Electronic Endoscope System

Abstract

To increase the frame rate of the image output from the image pickup device while suppressing the degradation of the image quality in the rolling shutter method, in an electronic endoscope system including an image pickup device that sequentially outputs image signals by being exposed with a time difference in a rolling shutter system.SOLUTION: The electronic endoscope system includes a processor having a processing unit for generating a display image from a captured image, and a timing controller for controlling the exposure timing of the image pickup device and the lighting timing of illumination light. Pixel regions of an image of the same frame in which the image pickup device is exposed includes: a pixel region A in which the period of the image pickup device being exposed includes a lighting period from the start of lighting to the end of lighting of the illumination light; and a pixel region B in which the period of the image pickup device being exposed does not include at least a portion of the lighting period. The processing unit generates an image, as the display image, which includes the pixel region A but does not include at least the portion of the pixel region B.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electronic endoscope system for imaging biological tissue. [Background technology]

[0002] The electronic endoscope system includes an electronic endoscope equipped with an imaging element for imaging biological tissue, a processor having a processing unit configured to process the image of the biological tissue captured to create an image for display, and a monitor connected to the processor and configured to display the created image for display.

[0003] In recent years, CMOS image sensors are often used as imaging elements in electronic endoscopes. When using a CMOS image sensor, the rolling shutter method is used as the exposure and output method for exposing the light receiving surface of the CMOS image sensor and outputting it as an image. The rolling shutter method divides the light receiving surface of the image sensor into multiple pixel regions of pixel units, and exposes each pixel region sequentially with a time difference. After sequentially resetting the accumulated charge for each pixel region, the accumulation of charge due to exposure begins, and the accumulated charge that becomes the image signal is output (read out).

[0004] In electronic endoscopes, biological tissue may be illuminated by turning on the illumination light in a pulsed manner at regular intervals. In this case, in the rolling shutter method, it is necessary to perform image exposure and image signal output in accordance with the lighting of the illumination light. In the rolling shutter method, the timing of lighting of the illumination light and the timing of exposure do not match, resulting in a problem of degradation of image quality, such as distortion in some pixel areas in the captured image. To solve this problem, in the rolling shutter method, exposure of each pixel area is started while shifting the timing of the exposure start by a certain time interval, and the exposure time length is extended so that the exposure period in all pixel areas includes the lighting period of the illumination light, that is, a global exposure period is provided in the exposure.

[0005] For example, an endoscope device has been proposed that is capable of acquiring high-quality, high-frame-rate observation images using an imaging unit built into the tip of the insertion portion of an endoscope (Patent Document 1). This endoscope device includes an endoscope scope that irradiates illumination light from the tip of an insertion section, captures images using an imaging section built into the tip of the insertion section, and outputs frame image signals obtained by imaging, and a processor device connected to the endoscope scope and having an image processing unit. The operation of emitting illumination light during the first half of a frame period obtained by dividing the frame period of the frame image signal in half and turning it off during the second half of the frame period is repeated for each frame period, while the first half of the frame period is the exposure period, and a signal of accumulated charge after exposure is read out during the second half and output to a buffer memory mounted in the endoscope. Image information of the frame image signal is read out from this buffer memory within the frame period and transferred to the image processing unit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-128024 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the above endoscope device, the first half of the frame cycle is a common exposure period for all pixel regions, all pixel regions are exposed simultaneously, and image signals are output (read out) sequentially after exposure. Therefore, in the above endoscope device, there is a limit to how much the frame rate of the image output from the imaging element can be increased, making it difficult to improve the frame rate.

