JP5225146B2 - Automatic dimming processing device for diagnostic medical device, image signal processing device for diagnostic medical device, and medical system - Google Patents

Description

  The present invention relates to an automatic light adjustment processing device for a medical device for diagnosis that automatically adjusts the amount of illumination light that illuminates a subject, an image signal processing device equipped with the automatic light adjustment processing device, and the image signal processing device. Specifically, an automatic dimming processing device suitable for use of an electronic scope, a medical processor equipped with the automatic dimming processing device, and a medical system having an electronic scope and a medical processor About.

  An electronic scope is generally known as a medical device used when a doctor observes a body cavity of a patient. A doctor who uses the electronic scope inserts the insertion portion of the electronic scope into the body cavity and guides the distal end portion provided at the distal end of the insertion portion to the vicinity of the observation target. A doctor operates an operation unit of an electronic scope or a video processor as necessary in order to take an image of the inside of a body cavity with a solid-state imaging device such as a CCD (Charge Coupled Device) mounted on the tip. A doctor observes an image in the body cavity obtained as a result of various operations through a monitor, and performs examinations and treatments.

  The medical system includes a light source device that illuminates a body cavity where natural light does not reach. The light source device is equipped with an automatic light control function for always displaying an image of a subject on a monitor with appropriate brightness. According to the automatic light control function, the brightness of the subject is detected as a luminance value, and the aperture of the diaphragm between the light guide incident end of the electronic scope and the light source is controlled based on the detected luminance value. Thereby, the light quantity of the illumination light by a light source will be adjusted automatically.

  In this type of light control method, for example, an average luminance value indicating an average value of the brightness of the subject is calculated. Next, the calculated average luminance value is compared with a reference luminance value indicating the brightness that is the standard of the subject image. Based on the difference between the average luminance value and the reference luminance value, the movement amount of the diaphragm until the diaphragm reaches the target position is calculated. The motor is driven according to the calculated movement amount of the diaphragm to control the opening degree of the diaphragm, and the amount of illumination light from the light source is adjusted. An example of a light source device in which an automatic light control function is mounted is disclosed in Patent Document 1.

JP 2005-21445 A

  By the way, in the field of endoscopes, various types of electronic scopes such as bronchial scopes and digestive system scopes are generally used depending on the observation site. Typical equipment is used. In other words, different types of electronic scopes corresponding to the observation site are connected to one light source device, and inspection is performed. In recent years, for example, when an inspection is performed using an electronic scope corresponding to observation of special light that reacts with a specific part, a light source device common to other electronic scopes is used.

  Special light observation compatible electronic scopes are generally compatible with color images, and the amount of incident light from the subject (for example, fluorescence excited by excitation light or light of a narrow band wavelength for observing blood vessel shape) It is much lower than the electronic scope. Therefore, a solid-state imaging device with high sensitivity is mounted to compensate for the shortage of the amount of light of the subject, and an image with appropriate brightness is obtained.

  However, the automatic light control function of a general light source device is designed to be suitable for, for example, a color image-compatible electronic scope. Therefore, when a special light observation compatible electronic scope is used, due to the difference in sensitivity from the color image compatible electronic scope (that is, the signal of the negative feedback amplification circuit in the special light observation compatible electronic scope). Since the amplification factor inevitably decreases), the response speed of automatic dimming decreases. When the brightness of the subject fluctuates abruptly (for example, when switching from normal observation to special light observation or when the observation area is moved), the brightness of the image cannot be followed with an appropriate response speed, and the image is momentarily displayed. The problem is that it becomes too dark or bright.

  Note that the above problem due to the response speed of automatic light control is not caused only by the difference in sensitivity of the solid-state imaging device. For example, the sensitivity of the electronic scope as a whole varies depending on the number of pixels of the solid-state imaging device, the optical path of illumination light, the diffusion range, the numerical aperture of the objective lens, the depth of field (aperture setting), etc. The response speed of light is different (the response speed is lowered in an electronic scope with low sensitivity), and the above problem occurs.

  The present invention has been made in view of the above circumstances, and the purpose of the present invention is to provide a diagnosis having an automatic dimming function with a fast and stable automatic dimming response speed when any electronic scope is used. An object of the present invention is to provide an automatic light control processing device for medical equipment, an image signal processing device equipped with the automatic light control processing device, and a medical system having the image signal processing device.

