JP5636177B2 - Endoscope system and endoscope - Google Patents

Description

  The present invention relates to an endoscope system, and more particularly to an endoscope system that supplies flickering light to an endoscope provided with a CMOS as an imaging device.

  In general, an endoscope system for diagnosing or treating the inside of a body cavity of a patient includes an electronic endoscope that images the inside of the body cavity with a solid-state imaging device provided at a distal end portion, and an image signal generated by the electronic endoscope And a light source device that supplies light for illuminating the observation site in the body cavity to the electronic endoscope. Some video processors incorporate a light source device. In such an electronic endoscope system, illumination light from the light source device is irradiated from the tip of the electronic endoscope into the body cavity, and the reflected light reflected by the body cavity wall is photoelectrically converted by the imaging device. The electric charge generated by the photoelectric conversion is read as an image signal, transferred to a video processor, and output to a monitor.

  In addition, in a conventional electronic endoscope system, a method for shortening an exposure time in each frame photographed by an imaging element is known in order to clearly capture a moving subject. Patent Document 1 includes an optical chopper (hereinafter referred to as “chopper”) for flickering illumination light between an endoscope light guide and a light source in order to adjust the exposure time. An endoscope light source device is also described. The chopper described in Patent Document 1 has a rotating disk composed of an opening and a light shielding part, and the rotating disk is arranged so as to cross the optical path of illumination light. Then, when the rotating disk rotates at a constant rotation speed, the state where the illumination light passes through the opening and the state where the illumination light is blocked by the light shielding unit are alternately repeated, and the light passing through the rotating disk is periodically It enters the light guide as intermittent illumination light (hereinafter referred to as “flickering light”) that repeats blinking. Further, the exposure time in the image sensor can be adjusted by adjusting the ratio of the opening or the light shielding part in the rotating disk. Furthermore, in the endoscope of Patent Document 1, the rotation of the turntable is controlled so that the passing light blinks in synchronization with the image transfer signal of the endoscope. Thereby, the exposure time in each frame imaged by the image sensor is adjusted to a certain time.

Japanese Patent Publication No. 6-38134

  By the way, an image sensor using a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) is well known as an imaging device for performing photoelectric conversion. A CMOS image sensor has the advantages of lower power consumption and lower cost than a CCD, and being easy to downsize. On the other hand, since CMOS generates a large amount of noise such as dark noise and is inferior to CCD in terms of image quality, CCDs are mainly used in conventional electronic endoscope systems. However, in recent years, improvement in noise has led to an increase in image quality in CMOS, and it has become possible to acquire images that are comparable to CCDs. Along with this, there is a demand for adopting a CMOS image sensor as an imaging element even in an electronic endoscope having a constant problem of diameter reduction and size reduction.

  Here, one of the operational differences between CCD and CMOS is the difference in charge accumulation and transfer methods. Specifically, in the CCD, charge accumulation is started simultaneously in all pixels on the light receiving surface, and charges accumulated in all pixels are transferred simultaneously. On the other hand, in the CMOS, charge accumulation is started in order from the pixels included in the leading line of the light receiving surface, and the charges are sequentially transferred from the leading line after the accumulation is completed. When the electronic endoscope is provided with a CMOS having different charge accumulation and transfer timings for each line as described in Patent Document 1, if flashing light synchronized with the image transfer signal is supplied, the timing of the flashing light is set. The charge accumulation timing differs between the upper part and the lower part of the image. As a result, when a still image is captured using blinking light, particularly for a moving subject, uneven exposure occurs, and the image displayed on the monitor is cracked or distorted. Sometimes.

  Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide an endoscope system capable of supplying blinking light suitable for an endoscope having a CMOS image sensor.

  In order to solve the above problems, according to the present invention, an imaging means for capturing an image in a body cavity, a light source for supplying light for illuminating the body cavity, and an optical path of illumination light supplied from the light source are provided. Illumination light flickering means that periodically flickers illumination light that is arranged and passed, and a control signal for controlling flickering of the illumination light so that the illumination light illuminates the body cavity only during the global exposure period in the imaging means There is provided an endoscope system including a control signal generation unit that generates the illumination light and a blinking control unit that controls the illumination light blinking unit according to the control signal. In addition, the present invention is preferably implemented when, for example, the imaging means is a CMOS image sensor.

