JP2007000273A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a still image with less blur in a freeze and prevent heating of an observation object body by an illumination light in an imaging device having a light source section. <P>SOLUTION: This imaging device having the light source section is provided with a liquid crystal shutter in a light path from a light source lamp of the light source section to the tip of a camera head section via an illumination light guide and controls the light quantity of the illumination light passing through the liquid crystal shutter to control the light quantity of the illumination of the observation object body. The light quantity passing through the liquid crystal shutter is adjusted based on a driving signal synchronous with a vertical synchronous signal of a solid-state image sensing device. This constitution sets an electronic shutter in a light flux in the freeze, controls the liquid crystal shutter at a field or frame unit for increasing the illumination light quantity and eliminate a transitional picture variation formed in adjusting exposure to control the optimal exposure in a short period of time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus having an illumination light source, and reduces blurring of still images and illumination in an imaging apparatus such as an electronic endoscope apparatus for imaging an object to be observed and a microscope apparatus incorporating a solid-state imaging element. The present invention relates to a technique that enables appropriate exposure adjustment while suppressing heat generation of an observation object due to light.

  FIG. 7 shows a basic configuration of an electronic endoscope apparatus as a conventional example of such an imaging apparatus. The electronic endoscope apparatus shown in FIG. 1 includes an endoscope main body (scope unit) 70 constituting a camera head unit, a signal processing unit 80 that processes a video signal output from the endoscope main body 70, The display unit 100 is connected to the signal processing unit 80. In addition, a light source unit 90 is optically coupled to the endoscope main body unit 70.

  The endoscope main body 70 incorporates an imaging system including an objective lens 71 and a solid-state imaging device 72 disposed at a distal end thereof, and an illumination system including an illumination lens 75 and a light guide 76. The light guide 76 is formed of, for example, an optical fiber cable, and extends to the light source unit 90 and is optically coupled.

  The light source unit 90 includes a light source lamp 94, an infrared cut filter 93, a condenser lens 92, and a diaphragm mechanism 95. The light emitted from the light source lamp 94 is sent to the light guide 76 through the infrared cut filter 93, the condenser lens 92, and the diaphragm mechanism 95.

  The signal processor 80 processes the video signal output from the endoscope body 70 into a displayable signal format. The display unit 100 displays an image of the observation object imaged by the solid-state imaging device 72 of the endoscope main body unit 70 based on the processed video signal from the signal processing unit 80.

  In such an electronic endoscope apparatus, in order to adjust the exposure of the solid-state imaging device, the electronic shutter means for controlling the iris control by the diaphragm mechanism 95 of the light source unit 90 of FIG. 7 and the charge sweeping time of the solid-state imaging device. Is available. Generally, exposure control is performed using only an electronic shutter without providing the diaphragm mechanism 95, or exposure control is performed using both the electronic shutter and diaphragm control by providing the diaphragm mechanism 95. In the latter case, for example, when the brightness of the object to be observed is dark, the electronic shutter is set to 1/60 seconds and the amount of light is adjusted by the diaphragm mechanism, and the electronic shutter is gradually increased in speed as it becomes brighter. For example, a method of adjusting the light amount by the diaphragm mechanism after setting to 1/500 seconds or the like is used. In addition to such exposure adjustment, the AGC (automatic gain adjustment) circuit may be used to make the level of the video signal constant.

  Further, when using an electronic endoscope apparatus, it is often necessary to observe an image of an object to be observed as a still image. In this case, in order to obtain a still image with less blur, the amount of light to the object to be observed is increased so that the electronic shutter of the solid-state image sensor is operated at a high speed, for example, 1/500 second. In order to increase the amount of illumination light to the object to be observed, it is conceivable to use a bright light source lamp 94 or increase the number of optical fibers constituting the illumination light guide. However, when the amount of illumination light is increased in this way, the temperature at the distal end of the endoscope rises, and the heat generation of the object to be observed increases, which causes a problem.

