JP6067309B2 - Endoscope system and endoscope processor - Google Patents

Description

  The present invention relates to an endoscope system for performing in-vivo observation, and more particularly to an endoscope system and an endoscope processor having a black balance adjustment function.

  Conventionally, an endoscope system using an endoscope for diagnosing the inside of a body cavity of a patient is generally known and put into practical use. In recent years, a scanning endoscope system that scans light guided by an optical fiber with respect to an observation site and receives reflected light from the observation site to form an image is also known. Furthermore, as one of the scanning endoscope systems, a living tissue to which a drug is administered is irradiated with laser light, and the fluorescence emitted from the living tissue is placed at a position conjugate with the focal position of the confocal optical system. A scanning confocal endoscope system is also proposed that enables the observation of the living tissue at a higher magnification than the observation image obtained by a normal endoscope optical system by extracting only the components through the pinhole. Has been.

  Here, in an endoscope system, variations in image color reproducibility occur due to differences in illumination light sources that irradiate a subject, differences in spectral sensitivity of individual image sensors, and the like. Therefore, the color of the subject in the observation image is faithfully reproduced by adjusting the black balance. Patent Document 1 discloses an electronic endoscope apparatus capable of performing appropriate black balance adjustment according to the type of electronic endoscope. In the electronic endoscope apparatus described in Patent Document 1, the iris is closed in accordance with a black balance adjustment instruction from the outside, and the black balance is adjusted to be appropriate. Then, the adjustment value obtained by the adjustment is stored in the processor together with the identification information of the electronic endoscope, and is used for the subsequent black balance adjustment. With such a configuration, it is possible to perform an appropriate black balance adjustment according to the type of electronic endoscope.

JP 11-197103 A

  However, even when observation is performed using the same endoscope, the optimum black balance also changes due to changes in the use environment, use time, and photographing target. Therefore, when the black balance is adjusted using the black balance value set by the single adjustment before the actual observation as in Patent Document 1, these changes cannot be dealt with and the color of the subject is faithful. May not be reproduced. Further, in the observation using the confocal endoscope, since the acquired signal is amplified and displayed, a slight signal difference appears as a large difference on the image. Furthermore, since the confocal image is monochrome, it is more important to represent black accurately than a color image.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an endoscope system and an endoscope that are capable of adjusting an optimum black balance in accordance with a change in use environment or the like. Is to provide a processor.

  In order to achieve the above object, an endoscope system according to the present invention includes an image acquisition unit that acquires an image of a subject, and a black balance adjustment unit that performs black balance adjustment on an image acquired by the image acquisition unit. And black level setting means for setting a black level used for black balance adjustment in the black balance adjusting means. Further, the image acquisition means in the endoscope system of the present invention includes a first image in a state where the subject is irradiated with light and a second image in a state where the illumination light is not irradiated during observation of the subject. The acquired black level setting means sets the black level based on the second image.

  With such a configuration, it is possible to perform an optimum black balance adjustment according to a change in the environment or the like based on a black image acquired during observation. Accordingly, it is possible to display and observe a stable observation image with excellent color reproducibility, and it is possible to improve diagnostic ability.

  The endoscope system further includes a light source that supplies light irradiated to the subject, and the image acquisition unit guides light from the light source incident on the incident end to the output end, and the subject from the output end. The output end of the optical fiber and the light output from the output end of the optical fiber during the imaging period scan the subject, and the output end of the optical fiber returns to the initial position during the braking period. It is good also as a structure provided with the optical fiber scanning means to drive. In this case, the second image may be acquired during the braking period. With this configuration, it is not necessary to set the black level using a special light-shielding device before observation, and the black level can be set in real time without imposing a burden on the user.

  The black level setting means includes variable means for gradually increasing the provisional black level, compares the pixel level of at least some of the pixels in the second image with the provisional black level, and the pixel level is higher than the provisional black level. In the case where it is small, the provisional black level may be set as the black level. Further, the black level setting means may be configured to return the provisional black level to the initial value after setting the black level. With this configuration, even when there is a change in environment during observation, it is possible to set an optimal black level without depending on the already set black level.

