Endoscope system and operation method thereof

Abstract

To provide an endoscope system for capturing images at appropriate brightness even in a state where a distance from an observation object changes frequently, and operation method thereof.SOLUTION: An endoscope system includes a processor. The processor executes exposure control based on an endoscopic image captured by an endoscope having an imaging device, calculates brightness information representing a degree of brightness of a peripheral edge of the endoscopic image, and controls a tracking speed of the exposure control according to the brightness information. The brightness information is compared with past brightness information, the information of past brightness, and a suppression coefficient for suppressing an amount of change or a rate of change in the exposure determined according to the comparison result is applied to the exposure control, thereby controlling the tracking speed.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an endoscopic system and a method of operation thereof. [Background technology]

[0002] In recent years, in the medical field, in systems that acquire images and observe objects, dimming control is widely used to optimize the brightness of the image of the object being observed. In such dimming control, brightness information of the image is calculated based on the luminance value of the image, and the emitted light amount and imaging parameters of the imaging device are changed so that the brightness information becomes a target value.

[0003] In the case of the above-mentioned dimming control, even if the brightness of the object being observed on the screen being observed by the user is optimal, the brightness of the image may be determined to be different from the optimal value due to disturbances such as light reflection, and the emitted light amount or the imaging parameters of the imaging device may be unintentionally changed. In order to suppress unintentional changes, a technology has been developed to switch dimming control in response to changes in the observation field of view, etc., and a medical dimming control device described in Patent Document 1 is known as an example.

[0004] The medical dimming control device in Patent Document 1 makes it possible to quickly obtain an image of optimal brightness by controlling dimming at a fast tracking speed when a change is made to the observation field of view or imaging conditions, and once an image of optimal brightness is obtained, the tracking speed is switched to a slower speed to avoid tracking unintended brightness fluctuations, allowing the user to observe the subject they actually want to observe with the dimming adjusted to match it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-154680 A Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, the dimming control assumes a state in which the observation field of view is unlikely to change once it is changed, as in a microscope image, and does not assume a state in which the distance to the observation target changes frequently, as in an endoscope. For example, if the folds of an organ are reflected on the edge of the screen during endoscopic observation and part of the image is halated, the device will operate in a fast tracking mode, and will track unintended brightness fluctuations, such as halation on the edge of the image, and dimming control will be performed to darken the image even if the observation target is at an appropriate brightness, making it impossible for the user to observe at an appropriate brightness.

[0007] An object of the present invention is to provide an endoscope system and an operating method thereof that can capture images at appropriate brightness in a state in which the distance to the object of observation frequently changes. [Means for solving the problem]

[0008] The endoscopic system of the present invention includes a processor that performs exposure control based on an endoscopic image captured by an endoscope equipped with an imaging element, calculates brightness information indicating the degree of brightness of the peripheral portion of the endoscopic image, and controls the tracking speed of the exposure control based on the brightness information.

[0009] It is preferable that the processor calculates a reduction coefficient for reducing the amount of change or the rate of change of the exposure in the exposure control based on the brightness information, and applies the reduction coefficient to the exposure control to control the tracking speed.

[0010] It is preferable that the processor determines the reduction coefficient according to a comparison result between past brightness information, which is past brightness information, and the brightness information.

[0011] It is preferable that the processor calculates a reduction coefficient when the comparison result indicates that the brightness information is greater than the past brightness information.

[0012] It is preferable that, when the comparison result indicates that the brightness information is equal to or lower than the previous brightness information, the processor sets the reduction coefficient to a lower limit value.

[0013] The processor preferably holds a pre-change suppression coefficient that is the suppression coefficient used in calculating the tracking speed before the change, and corrects the suppression coefficient if the suppression coefficient is smaller than the pre-change suppression coefficient.

[0014] As a correction, the processor preferably changes the following speed so as to gradually approach the reference state.

[0015] It is preferable that, when the reduction coefficient becomes equal to or less than a preset threshold value, the processor sets the reduction coefficient to a lower limit value.

[0016] It is preferable that the processor updates the past brightness information using the calculated brightness information and the multiple pieces of past brightness information stored therein.

[0017] It is preferable that the processor calculates the brightness information from a difference in brightness between a central portion of the endoscopic image and a peripheral portion of the endoscopic image.

[0018] The processor preferably determines the brightness information based on the amount of high brightness pixels, which are pixels having a brightness value equal to or greater than a preset threshold.

[0019] As the exposure control, the processor preferably changes at least one of the amount of illumination light and the imaging parameters of the imaging element based on the brightness information.

[0020] The operation method of the endoscopic system of the present invention includes the steps of capturing an endoscopic image based on exposure control, calculating brightness information indicating the degree of brightness of the peripheral portion of the endoscopic image, and controlling the tracking speed of the exposure control in accordance with the brightness information. Effect of the Invention

[0021] According to the present invention, imaging can be performed with appropriate brightness even in a state in which the distance to the observation target frequently changes. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram of an endoscope system. [Diagram 2] 2 is a block diagram showing the functions of the endoscope system. FIG. [Diagram 3] 11 is an explanatory diagram illustrating how brightness information is calculated by dividing an endoscopic image into a central image and a peripheral image. FIG. [Figure 4] 13A is an explanatory diagram showing classification according to the luminance values ​​of pixels in a central image, and FIG. 13B is an explanatory diagram showing classification according to the luminance values ​​of pixels in a peripheral image. [Diagram 5] 11 is an explanatory diagram for calculating the difference between the number of high luminance pixels in a peripheral image and the number of high luminance pixels in a central image; FIG. [Figure 6] FIG. 11 is an explanatory diagram for comparing brightness information and updating past brightness information in each control cycle. [Figure 7] 11 is an explanatory diagram showing the relationship between the suppression coefficient used in the tracking speed of the exposure amount control and brightness information; [Figure 8] FIG. 1A is an explanatory diagram of a time series relating to a control cycle in endoscopic observation, FIG. 1B is an explanatory diagram showing the relationship between the exposure and the control cycle in exposure control in normal mode, and FIG. 1C is an explanatory diagram showing the relationship between the exposure and the control cycle using a suppression coefficient in tracking control mode. [Figure 9] FIG. 13A is an explanatory diagram showing a change in the ratio of the follow-up speed to the reference speed for each control cycle when the reduction coefficient is decreased, and FIG. 13B is an explanatory diagram showing a change in the reduction coefficient for each control cycle. [Figure 10] 5 is a flowchart showing a series of steps for controlling the amount of exposure depending on the tracking speed according to the present invention. [Figure 11] 13A is an explanatory diagram of a peripheral image in which the peripheral portion is set narrower than in the embodiment as a modified example, and FIG. 13B is an explanatory diagram of a peripheral image in which the peripheral portion is set wider than in the embodiment as a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 1, an endoscope system 10 according to an embodiment of the present invention includes an endoscope 11, a light source device 12, a processor device 13, a display 14, and a user interface (UI) 15. The endoscope 11 is optically connected to the light source device 12 and electrically connected to the processor device 13. The light source device 12 supplies illumination light to the endoscope 11.