  With this configuration, it is possible to irradiate illumination light only during the global exposure period of the imaging means, and even when shooting a fast-moving subject, an appropriate image is generated without causing image cracking or distortion. Can be provided.

  The control signal generation means may generate a control signal based on the charge accumulation start timing of the first line and the charge accumulation start timing of the last line in the CMOS image sensor.

  With this configuration, a control signal based on the charge accumulation timing of the CMOS image sensor can be generated, and the light can be blinked so as to emit illumination light only during the global exposure period of the CMOS image sensor. It becomes possible.

  The illumination light blinking means is composed of a rotating disk having an opening for allowing illumination light supplied from a light source to pass therethrough and a light shielding part for shielding illumination light supplied from the light source. Also good. The endoscope system further includes an opening adjustment unit that adjusts the size of the opening of the turntable, and the opening adjustment unit illuminates the inside of the body cavity only during the global exposure period of the imaging unit. As described above, the opening angle of the opening may be adjusted.

  With this configuration, the opening angle of the opening can be adjusted according to the length of the global exposure period of the imaging unit, and illumination light can be irradiated only during the global exposure period.

  Further, according to the present invention, the imaging means for capturing an image in the body cavity, the light guiding means for propagating the illumination light for illuminating the inside of the body cavity, and the illumination light in the body cavity only during the global exposure period in the imaging means. And a control signal generating means for generating a control signal for controlling blinking of the illumination light so as to illuminate the endoscope.

  Therefore, according to the present invention, even when a CMOS is used as the imaging element of the endoscope, it is possible to supply light that blinks at an appropriate timing, and it is possible to provide an image without breakage.

1 is a schematic configuration diagram of an electronic endoscope system in an embodiment of the present invention. It is (a) enlarged front view and (b) enlarged side view of a turntable in an embodiment of the present invention. It is a figure for demonstrating control of the turntable in embodiment of this invention. It is a figure for demonstrating another example of the turntable control in embodiment of this invention.

  Hereinafter, an electronic endoscope system 1 according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an electronic endoscope system 1 of the present embodiment. The electronic endoscope system 1 is a medical observation system for an operator to observe and diagnose the inside of a patient's body cavity. The electronic endoscope system 1 includes an electronic endoscope 10 for taking an image of a body cavity, a processor 20 to which the electronic endoscope 10 is detachably connected, and a monitor 30.

  The electronic endoscope 10 includes an insertion portion 10a that is a long flexible tube that is inserted into a patient's body, and a connection portion 10c that is electrically and optically connected to the processor 20. A light guide 101 for propagating light supplied from the processor 20 extends from the connection portion 10c of the electronic endoscope 10 to the distal end of the insertion portion 10a. In addition, a light distribution lens 102 for emitting light propagated by the light guide 101 to the observation site is formed at the distal end of the insertion portion 10a, and light reflected from the observation site is imaged on the light receiving surface of the image sensor. And a CMOS image sensor 104 (hereinafter referred to as “CMOS 104”), which is a solid-state imaging device that generates an image signal based on the subject image formed on the light receiving surface.

  Further, the connection unit 10c of the electronic endoscope 10 includes a first-stage signal processing circuit 105 that performs predetermined image processing on an image signal generated by the CMOS 104, a CMOS driving circuit 106 that controls driving of the CMOS 104, and an electronic internal A control circuit 107 that controls each part of the endoscope 10 is provided.

The processor 20 has a system controller 201 and a timing controller 202 for driving and synchronizing the entire electronic endoscope system 1, and a video signal output from the electronic endoscope 10 in a format suitable for display on the monitor 30. A post-stage signal processing circuit 203 for conversion and a light source unit 205 for supplying illumination light to the electronic endoscope 10 are provided. The light source unit 205 includes a light source 251 formed of a high-intensity lamp such as a halogen lamp or a xenon lamp, and a motor control unit 252 that configures an optical chopper for blinking light emitted from the light source 251, a motor driver 253, a motor 254, an encoder 255, a rotating disk 256, and an opening control motor 257 (described only in FIG. 2). The monitor 30 is a display device having a general image receiving function for displaying an image based on the video signal processed by the post-stage signal processing circuit 203.