[0008] The present invention aims to provide an electronic endoscope system that has an image sensor that exposes using a rolling shutter method and sequentially outputs image signals, and that can increase the frame rate of images output from the image sensor while suppressing degradation in image quality of the displayed image that occurs in the rolling shutter method. [Means for solving the problem]

[0009] One aspect of the present invention is an electronic endoscope system, comprising: an electronic endoscope having an image sensor configured to capture images of biological tissue by a rolling shutter method; a light source device configured to turn on illumination light at time intervals to illuminate the biological tissue; The imaging device includes a processor having a processing unit configured to generate an image for display from an image obtained by imaging of the imaging element, and a timing controller configured to control the timing of exposure of the imaging element and the timing of turning on the illumination light. the exposure time length for each pixel region when the image sensor captures an image using the rolling shutter method is the same, and the illumination light is turned on for a period of time shorter than the exposure time length; The pixel areas of the image of the same frame exposed by the imaging element using the rolling shutter method include a pixel area A in which the exposure period of the imaging element includes the lighting period from the start of lighting of the illumination light to its end, and a pixel area B in which the exposure period of the imaging element does not include at least a portion of the lighting period. The processing unit is configured to generate an image that includes pixel area A but excludes at least a portion of pixel area B as the display image.

[0010] the pixel area B includes a first pixel area that starts exposure first and a second pixel area that starts exposure last in the rolling shutter system in a pixel area of ​​an image of the same frame captured by the imaging element, It is preferable that the timing controller is configured to control the timing of turning on the illumination light and the exposure using the rolling shutter method so that the illumination light starts to be turned on after the exposure of the first pixel region starts, the exposure of the first pixel region ends and the exposure of the second pixel region starts after the illumination light starts to be turned on and before the illumination light ends, and the illumination light ends before the exposure of the second pixel region ends.

[0011] the first pixel region and the second pixel region are regions along both edges of the captured image, The processing unit is preferably configured to generate, as the display image, an image that does not include at least the first pixel region and the second pixel region.

[0012] It is preferable that the time difference between the start of illumination light and the end of exposure of the first pixel region is the same as the time difference between the start of exposure and the end of illumination light in the second pixel region.

[0013] It is preferable that the length of time from the start of illumination of the pre-illumination light to the end of the exposure in the first pixel region is the same as the length of time from the end of the exposure in the first pixel region to the end of illumination of the pre-illumination light.

[0014] It is also preferable that the length of time from the start of illumination of the pre-illumination light to the start of exposure in the second pixel region is the same as the length of time from the start of exposure in the second pixel region to the end of illumination of the pre-illumination light.

[0015] It is also preferable that the timing controller controls the timing of turning on the illumination light so that a selected area, a portion of the image of the frame selected as the display image, is included in pixel area A depending on a position within the image of the frame, thereby making the time difference between the start of turning on the illumination light and the end of the exposure of the first pixel area different from the time difference between the start of the exposure and the end of the illumination light in the second pixel area.

[0016] the imaging element sequentially outputs each of the pixel regions after the exposure of each of the pixel regions is completed; It is preferable that the exposure time length is the same as the time length that the imaging element outputs per image frame.

[0017] It is preferable that the lighting duration length is more than 0% and not more than 50% of the exposure time length.

[0018] It is preferable to include a monitor device configured to display the display image on a screen for the same length of time as the length of time it takes for the imaging device to output an image of one frame. Effect of the Invention

[0019] According to the above-mentioned electronic endoscope system, in an electronic endoscope system that uses an image sensor that exposes using a rolling shutter method and sequentially outputs image signals, it is possible to increase the frame rate of the image output from the image sensor while suppressing deterioration in the image quality of the displayed image. [Brief description of the drawings]

[0020] [Figure 1] 1 is a block diagram showing an example of a configuration of an endoscope system according to an embodiment; [Diagram 2] 1A to 1E are diagrams illustrating the timing of turning on illumination light, exposure, image output, and monitor display of a display image, which are performed in an endoscope system according to one embodiment. [Diagram 3] 13(a) and 13(b) are diagrams illustrating an example of a preferable embodiment of the relationship between the exposure timing of pixel regions R1 and RN and the illumination light lighting timing. [Figure 4] 2(a) and 2(b) are diagrams illustrating an example of image processing different from the image processing for monitor display shown in FIGS. 2(d) and 2(e). [Diagram 5] 13A and 13B are diagrams illustrating the timing of lighting of an illumination light according to another embodiment. [Figure 6] 1A to 1E are diagrams illustrating the timing of exposure using a conventional rolling shutter method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the endoscope system will be described in detail with reference to the accompanying drawings. The endoscope system includes an electronic endoscope, a light source device, and a processor. The electronic endoscope includes an image sensor configured to capture images of biological tissue using a rolling shutter system, a light source device configured to turn on illumination light at time intervals to illuminate the biological tissue, and a processor including a processing unit configured to generate a display image from an image captured by the image sensor, and a timing controller configured to control the timing of exposure of the image sensor and the timing of turning on the illumination light.

