JP2011024885A - Light source system for endoscope, and endoscope unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a high luminance image signal and a low luminance image signal. <P>SOLUTION: An imaging device is controlled so as to alternately repeat a light-receiving period and a blanking period. The imaging device accumulates signal charges according to an amount of light received in the light receiving period. The imaging device outputs the signal charges accumulated in the light receiving period right before a blanking period. An LED is controlled so as to emit illumination light in first and second light emitting periods within each light receiving period. The length of the first light emitting period is determined so as to be longer than the second light emitting period. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an endoscope light source system that enables an image sensor to generate a high-luminance image signal photographed with a high exposure value and a low-luminance image signal photographed with a low exposure value.

  There has been proposed an endoscope apparatus that creates an image with an expanded dynamic range so that a bright part to a dark part of a subject are clearly displayed (see Patent Document 1). In order to create an HDR (High Dynamic Range) image that is an image with an expanded dynamic range, a high-intensity image signal corresponding to an image of the same subject taken with a higher exposure value and an image taken with a lower exposure value And a low-luminance image signal corresponding to.

  Conventionally, a high-intensity image signal and / or a low-intensity image signal has been generated by performing image processing on a single image signal. However, when a high-intensity image signal and / or a low-intensity image signal is generated by image processing, there is a problem that noise increases.

  Further, by using an electronic shutter, an image signal is generated by lengthening the charge accumulation period during one of consecutive frame periods, and an image signal is generated by shortening the charge accumulation period during the other period. It is also known.

  However, when an electronic shutter is used, it is impossible to adjust the charge accumulation time. Since problems due to the inability to adjust the charge accumulation time may occur, it has been required to generate a high luminance image signal and a low luminance image signal by another method.

Japanese Patent Laid-Open No. 11-313247

  Therefore, an object of the present invention is to provide an endoscope light source system that can generate a high luminance image signal and a low luminance image signal without using an electronic shutter.

  An endoscope light source system according to the present invention irradiates a subject in an endoscope unit having an image sensor that generates an image signal corresponding to an optical image of a subject received during a continuous light receiving period with a blanking period interposed therebetween. An endoscope light source system for supplying irradiation light, wherein the irradiation light is emitted only during a first light emission period shorter than the light reception period during the first light reception period of the light source and the image sensor. An emission period control unit that emits irradiation light for a second emission period that is shorter than the first light reception period and different in length from the first emission period during a second light reception period after one light reception period; It is characterized by that.

  The image sensor further includes a first input unit that detects a still image shooting command input that is a command for shooting a still image, and an emission period control unit that detects when the first input unit detects the still image shooting command input. It is preferable to control the emission timing of the irradiation light so that the end timing of the first emission period is close to the start timing of the second emission period.

  In addition, a second input unit that detects a period change command input that is a command for changing the first and second emission periods is provided, and an emission period control unit when the second input unit detects a period change command input It is preferable to change the first and second emission periods.

  In addition, the emission period control unit alternately repeats the first and second emission periods for emitting the emitted light for each successive light receiving period with the blanking period in between and the center of the first and second emission periods. It is preferable to control the irradiation timing of the irradiation light so that the interval is kept constant.

  The emission period control unit preferably adjusts the emission period of the irradiation light by causing the light source to change the emission period of the irradiation light. Alternatively, the emission period control unit preferably adjusts the emission period of the irradiation light by adjusting the light shielding period of the irradiation light.

  In addition, the endoscope unit of the present invention includes an imaging element that generates an image signal corresponding to an optical image of a subject that is received during a continuous light receiving period with a blanking period interposed therebetween, and irradiation light that is light that irradiates the subject The light source emits light, and the irradiation light is emitted during the first light receiving period shorter than the light receiving period during the first light receiving period of the image sensor, and the first light receiving period after the first light receiving period is the first light receiving period. And an emission period control unit that emits irradiation light for a second emission period that is shorter than the first light emission period and different in length from the first emission period.

  According to the present invention, the substantial exposure time is adjusted by adjusting the emission period of the irradiation light with which the subject is irradiated. By adjusting the substantial exposure time, a high luminance image signal and a low luminance image signal can be generated.