  In-body cavity observation in the electronic endoscope system 1 having the above-described configuration is performed as follows. First, when the power of the processor 20 is turned on, the light source 251 is driven under the control of the system controller 201. Then, the operator inserts the insertion portion 10a of the electronic endoscope 10 into the patient's body. The continuous light emitted from the light source 251 is converted into flickering light by a turntable 256 disposed in the optical path. Until the switch (not shown) is pressed, the rotating disk is controlled to stop in a light passing state, and continuous light is emitted from the tip. FIG. 2 is an enlarged view of the rotating disk 256. FIG. 2A is a front view of the turntable 256, and FIG. 2B is a side view of the turntable 256.

  The rotating disk 256 is composed of two disks 2561 and 2562 having the same shape around the rotating shaft 256a. Each of the disks 2561 and 2562 constituting the rotating disk 256 is provided with an opening having an opening angle of 180 degrees. The opening 256c of the rotary disk 256 is adjusted between 0 degrees and 180 degrees by rotating the disks 2561 and 2562 separately by the opening control motor 257. The disks 2561 and 2562 are fixed in that state when the opening angle of the opening 256c in the rotating disk 256 is adjusted to a desired angle, and thereafter, the rotation is controlled simultaneously as an integral rotating disk 256. The adjustment of the opening angle in the opening control motor 257 may be manually set by a front panel (not shown) of the processor 20 or automatically by the system controller 201 based on the type of the electronic endoscope 10 connected to the processor 20. May be set automatically.

  A motor 254 and an encoder 255 are attached to the rotating shaft 256 a of the rotating disk 256. The motor 254 is driven according to the drive signal supplied from the motor driver 253, and rotates the rotating disk 256 at a predetermined speed. The encoder 255 is interlocked with the rotating shaft 256a, and outputs an index pulse signal every time the rotating disk 256 makes one rotation. Further, the motor driver 253 drives the motor 254 in accordance with a control signal output from the motor control unit 252.

  The motor control unit 252 is input with a turntable control signal output from the electronic endoscope 10 and an index pulse signal output from the encoder 255. The motor control unit 252 includes a phase comparator, compares the input turntable control signal with the phase of the index pulse signal, and controls the motor 254 so as to eliminate the phase difference to rotate the turntable 256. . That is, in the present embodiment, rotation control of the turntable 256 is performed based on the turntable control signal sent from the electronic endoscope 10. The turntable control signal will be described in detail later.

  The continuous light emitted from the light source 251 enters one end of the light guide 101 when the opening 256b of the turntable 256 is in its optical path. On the other hand, when the light shielding portion 256c of the turntable 256 is in the optical path, light cannot be passed through the turntable 256 because the light is blocked by the light shielding portion 256c. That is, by rotating the turntable 256 by the motor 254, continuous light emitted from the light source 251 can be converted into blinking light.

  The blinking light that has entered the light guide 101 of the electronic endoscope 10 propagates through the light guide 101 and is emitted from the distal end of the insertion portion 10 a through the light distribution lens 102. Then, the light reflected by the living tissue in the body cavity is imaged on the light receiving surface of the CMOS 104 via the objective lens 103. In the CMOS 104, charge accumulation is started in order from the first line on the light receiving surface in accordance with the drive control signal from the CMOS drive circuit 106. Then, in accordance with the transfer signal from the CMOS drive circuit 106, the image signal photoelectrically converted from the first line is read out and sent to the first stage signal processing circuit 105.

  The first-stage signal processing circuit 105 performs predetermined processing on the image signal to generate a video signal including the luminance signal Y and the color difference signals RY and BY. The predetermined processing here includes, for example, clipping processing that limits the dynamic range of the image signal to a predetermined range, and gamma that corrects the γ (gamma) characteristics so that the gradation characteristics and color reproducibility of luminance are appropriate. Correction processing and the like are included. The video signal generated by the first stage signal processing circuit 105 is output to the subsequent stage signal processing circuit 203 of the processor 20.

