JP2004313523A - Solid-state image sensor, electronic endoscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state image sensor which improves the dynamic range without increasing the diameter or lowering the resolution even if the solid-state image sensor is set in a cylindrical apparatus. <P>SOLUTION: The solid-state image sensor, having photoreceivers on a single semiconductor substrate formed to be long in a prescribed direction, is equipped with at least two photoreceivers including first and second photoreceivers in different regions in the prescribed direction, at least two transfer parts including a first transfer part, where charges stored in a plurality of light-sensitive elements included in the first photoreceiver are transferred, and a second transfer part, where charges stored in a plurality of light-sensitive elements included in the second photoreceiver are transferred, and an adding and outputting part which adds the charges, transferred to at least two transfer parts and including the charges transferred to the first transfer part and the charges transferred to the second transferred part, and outputs outward. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid-state imaging device in which a plurality of light-receiving elements are arranged in a matrix on a single semiconductor substrate, and to an electronic endoscope including the solid-state imaging device at a distal end.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, by reducing the diameter of an insertion portion including a distal end portion of an endoscope, pain of a patient when inserting the endoscope into a body cavity, particularly, into a thin tube is reduced. In recent years, electronic endoscopes having a solid-state imaging device such as a CCD at the tip thereof have become widespread, and various components provided therein have been downsized to achieve a smaller diameter. I have. The smaller the endoscope or electronic endoscope, the more it can be inserted into the body cavity and the more freely it can be moved inside the body cavity. Have been.
[0003]
Many electronic endoscopes are equipped with a monochrome CCD suitable for miniaturization for the reasons described above. However, in recent years, in order to observe the state of a living tissue more accurately, a device for obtaining a color image has been put to practical use. There are two main types of devices for obtaining this color image. One is to place an observation target (imaging target) illuminated by white illumination light of a light source device connected to an electronic endoscope on a front surface of each of a plurality of light receiving elements arranged in a matrix on a light receiving unit. A so-called simultaneous method is used in which a color image is obtained by taking an image with a CCD equipped with a color filter. The other is to obtain a color image by taking an image of an observation target illuminated by illumination light of each color through a rotary color filter of a light source device connected to an electronic endoscope with a monochrome CCD, thereby obtaining a color image. It uses a sequential method.
[0004]
However, in recent years, further reduction in the diameter of the electronic endoscope has been required, and it is necessary to further reduce the size of the CCD and the like provided at the distal end. In order to reduce the size of the CCD, it is necessary to reduce the size per pixel. However, as the size per pixel is reduced, the amount of charge that can be stored per pixel decreases. Therefore, the dynamic range of the photographable brightness is reduced.
[0005]
The biological tissue in the body cavity, which is the object to be observed by the electronic endoscope, is observed by illuminating the interior of the body cavity, which is a dark part, with an illumination device. It tends to be particularly large compared to images such as videos. Therefore, when the dynamic range is reduced, the phenomenon that the image of the dark part is crushed black and the image of the bright part is dashed white frequently occurs.
[0006]
Therefore, conventionally, a pair of adjacent light receiving elements having different sensitivities, the electric charge accumulated in each light receiving element is transferred, and the electric charge of the pair of light receiving elements is added to improve the dynamic range ( For example, see Patent Document 1). In addition, a color filter of the same color is mounted for every predetermined number of adjacent pixels, and the electric charge obtained by the predetermined number of pixels of the same color is added according to the set mode to improve the dynamic range and sensitivity. (For example, see Patent Document 2).
[0007]
[Patent Document 1]
JP-A-9-252107 (pages 3 to 5, FIG. 1)
[Patent Document 2]
JP-A-11-298800 (pages 3, 4 and 2)
[0008]
[Problems to be solved by the invention]
However, in the solid-state imaging devices described in Patent Literature 1 and Patent Literature 2 described above, a signal equivalent to one pixel is output by adding charges accumulated in a plurality of pixels. Will decrease. In other words, although the dynamic range and sensitivity can be improved to improve image collapse and overexposure, the output image becomes unclear due to a decrease in resolution. Therefore, it becomes difficult for the surgeon to accurately grasp the state of the details of the living tissue from the image of the living tissue displayed on the monitor.
