JP4426220B2 - Electronic endoscope device capable of split photometry - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic endoscope apparatus including a video scope having an image sensor. In particular, the present invention relates to brightness adjustment for appropriately maintaining the brightness of a displayed subject image by adjusting the opening / closing of an aperture, an electronic shutter function, or the like.
[0002]
[Prior art]
In a conventional electronic endoscope apparatus, when an image signal corresponding to a subject image is read from an image sensor in a video scope, a luminance value indicating the brightness of the subject image (hereinafter referred to as a representative luminance value) is calculated. Then, based on the difference between the luminance value and the reference luminance value indicating appropriate brightness, for example, the amount of light applied to the observation region is adjusted by opening and closing the diaphragm. As a photometric method for calculating the luminance value, there are average photometry for obtaining the average brightness of the entire screen, and peak photometry using a relatively high luminance value in the entire screen as the brightness of the subject image. There is also known a divided photometry method that divides a displayed subject image and assigns an appropriate photometry method for each divided area (see, for example, Patent Documents 1, 2, and 3). In these divided metering methods, the luminance value obtained for each area is weighted and then added up to calculate the representative luminance value, or the luminance value obtained for each area is added up to obtain the average value. Or calculate.
[0003]
[Patent Document 1]
JP 2000-333901 A (FIG. 3)
[Patent Document 2]
Japanese Patent Laid-Open No. 2002-98913 (FIG. 5)
[Patent Document 3]
JP 2000-81577 A (FIG. 8)
[0004]
[Problems to be solved by the invention]
In the conventional photometry method, when a high-brightness minute region that generates so-called halation straddles a plurality of areas, high-brightness information is dispersed in each area.
[0005]
As a result, the high luminance information is not sufficiently reflected in the representative luminance value, the erroneous brightness of the subject image is detected, and appropriate brightness adjustment cannot be performed.
[0006]
Therefore, an object of the present invention is to obtain an electronic endoscope apparatus or the like that can appropriately detect the brightness of a subject image even when a high-luminance minute region extends over a plurality of areas.
[0007]
[Means for Solving the Problems]
An electronic endoscope apparatus according to the present invention includes a light source for illuminating a subject, and a video scope including an image sensor that reads an image signal based on reflected light from the illuminated subject. And a luminance signal detecting means for sequentially detecting luminance signals of pixels constituting the subject image based on an image signal read from the image sensor, and a plurality of areas defined by dividing the entire subject image. On the other hand, the peak metering means for performing peak metering based on a predetermined peak detection characteristic to calculate the peak value, and the brightness of the subject image based on each peak value calculated for each of a plurality of areas. A luminance value calculating unit that calculates a representative luminance value to be shown; and a brightness adjusting unit that adjusts the brightness of the subject image based on the representative luminance value. For example, the peak value of the entire subject image may be calculated after weighting each peak value, or the average value may be calculated by adding the peak values. The brightness adjusting means adjusts the brightness by opening / closing the aperture, adjusting the light intensity of the light source, or adjusting the electronic shutter speed, for example.
[0008]
For each area, a peak detection characteristic corresponding to the area is given, and a peak value is calculated according to the characteristic. Therefore, even when a high-brightness minute region is straddling between areas, high-brightness information is appropriately detected, and appropriate brightness adjustment of the subject image is performed.
[0009]
The peak photometric means may calculate the peak value according to the following formula representing the peak detection characteristics. At this time, α and β corresponding to the corresponding area are determined in advance.
y (n) = β × y (n−1) + α × x (n)
However, y (n) is a luminance signal output from the peak photometry means, x (n) is a luminance signal input to the peak photometry means, α is a gain value for the input luminance signal, and β is a previous luminance to be fed back. A gain value for the signal y (n-1), n indicates a sample pixel.
[0010]
The endoscopic subject image brightness detection apparatus according to the present invention is configured such that the luminance of pixels constituting a subject image is based on an image signal corresponding to the subject image read from an image sensor that receives reflected light from an illuminated subject. A peak for performing peak metering based on a predetermined peak detection characteristic to calculate a peak value for each of a plurality of areas defined by dividing the entire subject image and a luminance signal detecting means for sequentially detecting signals. It is characterized by comprising photometric means and luminance value calculating means for calculating a representative luminance value indicating the brightness of the subject image based on each peak value calculated for each of a plurality of areas.
