of the total value of the frequencies of the regions divided by this threshold value is checked (steps 33 and 3 in the same figure).
7). As a result of this ratio check, when the ratio of the total frequency value of the regions above the threshold value exceeds the constant ratio 0.4, the peak metering mode is switched to (step 34 in the figure). On the contrary, when the ratio falls below the fixed ratio of 0.2, the mode is switched to the average photometry mode (step 38 in the figure).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic endoscope system, and more particularly, to automatic light control (ALC) for illuminating a subject.
Regarding improvement of Auto Light Control) function.

[0002]

2. Description of the Related Art Generally, an automatic light control mechanism in an electronic endoscope apparatus generates a light amount adjustment signal, that is, an input signal for a light amount diaphragm, using an image signal obtained based on reflected light from a subject, This input signal is supplied to the diaphragm control circuit together with the reference signal to form a feedback system. There are an average metering method and a peak metering method as a photometric method for generating the light amount adjustment signal. The average photometry is a method of calculating the average value of the image signal and adopting the average value as the light quantity adjustment signal, and the peak photometry is the method of adopting the signal of the highest value among the image signals as the light quantity adjustment signal.

When the average photometry method is adopted, the average value forms a light amount adjustment signal when observing a protruding portion such as the corner of the stomach, so that the light from the automatic light control mechanism is strongly controlled, Halation occurs due to the strong reflected light from the corners, making it unobservable. On the other hand, when peak metering is adopted, if strong reflected light is present in part, the image signal due to the strong reflected light forms a light amount adjustment signal, so most of the image other than that strong reflected light becomes dark. Becomes unobservable.

Therefore, conventionally, in order to avoid these unobservable states, the operator manually switches the photometric system (photometric mode) each time while observing the monitor, and the aperture control circuit is also provided as necessary. The amount of light itself is manually adjusted by adjusting the level of the reference signal for.

[0005]

However, the electronic endoscope apparatus configured to manually switch even the photometric method as described above has a too wide range of manual operation by the operator, and the operator has a great deal of operational problems. There is a problem in that the burden is imposed and the inspection time becomes long, and the inspection efficiency decreases.

The present invention has been made in view of such a conventional problem, and enables automatic selection of a photometric system in accordance with the reflected light state of a target portion of a subject, which can be operated by an operator. It is an object of the present invention to provide an electronic endoscope device that can reduce the burden and the examination time.

[0007]

In order to achieve the above object, the electronic endoscope apparatus according to the present invention calculates a light amount adjustment signal from image data by using a commanded photometric method, as shown in FIG. The light amount adjustment signal calculation unit and the automatic light adjustment unit that automatically adjusts the light amount emitted from the illumination unit to the subject according to the calculation signal of the light amount adjustment signal calculation unit are provided. Further, an illumination state calculation means for calculating information on the illumination state of the subject by the illumination section from the image data, and a photometric system setting means for setting the photometric system based on the computation information of the illumination state calculation means are provided. There is. In particular, the illumination state calculation means is, for example, means for calculating the histogram of the image data as information on the illumination state, and the photometric method setting means is, for example, an average metering method or a peak metering method, and a metering method according to the calculation information. It is a means for selecting a method.

[0008]

The illumination state calculation means calculates, for example, a histogram of image data as a parameter relating to the illumination state by the illumination unit. Based on this histogram, the photometry method setting means sets, for example, the average photometry method or the peak photometry method, and gives an instruction to the light amount adjustment signal calculation means. This allows
For example, when strong reflection occurs in a close-up image, such as in the corner of the stomach, the light intensity is automatically adjusted to a certain value by the light intensity adjustment signal calculated based on the peak metering method, and the halation The part becomes easy to observe. Also, if there is a strong spot-like reflection part in the image and the field of view other than the spot-like part becomes dark in the peak metering method, the light intensity adjustment signal is automatically adjusted based on the average metering method. Is calculated. This prevents a situation where most of the screen is dark.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

The electronic endoscope apparatus according to this embodiment is shown in FIG.
As shown in FIG. 3, the illumination unit 2 that illuminates the subject 1 and the control unit 3 that controls the amount of light emitted from the illumination unit 2 are provided.

