Endoscope system

Abstract

When capturing living tissue as a moving image using a rolling shutter method, an adjustment process having an adjustment level is executed to suppress artifacts generated along lines corresponding to scanning lines of an imaging element within a frame image. An endoscope system comprises: a light source device; an electronic endoscope having an imaging element for capturing living tissue using a rolling shutter method; and a processor having an adjustment unit that adjusts the brightness of the frame image by combining at least one of adjustment of the exposure time of the imaging element, adjustment of the light intensity of the illumination light, and gain adjustment for determining the signal level of the frame image obtained by the imaging element. The adjustment unit determines whether information related to the amount of movement or shaking of a subject image within the captured image satisfies an adjustment condition, and executes the adjustment process by adjusting an adjustment level, whose value indicates the strength of the adjustment process, based at least on the determination result.

Description

Technical Field

[0001] The present invention relates to an endoscope system for displaying images of living tissue in a body cavity. Background Art

[0002] The endoscope system includes: an electronic endoscope having an imaging element for imaging living tissue; a processor having an image processing unit configured to process the image of the captured living tissue to generate a display image; and a monitor configured to be connected to the processor and to display the generated display image.

[0003] In recent years, CMOS image sensors have become increasingly common as imaging elements used in electronic endoscopes. When using CMOS image sensors, a rolling shutter method is used as an exposure / output method for exposing the light-receiving surface of the CMOS image sensor and then outputting the image.

[0004] The rolling shutter method is a method in which the light-receiving surface of the camera element is divided into multiple areas for each scanning line and a time difference is set in each area for exposure. It is also a method in which the accumulated charge is reset in each area, and then the exposed charge is accumulated and the accumulated image signal charge is output (read).

[0005] In imaging elements using this rolling shutter method, since living tissue, the subject, moves slowly, even when exposures are sequentially timed with different exposure times, the subject image rarely shifts at the boundaries of scan lines. However, when droplets of liquid fly around the living tissue at high speed and adhere to the surface of the observation window in front of the imaging element, forming a stream, the droplets or stream move faster than the living tissue. Therefore, in portions of the frame image corresponding to scan line boundaries, the droplet images and the image of the living tissue seen through the stream often shift along the lines corresponding to those scan lines. In other words, the rolling shutter method often produces artifacts along the lines corresponding to the imaging element's scan lines in the frame image.

[0006] To address the above-mentioned problem of droplet images in flight, an endoscope device is known that can prevent the observer from seeing the edge phenomenon, that is, the phenomenon of unnatural edges in the droplet image reflected in the observation image of the endoscope (Patent Documents 1 and 2).

[0007] In the endoscope apparatus, in a frame image captured by a CMOS imaging element, it is determined whether edge formation, i.e., horizontal edges, occurs in the image of scattered droplets. If edge formation occurs, edge formation reduction processing is performed to reduce the edge formation.

[0008] As a processing to reduce the edge phenomenon, the edge phenomenon is reduced by extending the exposure time or performing a blurring process.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-117413

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-117412 Summary of the Invention

[0013] Problems to be solved by the invention

[0014] In the above-mentioned endoscope system, since edge reduction processing is performed after edge detection, edge display on the monitor screen is inevitable. This edge display appears as noise to the surgeon operating the endoscope, and can sometimes lead to misjudgment of living tissue.

[0015] Furthermore, in the above-mentioned endoscope system, if edge blur occurs, extending the exposure time as a measure to mitigate edge blur can cause the image to become too bright, causing discomfort to the surgeon. Therefore, it is necessary to adjust the exposure time without changing the image brightness, but the above-mentioned endoscope system cannot address this issue.

[0016] Furthermore, in the above-mentioned endoscope device, when edge blurring occurs, if blurring is applied only to the edge portion as an edge blurring reduction treatment, the image becomes unnatural, and if blurring is applied to the entire screen, the area to be observed also becomes a blurred image, causing discomfort to the surgeon.

[0017] Therefore, an object of the present invention is to provide an endoscope system that, when capturing living tissue as a moving image using a rolling shutter method, can perform the following processing: processing for suppressing artifacts generated along lines corresponding to scanning lines of a camera element within a frame image; and adjustment processing for adjusting the brightness level without significantly changing the image brightness level.

[0018] Technical solutions to problems

[0019] One aspect of the present invention is an endoscope system for displaying images of living tissue in a body cavity.

[0020] It has:

[0021] a light source device configured to generate illumination light for irradiating living tissue;

[0022] An electronic endoscope having an imaging element configured to capture living tissue as a moving image using a rolling shutter method;

[0023] A processor comprising: an image processing unit configured to perform image processing on a frame image obtained by imaging by the imaging element; and an adjustment unit configured to perform adjustment processing for adjusting the brightness of the frame image by combining at least one of adjustment of the exposure time of the imaging element, adjustment of the light intensity of the illumination light, and gain adjustment for determining the signal level of the imaging signal of the frame image obtained by the imaging element, and configured to perform adjustment determination and, based on a determination result of the adjustment determination, perform the adjustment processing by adjusting an adjustment level whose value represents the strength of the adjustment processing, wherein the adjustment determination includes determining whether at least one of first information related to an amount of movement between adjacent frame images in an image of a subject in the captured image and second information related to an amount of jitter at an edge of the image of the subject in the captured image satisfies an adjustment condition; and

[0024] The monitor is configured to display the frame image that has been image-processed.

[0025] Preferably, the first information related to the movement amount includes at least one of the movement amount of the subject image in the current frame image and the change amount between the movement amount of the subject image in the current frame image and the movement amount of the subject image in the previous frame image.

[0026] Preferably, the second information related to the jitter amount includes at least one of the jitter amount of the subject image in the current frame image, or the change amount between the jitter amount of the subject image in the current frame image and the jitter amount of the subject image in the previous frame image.

[0027] Preferably, the adjustment unit is used to adjust parameters so that the brightness level of the current frame image obtained by the imaging element reaches the target brightness level. When the brightness level of the current frame image is greater than the target brightness level, the currently set value is reduced; when the brightness level of the current frame image is less than the target brightness level, the currently set value is increased, and the brightness level of the image obtained by the imaging element is adjusted by using the set dimming amount.

[0028] Preferably, as the adjustment determination, the adjustment unit further determines whether third information related to the dimming amount satisfies an adjustment condition, and the determination result of the adjustment determination includes a determination result of the third information.

[0029] Preferably, the third information related to the dimming amount includes at least one of a change in the current dimming amount relative to the previous dimming amount and a maintenance time for which the dimming amount is maintained at a value lower than a predetermined value.

[0030] Preferably, the frame image includes: a display area for displaying the subject image; and a vignetting area formed outside the display area and having a lower brightness than the display area due to an imaging optical system of the electronic endoscope, and not displaying the subject image;

[0031] The adjustment unit further determines whether fourth information related to the pixel value in the vignetting area satisfies the adjustment condition;

[0032] The adjustment unit is configured to adjust the adjustment level based on a determination result of the fourth information.

[0033] Preferably, the fourth information related to the pixel values ​​of the vignetting area includes at least one of the cumulative value of the pixel values ​​in the vignetting area, the number of pixels in the vignetting area whose pixel values ​​exceed a predetermined threshold, the change in the cumulative value calculated from the previous frame image of the current frame image, and the change in the number of pixels calculated from the previous frame image of the current frame image.

[0034] Preferably, the adjustment unit performs the adjustment determination each time the frame image is obtained from the imaging element, and when a result of the adjustment determination is affirmative, the value of the adjustment level is greater than the value of the adjustment level determined in the previous frame image.

[0035] Preferably, at this time, the adjustment unit performs a plurality of determinations as the adjustment determinations, and when the determination results of at least one determination or at least two determinations among the plurality of determinations are affirmative, sets the determination result of the adjustment determination to affirmative.

[0036] Preferably, when the adjustment unit performs the adjustment judgment and the result of the judgment is negative, and the cumulative value of the pixel values ​​or the number of pixels in the vignetting area is greater than a predetermined threshold, the value of the adjustment level is maintained at the value of the adjustment level determined in the previous frame image.

[0037] Preferably, when the adjustment judgment performed by the adjustment unit results in a negative judgment result, and the cumulative value of the pixel values ​​or the number of pixels in the vignetting area is less than or equal to the threshold value, the value of the adjustment level in the current frame image is made smaller than the value of the adjustment level determined in the previous frame image.

[0038] Preferably, the adjustment unit includes an index calculation unit for calculating an index of the degree of generation of artifacts generated along a line corresponding to a scanning line of the imaging element by the rolling shutter method within the frame image.

[0039] When the adjustment determination performed by the adjustment unit results in a negative result and the index is greater than a predetermined threshold, the adjustment level is maintained at the adjustment level determined in the previous frame image.

[0040] Preferably, when the adjustment unit performs the adjustment judgment and the result is negative, and the index is less than or equal to a predetermined threshold, the value of the adjustment level in the current frame image is made smaller than the value of the adjustment level determined in the previous frame image.

[0041] Another aspect of the present invention is an endoscope system for displaying images of living tissue captured in a body cavity.

[0042] It has:

[0043] a light source device configured to generate illumination light for irradiating living tissue;

[0044] An electronic endoscope having an imaging element configured to capture living tissue as a moving image using a rolling shutter method;

[0045] A processor comprising: an image processing unit configured to perform image processing on a frame image obtained by imaging the imaging element; an index calculation unit configured to calculate an artifact generation index for indicating the degree of artifact generation along lines corresponding to scanning lines of the imaging element by the rolling shutter method within the frame image; and an adjustment unit configured to perform adjustment processing for adjusting the brightness of the frame image by combining at least one of adjustment of the exposure time of the imaging element, adjustment of the light intensity of the illumination light, and gain adjustment for determining the signal level of an imaging signal of the frame image obtained by the imaging element, and configured to perform the adjustment processing by adjusting an adjustment level whose value indicates the intensity of the adjustment processing, based on a result of determining whether the magnitude of the artifact generation index satisfies an adjustment condition; and

[0046] A monitor displays the frame image that has been image processed.