  Further, the black level setting means may be configured to set the black level for all the second images acquired during observation, or to set the black level according to an instruction from the user. Furthermore, the endoscope system of the present invention may be a confocal endoscope system.

  Further, according to the present invention, a black balance adjusting unit that adjusts a black balance for an image of a subject acquired by the image acquiring unit, and a black level that sets a black level used for black balance adjustment in the black balance adjusting unit. A black level setting unit, wherein the black level setting unit sets the black level based on an image obtained by irradiating light on the subject acquired by the image acquisition unit during observation of the subject. An endoscopic processor is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the endoscope system and the processor for endoscopes which can adjust optimal black balance according to change of a use environment etc. are provided.

It is a block diagram which shows the structure of the scanning confocal endoscope system of embodiment of this invention. It is a figure which shows schematically the structure of the confocal optical unit which the scanning confocal endoscope system of embodiment of this invention has. It is a figure which shows the displacement amount of the X and Y direction of the front-end | tip of an optical fiber on an XY approximate surface. It is a figure which shows the rotation locus | trajectory of the front-end | tip of an optical fiber on an XY approximate surface. It is a flowchart which shows the black level setting process in embodiment of this invention. It is a figure explaining the area | region extracted in a black level setting process. It is a figure explaining the detection of the black data in a black level setting process.

  Hereinafter, an endoscope system according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case where the present invention is applied to a scanning confocal endoscope system will be described.

  FIG. 1 is a block diagram showing a configuration of a scanning confocal endoscope system 1 according to an embodiment of the present invention. The scanning confocal endoscope system 1 according to the present embodiment is a system designed by applying the principle of a confocal microscope, and is preferably configured to observe a subject with high magnification and high resolution. As shown in FIG. 1, the scanning confocal endoscope system 1 includes a system main body (processor) 100, a confocal probe 200, and a monitor 300. The confocal observation using the scanning confocal endoscope system 1 is performed in a state where the distal end surface of the flexible tubular confocal probe 200 is applied to the subject.

  The system body 100 includes a light source 102, an optical demultiplexer / multiplexer (photocoupler) 104, a damper 106, a CPU 108, a CPU memory 110, an optical fiber 112, a light receiver 114, a video signal processing circuit 116, an image memory 118, and a video signal output. A circuit 120 and a photoreceiver control circuit 122 are included. In another embodiment, the light source unit including the light source 102 may be provided as a separate body. The confocal probe 200 includes an optical fiber 202, a confocal optical unit 204, a sub CPU 206, a sub memory 208, and a scanning driver 210.

  The light source 102 emits excitation light that excites the drug administered into the body cavity of the patient in accordance with the drive control of the CPU 108. The excitation light enters the optical demultiplexer / multiplexer 104. An optical connector 152 is coupled to one of the ports of the optical demultiplexer / multiplexer 104. The unnecessary port of the optical demultiplexer-multiplexer 104 is coupled to a damper 106 that terminates the excitation light emitted from the light source 102 without reflection. The excitation light incident on the former port passes through the optical connector 152 and enters the optical system arranged in the confocal probe 200.

  The proximal end of the optical fiber 202 is coupled to the optical demultiplexer / multiplexer 104 through the optical connector 152. The tip of the optical fiber 202 is housed in a confocal optical unit 204 that is built into the tip of the confocal probe 200. The excitation light emitted from the optical demultiplexer-multiplexer 104 passes through the optical connector 152 and is incident on the proximal end of the optical fiber 202, then transmitted through the optical fiber 202 and emitted from the distal end of the optical fiber 202.