[0022] In such an endoscope system, conventionally, the timing of exposure is set so that a global exposure period sharing the same lighting period can be set for each pixel area that is sequentially exposed by the rolling shutter method when the illumination light is turned on, so that the pixel areas are exposed during the same lighting period. However, in this case, since all pixel areas are configured to share the same lighting period, the length of time from the start of exposure of the pixel area that is exposed first to the end of exposure of the pixel area that is exposed last is the time length obtained by multiplying the time difference for shifting the timing of exposure start between pixel areas by (the number of pixel areas - 1) and adding the result to the exposure time length from the start of exposure to the end of exposure in one pixel area. Figures 6(a) to (e) are diagrams explaining the timing of exposure using the conventional rolling shutter method.

[0023] During the illumination light illumination duration T2 shown in FIG. 6(b), the pixel regions R1 to R N As shown in FIG. 6(c), pixel regions R1 to R NImmediately after the end of the exposure, the image sensor sequentially outputs the accumulated signal, so the time length is calculated by multiplying the time difference by (the number of pixel regions - 1) and adding the exposure time length from the start of exposure to the end of exposure. Therefore, as shown in Fig. 6(d), captured images are obtained in a cycle obtained by adding the time length T1, which is the result of multiplying the time difference by the number of pixel regions to be exposed sequentially, to the lighting duration length T2. Therefore, the captured images are displayed on the monitor so that they are switched at a cycle of (T1 + T2), as shown in Fig. 6(e). In this way, the captured images are displayed on the monitor in a switching manner at a long cycle of (T1+T2), so the frame rate at which the images are displayed on the monitor is slow.

[0024] In this embodiment, the exposure time length for each pixel region when the image sensor captures an image using the rolling shutter method is the same, and the illumination light on duration length T2 is shorter than the exposure time length. The timing of illumination light on is adjusted so that the pixel regions of the image of the same frame exposed by the image sensor include a pixel region A whose exposure period of the image sensor includes an on-period from the start of illumination light on to the end of illumination light on, and a pixel region B whose exposure period of the image sensor does not include at least a part of the on-period. That is, the exposure period of all pixel regions does not have a global exposure period in which the exposure period is shared. In this case, in the image captured by the image sensor, the amount of exposure light of the pixel region B is smaller than the amount of exposure light of the pixel region A, so the luminance of the pixel region B is low, and the image quality of a part of the pixel region B is easily deteriorated compared to the pixel region A. For this reason, an image including the pixel region A but not including at least a part of the pixel region B is generated as a display image to be displayed on a monitor from the captured image. By adjusting the duration T2 of illumination light for exposure of each pixel region and the timing of illumination, the area occupied by pixel region B can be made smaller than the area occupied by pixel region A, so that the pixel region B, which is not displayed as a display image and has a large deterioration in image quality, can be made smaller. In an endoscope system, the inner wall surface of a duct such as an organ is often imaged, and the image of the inner wall surface of the duct is often displayed within a circular or elliptical outer frame, and the image of the edge periphery including the corners of a rectangular image is often masked and displayed. Therefore, while the frame rate of the display image is improved, at least a part of the pixel region B, which has a poor image quality, is not displayed from the display image by being masked or the like. In this way, in the rolling shutter method, while sacrificing the formation of an area with poor image quality in the image, the image can be displayed on the monitor so that the captured image is switched at a period of time length T1, that is, the frame rate is improved.

[0025] 1 is a block diagram showing an example of the configuration of an endoscope system 1 according to an embodiment. As shown in FIG. 1, the electronic endoscope system 1 includes an electronic scope 100, an electronic endoscope processor 200, a monitor 300, and a printer 400.

