JP4745850B2 - Electronic endoscope device - Google Patents

Description

  The present invention relates to an electronic endoscope apparatus capable of adjusting the brightness of a subject image, and more particularly to an automatic light control process using a rotary shutter.

  In an endoscope apparatus, automatic dimming is possible using a dimming mechanism such as a diaphragm or an electronic shutter function, and the subject image displayed on the monitor is maintained at an appropriate brightness. The amount of illumination light applied to the light source is adjusted, or the charge accumulation time of the image sensor is adjusted.

In a dimming mechanism including a rotary shutter, two rotary shutters, each having a light transmission portion and a light shielding portion formed along the circumferential direction, rotate, and a transmission region where the transmission portions overlap and other light shielding portions Alternately pass (cross) the light path of the illumination light, so that the subject is intermittently illuminated, and the charges accumulated in the imaging device that receives the reflected light from the illuminated subject are sequentially read out. In order to adjust the brightness of the subject image, the relative rotational phase difference between the two rotary shutters is changed, and the amount of illumination light is adjusted by changing the circumferential length of the light transmission region (Patent Document). 1).
JP 2002-119464 A

  When two rotary shutters are used, the configuration of the light control mechanism is complicated, and relative phase control of the two rotary shutters rotating at the same time is performed, so that high-precision automatic light control processing is difficult.

  In addition, when the rotary shutter is continuously rotated, the rotation speed fluctuates irregularly due to mechanical vibration of a motor or the like, and jitter occurs with respect to the image signal. Specifically, a difference occurs between the brightness of the image by the first frame / field and the brightness of the image by the second frame / field. As a result, the image continues to be bright and dark, and an unstable image flickering with respect to the brightness is generated. It will be displayed.

  The electronic endoscope apparatus according to the present invention is an electronic endoscope apparatus including a video scope having an image sensor, and the brightness of which can be adjusted with a single rotary shutter. The electronic endoscope apparatus includes a light source that illuminates a subject, a luminance signal detection unit that detects a luminance signal corresponding to the subject image based on an image signal read from the image sensor, and a charge accumulation time for reading the image signal. Charge accumulation time adjusting means for outputting a charge sweeping pulse to the image sensor within one frame or one field period.

  In the present invention, one rotary shutter having a transmission part that transmits illumination light from a light source and a light shielding part that blocks illumination light is provided, and the light shielding part and the transmission part of the rotary shutter have illumination light. It is arranged so as to pass through (pass across) the optical paths in order and rotate. In the transmissive portion, for example, an opening may be formed by a semicircle along the circumferential direction. The electronic endoscope apparatus according to the present invention includes a rotary shutter control unit that controls the rotation of the rotary shutter. The rotary shutter control unit synchronizes the rotation of the rotary shutter with one frame or one field period, and rotates the rotary shutter so that at least a part of the illumination period is included in the charge accumulation time for reading image signals. Here, the illumination period represents a period during which the transmission part crosses the optical path of the illumination light. For example, the illumination period may be made to coincide with the charge accumulation time from one charge discharge pulse to one frame or one field period.

  The rotary shutter may be configured according to an imaging method or the like. For example, in the case of a single plate simultaneous type, as a configuration of a rotary shutter that is rotated half a time in accordance with one field period, a transmission portion is formed along the circumferential direction by a semicircle. Alternatively, as a configuration of the rotary shutter that is rotated halfway in accordance with one field period, a pair of transmission portions are formed along the circumferential direction of the opposing quadrant circles.

  The rotary shutter control means of the present invention shifts the rotational phase by changing the rotational speed of the rotary shutter so as to maintain the brightness of the subject image at an appropriate brightness according to the detected luminance signal. If the subject image is too bright, the phase of the rotary shutter is shifted forward or backward in time series so as to shorten the illumination period within the charge accumulation time for reading image signals. On the other hand, when the subject image is dark, the phase of the rotary shutter is shifted so as to shorten the illumination period within the charge accumulation time for reading image signals. Although part of the illumination period overlaps with the next or previous one field or one frame period due to the phase shift, the charge discharge pulse does not affect the image signal readout. In this case, the electrification / accumulation time adjusting means does not output a charge discharge pulse for the purpose of adjusting the amount of light, but performs a function of discharging accumulated charge unnecessary for image signal reading by a phase shift of the rotary shutter. Automatic dimming processing is executed by rotation control of one rotary shutter using the output of such charge discharge pulses.