  FIG. 2A is a diagram schematically showing the configuration of the confocal optical unit 204. Hereinafter, for convenience of describing the confocal optical unit 204, the longitudinal direction of the confocal optical unit 204 is defined as the Z direction, and two directions orthogonal to the Z direction and orthogonal to each other are defined as the X direction and the Y direction. As shown in FIG. 2A, the confocal optical unit 204 has a metal outer cylinder 204A that houses various components. The outer cylinder 204A holds an inner cylinder 204B having an outer wall surface shape corresponding to the inner wall surface shape of the outer cylinder 204A so as to be slidable coaxially (Z direction). The optical fiber 202 is housed and supported in the inner cylinder 204B through openings formed in the base end surfaces of the outer cylinder 204A and the inner cylinder 204B, and the distal end of the optical fiber 202 (hereinafter referred to as “202a”) is provided. It functions as a secondary point light source of the scanning confocal endoscope system 1. The position of the tip 202a, which is a point light source, periodically changes based on control by the CPU. In FIG. 2A, the central axis AX indicates the axis of the optical fiber 202 arranged in the Z direction, and when the tip 202a of the optical fiber 202 is not oscillating (initial state), The central axis AX coincides with the optical path of the optical fiber 202.

  The sub memory 208 stores probe information such as identification information and various properties of the confocal probe 200. The sub CPU 206 reads probe information from the sub memory 208 when the system is activated, and transmits the probe information to the CPU 108 via the electrical connector 154 that electrically connects the system main body 100 and the confocal probe 200. The CPU 108 stores the transmitted probe information in the CPU memory 110. The CPU 108 reads the stored probe information when necessary, generates a signal necessary for controlling the confocal probe 200, and transmits the signal to the sub CPU 206. The sub CPU 206 designates a setting value necessary for the scan driver 210 in accordance with the control signal transmitted from the CPU 108.

  The scanning driver 210 generates a drive signal corresponding to the designated set value, and drives and controls the biaxial actuator 204C that is bonded and fixed to the outer peripheral surface of the optical fiber 202 near the tip 202a. FIG. 2B is a diagram schematically showing the configuration of the biaxial actuator 204C. As shown in FIG. 2B, the biaxial actuator 204C includes a pair of X-axis electrodes (“X” and “X ′” in the figure) and Y-axis electrodes (in the figure) connected to the scanning driver 210. “Y”, “Y ′”) are piezoelectric actuators formed on a piezoelectric body.

  The scanning driver 210 applies an AC voltage X between the X-axis electrodes of the biaxial actuator 204C to resonate the piezoelectric body in the X direction, and also applies an AC voltage Y having the same frequency as that of the AC voltage X and orthogonal in phase. Applied between the Y-axis electrodes, the piezoelectric body resonates in the Y direction. The AC voltages X and Y are respectively defined as voltages that increase linearly in proportion to time and reach effective values (X) and (Y) over time (X) and (Y). The tip 202a of the optical fiber 202 is on a surface that approximates the XY plane (hereinafter referred to as "XY approximate surface") by combining the kinetic energy in the X and Y directions by the biaxial actuator 204C. Rotate to draw a spiral pattern around the central axis AX. The rotation trajectory of the tip 202a increases in proportion to the applied voltage, and draws a circular trajectory having the largest diameter when the AC voltage having the effective values (X) and (Y) is applied.

  3A and 3B show the relationship between the displacement amounts (amplitudes) of the tip 202a of the optical fiber 202 on the XY approximate plane in the X and Y directions and the operation timings of the confocal endoscope 200, respectively. It is a figure explaining. The excitation light is continuous light, and during the period from the start of application of AC voltage to the biaxial actuator 204C to the stop of application (hereinafter, for convenience of description, this period is referred to as “imaging period”). The light is emitted from the tip 202a. As described above, when an AC voltage is applied to the biaxial actuator 204C, the tip 202a of the optical fiber 202 rotates so as to draw a spiral pattern around the central axis AX. The excitation light emitted from the tip 202a of the 202 scans a predetermined circular scanning area centering on the central axis AX in a spiral shape. FIG. 4A is a diagram illustrating a rotation locus of the tip 202a on the XY approximate plane in the imaging period.