  In general, a xenon lamp or a halogen lamp is used as a light source lamp of an electronic endoscope apparatus. However, the xenon lamp cannot easily control the amount of light, and the halogen lamp can control the amount of light, but there is a problem that the color temperature changes when the amount of light is controlled.

  From the above, when exposure adjustment is performed using only the electronic shutter, a light source lamp that is not very bright is used in consideration of the problem of heat generation of the object to be observed. For this reason, the speed of the electronic shutter cannot be increased, and it is difficult to obtain a still image with little blurring during freezing. On the other hand, in the case of the method using the electronic shutter and iris control by the diaphragm mechanism (95) in combination, a bright light source lamp can be used, so that a desired fast electronic shutter speed, for example, 1/500 second, 1/1000. It is easy to get seconds and so on. However, in this case, if it is used for a long time in a state where the amount of light is large, a temperature rise at the distal end portion of the endoscope becomes large and heat generation of the object to be observed becomes a problem.

  In the above description, various problems are shown by taking an electronic endoscope apparatus as an example of the imaging apparatus. However, similar problems occur in a microscope apparatus using a solid-state imaging element.

In order to solve such a problem, as shown in JP-A-6-296580, at the time of freezing, the aperture is fully opened and a high electronic shutter speed, for example, 1/500 second, 1/1000 second, etc. Has proposed a method for driving and controlling a solid-state imaging device (CCD). Further, as disclosed in Japanese Patent Application Laid-Open No. 2003-284687, the light from the light source lamp is reflected by the micromirror device having a high response speed and is incident on the light guide, and the deflection angle of the micromirror is controlled. It has also been proposed to control the light emitted from the distal end of the endoscope.
JP-A-6-296580 JP 2003-284687 A

  However, there are some problems to be solved regarding the exposure control technique in the electronic endoscope apparatus proposed so far. First, in the case where the CCD is driven and controlled at a high electronic shutter speed with the aperture fully opened at the time of the above-mentioned freeze, after the freeze switch is pressed, the necessary operation is completed until a stable still image is obtained. There was a problem that time delay occurred. In addition, in the case of using a micromirror device, the response speed is fast, but there is a problem that the apparatus configuration becomes complicated and the reliability is lowered, and the cost of the apparatus is increased.

  An object of the present invention is to provide an imaging apparatus such as an electronic endoscope apparatus that can control the amount of illumination light from a light source lamp at a high speed and suppress the heat generation of an object to be observed in view of the problems in the prior art. There is.

  Another object of the present invention is to control the amount of illumination light from the light source lamp at a high speed and suppress the heat generation of the object to be observed, and has a simple apparatus configuration and a highly reliable electronic endoscope apparatus. An imaging apparatus is provided.

  According to one aspect of the present invention, a camera head unit including an illumination system including a light guide that guides light for illuminating an object to be observed, and an imaging system including an objective lens and a solid-state imaging device; and An imaging device is provided that includes a signal processing unit that processes an output video signal, and a light source unit that includes a light source lamp and supplies light to the light guide, and the imaging device is provided from the light source lamp of the light source unit. A liquid crystal shutter is provided in an optical path leading to the tip of the camera head through a light guide, and the amount of illumination light transmitted through the liquid crystal shutter is controlled to control the amount of illumination light of the object to be observed. .

  Conveniently, the liquid crystal shutter is configured to control the amount of light of a part of the illumination light of the object to be observed.

  If it says from another viewpoint, you may comprise so that the permeation | transmission light quantity control area | region of the said liquid-crystal shutter may be arrange | positioned in a part of cross-sectional area | region of the light beam of the illumination light of the said to-be-observed body.

  It is convenient to control the amount of light transmitted through the liquid crystal shutter in synchronization with a vertical synchronization signal supplied to the solid-state imaging device.

