JP5006545B2 - Light source device - Google Patents

Description

  The present invention relates to a light source device, and more particularly, to a light source device provided in an electronic endoscope device.

  In general, an electronic endoscope apparatus includes a processor including a light source device for emitting illumination light for illuminating a body tissue as a subject, and charges accumulated by receiving reflected light from the illuminated subject. It is configured by a scope including an image sensor that forms a subject image. The illumination light from the light source device is irradiated to the subject from the distal end portion of the scope through a light guide inserted into the scope.

Depending on the method of reading the charge accumulated in the image sensor, it is necessary to provide a period during which the image sensor is shielded from light. For this reason, there is known an optical chopper for causing illumination light emitted from a light source to be incident on a light guide intermittently (for example, Patent Documents 1 and 2). The optical chopper is controlled to rotate at a predetermined rotational speed.
Japanese Patent No. 3398550 (see paragraphs [0019], [0024] to [0026], FIGS. 1 and 6 etc.) Japanese Patent Laid-Open No. 8-66357 (see paragraphs [0012], [0014], [0019] to [0021], FIG. 1 etc.)

  Conventionally, the rotation speed of the optical chopper has only been adjusted by a drive circuit or the like that has received a signal instructing the target speed, and whether or not the actual rotation speed matches the instructed target speed is Not done. Therefore, for example, when an error due to the motor driving the optical chopper has occurred, the rotational speed of the optical chopper may not be adjusted accurately.

  An object of this invention is to provide the light source device which can adjust the rotational speed of an optical chopper correctly.

  The light source device of the present invention is a light source device for an electronic endoscope device, and is provided with a light source that emits illumination light for illuminating a subject and a passage area so that the illumination light is allowed to pass intermittently. A light receiving chopper, a speed adjusting means for adjusting the rotating speed of the light chopper, and a light receiving part of the illumination light that has passed through the passing region in order to generate a timing signal indicating the actual rotation period of the light chopper. And the speed adjusting means adjusts the rotational speed of the optical chopper so that the actual rotational period indicated by the timing signal coincides with the target rotational period.

  The light source device preferably further includes signal generation means for generating a timing signal. In this case, it is more preferable that the light receiving element outputs an output signal indicating the amount of illumination light that has passed through the passage region, and the signal generating unit generates a timing signal as a pulse wave based on the output signal.

  It is desirable that the light source device further includes receiving means for receiving a target timing signal indicating the target rotation period. The light source device further includes a rotation cycle difference detection unit that detects a rotation cycle difference that is a difference between the actual rotation cycle of the optical chopper and the target rotation cycle, and the speed adjustment unit performs light emission based on the rotation cycle difference. It is desirable to adjust the rotation speed of the chopper.

  An electronic endoscope apparatus according to the present invention includes the light source device described above. The electronic endoscope apparatus preferably further includes an imaging device that receives reflected light of the illumination light from the subject and generates a video signal, and the target rotation cycle corresponds to the video signal readout cycle.

  ADVANTAGE OF THE INVENTION According to this invention, the light source device which can adjust the rotational speed of an optical chopper correctly can be implement | achieved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an electronic endoscope apparatus 10 in the present embodiment.

  The electronic endoscope apparatus 10 supplies a scope 20 used for imaging inside a body cavity of a patient, and a processor 30 that supplies illumination light for illuminating a subject to the scope 20 and processes a video signal sent from the scope 20. With. The scope 20 is detachably connected to the processor 30, and a monitor 60 is connected to the processor 30.

  The processor 30 is provided with a light source device 48 including a light source 32 incorporating a xenon lamp (not shown) that emits illumination light and a power source 34 for the light source, a system control circuit 50 that controls the entire processor 30, and the like. . The light source 32 emits illumination light when power is supplied from the light source power supply 34. The system control circuit 50 controls the amount of light emitted from the light source 32 and switching between turning on / off and the like by adjusting the amount of power supplied from the light source power source 34 to the light source 32.