[0024] The endoscope 11 illuminates the observation target with illumination light, captures an image of the observation target, and acquires an endoscopic image. The endoscope 11 has an insertion section 11a that is inserted into a living body (inside a subject) having an observation target, and an operation section 11b that is provided at the base end portion of the insertion section 11a. A bending section 11c and a tip section 11d are provided at the tip side of the insertion section 11a. The bending section 11c is bent in a desired direction by operating the operation section 11b. The tip section 11d irradiates the observation target with illumination light, and receives reflected light from the observation target to capture an image of the observation target. The operation section 11b is provided with a mode changeover switch 11e that is used for switching modes.

[0025] The processor device 13 is electrically connected to the display 14 and the user interface 15. The processor device 13 receives an image signal from the endoscope 11 and performs various processes based on the image signal. An external recording medium (not shown) for recording images and image information, etc. may be connected to the processor device 13. The display 14 outputs and displays images and image information of the observation target that have been image-processed by the processor device 13. The user interface 15 has a keyboard, a mouse, a touchpad, a microphone, a foot pedal, etc., and has a function of accepting input operations such as function settings.

[0026] The endoscope system 10 is capable of performing normal observation for observing an observation site and special observation for emphasizing a specific structure in the observation site. In special observation, multiple frames including a frame in which illumination light of a specific wavelength is irradiated to emphasize a specific structure are captured to generate one observation image. The generated observation image is displayed on the display 14. Note that, unless otherwise specified, normal observation is performed in normal mode and exposure control in tracking control mode.

[0027] As shown in FIG. 2, in the endoscopic system 10, the light source device 12 transmits emitted illumination light to the endoscope 11 via a light guide 29, and the endoscope 11 transmits an image signal captured using the illumination light to the processor device 13, and the processor device 13 generates an image to be displayed on the display 14.

[0028] The light source device 12 includes a light source section 20 that emits one or more illumination lights, and a light emission control section 22 that generates a drive current (drive signal) that controls the light emission timing and light emission amount of the light source section 20, and supplies the drive current (drive signal) to the light source section 20 to emit light. The function of the light emission control section 22 is realized by a light source control processor (not shown) included in the light source device 12, and controls the emitted illumination light by supplying a drive current (drive signal) that controls the light emission timing and light amount of the illumination light to the light source section 20 in response to receiving a light emission control signal. Note that when the light source device 12 and the processor device 13 are electrically connected, the function of the light source control processor may be realized by a central control section instead of the light source control processor.

[0029] In the light source device 12, the light emission control unit 22 controls light emission and light amount according to the drive current transmitted to the light source unit 20. The amount of light emitted is determined by the drive current value. The light emission control unit 22 stores a target light emission amount and a target light emission timing, or receives input from the processor device 13. The light emission amount indicates the amount of light output emitted per unit time.

[0030] In the light emission in one frame, brightness information based on the endoscopic image can be calculated as the amount of light received by the image sensor 44. The light emission in each frame can be controlled to stop when a preset amount of light required for imaging is reached, thereby enabling imaging at a brightness suitable for observation. When the light source 25 emits light, a drive current having a predetermined drive current value is transmitted from the light emission control unit 22 to the light source 25, and the light source 25 emits light at an amount of light corresponding to the drive current. The amount of light emission and the drive current value are in a proportional relationship.

[0031] Light emitted by the light source unit 20 is incident on the light guide 29. The light guide 29 is built into the endoscope 11 and a universal cord (a cord that connects the endoscope 11 with the light source device 12 and the processor device 13). The light guide 29 propagates light from the light source unit 20 to the tip 11d of the endoscope 11.

[0032] The tip 11d of the endoscope 11 is provided with an illumination optical system 30 and an imaging optical system 40. The illumination optical system 30 has an illumination lens 32, and illumination light propagated by the light guide 29 is irradiated onto the observation object via the illumination lens 32. The imaging optical system 40 has an objective lens 42 and an imaging sensor 44. Reflected light of the illumination light returning from the observation object irradiated with the illumination light is incident on the imaging sensor 44, which is a color imaging sensor, via the objective lens 42. As a result, an image of the observation object is formed on the imaging sensor 44.

[0033] The imaging sensor 44 may be a photoelectric conversion element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal-Oxide Semiconductor) sensor. The imaging sensor 44 performs, for example, a storage operation of photoelectrically converting received light and storing a signal charge according to the amount of received light for each pixel within an acquisition period of one frame, and a readout operation of reading out the stored signal charge. The signal charge for each pixel read out from the imaging sensor 44 is converted into a voltage signal and input to a CDS / AGC (Correlated Double Sampling / Automatic Gain Control) circuit 46. The light source device 12 generates illumination light in accordance with the timing of the storage operation of the imaging sensor 44, and causes the illumination light to enter the light guide 29.

[0034] Each pixel of the image sensor 44 is provided with either a B pixel (blue pixel) having a B (blue) color filter, a G pixel (green pixel) having a G (green) color filter, or an R pixel (red pixel) having an R (red) color filter. For example, the image sensor 44 is preferably a color image sensor with a Bayer array in which the ratio of the number of B pixels, G pixels, and R pixels is 1:2:1.

[0035] The B color filter transmits mainly light in the blue band, specifically light with a wavelength band of 380 to 560 nm (blue transmission band). The peak wavelength at which the transmittance is maximum is around 460 to 470 nm. The G color filter transmits mainly light in the green band, specifically light with a wavelength band of 450 to 630 nm (green transmission band). The R color filter transmits mainly light in the red band, specifically light with a wavelength band of 580 to 760 nm (red transmission band).

[0036] Also, a complementary color image sensor equipped with complementary color filters of C (cyan), M (magenta), Y (yellow) and G (green) may be used instead of the primary color image sensor 44. When a complementary color image sensor is used, image signals of four colors, CMYG, are output, and by converting the four color image signals of CMYG into three color image signals of RGB by complementary color-primary color conversion, image signals of each color of RGB similar to those of the image sensor 44 can be obtained.

[0037] The imaging control unit 45 drives and controls the imaging sensor 44 in response to instructions from the mode changeover switch 11e and the user interface 15 via the processor device 13, and signals from the light emission control unit 22, switches between normal mode and tracking control mode for exposure control, and controls imaging in each mode. In controlling imaging, the imaging control unit 45 adjusts the exposure period by setting the shutter speed of an electronic shutter (not shown) of the imaging sensor 44. It also transmits a control signal to the light emission control unit 22 to control the amount and timing of illumination light emitted by the light source device 12. Instructions from the user interface 15 include settings using a menu screen or operation buttons displayed on the display 15. In addition, internal parameters such as an upper limit value of the emitted light amount determined by the type of scope in the endoscope 11 may be used for exposure control.