The illumination unit 2 is a xenon lamp 1 which serves as a light source.
0, a lamp power source 11 for turning on the xenon lamp 10, a condenser lens 12 for collecting the light emitted from the xenon lamp 10, a rotary filter 13 arranged on the output side of the condenser lens 12, and a rotation for this rotation. The light guide 14 guides the light transmitted through the filter 13 to the subject 1.

The control unit 3 receives the reflected light of the object 1, the CCD (solid-state image sensor) 21 for converting the transmitted light of the objective lens 20 into an electric signal, and the CC.
Video processing circuit 2 for processing the converted electric signal of D21
Have two. Further, the control unit 3 controls the diaphragm 25 inserted in the optical path between the xenon lamp 10 and the condenser lens 12.
And an automatic light control means including an aperture motor 26 for driving the aperture 25 and an aperture control circuit 27 for controlling the rotation of the aperture motor 26. The light guide 14,
The objective lens 20 and the CCD 21 are mounted in the electronic scope.

The aperture control circuit 27 is supplied with a light amount adjustment signal S _L calculated by the video process circuit 22 as shown in FIGS. 3 and 4 which will be described later, and serves as a reference signal set by an operation panel (not shown). The dimming level setting signal S _D is supplied. Then, the aperture control circuit 27 compares the supplied light amount adjustment signal S _L with the setting signal S _D , calculates the difference signal, further amplifies the difference signal, and supplies it to the aperture motor 26. As a result, a feedback system for automatic light control is formed. The video process circuit 22 is equipped with a microcomputer to process the procedures shown in FIGS.

Next, the operation of this embodiment will be described with reference to FIGS.

The video process circuit 22 performs the process shown in FIG. 3 as the setting control of the photometric mode (photometric system), and during the process shown in FIG. 3, every minute fixed time (for example, 20 msec). As the timer interrupt processing of, the light quantity adjustment signal arithmetic processing shown in FIG. 4 is performed.

First, the algorithm related to the processing of FIG. 3 will be described. In step 30 of FIG. 3, the video process circuit 22 sets the average photometry mode as an initial setting. This is done, for example, by setting the mode flag F = 1. Next, the video process circuit 22 inputs the image signal (pixel value) in step 31, and calculates the histogram of the image signal input in step 32.
Thus, for example, as shown in FIG. 6, when the horizontal axis represents the intensity (pixel value) of the image signal, the vertical axis represents the frequency of each intensity.

Next, the video process circuit 22 shifts the processing to step 33, and "A / (A + B)>"
It is determined whether it is R ₁ ”. Here, assuming that the threshold value T ₁ is, for example, 80% of the maximum allowable pixel value (for example, 255), the total value of each frequency for pixel values equal to or higher than the threshold value T ₁ is A, the total value of each frequency and B for the pixel values less than _1, the ratio R ₁ is in this example "0.
4 ”. When the determination in step 33 is NO, the process returns to step 31, and the process of steps 31 to 33 is repeated while waiting. During this standby, the average metering mode is maintained as the metering mode.

However, when the determination is YES in step 33, the video process circuit 22 proceeds to step 34, and this time, the peak metering mode is set and the mode flag F =
Select by setting to 0.

Next, the video process circuit 22 sequentially performs the processing of steps 35 to 37. The processing contents of steps 35 and 36 are the same as the above-mentioned steps 31 and 32. In addition the step 37, it is determined whether the "C / (C + D) < R 2 ". Here, assuming that the threshold value T ₃ is 80% of the maximum value (≦ 255) of the signal intensity (pixel value) in the current captured image, for example, the sum of frequencies for pixel values equal to or higher than the threshold value T ₃ Let C be the value, D be the total value of each frequency for pixel values less than the threshold value T ₃ , and the ratio R ₂ here is “0.2”.