[0047] Preferably, the adjustment unit is used to adjust parameters so that the brightness level of the current frame image obtained by the imaging element reaches the target brightness level. When the brightness level of the current frame image is greater than the target brightness level, the currently set value is reduced; when the brightness level of the current frame image is less than the target brightness level, the currently set value is increased, and the brightness level of the image obtained by the imaging element is adjusted by using the set dimming amount.

[0048] Preferably, the adjustment unit includes a first reference table and a second reference table for determining the light intensity level relative to the light adjustment amount, the length of the exposure time, and the gain level of the gain adjustment.

[0049] The product of the light intensity level, the exposure time, and the gain level of the gain adjustment relative to the value of the dimming amount is consistent between the first reference table and the second reference table over the entire range of possible values ​​of the dimming amount; on the other hand, the correspondence between the light intensity level and the value of the dimming amount, and the correspondence between the exposure time and the value of the dimming amount are different between the first reference table and the second reference table.

[0050] The adjustment unit is configured to determine the adjustment values ​​of the light intensity level, the exposure time, and the gain level used in the adjustment process by interpolating between the first setting value and the second setting value corresponding to the first setting value according to the adjustment level using a first setting value and a second setting value, wherein the first setting value is the light intensity level, the exposure time, and the gain level determined by the first reference table based on the value of the dimming amount, and the second setting value is the light intensity level, the exposure time, and the gain level determined by the second reference table based on the value of the dimming amount.

[0051] Furthermore, preferably, in either the first reference table or the second reference table, the product of the light intensity level, the exposure time, and the gain level relative to the maximum value of the dimming amount is greater than the product of the light intensity level, the exposure time, and the gain level relative to the minimum value of the dimming amount.

[0052] In the entire range of possible values ​​of the dimming amount, the duration of the exposure time in the second reference table will not be less than the duration of the corresponding exposure time in the first reference table.

[0053] In the entire range of possible dimming values, the product of the light intensity level value and the gain level value in the second reference table will not be greater than the product of the corresponding light intensity level value and the gain level value in the first reference table.

[0054] Preferably, the first reference table and the second reference table have the dimming amount range, and the dimming amount range is that, relative to the value of the dimming amount, the exposure time of the second reference table is longer than the exposure time of the first reference table, and the light intensity level of the second reference table is smaller than the light intensity level of the first reference table.

[0055] Preferably, the stronger the degree of the adjustment process is, the larger the value of the adjustment level is; and the larger the value of the adjustment level is, the closer the adjustment value is to the second set value.

[0056] Effects of the Invention

[0057] According to the above-mentioned endoscope system, when capturing living tissue as a moving image using a rolling shutter method, the following processing can be performed: processing to suppress artifacts generated along lines corresponding to scanning lines of the camera element within the frame image; and adjustment processing capable of adjusting the brightness level without significantly changing the image brightness level. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a perspective view of the appearance of an endoscope system as one embodiment.

[0059] Figure 2 This is a block diagram showing the configuration of an endoscope system as one embodiment.

[0060] Figure 3 This is a diagram showing an example of the distal end surface of the distal end portion of an endoscope in one embodiment.

[0061] Figure 4 (a) Figure 4 (b) in FIG. 1 is a diagram illustrating artifacts generated in a frame image.

[0062] Figure 5 This is a block diagram showing an example of the configuration of an adjustment unit of an endoscope system as one embodiment.

[0063] Figure 6 This is a diagram illustrating an example of a method of calculating a value indicating a degree of movement in an endoscope system according to one embodiment.

[0064] Figure 7This is a diagram showing an example of temporal changes in values ​​indicating the calculated degree of movement in the endoscope system according to one embodiment.

[0065] Figure 8 This is a diagram illustrating an example of a method of calculating a value indicating a calculated degree of shake in an endoscope system according to one embodiment.

[0066] Figure 9 This is a diagram showing an example of how the value of the sum of pixels of a frame image changes over time when a differential filter for calculating a differential value in the horizontal direction is applied to a frame image.

[0067] Figure 10 This is a diagram illustrating a vignetting area used in an endoscope system as one embodiment.

[0068] Figure 11 This is a diagram showing an example of temporal changes in the integrated value of pixel values ​​in the vignetting area calculated in the endoscope system according to one embodiment.

[0069] Figure 12 This is a diagram showing an example of a flow of adjustment processing executed in an endoscope system as one embodiment.

[0070] Figure 13 It shows Figure 12 FIG. 1 is a diagram showing an example of a flow of setting the adjustment level in step S16 shown in FIG.

[0071] Figure 14 It shows Figure 12 FIG. 1 is a diagram showing an example of a flow of setting adjustment values ​​in step S18 shown in FIG.

[0072] Figure 15 (a) is a diagram showing an example of a common reference table used in an endoscope system according to one embodiment. Figure 15 (b) is a diagram showing an example of an RSA reduction reference table used in the endoscope system according to one embodiment.

[0073] Figure 16 This is a diagram illustrating an example of a method for calculating the RSA amount calculated in the endoscope system according to one embodiment.

[0074] Figure 17 This is a diagram showing an example of temporal changes in the RSA amount calculated in the endoscope system according to one embodiment.

[0075] Figure 18 This is a block diagram of the configuration of an adjustment unit in an endoscope system according to one embodiment.

[0076] Figure 19 (a) Figure 19(b) is a diagram showing an example of temporal changes in the RSA amount and the movement amount calculated in the endoscope system according to one embodiment.

[0077] Figure 20 (a) Figure 20 (b) is a diagram showing an example of temporal changes in the RSA amount and the movement amount calculated in the endoscope system according to one embodiment.

[0078] Figure 21 This is a diagram showing an example of temporal changes in the RSA amount and adjustment level calculated in the endoscope system according to one embodiment. DETAILED DESCRIPTION

[0079] Hereinafter, an endoscope system according to an embodiment will be described with reference to the drawings.

[0080] Figure 1 This is a perspective view of the appearance of an endoscope system 1 as one embodiment. Figure 2 This is a block diagram showing the configuration of an endoscope system as one embodiment. Figure 3 This is a diagram showing an example of the distal end surface of the distal end portion of an endoscope in one embodiment.

[0081] Figure 1 The illustrated endoscope system 1 is a system specifically for medical use and primarily includes an electronic endoscope (hereinafter referred to as an electronic scope) 100, a processor 200, a light source device 300, and a monitor 400. The electronic scope 100, the light source device 300, and the monitor 400 are each connected to the processor 200. Although the light source device 300 and the processor 200 are configured separately, the light source device 300 may also be integrally provided within the processor 200.

[0082] like Figure 2 As shown, the processor 200 includes a system controller 21. The system controller 21 is a control unit for executing various programs stored in a memory (not shown) and for centrally controlling the entire endoscope system 1. The system controller 21 is composed of software or hardware. Furthermore, the system controller 21 is connected to an operation panel 24. The system controller 21 changes various operations of the endoscope system 1 and parameters corresponding to each operation based on instructions input by an operator into the operation panel 24. Instructions input by the operator include, for example, instructions for switching the observation mode of the electronic endoscope system 1. Observation modes include a normal observation mode in which white light is used as illumination light and a special observation mode in which special light is used as illumination light.

[0083] Furthermore, the processor 200 includes an image processing unit 26 and an adjustment unit 28 .

[0084] The image processing unit 26 is configured to perform image processing on a frame image captured by the imaging element of the electronic scope 100 .

[0085] The adjustment unit 28 is configured to perform adjustment processing for adjusting the brightness of the frame image by combining at least one of adjustment of the exposure time of the imaging element, adjustment of the light intensity of the illumination light, and gain adjustment for determining the signal level of the imaging signal of the frame image obtained by the imaging element. A detailed description will be given later.

[0086] Although not shown in the figure, the processor 200 includes a timing controller that outputs clock pulses to each circuit in the endoscope system 1 for adjusting the operation timing of each component.

[0087] The light source device 300 includes a light source unit 310, a light intensity control circuit 340, and a focusing lens 350. The light intensity control circuit 340 generates a drive signal for changing the light intensity level of the light source in response to an instruction from the system controller 21, and outputs the signal to the light source unit 310. The light source unit 310 irradiates light at a set light intensity level as illumination light for irradiating living tissue. The light includes at least white light and may also include special light in a specific wavelength band. The light source unit 310 includes a xenon lamp for emitting white light, an LED or laser diode for emitting special light, or the like. Alternatively, special light may be generated by passing white light through an optical filter.

[0088] like Figure 2 As shown, the illumination light L emitted from the light source unit 310 is focused by the condenser lens 350 onto the incident end face of an LCB (Light Carrying Bundle) 11 , which is composed of a plurality of optical fiber bundles, and is incident on the LCB 11 .

[0089] like Figure 1 As shown, the electronic scope 100 mainly includes a connection portion 50, an operating portion 52, an insertion portion 54, and a cable 51 for connecting the connection portion 50 and the operating portion 52. The insertion portion 54 includes a flexible tube 58 for connecting the operating portion 52 to the distal end 56 of the insertion portion 54. The flexible tube 58 is provided with the LCB 11, an air and water supply pipe for conveying fluids such as water or air, a surgical instrument introduction tube, and a signal line. The surgical instrument introduction tube is a tube through which surgical instruments used to treat living tissue (e.g., cutting or removing) are inserted from the distal end 56 through the operating portion 52 to treat the living tissue. The signal line includes a transmission line for transmitting image signals captured by the imaging element 14 (described later) and a control line for transmitting control signals from the processor 200 to the imaging element 14.

[0090] The distal end of the electronic scope 100 is a flexible insertion portion 54 for insertion into the human body. A bending portion 60, connected to the proximal end of the insertion portion 54, is provided near the distal end of the insertion portion 54. The bending portion 60 bends in response to remote control of the operating portion 52. The bending mechanism of the bending portion 60 is a well-known mechanism incorporated into conventional endoscopes. The bending mechanism bends the bending portion 60 by pulling an operating wire linked to rotation of a bending operation knob provided on the operating portion 52. A distal end portion 56 equipped with an imaging element 14 is provided at the distal end of the bending portion 60.