[0038] The CDS / AGC circuit 46 performs correlated double sampling (CDS) and automatic gain control (AGC) on the analog image signal obtained from the image sensor 44. The image signal passed through the CDS / AGC circuit 46 is converted into a digital image signal by an A / D (Analog / Digital) converter 48. The digital image signal after A / D conversion is input to the processor device 13.

[0039] In the processor device 13, programs related to each process are incorporated in a program memory (not shown). A central control unit (not shown) constituted by a processor executes the programs in the program memory to realize the functions of an image signal acquisition unit 50, a DSP (Digital Signal Processor) 51, a noise reduction unit 52, an image processing unit 53, an output control unit 54, and an exposure amount control unit 60. In addition, the exposure amount control unit 60 has the functions of a brightness information calculation unit 61, a brightness information holding unit 62, a brightness information comparison unit 63, a suppression coefficient calculation unit 64, a tracking pattern determination unit 65, and a brightness information update unit 66.

[0040] The image signal acquisition unit 50 receives an image signal input from the endoscope 11 driven and controlled by the imaging control unit 45, and transmits the received image signal to the DSP 51. The output control unit 54 transmits the image signal of the image to be displayed, acquired from the image processing unit 53, to the display 14.

[0041] The DSP 51 performs various signal processing such as defect correction, offset processing, gain correction, linear matrix processing, gamma conversion, demosaic processing, and YC conversion processing on the received image signal. In the defect correction processing, signals from defective pixels of the imaging sensor 44 are corrected. In the offset processing, dark current components are removed from the image signal that has been subjected to the defect correction processing, and an accurate zero level is set. In the gain correction processing, the signal level of each image signal is adjusted by multiplying the image signal of each color after the offset processing by a specific gain. The image signal of each color after the gain correction processing is subjected to linear matrix processing to improve color reproducibility.

[0042] Then, the brightness and saturation of each image signal are adjusted by gamma conversion processing. The image signals after the linear matrix processing are subjected to demosaic processing (also called isotropic processing or synchronization processing), and signals of the missing colors of each pixel are generated by interpolation. Through the demosaic processing, all pixels have signals of each of the RGB colors. The DSP 51 performs YC conversion processing on each image signal after the demosaic processing, and outputs a luminance signal Y and color difference signals Cb and Cr to the noise reduction unit 52.

[0043] The noise reduction unit 52 performs noise reduction processing, for example, by a moving average method, a median filter method, etc., on the image signal that has been subjected to demosaic processing, etc. by the DSP 51. The image signal with the noise reduced is input to the image processing unit 53.

[0044] The image processing unit 53 performs color conversion processing such as 3×3 matrix processing, tone conversion processing, and 3D LUT (Look Up Table) processing on one frame of image signals input from the noise reduction unit 52. Then, various color enhancement processing is performed on the RGB image data that has been color converted. Then, structure enhancement processing such as spatial frequency enhancement is performed on the RGB image data that has been color enhanced. The RGB image data that has been subjected to structure enhancement processing is input to the output control unit 54 as an observation image.

[0045] The output control unit 54 sequentially acquires the observation images from the image processing unit 53 and converts them into video signals that enable full-color display on the display 14. The converted video signals are output and displayed on the display 14. This allows a doctor or the like to observe the subject using still or moving images of the observation images.

[0046] The exposure control unit 60 calculates brightness information for the observation image generated by the image processing unit 53, and performs exposure control according to the brightness information. The exposure control is performed by performing at least one of light emission control of the light source device 12 and light reception control of the endoscope 11. A light emission control signal is transmitted to the light emission control unit 22 and an imaging control signal is transmitted to the imaging control unit 45 via the output control unit 54.

[0047] In the exposure amount control, at least one of the amount of illumination light emitted from the light source unit 20 and the imaging parameters of the imaging element of the imaging sensor 44 is changed based on the brightness information. It is also preferable to control the light emission timing and the exposure time. When changing the imaging parameters, if the exposure amount is to be reduced, the sensitivity of the imaging element is weakened or the exposure time is shortened. The length of the exposure time is adjusted, for example, by changing the shutter speed of the electronic shutter to change the length of the imaging frame. It is also preferable that the opening and closing of the shutter is controlled in synchronization with the imaging frame.

[0048] The brightness information calculation unit 61 calculates an evaluation value that can convert the brightness in the endoscopic image generated by the image processing unit 53 into a numerical value or a comparable graded evaluation value. The brightness of each pixel in the endoscopic image is calculated to create brightness distribution data. It is preferable that the brightness is evaluated in 256 steps. Instead of the brightness, a 10-step evaluation of brightness may be used. The calculation of the brightness information is linked to the acquisition timing of the observation image generated from the frame images, but the calculation does not have to be performed for each frame, and it may be performed once for multiple frames.

[0049] The brightness information storage unit 62 stores the calculated brightness information as past brightness information. The past brightness information is used for comparison in the brightness information comparison unit 63. The past brightness information may be calculated brightness information stored individually, or calculated and stored by the brightness information update unit 66 using multiple pieces of brightness information. In addition, a predetermined value of brightness information to be used for comparison when no past brightness information has been accumulated is also stored.

[0050] The brightness information comparison unit 63 compares the calculated brightness information with a predetermined value or past brightness information. In the comparison, the brightness information calculated by the brightness information calculation unit 61 and the predetermined value or past brightness information stored in the brightness information storage unit 62 are used.

[0051] The reduction coefficient calculation unit 64 calculates a reduction coefficient based on the brightness information comparison result. The reduction coefficient is a coefficient that delays the tracking speed in exposure control, and the larger the reduction coefficient, the slower the tracking speed. If the calculated brightness information is not brighter than a predetermined value or the past brightness information, the reduction coefficient is reset to a lower limit value. The predetermined value is a preset threshold value, etc. If it is determined that the calculated brightness information is brighter than the predetermined value or the past brightness information, a reduction coefficient is calculated based on the comparison result.

[0052] The tracking pattern determination unit 65 determines a tracking pattern for exposure control based on the suppression coefficient calculated by the suppression coefficient calculation unit 64. When the suppression coefficient is 1, there is no delay correction, and exposure control is performed in a reference state with a tracking pattern similar to that of normal observation. The tracking speed is changed every time a suppression coefficient is obtained from the suppression coefficient calculation unit 64, but even after the tracking speed is changed, the pre-change suppression coefficient, which is the suppression coefficient used to calculate the tracking speed before the change, is held. If the newly obtained suppression coefficient is smaller than the pre-change suppression coefficient, the suppression coefficient is corrected. The correction is performed by changing the tracking speed to gradually approach the reference state.