1 is a block diagram schematically showing an internal configuration of an endoscope unit including an endoscope processor having an endoscope light source system to which an embodiment of the present invention is applied. FIG. It is a timing chart for demonstrating the production | generation time of the image signal in the normal image display mode, and the light emission time of illumination light. It is a timing chart for demonstrating the production | generation time of the image signal in the HDR image display mode, and the light emission time of illumination light. 6 is a timing chart for explaining the emission timing of illumination light when a still image observation command is input in the HDR image display mode. It is a timing chart for demonstrating the accumulation | storage time of the signal charge at the time of using an electronic shutter.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram schematically showing an internal configuration of an endoscope unit including an endoscope processor having an endoscope light source system to which an embodiment of the present invention is applied.

  The endoscope unit 10 includes an endoscope processor 20, an electronic endoscope 30, and a monitor 11. The endoscope processor 20 is connected to the electronic endoscope 30 and the monitor 11.

  Illumination light for illuminating the subject is supplied from the endoscope processor 20 to the electronic endoscope 30. The subject irradiated with the illumination light is imaged by the electronic endoscope 30. An image signal generated by imaging of the electronic endoscope 30 is sent to the endoscope processor 20.

  In the endoscope processor 20, predetermined signal processing is performed on the image signal obtained from the electronic endoscope 30. The image signal subjected to the predetermined signal processing is transmitted to the monitor 11, and an image corresponding to the transmitted image signal is displayed on the monitor 11.

  The endoscope processor 20 includes a light source system 21, a timing controller 22, a processor image processing unit 23, a system controller 24, an input unit 25, and the like.

  The light source system 21 has an LED (not shown) as a light source, and illumination light is emitted from the LED to the subject. As will be described later, the timing at which the LEDs emit illumination light is controlled by the timing controller 22.

  The processor image processing unit 23 performs predetermined signal processing on the image signal. The timing controller 22 controls the operation timing of each part of the endoscope unit 10 including the above-described control of the light emission timing. The operation of each part of the endoscope unit 10 is controlled by the system controller 24. The system controller 24 causes the endoscope unit 10 to execute various operations in accordance with commands input to the input unit 25.

  When the endoscope processor 20 and the electronic endoscope 30 are connected, the light source system 21 and the light guide 31 provided in the electronic endoscope 30 are optically connected. In addition, when the endoscope processor 20 and the electronic endoscope 30 are connected, an image sensor 32, an endoscope image processing unit 33, an endoscope memory 34, a timing controller 22, The processor image processing unit 23 and the system controller 24 are electrically connected.

  The electronic endoscope 30 is provided with a light guide 31, an image sensor 32, an endoscope image processing unit 33, an endoscope memory 34, and the like. The light guide 31 extends from the connector 35 connected to the endoscope processor 20 to the distal end of the insertion tube 36.

  Illumination light emitted from the light source system 21 enters the incident end of the light guide 31. The illumination light incident on the incident end is transmitted to the exit end. The illumination light transmitted to the emission end is irradiated to the subject in the distal direction of the insertion tube 36.

  The image sensor 32 is controlled by the timing controller 22 and is driven so as to generate an image signal at a constant cycle, for example, every 1/60 seconds.

  An optical image of the reflected light of the subject irradiated with the illumination light reaches the light receiving surface of the image sensor 32. The image sensor 32 is, for example, a CCD. As described above, based on the control of the timing controller 22, an image signal corresponding to the optical image reaching the light receiving surface is generated by the imaging element 32 at a constant period.

  The generated image signal is transmitted to an endoscope image processing unit 33 provided in the connector 35. In the endoscope image processing unit 33, predetermined signal processing such as correlated double sampling processing and A / D conversion processing is performed on the image signal. The image signal that has undergone the predetermined signal processing is transmitted to the processor image processing unit 23.

  Note that the endoscope memory 34 stores data such as the type of the electronic endoscope 30, a necessary light amount, and a blanking period. These data are read out to the system controller 24 when the electronic endoscope 30 is connected to the endoscope processor. The system controller 24 controls the operation of each part of the endoscope unit 10 based on the read data.

  In the processor image processing unit 23, predetermined image processing is performed on the received image signal. Further, the processor image processing unit 23 can execute HDR synthesis based on the high luminance image signal and the low luminance image signal. Further, the processor image processing unit 23 can perform arbitrarily selected image processing on the image signal.

  An image signal subjected to predetermined image processing and arbitrary image processing is transmitted to the monitor 11. An image corresponding to the received image signal is displayed on the monitor 11.

  As described above, the image pickup device 32 is driven to generate an image signal every 1/60 seconds, and the image signal is transmitted to the monitor 11 every 1/60 seconds. A moving image is displayed on the monitor 11 by switching the image to be displayed every 1/60 seconds.