[0091] The front end portion 56 of the electronic scope 100 includes an illumination light emitting end of the LCB 11 arranged over substantially the entire length from the connecting portion 50 to the front end portion 56 .

[0092] On the front end portion 56, as Figure 2 As shown in FIG, a light distribution lens is provided in front of the illumination light emitting end of LCB 11. In front of the light distribution lens on the living tissue side is an illumination window 12 for emitting illumination light. Furthermore, an objective lens for imaging the living tissue image is provided at the front end 56. In front of the objective lens on the living tissue side is an observation window 13 for receiving light from the living tissue image. Furthermore, an imaging element 14 for receiving the imaged image and an amplifier (not shown) for amplifying the image signal output from imaging element 14 are provided at the front end 56.

[0093] The illumination light incident on LCB 11 propagates within LCB 11, is emitted from the illumination light emitting end of LCB 11, and illuminates a living tissue subject as illumination light L via illumination window 12 formed by a light distribution lens. The light reflected from the subject in illumination light L emitted from illumination window 12 passes through observation window 13 formed by an objective lens, and forms an optical image on the light-receiving surface of imaging element 14.

[0094] Furthermore, the light source unit 310 of the light source device 300 may be built into the front end portion 56 of the electronic scope 100 for a compact structure. In this case, the LCB 11 and the condenser lens 350 for guiding the illumination light L from the light source unit 310 to the front end portion 56 are unnecessary.

[0095] Figure 3An example of the front end face 57 of the front end portion 56 is shown. Two illumination windows 12, each formed of a light-distributing lens disposed in front of the front end of the LCB 11, are provided on the front end face 57. Furthermore, an observation window 13, formed of an objective lens, is provided between the illumination windows 12. Furthermore, the front end face 57 includes a surgical instrument opening 62 for protruding surgical instruments from the front end face 57, and an air and water supply port 64 (fluid discharge port) for discharging fluid for cleaning the illumination windows 12 and the observation window 13. The air and water supply port 64 is, for example, a portion that receives a supply of fluid from a fluid delivery mechanism (not shown) connected to the operating portion 52 via an air and water supply pipe within the flexible tube 58 and discharges the fluid. Specifically, the air and water supply port 64 has three discharge nozzles configured to spray water or air onto each of the two illumination windows 12 and the one observation window 13 for cleaning.

[0096] In addition, instead of Figure 3 As shown in the front end surface 57, the air and water supply ports 64 may also be provided with an air supply port for jetting air and a water supply port for spraying water, respectively.

[0097] The imaging element 14 is a color imaging element having a predetermined pixel configuration, such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The imaging element 14 accumulates the optical image formed on each pixel of the light-receiving surface as an electric charge that varies with the amount of light, and generates and outputs R (Red), G (Green), and B (Blue) image signals. A color filter for determining the sensitivity band of the image color component of the image captured by the imaging element 14 is provided in front of each light-receiving position of the imaging element 14. The color filter can be, for example, a primary color filter of red (R), green (G), and blue (B). The imaging element 14 repeatedly captures living tissue at the time point according to the clock pulse sent from the processor 200.

[0098] Furthermore, the imaging element 14 captures images using a rolling shutter method. Specifically, rolling shutter capture involves setting one or more rows of pixels extending horizontally across the light-receiving surface of the imaging element 14 as a single pixel region. Exposure is performed by sequentially setting time differences within each pixel region. After resetting the accumulated charge for each region, the accumulated charge is accumulated and the accumulated image signal is output (read). Therefore, within a captured frame, the exposure time is staggered at predetermined intervals for each row or multiple rows.

[0099] like Figure 2As shown, a driver signal processing circuit 15 and a memory (not shown) are provided within the connection portion 50 of the electronic scope 100. Image signals of living tissue are input from the imaging element 14 to the driver signal processing circuit 15 at a frame rate. The frame rate is, for example, 1 / 30 second. The driver signal processing circuit 15 performs predetermined processing on the image signals transmitted from the imaging element 14 and then outputs the signals to the image processing unit 26 and adjustment unit 28 of the processor 200.

[0100] The driver signal processing circuit 15 also accesses a memory (not shown) to read information unique to the electronic scope 100. The unique information of the electronic scope 100 recorded in the memory includes, for example, the number of pixels, sensitivity, operable frame rate, and model of the imaging element 14. The driver signal processing circuit 15 outputs the unique information read from the memory to the system controller 21.

[0101] The system controller 21 performs various calculations and generates control signals based on information unique to the electronic scope 100. A timing controller (not shown) uses these generated control signals to control the operation and timing of various components of the endoscope system 1, thereby executing processing appropriate for the electronic scope 100 connected to the processor 200.

[0102] The driver signal processing circuit 15 receives a supply of clock pulses from a timing controller (not shown) in accordance with timing control executed by the system controller 21. Based on the supplied clock pulses, the driver signal processing circuit 15 drives and controls the imaging element 14 at a timing synchronized with the image frame rate processed by the processor 200. Thus, the imaging element 14 continuously captures the subject and continuously generates image signals representing frame images of the subject.

[0103] The image processing unit 26 performs predetermined image processing, such as demosaicing, matrix operations, and color balancing, on the image signal of the captured image input from the driver signal processing circuit 15 in a frame cycle, and then outputs the signal to a frame memory (not shown). The frame memory buffers the input image signal and outputs the image signal according to predetermined timing control. The image processing unit 26 further processes the output image signal to generate screen data for monitor display, converting the generated monitor display data into a predetermined video format signal. The converted video format signal is then output to the monitor 400. Thus, the moving image of the living tissue captured by the electronic scope 100 is displayed on the display screen of the monitor 400. In other words, the monitor 400 is configured to display the frame image after image processing.

[0104] The adjustment unit 28 is a component that performs adjustment processing for adjusting the brightness of the frame image by combining at least one of adjustment of the exposure time of the imaging element 14, adjustment of the light intensity of the illumination light, and gain adjustment for determining the signal level of the imaging signal of the frame image obtained by the imaging element 14, while performing adjustment processing for reducing RSA (described later). Specifically, the adjustment unit 28 is configured to perform adjustment processing by adjusting an adjustment level (a value indicating the intensity of the adjustment processing) based on the result of the adjustment determination. The adjustment determination includes determining whether at least one of information related to the amount of movement between adjacent frame images in the subject image within the captured image and information related to the amount of jitter at the edge of the subject image within the captured image satisfies adjustment conditions. The adjustment determination preferably also includes a determination regarding the amount of light adjustment (described later).

[0105] As described above, in such an endoscope system 1 , since the imaging element 14 performs imaging using a rolling shutter method, the exposure time in one frame of an image captured is shifted at predetermined time intervals for each line or for a plurality of lines.

[0106] As a result, high-speed droplets may sometimes be captured within an image, or liquid may contact (or adhere to) observation window 13, forming a stream. In such cases, edge distortion often occurs during rolling shutter imaging due to variations in exposure time. Hereinafter, due to the use of a rolling shutter method, artifacts are generated along lines corresponding to the scan lines of imaging element 14 in the frame image, and this edge distortion is referred to as RSA (rolling shutter artifact).

[0107] Figure 4 (a) Figure 4 (b) in FIG is a diagram illustrating RSA generated within a frame image. Figure 4 As shown in (a) of FIG. 1 , when the droplet Drp moves in the vertical direction of the captured image, in the rolling shutter method, as shown in FIG. 1 , the droplet Drp moves in the vertical direction of the captured image, as shown in FIG. Figure 4 As shown in (b) of the figure, because one or more image areas are sequentially exposed and captured with staggered exposure times, the image of the droplet Drp may be interrupted within the frame along the lines corresponding to the scanning lines of the imaging element 14. This is called RSA. As a result, the image becomes discontinuous between adjacent vertical lines, forming striped edges extending horizontally. This phenomenon is not limited to droplets Drp; when liquid forms a flow, the image of living tissue may also experience jitter due to the flow, resulting in RSA.

[0108] In addition, Figure 4In the example shown in (b), there is an example in which the image area of ​​one or more rows and the adjacent image areas do not overlap with each other in exposure time, but the exposure time may also partially overlap between adjacent image areas.

[0109] In the endoscope system 1, as a situation where such RSA may occur, the following situations can be cited for the observation window 13 with foreign matter attached to the surface: Figure 3 The liquid ejected from the air and water supply port 64 shown in FIG. 5 cleans the surface of the observation window 13, and the front end face 57 contacts the liquid in the living tissue, causing the liquid to contact the observation window 13 and flow. Therefore, in order to predict the above-mentioned situation in which RSA is likely to occur before it occurs, the adjustment unit 28 (refer to FIG. Figure 2 ) Using the image feature quantity calculated based on the continuously generated frame images or the dimming amount described later, the situation in which RSA may occur is determined, and based on the determination, the adjustment process described later for reducing the occurrence of RSA is performed. In the adjustment process, RSA can be reduced by extending the exposure time of the imaging element 14. However, since the brightness of the frame image also increases, the adjustment of the exposure time of the imaging element 14 is combined with the adjustment of the light intensity of the combined illumination light and the gain adjustment for determining the signal level of the imaging signal of the frame image obtained by the imaging element 14 to perform the adjustment process. At this time, the adjustment process is performed by adjusting the adjustment level, whose value represents the strength of the adjustment process, according to the frame image or the dimming amount.

[0110] Figure 5 This is a block diagram showing an example of the configuration of the adjustment unit 28 of the endoscope system 1 as one embodiment.

[0111] The adjustment unit 28 includes a frame memory 29 , a movement detection unit 28 a , a liquid contact detection unit 28 b , a vibration detection unit 28 c , a dimming control unit 28 d , and an adjustment value setting unit 28 e .