[0053] The brightness information update unit 66 updates the past brightness information using the calculated brightness information. The past brightness information is updated using the brightness information calculated by the brightness information calculation unit 61 and a plurality of pieces of past brightness information stored in the brightness information storage unit 62. For example, the information is updated using an infinite impulse response calculated using an IIR (Infinite Impulse Response) filter. In addition, a moving average of previously calculated brightness information or only the brightness information calculated immediately before may be used as the past brightness information.

[0054] An example using the endoscope system 10 of the present embodiment described above will be described. The exposure control unit 60 has two types of observation modes: a normal mode in which the exposure is controlled at a fixed tracking speed to perform observation, and a tracking control mode in which the exposure is controlled at a tracking speed based on calculated brightness information to perform observation. The observation mode is arbitrarily switched by a user operation on any of the endoscope 11, the processor device 13, or the light source device 12.

[0055] In normal mode, a normal observation image is captured with an exposure appropriate for observing the entire observation area. In normal observation, the light is continuously turned on during observation, and the exposure period is adjusted by opening and closing the shutter, etc. In normal mode, exposure control is performed at a fixed tracking speed in the reference state based on brightness information. In tracking control mode, exposure control is performed at a tracking speed based on a suppression coefficient calculated from the brightness information.

[0056] In the tracking control mode, the exposure control is performed based on the endoscopic image captured by the endoscope 11, brightness information indicating the degree of brightness of the endoscopic image is calculated, and the tracking speed of the exposure control is changed based on the brightness information. The brightness information is calculated using, for example, the luminance value of pixels in the endoscopic image.

[0057] The suppression coefficient used to change the tracking speed is determined using past brightness information, so the tracking speed in the tracking control mode immediately after switching is set to a reference state in which there is no delay similar to that in the normal mode, and resetting the tracking speed, which will be described later, refers to changing to the reference state. The suppression coefficient in the reference state is the lower limit of 1. The suppression coefficient is calculated based on the brightness information, and the calculated suppression coefficient is applied to the exposure control to control the tracking speed. For example, the tracking speed is delayed from the reference state. The suppression coefficient is determined according to a comparison result obtained by comparing past brightness information, which is past brightness information, with the calculated brightness information. If the comparison result shows that the brightness information is greater than the past brightness information, the suppression coefficient is calculated. The suppression coefficient is used to suppress the amount of change or the rate of change of the exposure in the exposure control.

[0058] In the tracking control mode, brightness information of the captured endoscopic image is calculated, and the tracking speed of the exposure control is changed in accordance with the brightness information. The tracking speed is delayed with respect to the reference state based on a suppression coefficient calculated using the brightness information.

[0059] As shown in Fig. 3, brightness information is calculated using an endoscopic image 70 captured by an endoscope 11. In calculating the brightness information, the exposure control unit 60 uses the luminance value of each pixel of an endoscopic image divided into two regions. The two regions are a central image 70a obtained by extracting the central region from the endoscopic image 70 and a peripheral image 70b obtained by extracting the peripheral region, and the brightness information is calculated using the difference in the number of high-luminance pixels as the difference in brightness between the central image 70a and the peripheral image 70b. It is preferable that the area ratio of the central image 70a and the peripheral image 70b is 1:1, i.e., that they have the same number of pixels.

[0060] By comparing the brightness information of the entire endoscopic image 70 or the central image 70a with the peripheral image 70b, it is possible to appropriately determine the exposure amount control by determining the situation such as when only the peripheral area is clearly bright, when a foreign object such as a highly reflective fold is captured, etc. The brightness information is determined based on the amount of high brightness pixels, which are pixels having a brightness value equal to or higher than a preset high brightness determination threshold.

[0061] As shown in FIG. 4, the brightness information calculation unit 61 determines the brightness value of each pixel of the central image 70a and the peripheral image 70b extracted from each endoscopic image 70. The brightness value takes any value from 0 to 255 in 256 gradations, and the brighter it is, the higher the value. FIG. 4(A) is a histogram showing the distribution of brightness values ​​in the central image 70a, with the vertical axis representing the number of pixels and the horizontal axis representing the brightness value. In the histogram, the brightness values ​​are classified into eight levels. FIG. 4(B) is a histogram showing the distribution of brightness values ​​in the peripheral image 70b, and can be compared with FIG. 4(A). The pixels classified into the group with the highest brightness value in each histogram are determined as high brightness pixels.

[0062] For example, in Fig. 4(A), when pixel values ​​of the central image 70a are divided into eight groups A1 to A8, group A1 is classified into 0 to 34, group A2 into 35 to 69, group A3 into 70 to 104, group A4 into 105 to 139, group A5 into 140 to 174, group A6 into 175 to 209, group A7 into 210 to 244, and group A8 into 245 to 255. Pixels classified into group A8, i.e., pixels with a luminance value of 224 or more, may be regarded as high luminance pixels. The division interval may be divided into smaller equal parts than eight.

[0063] 4B, the pixel values ​​of the peripheral image 70b are grouped in the same manner as in the central image 70a: group B1 corresponds to group A1, group B2 to group A2, group B3 to group A3, group B4 to group A4, group B5 to group A5, group B6 to group A6, group B7 to group A7, and group B8 to group A8.

[0064] Comparison based on the distribution of luminance values ​​can be used not only to distinguish foreign bodies, which will be described later, but also for normal light amount control in the progress of endoscopic observation. For example, if the distribution has a large number of pixels in groups A1 to A3 and groups B1 to B3, it can be determined that the exposure amount of the entire endoscopic image 70 is insufficient, and control is performed to increase the amount of light emitted from the light source unit 20 or to change the imaging parameters so as to increase the light receiving sensitivity in the imaging optical system 40.

[0065] Instead of grouping, a high luminance discrimination threshold may be set to define pixels having a luminance value of 245 or more or pixels having a luminance value of 250 or more as high luminance pixels, and pixels having a luminance value equal to or more than the high luminance discrimination threshold may be simply defined as high luminance pixels. The high luminance discrimination threshold may be changed by the user through an operation via the user interface 15.

[0066] As shown in FIG. 5, the brightness information D(n) of the endoscope image 70 can be determined from the difference value between Xa, which is the number of high-brightness pixels in the central part, and Xb, which is the number of high-brightness pixels in the edge part. The brightness information D(n) is the difference value calculated in the nth brightness information calculation in the tracking control mode. The number of pixels of A8 in FIG. 4(A) is defined as the number of high-brightness pixels in the central part image 70a, which is the number of central high-brightness pixels, and the number of pixels of B8 in FIG. 4(B) is defined as the number of high-brightness pixels in the edge part image 70b, which is the number of edge high-brightness pixels. When the number of central high-brightness pixels is Xa and the number of edge high-brightness pixels is Xb, the brightness information D(n) is the value of Xb - Xa. The larger the value of the brightness information D(n) is and it is a positive number, the more it can be determined that the edge part of the endoscope image 70 is brighter than the central part.