  Thereafter, when the imaging period ends and the application of the AC voltage to the biaxial actuator 204C is stopped, the vibration of the optical fiber 202 is attenuated. The circular motion of the tip 202a on the approximate XY plane converges as the vibration of the optical fiber 202 is attenuated, and the vibration of the optical fiber 202 becomes substantially zero after a predetermined time (that is, the tip 202a is on the central axis AX). Almost stop). Hereinafter, for convenience of explanation, a period from the end of the imaging period until the tip 202a substantially stops on the central axis AX is referred to as a “braking period”. FIG. 4B shows a rotation locus of the tip 202a on the XY approximate surface during the braking period. After the braking period, the next imaging period is started after a predetermined time has passed. Hereinafter, for convenience of description, a period from the end of the braking period to the start of the next imaging period is referred to as a “settling period”. The settling period is a standby time for completely stopping the tip 202a of the optical fiber 202 on the central axis AX. By providing the settling time, the tip 202a can be scanned accurately. The period corresponding to one frame is composed of one imaging period and one braking period, and the frame rate can be adjusted by adjusting the settling period. That is, the settling period can be appropriately set from the relationship between the time until the tip 202a of the optical fiber 202 completely stops and the frame rate. In order to shorten the braking period, a braking torque may be positively applied by applying a reverse phase voltage to the biaxial actuator 204C in the initial stage of the braking period.

  An objective optical system 204D is installed in front of the tip 202a of the optical fiber 202. The objective optical system 204D is composed of a plurality of optical lenses, and is held by the outer cylinder 204A via a lens frame (not shown). The lens frame is fixed and supported relative to the inner cylinder 204B inside the outer cylinder 204A. Therefore, the optical lens group held by the lens frame slides in the Z direction integrally with the inner cylinder 204B inside the outer cylinder 204A.

  A compression coil spring 204E and a shape memory alloy 204F are attached between the base end surface of the inner cylinder 204B and the inner wall surface of the outer cylinder 204A. The compression coil spring 204E is initially compressed and sandwiched in the Z direction from the natural length. The shape memory alloy 204F has a long bar shape in the Z direction, deforms when an external force is applied at room temperature, and has a property of restoring to a predetermined shape by a shape memory effect when heated to a certain temperature or higher. ing. The shape memory alloy 204F is designed such that the restoring force due to the shape memory effect is larger than the restoring force of the compression coil spring 204E. The scan driver 210 generates a drive signal corresponding to the set value designated by the sub CPU 206, and energizes and heats the shape memory alloy 204F to control the expansion / contraction amount. The shape memory alloy 204F advances and retracts the inner tube 204B in the Z direction together with the optical fiber 202 according to the amount of expansion and contraction.

  The excitation light emitted from the tip 202a of the optical fiber 202 passes through the objective optical system 204D and forms a spot on the surface or surface layer of the subject. The spot formation position is displaced in the Z-axis direction in accordance with the advance / retreat of the tip 202a, which is a point light source. That is, the confocal optical unit 204 scans the subject three-dimensionally by combining the periodic circular motion of the tip 202a on the XY approximate plane by the biaxial actuator 204C and the advance and retreat in the Z direction.

  Since the tip 202a of the optical fiber 202 is disposed at the front focal position of the objective optical system 204D, it functions as a confocal pinhole. Of the scattering component (fluorescence) of the subject excited by the excitation light, only the fluorescence from the condensing point optically conjugate with the tip 202a is incident on the tip 202a. The fluorescence is transmitted through the optical fiber 202, passes through the optical connector 152, and enters the optical demultiplexer / multiplexer 104. The optical demultiplexer / multiplexer 104 separates the incident fluorescence from the excitation light emitted from the light source 102 and guides it to the optical fiber 112. The fluorescence is transmitted through the optical fiber 112 and detected by the light receiver 114, and converted into a detection signal and amplified. The light receiver 114 may be a high-sensitivity photodetector such as a photomultiplier tube (PMT), for example, in order to detect weak light with low noise.

  The detection signal is input to the video signal processing circuit 116. The video signal processing circuit 116 operates under the control of the CPU 108 to obtain a digital detection signal by sample-holding and AD converting the detection signal at a constant rate. Here, when the position (trajectory) of the tip 202a of the optical fiber 202 during the imaging period is determined, the spot forming position in the observation region (scanning region) corresponding to the position and the return light from the spot forming position are detected. Thus, the signal acquisition timing for obtaining the digital detection signal is almost uniquely determined. In the present embodiment, the spot formation position is estimated from the signal acquisition timing in advance with reference to the actual measurement result using a calibration jig or the like, and the position on the image corresponding to the estimated position is determined. The CPU memory 110 stores a remapping table that associates the determined signal acquisition timing with the pixel position (pixel address).