[0112] The motion detection unit 28a is a portion for detecting information related to the amount of movement of the subject image between adjacent frame images within the captured image. The information related to the amount of movement includes the amount of movement of the subject image in the current frame image, or the amount of change in the amount of movement of the subject image in the current frame image relative to the amount of movement of the subject image in the previous frame image. Below, as information related to the amount of movement, the amount of movement of the subject image in the current frame image is used as an example for explanation. Since the amount of movement is determined by comparison with adjacent frame images, the previous frame image used as the comparison object is temporarily maintained in the frame memory 29 relative to the current frame image, and when the current frame image is provided, the previous frame image is read from the frame memory 29. A specific description of the degree of movement to be detected will be described later.

[0113] According to one embodiment, the movement detection unit 28 a preferably further detects a change in the movement amount of the current frame image obtained by the imaging element 14 relative to the movement amount in the previous frame image as information related to the movement amount.

[0114] The shake detection unit 28c is responsible for detecting information related to the amount of shake at the edge of the subject image. This information includes at least one of the amount of shake at the edge of the subject image in the current frame image or the amount of change in the amount of shake at the edge of the subject image in the current frame image relative to the amount of shake at the edge of the subject image in the previous frame image. The specific amount of shake to be detected will be described later.

[0115] The frame image generated by the imaging element 14 includes a display area for displaying a subject image and a vignetting area formed outside the display area and having a lower brightness than the display area due to the imaging optical system of the electronic scope 1 and not displaying the subject image.

[0116] The liquid contact detection unit 28b calculates information related to the pixel values ​​of the vignetting area. The information related to the pixel values ​​of the vignetting area includes at least one of the cumulative value of the pixel values ​​in the vignetting area, the number of pixels in the vignetting area whose pixel values ​​exceed a predetermined threshold, the change in the cumulative value calculated from the frame image before the current frame image, and the change in the above number of pixels calculated from the frame image before the current frame image. When liquid contacts (or adheres to) the observation window 13, the viewing angle expands according to the refractive index of the liquid, and the pixel values ​​of the vignetting area become larger than the pixel values ​​of the vignetting area when the liquid is not in contact (or adhered). Therefore, by checking the pixel values ​​in the vignetting area, it is possible to determine whether the liquid is adhered to the observation window 13. A detailed description of the vignetting area will be described later.

[0117] The dimming control unit 28d adjusts parameters so that the brightness level of the current frame image captured by the imaging element 14 reaches the target brightness level. If the brightness level of the current frame image exceeds the target brightness level, the currently set value is reduced; if the brightness level of the current frame image is less than the target brightness level, the currently set value is increased, and the brightness level of the frame image captured by the imaging element 14 is adjusted according to the set dimming amount. Therefore, when capturing a frame image, the dimming control unit 28d converts pixel values ​​into brightness values, calculates the sum of the brightness values ​​of valid pixels (pixels outside the vignetting area), and calculates the average brightness level obtained by dividing by the number of valid pixels as the current brightness level. The dimming control unit 28d changes the currently set dimming amount based on the current brightness level and the target brightness level.

[0118] According to one embodiment, the value obtained by adding log2 (target brightness level / current brightness level) / constant (the constant is a pre-set value, for example, the value is set to 10) to the value of the currently set dimming amount is the value of the newly set dimming amount. In addition, the value of the dimming amount when the processor 200 is started is set to a predetermined value, for example, 50%. The value of the dimming amount is 100%, which means that the light intensity of the light source device 300, the exposure time of the imaging element 14, and the gain level of the imaging element 14 are maximum; the value of the dimming amount is 0%, which means that the light intensity of the light source device 300, the exposure time of the imaging element 14, and the gain level of the imaging element 14 are minimum. In the following examples of dimming amounts, the values ​​of the dimming amounts are expressed as 0 to 100%.

[0119] If observation window 13 is close to the subject and receives a large amount of reflected light from the subject, causing the brightness value of the frame image to increase, the dimming amount decreases. In this case, observation window 13 is in contact with the subject, and liquid in the subject is easily in contact with (adhering to) observation window 13. Therefore, the change in the current dimming amount relative to the previous dimming amount reflects the fact that observation window 13 is close to the subject and liquid in the subject is easily in contact with (adhering to) observation window 13.

[0120] Furthermore, when observation window 13 is in contact with the subject or is kept very close to the subject, liquid in the subject is likely to come into contact with (adhere to) observation window 13. Therefore, the duration for which the dimming amount is maintained below a predetermined value reflects the condition in which liquid in the subject is likely to come into contact with (adhere to) observation window 13.

[0121] Therefore, the dimming control unit 28 d preferably calculates at least one of a change in the current dimming amount relative to the previous dimming amount and a maintenance time during which the dimming amount remains less than a predetermined value as information related to the dimming amount.

[0122] The information on the amount of movement, the amount of shaking, and the pixel value of the vignetting area is collectively referred to as image feature quantity. The image feature quantity, the light adjustment amount, and the amount of change in the light adjustment amount are used to set the adjustment level in the light adjustment value setting unit 28e, and further set the adjustment value.

[0123] The adjustment value setting unit 28e uses the image feature values ​​sent from the motion detection unit 28a, the shake detection unit 28c, and the liquid contact detection unit 28b, as well as the dimming level and its change in dimming level sent from the dimming control unit 28d, to determine whether these values ​​satisfy the adjustment conditions. The adjustment level is a value that indicates the intensity of the adjustment process, with larger values ​​indicating a stronger adjustment process. Details of the determinations made by the adjustment value setting unit 28e and the adjustment of the adjustment level will be described later.

[0124] Figure 6 This figure illustrates an example method for calculating the amount of movement. The movement detection unit 28a converts the pixel values ​​of valid pixels (excluding the vignetted area) in the frame image into luminance values ​​and calculates the difference in luminance values ​​between corresponding pixels by subtracting the luminance value obtained by converting the pixel values ​​of valid pixels in the previous frame image read from the frame memory 29 from the luminance value of the current frame image. The movement detection unit 28a also calculates the amount of movement by multiplying the number of pixels F1 with differences exceeding a predetermined threshold value TH1 in the frequency distribution of these differences by a predetermined coefficient. In the initial stages of liquid contact (or adhesion) with the observation window 13 and beginning to flow, or during the flow of the liquid, the number of differences exceeding this threshold increases. Therefore, when the amount of movement exceeds the predetermined threshold, it can be said that RSA is more likely to occur. While the above example uses the value obtained by multiplying the number of pixels F1 with differences exceeding the predetermined threshold value TH1 by a predetermined coefficient as the amount of movement, the method of calculating the amount of movement using luminance value differences is not limited to this method.

[0125] Figure 7 This graph shows an example of the temporal variation in the amount of movement obtained using the above method. In the state of Photo Im1, the amount of movement is small and stable. In contrast, in the state of Photo Im2, when water is supplied to observation window 13 for cleaning, the amount of movement is large and fluctuating. Subsequently, in Photo Im3, when the water supply is stopped, the amount of movement is small and stable. Thus, the amount of movement reflects whether liquid is flowing through observation window 13.

[0126] Figure 8: is a diagram illustrating an example of a method for calculating the amount of jitter. The jitter detection unit 28c applies a differential filter, for example, a 5-pixel x 5-pixel differential filter, to each of the valid pixels in the frame image, and calculates a transverse differential value representing the strength of an edge extending in the longitudinal direction of the frame image. In pixels corresponding to edges where pixel values ​​change sharply, the value resulting from the filtering process becomes larger. In the frequency distribution of transverse differential values ​​in the frame image, the jitter detection unit 28c further calculates the amount of jitter by multiplying the number of pixels F2 having differential values ​​below a predetermined threshold value TH2 by a predetermined coefficient. Since the transverse differential value does not reflect the degree of edges extending in a transverse linear manner and the number of occurrences thereof, as does RSA, but reflects the degree of edges extending in a longitudinal direction and the number of occurrences thereof, the amount of jitter calculated based on the transverse differential value does not reflect the occurrence of RSA extending in a transverse linear manner. However, as in the case of liquid flowing through observation window 13, the flow of the liquid causes the image of the subject to vibrate or blur in the vertical and horizontal directions, thereby reducing the number of vertical and horizontal edges. Therefore, it can be said that the fewer the number of edges extending in the vertical direction, the greater the amount of subject image vibration caused by the liquid flow. Therefore, it can be said that the number of pixels F2 having differential values ​​below threshold TH2 among the horizontal differential values ​​not affected by RSA generation reflects the degree of vibration of the subject image caused by the flow of liquid adhering to observation window 13.

[0127] Figure 9 This graph illustrates an example of how the sum of the values ​​of each pixel in a frame image changes over time when a differential filter for calculating lateral differential values ​​is applied to the frame image. In the state of photograph Im1, the sum of the differential values ​​is very stable. However, in the state of photograph Im2, which shows water being supplied to the observation window 13 for cleaning, the sum of the differential values ​​decreases. Subsequently, in the state of photograph Im3, which shows the water supply being stopped, the sum of the differential values ​​is large and stable. Thus, it can be said that the smaller the sum of the lateral differential values ​​(the sum of the lateral edges), the greater the amount of jitter. Therefore, the jitter detection unit 28c calculates a value representing the degree of jitter by multiplying the number of pixels F2 with differential values ​​below a predetermined threshold value TH2 in the frequency distribution of lateral differential values ​​in the frame image by a predetermined coefficient. The method for calculating the amount of jitter is not limited to the method described above; as long as the jitter amount can be set to decrease with increasing differential values ​​based on information about the lateral differential values, the method is not particularly limited.

[0128] Figure 10 is a diagram illustrating the vignetting area. Figure 10As shown, the frame image Im generated by the imaging element 14 includes: a circular display area Im4 for displaying a subject image; and a vignetting area Df formed outside the display area. The vignetting area Df is formed within a predetermined range. Figure 10 In the example shown, it is formed at the four corners of the rectangular frame image Im. The vignetted area Df is the area formed by the imaging optical system (circular lens system) of the electronic scope 1. However, when liquid contacts (or adheres to) the observation window 13, since the liquid has a higher refractive index than air, light can also reach the vignetted area Df due to this refractive index. Therefore, by determining the pixel values ​​of this vignetted area Df, it is possible to determine whether liquid is adhered to the observation window 13.