  The light source unit further includes an infrared cut filter that removes infrared rays from the light source lamp, and a condenser lens that receives light passing through the infrared cut filter and guides the light to the light guide, and the liquid crystal shutter includes the condenser lens and It can be provided between the light guides.

  In this case, the liquid crystal shutter may be provided between the infrared cut filter and the condenser lens.

  The imaging apparatus is an electronic endoscope apparatus including an endoscope main body that constitutes the camera head unit, and the light guide extends from the light source unit to the inside of the endoscope main body to extend the object to be observed. The illumination light can be configured to be guided from the light source part to the distal end of the endoscope main body part.

  According to the present invention, it is possible to control the amount of light from the light source lamp at a high speed by using a liquid crystal shutter instead of the mechanical aperture mechanism, and to appropriately suppress the heat generation of the object to be observed. Become. Further, since no mechanical diaphragm mechanism is used, the apparatus configuration is simplified and the reliability is improved.

  Furthermore, according to the present invention, it is possible to perform dimming in synchronization with the vertical synchronizing signal, and it is possible to easily combine with exposure adjustment by an electronic shutter, and control of illumination light quantity and exposure adjustment by an electronic shutter. Can be performed at the same timing. For this reason, at the time of freezing, the electronic shutter can be quickly set at high speed, and illumination light matching the electronic shutter speed can be controlled by the liquid crystal shutter. Therefore, not only can a still image with less blurring be obtained quickly when necessary, but also the amount of illumination light in a normal imaging operation can be suppressed, and the problem of heat generation of the object to be observed can be solved appropriately. .

  FIG. 1 shows a schematic configuration of an electronic endoscope apparatus as an imaging apparatus according to an embodiment of the present invention. The apparatus shown in FIG. 1 includes an endoscope main body unit (scope unit) 10, a signal processing unit 20, a light source unit 30, and a display unit 40.

  The endoscope main body 10 incorporates an imaging system including an objective lens 11 and a solid-state imaging device 12 such as a CCD disposed at a distal end thereof, and an illumination system including an illumination lens 15 and a light guide 16. . In addition, a buffer amplifier (BA) 13 is provided to send the output video signal of the solid-state imaging device 12 to the signal processing unit 20.

  The signal processing unit 20 receives a video signal from the solid-state imaging device 12 of the endoscope body unit 10 and generates a timing and synchronization signal with a CDS / AGC unit 21 that performs correlated double sampling and automatic gain control. A timing generator / synchronization signal generator (TG / SSG) 22, a drive circuit 23 for generating a liquid crystal shutter control signal, and a signal processing circuit 24 including a microprocessor and the like are provided.

  In addition to the light source lamp 34, the infrared cut filter 33, and the condenser lens 32, the light source unit 30 includes a liquid crystal shutter 31 provided according to the present invention.

  In the electronic endoscope apparatus of FIG. 1, the light from the light source lamp 34 in the light source unit 30 passes through the infrared cut filter 33 and the condenser lens 32 and then adjusts the amount of transmitted light by the liquid crystal shutter 31 as will be described later. And enters the light guide 16. The illumination light that has passed through the light guide 16 is applied to an object to be observed (not shown) via the illumination lens 15 at the tip of the endoscope body 10.

  An image of the object to be observed is picked up by an image pickup system including an image pickup lens and a solid-state image pickup device 12 in the endoscope main body 10, and the obtained video signal is sent to the signal processing unit 20 via the buffer amplifier 13. In the signal processing unit 20, the video signal is subjected to processing such as correlated double sampling and automatic gain control in the CDS / AGC unit 21 and then input to the signal processing circuit 24. The signal processing circuit 24 performs further necessary processing on the input signal, for example, gamma correction, application of a synchronization signal, and the like, and supplies the signal to the display unit 40 to display an image of the object to be observed.

  In this case, the TG / SSG unit 22 supplies necessary timing signals and synchronization signals to the solid-state imaging device 12 of the endoscope body unit 10, the signal processing circuit 24 in the signal processing unit 20, the drive circuit 23, and the like. The operation timing of each unit is controlled.