[0011]
The endoscope subject image brightness detection method according to the present invention is based on an image signal corresponding to a subject image read from an image sensor that receives reflected light from an illuminated subject, and brightness of pixels constituting the subject image. For each of a plurality of areas defined by sequentially detecting signals and dividing the entire subject image, peak photometry is performed based on a predetermined peak detection characteristic to calculate a peak value. On the basis of the calculated peak values, a representative luminance value indicating the brightness of the subject image is calculated.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a block diagram of an electronic endoscope apparatus according to the first embodiment. When examination, surgery, etc. are started, the video scope is inserted into the body.
[0014]
The electronic endoscope apparatus includes a video scope 50 having a CCD (Charge-Coupled Device) 54 and a processor 10 for processing a signal read from the CCD 54, and a monitor 32 and a keyboard 34 for displaying a subject image. Are connected to the processor 10. The video scope 50 is detachably connected to the processor 10.
[0015]
When a lamp power switch (not shown) is turned on, power is supplied from the lamp power source 11 including the lamp control circuit 11A to the lamp (light source for illumination) 12, and thereby light is emitted from the lamp 12. The light emitted from the lamp 12 enters the incident end 51 </ b> A of the light guide 51 provided in the video scope 50 through the condenser lens 14. The light guide 51 is a bundle of ultrafine optical fibers that transmits light emitted from the lamp 12 to the distal end portion 60 of the video scope 50 in the vicinity of the observation site S. The light that has passed through the light guide 51 is emitted from the emission end. The light is emitted from 51B. As a result, light is irradiated to the observation region S that is the subject through the light distribution lens 52 that is an illumination lens, and the observation region S is illuminated.
[0016]
The light reflected at the observation site S passes through the objective lens 53 and reaches the light receiving area of the CCD 54, whereby an optical image of the observation site S is formed in the light receiving area of the CCD 54. In the present embodiment, a simultaneous single plate type is applied as a color imaging method, and yellow (Ye), cyan (Cy), magenta (Mg), and green (G) color elements are checked on the light receiving surface of the CCD. Complementary color filters (not shown) arranged in a line are arranged so as to correspond to the respective pixel positions in the light receiving region. In the CCD 54, an image signal composed of a plurality of pixel signals corresponding to the color of light transmitted through each color element of the complementary color filter is generated by photoelectric conversion, and an image signal for one frame or one field is generated at predetermined time intervals. The color difference lines are sequentially read out in accordance with the sequential method. In the present embodiment, the NTSC system is applied as a color television system, and image signals for one frame (one field) are sequentially read out every 1/30 (1/60) second interval, and an initial signal processing circuit. 55.
[0017]
The initial signal processing circuit 55 includes a preamplifier, a sample hold circuit, an image memory, an image processing circuit (none of which are shown), and the image signal input to the initial signal processing circuit 55 After processing, it is converted into a digital image signal and temporarily stored in an image memory. The digital image signal read from the image memory is sent to the image processing circuit, subjected to processing such as white balance adjustment and gamma correction, and then sent to the processor signal processing circuit 28 of the processor 10. Also, a luminance signal that is a luminance component of the image signal input to the initial signal processing circuit 55 is generated, converted into a digital signal by an A / D converter (not shown), and then the dimming circuit 23 of the processor 10. Sent to. Here, in accordance with the NTSC system, a luminance signal for one frame is sequentially sent every 1/30 (1/60) second interval.
[0018]
In the processor signal processing circuit 28, predetermined processing is performed on the image signal sent from the initial signal processing circuit 55. The processed image signal is output to the monitor 32 as a video signal (video signal) such as an NTSC composite signal, a Y / C separation signal (so-called S video signal), or an RGB separation signal, whereby a subject image is displayed on the monitor 32. It is.
[0019]
The system control circuit 22 of the processor 10 includes a CPU 24, a ROM 25, and a RAM 26. The CPU 24 controls the entire processor 10, and each circuit such as a light control circuit 23, a lamp control circuit 11A, and a processor signal processing circuit 28. Output a control signal. In the timing control circuit 30, a clock pulse for adjusting a signal processing timing is output to each circuit in the processor 10, and a synchronization signal accompanying the video signal is sent to the processor signal processing circuit 28. The ROM 25 in the system control circuit 22 stores in advance a program for controlling the entire electronic endoscope apparatus.