[0067] In order to determine that the edge part image 70b is brighter than the central part image 70a, in addition to the brightness information D(n) being a positive number (0 < D(n)), it is preferable to provide a criterion for determining whether it is a significant brightness based on the number of pixels of the endoscope image 70. For example, when the value of the brightness information D(n), which is the difference value, is less than 1% of the number of pixels of the endoscope image 70, it is determined that it is not a significant brightness and approximated to D(n) = 0.

[0068] A suppression coefficient is calculated to suppress the exposure control that follows unintentional brightness fluctuations such as halation that occurs when a foreign object is captured. Based on the condition that the brightness information D(n), in which the number of high-brightness pixels in the edge part image 70b is larger than that in the central part image 70a, is a positive number and brighter than the past brightness information, the calculation of the suppression coefficient used in the tracking pattern is performed.

[0069] As shown in Fig. 6, in the brightness information comparison, the calculated brightness information is compared with the past brightness information updated in the previous control cycle. In the tracking control mode, the control cycle is a cycle in which brightness information for an endoscopic image is calculated, a suppression coefficient is calculated, the tracking speed is changed, and the brightness information is updated, and exposure control is performed. Immediately after switching to the tracking control mode, that is, the control cycle T(1) is the first brightness information calculation, the next is control cycle T(2), and the next is control cycle T(3), and each control cycle T(n) is the nth brightness information calculation, which is an arbitrary number of times.

[0070] The past brightness information that is updated and held in the control cycle T(n) is set as past brightness information Dp(n). That is, in the control cycle T(n), the calculated brightness information D(n) is compared with the past brightness information Dp(n-1) that is a comparison value, and whether or not to calculate the reduction coefficient is determined according to the comparison result. However, since the past brightness information Dp(n) is not held in the control cycle T(1), a predetermined value is used as the comparison value. Also, since the past brightness information Dp(n) uses a larger number of calculated brightness information D(n) as the value of n increases, the comparison with the predetermined value may be performed even when the number of control cycles T(n) is equal to or less than a preset reference number. The predetermined value is brightness information measured by other endoscopic observations, etc.

[0071] The brightness information used in the comparison is used to update the past brightness information. The past brightness information is updated, for example, by using an infinite impulse response using an IIR filter. In the infinite impulse response, the brightness information calculated in the control cycle T(n) is D(n), and the past brightness information updated in the control cycle T(n) is the past brightness information Dp(n), using the following formula (1). Dp(n)=(D(n)÷4)+(3Dp(n-1)÷4) (1)

[0072] As shown in formula (1), the past brightness information Dp(n) updated in the control cycle T(n) is the sum of one-fourth of the brightness information calculated in the control cycle T(n) and three-fourths of the past brightness information Dp(n-1) updated in the control cycle T(n-1). As a result, even if an endoscopic image 70 with halation is continuously acquired in the control cycle T(n+1), it can be determined that the image is brighter than the past brightness information each time, and when an endoscopic image 70 without halation is acquired, it can be determined that the image is not brighter than the past brightness information. Regardless of the result of the determination, the calculation and update of the past brightness information Dp(n+1), which is the update value, is performed.

[0073] If the difference value D(n) is brighter than the past brightness information, that is, the brightness information calculation of the control cycle T(n), satisfies the following formula (2), the reduction coefficient is calculated. D(n)-Dp(n-1)>0 (2)

[0074] If the above formula (2) is satisfied and the comparison determines that the brightness information D(n) is brighter than the past brightness information Dp(n-1), the comparison result is used to calculate the reduction coefficient. If the above formula (2) is not satisfied and the brightness information is not determined to be brighter than the past brightness information, the reduction coefficient is set to the lower limit of 1. Resetting the reduction coefficient refers to changing the reduction coefficient to 1. On the other hand, if the brightness information D(n) is a number equal to or less than 0, or the brightness information based on the brightness information D(n) is equal to or less than the past brightness information, the reduction coefficient is set to the lower limit of 1.

[0075] As shown in FIG. 7, the calculation of the suppression coefficient C for determining the tracing pattern uses the brightness information D(n). The suppression coefficient C is calculated when the brightness information D(n) has a predetermined range between a lower limit threshold Ds and an upper limit threshold De. When the brightness information D(n) is equal to or less than the lower limit threshold Ds, the suppression coefficient C is the lower limit value of 1, and the exposure amount control is performed with the same tracing pattern as in the normal mode. The lower limit threshold Ds is a value for determining that the peripheral image 70b is brighter than the central image 70a, and the upper limit threshold De is a value for determining that the peripheral image 70b does not cause halation. In the range between the lower limit threshold Ds and the upper limit threshold De, the suppression coefficient C is calculated using a proportional relationship in which the suppression coefficient C becomes larger as the value of the brightness information D(n) increases. The suppression coefficient C is a coefficient for suppressing the amount of change or the rate of change of the exposure amount in the exposure amount control.

[0076] The reduction coefficient C has a maximum value of a preset Cmax, and when the brightness information D(n) is equal to or greater than the upper threshold De, the calculated reduction coefficient C is uniformly set to Cmax. When the brightness information D(n) is smaller than the lower threshold Ds of the proportional range, the reduction coefficient C is set to 1, and when the brightness information D(n) is larger than the upper threshold De of the proportional range, the reduction coefficient C is set to Cmax. The larger the value of the reduction coefficient C, the more gradual the change in exposure caused by exposure control. Also, even if the brightness information D(n) is a value outside the proportional range, the control content of the exposure changes.

[0077] The suppression coefficient C is for suppressing the exposure control, not for stopping the exposure control, so the maximum value Cmax of the suppression coefficient C is a value that causes the exposure control to be performed with the determined tracing pattern at least once before the next control cycle. For example, when brightness information calculation is performed every second, the value is a value that causes the exposure control to be performed with the determined tracing pattern at least once per second. The value of Cmax varies depending on the imaging conditions and the performance of the endoscope system 10.

[0078] It is preferable to calculate the brightness information every time the endoscopic image 70 is acquired, but since it is affected by the frame rate as well as the performance and imaging conditions of the devices constituting the endoscopic system 10, it may be possible to image a plurality of frames during one control cycle T(n), for example, by calculating the reduction coefficient C every five frames of the endoscopic image 70. In addition, the reduction coefficient C may be determined based on a conversion table (not shown) calculated in advance that is different from the relationship shown in FIG.

