JP2018007880A - Endoscope apparatus and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of hunting and halation as much as possible.SOLUTION: An endoscope apparatus includes: an insertion section, a hunting detection section, a halation detection section, and an imaging control section. The insertion section includes an imaging part at a distal end. The hunting detection section detects a hunting state on the basis of luminance of an image from the imaging part. The halation detection section detects a halation state of the image. The imaging control section controls the luminance on the basis of the hunting state and the halation state. A control method of an endoscope apparatus can be also implemented as one embodiment.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an endoscope apparatus and a control method.

  Conventionally, an endoscope apparatus provided with an elongated insertion portion has been used in the medical field. The insertion unit may be provided with illumination and an imaging unit at the tip, and the treatment instrument channel may be inserted therethrough. When the imaging unit is inserted into the body cavity, for example, it is used for observation of a subject such as an internal organ. Various treatment tools are inserted into the treatment tool channel and used for various therapeutic treatments. Also in the industrial field, the endoscope apparatus is used for observation, inspection, and the like of damage, corrosion, and the like inside boilers, turbines, engines, chemical plants, and other structures. Such an endoscope apparatus generally has various objects such as observation. Therefore, there is an endoscope apparatus equipped with an automatic exposure control mechanism that controls the brightness of the screen according to the observation conditions.

  The AE control includes feedback control that determines the brightness control parameter by feeding back the difference between the brightness of the captured image and the target brightness. An example of the control parameter is a shutter speed. The shutter speed corresponds to the reciprocal of the exposure time. The control parameter may further include a gain. The gain is an amplification factor multiplied by the signal level for each pixel. If AE control is performed during imaging, hunting may occur without the control parameters converging. Hunting means an oscillation phenomenon of brightness. When hunting occurs, the brightness of the photographed image is not set to an appropriate brightness, which may hinder observation. As an endoscope apparatus for preventing such a situation, Patent Document 1 discloses an electronic endoscope apparatus that stops AE control when hunting is detected.

JP 2002-325729 A

  However, if AE control is completely stopped, halation tends to occur more frequently. The halation is a phenomenon in which the signal value is limited to the maximum value because the luminance detected for each pixel exceeds a predetermined maximum value that can be expressed as a signal value. Halation is also called whitening. When halation occurs, the user cannot observe the subject and cannot perform a desired operation. In particular, halation frequently occurs when an object is inserted into a metal object having a high light reflectance such as an aircraft engine during image observation.

  The present invention has been made based on the above problems, and an object of the present invention is to provide an endoscope apparatus and a control method that can suppress the occurrence of hunting and halation as much as possible.

  One aspect of the present invention includes an insertion unit including an imaging unit at a tip, a hunting detection unit that detects a hunting state based on luminance of an image from the imaging unit, and a halation detection unit that detects a halation state of the image. An imaging control unit that controls the luminance based on the hunting state and the halation state.

  According to the present invention, generation of hunting and halation can be suppressed as much as possible.

It is a block diagram which shows the structural example of the endoscope apparatus which concerns on this embodiment. It is a figure which shows an example of the detection method of hunting concerning this embodiment. It is a figure which shows an example of the detection method of the halation which concerns on this embodiment. It is a figure which shows the example of control of the exposure time which concerns on this embodiment. It is a figure which shows an example of AE control which concerns on this embodiment. It is a figure which shows the other example of AE control which concerns on this embodiment.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration example of an endoscope apparatus 1 according to the present embodiment.
The endoscope apparatus 1 according to the present embodiment includes an insertion portion 10 and a main body portion 11. The insertion unit 10 is inserted into the subject and acquires at least an image inside the subject. The type of subject is not particularly limited. The subject may be an industrial device such as an engine, a turbine, or a boiler, or may be a living body. The insertion portion 10 is bendable and has an elongated tubular shape. The length of the insertion part 10 is 1-30 m, for example.

  The insertion portion 10 has a CCD (Charge Coupled Device) imaging element 104, an objective lens 105, an LED (Light Emitting Diode) 106, a thermistor 107, an acceleration sensor 108, and a wire fixing portion 109 at the distal end thereof. And a wire connecting part 124 and a detachable connector 134. In the longitudinal direction of the insertion portion 10, four bending wires 126 are inserted.

  The CCD image sensor 104 photoelectrically converts light from the subject. A light receiving element is arranged for each pixel on the image pickup surface of the CCD image pickup element 104, and each light receiving element generates a voltage according to the intensity of the incoming light. The CCD image pickup device 104 generates an image pickup signal indicating a signal value for each pixel from a voltage value obtained by photoelectric conversion based on a timing indicated by a drive signal input from the main body unit 11. The CCD imaging device 104 outputs the generated imaging signal to the main body unit 11.

  The objective lens 105 converges the light incident on the distal end portion of the insertion unit 10 and forms an image of the subject on the imaging surface of the CCD image sensor. The objective lens 105 is disposed to face a light receiving window (not shown) at the tip.

  The LED 106 is a light source that emits light based on the driving power supplied from the main body 11. The LED 106 irradiates the subject with the emitted light.