[0009]
When the amount of charge that can be accumulated is increased by increasing the size per pixel as much as possible to improve the dynamic range while maintaining the resolution, the dynamic range is improved without deteriorating the sharpness of the image. Can obtain a perfect image. However, in order to increase the size per pixel while maintaining the number of pixels, there is a limit in reducing the size of the solid-state imaging device. As a result, the diameter of the electronic endoscope cannot be reduced as desired, and the Can not reduce the burden on
[0010]
In view of the above circumstances, the present invention provides a solid-state imaging device capable of improving the dynamic range without increasing the diameter or reducing the resolution even when incorporated in a cylindrical device, and a solid-state imaging device. It is an object of the present invention to provide an electronic endoscope provided with an imaging device.
[0011]
[Means for Solving the Problems]
A solid-state imaging device according to one embodiment of the present invention which solves the above problem has a structure in which a plurality of light-receiving elements for receiving light from an imaging target are arranged in a matrix on a single semiconductor substrate formed to be long in a predetermined direction. Has a light receiving portion disposed in the first position. The solid-state imaging device is stored in at least two light receiving units including a first light receiving unit and a second light receiving unit in different regions in a predetermined direction, and a plurality of light receiving elements included in the first light receiving unit. At least two transfer units including a first transfer unit that is a transfer destination of the charge, a second transfer unit that is a transfer destination of the charge accumulated in the plurality of light receiving elements included in the second light receiving unit, An addition output unit that adds the charges transferred to at least two transfer units including the charges transferred to the first transfer unit and the charges transferred to the second transfer unit, and outputs the sum to the outside . As described above, by adding and outputting the respective charges accumulated in at least two light receiving units arranged in different regions in the predetermined direction on a single semiconductor substrate formed long in the predetermined direction, Image information with an improved dynamic range can be output without increasing the size of the apparatus or reducing the resolution in a direction orthogonal to the predetermined direction.
[0012]
In the solid-state imaging device, it is preferable that the arrangement of the plurality of light receiving elements included in each of the at least two light receiving units is the same.
[0013]
In the solid-state imaging device, each of the electric charges accumulated in each of the at least two light receiving units is transferred to each of the at least two transfer units for each electric charge accumulated in one row of the light receiving elements in a predetermined direction. Is preferred. In addition, it is preferable that the addition output unit adds the transferred electric charges in each row of the light receiving elements and outputs the added electric charges to the outside. In addition, it is preferable that at least two transfer units are included in elements arranged in a line in a predetermined direction. Further, it is preferable that a dimming unit is disposed on a front surface of one of the first light receiving unit and the second light receiving unit.
[0014]
In the solid-state imaging device, a light beam splitting unit that splits a light beam from an imaging target into a first light beam and a second light beam is disposed on the front surface of the light receiving unit, and the first light beam is guided to the first light receiving unit. Preferably, the second light beam is guided to the second light receiving unit. Preferably, the light beam splitting means is a beam splitter. At this time, the first light beam is a reflected light beam by the beam splitter, and the second light beam is a transmitted light beam by the beam splitter.
[0015]
In addition, an electronic endoscope according to one embodiment of the present invention that solves the above-described problem includes a plurality of light receiving devices for receiving reflected light from an observation target on a single semiconductor substrate that is formed to be long in a predetermined direction. A solid-state imaging device having a light receiving portion in which the devices are arranged in a matrix is provided in the front end portion. The solid-state imaging device provided in the electronic endoscope includes at least two light receiving units including a first light receiving unit and a second light receiving unit in different regions in a predetermined direction, and a first light receiving unit. A first transfer unit that is a transfer destination of the charge accumulated in the plurality of light receiving elements having the first transfer unit and a second transfer unit that is a transfer destination of the charge accumulated in the plurality of light receiving elements of the second light receiving unit. At least two transfer units, the charge transferred to the first transfer unit, and the charge transferred to the at least two transfer units including the charge transferred to the second transfer unit are added and output to the outside And an addition output unit for performing the addition. The solid-state imaging device is further arranged such that the longitudinal direction of the semiconductor substrate and the longitudinal direction of the distal end of the electronic endoscope match. As described above, by adding and outputting the respective charges accumulated in at least two light receiving units arranged in different regions in the predetermined direction on a single semiconductor substrate formed long in the predetermined direction, An image with an improved dynamic range can be output without increasing the diameter of the electronic endoscope or reducing the resolution. Therefore, it is possible to output image information capable of improving the dynamic range and obtaining a smooth image without increasing the burden on the patient or reducing the sharpness of the image.