[0020]
A diaphragm 16 that adjusts the amount of light applied to the subject S is provided between the incident end 51 </ b> A of the light guide 51 and the condenser lens 14, and opens and closes by driving the motor 18. In the present embodiment, the light control circuit 23 constituted by a DSP (Digital Signal Processor) controls the light amount adjustment of the light passing through the diaphragm 16, that is, the light applied to the subject S. The dimming circuit 23 transmits a control signal for adjusting the amount of light to the motor driver 20 based on the luminance signal sequentially sent from the video scope 50. The motor driver 20 transmits a drive signal to the motor 18 based on this control signal. As a result, the motor 18 is operated and the diaphragm 16 is driven so as to have a predetermined opening.
[0021]
In the video scope 50, a scope control unit 56 for controlling the entire video scope 50 and an EEPROM 57 in which data related to the video scope 50 are stored in advance are provided. The scope control unit 56 controls the initial signal processing circuit 55 and reads scope-related data from the EEPROM 57. When the video scope 50 is connected to the processor 10, data is transmitted and received between the scope control unit 56 and the system control circuit 22, and the data is sent to the system control circuit 22.
[0022]
The front panel 46 of the processor 10 is provided with a setting switch 46A for setting a reference luminance value Yr used as a standard in automatic light control. When the operator operates the switch, a signal corresponding to the operation is sent to the system control. It is sent to the circuit 22. The data of the reference luminance value Yr is temporarily stored in the RAM 26 and sent from the system control circuit 22 to the dimming circuit 23 as necessary.
[0023]
FIG. 2 is a schematic block diagram of the light control circuit 23, and FIG. 3 is a diagram showing a photometry area.
[0024]
As shown in FIG. 3, the entire area AA of the displayed subject image is divided into five photometric areas. Here, each photometric area is divided into area A, area B, area C, area D, and area. E. In the light control circuit 23, the first detector 71 to the fifth detector 75 detect the peak value of each photometric area, and the overall detector 82 detects the overall peak value (representative luminance value) for the entire subject image area AA. The However, the peak value and the luminance value of each pixel constituting the subject image are represented by luminance level values divided into 2 ⁸ = 256 levels. The luminance value and the peak value of each pixel are any one of 0 to 255.
[0025]
As will be described later, each detection circuit has a peak detection characteristic corresponding to the corresponding photometry area, and a parameter for determining the peak characteristic is preset in each detection circuit, and the peak value is detected according to the parameter value. The The peak value output from each detection circuit is weighted by the weighting coefficient specific to each area in the weighting circuits 76 to 80 and sent to the whole peak detector 82. In the total peak detector 82, the peak value which is the maximum value among the five peak values is selected. The selected maximum peak value is compared with a preset reference peak value, and a control signal is transmitted to the motor driver 20 based on the difference information.
[0026]
FIG. 4 is a block diagram of the first detector 71 of FIG.
[0027]
The first detector 71 includes amplifiers 92 and 93, a comparator 94, a switch 96, and a delay memory 98. Luminance signals corresponding to the pixels in the area A area are sequentially input to the amplifier 92 and the comparator 94 by the number of samples in time series. The gains α ₁ and β ₁ that determine the peak characteristics of the amplifiers 92 and 93 satisfy the following relationship.
α ₁ + β ₁ = 1 (1)
[0028]
The luminance signal input to the first detector 71 is sent to the amplifier 92 and the comparator 94. The luminance signal input to the amplifier 92 is amplified by α ₁ , stored in the delay memory 98, added to the previous luminance signal amplified by β _{1 in} the amplifier 93, and sent to the switch 96. Hereinafter, the input luminance signal is represented by x (n), and the luminance signal stored in the delay memory 98 is represented by an in-memory luminance signal y (n−1). Here, n indicates the number of samples (number of pixels to be sampled).
[0029]
On the other hand, the comparator 94 compares the luminance level of the input luminance signal x (n) with the luminance level of the luminance signal stored in the delay memory 98 when the previous luminance signal was input. When the luminance level of the in-memory luminance signal y (n−1) is higher than the luminance level of the input luminance signal x (n), an L (Low) signal is input to the switching circuit 96. The switching circuit 96 connects the contact S2 and the delay memory 98 according to the L signal. On the other hand, when the luminance level of the in-memory luminance signal y (n−1) is smaller than the luminance level of the input luminance signal x (n), an H (High) signal is sent to the switching circuit 96. The switching circuit 96 connects the contact S1 and the delay memory 98 according to the H signal.