  The thermistor 107 is a temperature sensor that detects the temperature at the distal end portion of the insertion portion 10. The thermistor 107 generates a thermistor signal indicating the detected temperature, and outputs the generated thermistor signal to the main body 11.

  The acceleration sensor 108 detects the acceleration at the distal end portion of the insertion portion 10. The acceleration sensor 108 is, for example, a triaxial acceleration sensor. The three-axis acceleration sensor detects respective accelerations in three directions orthogonal to each other in a three-dimensional space. The acceleration sensor 108 outputs an acceleration signal indicating the detected acceleration to the main body 11.

  The wire fixing portion 109 is installed at the distal end portion of the insertion portion 10. The distal ends of the four bending wires 126 are connected to the wire fixing portion 109 so that they can be alternately tilted in two axial directions orthogonal to the longitudinal direction of the insertion portion 10. The directions of the two axes are orthogonal to each other. The biaxial directions include a UD (Up-Down) direction and an RL (Right-Left) direction. The UD direction and the RL direction correspond to the vertical direction and horizontal direction of the pixels arranged on the imaging surface. Each of the two bending wires relating to the bending in the UD and RL directions is referred to as a UD and RL wire, respectively.

  The wire connecting portion 124 is installed at the proximal end portion of the insertion portion 10. The wire connecting portion 124 pulls each bending wire 126 in the longitudinal direction of the insertion portion 10 in accordance with the pulling by the wire connecting portion 125 when the wire connecting portion 124 is connected to the wire connecting portion 125 included in the main body portion 11.

  The detachable connector 134 is installed at the proximal end portion of the insertion portion 10. The detachable connector 134 includes a mechanism that is detachable from the detachable connector 135 included in the main body 11. The detachable connector 134 has a shape that fits with the detachable connector 135, for example.

  The insertion unit 10 is inserted with connection cables that transmit the imaging control signal, the imaging signal, the driving power, the thermistor signal, and the acceleration signal. These connection cables are electrically connected to the components of the transmission source and the transmission destination when the detachable connector 134 is attached to the detachable connector 135 of the main body 11. These connection cables are, for example, composite coaxial lines. The detachable connectors 134 and 135 include contacts that are electrically connected to the base ends of the connection cables.

  The main body portion 11 includes a wire connecting portion 125 and a detachable connector 135 at an end portion that can come into contact with the proximal end portion of the insertion portion 10. The main body 11 includes a system control unit 110, a user interface unit 111, a storage medium 112, a parameter storage unit 113, a timing generator 114, a CCD drive circuit 115, an LCD (Liquid Crystal Display) 118, an LED drive circuit 119, a curve The controller 121 includes a UD bending motor 122, an RL bending motor 123, a preamplifier 136, an AFE (Analog Front End) 137, and an image processing unit 140.

  The system control unit 110 is a component that performs overall operation control of the endoscope apparatus 1. The system control unit 110 is connected to the user interface unit 111, the storage medium 112, the parameter storage unit 113, the CCD drive circuit 115, the LCD 118, the LED drive circuit 119, the bending control unit 121, the contacts of the detachable connector 135 and the image processing unit 140. Has been. The system control unit 110 controls the operation of each component of the endoscope apparatus 1 based on the operation signal input from the user interface unit 111, various parameters stored in the parameter storage unit 113, and the like. The system control unit 110 includes, for example, lighting / extinguishing control of the LED 106, imaging operation control of the CCD image sensor 104, bending control of the bending control unit 121, temperature detection control, and the like. In the temperature detection control, the system control unit 110 causes the LCD 118 to display information indicating the current temperature indicated by the thermistor signal input from the thermistor 107 via the LCD controller 110b. Further, the system control unit 110 determines whether the current temperature is within a predetermined range from the upper limit or the lower limit, based on the upper limit or the lower limit of the allowable temperature stored in the parameter storage unit 113 in advance, or higher or lower than the upper limit. If lower, a predetermined warning message is displayed on the LCD 118. The system control unit 110 includes an image recording unit 110a and an LCD controller 110b.

  The image recording unit 110 a stores the image signal input from the image processing unit 140 in the storage medium 112 based on the control signal input from the user interface unit 111. For example, the image recording unit 110a stores in the storage medium 112 image signals from the start of recording to the end of recording indicated by the control signal.

  The LCD controller 110 b outputs an image signal input from the image processing unit 140 via the image recording unit 110 a to the LCD 118 based on the control signal input from the user interface unit 111. Thereby, the LCD 118 can display various moving images and still images acquired by the image processing unit 140. When displaying a still image, the LCD controller 110b continuously outputs an image signal of a frame acquired at that time to the LCD 118. The image recording unit 110a may record an image signal acquired as a still image in the storage medium 112. In addition, the LCD controller 110b outputs image signals indicating various display information to the LCD 118. The display information includes, for example, a guidance screen for information necessary for operation input.