[0026] The electronic endoscope processor 200 includes a system controller 202 and a timing controller 206. The system controller 202 executes various programs stored in a memory 204 and comprehensively controls the entire electronic endoscope system 1. The system controller 202 also changes various settings of the electronic endoscope system 1 in response to instructions from a user (surgeon or assistant) inputted to an operation panel 208. The timing controller 206 outputs clock pulses to each circuit in the electronic endoscope system 1 to adjust the timing of the operation of each part.

[0027] The electronic endoscope processor 200 includes a light source device 230 that supplies illumination light to the electronic scope 100. The light source device 230 includes, for example, a high-intensity lamp that emits white illumination light by receiving driving power from a lamp power supply (not shown), such as a xenon lamp, metal halide lamp, mercury lamp, or halogen lamp. The light source device 230 is configured so that the illumination light emitted from the high-intensity lamp is focused by a focusing lens (not shown) and then incident on an entrance end of an LCB (Light Carrying Bundle) 102, which is a bundle of optical fiber strands of the electronic scope 100, via a dimming device (not shown). Alternatively, the light source device 230 includes a plurality of light-emitting diodes that emit light in a wavelength band of a predetermined color. The light emitted from the light-emitting diodes is combined using an optical element such as a dichroic mirror, and the combined light is focused as illumination light by a focusing lens (not shown), and then input to an input end of an LCB (Light Carrying Bundle) 102 of the electronic scope 100. The LCB 102 is a bundle of optical fiber strands. A laser diode can be used instead of the light-emitting diode. Compared to other light sources, light-emitting diodes and laser diodes have characteristics such as low power consumption and low heat generation, and therefore have the advantage of being able to obtain a bright image while suppressing power consumption and heat generation. The ability to obtain a bright image can improve the accuracy of evaluation of the degree of the lesion in the lesion. 1, the light source device 230 is built into the electronic endoscope processor 200, but may be provided in the electronic endoscope system 1 as a device separate from the electronic endoscope processor 200. The light source device 230 may also be provided at the tip of the electronic scope 100, which will be described later. In this case, the LCB 102 for guiding the illumination light is not necessary.

[0028] Illumination light entering the LCB 102 from the entrance end propagates through the LCB 102, exits from the exit end of the LCB 102 located in the tip of the electronic scope 100, and is irradiated onto the subject via a light distribution lens 104. Light reflected from the subject forms an optical image on the light receiving surface of an image sensor 108 via an objective lens 106.

[0029] The imaging element 108 is, for example, a single-chip color CCD (Charge-Coupled Device) image sensor with various filters, such as an IR (Infra Red) cut filter 108a and a Bayer array color filter 108b, arranged on the light-receiving surface, and generates primary color signals of R (Red), G (Green), and B (Blue) according to the optical image formed on the light-receiving surface. Instead of a single-chip color CCD image sensor, a single-chip color CMOS (Complementary Metal Oxide Semiconductor) image sensor can also be used.

[0030] A driver signal processing circuit 112 is provided in the connection section of the electronic scope 100. The driver signal processing circuit 112 performs predetermined signal processing such as color interpolation and matrix calculation on the primary color signals input from the image sensor 108 to generate image signals (luminance signal Y, color difference signals Cb, Cr), and outputs the generated image signals to the image processing unit 220 of the electronic endoscope processor 200. The driver signal processing circuit 112 also accesses the memory 114 to read out the unique information of the electronic scope 100. The unique information of the electronic scope 100 recorded in the memory 114 includes, for example, the number of pixels and sensitivity of the image sensor 108, the operable frame rate, the model number, etc. The driver signal processing circuit 112 outputs the unique information read out from the memory 114 to the system controller 202. In this way, the electronic scope 100 uses the image sensor 108 to capture images of biological tissue in a body cavity.

[0031] The system controller 202 performs various calculations based on the unique information of the electronic endoscope 100 and generates a control signal. Using the generated control signal, the system controller 202 controls the operation and timing of each circuit in the electronic endoscope processor 200 so that processing suitable for the electronic endoscope 100 connected to the electronic endoscope processor 200 is performed.