  An automatic light control processing device for a medical device for diagnosis according to an embodiment of the present invention that solves the above-described problem includes a light source that irradiates illumination light, and a diaphragm that adjusts the amount of the irradiated illumination light by varying the opening degree. A luminance that generates a luminance signal from an image signal generated by the imaging device capturing a member, an illumination light supply unit that supplies adjusted illumination light to a predetermined imaging device, and a subject illuminated by the supplied illumination light A signal generation unit, a signal level conversion unit that converts the level of the generated luminance signal, a luminance value calculation unit that calculates the luminance value of the image based on the luminance signal subjected to the level conversion, and the calculated luminance A target opening setting unit for setting a target opening of the throttle member based on a difference between the value and a predetermined reference luminance value, and a throttle operation control for operating the throttle member toward the target opening at a speed corresponding to the difference Part. When the level of the generated luminance signal falls within a range near the reference level including the reference level corresponding to the reference luminance value, the signal level conversion unit converts the level of the luminance signal at the first change rate. When the level of the generated luminance signal exceeds the upper limit of the above range, the signal level conversion unit outputs the luminance signal to the first level so that the higher the level is, the higher the level of the converted luminance signal is. Level conversion is performed at a second change rate higher than the change rate. When the level of the generated luminance signal falls below the lower limit of the above range, the signal level conversion unit converts the luminance signal to the first level so that the lower the level is, the lower the converted luminance signal level is. Level conversion is performed at a third rate of change higher than the rate of change.

  As described above, the automatic light control processing device according to the present invention is configured such that the brightness value of the image is compared with the reference brightness value so that the brightness of the image follows the rapid change in brightness of the subject at an appropriate response speed. In this case, the throttle member is operated at a high speed when it greatly deviates, so that the opening degree of the throttle member quickly reaches the target opening degree. Regardless of which imaging device is used, automatic light control with high response speed and stability is achieved. The automatic light control with stable response speed means that a difference in response speed of automatic light control in various imaging devices is within a certain range.

  The automatic light control processing device for a diagnostic medical device according to the present invention may further include an image sensor drive control unit that controls driving of an image sensor included in the image pickup device. In this case, when the level of the generated luminance signal exceeds a first level threshold value that is higher than the upper limit of the above range, the imaging device drive control unit moves the imaging device to a high-speed electronic device that is faster than a predetermined normal electronic shutter speed. Operate at shutter speed. On the other hand, when the level of the generated luminance signal falls below a second level threshold value that is lower than the lower limit of the range, the image sensor is operated at an electronic shutter speed that is slower than the high-speed electronic shutter speed.

  When the operation control of the diaphragm member and the electronic shutter speed control of the image sensor are used together, the response speed of automatic light control is further increased. Therefore, even when the brightness of the subject changes remarkably rapidly, the brightness of the image can be made to follow at an appropriate response speed.

  The automatic light control processing apparatus for a medical device for diagnosis according to the present invention may further include an opening degree detecting means for detecting the opening degree of the aperture member. In such a case, the image sensor drive control unit varies the electronic shutter speed according to the detected opening. For example, when the detected opening is equal to or less than the first opening threshold, the image sensor drive control unit determines that the image pickup surface of the image sensor is close to the subject and the image blur is likely to occur. For this reason, the image pickup device is operated at a high electronic shutter speed that is faster than the normal electronic shutter speed, thereby making it difficult for image blurring to occur. On the other hand, for example, when the detected opening is greater than or equal to a second opening threshold value that is higher than the first opening threshold value, the image sensor drive control unit is configured to display an image because the distance between the imaging surface of the image sensor and the subject is long. In order to improve the S / N ratio of the signal, the image sensor is operated at an electronic shutter speed slower than the high-speed electronic shutter speed.

  The diaphragm operation control unit may include a DC motor that operates the diaphragm member. In order to effectively suppress hunting of the throttle member in the vicinity of the target opening, the diaphragm operation control unit applies PWM (Pulse Width Modulation) to the DC motor when the level of the generated luminance signal reaches the range from outside the above range. It is good also as a structure driven by control.

  The automatic light control processing device for a medical device for diagnosis according to the present invention may further include an operation unit that receives a reference luminance value setting operation so that a user can observe an image with a desired brightness.

  An image signal processing apparatus for a medical device for diagnosis according to an embodiment of the present invention that solves the above-described problem enables the automatic light control processing apparatus according to any one of the above and an image signal from the imaging apparatus to be displayed on a monitor. And an image signal processing unit for processing.

  A medical system according to an aspect of the present invention that solves the above-described problems is an electronic device that generates an image signal by photographing the subject illuminated by illumination light from the image signal processing device and the automatic light control processing device. With a scope.

  According to the automatic dimming processing device for diagnostic medical devices, the image signal processing device for diagnostic medical devices, and the medical system according to the present invention, the response speed is fast and stable when any electronic scope is used. Automatic dimming is achieved.