[0016]
In the electronic endoscope, it is preferable that each of the at least two light receiving units is arranged at a position substantially optically equivalent.
[0017]
In the electronic endoscope, it is preferable that at least two light receiving units have the same arrangement of the plurality of light receiving elements.
[0018]
In the electronic endoscope, it is preferable that each of the electric charges accumulated in each of the at least two light receiving units is transferred to each of the at least two transfer units for each electric charge accumulated in one row of the light receiving elements. . In addition, it is preferable that the addition output unit adds the transferred electric charges in each row of the light receiving elements and outputs the added electric charges to the outside. In addition, it is preferable that at least two transfer units are included in elements arranged in a line in a predetermined direction. Further, it is preferable that a dimming unit is disposed on a front surface of one of the first light receiving unit and the second light receiving unit.
[0019]
Further, in the electronic endoscope, a light beam splitting unit that splits a light beam from an imaging target into a first light beam and a second light beam is disposed on the front surface of the light receiving unit, and the first light beam is transmitted to the first light receiving unit. It is preferable that the second light beam is guided to the second light receiving unit. Preferably, the light beam splitting means is a beam splitter. At this time, the first light beam is a reflected light beam by the beam splitter, and the second light beam is a transmitted light beam by the beam splitter.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram illustrating a configuration of an electronic endoscope apparatus 500 including an electronic endoscope 100 according to an embodiment of the present invention. The electronic endoscope device 500 includes an electronic endoscope (electronic scope) 100 that outputs image information in a body cavity of a patient, and performs predetermined processing on image information output from the electronic endoscope 100 to generate a video signal. It comprises a processor 200 having both an image processing device for conversion and a light source device, and a monitor 300 for displaying the inside of a patient's body cavity based on a video signal output from the processor 200. The configuration and operation of the electronic endoscope device 500 will be described below with reference to FIG.
[0021]
The processor 200 includes a light source unit (light source lamp) 210 that emits illumination light that illuminates the living tissue 400 to be observed in the present embodiment. In the electronic endoscope apparatus 500 of the present embodiment, a plane-sequential imaging system is employed in order to reduce the diameter of the distal end of the electronic endoscope 100. Therefore, the illumination light emitted by the light source 210 is It is white light, and an RGB filter rotation 220 is arranged on the optical path.
[0022]
The RGB rotation filter 220 has three color filters of R (red), G (green), and B (blue), and a light shielding unit. These three color filters are filters that transmit only the corresponding one color light. The RGB rotation filter 220 has a color filter (R), a light shielding unit, a color filter (G), a light shielding unit, a color filter (B), and a light shielding unit in the rotation direction. Hereinafter, a process of generating a color image by the frame sequential method using the RGB rotation filter 220 will be described.
[0023]
First, the timing generator 230 transmits a drive signal to a motor driver (not shown). The motor driver drives the motor 222 based on the received drive signal. Since the rotation shaft of the motor 222 rotatably supports the RGB rotation filter 220, the RGB rotation filter 220 rotates with the driving of the motor 222. The illumination light emitted from the light source unit 210 by the rotation of the RGB rotation filter 220 intermittently passes through the filters of R, G, and B by the light-shielding units provided therebetween.
[0024]
The processor 200 is connected to the electronic endoscope 100 by a connector 280. Each of the illumination lights transmitted through the respective filters of the RGB rotation filter 220 enters the light guide 110 of the electronic endoscope 100 via the condenser lens 224 arranged on the optical path. The illumination light is guided by the light guide 110 to the distal end of the electronic endoscope 100. The illumination light guided to the light guide 110 illuminates a living tissue 400 as an observation target (imaging target) via an illumination window 120 provided on a front surface of the distal end of the electronic endoscope 100.