[0032] The timing controller 206 generates a timing signal composed of clock pulses in accordance with timing control by the system controller 202, and supplies this timing signal to the image sensor 108, the driver signal processing circuit 112, the image processing unit 220, and the light source device 230. The driver signal processing circuit 112 is driven in accordance with the clock pulses of the timing signal supplied from the timing controller 206.

[0033] Under the control of the system controller 202, the image processing unit 220 generates a video signal for displaying an endoscopic image, etc. on the monitor based on the image signal input from the driver signal processing circuit 112 in accordance with a timing signal, and outputs the video signal to the monitor 300.

[0034] 2(a) to (e) are diagrams for explaining the timing of turning on the illumination light, exposing the image sensor 108, outputting the image from the image sensor 108, and displaying the display image on the monitor, which are performed in the endoscope system 1 of one embodiment. As shown in FIG. 2(a), the timing controller 206 generates clock pulses at intervals of time length T1 and sends them to the light source device 230 and the image sensor 108. The time length T1 is a predetermined length obtained by multiplying the time difference between the start or end of exposure between pixel regions in the rolling shutter method by the number of pixel regions to be sequentially exposed, and is also the length of time required to output an image signal for one frame of image. In synchronization with the clock pulse, the light source device 230 turns on the illumination light for a duration of time length T2 during which the illumination light is turned on. In synchronization with this clock pulse, the image sensor 108 performs exposure. In the following explanation, an example will be explained in which the exposure of the rolling shutter method by the image sensor 108 is performed for each row of light receiving sections arranged in one direction among a plurality of light receiving sections arranged in a lattice on the light receiving surface of the image sensor 108. In this case, the image sensor 108 exposes the pixel regions for each row, so that the pixel regions R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R20, R21, R22, R23, R24, R25, R26, R27, R28, R39, R41, R42, R45, R46, R51, R52, R53, R54, R65, R66, R67, R68, R79, R79, R88, R89, R89, R90, R91, R92, R93, R94, R95, R96, R97, R98, R98, R99, R99, R99, R99, R109, R110, R120, R130, R14 N (N is a natural number), the exposure start timing is shifted by a certain time difference, and the pixel areas R1 to R NThe exposure time length is T1 in each pixel region. N The end of exposure is the pixel area R1 in order. N This is done with a certain time lag up to (N is a natural number). In FIG. 2(c), a pixel region R1 where exposure is started first and a pixel region R where exposure is started last are shown. N The exposure period of the pixel area R1 is shown by a dotted line with arrows on both sides. During the exposure period, the period during which the illumination light is turned on is shown by the solid arrow areas EP1 and EP2. N In this case, the image sensor 108 receives light only for a part of the illumination light illumination duration T2, so the amount of light received in this area is small and the brightness of the image is low. k1 From pixel area R k2 In the pixel regions between k1 and k2 (k1 being natural numbers), the shutter is open (the image sensor 108 receives light) during the entire illumination light illumination duration T2, so the brightness of the image in this region is appropriate. In other words, these pixel regions are pixel region A, where the period during which the image sensor 108 is exposed includes the illumination light illumination period from when the illumination light starts to when it ends. Therefore, in the pixel regions between pixel region R1 and pixel region R (k1-1) and pixel area R (k2+1) From pixel area R N The pixel region from pixel region R1 to pixel region R2 is a pixel region B in which the exposure period of the image sensor 108 does not include at least a part of the lighting period. (k1-1) In the pixel area up to, the pixel area is (k1-1) As the pixel area R (k2+1) From pixel area R N In the pixel area up to, the pixel area is (k2+1) As the distance approaches , the amount of received light increases and the brightness of the image increases.

[0035] When the exposure of each pixel area is completed, the charge accumulated on the light receiving surface of the image sensor 108 is extracted and an image signal is output immediately after the exposure is completed. The image signal is output from the image sensor 108 in the order of the start of exposure of the pixel areas in the rolling shutter system. N When the output of the light reception signal in ends, one frame of a captured image is output. In this way, while the captured image is being obtained, the image sensor 108 performs exposure for the next frame of the image by the rolling shutter method.