It is a block diagram showing roughly the composition of the medical system of the embodiment of the present invention. It is a block diagram which shows the structure of the front | former stage signal processing circuit and its peripheral circuit of embodiment of this invention. It is a figure which shows the conversion characteristic of the luminance signal level of LUT of embodiment of this invention. It is a figure which shows the conversion characteristic of the signal level of LUT after the brightness adjustment operation with respect to the front panel of embodiment of this invention. It is a figure which shows the relationship between the level of the input signal to LUT of embodiment of this invention, and the drive signal applied to a motor. It is a figure for demonstrating the electronic shutter speed control of the solid-state image sensor of embodiment of this invention.

  Hereinafter, a medical system according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram schematically showing the configuration of the medical system 1 of the present embodiment. As shown in FIG. 1, a medical system 1 includes an electronic scope 100 that images a body cavity, and a processor 200 that illuminates a body cavity that does not reach natural light through the electronic scope 100 and simultaneously processes a signal from the electronic scope 100. And a monitor 300 for displaying the signal processed by the processor 200 as an image.

  The processor 200 includes a system controller 202 and a timing controller 204. The system controller 202 controls each element constituting the medical system 1. The timing controller 204 outputs a clock pulse for adjusting the signal processing timing to each circuit in the medical system 1.

  When the power of the processor 200 is turned on, power is supplied from the lamp power source 206 to the lamp 208 and the lamp 208 is lit. As the lamp 208, a high-intensity lamp such as a xenon lamp, a halogen lamp, a mercury lamp, or a metal halide lamp is suitable. Illumination light emitted from the lamp 208 is collected by the condenser lens 210, is limited to an appropriate amount of light through the diaphragm 212, and is incident on an LCB (light carrying bundle) 102 included in the electronic scope 100.

  A motor 214 is mechanically connected to the diaphragm 212 via a transmission mechanism such as an arm or a gear (not shown). The motor 214 is a DC motor, for example, and is driven under the drive control of the driver 216. The diaphragm 212 is operated by the motor 214 to change the opening degree so that the image displayed on the monitor 300 has an appropriate brightness, and limits the amount of illumination light emitted from the lamp 208 according to the opening degree. To do. Note that the appropriate reference for the brightness of the image changes according to the brightness adjustment operation of the front panel 218 by the operator.

  The light incident on the LCB 102 propagates through the LCB 102 and is emitted from the exit end of the LCB 102 disposed at the distal end of the electronic scope 100. The light emitted from the LCB 102 illuminates the subject via the light distribution lens 104. The reflected light from the subject enters the objective lens 106 and forms an optical image on the light receiving surface of the solid-state image sensor 108 by the power of the objective lens 106.

  The solid-state image sensor 108 is, for example, a single-plate color CCD having a Bayer-type pixel arrangement, accumulates an optical image formed by each pixel on the light receiving surface as charges according to the amount of light, and each color of R, G, B Is converted into an image signal corresponding to. The converted image signal is amplified by the preamplifier 110 and input to the driver signal processing circuit 112.

  Based on the clock pulse of the timing controller 204, the driver signal processing circuit 112 drives and controls the solid-state imaging device 108 at a timing synchronized with the frame rate of the video processed on the processor 200 side. The memory 114 stores information unique to the electronic scope 100 (for example, the number and sensitivity of pixels of the solid-state imaging device 108, a compatible rate, or a model number). The driver signal processing circuit 112 accesses the memory 114 and reads information unique to the electronic scope 100. The driver signal processing circuit 112 outputs the read unique information to the system controller 202 and the image signal to the pre-stage signal processing circuit 220, respectively. An insulation circuit (not shown) using a photocoupler or the like is disposed between the driver signal processing circuit 112 and the previous signal processing circuit 220, and the electronic scope 100 and the processor 200 are electrically insulated.

  The system controller 202 performs various calculations based on the specific information from the driver signal processing circuit 112 to generate a control signal, and performs processing suitable for the electronic scope connected to the processor 200. Control the operation and timing of each circuit. Further, the system controller 202 may be configured to have a table in which a model number of the electronic scope is associated with control information suitable for the electronic scope of the model number. In such a case, the system controller 202 refers to the control information in the correspondence table and controls the operation and timing of each circuit in the processor 200 so that processing suitable for the electronic scope connected to the processor 200 is performed.

  FIG. 2 is a block diagram showing the configuration of the pre-stage signal processing circuit 220 and its peripheral circuits. The image signal from the driver signal processing circuit 112 is converted into a digital format by the A / D converter 14 after signal amplification by the amplifier 10 and noise cut by the filter 12. The image signal converted into the digital format is output to the image signal processing circuit 16 and the luminance signal generation circuit 17.