[0129] Figure 11 : is a diagram showing an example of how the cumulative value of pixel values, which is an example of information related to the pixel values ​​in the vignetting area Df, changes over time. In the state of the photograph Im1, the cumulative value of the pixel values ​​in the vignetting area Df is small and stable. In contrast, in the state of the photograph Im2 when water is supplied to the observation window 13 in order to clean the observation window 13, the cumulative value of the pixel values ​​in the vignetting area Df increases. Thereafter, in the state of the photograph Im3 when the water supply is stopped, the cumulative value of the pixel values ​​in the vignetting area Df is small and stable. In this way, the above-mentioned cumulative value reflects whether or not liquid is in contact with (or adheres to) the observation window 13. In Figure 11 In the example shown, the integrated value of the pixel values ​​in the vignetting area Df is used as information on the pixel values ​​of the vignetting area Df. However, the number F1 of pixels whose pixel values ​​in the vignetting area Df exceed a predetermined threshold value may be used.

[0130] In addition, if Figure 11 As shown, since the cumulative value of the pixel values ​​in the vignetting area Df increases sharply due to the contact with the liquid, or the above-mentioned number of pixels increases sharply, the change between the cumulative value or the number of pixels F1 in the current frame image Im and the cumulative value or the number of pixels F1 in the previous frame image Im can also be used as information related to the image feature value.

[0131] Furthermore, since the liquid in contact with the observation window 13 begins to flow, and the greater the flow rate, the closer it is to a situation where RSA may occur, it is preferable to calculate a change in the movement amount as the above-mentioned image feature amount.

[0132] Furthermore, by bringing the front end face 57 of the electronic scope 100 closer to the living tissue surface, the liquid in the living tissue comes into contact with (or adheres to) the observation window 13. As the front end face 57 of the electronic scope 100 approaches the living tissue surface, the brightness of the image captured by the electronic scope 100 gradually increases. Therefore, through the dimming control unit 28d adjusting the dimming amount, the dimming amount gradually decreases. Therefore, if the difference between the dimming amount set for the current frame image and the dimming amount set for the previous frame image is negative, and the absolute value of this difference is greater than a predetermined threshold, it can be said that the observation window 13 is approaching a situation where contact with the liquid in the living tissue is likely to cause RSA. Therefore, the dimming control unit 28d preferably calculates the difference between the dimming amount set for the current frame image and the dimming amount set for the previous frame image.

[0133] The information on the image feature amount and the amount of change in the light adjustment amount are sent to the adjustment value setting unit 28e.

[0134] Figure 12 A diagram illustrates an example of the flow of adjustment processing performed in the endoscope system 1 according to one embodiment. First, when the endoscope system 1 is activated, the adjustment unit 28 resets the adjustment level, which indicates the image feature quantity and the intensity of the adjustment processing, to zero and sets the dimming level to 50% (step S10). The imaging element 14 then captures the subject, and the adjustment unit 28 obtains image data for the frame image (step S12). Once the adjustment unit 28 obtains the image data, the motion detection unit 28a, shake detection unit 28c, liquid contact detection unit 28b, and dimming control unit 28d of the adjustment unit 28 calculate the image feature quantity and the dimming level as described above (step S14).

[0135] Next, the adjustment value setting unit 28e sets an adjustment level indicating the strength of the adjustment process for reducing RSA and adjusting the brightness of the image (step S14). The adjustment level is set according to the value of the image feature value and the change in the dimming amount. The setting of the adjustment level will be described later.

[0136] Furthermore, the adjustment value setting unit 28e sets an adjustment value for determining the light intensity level of the illumination light irradiated by the light source unit 310, the length of the exposure time performed by the imaging element 14, and the gain level of the signal level of the imaging signal generated by the imaging element 14 according to the set adjustment level and dimming amount (step S18).

[0137] The set light intensity level, exposure time, and gain level are transmitted to the system controller 21, which generates a control signal related to the light intensity level, exposure time, and gain level. This control signal is sent to the light intensity control circuit 340 and the imaging element 14, indicating the light intensity level, exposure time, and gain level to the light intensity control circuit 340 and the imaging element 14. The gain of an amplifier (not shown) built into the imaging element 14 is adjusted based on the gain level.

[0138] The adjustment unit 28 determines whether the input of image data has ended (step S22). If so, the adjustment value setting is completed. On the other hand, if the adjustment unit 28 determines that the input of image data has not ended, that is, if the next frame of image data is to be acquired, the image feature values ​​and various internal parameters are reset to zero (step S24) and new image data is acquired (step S12). In this manner, the adjustment level and adjustment value are set each time image data is input.

[0139] Figure 13 It shows Figure 12 FIG. 1 is a diagram showing an example of a flow of setting the adjustment level in step S16 shown in FIG.

[0140] The adjustment value setting unit 28e determines whether information related to image feature quantities such as the amount of movement, the change in the amount of movement (the difference between the amount of movement in the current frame image and the amount of movement in the previous frame image), and the amount of jitter, as well as the change in the dimming amount (the difference between the dimming amount set in the current frame image and the dimming amount set in the previous frame image) meet pre-set adjustment conditions (making an adjustment determination) (step S30). The adjustment conditions are set separately according to the amount of movement, the change in the amount of movement, the amount of jitter, and the change in the dimming amount. For example, the adjustment value setting unit 28e determines whether the amount of movement is greater than a pre-set first threshold, whether the amount of jitter is greater than a pre-set second threshold, whether the change in the amount of movement is greater than a pre-set third threshold, whether the change in the dimming amount is negative, or whether the absolute value of the change in the dimming amount is greater than a pre-set fifth threshold.

[0141] In addition to such determination, the amount of change in the jitter amount and the time for which the dimming amount is maintained below a predetermined value may be used to determine the adjustment condition.

[0142] If any of these multiple determinations are positive, the adjustment value setting unit 28e sets the value obtained by adding 10% to the currently set adjustment level as the new adjustment level (step S32). Furthermore, in the above adjustment determination, step S32 is executed when at least one of the multiple determination targets is positive, and step S32 can also be executed when at least two of the multiple determination targets meet the adjustment conditions.

[0143] The adjustment level is expressed in %, indicating the degree of intensity of the adjustment process. The adjustment level sets the intensity of the adjustment process, with 0% indicating no adjustment process at all and 100% indicating maximum adjustment process execution. When the endoscope system 1 is activated, the adjustment level is set to zero.

[0144] On the other hand, when any one of the judgments in step S30 is negative (the result of the adjustment judgment is negative), the adjustment value setting unit 28e determines whether the cumulative value of the pixel values ​​in the vignetting area Df is greater than the predetermined fourth threshold value (step S34). When the cumulative value of the pixel values ​​in the vignetting area Df is greater than the predetermined sixth threshold value, the possibility of RSA occurring is very high, so the adjustment level of the adjustment process for reducing RSA is maintained (step S36). When it is determined that the cumulative value of the pixel values ​​in the vignetting area Df is less than or equal to the predetermined fourth threshold value, the adjustment value setting unit 28e considers that although RSA has occurred, the number of occurrences has decreased, or that RSA has not occurred, and sets the value obtained by subtracting 10% of the adjustment level as a new adjustment level (step S38).

[0145] In this way, the adjustment value setting unit 28e sets the adjustment level based on the changes in the image adjustment amount and the light adjustment amount. In the determination of step S34, the cumulative value of the pixel values ​​in the vignetting area Df is used. However, the number of pixels F1 in the vignetting area Df whose pixel values ​​exceed the threshold value may be used instead of the cumulative value.

[0146] Figure 14 It shows Figure 12 FIG. 1 is a diagram showing an example of a flow of setting adjustment values ​​in step S18 shown in FIG.

[0147] The adjustment value setting unit 28e uses the first setting value of each of the light intensity level, exposure time, and gain level when the adjustment processing is performed under the premise that the adjustment level is 0%, that is, when no adjustment processing is performed at all, and the second setting value of each of the light intensity level, exposure time, and gain level when the adjustment processing is performed under the premise that the adjustment level is 100%, and interpolates between the first setting value and the second setting value according to the adjustment level to thereby determine the adjustment value of the light intensity level, the duration of the exposure time, and the gain level.

[0148] Specifically, the adjustment value setting unit 28e refers to a non-adjustment processing reference table (first reference table, hereinafter referred to as a normal reference table) and an RSA reduction processing reference table (second reference table) when no adjustment processing as RSA reduction processing is performed. Based on the dimming amount sent from the dimming control unit 28d, the adjustment value setting unit 28e retrieves the light intensity level I1, exposure time T1, and gain G1 as the first setting value from the normal reference table, and retrieves the light intensity level I2, exposure time T2, and gain G2 as the second setting value from the RSA reduction processing reference table (step S50). The normal reference table and the RSA reduction reference table are tables that define the correspondence between the light intensity level, exposure time, and gain with respect to the dimming amount. These correspondences represent changes in the light intensity level, exposure time, and gain with respect to the dimming amount. Figure 15 (a) is a diagram showing an example of a commonly used reference table. Figure 15 (b) is a diagram showing an example of a reference table for RSA reduction. Figure 15 (a) Figure 15 In (b), the image is normalized based on the preset light intensity level, exposure time, and gain level, and expressed in %.

[0149] from Figure 15 (a) Figure 15 As can be seen from (b) in the figure, the changes in exposure time and light intensity level with respect to the dimming amount are different between the commonly used reference table and the reference table for RSA reduction processing. In the reference table for RSA reduction processing, in the part where the dimming amount is small, in order to reduce the generation of RSA, the exposure time is made longer than the corresponding exposure time in the commonly used reference table. However, since the brightness of the image is increased by extending the exposure time, the light intensity level is lowered in order to suppress the increase in brightness. In addition, in the example shown in the figure, the gain level is roughly the same between the commonly used reference table and the reference table for RSA reduction, but the exposure time, light intensity level and gain level can also be made different between the commonly used reference table and the reference table for RSA reduction. In this case, it is preferable to set the products of the exposure time, light intensity level and gain level between the commonly used reference table and the reference table for RSA reduction in such a way that the product of the exposure time, light intensity level and gain level is the same, from the point of view that the brightness level in the image will not change even if the adjustment process is performed.