[0036] In the captured image, pixel area R1 to pixel area R (k1-1) and pixel area R (k2+1) From pixel area R N The pixel region up to is pixel region B which does not receive light during at least a portion of the illumination light illumination period, and therefore the luminance in this pixel region is low. In the rolling shutter method, exposure starts in order from the edge of the captured image, from pixel area R1 to pixel area R (k1-1) and pixel area R (k2+1) From pixel area R N The pixel region up to (the region of width W1 shown in FIG. 2(d)) is a region adjacent to the edge of the captured image. Therefore, the image processing unit 220 performs processing to generate an image for display that includes the pixel region A but does not include at least a part of pixel region B. For example, it performs masking processing on pixel regions that are not to be displayed, or performs zoom processing to enlarge pixel regions that are to be displayed. Note that the width W1 of pixel region B changes depending on the timing of the start and end of illumination light turn-on relative to the start and end of exposure of each pixel region. In this way, the image for display that does not include at least a part of the pixel region B includes the image for display not including the entire pixel region B, and the image for display including a part of the pixel region B. (k1-1) and its neighboring pixel areas, and pixel area R (k2+1)Although the time for which pixel area B and the pixel areas nearby receive illumination light is shorter than that of pixel area A, the difference is small and there is no problem with the brightness of the image to be displayed, so the image to be displayed may also include part of pixel area B. FIG. 2(e) shows an example in which the image processing unit 220 performs mask processing.

[0037] In this way, since the exposure time length is set to time length T1, the image sensor 108 outputs an image at intervals of time length T1. For this reason, the image processing unit 220 processes the image sent from the electronic scope 100 at intervals of time length T1, and further performs masking to mask a dark area of ​​width W1 to generate an image for display. Therefore, the monitor 300 displays the image for display that has been subjected to the masking process and sent at intervals of time length T1. This allows the frame rate of the display image to be set to time length T1.

[0038] As described above, the pixel area B is divided into a pixel area R1 that starts exposure first and a pixel area R N The timing controller 206 controls the timing of the illumination light being turned on after the exposure of the pixel region R1 is started, and the timing of the exposure of the pixel region R1 being ended after the exposure of the pixel region R2 is ended. N The exposure of the pixel region R is started after the illumination light starts to be turned on and before the illumination light ends. N The timing of turning on the illumination light and the exposure by the rolling shutter method are controlled so that the exposure is performed before the end of the exposure of pixel area R1 and pixel area R2. N Between these, there is always a pixel area A whose exposure period includes the lighting period from when the illumination light starts to turn on until it ends, so that a display image that reliably includes pixel area A can be easily created.

[0039] As described above, pixel area R1 and pixel area R N are areas along both edges of the captured image, and the image processing unit 220 processes pixel areas R1 and R2 as an image to be displayed. NSince the image is configured to generate an image that does not include at least the above, it is suitable for displaying an image of the inner wall surface of a tube such as an organ within a circular or elliptical outer frame by masking the edges and corners on both sides of a rectangular image.

[0040] 3(a) and (b) show pixel areas R1 and R N 10A and 10B are diagrams illustrating an example of a preferred embodiment of the relationship between the timing of exposure and the timing of turning on the illumination light. According to one embodiment, as shown in FIG. 3(a), the time difference between the start of illumination light and the end of exposure of pixel region R1 (the time length of arrow region EP1 in FIG. 3(a)) is N It is preferable that the time difference between the start of exposure and the end of illumination light in the image (the time length of the arrow region EP2 in FIG. 3(a)) is the same as the time difference between the start of exposure and the end of illumination light in the image (the time length of the arrow region EP2 in FIG. 3(a)), because pixel region B has the same width W1 along the edge of the image and masking and zooming can be performed so that the central portion of the image becomes the image for display. The above two time differences being the same includes not only the case where the time differences are identical, but also the case where the time differences deviate within an acceptable range. Within an acceptable range means that the difference between the two time lengths being compared deviates by 10% or less, preferably 5% or less, of the average value of the two time lengths.