  The image signal processing circuit 16 performs predetermined processing on the image signal from the A / D converter 14 and outputs it to the image memory 222. The image memory 222 is a frame buffer that buffers input image signals. The image memory 222 sweeps the buffered image signal to the subsequent video signal processing circuit 224 at a predetermined timing. The post-stage video signal processing circuit 224 converts the image signal from the image memory 222 into a video signal conforming to a predetermined video standard such as NTSC (National Television System Committee) and outputs the video signal to the monitor 300. As a result, the image of the subject is displayed on the monitor 300. The surgeon can observe the image in the body cavity through the monitor 300 and perform an examination or a treatment.

  The luminance signal generation circuit 17 calculates a luminance signal for one frame based on an image signal corresponding to each of R, G, and B colors from the A / D converter 14 and outputs the calculated luminance signal to an LUT (Look up Table) 18. The LUT 18 is an input / output correspondence table for converting the level of the input luminance signal. FIG. 3 shows the luminance signal level conversion characteristics of the LUT 18. The horizontal axis in FIG. 3 indicates the level of the luminance signal input to the LUT 18, and the vertical axis in FIG. 3 indicates the level of the luminance signal output from the LUT 18.

  As shown in FIG. 3, the conversion characteristic of the luminance signal level of the LUT 18 is based on the median c of the stable region B, and the stable region B with a low rate of increase or decrease of the output level relative to the input level. High-speed areas A1 and A2 having a high level decrease rate and high-speed areas A3 and A4 having a high output level increase rate with respect to the input level are included. According to another expression, the LUT 18 is configured to level-convert the input luminance signal with a coefficient corresponding to the input level. As shown in FIG. 3, the high speed region A1 is defined as a region where the input level is below the point a '. The high speed region A2 is defined as a region where the input level is greater than or equal to the point a 'and less than the point a. The stable region B is defined as a region where the input level is higher than the point a and lower than the point b. The high speed region A3 is defined as a region where the input level is not less than the point b and below the point b '. The high speed region A4 is defined as a region where the input level is equal to or higher than the point b '. The high-speed areas A1 to A4 are defined as areas where the input luminance signal is level-converted with a higher coefficient than the stable area B.

  The input / output correspondence table of the LUT 18 is prepared for each luminance adjustment value on the front panel 218. For example, when the luminance can be adjusted in ten steps, there are ten input / output correspondence tables of the LUT 18. FIG. 4 shows the characteristics of the input / output correspondence table when the brightness is increased by a predetermined level from the set brightness corresponding to FIG. As shown in FIG. 4, the input / output correspondence table of the LUT 18 has a characteristic in which each of the high speed areas A1 to A4 and the stable area B is entirely shifted in accordance with the adjustment amount of the luminance.

  The level of the luminance signal input to the LUT 18 is controlled by negative feedback and converged to a level in the stable region B (for example, the median value c of the stable region B). Here, the negative feedback control will be described in detail.

  The LUT 18 converts the level of the input luminance signal with a coefficient corresponding to the input level, and outputs it to the histogram processing circuit 20. The histogram processing circuit 20 performs histogram processing using the input luminance signal. The histogram processing circuit 20 calculates an average luminance value indicating the average value of the luminance of the subject image for one frame using the generated histogram data. The histogram processing circuit 20 compares the calculated average luminance value with a reference luminance value corresponding to the luminance value set on the front panel 218 to obtain a difference. Here, the reference luminance value is a luminance value indicating the brightness that is the standard of the subject image, and is determined in advance for each luminance setting value on the front panel 218. More specifically, the reference luminance value is defined as a luminance value corresponding to the input level of the median value c of the stable region B, for example.

  Based on the difference between the average luminance value and the reference luminance value, the histogram processing circuit 20 is ideal for matching the target opening of the aperture 212 (that is, the input level to the LUT 18 with the median value c of the stable region B). Or an approximate opening for keeping the input level to the LUT 18 at an arbitrary level within the stable region B, and hereinafter referred to as “target opening”. Then, the calculated target opening is output to the negative input terminal of the comparator 22 via SW1 (when SW1 is switched to the side indicated by the solid line in FIG. 2). Note that switching with respect to SW1 and SW2, which will be described later, is controlled at the timing by the timing circuit 34.

  The opening (actual value) of the diaphragm 212 is input from the register 32 described later to the + input terminal of the comparator 22. The comparator 22 compares the measured opening of the throttle 212 with the target opening, and outputs a signal corresponding to the difference to the driver 216 via the D / A converter 24. The driver 216 supplies a voltage corresponding to the input signal to the motor 214 and drives it to adjust the opening degree of the diaphragm 212. The motor 214 is supplied with a voltage that is proportional to the difference between the actually measured opening of the diaphragm 212 and the target opening. That is, the motor 214 applies a higher voltage as the difference between the actually measured opening and the target opening of the diaphragm 212 is larger, and operates the diaphragm 212 at a high speed.