  Furthermore, the transmission part of the present invention has an opening that is formed along the circumferential direction and whose width along the radial direction becomes asymptotically small along the rotation direction. With such a shape of the transmissive portion, the amount of light reaching the first stage after the portion passing through the optical path is switched from the light shielding portion to the transmissive portion is small, and the amount of light gradually increases as it rotates. Therefore, even if jitter occurs, the average light quantity change is small, and the influence on the image can be suppressed. However, it is assumed that jitter occurs within a range in which the width changes along the radial direction.

  An automatic light control device for an electronic endoscope according to the present invention includes a luminance signal detecting means for detecting a luminance signal corresponding to a subject image based on an image signal read from an image sensor provided in a video scope, and an image signal reading Charge storage time adjusting means for outputting a charge sweep pulse to the image sensor within one frame or one field period in accordance with the charge storage time for use, a transmission part for transmitting illumination light from the light source, and a light shielding part for blocking illumination light A single rotary shutter that rotates so that the light shielding portion and the transmission portion sequentially traverse the optical path of the illumination light, and the rotation of the rotary shutter is synchronized with one frame or one field period, and the transmission The rotary shutter so that at least a part of the illumination period in which the section crosses the optical path of the illumination light is included in the charge accumulation time for image signal readout. A rotary shutter control unit that rotates the rotary shutter, and the rotary shutter control unit rotates at a rotation speed of the rotary shutter so as to maintain the brightness of the subject image at an appropriate brightness according to the detected luminance signal. The phase is shifted, and the transmission part is formed along the circumferential direction, and the width along the radial direction is asymptotically reduced along the rotation direction.

  According to the present invention, high-precision automatic light control processing can be executed with a simple rotary shutter configuration, and an image with stable brightness can be obtained even in imaging using the rotary shutter. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of an electronic endoscope apparatus according to the first embodiment.

  The electronic endoscope apparatus includes a video scope 10 and a processor 20, and the video scope 10 is detachably connected to the processor 20. A monitor 60 is connected to the processor 20.

  When the lamp power supply 22 of the processor 20 is turned on, power is supplied from the lamp power supply 22 to a lamp 24 having a discharge tube such as a xenon lamp, and illumination light is emitted from the lamp 24. The emitted light enters the incident end 12A of the light guide 12 in the video scope 10 via the condenser lens 26A. The light guide 12 transmits light from the lamp 24 to the distal end of the scope, and illumination light emitted from the light guide 12 irradiates the subject via the light distribution lens 14.

  The light reflected at the observation site irradiated with the illumination light reaches the CCD 18 through the objective lens 16, whereby a subject image is formed on the light receiving surface of the CCD 18. In the CCD 18 provided with the color filter on the light receiving surface, image signals corresponding to the subject image are read at predetermined time intervals, and the read image signals are sent to the video signal processing circuit 26 of the processor 20. The CCD 18 is driven by a CCD driver 28, and here, image signals for one field are read at 1/60 second intervals in accordance with the NTSC system. The CCD 18 is an interline type CCD, and an image signal is read out according to a single-plate simultaneous type.

  In the video signal processing circuit 26, various processes such as white balance processing and γ correction are performed on the image signal to generate a video signal such as an NTSC signal. The video signal is output to the monitor 60, whereby the observation image is displayed on the monitor 60. Also, a luminance signal is generated in the video signal processing circuit 26 and is sequentially sent to the dimming circuit 36 at intervals of one field. A system control circuit 29 including a CPU, ROM, and RAM can control the operation of the processor 20, output a control signal to each circuit in the processor, and control the lamp power supply 22 to adjust the output of the lamp 24. is there.