  In the post-stage signal processing circuit 203, the luminance signal component in the received video signal is subjected to noise reduction processing and the like, such as a luminance signal with reduced noise, a color difference signal, and an NTSC composite video signal obtained by multiplexing the decoded synchronization signal. A video signal is generated. The video signal is output from the processor 20 to the monitor 30, and a subject image based on the video signal is displayed on the monitor 30. Thereby, the surgeon and the diagnostician can observe the state in the body cavity of the patient from the subject image displayed on the monitor 30. In addition, a still image of a subject can be acquired by operating a freeze button (not shown) provided in the operation unit of the electronic endoscope 10 during observation in the body cavity as described above.

  Next, control of the turntable 256 by the turntable control signal will be described with reference to FIG. In each waveform of FIG. 3, the horizontal axis represents time, and the vertical axis represents the output value (the charge amount in FIG. 3A). FIG. 3A is a diagram showing a state of charge accumulation in the CMOS 104. In FIG. 3A, the charge accumulation state of the first line on the light receiving surface of the CMOS 104 is indicated by a solid line, and the charge accumulation state of the final line is indicated by a broken line. As shown in FIG. 3A, in the CMOS 104, the timing for starting charge accumulation differs between the first line and the last line. Here, a period in which charges are accumulated in all pixels from the first line to the last line of the CMOS 104, that is, a period from the start of charge accumulation in the last line until the charge in the first line is transferred. Is called the global exposure period. In the present embodiment, a turntable control signal for controlling the turntable 256 is sent to the CMOS drive circuit 106 of the electronic endoscope 10 so that illumination light is incident on the light guide 101 only during the global exposure period of the CMOS 104. Generated.

  In the CMOS drive circuit 106, an intermediate timing detection signal is first generated. This intermediate timing detection signal is a pulse signal indicating a result of detecting an intermediate timing between the timing of starting the accumulation of the first line of the CMOS 104 and the timing of starting the accumulation of charges on the final line. Here, the time difference between the charge accumulation start timing in the first line and the charge accumulation start timing in the last line is determined by the drive frequency of the CMOS 104 and the number of pixels (number of lines). Therefore, in the CMOS drive circuit 106, based on this time difference, an intermediate timing between the timing of starting accumulation of the first line and the timing of starting accumulation of charge on the last line is detected, and the pulse signal shown in FIG. Is generated.

  Subsequently, in the CMOS drive circuit 106, a turntable control signal is generated based on the intermediate timing detection signal generated as described above and the frame frequency in the CMOS 104. As shown in FIG. 3C, the turntable control signal is a signal that rises in synchronization with the intermediate timing detection signal and falls in synchronization with the charge accumulation end timing of the image signal on the first line. Then, the turntable control signal generated by the CMOS drive circuit 106 is sent to the motor control unit 252.

FIG. 3D shows an index pulse signal output from the encoder 255 that is input to the motor control unit 252 together with the turntable control signal generated by the CMOS drive circuit 106. Here, in the index pulse signal output from the encoder 255, the position of the continuous light beam emitted from the light source 251 is located at the position shown in FIG. 2A, that is, at the center of the light shielding portion 256d of the rotating plate 256. It is a pulse signal that rises every time. Then, the motor control unit 252 controls the turntable 256 so that the turntable control signal and the index pulse signal are synchronized, and as shown in FIG. The rotation of the turntable 256 is controlled so that the illumination light from 251 enters the light guide 101.

  The timing of each part performing such an operation will be described using specific numerical values. In FIG. 3, as an example, the case where the frame frequency of the CMOS 104 is 30 Hz and the time difference between the charge accumulation start timing in the first line and the charge accumulation start timing in the last line is about 11 ms (milliseconds) will be described. In this case, since one frame is about 33 ms, the global exposure period in the CMOS 104 is about 22 ms.