[0025]
Illumination light illuminating the living tissue 400 is reflected by the living tissue 400 and enters the objective optical system 130 as observation light. The observation light emitted from the objective optical system 130 is bent by the optical path deflecting unit 140 in a direction orthogonal to the optical axis of the objective optical system 130, in other words, the direction perpendicular to the longitudinal direction (insertion direction) of the electronic endoscope 100.
[0026]
In the electronic endoscope 100 of the present embodiment, the solid-state imaging device 150 having a function of receiving observation light and performing photoelectric conversion to generate an image signal has a light receiving surface parallel to the longitudinal direction of the electronic endoscope 100. It is arranged so that it becomes. The solid-state imaging device 150 is, for example, a CCD.
[0027]
The observation light bent by the above-described optical path deflecting unit 140 forms an image on the light receiving surface of the solid-state imaging device 150 and is received by each of the plurality of light receiving elements arranged in a matrix on the light receiving surface. Is done. Since the living tissue 400 is illuminated by the intermittent illumination light that has been transmitted through the filters of the RGB rotation filters 220 in order as described above, the light receiving surface of the solid-state imaging device 150 intermittently transmits the observation light of each color. Are sequentially received.
[0028]
The driver 240 included in the processor 200 drives the solid-state imaging device 150 by a drive control signal transmitted from the timing generator 230. More specifically, the driver 240 performs a period during which the solid-state imaging device 150 receives any one of the R light, the G light, and the B light, based on the drive control signal transmitted from the timing generator 230. The solid-state imaging device 150 is driven to accumulate the observation light in each light receiving element, and the electric charge accumulated in each light receiving element during a period in which the solid-state imaging element 150 does not receive any observation light by the light blocking portion of the RGB rotation filter 220. The solid-state imaging device 150 is driven so as to output the image signal as an image signal.
[0029]
The image signal output from the solid-state imaging device 150 is transmitted to the processor 200 and subjected to image processing described later. The signals processed by the processor 200 are output to the monitor 300 as various video signals (video signals) that can be displayed on an external display device, and displayed on the monitor 300 as a color observation image. Hereinafter, a process of image processing performed by the processor 200 will be described.
[0030]
The image signal of the living tissue 400 in the body cavity obtained by the solid-state imaging device 150 is transmitted to the first-stage video signal processing unit 250 provided in the processor 200. The first-stage video signal processing unit 250 first amplifies the transmitted image signal and performs processing such as sampling and holding. Then, this image signal is converted into a digital image signal. The converted digital image signal is further switched in synchronization with the driving of the solid-state imaging device 150 by a multiplexer (not shown) included in the first-stage video signal processing unit 250, and converted into image signals of R, G, and B colors. The data is separated and output to each memory of the RGB memory 260.
[0031]
The RGB memory 260 includes three not-shown R memories, G memories, and B memories, which are three frame memories corresponding to the respective colors of R, G, and B. The image signals of each color separated by the first-stage video signal processing unit 250 are Are stored in the corresponding frame memories.
[0032]
The timing generator 230 transmits a timing signal for simultaneously reading image signals stored in each frame memory of the RGB memory 260. This timing signal is transmitted, for example, at a timing at which a moving image composed of 30 frames per second can be displayed on the monitor. That is, the timing generator 230 transmits a timing signal for simultaneously reading out the image signals stored in each frame memory of the RGB memory 260 at 30 frames per second. Based on this timing signal, the image signals of the respective colors are read out at the same time and output to the subsequent signal processing unit 270.
[0033]
The latter-stage signal processing unit 270 converts this signal into an analog signal, and further converts this analog signal into a composite video signal, a Y / C signal, and an RGB component video signal for displaying on the monitor 300. Then, when these video signals are output to the monitor 300, an observation image of the living tissue 400 is displayed on the monitor 300 as a color image.
[0034]
FIG. 2 is a side sectional view schematically showing an internal structure of a distal end portion of the electronic endoscope 100 according to the embodiment of the present invention. FIG. 2 shows the internal structure of the distal end of the electronic endoscope 100 in more detail than FIG. Hereinafter, the configuration and operation of the distal end portion of the electronic endoscope 100 will be described in more detail with reference to FIG.