[0041] According to an embodiment, as shown in FIG. 3B, the time length T from the start of illumination light to the end of exposure in the pixel region R1 is a1 is the time length T from the end of exposure to the end of illumination in the pixel area R1 b1 Even if the lighting duration T2 is changed, the pixel area R1 to the pixel area R (k1-1) Since the width W1 of the pixel region B up to the pixel region B can be obtained using the changed lighting duration T2, masking and zooming can be performed efficiently. The above two time lengths being the same includes not only the case where the time lengths match, but also the case where the time lengths deviate within an allowable range. Deviating within an allowable range means that the difference between the two time lengths deviates by 10% or less, preferably 5% or less, of the average value of the two time lengths.

[0042] Similarly, from the start of illumination light illumination, pixel region R N The time length T until the start of exposure b2 is the pixel area R N The time length T from the start of exposure to the end of illumination light a2 Even if the lighting duration T2 is changed, the pixel area R (k2+1) Since the illumination duration T2 obtained by changing the width W1 of the pixel region from the pixel region R1 to the pixel region R2 can be used to obtain the illumination duration T2, mask processing and zoom processing can be performed efficiently. The above two time lengths being the same includes not only the case where the time lengths match, but also the case where the time lengths deviate within an allowable range. Deviating within an allowable range means that the difference between the two time lengths being compared deviates by 10% or less, preferably 5% or less, of the average value of the two time lengths.

[0043] 4(a) and (b) are diagrams for explaining an example of image processing different from the image processing for monitor display shown in Fig. 2(d) and (e). In the above embodiment, the image processing unit 220 performs mask processing, but as shown in Fig. 4(a) and (b), a rectangular area indicated by a dotted line may be zoomed to produce an image for display.

[0044] According to one embodiment, the timing controller 206 controls the timing of illumination light so that the selected region, which is a part of an image of one frame selected as an image for display, is included in the pixel region A according to the position of the image of the frame, and adjusts the time difference between the start of illumination light illumination and the end of exposure of the pixel region R1 (the time length of the arrow region EP1 shown in FIG. 3(a)) to the pixel region R1. NIt is also preferable to make the time difference between the start of exposure and the end of illumination light illumination in the pixel region R1 different from the time length of the arrow region EP2 shown in FIG. 3(a). FIGS. 5(a) and (b) are diagrams for explaining the timing of illumination light illumination in one example of this embodiment. As shown in FIG. 5(b), the upper left image region of the image displayed on the monitor 300 may be set as a selected region S, and the image of the selected region S may be zoomed to create an image for display. In this case, it is preferable to control the timing of illumination light illumination in accordance with the selected region S. When the selected region S shown in FIG. 5(b) is zoomed to create an image for display, the timing of illumination light illumination is shifted forward in the figure to change the length of illumination time during the exposure period in the pixel region R1 to the length of illumination time during the exposure period in the pixel region R2, as shown in FIG. 5(a). N By making the lighting time longer than the length of the exposure period in the selection area S, the pixel area corresponding to the selection area S can be made into a bright image.

[0045] According to one embodiment, the image sensor 108 outputs each pixel region sequentially after the exposure of each pixel region is completed, and the exposure time length is preferably the same as the time length output by the image sensor 108 per image of one frame, as shown in Fig. 2(c) and (d). This makes it possible to ensure a long exposure time while shortening the total time of the exposure time and the output of the pixel region in the rolling shutter method. The above two time lengths being the same includes not only the case where the time lengths are the same, but also the case where the time lengths deviate within an allowable range. The deviating within an allowable range means that the difference between the two time lengths to be compared is 10% or less, preferably 5% or less, of the average value of the two time lengths. The monitor 300 is preferably configured to display the display image on the screen for the same time length as the time length for the image sensor 108 to output one frame image. In other words, the display image can be switched for each time length for the image sensor 108 to output one frame image, so that the frame rate of the display image can be improved compared to the frame rate of the conventional technology shown in FIG. 6. The above two time lengths being the same includes not only the case where the time lengths match, but also the case where the time lengths are shifted within an allowable range. The term "within an allowable range" means that the difference between the two time lengths being compared is 10% or less, preferably 5% or less, of the average value of the two time lengths.