[0030]
The luminance signal stored in the delay memory 98 is fed back to the switching circuit 96 and the amplifier 93 in accordance with the input timing of the reset pulse, and is sent to the whole peak detector 82 shown in FIG. When a new input luminance signal x (n + 1) is input to the first detector 71, the comparator 94 determines the luminance level of the input luminance signal x (n + 1) and the luminance level of the in-memory luminance signal y (n). Are compared. As long as the luminance level of the newly input luminance signal does not become higher than the luminance level of the luminance signal stored in the delay memory 98, the luminance signal stored in the delay memory 98 is continuously output to the overall peak detector 82.
[0031]
The second detection circuit 72 to the fifth detection circuit 75 are also configured in the same manner as the first detection circuit 71. In each circuit, the gains α _k and β _k corresponding to the area (k = 2 to 5) are set. It has been established.
[0032]
Here, when the input luminance signal x (n) is larger than the in-memory luminance signal y (n−1) with respect to the peak detection characteristic of the luminance signal, the luminance signal stored in the delay memory 98 is y (n). y (n) is based on the input luminance signal x (n) and the in-memory luminance signal y (n−1), and follows the following difference equation.
y (n) = [beta] _k * y (n-1) + [alpha] _k * x (n) (2)
When the equation (1) is solved, y (n) is expressed by an exponential function shown in the following equation. However, β _k ^ n represents β _k ⁿ .
y (n) = α _k β _k / (β _k −1) × β _k ^ n
+ Α _k / (1−β _k ) × 1 (3)
Similarly to the equation (1), α _k and β _k (k = 1 to 5) satisfy the following relationship.
α _k + β _k = 1 (4)
[0033]
The gains α _k and β _k are respectively set to appropriate values based on the subject (observation site) or the location of the corresponding photometric area. Preferably, after determining the minimum area in the entire subject image area AA, that is, the number of samples n, α _k and β _k are determined for each area. For example, when α _k = β _k = 0.5, the luminance signal y (n) is expressed by the following equation.
y (n) = 1-0.5 ^ (n + 1) (5)
[0034]
FIG. 5 is a diagram showing the luminance level characteristic of the luminance signal y (n) stored in the delay memory 98. Here, when a high-brightness minute region is generated in area A and area B, the characteristic of the luminance signal level according to the location of the minute region is shown.
[0035]
When the average brightness level is calculated for each photometric area as a conventional method, a high brightness minute area D (area = number of samples = d) exists across area A and area B as shown in the brightness level state (A). In this case, the levels of the luminance signals y1 and y2 are both close to half the peak value. Therefore, the high luminance information is dispersed in area A and area B, and the brightness of the subject image is not properly detected.
[0036]
When α ₁ = α ₂ = 1 and β ₁ = β ₂ = 0, once the luminance value of the peak value is input to the delay memory 98 shown in FIG. 3, the luminance signal of the peak value is switched to the switching circuit 96 and the delay memory. 98 is repeatedly input. Therefore, as shown in the luminance level state (B), the levels of the luminance signals y1 and y2 are maintained at the peak values. On the other hand, when α ₁ = α ₂ = β ₁ = β ₂ = 0.5, as shown in the luminance level state (C), the levels of the luminance signals y1 and y2 near the boundary between the areas A and B are Maintain peak value.
[0037]
Here, for a high-brightness subject straddling the photometric area, when the fluctuation tolerance of the luminance fluctuation generated across the boundary of the area is made to correspond to the luminance resolution, that is, the fluctuation rate for 1 bit (= 1/256 = 0.4%) is assumed to be a variation allowable rate, the sampling number n satisfies the following conditional expression. However, α _k = β _k = 0.5.
y (n) = 1-0.5 ^ (n + 1)> (1-1 / 256) (6)
From equation (6), n must satisfy the following conditional expression.
n> 6.97 (7)
Since n is a natural number, 7 or more sample pixels are required.
[0038]
As described above, according to the present embodiment, the first to fifth detection circuits 71 to 75 having the peak detection characteristics represented by α _k and β _k are provided in the dimming circuit 23, and the entire subject image region A peak value of the luminance signal is detected based on a predetermined sample pixel in AA. Since α _k and β _k of the amplifiers 92 and 93 can be determined according to the subject image, the peak value is properly detected even when the high-intensity minute region D straddles between the divided areas A to E. The
[0039]
Instead of adjusting the brightness of the subject image by opening and closing the aperture, the light intensity of the light source may be directly adjusted. Alternatively, the brightness of the subject image may be adjusted by controlling the charge accumulation time using the electronic shutter function of the CCD 54.