[0150] The adjustment value setting unit 28e sets the values ​​of light intensity level I, exposure time T and gain G by interpolating according to the adjustment level between the extracted light intensity level I1, exposure time T1 and gain G1, and the light intensity level I2, exposure time T2 and gain G2 (step S52).

[0151] When the right Figure 14 When the formula shown in step S52 is transformed, for example, the light intensity level I becomes I=I1 (1-α) I2 α (α is the value obtained by dividing the adjustment level by 100.) That is, when adjustment level α = 0 (no adjustment processing), I = I1; when adjustment level α = 1 (maximum intensity adjustment processing), I = I2. When adjustment level α is greater than 0 and less than 1, the exponents of I1 and I2 are assigned according to adjustment level α, and the interpolated value is set.

[0152] Therefore, according to one embodiment, preferably, the stronger the adjustment process, the higher the value of the adjustment level α, and the higher the value of the adjustment level α, the closer the adjustment value is to the light intensity level I2, exposure time T2 and gain G2 (second set value).

[0153] Information on the light intensity level I, exposure time T, and gain G value set in this manner is sent as a control signal to the light amount control circuit 340 and the imaging element 14 .

[0154] In the endoscope system 1, the adjustment unit 28 of the processor 200 is configured to perform an adjustment process for adjusting the brightness of the frame image by combining at least one of adjustment of the exposure time of the imaging element 14, adjustment of the light intensity of the illumination light, and gain adjustment, perform an adjustment determination, and, based on the result of the adjustment determination, adjust an adjustment level, which represents the strength of the adjustment process for reducing RSA. The adjustment determination includes determining whether at least one of information related to the amount of motion between adjacent frame images in the subject image within the captured image and information related to the amount of jitter at the edge of the subject image satisfies an adjustment condition. Therefore, the adjustment process for reducing RSA can be performed before RSA occurs. Furthermore, since the adjustment level is adjusted based on at least information related to the amount of motion of the subject image or information related to the amount of jitter within the image, the strength of the adjustment process can be determined by the adjustment level, effectively performing the adjustment process to suppress the occurrence of RSA. The amount of movement or shaking of the subject image tends to increase before the liquid contacts the observation window 13 or when the liquid contacts the observation window 13 , and can be effectively used as an indicator for predicting the occurrence of RSA.

[0155] Furthermore, the adjustment unit 28 determines information related to the amount of jitter and the amount of movement of the subject image edge, and adjusts the adjustment level based on these determination results. This allows for more accurate determination of possible RSA situations. For example, an adjustment condition related to the amount of movement may include whether the amount of movement exceeds a first threshold. An adjustment condition related to the amount of jitter at the edge may include whether the amount of jitter exceeds a second threshold.

[0156] In addition, the information related to the amount of movement preferably includes at least one of the amount of movement of the subject image in the current frame image and the amount of change between the amount of movement of the subject image in the current frame image and the amount of movement of the subject image in the previous frame image. In addition, the information related to the amount of jitter preferably includes at least one of the amount of jitter of the subject image in the current frame image and the amount of change between the amount of jitter of the subject image in the current frame image and the amount of jitter of the subject image in the previous frame image. This allows the adjustment unit 28 to comprehensively determine situations in which RSA may occur. The adjustment condition related to the amount of change in movement or the amount of change in jitter is, for example, whether the amount of change in movement or the amount of change in jitter exceeds a threshold.

[0157] Furthermore, as described above, the adjustment unit 28 is preferably configured to adjust the adjustment level based on at least the determination result regarding the information related to the dimming amount. Since the adjustment unit 28 uses the dimming amount to adjust the brightness level of the image captured by the imaging element 14, it can effectively bring the brightness level to the target brightness level. When the front end 72 approaches the subject, the adjustment unit 28 reduces the dimming amount so that the brightness level of the frame image does not rise to a level that causes the observation window 13 to come into contact with (or adhere to) the liquid in the living tissue. Therefore, it is preferable to adjust the adjustment level assuming this situation. Specifically, the adjustment unit 28 is configured to determine whether the change between the current dimming amount (the dimming amount set for the current frame image) and the previous dimming amount (the dimming amount set for the previous frame image) satisfies an adjustment condition, and to adjust the adjustment level based on the determination result regarding the information related to the amount of motion or shake and the determination result regarding the change in the dimming amount. The adjustment condition regarding the change in the dimming amount includes, for example, whether the change in the dimming amount is negative and whether the absolute value of the change in the dimming amount is greater than a fifth threshold value.

[0158] In addition, while maintaining the observation window 13 in contact with the subject or extremely close to the subject, as described above, considering that the liquid in the subject easily contacts (adheres) to the observation window 13, it is preferred to calculate at least one of the maintenance times for maintaining the dimming amount to a value less than a predetermined value.

[0159] This allows the adjustment unit 28 to more accurately determine situations where RSA may occur.

[0160] In addition to determining whether the information related to the pixel values ​​in the vignetting area Df satisfies the adjustment conditions and determining information related to the amount of motion or shake, the adjustment unit 28 is configured to adjust the adjustment level based on at least the information related to the pixel values ​​in the vignetting area Df, in addition to the determination results related to the amount of motion or shake. This allows the adjustment unit 28 to more accurately determine the likelihood of RSA. As described above, the information related to the pixel values ​​in the vignetting area Df preferably includes at least one of the cumulative value of the pixel values ​​in the vignetting area Df, the number F1 of pixels in the vignetting area Df whose pixel values ​​exceed a predetermined threshold, the change in the cumulative value from the frame image immediately preceding the current frame image, and the change in the number of pixels F1 from the frame image immediately preceding the current frame image. The adjustment condition related to the cumulative value of the pixel values ​​in the vignetting area Df is, for example, whether the cumulative value is greater than a fourth threshold.

[0161] As mentioned above, Figure 13 As shown in step S30, each time a frame image is obtained from the imaging element 14, the adjustment unit 28 performs adjustment determination using the adjustment conditions. If the adjustment determination is positive, for example, if at least one of the plurality of pieces of information to be determined is positive, the adjustment unit 28 performs adjustment determination using the adjustment conditions. Figure 13 As shown in step S32 , the value of the adjustment level is greater than the value of the adjustment level determined in the previous frame image, and therefore the adjustment level can be adjusted sequentially according to the frame image.

[0162] When the adjustment unit 28 performs an adjustment judgment in step S30 and the result is negative, and the cumulative value of the pixel values ​​in the vignetting area Df is greater than the predetermined fourth threshold value, the adjustment value setting unit 28e maintains the value of the adjustment level at the value of the adjustment level determined in the previous frame image, thereby being able to appropriately maintain the adjustment level according to the frame image.

[0163] In addition, when the adjustment unit 28 performs an adjustment judgment in step S30 and the result is negative, and the cumulative value of the pixel values ​​in the vignetting area Df is less than or equal to the fourth threshold value, the value of the adjustment level in the current frame image is made smaller than the value of the adjustment level determined in the previous frame image, so that the adjustment level can be adjusted sequentially according to the frame image.

[0164] In addition, Figure 13 In the process shown, in step S34, the judgment is made by calculating the cumulative value of the pixel values ​​in the vignetting area Df and comparing it with the 4th threshold value, but instead of the cumulative value, the amount of RSA generated in the frame image (hereinafter referred to as the RSA amount) can be compared with the pre-set 7th threshold value. When the RSA amount is greater than the 7th threshold value, step S36 is performed; when the RSA amount is less than or equal to the 7th threshold value, step S38 is performed. Figure 16 This is a diagram illustrating an example of a method for calculating the RSA amount.

[0165] exist Figure 16 In the example shown, the RSA amount is determined by multiplying the total number of pixels above threshold TH3 by a predetermined coefficient in the frequency distribution of the value obtained by subtracting the horizontal differential value from the vertical differential value for each pixel in the frame image. The vertical differential value reflects not only the edges of the RSA but also the vertical jitter of the subject image. The horizontal differential value does not reflect the edges of the RSA but rather the horizontal jitter of the frame image. Here, assuming that the degree of vertical jitter is the same as that of horizontal jitter, the value obtained by subtracting the horizontal differential value from the vertical differential value is used to eliminate the vertical jitter.

[0166] Instead of using RSA Figure 13 The cumulative value of the pixel values ​​in the vignetting area Df in step S34 is shown.

[0167] Figure 17 This graph shows an example of how the RSA level, obtained using the above method, changes over time. In the state of Photo Im1, the RSA level is small and stable. In contrast, in the state of Photo Im2, when water is supplied to the observation window 13 for cleaning, the RSA level increases and fluctuates. Subsequently, in the state of Photo Im3, when the water supply is stopped, the RSA level is small and stable. Thus, the RSA level reflects the number of RSA events generated.

[0168] Therefore, according to one embodiment, the adjustment unit 28 includes an RSA detection unit (index calculation unit) for calculating an index representing the degree of RSA generation, that is, an RSA amount, within the frame image. Figure 13 If the result of the determination in step S30 is negative and the RSA amount is greater than the predetermined seventh threshold, Figure 13 As shown in step S36, it is preferable to maintain the value of the adjustment level at the value of the adjustment level determined in the previous frame image. In this way, the adjustment level can be maintained according to the frame image.

[0169] In addition, when the adjustment unit 28 is Figure 13 If the determination result in step S30 is negative and the RSA amount is less than or equal to the predetermined seventh threshold, Figure 13 As shown in step S38, it is preferable to make the adjustment level value in the current frame image smaller than the adjustment level value determined in the previous frame image. In this way, the adjustment level can be adjusted sequentially according to the frame image.