[0046] The illumination light on duration T2 in the light source device 230 (see FIG. 2(b)) is preferably more than 0% and not more than 50% of the exposure time. By setting the illumination light on duration T2 within this range, the width W1 of the pixel region B can be narrowed, and a wide display image can be extracted from the image captured by the image sensor by masking and zooming. More preferably, the illumination light on duration T2 is more than 5% and not more than 30% of the exposure time.

[0047] The above describes the endoscopic system of the present invention in detail, but the present invention is not limited to the above-described embodiments and examples, and it goes without saying that various improvements and modifications may be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0048] 1. Electronic endoscope system 100 Electronic Scope 102 LCB 104 Orientation Lens 106 Objective Lens 108 Image sensor 108a Cut Filter 108b Bayer color filter 112 Driver signal processing circuit 114 Memory 200 Electronic endoscope processor 202 System Controller 204 Memory 206 Timing Controller 208 Operation Panel 220 Image Processing Unit 230 Light source section 300 Monitors 400 Printer

Claims

1. an electronic endoscope having an image sensor configured to capture images of biological tissue by a rolling shutter method; a light source device configured to turn on illumination light from a high-intensity lamp at time intervals to illuminate the biological tissue; a processor including a processing unit configured to generate a display image from an image obtained by imaging with the imaging element, and a timing controller configured to control the timing of exposure of the imaging element and the timing of lighting of the illumination light, the exposure time length for each pixel region when the image sensor captures an image using the rolling shutter method is the same, and the illumination light is turned on for a period of time shorter than the exposure time length; a pixel area of ​​an image of the same frame exposed by the image sensor in the rolling shutter system includes a pixel area A in which an exposure period of the image sensor includes a lighting period from a start of lighting of the illumination light to an end of lighting of the illumination light, and a pixel area B in which an exposure period of the image sensor does not include at least a part of the lighting period; the processing unit is configured to generate, as the display image, an image that includes the pixel area A but does not include at least a portion of the pixel area B; the pixel area B includes a first pixel area that starts exposure first and a second pixel area that starts exposure last in the rolling shutter system in a pixel area of ​​an image of the same frame captured by the imaging element, the timing controller is configured to control timing of turning on the illumination light and exposure by the rolling shutter method so that turning on the illumination light starts after exposure of the first pixel region starts, exposure of the first pixel region ends and exposure of the second pixel region starts after turning on the illumination light starts and before the turning on of the illumination light ends, and turning on the illumination light ends before exposure of the second pixel region ends; the timing controller controls a timing of turning on the illumination light so that a selected area, which is a part of the image of the frame selected as the display image, is included in the pixel area A according to a position of the image of the frame, and controls so that a time difference between a start of turning on the illumination light and an end of the exposure of the first pixel area is made different from a time difference between the start of the exposure and an end of the illumination light in the second pixel area; The electronic endoscope system according to claim 1, wherein the selected area includes a part of the pixel area B.

2. The electronic endoscope system according to claim 1 , wherein a time length from a start of illumination light to an end of exposure in the first pixel region is equal to a time length from the end of exposure in the first pixel region to an end of illumination light.

3. 3. The electronic endoscope system according to claim 1, wherein a time length from a start of illumination light to a start of exposure in the second pixel region is the same as a time length from a start of exposure in the second pixel region to an end of illumination light.

4. the imaging element sequentially outputs each of the pixel regions after the exposure of each of the pixel regions is completed; 4. The electronic endoscope system according to claim 1, wherein the exposure time length is the same as the time length for which the image sensor outputs one frame of image.

5. 5. The electronic endoscope system according to claim 1, wherein the lighting duration is more than 0% and not more than 50% of the exposure time.

6. 6. The electronic endoscope system according to claim 1, further comprising a monitor device configured to display the display image on a screen for the same length of time as the length of time it takes for the imaging element to output an image of one frame.

Images