  The user interface unit 111 includes an operation unit. The operation unit accepts an operation input by a user. The operation unit is, for example, a member such as a joystick, an operation switch, or an operation button. The user interface unit 111 generates a control signal corresponding to the received operation input, and outputs the generated control signal to the system control unit 110.

  The storage medium 112 is a storage medium that stores image signals. In the storage medium 112, for example, an image signal indicating an image such as a moving image or a still image obtained by the image processing unit 140 is stored.

  The parameter storage unit 113 is changed by a user operation such as an operation input to the user interface unit 111, an image processing parameter used for various image processing executed by the image processing unit 140, and a bending control parameter related to bending control by the bending control unit 121. Various parameters to be stored are stored. Further, the parameter storage unit 113 stores the relationship between the transmission path length of the non-imaging signal and the drive processing parameters of the CCD drive circuit 115, and the like.

  The timing generator 114 generates a timing signal for driving the CCD image sensor based on the imaging control signal input from the system control unit 110. The imaging control signal includes information such as the exposure time notified from the image processing unit 140. The exposure time is the time from the start of exposure to the end of exposure at each pixel, and corresponds to the reciprocal of the shutter speed. Therefore, the longer the exposure time, the higher the signal level obtained by one reading. The exposure time is used as a control parameter for controlling the brightness of the captured image. Here, the longer the exposure time, the higher the luminance, and the shorter the exposure time, the lower the luminance. The timing generator 114 outputs the generated timing signal to the CCD drive circuit 115.

  The CCD drive circuit 115 generates a drive signal based on the timing signal input from the timing generator 114 and the control signal from the system control unit 110. A control signal from the system control unit 110 is a signal indicating imaging operation control. As the imaging operation control, an instruction to start imaging, stop imaging, zoom, brightness adjustment, and the like is instructed. The CCD drive circuit 115 outputs the generated drive signal to the CCD image sensor 104. The drive signal instructs the frame rate, the order of pixels from which signal levels are acquired in each frame, the exposure start and the exposure end for each pixel.

  The LCD 118 is an image display unit that displays an image based on an image signal input from the system control unit 110.

  The LED drive circuit 119 performs lighting / extinguishing control of the LED 106 based on a control signal input from the system control unit 110. The LED drive circuit 119 starts supplying drive power to the LED 106 when instructed to turn on, and stops supplying drive power when instructed to turn off.

  The bending control unit 121 drives one or both of the UD bending motor 122 and the RL bending motor 123 based on a control signal input from the system control unit 110. The control signal indicates, for example, a bending amount for each bending direction corresponding to each of the operation amounts in two directions detected by the user interface unit 111. The bending direction corresponds to the above-described UD direction and RL direction. The bending control unit 121 instructs the UD bending motor 122 and the RL bending motor 123 with a driving amount corresponding to the bending amount in the UD direction indicated by the control signal and a driving amount corresponding to the bending amount in the RL direction.

The UD bending motor 122 and the RL bending motor 123 respectively pull the UD wire and the RL wire with the driving amounts instructed by the bending control unit 121 by the respective rotations.
When the detachable connector 135 is attached to the detachable connector 134 of the insertion unit 10, the wire connection unit 125 connects the UD wire and the RL wire connected to the wire connection unit 124 of the insertion unit 10. The UD wire and the RL wire are pulled by the UD bending motor 122 and the RL bending motor 123. Thereby, the front-end | tip part of the insertion part 10 curves according to a user's operation.

  The detachable connector 135 is installed at a position where it comes into contact with the proximal end portion of the insertion portion 10. The detachable connector 135 includes a mechanism that is detachable from the detachable connector 134 of the insertion unit 10. The detachable connector 135 has a shape that fits with the detachable connector 134, for example.

  The preamplifier 136 amplifies the image signal input from the CCD image sensor 104 and outputs the amplified image signal to the AFE 137. This amplification is performed to compensate for the signal level attenuated by transmission.

  The AFE 137 performs CDS (Correlated Double Sampling) processing, AGC (Automatic Gain Control) processing, and AD (Analog-to-Digital) analog processing on analog imaging signals input from the preamplifier. / Digital) conversion processing is performed to generate a digital imaging signal. The AFE 137 outputs the generated digital imaging signal to the image processing unit 140.

  The image processing unit 140 includes a black correction unit 142, a pixel interpolation / luminance color difference conversion unit 143, a correction processing unit 144, a hunting detection unit 145, a halation detection unit 146, and an imaging control unit 147.

  The black correction unit 142 calculates a corrected signal level by subtracting the black level from the signal level for each pixel indicated by the input imaging signal. The black correction unit 142 may use, as the black level, for example, a signal level during the extinguishing period of the LED 106, a minimum value between pixels of each frame or a signal level within a predetermined period, and the like. The black correction unit 142 outputs an imaging signal indicating the corrected signal level for each pixel to the pixel interpolation / luminance color difference conversion unit 143.