  The light source device 48 is provided with a diaphragm 36, an optical chopper 40 for passing illumination light intermittently, and the like. The illumination light emitted from the light source 32 and passed through the diaphragm 36 and the light chopper 40 is collected by the condenser lens 35 and enters the incident end 12A of the light guide 12. The diaphragm 36 is opened and closed by a diaphragm motor 38 to adjust the amount of illumination light. The aperture control circuit 44 controls the aperture 36 by driving the aperture motor 38 based on the instruction signal from the system control circuit 50.

  In addition, the light source device 48 is provided with a light receiving element 26, a chopper controller 42, and a chopper motor 56 in order to control the rotation of the optical chopper 40. The light receiving element 26 receives a part of the illumination light that has passed through the condenser lens 35 and outputs a detection signal indicating a change in the amount of the received light to the chopper control unit 42. The chopper control unit 42 controls the chopper motor 56 so as to rotate the optical chopper 40 at a predetermined speed based on the detection signal transmitted from the light receiving element 26 and the like.

  The light guide 12 transmits the illumination light incident on the incident end 12A to the distal end portion of the scope 20 where the observation site is located. The illumination light that has passed through the light guide 12 is emitted from the emission end 12 </ b> B, and is irradiated toward the subject via the orientation lens 22. The light reflected from the observation site, which is an illuminated subject, passes through the objective lens 28 and reaches the CCD 24, which is a color imaging device provided with a color filter (not shown).

  The scope 20 is provided with a timing control circuit (not shown). The timing control circuit transmits a vertical synchronization signal to the image sensor driving circuit 54. The image sensor driving circuit 54 drives the CCD 24 based on the vertical synchronization signal under the control of the system control circuit 50.

  In the CCD 24, a video signal of a subject image corresponding to the color of light passing through the color filter is generated by photoelectric conversion. Here, the NTSC system is applied as the color television system, and the signal charges of the odd-numbered line and the even-numbered line of the CCD 24 are sequentially read out by one field period, that is, at intervals of 1/60 seconds under the control of the image sensor driving circuit 54. All charges are read every frame period.

  Note that the vertical synchronization signal transmitted to the image sensor driving circuit 54 is also transmitted to the chopper controller 42. As will be described later, the chopper control unit 42 controls the chopper motor 56 based on the vertical synchronization signal (target timing signal) in addition to the signal output from the light receiving element 26 and adjusts the rotation speed of the optical chopper 40. .

  The read video signal is subjected to various processes such as an amplification process, a conversion process from an analog video signal to a digital video signal, and a white balance adjustment to generate a luminance signal and a color difference signal. The luminance signal and the color difference signal are sent to the video signal processing circuit 46 of the processor 30, converted into a video signal such as an NTSC signal, and output to the monitor 60. As a result, the subject image is displayed on the monitor 60.

  FIG. 2 is a diagram showing the optical chopper 40. FIG. 3 is a diagram schematically showing a state in which the illumination light emitted from the light source 32 is received by the light receiving element 26. FIG. 4 is a diagram schematically showing rotation control of the optical chopper 40 by the chopper controller 42.

  The light chopper 40 is a thin disk-shaped light shielding member, and the light chopper 40 is provided with a pair of openings M (passage regions) through which a part of illumination light passes. The shape of the opening M is a part of the ring centering on the center point C of the optical chopper 40, and the shape of the pair of openings M is equal to each other. Further, the shape of the pair of shielding regions S that are located between the pair of openings M and form a part of the same ring is also substantially equal to the shape of the openings M.

  The optical chopper 40 is rotated by a chopper motor 56 as indicated by an arrow A about an axis passing through the center point C and parallel to the optical path of the illumination light. The light chopper 40 is disposed so that a part of the illumination light is irradiated on the optical chopper 40 through a certain optical path, and the irradiated illumination light passes through the opening M or is shielded by the shielding region S. .

  As is clear from the above, even when the amount of illumination light emitted from the light source 32 is constant, the amount of illumination light passing through the opening M varies with the rotation of the light chopper 40. That is, when the light chopper 40 is at a rotation position where the optical path of the illumination light toward the light chopper 40 overlaps the opening M, the amount of illumination light passing through the light chopper 40 is maximum (see FIG. 3). When the light chopper 40 is in a rotational position where the optical path of the illumination light is blocked by the shielding region S, the illumination light does not pass through the light chopper 40. When the optical path of the illumination light overlaps the area including the boundary line B between the opening M and the shielding area S, the amount of illumination light passing through the opening M is less than the maximum amount.