[0079] The determined reduction coefficient C is applied to control the amount of exposure, and the amount of exposure to be changed during exposure control can also be determined using high luminance pixels. For example, the brightness of the endoscopic image 70 may be determined by calculating the total value of high luminance pixels such as Xa+Xb in calculating the brightness information D(n). In addition, the degree of excess or deficiency of the amount of exposure for the endoscopic image 70 can be determined from changes in the distribution of the histograms in Figures 4(A) and 4(B). If the number of pixels in the high luminance group decreases and the number of pixels in the low luminance group increases, it can be determined that the endoscopic image 70 is insufficiently exposed and is a dark image.

[0080] As shown in Fig. 8, exposure control in the case where a large number of high-luminance pixels occur in the peripheral image 70b due to halation during real-time observation will be described. Fig. 8(A) shows the transition of control cycles in which a foreign body M appears in the endoscopic image 70 in control cycles T(n+1) and T(n+2), Fig. 8(B) is a graph showing the relationship between the exposure (vertical axis) and the transition of the control cycle (horizontal axis) in the normal mode corresponding to Fig. 8(A), and Fig. 8(C) is a graph showing the relationship between the exposure (vertical axis) and the transition of the control cycle (horizontal axis) in the tracking control mode corresponding to Fig. 8(A).

[0081] 8(A), the control cycles T(n+1) and T(n+2) at which an endoscopic image 71 that includes a foreign object M is captured, and the control cycle T(n+3) at which an endoscopic image 70 that does not include a foreign object M is captured are designated as control cycle T(n+3). The control cycle following control cycle T(n+3) is T(n+4), and continues thereafter. In T(n), nothing that would cause an adjustment to the exposure amount during observation, such as a foreign object M, is captured, and the exposure amount is set to a reference value for an average state.

[0082] The transition of the exposure amount in the normal mode of Fig. 8(B) and the tracking control mode of Fig. 8(C) will be explained using a reference value and an adjustment value, which is the value of the exposure amount set based on the brightness information. The reference value of the exposure amount is set to the exposure amount in the control cycle T(n) in which the endoscopic image 70 before the control cycle T(n+1) in which no foreign object M is captured and no specific exposure amount control operation is performed. In other words, the exposure amount will be explained in terms of a relative change amount. Note that the control of the exposure amount due to the change in reflectance for each imaging part will be omitted.

[0083] In the control cycle T(n+1) of the normal mode in FIG. 8(B), the exposure amount is reduced with respect to the reference value based on the brightness information of the endoscopic image 71 in which the foreign matter M is captured. For example, it is adjusted to 20%. In the control cycle T(n+2), an image is captured with the exposure amount adjusted in the control cycle T(n+1) and brightness information is calculated. Since an image is captured with the exposure amount corresponding to the foreign matter M, if the brightness distribution for each pixel is appropriate in the brightness information calculation, the exposure amount adjusted in the control cycle T(n+1) is maintained. Note that the exposure amount during halation is appropriately adjusted to 10%, 25%, etc. depending on the situation.

[0084] In the endoscopic image 70 captured in control cycle T(n+3), the imaging range has moved and the foreign object M is no longer captured, and the brightness value of the endoscopic image 70 is generally low. Therefore, the exposure amount is adjusted to have an appropriate distribution. For example, the exposure amount is changed to be the same as that of control cycle T0. If there is no foreign object in control cycle T(n+4), the exposure amount is not reduced.

[0085] In the normal mode, the exposure control is performed for each control cycle, so that the value of the brightness information D(n) of the endoscopic image 70 increases suddenly, for example, when halation occurs due to the foreign matter M, and the exposure control is performed accordingly. In that case, the exposure control becomes extreme in a short period of time, which may place a heavy burden on the equipment and shorten the life of the parts. In addition, the endoscopic image 70 acquired by imaging with the exposure control according to the foreign matter M may become unsuitable for observation.

[0086] 8(C), in the control cycle T(n+1), the calculation of the suppression coefficient C and the exposure amount control are performed based on the brightness information of the endoscopic image 70 in which the foreign body M is captured. If the maximum value Cmax of the suppression coefficient C for halation is 4, the tracking speed (tracking rate) of the exposure amount control becomes 1 / 4 of that in the normal mode, and the exposure amount during imaging in the control cycle T(n+2) becomes 0.8 because the change is 1 / 4 of that in the normal mode.

[0087] If halation also occurs in control cycle T(n+2), the brightness information D(n+2) is higher than the past brightness information Dp(n+1) and is equal to or greater than the upper limit threshold De, and the suppression coefficient C becomes the maximum value Cmax of 4, just like in control cycle T1. In that case, the exposure amount during imaging in control cycle T(n+3) is 0.6.

[0088] On the other hand, in the case where no halation occurs in the image capture in the control cycle T(n+3), the brightness information D(n+3) is lower than the past brightness information Dp(n+2), so the suppression coefficient C is reset and normal exposure control is performed. That is, the exposure is returned to a state in which the foreign matter M is not captured by the time of the image capture in the next control cycle T(n+4). Therefore, the exposure is increased.

[0089] In the tracking control mode, it takes longer for the exposure amount to decrease from 1.0 to 0.2 than in the normal mode, depending on the value of the suppression coefficient C. For example, in the case of FIG. 8(C), if the endoscopic image 71 in a halation state is continuously captured in the control cycles T(n+3) to T(n+4), the exposure amount will be 0.2 when the image is captured in the control cycle T(n+5). If the endoscopic image 71 is detected in the control cycle T(n+5), the exposure amount may further decrease, but will not become 0.

[0090] A control cycle is a set of image acquisition, brightness information calculation, brightness information comparison, suppression coefficient calculation, exposure control, and past brightness information update. Fig. 8(C) shows the change in exposure when the maximum value Cmax of the suppression coefficient C to be changed is set to 4.0. On the other hand, the method of increasing the value of Cmax and the exposure, i.e., the tracking pattern, may be appropriately set according to the performance of the endoscope system 10 and the observation situation.

[0091] In changing the tracking speed according to the calculated reduction coefficient C, when the tracking speed approaches 1, a correction can be implemented to gradually decrease the value of the reduction coefficient C. It is preferable to change the correction of the reduction coefficient C in stages, and the amount of change may be divided equally, or the tracking speed may be changed at a specific ratio. This makes it possible to avoid making large changes to the emitted light amount and imaging parameters all at once in exposure control, so that even when the exposure amount is increased, the burden on each device of the endoscope system, such as the light source device 12, the endoscope 11, and the processor device 13, can be reduced.

[0092] In Fig. 9, a stepwise reset of the tracking speed when the suppression coefficient C is Cmax = 4 and the tracking speed is 0.25 in the control cycle T(n) will be described. The suppression coefficient C is reset in a stepwise manner when the calculated brightness information D(n) is not brighter than the past brightness information Dp(n-1). In other words, a correction is performed to gradually bring the tracking speed closer to the reference state. It is preferable to appropriately determine the amount of change at one time using the time until the next control cycle and the number of frames.