  The pixel interpolation / luminance color difference conversion unit 143 performs pixel interpolation processing on the imaging signal input from the black correction unit 142. The input imaging signal has a signal level of any color component of red (R), green (G), and blue (B) for each pixel. Pixels related to red, green, and blue are periodically arranged in a two-dimensional space. This arrangement is, for example, a Bayer arrangement. Hereinafter, a group of pixels related to each color component of one cycle is referred to as a pixel cycle. In the pixel interpolation process, the pixel interpolation / luminance color difference conversion unit 143 is arranged within a predetermined range from the target pixel for each target pixel, and interpolates the signal level for each pixel related to the same color component as the target pixel. The signal level of the target pixel is calculated. The target pixel is a pixel to be processed at that time. Each pixel in the frame is treated as a target pixel. In the interpolation, for example, a method such as bilinear interpolation or bicubic interpolation can be used.

  The pixel interpolation / luminance / chrominance conversion unit 143 performs color space conversion on the signal level of each pixel for each color component obtained by interpolation, so that the luminance level (Y) for each pixel period and two color difference levels (Cr), ( Cb) is calculated. That is, the pixel interpolation / luminance color difference conversion unit 143 converts the RGB value represented by the RGB color system into the YCrCb value represented by the YCrCb color system in the color space conversion. In color space conversion, for example, ITU-R BT. A conversion formula defined in 601 can be used. The color difference levels (Cr) and (Cb) indicate the hue and saturation of red and blue colors, respectively. The pixel interpolation / luminance color difference conversion unit 143 outputs a luminance signal indicating the luminance level for each pixel cycle to the correction processing unit 144, the hunting detection unit 145, the halation detection unit 146, and the imaging control unit 147. The pixel interpolation / luminance color difference conversion unit 143 outputs a color difference signal indicating two color difference levels (Cr) and (Cb) for each pixel period to the correction processing unit 144.

  The correction processing unit 144 performs various correction processes for each of the luminance signal and the two color difference signals input from the pixel interpolation / luminance color difference conversion unit 143. The correction processing includes, for example, aberration correction and noise reduction processing. The correction processing unit 144 performs color space conversion on each of the luminance signal and the two color difference signals obtained by the correction process, and generates an image signal indicating the signal level for each pixel after correction. That is, the correction processing unit 144 converts the YCrCb value expressed in the YCrCb color system into the RGB value expressed in the RGB color system in the color space conversion. This color space conversion process corresponds to the inverse conversion of the color space conversion in the pixel interpolation / luminance color difference conversion unit 143. The correction processing unit 144 outputs the generated image signal to the system control unit 110.

  The hunting detection unit 145 detects the hunting state based on the luminance signal input from the pixel interpolation / luminance color difference conversion unit 143. The hunting detection unit 145 analyzes the luminance variation based on the luminance signal, generates hunting state information indicating the presence / absence of hunting as a hunting state, and the hunting strength when the hunting occurs, and the generated hunting state information Is output to the imaging control unit 147. An example of detecting hunting and hunting strength will be described later.

  The halation detection unit 146 detects the halation state based on the luminance signal input from the pixel interpolation / luminance color difference conversion unit 143. Here, the halation detection unit 146 determines the presence / absence of halation based on the luminance for each block which is a partial region in the frame based on the luminance signal. The halation detection unit 146 generates, as the halation state, halation state information indicating the presence / absence of halation detection and the halation intensity when it is detected. The halation detection unit 146 outputs the halation state information to the imaging control unit 147.

  The imaging control unit 147 receives a luminance signal from the pixel interpolation / luminance color difference conversion unit 143, hunting state information from the hunting detection unit 145, and halation detection information from the halation detection unit 146. The imaging control unit 147 controls the luminance level indicated by the luminance signal input based on the hunting state information and the halation detection information. In the brightness level control, the imaging control unit 147 performs, for example, AE control.

  In the AE control, when hunting and halation are not detected, the imaging control unit 147 sets the exposure time so that the absolute value of the luminance difference, which is the difference between the target luminance and the predetermined target luminance as the target amount, becomes small. Determine. The imaging control unit 147 calculates, for example, an average value of luminance levels within a predetermined period (for example, 1 to 3 seconds) up to that point (current) as the representative luminance. As the predetermined target luminance, for example, target luminance stored in advance in the parameter storage unit 113 may be used, or target luminance instructed by a user operation input may be used. The imaging control unit 147 notifies the timing generator 114 of the determined exposure time. As a result, the determined exposure time is used for capturing an image by the CCD image sensor 104. On the other hand, the imaging control unit 147 makes the exposure time control speed lower when detecting hunting than when hunting is not detected. In addition, when the imaging control unit 147 detects halation while detecting hunting, only the hunting, that is, the exposure time control speed when no halation is detected while detecting hunting is set. Compared with this, the control speed of the exposure time is increased. An example of AE control based on the exposure time will be described later.