  The illumination light that has passed through the opening M is received by the light receiving element 26. The light receiving element 26 outputs a signal having an intensity corresponding to the amount of received illumination light. Therefore, the intensity of the signal output from the light receiving element 26 changes between the maximum value MAX and the minimum value MIN as shown schematically in FIG. 3, and the time for the maximum value MAX or the minimum value MIN is long. On the other hand, it changes between the maximum value MAX and the minimum value MIN in a relatively short time. This is because the time when the optical path of the illumination light overlaps with the region including the boundary line B is shorter than the time when only the opening M or the shielding region S overlaps.

  A signal indicating the amount of illumination light output by the light receiving element 26 is received by a buffer 62 (signal generating means) provided in the chopper control unit 42 (see FIG. 4). As will be described later, the buffer 62 generates a pulse signal (timing signal) having a waveform similar to the waveform of the received signal and indicating the actual rotation period of the optical chopper 40 based on the received signal. The pulse signal generated in the buffer 62 is transmitted to the comparison operation circuit 66.

  On the other hand, the vertical synchronization signal transmitted from the timing control circuit to the chopper control unit 42 via the image sensor driving circuit 54 is received by the comparison operation circuit 66 (receiving means) provided in the chopper control unit 42. The vertical synchronization signal originally indicates a signal charge read cycle in the CCD 24. The period in which the signal charges accumulated in the CCD 24 are read out corresponds to the time during which the illumination light is emitted to the subject, that is, the rotation period of the light chopper 40. Therefore, the vertical synchronization signal also indicates the target value of the rotation period of the optical chopper 40.

  Here, as will be described later, it is necessary to repeat the emission and stop of the illumination light every one field period, that is, every 1/60 seconds. Therefore, the pair of openings M and the pair of shielding regions S each pass illumination light during one rotation, and the light chopper 40 that shields needs to rotate once in 1/15 seconds. That is, the target value of the rotation period of the optical chopper 40 indicated by the vertical synchronization signal is 1/15 seconds.

  The comparison operation circuit 66 detects a rotation period difference that is a difference between the actual rotation period of the optical chopper 40 indicated by the pulse signal generated by the buffer 62 and the target value. The chopper control circuit 64 controls the chopper motor 56 based on the rotation period difference. In other words, the chopper control circuit 64 instructs the chopper motor 56 to rotate the optical chopper 40 that rotates exactly once in 1/15 seconds at the same rotation speed when there is no rotation period difference. Send a signal.

  On the other hand, if a rotation cycle difference has occurred, the chopper control circuit 64 provides an instruction signal for adjusting the chopper so as to cancel the rotation cycle difference, that is, so that the optical chopper 40 makes one rotation in 1/15 seconds. Send to motor 56. As a result, the optical chopper 40 is rotated at a constant speed so as to ensure that the actual rotation period coincides with the target rotation period indicated by the vertical synchronization signal.

  FIG. 5 is a timing chart showing the timing of illumination light emission and video signal readout.

The CCD 24 is exposed in the emission period L ₁ of the illumination light to the subject, and the video signal generated in the odd line is read out in the next odd field period T ₁ . In the odd field period T ₁ , since the illumination light is shielded by the light chopper 40, the odd field period T ₁ is equal to the illumination light emission stop period L ₂ . In the subsequent even field period T ₂ , the video signal generated in the even line by the exposure of the CCD 24 in the emission period L ₁ is read, and the illumination light is emitted again to the subject.

  As described above, the pulse signal (solid line) indicating the actual rotation period of the optical chopper 40 is the output signal from the light receiving element 26 (solid line connecting between the broken line and the broken line) indicating the amount of illumination light received by the light receiving element 26. ). Here, during the period in which the intensity of the output signal is the minimum value MIN, since the illumination light is not emitted to the subject, the intensity of the generated pulse signal is also the minimum value MIN. On the other hand, during the period when the intensity of the output signal from the light receiving element 26 is not the minimum value MIN, the intensity of the pulse signal is set to the maximum value MAX because the illumination light is emitted to the subject although the amount of light changes.