  If a still image observation command is input to the input unit 25 while a moving image is being displayed on the monitor 11, the transmission of the image signal to the monitor 11 can be stopped and the still image of the subject can be displayed on the monitor 11. is there.

  The endoscope unit 20 is provided with a normal image display mode for displaying a normal image and an HDR image display mode for displaying an image with an expanded dynamic range. In both the normal image display mode and the HDR image display mode, a moving image and a still image can be displayed.

  Illumination light emission control and image capturing control by the image sensor 32 executed by the light source system 21 in the normal image display mode will be described with reference to the timing chart of FIG.

  The image sensor 32 has pixels (not shown) arranged two-dimensionally on the light receiving surface, and each pixel has a signal charge corresponding to the amount of received light during the light receiving period (see “Image sensor light receiving timing” column). Accumulated. The signal charge accumulated during the light receiving period is read out as a pixel signal constituting an image signal of one field during the blanking period (see “image sensor light receiving timing” column).

  As described above, the image sensor 32 is driven so as to generate an image signal of one field in 1/60 second. Therefore, the light receiving period and the blanking period are alternately repeated, and an image signal of one field is generated for every 1/60 second field period in which a single light receiving period and a continuous single blanking period are totaled. The

  The LED is controlled by the timing controller 22 so that the illumination light blinks. The start time, end time, and length of the light emission period (refer to the “illumination light irradiation period” column) from when the illumination light is emitted until it is extinguished depends on the normal image display mode and the HDR image display mode. Different.

  The normal light emission period, which is the light emission period in the normal image display mode, is controlled so as to be a fixed length within the light reception period. That is, the normal light emission period starts at a time delayed by a predetermined period from the start time of the light reception period, and the normal light emission period ends at a time earlier than the end time of the light reception period. Therefore, the normal light emission period starts every 1/60 seconds.

  Usually, an endoscope is used for observing a subject in an area where light does not reach, such as in a body or a structure. Therefore, in such a region, the optical image of the subject reaches the image sensor 32 and signal charges are generated during the light emission period of the LED. On the other hand, in such a region, the amount of light received by the image sensor 32 is substantially zero during the extinguishing period of the LED, and no signal charge is generated. Therefore, the light emission period of the LED is a substantial exposure time of the image sensor 32.

  As described above, the normal light emission period has a constant length during all field periods. Therefore, the exposure time of the image sensor 32 is kept constant during all field periods. In the normal image display mode, a normal image signal in a state where the exposure time is kept constant is generated.

  Even when a still image observation command is input, the imaging control of the image sensor 32 and the illumination light emission control are the same. Therefore, illumination light is emitted every field period even after the command is input, and an image signal of one field is generated. However, transmission of the generated image signal to the monitor 11 is stopped, and a still image corresponding to the most recent image signal transmitted before the stop is displayed on the monitor 11.

  Next, illumination light emission control and image capturing control performed by the image sensor 32 executed by the light source system 21 in the HDR image display mode will be described with reference to the timing chart of FIG.

  Even in the HDR image display mode, the image sensor 32 is driven so that an image signal of one field is generated every field period that is the sum of the same light receiving period and the same blanking period as in the normal image display mode.

  On the other hand, as described above, in the HDR image display mode, the start time, end time, and length of the light emission period are changed from those in the normal image display mode. In the HDR image display mode, the light emission timing and the light extinction timing of the LED are controlled so that the first and second light emission periods having different lengths are alternately repeated with the light extinction period interposed therebetween. Note that the second light emission period is controlled to be shorter than the first light emission period.

  The first and second light emission periods can be changed, and are changed when a command for adjusting the brightness of the HDR image is input to the input unit 25. When expanding the luminance range of the HDR image on the high luminance side and the low luminance side, the first and second light emission periods are extended, respectively. Conversely, when the luminance range is reduced on the high luminance side and the low luminance side, the first and second light emission periods are shortened, respectively.

  In addition, the light emission timing and the light extinction timing of the LED are controlled so that the center interval between the continuous first and second light emission periods is the same constant interval (see symbol c) as the field period.

  As described above, the second light emission period is shorter than the first light emission period. Accordingly, the low luminance image signal L (see “image signal generation” column) in which signal charges are accumulated during the second light emission period is higher than the high luminance image signal H in which signal charges are accumulated during the first light emission period. It is an image signal generated with a short exposure time.