  When the motor 214 rotates by a predetermined angle with respect to the initial position, the diaphragm 212 also rotates by a predetermined angle with respect to the initial position (for example, the fully closed state) to a predetermined opening degree. That is, the rotation angle with respect to the initial position of the motor 214 and the opening degree of the diaphragm 212 are uniquely determined. The rotation angle with respect to the initial position of the motor 214 is detected by the displacement detector 26. As a specific device example of the displacement detector 26, an optical rotary encoder connected to and supported by the motor 214 is assumed. The rotation angle detected by the displacement detector 26 is written into the register 32 as information indicating the actual opening of the aperture 212 via the preamplifier 27, the filter 28, and the A / D converter 30. Under the timing control by the timing circuit 34, the register 32 sets the written opening of the diaphragm 212 to the + of the comparator 22 via SW2 (when SW2 is switched to the side indicated by the solid line in FIG. 2). Output to the input terminal. The level of the luminance signal input to the LUT 18 is converged to a level in the stable region B by controlling the amount of illumination light accompanying the opening degree adjustment of the stop 212.

  A specific example of the automatic light control processing executed in the medical system 1 will be described with reference to FIG. For example, consider a case where the brightness of the subject suddenly becomes dark due to switching from normal observation to special light observation or moving the observation area, and the signal level input to the LUT 18 falls to a level in the high-speed area A2. In such a case, the level of the luminance signal output from the LUT 18 is further lowered as the input level is lower than in the normal case (when it falls within the stable region B). For this reason, a luminance signal having a level corresponding to a darker image than the actual level is input to the histogram processing circuit 20 from the LUT 18 as the input level to the LUT 18 is lower. As a result, the histogram processing circuit 20 calculates an opening larger than the ideal opening corresponding to the appropriate brightness as the target opening in order to make the image brighter. Since the target opening that is larger than the ideal target opening that is supposed to be proper is input to the comparator 22, the difference output from the comparator 22 increases. Since the difference is large, a high voltage is applied to the motor 214 and the diaphragm 212 operates at high speed.

  The diaphragm 212 operates at a high speed toward an opening exceeding an appropriate target opening while the input level to the LUT 18 falls within the high speed region A2. The opening degree of the throttle 212 approaches the appropriate target opening degree in a shorter time, and the input level to the LUT 18 quickly reaches the stable region B. In the stable region B, the rate of change in the level conversion of the output with respect to the input decreases (for example, decreases to a value close to the same magnification, etc.), so that the LUT 18 outputs a signal having a level suitable for an appropriate target opening. Therefore, when the input level to the LUT 18 reaches the stable region B, the aperture 212 is set to an appropriate target opening (for example, the median value c of the stable region B or an arbitrary value within the stable region B as the input level to the LUT 18). ), The opening degree is changed at a lower speed than the speed corresponding to the high speed region A2. The reason why the speed of the diaphragm 212 in the stable region B is set to a low speed is to suppress hunting of the diaphragm 212 in the vicinity of the target opening.

  According to the above specific example, the opening degree of the diaphragm 212 quickly reaches the target opening degree even when the brightness of the subject suddenly changes, so that the response speed of automatic light control is increased. Therefore, the brightness of the image is kept substantially constant following an abrupt change at an appropriate response speed. For example, even when an electronic scope with low sensitivity is used, automatic light control is performed quickly, and the brightness of the image follows the luminance change at an appropriate response speed. That is, even when any electronic scope is connected to the processor 200 and used, automatic dimming with a high response speed and stability is achieved. Here, the automatic light control with a stable response speed means that the difference in the response speed of the automatic light control in various electronic scopes is within a certain range.

  The processor 200 is configured as described below in order to further suppress hunting of the iris 212 near the target opening. FIG. 5 shows a characteristic diagram for explaining such a configuration. The horizontal axis in FIG. 5 represents the operation time of the diaphragm 212, and the vertical axis in FIG. 5 represents the drive signal applied to the motor 214. FIG. 5 corresponds to the above specific example.

  The luminance signal level input to the LUT 18 is a level corresponding to the high speed region A2 until reaching time t1 in FIG. 5, and is a level corresponding to the stable region B after time t1. The broken line in FIG. 5 is a line obtained by extending the slope of the drive signal after time t1. Such a broken line indicates a virtual drive signal in a case where the target opening is set to the original appropriate opening in the period until the time t1 is reached. During the period until the time t1 is reached, the target opening is set to an opening larger than the original proper opening. Therefore, referring to FIG. 5, it can be seen that the motor 214 is applied with a voltage higher than the broken line until the time t1 is reached, and operates the diaphragm 212 at a high speed.