  The drive circuit 23 generates a liquid crystal shutter control signal based on a command from the signal processing unit 24 in synchronization with the vertical synchronization signal from the TG / SSG unit 22 and supplies it to the liquid crystal shutter 31 of the light source unit 30. Therefore, the amount of illumination light transmitted through the liquid crystal shutter 31 can be adjusted by this drive signal.

  As the liquid crystal shutter 31, for example, a π cell used for stereoscopic liquid crystal shutter glasses, or other liquid crystal units can be used. The response speed of the liquid crystal shutter composed of π · cells is as high as about 160 Hz (6.25 ms), and the contrast ratio at the time of on / off is about 300: 1, which is suitable for light quantity adjustment.

  FIG. 2A is a schematic diagram for explaining a detailed configuration and operation of a portion including the liquid crystal shutter 31 of the light source unit 30. FIG. 2B shows the positional relationship between the liquid crystal shutter 31 and the luminous flux R of the illumination light.

  As shown in these drawings, the liquid crystal shutter 31 is disposed in an optical path that enters the light guide 16 from the light source lamp 34 through the infrared cut filter and the condenser lens 32. In the present embodiment, the liquid crystal shutter 31 has a larger size than the diameter of the luminous flux R of the illumination light so as to cover the total luminous flux R in the optical path of the illumination light. With this configuration, the entire illumination light beam can be controlled at a high speed and in a wide range. That is, the illumination light quantity can be controlled at a high speed and in a wide range.

  The liquid crystal shutter 31 is conveniently provided behind the infrared cut filter 33 as shown in FIGS. 1 and 2A in order to suppress the influence of heat from the light source lamp 34. In this embodiment, as shown in FIGS. 1 and 2A, the liquid crystal shutter 31 is provided after the condenser lens 32 further rearward than the infrared cut filter 33. The liquid crystal shutter 31 includes the infrared cut filter 33 and the condenser lens. 32 can also be provided.

  FIG. 3 shows an example in which dimming control is performed on a part of the light beam of the illumination light from the illumination light source by a liquid crystal shutter as another embodiment of the present invention. As described above, the liquid crystal shutter can obtain a high response speed and a high contrast, but a loss occurs when light is transmitted. Therefore, when the light transmittance is controlled by increasing the light transmittance from the illumination light source, a liquid crystal is applied to a part of the luminous flux R of the illumination light as shown in FIGS. 3 (A), (B) and (C). The shutter 31, that is, the control area of the liquid crystal shutter can be arranged, and the remaining area can be configured to transmit light as it is.

  FIG. 3A shows an example in which the transmitted light amount control region of the liquid crystal shutter is arranged at the center of the luminous flux R of the illumination light, that is, the hatched portion in the figure. The outer side of the shaded area is a transmission area T, and the illumination light is transmitted as it is without performing the liquid crystal shutter control. Accordingly, it is possible to cope with a case where the amount of illumination light is reduced by the liquid crystal shutter and the amount of light becomes insufficient.

  In FIG. 3B, the liquid crystal shutter 31, that is, the transmitted light amount control region of the liquid crystal shutter is arranged in the peripheral portion and the shaded portion of the illumination light beam R, and the central portion of the illumination light beam R is the transmission region T. It is a configuration. Even with this configuration, attenuation of light from the illumination light source can be suppressed, and light from the illumination light source can be used efficiently.

  Further, FIG. 3C shows an example in which, for example, a lattice-shaped transmitted light amount control region is arranged on the liquid crystal shutter 31. The transmitted light amount control region can be an arbitrary pattern other than a lattice shape.

  It should be noted that the method of providing the transmitted light amount control region of the liquid crystal shutter in a part of the cross-sectional region of the illumination light beam is not limited to the above example, and it is apparent that various forms are possible.