When the determination in step 37 is NO, the process returns to step 35, and the process of steps 35 to 37 is repeated to wait. During this standby, the peak metering mode is maintained as the metering mode. However, when the determination in step 37 is YES, the process proceeds to step 38.

Next, at step 38, the mode flag F
By setting = 1, the average photometry mode is instructed this time. After that, the process returns to step 31, and the series of processes described above is repeated.

Next, the timer interrupt processing of FIG. 4 will be described. In step 50 of FIG. 4, the video process circuit 22
Determines whether the mode flag F = 1, that is, whether the mode at the time of the current interrupt is the average photometry mode.

If the determination in step 50 is YES, that is, if it is determined that the average photometry mode is instructed, then the processes in steps 51 to 53 are sequentially performed. That is, the image signal at that time is read in step 51, the average value of the pixel values is calculated in step 52, and the calculated average value is output to the aperture control circuit 27 as the light amount adjustment signal S _L. It

On the other hand, in step 50, NO (F =
If it is determined to be 1), that is, if it is determined that the peak metering mode is instructed, step 54
The processes of to 56 are sequentially performed. That is, the image signal at that time is read in step 54, the peak value in the image signal is calculated in step 55, and in step 56,
The calculated peak value signal is output to the aperture control circuit 27 as the light amount adjustment signal S _L.

The output light amount adjustment signal S _L is compared with the dimming level setting signal S _{D in} the diaphragm control circuit 27. That is, since the control signal based on these deviation signals is given to the diaphragm motor 26 and the diaphragm 25 is driven, the amount of light illuminating the subject 1 is narrowed so that the deviation becomes zero.

As described above, the photometric mode is updated in real time by the process of FIG. 3, and the light amount adjustment signal S _L is calculated and output by the process of FIG. 4 based on the updated photometric mode.

In this embodiment, the video process circuit 22
4 corresponds to the light amount adjustment signal calculation means, and is performed in steps 31, 32, 35, and 3 in the procedure of FIG.
The processing of 6 corresponds to the illumination state calculation means, and the processing of steps 33, 34, 37, and 38 in the figure corresponds to the photometric method setting means.

Next, the overall operation will be specifically described with reference to FIGS.

Now, the dimming level setting signal S _D as a reference signal set by the manual operation of the operator
Holds a constant value. The initial photometry mode after the device is activated is set to the average photometry mode (step 30 in FIG. 3).
reference). It is assumed that an endoscopic image of the corner of the stomach is captured, for example, as shown in FIG. 5 during photographing of the light amount control in the average photometry mode. In general, since the endoscopic image of the corner of the stomach is a close-up image, halation occurs due to strong reflected light, and there is a possibility that observation will not be possible in the average photometry mode. The histogram in the ROI (region of interest: see FIG. 5) set in the central portion of the monitor image when this halation occurs is biased near the maximum allowable intensity (pixel value 255), as shown in FIG. 6, for example. A high intensity distribution is seen.

However, in this embodiment, as shown in FIG. 6, the area within the curve for pixel values above the threshold T ₁ ,
That is, when the total value A of each frequency becomes large, “A / (A +
B) ”exceeds 0.4 (step 3 in FIG. 3).
3). Thus, now changed to a peak metering mode, the feedback control of the light amount based on the peak metering mode, the highest intensity value in the image, the dimming level setting signal S _D (for example, the maximum intensity of a certain value 70 %
The value T _2: is adjusted to follow the see Figure 7). The histogram in this light amount control state is shown in FIG.

Therefore, even when a close-up image such as a corner of the stomach is obtained, halation does not occur and the image cannot be observed. Moreover, when an illumination state in which halation may occur is reached, the peak automatically and timely. It is possible to reduce the operational burden on the operator by switching to the photometric mode.

On the other hand, it is assumed that there is a strong spot-like reflected light in the endoscopic image during the light amount control in the peak metering mode. In the peak metering mode, since the strongly reflected light is the intensity of the peak in the image, the light amount is limited so that the intensity value matches the constant threshold value T ₂ (see FIG. 7). As a result, the histogram is represented as shown in FIG. 8, for example. That is, the histogram of most of the screen area other than such strongly reflected light may be biased toward the low intensity side, and the entire monitor screen may become dark.