  A rotary shutter 32 is provided between the lamp 24 and the condenser lens 26A, and is rotated by a motor 34 to which an encoder (not shown here) is attached. The motor 34 is a stepping motor and rotates in accordance with a pulse signal sent from the dimming circuit 36. The light control circuit 36 controls the rotation of the motor 34, that is, the rotation of the rotary shutter 32, based on the luminance signal sent from the video signal processing circuit 26, and here is constituted by a DSP (Digital Signal Processor). Yes. In the present embodiment, the phase of rotation of the rotary shutter 32 is controlled by the dimming circuit 36 in order to maintain the subject image displayed on the monitor 60 with appropriate brightness.

  The timing controller 30 outputs a clock pulse signal so that the rotation of the rotary shutter 32 and the image signal reading operation by the CCD driver 28 are synchronized. The front panel of the processor 20 is provided with a reference luminance level switch 38 for setting the brightness of the subject image, and the dimming circuit 36 is based on the difference between the luminance level of the detected luminance signal and the reference luminance level. To perform automatic dimming.

  FIG. 2 is a plan view of the rotary shutter 32.

  As shown in FIG. 2, the rotary shutter 32 is a disk-shaped light amount adjusting member that rotates about the axis C, and an arc-shaped transmission portion 32 </ b> A is formed along the circumferential direction by a length corresponding to a semicircle. The transmission part 32A is formed as an opening, and allows light traveling from the lamp 24 to the incident end 12A of the light guide 12 to pass therethrough. The light shielding parts 32B other than the transmission part 32A shield the light from the lamp 24. In addition, the transmission portion 32A has a circumferential width W that gradually decreases along the rotation direction RR.

  The rotary shutter 32 is disposed so that the optical path of the light beam LB of the light emitted from the lamp 24 is close to the outer edge of the rotary shutter 32, and a transmissive portion 32A and a light shielding portion 32B that transmit light by rotating the rotary shutter 32. And sequentially pass (cross) the optical path of the light beam LB. Here, the rotary shutter 32 makes one rotation in one field period, and makes one rotation (two rotations) every 1/60 seconds (every 1/30 seconds) according to the NTSC system.

  FIG. 3 is a diagram showing a timing chart of automatic light control processing.

  The one-field period C0 is divided into an illumination period C in which the transmission part 32A of the rotary shutter 32 passes through the optical path of the light beam LB and a light-shielding period C1 in which the light shielding part 32B passes through the light beam LB. Reaches the CCD 18. The CCD driver 28 outputs a charge sweeping pulse signal K within one field period, and the output of the pulse signal K follows the illumination period C. As a result, the charge accumulated in the period B before the output of the pulse signal K is discarded, and the charge accumulated by the illumination light during the period A is transferred in the next field period and read out as an image signal. In a state where the illumination period C during which the transmission part 32A passes through the light beam LB coincides with the charge accumulation time A for reading the image signal, the entire illumination light amount obtained over the illumination period C is used for image signal generation.

  Based on the difference between the predetermined reference luminance level and the luminance level of the detected luminance signal for one field, it is determined whether the brightness of the subject image is appropriate. Then, when there is a luminance difference, the phase of the rotary shutter 32 is controlled. Here, the phase of the rotary shutter 32 represents the rotation angle of the rotary shutter 32 when one field period is used as a reference, the start time of the passage of the light beam LB of the light shielding unit 32B is set as a reference angle, and the rotary shutter 32 is based on the reference angle. The phase of is determined.

  When the brightness of the subject image exceeds the appropriate brightness, that is, when the detected brightness level is larger than the reference brightness level, the phase of the rotary shutter 32 is shifted so as to reduce the amount of illumination light. Here, the rotational speed of the rotary shutter 32 is temporarily reduced, and the phase of the rotary shutter 32 is shifted by a period CS corresponding to the luminance difference. Since the motor 34 is a stepping motor, the rotational speed of the rotary shutter 32 is temporarily reduced by temporarily reducing the pulse period output to the motor 34.