[0170] As described above, when the RSA amount is detected, the adjustment section 28 can adjust the adjustment level by using the following configuration of the adjustment section 28 and perform adjustment processing for reducing the RSA.

[0171] Figure 18 is with Figure 5 The shown diagram is a block diagram of the structure of the adjustment unit 28 according to a different embodiment of the adjustment unit 28 . Figure 18 The adjustment unit 28 shown in FIG has an RSA detection unit 28f instead of Figure 5 The liquid contact detection portion 28b shown in FIG, and the rest of the parts are the same as Figure 5 The adjustment section 28 shown in FIG is the same. Therefore, in Figure 18 In the figure, description of the dimming control unit 28d, the shake detection unit 28c, the frame memory 29, and the movement detection unit 28a is omitted.

[0172] The RSA detection unit 28f is a part (index calculation unit) that calculates the RSA amount, which is an index indicating the degree of RSA generation, within the frame image. Figure 16 The RSA amount is calculated using the method shown. The calculated RSA amount is sent to the adjustment value setting unit 28e. The adjustment value setting unit 28 is a part that performs adjustment processing, which is used to adjust the brightness of the frame image by combining the adjustment of the exposure time of the imaging element 14, the adjustment of the light intensity of the illumination light, and the gain adjustment for determining the signal level of the imaging signal of the frame image obtained by the imaging element 14. Specifically, the adjustment value setting unit 28e is configured to perform the adjustment processing by adjusting the adjustment level, which represents the strength of the adjustment processing by the size of the value, based on the result of the determination of whether the RSA amount meets the adjustment condition. In this case, whether the image feature amount sent from the motion detection unit 28a meets the adjustment condition and whether the change in the dimming amount sent from the dimming control unit 28d meets the adjustment condition can be determined together with the determination of whether the RSA amount meets the adjustment condition. The adjustment condition related to the RSA amount is whether the RSA amount is greater than the eighth threshold value.

[0173] In this case, if Figure 13 As shown in step S30, when all the determinations of whether the image feature quantity satisfies the adjustment condition, whether the change amount of the dimming amount sent from the dimming control unit 28d satisfies the adjustment condition, and whether the RSA quantity satisfies the adjustment condition are negative, the determination of whether the RSA quantity is greater than the seventh threshold value may be performed instead of the determination of whether the cumulative value of the pixel values ​​in the vignetting area is greater than the fourth threshold value. Figure 13 The determination in step S34 is shown.

[0174] Figure 19 (a) Figure 19 (b) is a diagram showing an example of temporal changes in values ​​representing the RSA amount and the movement amount. Figure 19 (a) Figure 19(b) in the figure shows the temporal changes in the RSA amount and the movement amount of the subject image when washing water is supplied to the observation window 13. After the washing water starts to be supplied, in the initial stage Tst until the water contacts the observation window 13 to form a water flow, the RSA amount does not increase, but reflects the movement of the subject image caused by the contact of water, and the movement amount increases. On the other hand, after the initial stage Tst, the RSA amount increases, but since the movement of the subject image is stable, the movement amount decreases. In this way, when RSA continues to occur, the value of the RSA amount increases. Therefore, before RSA occurs, it is possible to determine whether RSA is in a situation where it may occur based on the movement amount. When RSA occurs and continues to occur, the RSA amount can be used as an indicator of whether the adjustment level of the adjustment process should be maintained or the adjustment level should be reduced.

[0175] Figure 20 (a) Figure 20 (b) is also a diagram showing an example of changes in the RSA amount and the movement amount over time. Figure 20 (a) Figure 20 (b) in the figure shows the temporal changes in the RSA amount and the amount of movement of the subject image when the observation window 13 is brought close to living tissue, acting as the subject, and comes into contact with the liquid present in the tissue. In this case, the RSA amount does not increase during the initial period Tst, but the amount of movement reflects the movement of the subject image caused by the adhesion of the liquid, and the amount of movement increases. On the other hand, after the initial period Tst, the RSA amount increases, but the amount of movement decreases relatively because the movement of the subject image stabilizes.

[0176] Figure 21 Is to show the use of Figure 18 1 shows an example of how the RSA amount and adjustment level change over time when the adjustment process in one embodiment is performed by the adjustment unit 28 shown in FIG. In the state of Photo Im1, no RSA is generated, and the RSA amount is small and stable. From this state, when water is supplied to the observation window 13 for cleaning, RSA is generated and the RSA amount begins to increase. However, since the adjustment process is performed at an adjustment level that gradually increases, as shown in Photo Im2 * As shown in FIG. 1 , the occurrence of RSA in the subject image can be suppressed. Afterwards, in the state of the photo Im3 when the water supply is stopped, RSA is no longer generated and the amount of RSA becomes smaller. At the same time, the adjustment level is gradually reduced. In this way, in the photo Im2 * The adjustment level is set in the image, and the adjustment process is performed by combining at least one of the exposure time, light intensity level, and gain level. * The brightness level in is maintained at approximately the same level as that in photos Im1 and Im3.

[0177] In this manner, the adjustment level is adjusted and the adjustment process is performed based on the result of determination of whether the RSA amount satisfies the adjustment condition. Therefore, the adjustment level can be adjusted in various ways according to the occurrence of RSA.

[0178] like Figure 15 (a) Figure 15 As shown in the example in (b), the adjustment value setting unit 28e has a common reference table (first reference table) and a reference table for RSA reduction (second reference table) for determining the light intensity level relative to the dimming amount, the exposure time, and the gain level of the gain adjustment.

[0179] Here, according to one embodiment, the product of the light intensity level, exposure time, and gain level of gain adjustment relative to the value of the dimming amount is consistent across the entire range of possible dimming amount values ​​between the common reference table and the RSA reduction reference table. On the other hand, the correspondence between the light intensity level and the value of the dimming amount, and the correspondence between the exposure time and the value of the dimming amount, differ between the common reference table and the RSA reduction reference table. In other words, the change in the light intensity level and exposure time relative to changes in the dimming amount differs between the common reference table and the RSA reduction reference table, and the light intensity level and exposure time also differ.

[0180] According to one embodiment, the adjustment value setting unit 28e takes out a first setting value and a second setting value. The first setting value is obtained by using a common reference table ( Figure 15 The light intensity level, exposure time and gain level are determined by the reference table (shown in (a) in FIG. 1 ), and the second setting value is obtained by RSA reduction using the reference table ( Figure 15 The light intensity level, exposure time, and gain level are determined using the reference table (shown in (b) of FIG. ). Using these first and second set values, interpolation is performed between the first set value and the corresponding second set value according to the adjustment level to determine the adjustment values ​​for the light intensity level, exposure time, and gain level used in the adjustment process. Therefore, the adjustment value can be set according to the adjustment level. When the adjustment level is 0%, the first set value set by the common reference table becomes the adjustment value.

[0181] In this way, interpolation is performed between the first and second set values ​​according to the adjustment level, enabling adjustment processing to be performed with appropriate intensity. Furthermore, since the product of the light intensity level, exposure time, and gain adjustment level is consistent across the entire range of light adjustment values ​​between the normal reference table and the RSA reduction reference table, image brightness levels do not change even when adjustment processing is performed.

[0182] According to one embodiment, in the common reference table and the RSA reduction reference table, the product of the light intensity level, exposure time, and gain level relative to the maximum dimming amount is preferably greater than the product of the light intensity level, exposure time, and gain level relative to the minimum dimming amount. When the dimming amount is at its maximum, the image brightness level is extremely low. Therefore, in order to quickly adjust the image brightness level, the product of the light intensity level, exposure time, and gain level is preferably large. When the dimming amount is at its minimum, the image brightness level is extremely high. Therefore, the product of the light intensity level, exposure time, and gain level is preferably small. In this case, the exposure time in the RSA reduction reference table will not be less than the corresponding exposure time in the common reference table across the entire range of possible dimming amount values. At this time, within the entire range of possible dimming values, the product of the light intensity level value and the gain level value in the RSA reduction reference table will not be greater than the product of the corresponding light intensity level value and the gain level value in the commonly used reference table. This is preferable from the perspective that the brightness level of the frame image will not change with the presence or absence of adjustment processing and the change of the adjustment level in the adjustment processing.

[0183] In the adjustment process for reducing RSA, as the adjustment level becomes larger, the exposure time is extended and RSA is suppressed in most cases. Therefore, in order to prevent the brightness level from becoming larger due to the adjustment process of extending the exposure time, preferably, within the entire range of possible values ​​of the dimming amount, the product of the light intensity level value and the gain level value in the reference table for RSA reduction is smaller than the product of the corresponding light intensity level value and the gain level value in the commonly used reference table.

[0184] According to one embodiment, the commonly used reference table and the reference table for RSA reduction have a dimming amount range, that is, relative to the value of the dimming amount, the exposure time of the reference table for RSA reduction is longer than the exposure time of the commonly used reference table, and the light intensity level of the reference table for RSA reduction is smaller than the light intensity level of the commonly used reference table, but this is preferred from the perspective that the brightness level of the frame image will not change due to changes in the adjustment level during the adjustment process.

[0185] The endoscope system provided by the present invention has been described in detail above. However, the present invention is not limited to the above-mentioned embodiments, and various improvements and changes can be made without departing from the scope of the present invention.

[0186] Description of Reference Numerals

[0187] 1 Endoscope system

[0188] 11 LCB

[0189] 12 Lighting Window

[0190] 13 Observation window

[0191] 14 Camera Components

[0192] 15 Driver signal processing circuit

[0193] 21 System Controller

[0194] 24 Operation Panel

[0195] 26 Image Processing Department

[0196] 28 Adjustment Department

[0197] 28a Motion detection unit

[0198] 28b Liquid contact detection unit

[0199] 28c Jitter detection unit

[0200] 28d dimming control unit

[0201] 28e Adjustment value setting section

[0202] 28f RSA Detection Department

[0203] 29 frame memory

[0204] 50 Operation Department

[0205] 51 cables

[0206] 52 Operation Department

[0207] 54 Insertion

[0208] 56 front end

[0209] 57 front face

[0210] 58 flexible pipe

[0211] 60 Bend

[0212] 62 Openings for surgical instruments

[0213] 64 Gas and water supply ports

[0214] 200 processors

[0215] 300 Light Source Device

[0216] 310 Light Source Department

[0217] 340 light control circuit

[0218] 350 condenser lens

[0219] 400 monitors.