(Example of hunting detection)
Next, a detection example of hunting and hunting strength according to the present embodiment will be described.
For example, the hunting detection unit 145 performs Fourier transform for each predetermined period up to that point (current) with respect to the average value or integrated value (sum) of the luminance levels indicated by the luminance signal of each frame for each predetermined period. Calculate the intensity of each. The predetermined period is, for example, 1 to 3 seconds. As shown in FIG. 2, when there is a frequency fr whose intensity is _{equal to} or greater than a predetermined intensity threshold Ith, the hunting detection unit 145 determines that hunting has been detected. This determination condition indicates that the fluctuation of the main component of luminance has periodicity of the frequency fr. And the hunting detection part 145 determines this intensity | strength as hunting intensity | strength. The hunting intensity is an index indicating the degree of periodicity of the luminance variation of the captured image. When there is no frequency fr at which the intensity is _{equal to} or greater than the predetermined intensity threshold Ith, the hunting detection unit 145 determines that hunting has not been detected. The threshold value of the hunting intensity is, for example, 0.3 to 0.6 times the total power between frequencies within a predetermined period. In the following description, the frequency fr related to detection of hunting may be referred to as hunting frequency.

(Example of detecting halation)
Next, an example of detecting halation and halation intensity according to this embodiment will be described. For example, the halation detection unit 146 calculates an integrated value of the luminance level for each block Bk with respect to the luminance level for each pixel period indicated by the luminance signal. The block Bk is a partial area of the image Im of each frame and includes a plurality of pixel periods. As for the size of the block Bk, for example, the number of pixels in the horizontal direction and the vertical direction is 9 × 9 to 24 × 24. It is determined that halation is detected in block Bk. The halation detection unit 146 determines that no halation is detected in the block Bk where the calculated integrated value does not exceed the predetermined integrated value threshold. The threshold value of the predetermined integrated value is, for example, 0.6 to 0.9 times the value obtained by multiplying the pixel period included in one block by the upper limit of the luminance value. The upper limit of the luminance value means the maximum luminance value that can be expressed under a predetermined number of bits. When the luminance value for each pixel period is represented by 10 bits, the upper limit of the luminance value is 1023 (= 2 ¹⁰ −1). As indicated by the dashed arrows in FIG. 3, the halation detection unit 146 sequentially changes the blocks Bk to be detected as halation in a predetermined order (for example, raster scan order), and detects halation over the entire frame. Determine presence or absence. The halation detection unit 146 determines the size of the area where halation is detected for each frame as the halation intensity. This size is represented by, for example, the number of blocks in which halation is detected, the number of pixel units in those blocks, and the like.

(Example of AE control)
Next, AE control will be described using an example in which exposure time is used as a control parameter. When determining the exposure time, the imaging control unit 147 performs, for example, proportional control (Proportional Control, P control). In P control, the imaging control unit 147 calculates a change amount in exposure time for each frame by multiplying a luminance difference that is a difference between the control amount and the target amount by a predetermined proportional gain. The proportional gain is a control parameter for the control speed. The larger the proportional gain, the higher the control speed, and the smaller the proportional gain, the lower the control speed. The imaging control unit 147 adds the calculated change amount to the original exposure time and updates the exposure time. In the following description, the proportional gain used when hunting and halation are not detected is referred to as a reference gain.

  The imaging control unit 147 makes the exposure time control speed lower when detecting hunting than when hunting and halation are not detected. Further, when the imaging control unit 147 detects halation while detecting hunting, only the hunting, that is, the exposure speed compared to the control speed of the exposure time when no halation is detected while detecting hunting is detected. Increase time control speed. Therefore, the imaging control unit 147 uses a constant value smaller than the reference gain as a proportional gain when detecting hunting or detecting halation. The proportional gain is, for example, 0 to 0.5 times the reference gain.

  In addition, the imaging control unit 147 may decrease the proportional gain as the hunting strength increases. In this case, the higher the hunting strength, the lower the exposure speed control speed. The imaging control unit 147 may decrease the proportional gain as the halation intensity increases. In this case, the higher the halation intensity, the lower the exposure speed control speed. When the halation intensity is higher than a predetermined halation intensity threshold, or when the hunting intensity is higher than a predetermined hunting intensity threshold, the imaging control unit 147 may set the proportional gain to zero. In this case, the exposure time does not change and becomes a constant value.