  The video signal processing circuit 116 refers to the remapping table and assigns the point image represented by each digital detection signal to the pixel address according to the signal acquisition timing. Hereinafter, for convenience of explanation, the above assignment work is referred to as remapping. The video signal processing circuit 116 buffers an image signal constituted by a spatial arrangement of each point image in the image memory 118 according to the remapping result in a frame unit. The buffered signal is swept from the image memory 118 to the video signal output circuit 120 at a predetermined timing, and the video signal conforms to a predetermined standard such as NTSC (National Television System Committee) or PAL (Phase Alternating Line). To be output to the monitor 300. On the display screen of the monitor 300, a three-dimensional confocal image of a subject with high magnification and high resolution is displayed.

  By the way, in the present embodiment, the black balance is adjusted using the black level K set by the light receiver control circuit 122 when the received light is converted into a detection signal and amplified in the light receiver 114. . In the prior art, before actual observation, the black level is set based on a black image photographed in a light-shielded state and used for adjusting the black balance during observation. However, if there is a change in the characteristics of the endoscope (confocal probe) during observation, or a change in the usage environment or observation target, the preset black level is not optimal and appropriate black balance adjustment cannot be performed. . In such a case, particularly in a confocal endoscope system that performs diagnosis using a monochrome image, black may not be accurately expressed, which may prevent appropriate diagnosis. Furthermore, since cancer cells are represented in black in the observed image, it is required to accurately reproduce black for discrimination from normal cells. Therefore, in this embodiment, the photoreceiver control circuit 122 is configured to automatically set an optimal black level in real time during observation and adjust the black level based on this.

  FIG. 5 is a flowchart showing the black level setting process of the present embodiment. This process is executed by the photoreceiver control circuit 122 under the control of the CPU 108. However, in another embodiment, the CPU 108 alone may execute this process. First, in S1, it is determined whether or not the imaging period in the current frame has ended (S1). When it is determined that the imaging period has ended (S1: Yes), the gain control of the light receiver 114 is set to the auto mode (S2). Thereby, the black level is automatically adjusted in the light receiver 114 under the control of the light receiver control circuit 122.

Subsequently, the excitation light emitted from the light source 102 is turned off (S3). As a result, in the braking period after the end of the imaging period, the subject is scanned without the excitation light being emitted from the tip 202a of the optical fiber 202. Subsequently, it is determined whether or not the calculation variable K _temp is 0 (S4). K _temp is a variable indicating a provisional black level for calculating the black level K used for black balance adjustment in the light receiver 114. As will be described later, when the black level K is updated in the processing of S10 or S11, 0 is input to K _temp .

When K _temp is 0 (S4: Yes), an initial value is input to K _temp (S5). As an initial value in this case, a minimum value that can be assumed as the black level K is set in advance. On the other hand, if K _temp is not 0 (S4: No), the process of S5 is skipped and the process proceeds to S6. When the initial value is set to 0, the processes of S4 and S5 can be omitted. Subsequently, a video signal of the subject in the braking period is acquired (S6). The video signal acquired here is a black video signal acquired in a state where the excitation light is OFF. Subsequently, it is determined whether or not black data is detected in the obtained black video signal (S7).

The determination of black data detection in S7 will be described with reference to FIGS. In S7, first, five areas A1 to A5 including an arbitrary number of pixels are extracted from the black video signal acquired in S6, and the pixel level of each area is detected. FIG. 6 is a diagram illustrating five regions A1 to A5 that are extracted from the black video signal. The area extracted here is not limited to five, and an arbitrary number of areas can be extracted. Further, the location of the extracted area can be arbitrarily set. FIG. 7A shows the pixel level detected in each pixel in each region A1 to A5. FIG. 7A shows a case where each of the regions A1 to A5 includes four pixels, where the vertical axis indicates the pixel level and the horizontal axis indicates the pixel position. Subsequently, the pixel level of each region is compared with K _temp . Then, if there are two or more regions where the pixel levels of all the pixels are smaller than K _temp , it is determined that black data has been detected. Here, in the case of FIG. 7A, it is determined that no black data is detected because the pixel level of all the pixels is higher than K _temp in any region.