[0035]
As described above, the observation light of the living tissue 400 incident via the objective optical system 130 is bent by the optical path deflecting unit 140 in a direction orthogonal to the longitudinal direction of the electronic endoscope 100. The optical path deflecting unit 140 is formed by bonding a first prism 142 and a second prism 144 together. These prisms are arranged in the longitudinal direction of the electronic endoscope 100 in the order of the first prism 142 and the second prism 144 from the objective optical system 130 side.
[0036]
The first prism 142 has a beam splitter 142a having a function of splitting light on the optical path of observation light of the living tissue 400. The beam splitter 142a is arranged in a state of being inclined by 45 degrees with respect to the optical path of the observation light of the living tissue 400 that coincides with the optical axis of the objective optical system 130. In other words, the beam splitter 142a is arranged in a state of being inclined by 45 degrees with respect to the longitudinal direction of the electronic endoscope 100. Therefore, the observation light of the living tissue 400 incident on the beam splitter 142a is partially bent at 90 degrees and travels in a direction orthogonal to the longitudinal direction of the electronic endoscope 100, that is, toward the solid-state imaging device 150, Part of the light passes through and travels in the second prism 144 along the longitudinal direction of the electronic endoscope 100.
[0037]
More specifically, the beam splitter 142a has a function of splitting the observation light of the living tissue 400 so that the intensity ratio between the light to be bent (reflected light) and the light to be transmitted is 2: 1. I have. Here, the observation light transmitted through the beam splitter 142a has a lower light intensity than the observation light bent by the beam splitter 142a.
[0038]
The second prism 144 has a total reflection mirror 144a having a function of totally reflecting light on the optical path of observation light transmitted through the beam splitter 142a. The total reflection mirror 144a is arranged in a state of being inclined by 45 degrees with respect to the optical path of the observation light transmitted through the beam splitter 142a that coincides with the optical axis of the objective optical system 130. In other words, the total reflection mirror 144a is arranged in a state of being inclined by 45 degrees with respect to the longitudinal direction of the electronic endoscope 100. Therefore, the observation light transmitted through the beam splitter 142a is bent 90 degrees by the total reflection mirror 144a, and travels in a direction orthogonal to the longitudinal direction of the electronic endoscope 100, that is, toward the solid-state imaging device 150.
[0039]
FIG. 3 is a top view schematically illustrating the configuration of the solid-state imaging device 150 provided in the distal end portion of the electronic endoscope 100 according to the embodiment of the present invention. The solid-state imaging device 150 includes a light receiving section 152 in which a plurality of light receiving elements are arranged in a matrix on a semiconductor substrate. The configuration and operation of the solid-state imaging device 150 will be described below with reference to FIG. Note that the surface of the semiconductor substrate, which is the base of the solid-state imaging device 150, provided with the light receiving portion 152 is a rectangle whose side in the arrow Y direction shown in FIG. 3 is longer than the side in the arrow X direction orthogonal to the arrow X direction. It has the shape of
[0040]
The solid-state imaging device 150 includes a light receiving unit 152, a horizontal transfer unit 154, and an amplifier 156. As described above, since the electronic endoscope device 500 generates a color image by a frame sequential method, the solid-state imaging device 150 is a monochrome CCD. Further, in order to achieve a reduction in the diameter of the electronic endoscope 100, the solid-state imaging device 150 is a full-frame CCD having no storage unit.
[0041]
The light receiving section 152 has two image areas (imaging areas) of a light receiving section 152a and a light receiving section 152b. The light receiving section 152a is an image area for capturing the observation optical image reflected by the beam splitter 142a, and is arranged so as to coincide with the image forming plane of the observation optical image. The light receiving unit 152b is an image area for capturing the observation optical image reflected by the total reflection mirror 144a, and is arranged so as to coincide with the imaging plane of the observation optical image. That is, the light receiving unit 152a and the light receiving unit 152 are arranged side by side along the longitudinal direction of the electronic endoscope 100. The same number of light receiving elements are arranged at the same pitch in each of the light receiving section 152a and the light receiving section 152b in the arrow Y direction and the arrow X direction. That is, the light receiving section 152a and the light receiving section 152b are formed as light receiving sections having the same shape and the same number of pixels.