More specifically, the imaging control unit 147 calculates an evaluation value by adding the normalized hunting intensity and the normalized halation intensity. In normalization, the imaging control unit 147 scales the hunting intensity and the halation intensity so as to take values within a predetermined range based on an upper limit value and a lower limit value that can be taken by the hunting intensity and the halation intensity, respectively. FIG. 4 is a diagram illustrating an example of the relationship between the evaluation value and the proportional gain. A thick solid line indicates an evaluation value calculated when the imaging control unit 147 detects only hunting. A one-dot broken line indicates an evaluation value calculated when the imaging control unit 147 detects halation while detecting hunting. As shown in FIG. 4, in both cases where only hunting is detected and when halation is detected while hunting is being detected, the imaging control unit 147 increases the proportional gain as the calculated evaluation value increases. Make it smaller. However, when the evaluation value when only halation is detected is the same as the evaluation value when halation is detected while hunting is detected, the imaging control unit 147 increases the latter proportional gain. . Specifically, as shown in FIG. 4, when the evaluation value in a case of detecting halation is equal to both S _n while detecting the evaluation value and the hunting in the case that detecting only halation, hunting proportional gain K ₁ calculated if you detect only _smaller than the proportional gain K ₂ is calculated when detecting the hunting and halation (K 1 _{<K 2).} The evaluation value S _n is smaller than the predetermined first threshold value S _{1 and} larger than the predetermined zeroth threshold value S ₀ (S ₀ <S _n <S ₁ ). However, if the evaluation value in a case that detects only halation is the first threshold value S ₁ or more, the imaging control unit 147 defines a proportional gain to zero. Similarly, when the evaluation value in the case of detecting halation becomes the second threshold value S ₂ or more predetermined in while detecting the hunting, the imaging control unit 147 defines a proportional gain to zero. The second threshold value S ₂ is a real number larger than the first threshold value S ₁ (S ₂ > S ₁ ). When the evaluation value in the case of detecting hunting or the evaluation value in the case of detecting halation while detecting hunting is smaller than the 0th threshold value S ₀ , the imaging control unit 147 performs proportional gain. the determined as a reference gain _{K 0.} This is because when the evaluation value is equal to or less than the 0th threshold value S ₀ , this corresponds to the fact that neither hunting nor halation is detected. That is, the evaluation value being equal to the 0th threshold value S ₀ indicates that the hunting strength is equal to the hunting strength threshold value used for detecting hunting.

  Note that the imaging control unit 147 may calculate the evaluation value by weighting and adding the hunting intensity and the halation intensity, and use the evaluation value for determining the proportional gain. Specifically, the imaging control unit 147 calculates, as an evaluation value, the sum of multiplication values obtained by multiplying the normalized hunting intensity and the normalized halation intensity by different weighting factors set in advance. Thereby, the degree of emphasizing hunting and halation is set as a cause that hinders observation of the captured image.

  The imaging control unit 147 may stop the AE control when the hunting frequency is a frequency within a predetermined range. When stopping the AE control, the imaging control unit 147 sets the proportional gain to zero. As a frequency within a predetermined range, a user-specified frequency indicated by a control signal input from the user interface unit 111 may be used. More specifically, control is performed according to the procedure shown in FIG.

FIG. 5 is a flowchart showing an example of AE control according to the present embodiment.
(Step S <b> 101) The system control unit 110 sets a user-specified frequency indicated by a control signal input from the user interface unit 111 in the imaging control unit 147. Thereafter, the process proceeds to step S102.
(Step S102) The imaging control unit 147 starts AE control when the control signal from the system control unit 110 indicates the start of imaging. Thereafter, the process proceeds to step S103.

(Step S103) The hunting detection unit 145 determines whether hunting is detected based on the luminance signal of each frame. When it determines with having detected (step S103 YES), it progresses to the process of step S104. When it determines with not detecting (step S103 NO), it progresses to the process of step S106.
(Step S104) The imaging control unit 147 determines whether or not the hunting frequency is within the set user-specified frequency range. When it is determined that the frequency is within the user-specified frequency range (YES in step S104), the process proceeds to step S105. When it is determined that the frequency is outside the range of the user designated frequency (NO in step S104), the process proceeds to step S106.

(Step S105) The imaging control unit 147 stops the AE control. Specifically, the imaging control unit determines that the proportional gain is zero. Thereafter, the process proceeds to step S103.
(Step S106) The imaging control unit 147 performs AE control normally. Specifically, the imaging control unit defines a reference gain K ₀ as a proportional gain. Thereafter, the process proceeds to step S103. The processes shown in steps S103 to S106 are repeated until a control signal indicating stop of imaging is input from the system control unit 110.

  Thereby, even when the luminance of the subject periodically varies depending on the specific conditions, hunting due to the variation can be suppressed. For example, in inspection of an aircraft engine, a turning tool may be used to rotate turbine blades arranged radially from the main shaft about the main shaft at a constant rotational speed. At this time, the brightness of the image of the turbine blade to be imaged varies at a constant frequency as it rotates. In addition, the luminance fluctuation itself may be an inspection target. A range of such a variation frequency is set in advance as a user-specified frequency, and hunting that hinders the inspection is suppressed by stopping the AE control with respect to the variation in luminance at the frequency within the range. As such a frequency, for example, it is also applied to a frequency of luminance variation of a light source such as a fluorescent lamp.

The imaging control unit 147 may further perform AE control based on the acceleration signal input from the acceleration sensor 108 via the system control unit 110. This acceleration signal indicates the acceleration of movement at the distal end of the insertion portion 10. For example, when hunting is detected, the imaging control unit 147 determines whether or not the distal end portion of the insertion unit 10 is stationary based on the acceleration signal. The imaging control unit 147 can determine whether or not the distal end is in a stationary state based on, for example, whether or not the absolute value of the acceleration indicated by the acceleration signal is equal to or less than a predetermined acceleration threshold. When the imaging control unit 147 determines that the tip portion is operating, the imaging control unit 147 sets the control speed to be lower than the normal control speed without completely stopping the AE control. Here, the imaging control unit 147 sets the proportional gain to a predetermined value that is larger than ₀ and smaller than the reference gain K ₀ . In such a case, the endoscope may be generated in the middle of the insertion operation into the subject, but this is because the observation of the image is required and is temporary. When the imaging control unit 147 determines that the tip portion is not operating, the imaging control unit 147 sets the control speed to a normal control speed similar to that when no hunting or halation is detected. More specifically, control is performed according to the procedure shown in FIG.