When it is determined that black data is not detected (S7: No), it is determined whether K _temp is equal to or greater than the maximum value K _max (S8). Here, it is determined whether or not the calculation variable K _temp has reached a preset maximum value K _max . If it is determined that K _temp has not reached K _max (S8: No), K _temp is increased by an arbitrary value (S9). Subsequently, it is determined whether or not to end the observation (S13). If the observation is not ended (S13: No), the excitation light emitted from the light source 102 is turned on (S14). Then, in the imaging period of the next frame, a process of acquiring a confocal image in a state where excitation light is emitted from the tip of the optical fiber 102 is performed (S15), and the process returns to S1. In this case, the black level K is not changed, and the light receiver 114 adjusts the black balance using the black level K used in the previous frame. Then, after the imaging period in this frame ends (S1: Yes), the processes after S2 are repeated.

At this time, in S7, as shown in FIG. 7B, the K _temp increased by an arbitrary number is compared with the pixel level of each pixel in the areas A1 to A5 to determine whether black data is detected. Is judged. Thereafter, until the black data is detected in S7, K _temp is increased by an arbitrary value and compared with the pixel level of the black video signal acquired during the braking period. If K _temp becomes equal to or higher than K _max without detecting black data (S8: Yes), an arbitrarily set black level value K _op is set as the black level K (S10). In subsequent S12, 0 is input to K _temp and the process proceeds to the subsequent processes. Thereby, in the next frame, the black balance is adjusted based on the new black level K, and this process is resumed in a state where K _temp is returned to 0. As described above, when the black level K is set, the calculation variable K _temp is returned to 0 and compared with the black image, so that the environment is shifted to another observation site during observation. Even if it changes, the black level corresponding to the change can be set without depending on the black level in the previous frame.

On the other hand, as shown in FIG. 7C, as a result of comparing the K _temp increased by an arbitrary number with the pixel level of each pixel in the areas A1 to A5, the pixel levels of all the pixels are smaller than K _temp. If there are two or more areas (areas A1 and A2 shown in FIG. 7C), it is determined that black data has been detected (S7: Yes). Then, the value of K _temp at this time is set as the black level K (S11). In subsequent S12, 0 is input to K _temp and the process proceeds to the subsequent processes. As a result, in the next frame, the light receiver 114 adjusts the black balance based on the changed black level K, and the present processing using K _temp returned to 0 is resumed.

  As described above, in the endoscope system according to the present embodiment, when the black environment K is automatically set based on the black image acquired during observation, the usage environment, the usage time, and the photographing target change. However, an appropriate black level K can be set in real time. In the present embodiment, a black image is acquired using the braking period in the frame, so that a special shading device is used to set the black level, or observation is interrupted for setting. There is no need.

  The above is the description of the embodiment of the present invention. The present invention is not limited to the above-described configuration, and various modifications can be made within the scope of the technical idea of the present invention. First, in the above embodiment, the case where the present invention is applied to a scanning confocal endoscope system has been described. However, the present invention is not limited to this, and the present invention can also be applied to other endoscope systems. is there. For example, when applied to an endoscope system using an endoscope having a solid-state imaging device at the tip, a frame obtained by adjusting the frame rate and irradiating the subject with illumination light during observation, and illumination It is configured to repeat alternately (or periodically) frames that are acquired without irradiating light, and based on the image (black image) of the frames that are acquired without irradiating illumination light, the same as in the above embodiment, black The level can be automatically set.