  Since the aperture 212 operates at a high speed until the time t1 is reached, a large moment of inertia is generated around the rotation axis of the aperture 212. Since the moment of inertia generated at this time is large, even if time t1 has passed and the diaphragm 212 has been slowed down, it does not disappear quickly. Therefore, it may cause the diaphragm 212 to be hunted.

  Therefore, after the time t1 has elapsed (that is, after the luminance signal level input to the LUT 18 reaches the stable region B), the timing circuit 34 switches SW1 and SW2 at a predetermined cycle. By switching SW1 and SW2, the input from the register 32 to the comparator 22 and the output of the comparator 22 become intermittent. The driver 216 generates a brake pulse (for example, a voltage having a PWM waveform) in response to intermittent input from the comparator 22 via the D / A converter 216 and supplies the brake pulse to the motor 214. In FIG. 5, the brake pulse is conceptually illustrated by a vertical line after time t1. The waveform after time t1 is actually a pulse waveform corresponding to, for example, PWM control.

  The moment of inertia around the rotation axis of the diaphragm 212 is greatly attenuated, for example, during the OFF period of the supply voltage of the PWM waveform, and thus is significantly attenuated before the diaphragm 212 reaches the vicinity of the target opening. According to another expression, the diaphragm 212 is substantially decelerated with respect to the speed according to the difference between the actually measured opening degree and the target opening degree by PWM control, so that the moment of inertia is rapidly attenuated. The Therefore, hunting of the diaphragm 212 in the vicinity of the target opening is effectively suppressed. The brake pulse may be a reverse pulse waveform for intermittently reversing the rotation of the motor 214. In such a case, the moment of inertia is further attenuated more quickly, so that a high anti-hunting effect can be obtained.

  By the way, mechanical elements such as the diaphragm 212 and the motor 214 have an operation characteristic that the follow-up is delayed with respect to a sudden change. For this reason, for example, when the brightness variation of the subject is remarkably abrupt, it is assumed that it is not possible to cope with the increase in the speed of the stop 212 alone. Therefore, the processor 200 according to the present embodiment is configured to use the electronic shutter of the solid-state imaging device 108 in order to follow the brightness of the image at an appropriate response speed even when the brightness of the subject changes remarkably. Has been.

  FIG. 6 is a diagram for explaining the electronic shutter speed control of the solid-state image sensor 108. The horizontal axis in FIG. 6 represents time, and the vertical axis in FIG. 6 represents shutter speed. The signal level input to the LUT 18 is a level corresponding to, for example, the stable region B or the high speed region A2 or A3 until the time t2 in FIG. 6 is reached. At this time, the difference between the actually measured opening of the throttle 212 and the target opening is equal to or less than a certain difference. For this reason, the brightness of the image can sufficiently follow the fluctuation of the brightness of the subject only by increasing the speed of the stop 212. Therefore, the solid-state image sensor 108 operates at a normal electronic shutter speed (1 / n second).

  For example, let us consider a case where the brightness of the subject suddenly increases when the time t2 in FIG. 6 is reached, and the signal level input to the LUT 18 rises to a level corresponding to the high speed region A4. At this time, since the difference between the actually measured opening and the target opening of the aperture 212 is too wide, the brightness of the image cannot sufficiently follow the fluctuation of the brightness of the subject only by increasing the speed of the aperture 212. . Therefore, the system controller 202 increases the electronic shutter speed of the solid-state imaging device 108 via the timing controller 204 and the driver signal processing circuit 112.

  Specifically, the system controller 202 gradually increases the electronic shutter speed of the solid-state image sensor 108 from the normal speed, and after a predetermined time (time t3 in FIG. 6), the high-speed electronic shutter speed (1 / 4 n seconds). By increasing the electronic shutter speed, the amount of charge accumulated in each pixel of the solid-state image sensor 108 decreases. As a result, the brightness of the video becomes dark, and the signal level input to the LUT 18 decreases to the stable region B side. At the same time, the opening degree of the throttle 212 is throttled to the fully closed side under the negative feedback control, and the signal level input to the LUT 18 is lowered to the stable region B side. As described above, when the opening degree adjustment of the diaphragm 212 and the electronic shutter speed control of the solid-state image sensor 108 are used in combination, the response speed of the automatic light control is further increased. Therefore, even when the brightness of the subject changes remarkably rapidly, the brightness of the image can be made to follow at an appropriate response speed.