[0093] FIG. 9(A) is a graph showing the relationship between the ratio of the tracking speed to the speed in the reference state, which is the inverse of the suppression coefficient (vertical axis), and the progress of the control cycle (horizontal axis). If the speed returns to the original state at equal intervals, for example 0.25, every control cycle, the tracking speed returns to 0.5 in control cycle T(n+1), 0.75 in control cycle T(n+2), and 1.0 in control cycle T(n+3).

[0094] FIG. 9(B) is a graph showing the relationship between the suppression coefficient C (vertical axis) and the transition of the control cycle (horizontal axis), and shows the stepwise change when the suppression coefficient C is reset. Since the following speed is reset to the reference state stepwise at equal intervals, the suppression coefficient C changes in accordance with the following speed. The suppression coefficient C is returned to 2.0 in control cycle T(n+1), 1.33 in control cycle T(n+2), and 1.0 in control cycle T(n+3).

[0095] Instead of the tracking speed, the suppression coefficient C may be decreased by any value. Even in this case, the step of change may be set arbitrarily. Furthermore, since the suppression coefficient C is applied to perform observation at an appropriate brightness, when a value larger than the lower limit is set, a threshold N is set in advance to determine whether the value has an effect on appropriate observation in terms of exposure control. Therefore, when the suppression coefficient C falls below the threshold N, the suppression coefficient C is set to the lower limit. In FIG. 9(B), the threshold N is set to 1.25, but it may be set appropriately to 1.20, 1.10, or the like.

[0096] The control of the light emission control unit 22 and the exposure control unit 60 in the normal mode and the tracking control mode is for single-frame observation using a single light source, but it may be for multi-frame observation in which multiple light sources are turned on or off and the amount of light emitted when turned on is independently controlled. The type and number of light sources vary depending on the light source unit 20.

[0097] In multi-frame observation, multiple illumination lights are switched on and off in a preset pattern, and multi-frame emission is performed. For example, when a first illumination light and a second illumination light are used, one may be a broadband light and the other a special light, or the first illumination light and the second illumination light may be combined to form a broadband light. The wavelength bands of the first illumination light and the second illumination light may be different wavelength bands or may be the same wavelength band.

[0098] Regardless of the light emission pattern, the object to be observed is illuminated with the illumination light of each frame, and captured images are obtained by imaging the image sensor 44, and one observation image is generated using the multiple captured images captured with different illumination lights. In the multi-frame observation mode, one observation image can be generated from captured images of frames in which different illumination lights are continuously emitted, for example, a captured image of the Nth frame and a captured image of the N+1th frame. Note that other methods may be used to generate an observation image from multiple captured images.

[0099] A series of operations in one control cycle in the tracking control mode of this embodiment will be described with reference to the flowchart shown in Fig. 10. The endoscope system 10 sets the observation mode to the tracking control mode, starts exposure control applying a tracking speed based on the reduction coefficient C, and acquires an observation image (step ST100). If the reduction coefficient C has not been calculated, the reduction coefficient C is set as the lower limit, and observation is performed in a reference state with the same tracking speed as in the normal mode. The exposure control unit 60 calculates brightness information from the acquired observation image (step ST110).

[0100] The calculated brightness information is compared with the past brightness information to determine whether it is a higher value than the past brightness information (step ST120). In the comparison of the brightness information, if the calculated brightness information is brighter than the past brightness information (Y in step ST120), a reduction coefficient C is calculated based on the brightness information (step ST130). In the comparison of the brightness information, if the calculated brightness information is not brighter than the past brightness information (N in step ST120), the reduction coefficient C is reset, that is, set to a value that does not cause reduction (step ST140).

[0101] The suppression coefficient C is compared with the suppression coefficient C at the current following speed (step ST150). If the calculated suppression coefficient C is greater than the current suppression coefficient C (Y in step ST150), the suppression coefficient C is set as is. On the other hand, if the calculated suppression coefficient C is smaller than the current suppression coefficient C (N in step ST150), the reduction rate of the suppression coefficient C is set (step ST160).

[0102] The tracking speed in exposure control is changed according to the set reduction coefficient C (step ST170). After the tracking speed is determined, the past brightness information is updated based on the calculated brightness information (step ST180). Observation is performed with exposure control at the changed tracking speed (step ST190). If observation is to be continued in the tracking control mode (Y in step ST200), endoscopic observation is performed with exposure control at the changed tracking speed, and an observation image is captured (step ST100). If observation is not to be continued in the tracking control mode (N in step ST200), the mode is switched from the tracking control mode to the normal mode. Note that endoscopic observation may be ended as is rather than switched to the normal mode.

[0103] In the above embodiment, the exposure control unit 60 calculates brightness information from brightness information D(n) of the number of high-luminance pixels in the central image 70a and the peripheral image 70b. However, exposure control may be performed to calculate brightness information from the ratio of the number of high-luminance pixels in the peripheral image 70b. Below, a modified example in which the brightness information is calculated using the ratio of the number of high-luminance pixels will be described.

[0104] The brightness information is calculated using the ratio of high brightness pixels in the peripheral image 70b to the total image. In the above embodiment, the area ratio of the central image 70a to the peripheral image 70b is 1:1, i.e., the area ratio of the endoscopic image 70 to the peripheral image 70b is 2:1, but the brightness information may be calculated using other area ratios.

[0105] As shown in FIG. 11, the exposure amount is controlled at a tracking speed determined by dividing the area of ​​the endoscopic image 70 to obtain an arbitrary area ratio and calculating brightness information. For example, the area ratio can be set depending on whether to prioritize speed and sensitivity or accuracy in changing the tracking speed. As shown in FIG. 11(A), the area ratio of the endoscopic image 70 to the image peripheral portion is set to 4:1, and the smaller the area occupied by the peripheral portion, the more the change to high-luminance pixels with a small number of pixels affects the brightness information, so that foreign objects that cause halation can be detected in a faster control cycle. On the other hand, as shown in FIG. 11(B), the larger the area occupied by the peripheral portion image 70b, the more pixels that affect the brightness information are required, and the more accurately foreign objects that cause halation can be detected.

[0106] In the above embodiment, the hardware structure of the processing units that execute various processes, such as the light emission control unit 22, the imaging control unit 45, the image signal acquisition unit 50, the DSP 51, the noise reduction unit 52, the image processing unit 53, the output control unit 54, and the exposure control unit 60, is various processors as shown below. The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and functions as various processing units, a GPU (Graphical Processing Unit), a programmable logic device (PLD), which is a processor whose circuit configuration can be changed after manufacture such as an FPGA (Field Programmable Gate Array), and a dedicated electric circuit, which is a processor having a circuit configuration designed exclusively for executing various processes.