Claims

1. An endoscope system for displaying images of living tissue in a body cavity. It is characterized by: have: a light source device configured to generate illumination light for irradiating living tissue; An electronic endoscope having an imaging element configured to capture living tissue as a moving image using a rolling shutter method; A processor comprising: an image processing unit configured to perform image processing on a frame image obtained by imaging of the imaging element; and an adjustment unit configured to perform adjustment processing for adjusting the brightness of the frame image by combining at least one of adjustment for reducing the light intensity of the illumination light and gain adjustment for determining the signal level of the imaging signal of the frame image obtained by the imaging element and adjustment for extending the exposure time of the imaging element, and configured to perform adjustment determination and, based on a determination result of the adjustment determination, perform the adjustment processing by adjusting an adjustment level whose value indicates the strength of the adjustment processing, wherein the adjustment determination includes determining whether at least one of first information related to an amount of movement between adjacent frame images in an image of a subject in the captured image and second information related to an amount of jitter at an edge of the image of the subject in the captured image satisfies an adjustment condition; and The monitor is configured to display the frame image that has been image-processed.

2. The endoscope system according to claim 1, wherein: The first information related to the movement amount includes at least one of the movement amount of the subject image in a current frame image and a change amount between the movement amount of the subject image in the current frame image and the movement amount of the subject image in a previous frame image.

3. The endoscope system according to claim 1 or 2, wherein: The second information related to the shake amount includes at least one of the shake amount of the subject image in a current frame image or a change amount between the shake amount of the subject image in a current frame image and the shake amount of the subject image in a previous frame image.

4. The endoscope system according to claim 1 or 2, wherein: The adjustment unit is used to adjust parameters so that the brightness level of the current frame image obtained by the camera element reaches the target brightness level. When the brightness level of the current frame image is greater than the target brightness level, the currently set value is reduced; when the brightness level of the current frame image is less than the target brightness level, the currently set value is increased, and the brightness level of the frame image obtained by the camera element is adjusted by using the set dimming amount.

5. The endoscope system according to claim 4, wherein: The adjustment unit further determines, as the adjustment determination, whether third information related to the dimming amount satisfies an adjustment condition, and the determination result of the adjustment determination includes a determination result of the third information.

6. The endoscope system according to claim 5, wherein: The third information related to the dimming amount includes at least one of a change in the current dimming amount relative to the previous dimming amount and a maintenance time for which the dimming amount is maintained at a value lower than a predetermined value.

7. The endoscope system according to claim 1 or 2, wherein: The frame image includes: a display area for displaying the subject image; and a vignetting area formed outside the display area and having a lower brightness than the display area due to an imaging optical system of the electronic endoscope, and not displaying the subject image; The adjustment unit further determines whether fourth information related to the pixel value in the vignetting area satisfies an adjustment condition.

8. The endoscope system according to claim 7, wherein: The fourth information related to the pixel values ​​of the vignetting area includes at least one of the cumulative value of the pixel values ​​in the vignetting area, the number of pixels in the vignetting area whose pixel values ​​exceed a predetermined threshold, the change in the cumulative value calculated from the previous frame image of the current frame image, and the change in the number of pixels calculated from the previous frame image of the current frame image.

9. The endoscope system according to claim 1 or 2, wherein: The adjustment unit performs the adjustment determination each time the frame image is obtained from the imaging element, and when the determination result of the adjustment determination is affirmative, the value of the adjustment level is greater than the value of the adjustment level determined in the previous frame image.

10. The endoscope system according to claim 9, wherein: The adjustment unit performs a plurality of determinations as the adjustment determinations, and sets the determination result of the adjustment determination to affirmative when a determination result of at least one determination or at least two determinations among the plurality of determinations is affirmative.

11. The endoscope system according to claim 8, wherein: When the adjustment determination performed by the adjustment unit results in a negative result and the cumulative value of the pixel values ​​or the number of pixels in the vignetting area is greater than a predetermined threshold, the value of the adjustment level is maintained at the value of the adjustment level determined in the previous frame image.

12. The endoscope system according to claim 8, wherein: When the adjustment unit performs the adjustment judgment and the result of the judgment is negative, and the cumulative value of the pixel values ​​or the number of pixels in the vignetting area is less than or equal to the threshold, the value of the adjustment level in the current frame image is made smaller than the value of the adjustment level determined in the previous frame image.

13. The endoscope system according to claim 1 or 2, wherein: The adjustment unit includes an index calculation unit for calculating an index of the degree of generation of artifacts generated along a line corresponding to a scanning line of the imaging element by the rolling shutter method within the frame image. When the adjustment determination performed by the adjustment unit results in a negative result and the index is greater than a predetermined threshold, the adjustment level is maintained at the adjustment level determined in the previous frame image.

14. The endoscope system according to claim 13, wherein: When the adjustment determination performed by the adjustment unit results in a negative result and the index is less than or equal to a predetermined threshold, the adjustment level in the current frame image is made smaller than the adjustment level determined in the previous frame image.

15. The endoscope system according to claim 4, wherein: The adjustment unit includes a first reference table and a second reference table for determining the light intensity level relative to the light adjustment amount, the length of the exposure time, and the gain level of the gain adjustment. The product of the light intensity level, the exposure time, and the gain level of the gain adjustment relative to the value of the dimming amount is consistent between the first reference table and the second reference table over the entire range of possible values ​​of the dimming amount; on the other hand, the correspondence between the light intensity level and the value of the dimming amount, and the correspondence between the exposure time and the value of the dimming amount are different between the first reference table and the second reference table. The adjustment unit is configured to determine the adjustment values ​​of the light intensity level, the exposure time, and the gain level used in the adjustment process by interpolating between the first set value and the second set value corresponding to the first set value according to the adjustment level using a first set value and a second set value, wherein the first set value is the light intensity level, the exposure time, and the gain level determined by the first reference table based on the value of the dimming amount, and the second set value is the light intensity level, the exposure time, and the gain level determined by the second reference table based on the value of the dimming amount.

16. An endoscope system for displaying images of living tissue in a body cavity. It is characterized in that have: a light source device configured to generate illumination light for irradiating living tissue; An electronic endoscope having an imaging element configured to capture living tissue as a moving image using a rolling shutter method; A processor comprising: an image processing unit configured to perform image processing on a frame image obtained by imaging the imaging element; an index calculation unit configured to calculate an artifact generation index for indicating the degree of artifact generation along lines corresponding to scanning lines of the imaging element by the rolling shutter method within the frame image; and an adjustment unit configured to perform adjustment processing for adjusting the brightness of the frame image by combining at least one of adjustment for reducing the light intensity of the illumination light and gain adjustment for determining the signal level of an imaging signal of the frame image obtained by the imaging element, and adjustment for extending the exposure time of the imaging element, and configured to perform the adjustment processing by adjusting an adjustment level, whose value indicates the intensity of the adjustment processing, based on a result of determining whether the magnitude of the artifact generation index satisfies an adjustment condition; as well as A monitor displays the frame image that has been image processed.

17. The endoscope system according to claim 16, wherein: The adjustment unit is used to adjust parameters so that the brightness level of the current frame image obtained by the camera element reaches the target brightness level. When the brightness level of the current frame image is greater than the target brightness level, the currently set value is reduced; when the brightness level of the current frame image is less than the target brightness level, the currently set value is increased, and the brightness level of the image obtained by the camera element is adjusted by using the set dimming amount.

18. The endoscope system according to claim 17, wherein: The adjustment unit includes a first reference table and a second reference table for determining the light intensity level relative to the light adjustment amount, the length of the exposure time, and the gain level of the gain adjustment. The product of the light intensity level, the exposure time, and the gain level of the gain adjustment relative to the value of the dimming amount is consistent between the first reference table and the second reference table over the entire range of possible values ​​of the dimming amount; on the other hand, the correspondence between the light intensity level and the value of the dimming amount, and the correspondence between the exposure time and the value of the dimming amount are different between the first reference table and the second reference table. The adjustment unit is configured to determine the adjustment values ​​of the light intensity level, the exposure time, and the gain level used in the adjustment process by interpolating between the first set value and the second set value corresponding to the first set value according to the adjustment level using a first set value and a second set value, wherein the first set value is the light intensity level, the exposure time, and the gain level determined by the first reference table based on the value of the dimming amount, and the second set value is the light intensity level, the exposure time, and the gain level determined by the second reference table based on the value of the dimming amount.

19. The endoscope system according to claim 18, wherein: In either the first reference table or the second reference table, a product of the light intensity level, the exposure time, and the gain level relative to the maximum value of the dimming amount is greater than a product of the light intensity level, the exposure time, and the gain level relative to the minimum value of the dimming amount. In the entire range of possible values ​​of the dimming amount, the duration of the exposure time in the second reference table will not be less than the duration of the corresponding exposure time in the first reference table. In the entire range of possible dimming values, the product of the light intensity level value and the gain level value in the second reference table will not be greater than the product of the corresponding light intensity level value and the gain level value in the first reference table.

20. The endoscope system according to claim 18 or 19, wherein: The first reference table and the second reference table have the dimming amount range, and the dimming amount range is that, relative to the value of the dimming amount, the exposure time of the second reference table is longer than the exposure time of the first reference table, and the light intensity level of the second reference table is smaller than the light intensity level of the first reference table.

21. The endoscope system according to claim 18 or 19, wherein: The stronger the degree of the adjustment process, the larger the value of the adjustment level; and the larger the value of the adjustment level, the closer the adjustment value is to the second set value.

Images