  The solid-state image sensor 108 continues to operate at a high electronic shutter speed until the brightness of the subject suddenly becomes dark and, for example, the signal level input to the LUT 18 decreases to a level corresponding to the high speed region A1. The signal level input to the LUT 18 decreases to a level corresponding to the high speed region A1 when the time t4 in FIG. 6 is reached, for example. At this time, since the difference between the actually measured opening and the target opening of the aperture 212 is too wide, the brightness of the image cannot sufficiently follow the fluctuation of the brightness of the subject only by increasing the speed of the aperture 212. . Therefore, the system controller 202 gradually decreases the electronic shutter speed of the solid-state imaging device 108 from the high speed (1/4 nsec), and after a predetermined time (time t5 in FIG. 6), the normal electronic shutter speed (1 / N seconds). As the electronic shutter speed decreases, the amount of charge accumulated in each pixel of the solid-state image sensor 108 increases. As a result, the brightness of the video becomes brighter, and the signal level input to the LUT 18 increases to the stable region B side. At the same time, the opening degree of the diaphragm 212 is opened to the fully open side under the negative feedback control described above, and the signal level input to the LUT 18 increases to the stable region B side. By using the diaphragm 212 and the solid-state image sensor 108 in combination, the response speed of automatic light control is further increased. Therefore, even when the brightness of the subject fluctuates remarkably, the image brightness can be set at an appropriate response speed. Can be followed.

  The change rate (slope of the graph in FIG. 6) and the maximum speed (1/4 nsec in FIG. 6) of the electronic shutter speed of the solid-state image sensor 108 are the specifications of the solid-state image sensor (number of pixels, sensitivity, rates that can be handled, etc.) The appropriate value changes depending on Therefore, the system controller 202 sets an appropriate electronic shutter speed change rate and maximum speed for the solid-state image sensor 108 for each electronic scope in accordance with the unique information from the driver signal processing circuit 112.

  Here, when the distance between the imaging surface of the electronic scope 100 (the light-receiving surface of the solid-state imaging device 108) and the subject is short, the subject to be photographed is caused by the movement of the subject itself or the camera shake of the electronic scope 100. Image blur is likely to occur in the image. Image blur is undesirable because it degrades image quality. The system controller 202 performs the following operation in order to eliminate such image blur during macro shooting.

  Specifically, when the diaphragm 212 reaches the target opening (that is, when the output of the comparator 22 is substantially 0), SW1 is switched to the side indicated by the broken line in FIG. Thereafter, the output of the A / D converter 30 is input to the + input terminal of the comparator 22 via the register 32 and SW2, and to the − input terminal of the comparator 22 via SW1. That is, since the same signal is input to both input terminals of the comparator 22, the difference output by the comparator 22 is fixed to 0 and the opening degree of the diaphragm 212 is locked.

  Since the opening degree of the diaphragm 212 is locked, the opening degree information having a fixed value is continuously input from the A / D converter 30 to the opening degree comparator 36. The opening degree comparator 36 uses the actually measured opening that is input as a first reference opening (for example, an opening with an opening ratio of 30% for full opening) and a second reference opening (for example with an opening ratio of 80% for full opening). Compare each with (opening).

  Here, in general, when the imaging surface of the electronic scope and the subject approach each other, the amount of light of the subject image increases, so that the diaphragm is easily narrowed to the fully closed side. On the other hand, when the distance between the imaging surface of the electronic scope and the subject is increased, the amount of light of the subject image decreases, so that the aperture is easily opened to the fully open side. The opening degree comparator 36 controls the electronic shutter speed of the solid-state imaging device 108 via the driver signal processing circuit 112 using such aperture opening / closing characteristics.

  That is, when the measured opening from the A / D converter 30 is equal to or smaller than the first reference opening, the opening degree comparator 36 has a short distance between the imaging surface of the electronic scope and the subject and causes image blurring. Judge that the situation is easy. The opening degree comparator 36 operates the solid-state imaging device 108 at a high electronic shutter speed (1/4 nsec). At the same time, SW1 is switched to the histogram processing circuit 20 side, and the diaphragm 21 is unlocked. By increasing the electronic shutter speed, the above-described image blur is less likely to occur, and the image quality of the video is improved.

  Thereafter, the aperture 212 is easily opened to the fully open side to compensate for the decrease in the amount of charge accumulated in each pixel due to the increase in the electronic shutter speed. When the measured opening from the A / D converter 30 reaches the second reference opening, the opening comparator 36 determines that the distance between the imaging surface of the electronic scope and the subject has been increased. At this time, the opening degree comparator 36 reduces the electronic shutter speed of the solid-state image sensor 108 to the normal speed (1 / n second). By reducing the electronic shutter speed, the S / N ratio of the image signal generated by the solid-state image sensor 108 is improved.