  Note that the processor image processing unit 23 performs HDR synthesis using the latest high-luminance image signal H and low-luminance image signal L. That is, when the high luminance image signal H is generated, HDR synthesis is executed using the low luminance image signal L generated during the immediately preceding field period. When the low luminance image signal L is generated, HDR synthesis is executed using the high luminance image signal H generated during the immediately preceding field period.

  Unlike the normal image display mode, when a still image observation command is input in the HDR image display mode, the emission timing of the illumination light is changed from the emission timing when the moving image is displayed. The illumination light emission time during still image observation will be described below with reference to FIG. Note that image capturing control by the image sensor 32 is the same as when moving images are displayed.

  When a still image observation command is input (see timing t1), the light reception period next to the light reception period at the time of command input and the start time and end time of the light emission period in the next light reception period are changed.

  In the light receiving period (see reference B) following the light receiving period (see reference A) at the time of command input, the first light emission period is started so that the end time overlaps with the end time (t2) of the light receiving period. Further, in the next light receiving period (see symbol C), the second light emission period is started so that the start time overlaps the start time (t3) of the light receiving period.

  When the light emission period during the light reception period at the time of command input is the first light emission period, the end time of the second light emission period overlaps with the end time of the light reception period in the next light reception period after the command is input. Thus, light emission is started. Further, light emission is started so that the start time of the first light emission period overlaps the start time of the light reception period in the next light reception period.

  In the processor image processing unit 23, the signal charge is accumulated in the light emission period in which the light reception period and the end time are overlapped, and the signal charge is accumulated in the light emission period in which the light reception period and the start time are overlapped. HDR synthesis is executed using the image signal (see reference E).

  As described above, according to the endoscope light source system to which the present embodiment is applied, it is possible to generate a high luminance image signal and a low luminance image signal without using an electronic shutter.

  According to the endoscope light source system of the present embodiment, unlike the case where an electronic shutter is used, the signal charge accumulation timing can be adjusted.

  As shown in FIG. 5, when an electronic shutter is used, signal charges are generated and accumulated after the signal charges accumulated by the electronic shutter are discarded until the end time of the light receiving period (“electronic shutter”, (See “Signal charge accumulation period” column). When the electronic shutter is used, unlike the present embodiment, the signal charge accumulation end time cannot be adjusted.

  When the signal charge accumulation end time cannot be adjusted, the influence of blurring appearing in the HDR image created by HDR synthesis changes in the display of the moving image. The effect of blur will be described below.

  Since the generation time of the high-intensity image signal and the low-intensity image signal used for HDR synthesis is different, when a moving subject is photographed, a shift occurs in the position of the subject when the high-intensity image signal and the low-intensity image signal are generated To do.

  When the electronic shutter is used, the interval from the signal charge accumulation end timing of the high luminance image signal to the signal charge accumulation start timing of the low luminance image signal (see L1 in FIG. 5) is the signal charge of the low luminance image signal. Is longer than the interval (see symbol L2 in FIG. 5) from the accumulation end timing of the high luminance image signal to the signal charge accumulation start timing.

  Therefore, the influence of the blurring on the moving subject described above is greatly expressed by the HDR image generated by HDR combining the high luminance image signal and the low luminance image signal generated in the next field. Since the influence of blur changes each time the display image is switched, the sense of discomfort given to the observer increases.

  On the other hand, in the present embodiment, the interval from the light emission period in an arbitrary light reception period, that is, the end time of the substantial signal charge accumulation period to the start time of the light emission period in the next light reception period is always constant (FIG. 3 “ Refer to “Illumination time” Therefore, the influence of blurring on the moving subject described above appears equally for an image whose display is switched every 1/60 seconds. Therefore, it is possible to reduce the viewer's uncomfortable feeling when switching images.

  In addition, according to the endoscope light source system of the present embodiment, when a still image observation command is input in the HDR image display mode, the signal charges of the continuous high luminance image signal and low luminance image signal are substantially accumulated. The time is approaching. It is possible to reduce the influence of blurring appearing in the HDR image by approaching the substantial accumulation timing of the signal charge.

  In the present embodiment, in the HDR image display mode, the center interval of the continuous first and second light emission periods is controlled to be the same constant interval as the field and the period. It is not necessary to control the distance.

  In the HDR synthesis for moving images as in the present embodiment, it is preferable that the generation interval between the high-luminance image signal and the low-luminance image signal is constant. When the luminance image signal is used, the control may not be necessary as described above.