  Due to the phase shift, as shown in FIG. 3, only a partial period C ′ of the illumination period C is accommodated in the charge accumulation period A for reading the image signal in one field period, and the shifted period CS is before the output of the charge discharge pulse K. It belongs to period B. As a result, the illumination period in the image signal generation period decreases, the charge accumulation amount in the image signal generation period decreases, and the brightness of the subject image changes to an appropriate brightness. On the other hand, when the brightness of the subject image decreases, the rotational speed of the rotary shutter 32 is temporarily increased so as to increase the illumination period in the image signal generation period, thereby shifting the rotational phase of the rotary shutter 32 by a predetermined amount. Is done. When the rotational speed is temporarily increased, the pulse period output to the motor 34 is temporarily increased.

  Since the transmission part 32A of the rotary shutter 32 has a shape as shown in FIG. 2, the light quantity gradually increases in the initial stage M of the light reaching the CCD 18, and then becomes constant. Therefore, even when jitter is caused by the phase control of the rotary shutter 32 and the light quantity increase line N1 is shifted to the increase line N2 indicated by the broken line, the light quantity fluctuation delta L caused by the jitter is minute.

  FIG. 4 is a control block diagram of automatic light control processing.

  The control system for automatic dimming processing includes a phase compensator T1, an amplifier T2, a speed detector T3, and a driver T4. In the luminance phase conversion unit T5, a signal obtained by adding a signal representing a preset reference luminance level and a signal representing the luminance level of the detected subject image is input, and the difference is the rotational phase shift amount of the rotary shutter 32. Is converted into a signal representing.

  The signal representing the rotational phase shift amount is added to the detected rotational phase signal of the rotary shutter 32 sent from the encoder 33, and is input to the phase compensator T1 together with the synchronization signal sent from the timing controller 30. . A speed signal for increasing / decreasing the rotational speed of the rotary shutter 32 is output from the phase compensator T1 based on the phase shift amount. The speed signal is added to the detection speed signal output from the encoder 33 via the amplifier T2, and input to the drive unit T4.

  When input to the drive unit T4, a pulse signal that is a drive signal is output to the motor. The encoder 33 coaxially attached to the motor 34 detects the rotational speed and rotational phase of the motor 34, outputs a pulse signal for phase detection every time it rotates, and a series of pulses for rotational speed detection. Output a signal. The rotational speed signal for detection detected from the speed detection unit T3 is fed back and added to the control signal output from the amplifier T2, that is, the speed signal, and input to the drive unit T4. The rotation speed is controlled by such feedback control. In addition, the phase signal output from the encoder 33 is fed back and input to the phase compensator T1 together with the rotational phase shift amount from the luminance phase converter T5, whereby the phase of the rotary shutter 32 is controlled.

  As described above, according to the first embodiment, the single rotary shutter 32 is disposed between the lamp 24 and the light guide 12, and the transmission part 32A and the light shielding part 32B of the rotary shutter 32 sequentially pass the optical path of the light beam LB. In order to pass, it rotates in synchronization with one field period. Then, the rotational phase of the rotary shutter 32 is shift-controlled so that the brightness of the subject image is maintained at an appropriate brightness. Further, the shape of the transmission part 32A is determined so that the width of the transmission part 32A along the radial direction is asymptotically reduced along the rotation direction. As a result, the increase in the amount of light after the transmission part 32A begins to pass light is moderated, and the variation in the amount of light due to the overall jitter is small, and the influence of the jitter on the display image and automatic light control processing is suppressed.

  The length along the circumferential direction of the transmissive portion may be determined according to the charge accumulation time for reading the image signal. Further, the configurations of the transmissive portion and the light shielding portion may be configurations other than those of the first and second embodiments. The rotary shutter may be rotated once or half in accordance with one frame period, and the transmission part and the light shielding part may be regularly formed in accordance with this. The rotational phase of the rotary shutter can be controlled by either shift control in front or back in time series. A motor other than the stepping motor may be used as the motor that drives the rotary shutter. A method other than the embodiment may be applied to the charge transfer method and the imaging method of the CCD.