  FIG. 4 schematically shows the operation when the transmitted light amount control of the liquid crystal shutter is performed in synchronization with the vertical synchronization signal. 4A shows an example of the vertical synchronization signal, FIG. 4B shows a liquid crystal shutter drive signal applied to the liquid crystal shutter 31, and FIG. 4C shows such a liquid crystal shutter drive signal. It shows a change in the amount of light transmitted through the driven liquid crystal shutter.

  That is, in the example shown in FIG. 4, the liquid crystal shutter drive signal is generated in synchronization with the vertical synchronization signal generated by the TG / SSG 22 (FIG. 1).

  The vertical synchronization signal is also supplied from the TG / SSG 22 to the solid-state image sensor 12 of the endoscope main body 10 and the electronic shutter operation of the solid-state image sensor 12 is performed. Therefore, by controlling the liquid crystal shutter 31 in synchronization with the vertical synchronizing signal, exposure adjustment can be suitably performed in consideration of the operation timing of the electronic shutter of the solid-state imaging device 12.

FIG. 5 schematically shows an imaging operation including an electronic shutter operation of a solid-state imaging device such as a CCD. The signal charge accumulated when light is incident on a pixel of the solid-state imaging device increases linearly with time as shown in the figure, and is usually 1 field period (in the case of NTSC system, 1/60). Seconds), C ₆₀ charge is accumulated. This signal charge is simultaneously read to the vertical transfer unit by the vertical transfer clock, the charge of the pixel becomes zero, and charge accumulation is started again. Actually, since the electronic shutter operation is performed, after the charges accumulated for a certain period are swept out, effective signal charges are accumulated again from zero.

That is, by setting the electronic shutter time t1, at the time of the lapse of 1/60-t1 = t _s time, so far accumulated have signal charge C _s are swept out. Then, the accumulation of the signal charge starts again from zero and is accumulated for the electronic shutter time t1, and then the signal charge of C _t1 is obtained. The signal charge C _t1 is a signal charge corresponding to the electronic shutter time t1, and is transferred to the vertical transfer unit and read out.

  FIG. 6 shows the relationship between the electronic shutter operation of such a solid-state imaging device and the change in illumination light quantity controlled by the liquid crystal shutter. For example, in an electronic endoscope apparatus, when it is desired to freeze a captured image and observe it as a still image, it is necessary to increase the electronic shutter speed, for example, 1/500 second, in order to reduce blurring. . Since the electronic shutter operation removes unnecessary charges, if the electronic shutter speed is increased, the sensitivity is reduced accordingly, and thus the amount of illumination light needs to be increased. Therefore, in such a case, it is necessary to increase the setting of the electronic shutter speed and increase the amount of illumination light. When such an operation is performed, as shown in FIG. 6, an increase in the amount of illumination by the liquid crystal shutter can be performed in synchronization with the vertical synchronization signal, thereby eliminating a transient image change that occurs during exposure adjustment. This makes it possible to perform optimal exposure control in a short time.

The light amount adjustment by the liquid crystal shutter is conveniently performed in synchronization with the vertical synchronization signal and at a time other than the electronic shutter time t1 (FIG. 5). That is, it may be performed during the sweep charge accumulation period (t _s ). However, since the sweep charge accumulation period changes according to the electronic shutter speed, the light amount control by the liquid crystal shutter is performed at an electronic shutter such as the beginning of the sweep charge accumulation period. It is convenient to carry out at a time that does not affect the charge accumulation at time t1. As a result, a transitional image change does not occur with exposure adjustment, and exposure control can be performed quickly.

  The present invention can be applied to an imaging apparatus having an illumination light source such as an electronic endoscope apparatus, a microscope apparatus with a built-in solid-state imaging device, etc. It is possible to prevent heat generation and perform accurate imaging.