  First, the CMOS driving circuit 106 detects an intermediate timing between the timing of starting the accumulation of the first line of the CMOS 104 and the timing of starting the accumulation of charges on the final line, and rises about 5.5 ms after the start of accumulation of the leading line. A detection signal is generated (FIG. 3B). Further, the turntable control signal generated in synchronization with the intermediate timing detection signal is a signal that rises about 5.5 ms after the start of accumulation of the leading line and falls after about 33 ms, which is the timing of completion of charge accumulation on the leading line. (FIG. 3C).

  Subsequently, the turntable 256 is controlled by the motor control unit 252 to synchronize the turntable control signal that rises about 5.5 ms after the start of accumulation of the head line and the index pulse signal output from the encoder 255. That is, the rotation of the turntable 256 is controlled so that the index pulse signal is output approximately 5.5 ms after the start of accumulation of the first line. Here, the opening angle of the opening 256c of the rotating disk 256 is set to 180 degrees as shown in FIG. Then, due to the positional relationship between the reference position of the index pulse signal on the turntable 256 and the opening 256c, the light source 251 is about 8.75 ms after the rise of the index pulse signal, that is, about 13.75 ms after the start of accumulation of the first line. The continuous light from the light reaches the opening 256c of the turntable 256. Then, the illumination light that has passed through the opening 256c is incident on the light guide 101 for 16.5 ms. In this way, by controlling the turntable 256 based on the turntable control signal, the illumination light from the light source 251 blinks so that the illumination light is incident on the light guide 101 only in the global exposure period of 22 ms in the CMOS 104. It becomes possible to make it.

  Here, as described above, the global exposure period of the CMOS 104 is determined by the frame frequency, the drive frequency, and the number of pixels (number of lines) of the CMOS 104. Therefore, for example, in CMOS 104 ′ (not shown) having the same frame frequency and drive frequency as CMOS 104 and having twice the number of pixels (number of lines), charge accumulation start timing in the first line and charge accumulation start timing in the last line And the time difference between the two times becomes about 22 ms, and the global exposure period becomes about 11 ms. In this case, assuming that the opening angle of the opening 256c of the rotating disk 256 is 180 degrees as described above, the rotating disk 256 makes one round in one frame (33 ms), so that for about 16.5 ms, which is longer than the global exposure period, The illumination light is incident on the light guide 101. In this embodiment, even if the global exposure period is shortened by adjusting the opening angle of the opening 256c in accordance with the length of the global exposure period, the illumination light is transmitted within the electrons only during the CMOS global exposure period. It is configured to be supplied to the endoscope 10.

  The timing of each part in this case will be described using specific numerical values with reference to FIG. FIG. 4A is a diagram showing a state of charge accumulation in the CMOS 104 '. In FIG. 4A, for example, the frame frequency of the CMOS 104 ′ is 30 Hz, and the time difference between the charge accumulation start timing in the first line and the charge accumulation start timing in the last line is about 22 ms (milliseconds). Will be described. In this case, the global exposure period in the CMOS 104 is about 11 ms.

  First, the CMOS drive circuit 106 detects an intermediate timing between the timing of starting the accumulation of the first line of the CMOS 104 and the timing of starting the accumulation of charges on the final line, as described above, and as shown in FIG. Then, an intermediate timing detection signal that rises 11 ms after the start of accumulation of the first line is generated. Further, as shown in FIG. 4C, the turntable control signal generated in synchronization with the intermediate timing detection signal rises 11 ms after the start of the accumulation of the first line and 33 ms after the transfer start timing of the first line. It becomes a falling signal.

  On the other hand, the opening angle of the opening portion 256c of the rotating disk 256 is controlled by the opening control motor 257 so that the opening is performed for a half time (ie, 5.5 ms) of the global exposure period (11 ms) in the CMOS 104. The instruction to the aperture control motor 257 in this case may be set manually by a front panel (not shown) of the processor 20 or automatically by the system controller 201 based on information on the driving frequency and the number of pixels of the CMOS 104 ′. It may be set. Since the turntable 256 makes one rotation at 33 ms, the opening angle for passing 5.5 ms illumination light is 60 degrees. The 60 degree opening 256c is provided centering on a point facing the reference point of the rise of the index pulse signal across the rotation shaft 256a.