It is a block diagram of the electronic endoscope apparatus which is 1st Embodiment. It is a top view of a rotary shutter. It is the figure which showed the timing chart of an automatic light control process. It is a control block diagram of automatic light control processing.

Explanation of symbols

10 Videoscope 18 CCD (Image sensor)
20 processor 22 lamp power supply 24 lamp (light source)
26 Video signal processing circuit 28 CCD driver 29 System control circuit 30 Timing controller 32 Rotary shutter 34 Motor 36 Light control circuit

Claims (4)

An electronic endoscope apparatus including a video scope having an image sensor,
A light source that illuminates the subject;
Luminance signal detection means for detecting a luminance signal indicating the brightness of the subject image based on the image signal read from the image sensor;
Charge accumulation time adjusting means for outputting a charge sweep pulse to the image sensor within one frame or one field period in accordance with the charge accumulation time for reading image signals;
A rotary shutter that includes a transmission unit that transmits illumination light from the light source and a light-blocking unit that blocks illumination light, and the light-blocking unit and the transmission unit sequentially rotate so as to cross the optical path of the illumination light; ,
The rotary shutter is synchronized with one frame or one field period, and at least a part of the illumination period in which the transmission section crosses the optical path of the illumination light is included in the charge accumulation time for image signal readout. A rotary shutter control means for rotating the shutter,
The rotary shutter control means shifts the rotational phase by changing the rotational speed of the rotary shutter so that the brightness of the subject image is maintained at an appropriate brightness according to the detected luminance signal,
An electronic endoscope apparatus, wherein the transmission part is formed along a circumferential direction, and a width along a radial direction is asymptotically reduced along a rotation direction.   2. The transmission part according to claim 1, wherein the transmission part has an opening formed by a semicircle along a circumferential direction, and the rotary shutter control unit rotates the rotary shutter once in one field period. The electronic endoscope apparatus described. A videoscope having an image sensor is connected,
A light source that illuminates the subject;
Luminance signal detection means for detecting a luminance signal according to the subject image based on the image signal read from the image sensor;
Charge accumulation time adjusting means for outputting a charge sweep pulse to the image sensor within one frame or one field period in accordance with the charge accumulation time for reading image signals;
A rotary shutter that includes a transmission part that transmits illumination light from the light source and a light shielding part that blocks illumination light, and the light shielding part and the transmission part rotate so as to traverse the optical path of the illumination light in order; ,
The rotary shutter is synchronized with one frame or one field period, and at least a part of the illumination period in which the transmission section crosses the optical path of the illumination light is included in the charge accumulation time for image signal readout. A rotary shutter control means for rotating the shutter,
The rotary shutter control means shifts the rotational phase by changing the rotational speed of the rotary shutter so that the brightness of the subject image is maintained at an appropriate brightness according to the detected luminance signal,
The processor of the electronic endoscope apparatus, wherein the transmission portion is formed along a circumferential direction, and a width along a radial direction is asymptotically reduced along a rotation direction. A luminance signal detecting means for detecting a luminance signal corresponding to the subject image based on an image signal read from an image sensor provided in the video scope;
Charge accumulation time adjusting means for outputting a charge sweep pulse to the image sensor within one frame or one field period in accordance with the charge accumulation time for reading image signals;
A rotary shutter that has a transmission part that transmits illumination light from the light source and a light shielding part that blocks illumination light, and that rotates so that the light shielding part and the transmission part sequentially traverse the optical path of the illumination light;
The rotary shutter is synchronized with one frame or one field period, and at least a part of the illumination period in which the transmission section crosses the optical path of the illumination light is included in the charge accumulation time for image signal readout. A rotary shutter control means for rotating the shutter,
The rotary shutter control means shifts the rotational phase by changing the rotational speed of the rotary shutter so that the brightness of the subject image is maintained at an appropriate brightness according to the detected luminance signal,
An automatic dimming device for an electronic endoscope, wherein the transmission part is formed along a circumferential direction, and a width along a radial direction is asymptotically reduced along a rotation direction.

Images