1 is a block circuit diagram showing a schematic configuration of an electronic endoscope apparatus as an imaging apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram (A) illustrating a configuration near a liquid crystal shutter of a light source unit in the imaging apparatus of FIG. 1 and an explanatory diagram (B) illustrating an arrangement relationship between the liquid crystal shutter and a luminous flux of illumination light. FIG. 4A shows another configuration example of the liquid crystal shutter portion of the image pickup apparatus according to the present invention. FIG. 4A shows an example in which the control area of the liquid crystal shutter is arranged at the center of the luminous flux of illumination light, and FIG. 2 shows an example in which the control area of the liquid crystal shutter is arranged in the periphery of the luminous flux of illumination light, and FIG. 3C shows an example in which the light quantity control area of the liquid crystal shutter is configured in a grid pattern. FIG. 6 is a timing chart showing a relationship between a light amount control of a liquid crystal shutter and a vertical synchronization signal in the imaging apparatus according to the present invention. It is explanatory drawing which shows operation | movement of the electronic shutter of a solid-state image sensor. FIG. 6 is a timing diagram illustrating a time relationship between an electronic shutter operation of a solid-state image sensor and an illumination light amount control operation in the imaging apparatus according to the present invention. It is a block circuit diagram which shows the schematic structure of the conventional electronic endoscope apparatus.

Explanation of symbols

10 Endoscope body (camera head)
DESCRIPTION OF SYMBOLS 11 Objective lens 12 Solid-state image sensor 13 Buffer amplifier 14 Drive signal supply line of solid-state image sensor 15 Illumination lens 16 Light guide 20 Signal processing part 21 Correlated double sampling / automatic gain control part 22 Timing generation / synchronization signal generation circuit 23 Liquid crystal Shutter drive circuit 24 Camera signal processing circuit 30 Light source section 31 Liquid crystal shutter 32 Condenser lens 33 Infrared cut filter 34 Light source lamp 40 Display section 95 Aperture mechanism

Claims (7)

A camera head unit having an illumination system including a light guide for guiding light for illuminating an object to be observed, an imaging system including an objective lens and a solid-state imaging device, and a signal for processing a video signal output from the camera head unit In an imaging apparatus including a processing unit and a light source unit that includes a light source lamp and supplies light to the light guide,
A liquid crystal shutter is provided in an optical path from the light source lamp of the light source unit through the light guide to the tip of the camera head unit, and the amount of illumination light transmitted through the liquid crystal shutter is controlled to control the illumination light amount of the object to be observed. An imaging device characterized by controlling the above.   The imaging apparatus according to claim 1, wherein the liquid crystal shutter controls a light amount of a part of a light beam of illumination light of the object to be observed.   The imaging apparatus according to claim 1, wherein a transmitted light amount control region of the liquid crystal shutter is disposed in a part of a cross-sectional region of a light flux of illumination light of the object to be observed.   The imaging apparatus according to claim 1, wherein the amount of light transmitted through the liquid crystal shutter is controlled in synchronization with a vertical synchronization signal supplied to the solid-state imaging device.   The light source unit further includes an infrared cut filter that removes infrared rays from the light source lamp, and a condenser lens that receives light passing through the infrared cut filter and guides the light to the light guide, and the liquid crystal shutter includes the condenser lens and The imaging apparatus according to claim 1, wherein the imaging apparatus is provided between the light guide and the light guide.   The light source unit further includes an infrared cut filter that removes infrared rays from the light source lamp, and a condenser lens that receives light passing through the infrared cut filter and guides the light to the light guide, and the liquid crystal shutter includes the infrared cut filter. The imaging apparatus according to claim 1, wherein the imaging apparatus is provided between a filter and the condenser lens. The imaging apparatus is an electronic endoscope apparatus including an endoscope main body that constitutes the camera head unit, and the light guide extends from the light source unit to the inside of the endoscope main body to extend the object to be observed. The imaging apparatus according to claim 1, wherein the illumination light is guided from the light source unit to a distal end of the endoscope main body unit.

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