In this way, by generating the pulse signal as a square wave having only the maximum value MAX or the minimum value MIN, the pulse signal is output from the actual rotation period of the optical chopper 40, that is, the emission period L corresponding to the maximum value MAX. ₁ and the emission stop period L ₂ corresponding to the minimum value MIN are shown. Then, the rotation period, that is, the rotation speed of the optical chopper 40 is controlled by the chopper so that the emission period L ₁ and the emission stop period L ₂ indicated by the pulse signal coincide with one field period which is the reception interval of the vertical synchronization signal. Adjusted by circuit 64.

  As described above, in the light source device 48 of the present embodiment, the actual rotation period of the light chopper 40 detected based on the change in the intensity of the illumination light that has passed through the light chopper 40 is accurate with the target rotation period. So that the rotation speed of the optical chopper 40 can be adjusted.

  The shape of the optical chopper 40 is not limited to this embodiment, and the rotational speed of the optical chopper 40 is adjusted according to the shape. For example, the optical chopper 40 may have a semicircular shape including one shielding region S and one passing region that is substantially the same shape as the shielding region S. In this case, the rotation period is, for example, 1/30 seconds. It is.

  The imaging device and the like are not limited to the present embodiment, and for example, a color CCD may be adopted instead of the CCD 24 that is a monochrome CCD. In this case, a color filter is unnecessary. In addition, as long as the electronic endoscope apparatus switches the emission of illumination light to the subject and the emission stop by the light chopper 40, the video signal readout method and the like are limited to the electronic endoscope apparatus 10 of the present embodiment. Not.

It is a block diagram of the electronic endoscope apparatus in this embodiment. It is a figure which shows an optical chopper. It is a figure which shows roughly the state by which the illumination light radiate | emitted from the light source is received by the light receiving element. It is a figure which shows roughly the rotation control of the optical chopper by a chopper control part. It is a timing chart which shows the timing of emission of illumination light and reading of a video signal.

Explanation of symbols

10 Electronic endoscope device 24 CCD (imaging device)
26 Light-receiving element 32 Light source 40 Optical chopper 42 Chopper controller (speed adjusting means / signal generating means / receiving means)
48 light source device 64 chopper control circuit (speed adjusting means)
66 Comparison operation circuit (rotation period difference detecting means / receiving means)
M opening (passage area)

Claims (3)

A light source that emits illumination light for illuminating a subject;
A passage area and a shielding area for the illumination light are provided, and the illumination light is intermittently passed through an emission period in which the illumination light passes through the passage area and an emission stop period in which the illumination light is shielded by the shielding area. A rotating light chopper,
Speed adjusting means for adjusting the rotational speed of the light chopper;
In order to generate a timing signal indicating an actual rotation period of the light chopper, an output signal indicating a part of the illumination light that has passed through the passage area and an amount of the illumination light that has passed through the passage area is generated. A light receiving element for output;
Signal generating means for generating the timing signal as a square-wave pulse signal having only a maximum value or a minimum value based on the output signal;
Receiving means for receiving a target timing signal indicating the target rotation period;
A rotation period difference detecting means for detecting a rotation period difference that is a difference between an actual rotation period of the optical chopper and the target rotation period;
The speed adjusting means adjusts the rotation speed of the optical chopper based on the rotation period difference so that an actual rotation period indicated by the timing signal matches a target rotation period ,
The rotation speed of the light chopper is adjusted such that the intensity of the output signal when the optical path of the illumination light overlaps the area including the boundary line between the passage area and the shielding area of the light chopper is the maximum intensity. By adjusting to be equal to each other, the emission period corresponding to the maximum value and the emission stop period corresponding to the minimum value are both made to coincide with the reception interval of the target timing signal. A light source device for an electronic endoscope apparatus.   An electronic endoscope apparatus comprising the light source device according to claim 1.   The imaging device according to claim 2, further comprising an imaging device that receives reflected light of the illumination light from a subject and generates a video signal, and the target rotation period corresponds to a read period of the video signal. Electronic endoscope device.

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