  In the present embodiment, in the HDR image display mode, when a still image observation command is input, the end time of the light emission period in the next light reception period is overlapped with the end time of the light reception period, and further in the next light reception period. The start time of the light emission period is overlapped with the start time of the light reception period, but if the end time of the light emission period in the previous light reception period and the start time of the light emission period in the subsequent light reception period are closer than those during movie observation Good.

  In the present embodiment, the first and second light emission periods can be adjusted. However, a fixed value that cannot be changed may be used. Even if it cannot be changed, the same effect as this embodiment can be obtained.

  In the present embodiment, the generated high-intensity image signal and low-intensity image signal are used for HDR synthesis, but are used for other image processing that requires the high-intensity image signal and the low-intensity image signal. It may be a configuration.

  Further, in this embodiment, by controlling the duty applied to the LED, the length of the light emission period of the illumination light from the LED, the start time of the light emission period, and the end time of the light emission period are changed. The same effect as in the present embodiment can be obtained by changing the length of the emission period of the illumination light from the light source system 21, the start time of the emission period, and the end time of the emission period by other mechanisms.

  For example, the emission period from the light source system 21 of illumination light emitted from a light source that emits light at all times, the start time of the emission period, and the end time of the emission period can be changed by adjusting the light shielding period by opening and closing the mechanical shutter. There may be.

  In this embodiment, the illumination light is irradiated onto the subject. However, the light irradiated onto the subject is not limited to the illumination light. Any irradiation light irradiated for photographing an optical image of a subject may be irradiated. For example, the subject may be irradiated with excitation light that emits fluorescence when irradiated on a living tissue.

  In addition, the configuration is applied to an endoscope light source system and an endoscope unit using an electronic endoscope according to the present embodiment, but is applied to an endoscope unit having an image sensor like an add-on camera. Is possible.

DESCRIPTION OF SYMBOLS 10 Endoscope unit 20 Endoscope processor 21 Light source system 22 Timing controller 23 Processor image processing part 24 System controller 25 Input part 30 Electronic endoscope 32 Image pick-up element 34 Endoscope memory

Claims (8)

Endoscope light source for supplying irradiation light to the subject in an endoscope unit having an image sensor that generates an image signal corresponding to an optical image of the subject received during a continuous light receiving period with a blanking period interposed therebetween A system,
A light source that emits the irradiation light;
The irradiation light is emitted during a first light-receiving period shorter than the light-receiving period during the first light-receiving period of the image sensor, and during the second light-receiving period following the first light-receiving period. An endoscope light source system, comprising: an emission period control unit that emits the irradiation light for a second emission period that is shorter than the first light reception period and different in length from the first emission period. A first input unit for detecting a still image shooting command input that is a command for shooting a still image on the image sensor;
When the first input unit detects the still image shooting command input, the emission period control unit brings the end time of the first emission period close to the start time of the second emission period. The light source system for an endoscope according to claim 1, wherein an emission timing of the irradiation light is controlled. A second input unit that detects a period change command input that is a command for changing the first and second emission periods;
3. The emission period control unit changes the first and second emission periods when the second input unit detects the period change command input. 4. Endoscope light source system.   The emission period control unit alternately repeats the first and second emission periods for emitting the emitted light for each successive light receiving period with the blanking period in between, and the first and second emission periods. The endoscope light source system according to any one of claims 1 to 3, wherein the irradiation timing of the irradiation light is controlled so that a center interval of the emission period is kept constant.   The said emission period control part adjusts the emission period of the said irradiation light by making the said light source change the light emission period of the said irradiation light, The Claim 1 characterized by the above-mentioned. Endoscope light source system.   The endoscope according to any one of claims 1 to 4, wherein the emission period control unit adjusts the emission period of the irradiation light by adjusting a light shielding period of the irradiation light. Light source system. An image sensor that generates an image signal corresponding to an optical image of an object received during a continuous light receiving period with a blanking period interposed therebetween;
A light source that emits irradiation light, which is light that irradiates the subject;
The irradiation light is emitted only during a first emission period shorter than the light reception period during the first light reception period of the image sensor, and during the second light reception period following the first light reception period, An endoscope unit comprising: an emission period control unit that emits the irradiation light for a second emission period that is shorter than the first light reception period and different in length from the first emission period.   8. The image processing apparatus according to claim 7, further comprising an image processing unit that generates a high dynamic range image signal with an expanded dynamic range using the image signals generated during the first and second light receiving periods. Endoscopic unit.

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