However, in this embodiment, when the histogram is biased toward the low intensity side as described above and the ratio of the area D (total value of frequencies) on the low intensity side in FIG. 8 increases, "C /
The condition of (C + D) <0.2 is satisfied. That is, FIG.
It is determined to be YES in the process of step 37, and the average photometry mode is returned again this time. Therefore, average photometry, that is, RO
The irradiation light amount is feedback-controlled so that the average value of the image intensity in I follows the dimming level setting signal S _{D having} a certain constant value (for example, 70% value T ₂ of maximum intensity: see FIG. 7).

Therefore, during observation based on peak photometry,
For example, even when strong spot-shaped reflected light is generated in the endoscopic image, the screen other than the spot portion does not become dark and unobservable. In addition, when the lighting condition that may cause such a dark screen condition is reached, the mode is automatically and timely returned to the average photometry mode, and the manual operation of the operator can be reduced also here. Further, the automatic switching of the photometric mode can shorten the inspection time and increase the inspection efficiency.

In the above embodiment, the threshold value and the ratio for switching between the peak metering mode and the average metering mode are not limited to the above-mentioned numerical values, but can be set to appropriate values according to experimental results. is there. The range for calculating the histogram is not limited to the ROI and may be the entire monitor screen.

[0036]

As described above, the electronic endoscope apparatus according to the present invention calculates the light amount adjustment signal from the image data by using the instructed photometric method, and according to this operation signal,
While automatically adjusting the amount of light emitted from the illumination unit to the subject, information regarding the illumination state of the illumination unit (for example, a histogram) is calculated from the image data, and a photometric method (for example, an average photometric method, based on the calculated information). Peak metering method) is set. Therefore, it is possible to automatically and timely switch the photometric method that is the basis of the calculation of the input signal for controlling the light amount. Therefore, when there is halation or strong spot-like reflected light at the time of photographing the stomach corner or the like. You can accurately eliminate the situation where the screen becomes dark,
There is an effect that it is possible to avoid the unobservable state of the screen, improve the inspection efficiency, and significantly reduce the operational burden on the operator to improve the operation efficiency.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to claims of an electronic endoscope apparatus according to the present invention.

FIG. 2 is a schematic block diagram showing a light amount control portion of the electronic endoscope apparatus according to the present invention.

FIG. 3 is a schematic flowchart showing a procedure for setting a photometric mode.

FIG. 4 is a schematic flowchart showing a calculation procedure of a light amount adjustment signal.

FIG. 5 is an explanatory diagram showing an example of a monitor screen of a stomach corner.

FIG. 6 is a histogram of image data showing an example of gastric corner imaging under the average photometry mode.

FIG. 7 is a histogram of image data showing an example of gastric corner imaging under peak metering mode.

FIG. 8 is a histogram of image data as an example when strong spot-shaped reflected light is present in the peak metering mode.

[Explanation of symbols] 1 subject 2 illumination unit 3 control unit 10 xenon lamp 11 lamp power supply 12 condenser lens 14 light guide 22 video process circuit 25 diaphragm 26 diaphragm motor 27 diaphragm control circuit

Claims (2)

[Claims] 1. A light amount adjustment signal calculation means for calculating a light amount adjustment signal from image data using a commanded photometric method,
In an electronic endoscope apparatus equipped with an automatic light control device that automatically adjusts the amount of light emitted from an illumination unit to a subject in accordance with a calculation signal of the light amount adjustment signal calculation unit, illumination of the subject by the illumination unit. An electronic endoscope comprising: an illumination state calculating means for calculating information on a state from the image data; and a photometric system setting means for setting the photometric system based on the arithmetic information of the illumination state calculating means. apparatus. 2. The illumination state calculation means is a means for calculating a histogram of the image data as information on the illumination state, and the photometric method setting means responds to the arithmetic information from among an average photometry method and a peak photometry method. The electronic endoscope apparatus according to claim 1, which is a means for selecting a photometric method.