[0040]
Next, a second embodiment will be described with reference to FIG. FIG. 6 is a block diagram of the dimming circuit 23 in the second embodiment.
[0041]
As shown in FIG. 6, in the second embodiment, an overall average peak detector 82 ′ is provided in the dimming circuit 23. Then, the weighted peak values of the areas A to E are added, and the average value is detected as the peak value.
[0042]
【The invention's effect】
As described above, according to the present invention, it is possible to appropriately detect the brightness of a subject image even when a plurality of high-brightness micro-regions span a plurality.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electronic endoscope apparatus according to a first embodiment.
FIG. 2 is a block diagram of a dimming circuit.
FIG. 3 is a diagram showing a photometric area.
FIG. 4 is a block diagram showing a first detector.
FIG. 5 is a diagram showing a luminance level characteristic according to a peak detection characteristic.
FIG. 6 is a block diagram of a dimming circuit according to a second embodiment.
[Explanation of symbols]
10 Processor 12 Lamp (light source)
16 Aperture 23 Light control circuit 50 Video scope 54 CCD (image sensor)
71 first detector 72 second detector 73 third detector 74 fourth detector 75 fifth detector 92, 93 amplifier 94 comparator 96 switch 98 delay memory α ₁ , β ₁ gain

Claims (3)

An electronic endoscope apparatus comprising: a light source for illuminating a subject; and a video scope having an image sensor that reads an image signal based on reflected light from the illuminated subject,
Luminance signal detection means for sequentially detecting the luminance signals of the pixels constituting the subject image based on the image signal read from the image sensor;
Peak metering means for performing peak metering based on a predetermined peak detection characteristic for calculating a peak value for each of a plurality of areas defined by dividing the entire subject image;
Luminance value calculating means for calculating a representative luminance value indicating the brightness of the subject image based on each peak value calculated for each of the plurality of areas;
Brightness adjusting means for adjusting the brightness of the subject image based on the representative brightness value ;
An electronic endoscope characterized in that the peak photometric means calculates a peak value according to a peak detection characteristic characterized by α and β in the following equations, and values of α and β are determined in advance according to a corresponding area. Mirror device.
y (n) = β × y (n−1) + α × x (n)
However, y (n) is a luminance signal output from the peak photometry means, x (n) is a luminance signal input to the peak photometry means, α is a gain value for the input luminance signal, and β is fed back. A gain value for the previous luminance signal y (n-1), n indicates a sample pixel. A luminance signal detecting means for sequentially detecting luminance signals of pixels constituting the subject image based on an image signal corresponding to the subject image read from the image sensor that receives reflected light from the illuminated subject;
Peak metering means for performing peak metering based on a predetermined peak detection characteristic for calculating a peak value for each of a plurality of areas defined by dividing the entire subject image;
A luminance value calculating means for calculating a representative luminance value indicating the brightness of the subject image based on each peak value calculated for each of the plurality of areas ;
Endoscope characterized in that the peak photometric means calculates peak values according to peak detection characteristics characterized by α and β in the following formulas, and α and β values are determined in advance according to corresponding areas. Subject image brightness detection device.
y (n) = β × y (n−1) + α × x (n)
However, y (n) is a luminance signal output from the peak photometry means, x (n) is a luminance signal input to the peak photometry means, α is a gain value for the input luminance signal, and β is fed back. A gain value for the previous luminance signal y (n-1), n indicates a sample pixel. Based on the image signal corresponding to the subject image read from the image sensor that receives the reflected light from the illuminated subject, the luminance signal of the pixels constituting the subject image is sequentially detected,
For each of a plurality of areas defined by dividing the entire subject image, execute peak metering based on a predetermined peak detection characteristic to calculate a peak value,
Based on each peak value calculated for each of the plurality of areas, a representative luminance value indicating the brightness of the subject image is calculated ,
Endoscopic object image brightness detection characterized in that peak values are calculated according to the peak detection characteristics characterized by α and β in the following equations, and α and β values are predetermined according to the corresponding areas. Method.
y (n) = β × y (n−1) + α × x (n)
However, y (n) is a luminance signal output from the peak photometry means, x (n) is a luminance signal input to the peak photometry means, α is a gain value for the input luminance signal, and β is fed back. A gain value for the previous luminance signal y (n-1), n indicates a sample pixel.

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