In the above embodiment, the black level setting process is performed for each frame during observation. However, the black level setting process is terminated when the black level K is once set during observation. When there is an instruction from the user, the black level setting process may be executed for the frame at that time. Further, the detection of black data in the black level setting process is not limited to the method in the above embodiment, and various known methods can be used. For example, in the above-described embodiment, a region including an arbitrary number of pixels is extracted from the acquired black video signal, and the pixel level of each region is compared with K _temp. comparing the pixel level and K _temp, or it is also possible to compare the mean and K _temp pixel levels for all pixels.

1 Scanning Confocal Endoscope System 100 System Main Body 102 Light Source 104 Optical Demultiplexer / Multiplexer 106 Damper 108 CPU
110 CPU memory 112 Optical fiber 114 Light receiver 116 Video signal processing circuit 118 Image memory 120 Video signal output circuit 122 Light receiver control circuit 200 Confocal probe 202 Optical fiber 204 Confocal optical unit 206 Sub CPU
208 Sub memory 210 Scan driver

Claims (8)

Image acquisition means for acquiring an image of the subject;
Black balance adjusting means for adjusting black balance for the image acquired by the image acquiring means;
Black level setting means for setting a black level used for black balance adjustment in the black balance adjusting means;
With
The image acquisition means includes
During observation of the subject, a first image in a state where the subject is irradiated with light and a second image in a state where the illumination light is not irradiated are acquired,
The black level setting means includes
Variable means to gradually increase the provisional black level
With
Comparing the pixel level of at least some of the pixels in the second image with the provisional black level, and setting the provisional black level as a black level when the pixel level is smaller than the provisional black level ;
Endoscope system. The black level setting means includes
After setting the black level, the provisional black level is returned to the initial value .
The endoscope system according to claim 1 . Image acquisition means for acquiring an image of the subject;
Black balance adjusting means for adjusting black balance for the image acquired by the image acquiring means;
Black level setting means for setting a black level used for black balance adjustment in the black balance adjusting means;
With
The image acquisition means includes
During observation of the subject, a first image in a state where the subject is irradiated with light and a second image in a state where the illumination light is not irradiated are acquired,
The black level setting means includes
In response to an instruction from the user , a black level is set based on the second image .
Endoscope system. An endoscope system that is a confocal endoscope system,
Image acquisition means for acquiring an image of the subject;
Black balance adjusting means for adjusting black balance for the image acquired by the image acquiring means;
Black level setting means for setting a black level used for black balance adjustment in the black balance adjusting means;
With
The image acquisition means includes
During observation of the subject, a first image in a state where the subject is irradiated with light and a second image in a state where the illumination light is not irradiated are acquired,
The black level setting means includes
Setting a black level based on the second image ;
Endoscope system. The endoscope system includes:
A light source for supplying light to the subject,
The image acquisition means includes
An optical fiber that guides light from the light source incident on the incident end to the exit end, and exits the exit end to the subject;
Light that drives the emission end of the optical fiber so that the light emitted from the emission end of the optical fiber scans the subject during the imaging period and returns to the initial position during the braking period. Fiber scanning means;
With
The second image is acquired during the braking period ;
The endoscope system according to any one of claims 1 to 4 . The black level setting means includes
Set the black level for all the second images acquired during observation .
The endoscope system according to any one of claims 1, 2, 4, and 5 . Black balance adjusting means for adjusting black balance for the image of the subject acquired by the image acquiring means;
Black level setting means for setting a black level used for black balance adjustment in the black balance adjusting means;
With
The black level setting means includes
Variable means to gradually increase the provisional black level
With
The provisional black level is compared with the provisional black level of at least some of the pixels in the image in which the object is not irradiated with light obtained by the image obtaining unit during observation of the subject, and the provisional pixel level is the provisional black level. When the black level is smaller, the provisional black level is set as the black level .
Endoscopy processor. Black balance adjusting means for adjusting black balance for the image of the subject acquired by the image acquiring means;
Black level setting means for setting a black level used for black balance adjustment in the black balance adjusting means;
With
The black level setting means includes
In response to an instruction from a user, during observation of the subject, a black level is set based on an image in a state where light is not emitted to the subject acquired by the image acquisition unit .
Endoscopy processor.

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