  FIG. 6 is a flowchart showing another example of AE control according to the present embodiment. The process illustrated in FIG. 6 includes the processes of steps S111 to S118. Since the process of step S111-S116 is the same as the process of step S101-S106 shown in FIG. 5, the description is abbreviate | omitted. The process of step S117 shown in FIG. 6 is started after it is determined in step S113 that the hunting detection unit 145 has detected hunting.

(Step S117) The imaging control unit 147 determines whether or not the distal end portion of the insertion unit 10 is stationary based on the acceleration signal. When it is determined that the camera is stationary (YES in step S117), the process proceeds to step S114. When it is determined that it is not stationary, that is, it is operating (NO in step S117), the process proceeds to step S118.
(Step S118) The imaging control unit 147 makes the control speed lower than the normal control speed (low speed control). The imaging control unit 147 sets the proportional gain to a predetermined value that is larger than ₀ and smaller than the reference gain K ₀ . Thereafter, the process proceeds to step S113.

Note that the imaging control unit 147 may determine the proportional gain so that the larger the absolute value of the acceleration indicated by the acceleration signal in the process of step S118 in FIG. However, the value range of the proportional gain that is determined is 0 or more and the reference gain K ₀ or less.

  5 and 6, after determining that the hunting frequency is outside the range of the user-specified frequency (NO in steps S104 and S114), the imaging control unit 147 determines the hunting intensity and the halation intensity as described above. The evaluation value may be calculated based on the above. Thereafter, in steps S106 and S116, the imaging control unit 147 may determine the control speed based on the evaluation value calculated as described with reference to FIG.

In the above-described embodiment, the case where the exposure time is mainly controlled as the brightness control of the image is described as an example. However, the present invention is not limited to this. For example, the frame rate may be controlled as a control parameter together with the exposure time. This is because, in a moving image, the upper limit of the exposure time is the sampling period for each pixel, and therefore when the exposure time is equal to the sampling period, it is necessary to increase the sampling period when further increasing the exposure time. Further, instead of the exposure time or in combination with the exposure time, the gain in the AGC may be controlled as a control parameter.
In the embodiment described above, P control is mainly used as an example. However, any method may be used as long as it is a method for calculating a control variable such as an exposure time so as to reduce the difference between the control amount and the target amount. It may be used. For example, PI (Proportional-Integral Control) control and PID (Proportional-Integral-Differential Control) control may be used.

As described above, the endoscope apparatus 1 according to the present embodiment includes the insertion unit 10 including the CCD image sensor 104 at the distal end. Further, the endoscope apparatus 1 includes a hunting detection unit 145 that detects a hunting state based on the luminance of an image from the CCD image sensor 104 and a halation detection unit 146 that detects a halation state of the image. The endoscope apparatus 1 further includes an imaging control unit 147 that controls the luminance based on the hunting state and the halation state.
With this configuration, the brightness is controlled based on the hunting state and the halation state detected based on the captured brightness. Therefore, the occurrence of hunting and halation is suppressed as much as possible.

The hunting detection unit 145 detects the hunting state based on the periodicity of the luminance variation.
With this configuration, the hunting state is detected based on the periodicity of the luminance of the captured image. Since the hunting state can be determined from the luminance variation mixed with the original luminance variation of the subject image, the luminance is controlled based on the accurately determined hunting state.

Further, the halation detection unit 146 detects the halation state based on the luminance for each block, which is a partial area of the image.
With this configuration, the halation state is detected based on the luminance of each partial region of the image. For this reason, the luminance is controlled based on the distribution of the halation state.

  Further, the imaging control unit 147 makes the brightness control speed lower than the control speed when hunting is not detected when hunting is detected. In addition, when the imaging control unit 147 detects halation while detecting hunting, the imaging control unit 147 increases the control speed of the exposure time compared to when only hunting is detected. With this configuration, the brightness control speed decreases when hunting is detected. Therefore, when hunting is detected, hunting can be eliminated by the control, and excessive control can be suppressed. In addition, when the imaging control unit 147 detects halation while detecting hunting, the frequency of occurrence of halation is increased by increasing the control speed of the exposure time compared to the case where only hunting is detected. Can be suppressed.

In addition, the imaging control unit 147 stops the control when the luminance fluctuation period is within a predetermined fluctuation period.
With this configuration, by setting the luminance fluctuation period specific to the subject in the imaging control unit 147, the control is stopped when the luminance fluctuation period falls within the set fluctuation period. Therefore, when the luminance varies according to the characteristics of the subject, unnecessary control according to the variation is not performed, so that occurrence of hunting is avoided.