  On the other hand, the opening degree comparator 36 determines that the distance between the imaging surface of the electronic scope and the subject is long when the locked actual opening degree from the A / D converter 30 is equal to or larger than the second reference opening degree. To do. The opening degree comparator 36 operates the solid-state imaging device 108 at a normal electronic shutter speed (1 / n second) in order to improve the S / N ratio of the image signal. At the same time, SW1 is switched to the histogram processing circuit 20 side, and the diaphragm 212 is unlocked.

  The diaphragm 212 is easily closed to the fully closed side in order to offset the increase in the charge accumulation amount of each pixel due to the reduction in the electronic shutter speed. When the measured opening degree from the A / D converter 30 reaches the first reference opening degree, the opening degree comparator 36 determines that the imaging surface of the electronic scope and the subject are close to each other. At this time, the opening degree comparator 36 operates the solid-state imaging device 108 at a high electronic shutter speed (1/4 nsec) in order to eliminate image blur.

  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. For example, the medical system 1 may have a configuration corresponding to the frame sequential method.

1 Medical system 18 LUT
20 Histogram processing circuit 100 Electronic scope 108 Solid-state imaging device 200 Processor 202 System controller 204 Timing controller 208 Lamp 212 Aperture 300 Monitor

Claims (8)

A light source that emits illumination light;
A diaphragm member that adjusts the amount of the irradiated illumination light by varying the opening;
An illumination light supply unit for supplying the adjusted illumination light to a predetermined imaging device;
A luminance signal generation unit that generates a luminance signal from an image signal generated by the imaging device shooting an object illuminated by the supplied illumination light; and
A signal level converter for converting the level of the generated luminance signal;
A luminance value calculation unit for calculating the luminance value of the image based on the luminance signal subjected to the level conversion;
A target opening setting unit that sets a target opening of the throttle member based on a difference between the calculated luminance value and a predetermined reference luminance value;
An aperture operation control unit that operates the aperture member toward the target opening at a speed according to the difference;
Have
The signal level converter is
When the level of the generated luminance signal falls within a range near the reference level including a reference level corresponding to the reference luminance value, the luminance signal is level-converted at a first rate of change,
When the level of the generated luminance signal exceeds the upper limit of the range, the luminance signal is set to the first level so that the higher the level of the generated luminance signal is, the higher the level of the luminance signal is. Level change at a second rate of change higher than the rate of change,
When the level of the generated luminance signal falls below the lower limit of the range, the luminance signal is reduced to the first level so that the lower the level of the generated luminance signal, the lower the level of the luminance signal. An automatic light control device for a medical device for diagnosis, characterized in that level conversion is performed at a third rate of change higher than the rate of change. An image sensor driving control unit that controls driving of the image sensor included in the imaging device;
The image sensor drive control unit
When the level of the generated luminance signal exceeds a first level threshold higher than the upper limit of the range, the imaging device is operated at a high electronic shutter speed that is faster than a predetermined normal electronic shutter speed,
The imaging device is operated at an electronic shutter speed slower than the high-speed electronic shutter speed when a level of the generated luminance signal falls below a second level threshold value lower than a lower limit of the range. Item 2. An automatic light control processing device for a medical device for diagnosis according to Item 1. Further comprising opening degree detecting means for detecting the opening degree of the throttle member;
The automatic dimming processing device for a medical device for diagnosis according to claim 2, wherein the imaging element drive control unit varies the electronic shutter speed according to the detected opening degree. The image sensor drive control unit
When the detected opening is equal to or less than a first opening threshold, the image sensor is operated at a high electronic shutter speed that is faster than the normal electronic shutter speed,
When the detected opening is equal to or higher than a second opening threshold higher than the first opening threshold, the image sensor is operated at an electronic shutter speed slower than the high-speed electronic shutter speed. An automatic light control processing device for a medical device for diagnosis according to claim 3. The aperture operation control unit
A DC motor for operating the aperture member;
The DC motor is driven by PWM (Pulse Width Modulation) control when the level of the generated luminance signal reaches the range from the outside of the range. The automatic light control processing device for medical equipment for diagnosis as described in 2.   The automatic light control processing device for a medical device for diagnosis according to any one of claims 1 to 5, further comprising an operation unit that receives a setting operation of the reference luminance value. An automatic light control processing device for a medical device for diagnosis according to any one of claims 1 to 6,
An image signal processing unit that processes the image signal from the imaging device so that it can be displayed on a monitor;
An image signal processing device for a medical device for diagnosis. An image signal processing device for a diagnostic medical device according to claim 7,
An electronic scope that shoots a subject illuminated by illumination light from the automatic light control processing device and generates an image signal;
Having a medical system.

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