  Subsequently, in the motor control unit 252, the rotating disk 256 is controlled so that the rotating disk control signal that rises about 11 ms after the start of accumulation of the leading line and the index pulse signal output from the encoder 255 are synchronized. That is, the rotation of the turntable 256 is controlled so that an index pulse signal is output about 11 ms after the start of accumulation of the first line. Here, the opening angle of the opening 256c of the rotating disk 256 is set to 60 degrees as described above. The continuous light from the light source 251 enters the opening 256c of the turntable 256 after 13.75 ms from the rising edge of the index pulse signal, that is, about 24.75 ms after the start of accumulation of the first line due to the positional relationship in the turntable 256. To reach. Then, the illumination light that has passed through the opening 256 c is incident on the light guide 101 for 5.5 ms thereafter. In this way, by adjusting the opening angle of the opening 256c and controlling the turntable 256 based on the turntable control signal, the illumination light is incident on the light guide 101 only in the global exposure period of 11 ms in the CMOS 104 ′. Thus, the illumination light from the light source 251 can be blinked.

  As described above, in this embodiment, a turntable control signal based on information such as the driving frequency and the number of pixels of the CMOS 104 mounted on the electronic endoscope 10 is generated and transmitted to the motor control unit 252 for motor control. By performing rotation control of the turntable 256 based on the turntable control signal in the unit 252, the illumination light can be blinked so that the illumination light is supplied to the electronic endoscope 10 only during the global exposure period. It becomes possible. Thus, by supplying illumination light to the electronic endoscope 10 only during the global exposure period of the CMOS 104, the charge accumulation timing for each line in the CMOS 104 can be made simultaneously. As a result, even when a fast-moving subject is photographed, an appropriate image can be provided without causing image cracking or distortion.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments and can be modified in various ranges. For example, in the above-described embodiment, as a means for converting continuous light into blinking light, a rotary disk type optical chopper is used, but for example, a reflective type having a rotating mirror, a liquid crystal cell, a car cell, etc. A shutter using an electro-optical effect or a shutter using a magneto-optical effect such as a Faraday effect or a magnetic Kerr effect may be used as a means for blinking illumination light. In this case as well, the flashing light may be flashed so that the illumination light is supplied to the electronic endoscope only during the CMOS global exposure period. The present invention can also be applied to an electronic endoscope system including an image sensor having a global exposure period other than CMOS, and in this case as well, the same effects as in the above embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Electronic endoscope system 10 Electronic endoscope 20 Processor 30 Monitor 104 CMOS image sensor 106 CMOS drive circuit 205 Light source part 251 Light source 252 Motor control part 253 Motor driver 254 Motor 255 Encoder 256 Rotary disk 257 Aperture control motor

Claims (2)

A CMOS image sensor for capturing an image in a body cavity;
A light source for supplying light for illuminating the body cavity;
Illumination light blinking means arranged on an optical path of illumination light supplied from the light source and periodically blinking the illumination light passing therethrough,
Intermediate timing signal generating means for generating an intermediate timing detection signal by detecting an intermediate timing between the timing of starting accumulation of the first line and the timing of starting accumulation of charge of the last line in the CMOS image sensor;
Control signal generating means for generating a control signal for controlling blinking of the illumination light so that the illumination light illuminates the body cavity only during a global exposure period in the CMOS image sensor;
Blinking control means for controlling the illumination light blinking means in accordance with the control signal;
With
The illumination light blinking means includes a turntable having an opening for allowing the illumination light supplied from the light source to pass therethrough and a light shielding part for shielding the illumination light supplied from the light source,
Said global exposure period, the charge of the first line from the charge accumulation is started in the last line is a period until the start of transfer,
The control signal generating means generates the control signal based on the intermediate timing detection signal ;
The endoscope system according to claim 1, wherein the blinking control unit controls the rotating disk so that a timing at which the illumination light is located at a center of the light shielding unit and an intermediate timing detection signal are synchronized . Further comprising an opening adjusting means for adjusting the size of the opening of the rotating disk;
The opening adjusting means, only the global exposure period in the CMOS image sensor, said as illumination light for illuminating the body cavity, and adjusting the opening angle of the opening in claim 1 The endoscope system described.

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