[0107] One processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same type or different types (for example, multiple FPGAs, a combination of a CPU and an FPGA, or a combination of a CPU and a GPU, etc.). Also, multiple processing units may be configured with one processor. As an example of configuring multiple processing units with one processor, first, as represented by a computer such as a client or a server, there is a form in which one processor is configured with a combination of one or more CPUs and software, and this processor functions as multiple processing units. Second, as represented by a system on chip (SoC), there is a form in which a processor is used that realizes the functions of the entire system including multiple processing units with one IC (Integrated Circuit) chip. In this way, the various processing units are configured using one or more of the above various processors as a hardware structure.

[0108] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit (Circuitry) in the form of a combination of circuit elements such as semiconductor elements. The hardware structure of the storage unit is a storage device such as a hard disk drive (HDD) or a solid state drive (SSD). From the above description, the endoscope systems described in the following supplementary notes 1 to 12 can be understood.

[0109] [Appendix 1] A processor is provided. The processor, performing exposure control based on an endoscopic image captured by an endoscope having an image sensor; Calculating brightness information indicating a degree of brightness of a peripheral portion of the endoscopic image; An endoscope system that controls a tracking speed of the exposure control based on the brightness information. [Appendix 2] The processor, calculating a suppression coefficient for suppressing an amount of change or a rate of change of the amount of exposure in the exposure control based on the brightness information; 2. The endoscope system according to claim 1, wherein the suppression coefficient is applied to the exposure control to control the tracking speed. [Appendix 3] The processor, An endoscope system according to claim 2, which determines the reduction coefficient according to a comparison result between past brightness information, which is the brightness information in the past, and the brightness information. [Appendix 4] The processor, 4. The endoscope system according to claim 3, wherein, in the comparison result, when the brightness information is greater than the past brightness information, the reduction coefficient is calculated. [Appendix 5] The processor, 5. The endoscope system according to claim 3, wherein, when the brightness information is equal to or lower than the past brightness information in the comparison result, the reduction coefficient is set to a lower limit value. [Appendix 6] The processor, A pre-change suppression coefficient is stored, which is the suppression coefficient used in calculating the following speed before the change; 6. The endoscope system according to claim 2, wherein when the suppression coefficient is smaller than the suppression coefficient before the change, the suppression coefficient is corrected. [Appendix 7] The processor, The endoscope system of claim 6, wherein the correction is performed by gradually changing the tracking speed to approach a reference state. [Appendix 8] The processor, 6. An endoscope system as described in claim 5, wherein when the reduction coefficient becomes equal to or lower than a predetermined threshold value, the reduction coefficient is set to the lower limit value. [Appendix 9] The processor, 9. The endoscope system according to claim 3, wherein the past brightness information is updated using the calculated brightness information and a plurality of pieces of past brightness information stored therein. [Appendix 10] The processor, 10. An endoscopic system according to any one of claims 1 to 9, wherein the brightness information is calculated from a difference in brightness between a central portion of the endoscopic image and a peripheral portion of the endoscopic image. [Appendix 11] The processor, An endoscope system according to any one of appendix 1 to 10, wherein the brightness information is determined based on the amount of high brightness pixels, which are pixels having a brightness value equal to or greater than a preset threshold value. [Appendix 12] The processor 12. The endoscope system according to claim 1, wherein the exposure control is performed by changing at least one of an amount of illumination light and an imaging parameter of the imaging element based on the brightness information. [Explanation of symbols]

[0110] 10 Endoscope System 11 Endoscopy 11a Insertion part 11b Operation section 11c Curved section 11d Tip 11e Mode switch 12 Light source device 13 Processor unit 14 Display 15 User Interface 20 Light source section 22 Light emission control unit 29 Light Guide 30 Illumination optical system 32 Lighting Lens 40 Imaging optical system 42 Objective Lens 44 Image sensor 45 Imaging control section 46 CDS / AGC circuit 48 A / D Converter 50 Image signal acquisition unit 51 DSP 52 Noise reduction section 53 Image processing section 54 Output control section 60 Exposure amount control section 61 Brightness information calculation unit 62 Brightness information storage unit 63 Brightness information comparison section 64 Suppression coefficient calculation unit 65 Tracking pattern determination unit 66 Brightness information update section 70 Endoscopic Images 70a Center image 70b Periphery image 71 Endoscopic images ST100~ST200 steps A1~A8 Group B1~B8 Group D(n) Brightness information M Foreign object N Threshold

Claims

1. A processor is provided. The processor, performing exposure control based on an endoscopic image captured by an endoscope having an image sensor; Calculating brightness information indicating a degree of brightness of a peripheral portion of the endoscopic image; An endoscope system that controls a tracking speed of the exposure control based on the brightness information.

2. The processor, calculating a suppression coefficient for suppressing an amount of change or a rate of change of the amount of exposure in the exposure control based on the brightness information; The endoscope system according to claim 1 , wherein the suppression coefficient is applied to the exposure amount control to control the tracking speed.

3. The processor, The endoscope system according to claim 2 , wherein the suppression coefficient is determined in accordance with a result of comparing the brightness information with past brightness information, which is the brightness information in the past.

4. The processor, The endoscope system according to claim 3 , wherein when the brightness information is greater than the past brightness information in the comparison result, the reduction coefficient is calculated.

5. The processor, The endoscope system according to claim 3 , wherein, in the comparison result, when the brightness information is equal to or lower than the past brightness information, the reduction coefficient is set to a lower limit value.

6. The processor, A pre-change suppression coefficient is stored, which is the suppression coefficient used in calculating the following speed before the change; The endoscope system according to claim 5 , wherein when the suppression coefficient is smaller than the suppression coefficient before change, the suppression coefficient is corrected.

7. The processor, The endoscope system according to claim 6 , wherein the correction is performed by changing the tracking speed so as to approach the reference state in a stepwise manner.

8. The processor, The endoscope system according to claim 5 , wherein when the reduction coefficient becomes equal to or less than a preset threshold value, the reduction coefficient is set to the lower limit value.

9. The processor, The endoscope system according to claim 3 , wherein the past brightness information is updated using the calculated brightness information and a plurality of pieces of past brightness information held.

10. The processor, The endoscope system according to claim 1 , wherein the brightness information is calculated from a difference in brightness between a central portion of the endoscope image and a peripheral portion of the endoscope image.

11. The processor, The endoscope system according to claim 10, wherein the brightness information is determined based on an amount of high-brightness pixels, which are pixels having a brightness value equal to or greater than a preset threshold value.

12. The processor 12. The endoscope system according to claim 1, wherein the exposure control is performed by changing at least one of an amount of illumination light and an imaging parameter of the imaging element based on the brightness information.

13. capturing an endoscopic image based on exposure control; calculating brightness information indicating a degree of brightness of a peripheral portion of the endoscopic image; and controlling a tracking speed of the exposure control in response to the brightness information.

Images