The endoscope apparatus 1 includes an acceleration sensor 108 that detects the acceleration at the tip, and the imaging control unit 147 controls the luminance based on the acceleration.
With this configuration, when the distal end portion of the insertion portion 10 is inserted into the subject, the luminance of the image to be captured is controlled according to the acceleration accompanying the movement. For this reason, the luminance of the image that fluctuates due to the change in the part of the subject that is imaged with the movement is controlled according to the state of the movement.

When it is determined that the tip portion is in operation, the imaging control unit 147 makes the brightness control speed lower than the control speed when hunting or halation is not detected.
With this configuration, when the distal end portion of the insertion portion 10 is being inserted into the subject, the image brightness control speed is reduced. For this reason, hunting is suppressed because excessive control is not performed by suppressing the influence of fluctuations in the luminance of the image due to insertion.

  Note that a part of the endoscope apparatus 1 according to the above-described embodiment, for example, the system control unit 110 and the image processing unit 140 is realized by a computer including a CPU, a memory, an input / output interface, a computer-readable recording medium, and the like. You may do it. In that case, a program for realizing the control function may be recorded on the recording medium, and the recorded program may be read by the computer system and executed. Here, the “computer system” is a computer system built in the endoscope apparatus 1 and includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” is a medium that dynamically holds a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, In this case, a volatile memory inside a computer system that serves as a server or a client may be included that holds a program for a certain period of time. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  Further, part or all of the endoscope apparatus 1 according to the above-described embodiment may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each functional block of the endoscope apparatus 1 may be individually made into a processor, or a part or all of them may be integrated into a processor. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to the advancement of semiconductor technology, an integrated circuit based on the technology may be used.

  For example, instead of a CCD image sensor, another type of image sensor such as a CMOS image sensor may be used as the image sensor. The LED 106 may be provided in the main body 11. In that case, the insertion unit 10 may be provided with a light guide that transmits light from the LED 106 to the objective lens 105 and emits the light from the distal end of the insertion unit 10. Further, the LCD 118 may be omitted in the main body unit 11 as long as it can receive an image signal from the system control unit 110 and display an image based on the received image signal.

As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment and its modification. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention.
Further, the present invention is not limited by the above description, and is limited only by the scope of the appended claims.

DESCRIPTION OF SYMBOLS 1 ... Endoscope apparatus, 10 ... Insertion part, 11 ... Main part, 104 ... CCD image pick-up element, 105 ... Objective lens, 106 ... LED, 107 ... Thermistor, 108 ... Acceleration sensor, 109 ... Wire fixing part, 110 ... System Control unit, 110a ... Image recording unit, 110b ... LCD controller, 111 ... User interface unit, 112 ... Storage medium, 113 ... Parameter storage unit, 114 ... Timing generator, 115 ... CCD drive circuit, 118 ... LCD, 119 ... LED drive Circuit 121, bending controller 122 UD bending motor 123 RL bending motor 124, 125 wire connecting part 126 bending wire 134, 135 detachable connector 136 preamplifier 137 AFE 140 ... Image processing unit, 142 ... Black correction unit, 143 ... Pixel interpolation Luminance and color difference conversion unit, 144 ... correction processing unit, 145 ... hunting detection unit, 146 ... halation detection unit, 147 ... imaging control unit

Claims (9)

An insertion unit having an imaging unit at the tip;
A hunting detection unit for detecting a hunting state based on luminance of an image from the imaging unit;
A halation detector for detecting the halation state of the image;
An imaging control unit that controls the luminance based on the hunting state and the halation state;
An endoscope apparatus comprising:   The endoscope apparatus according to claim 1, wherein the hunting detection unit detects the hunting state based on periodicity of the luminance variation.   The endoscope apparatus according to claim 1, wherein the halation detection unit detects the halation state based on luminance for each block, which is a partial area of the image.   The endoscope according to any one of claims 1 to 3, wherein the imaging control unit makes the brightness control speed lower than the control speed when hunting is not detected when hunting is detected. apparatus.   The said imaging control part raises the control speed of the said brightness | luminance compared with the case where only the hunting is detected when the halation is detected while detecting the hunting. The endoscope apparatus described in 1.   The endoscope apparatus according to claim 4, wherein the imaging control unit stops the control when the luminance fluctuation period is within a predetermined fluctuation period. An acceleration detection unit for detecting the acceleration of the tip;
The endoscope apparatus according to any one of claims 1 to 6, wherein the imaging control unit controls the brightness based on the acceleration.   The endoscope apparatus according to claim 7, wherein, when it is determined that the distal end is in operation, the imaging control unit sets the brightness control speed lower than the control speed when hunting or halation is not detected. A method for controlling an endoscope apparatus, comprising:
A hunting detection process for detecting a hunting state based on the brightness of an image from an imaging unit provided at the tip of the insertion unit;
A halation detection process for detecting a halation state of the image;
An imaging control process for controlling the brightness based on the hunting state and the halation state;
A control method.

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