[0042]
Further, since the solid-state imaging device 150 is a full frame type CCD, the light receiving section 152 also has a function of a vertical transfer section for transferring the electric charges accumulated in each of the plurality of light receiving elements in the direction of arrow X in FIG. I have. Since the solid-state imaging device 150 is a small-sized chip, the light receiving unit 152a and the light receiving unit 152b are optically substantially equivalently arranged. Therefore, observation images having substantially the same shape are formed on these two light receiving units.
[0043]
The horizontal transfer unit 154 is a part to which charges accumulated in each of the plurality of light receiving elements included in the light receiving unit 152 are transferred, and is configured by charge coupled elements arranged in a line in the longitudinal direction of the semiconductor substrate. ing. The horizontal transfer unit 154 transfers the charge accumulated in the light receiving element included in the light receiving unit 152a, and the horizontal transfer unit 154a transfers the charge accumulated in the light receiving element included in the light receiving unit 152b. And a horizontal transfer unit 154b.
[0044]
Each of the charge coupled elements constituting the horizontal transfer unit 154 is arranged at the same pitch as the light receiving elements of the light receiving unit 152 in the arrow Y direction. The horizontal transfer unit 154a included in the horizontal transfer unit 154 includes a charge-coupled device that is arranged in alignment with each of the light receiving elements of the light receiving unit 152a in the arrow Y direction. The horizontal transfer unit 154b included in the horizontal transfer unit 154 includes a charge-coupled device that is arranged in alignment with each of the light-receiving elements of the light-receiving unit 152b in the arrow Y direction. Note that each of the charge-coupled devices constituting the horizontal transfer unit 154 has a larger allowable amount so that even if a plurality of light-receiving elements of the light-receiving unit 152 accumulate a plurality of light-receiving elements, they are not saturated. For this reason, it is formed larger than the light receiving element of the light receiving section 152 in the arrow X direction.
[0045]
FIG. 4 is a diagram showing the charge transfer operation of the solid-state imaging device 150. First, as shown in FIG. 4A, the electric charges accumulated in each of the light receiving elements of one line located at the lower end in the arrow X direction of the light receiving unit 152a are simultaneously transferred to the horizontal transfer unit 154a in the arrow X direction. Is done. For example, the electric charge accumulated in the light receiving element located at 152a (1) of the light receiving section 152a is transferred to the charge coupled element located at 154a (1) at the right end of the horizontal transfer section 154a in the arrow Y direction. Next, as shown in FIG. 4B, the charges transferred and accumulated in each charge-coupled device of the horizontal transfer unit 154a are sequentially transferred through the horizontal transfer unit 154 in the arrow Y direction. Then, as shown in FIG. 4C, the electric charge accumulated in the light receiving element located at 152a (1) of the light receiving unit 152a is moved to the position 154b (1) at the right end of the horizontal transfer unit 154b in the arrow Y direction. When the charges are transferred to the corresponding charge coupled elements, the charges accumulated in each of the light receiving elements of one line located at the lower end in the arrow X direction of the light receiving section 152b are simultaneously transferred to the horizontal transfer section 154b in the arrow X direction. , And the previously transferred charges are added. For example, the electric charge accumulated in the light receiving element located at 152a (1) is added to the electric charge accumulated at the light receiving element located at 152b (1) of the light receiving section 152b, and the electric charge is located at 154b (1). Stored in the charge-coupled device. Finally, the charges added and accumulated in each charge-coupled device of the horizontal transfer unit 154b are sequentially transferred to the amplifier 156. The amplifier 156 amplifies the added electric charge and outputs the amplified electric charge to the first-stage video signal processing unit 250 included in the processor 200.
[0046]
FIG. 5 is a timing chart showing a period of imaging and transfer of the solid-state imaging device 150 and a period of observation light incident on the solid-state imaging device 150. FIG. 5A is a timing chart for performing imaging and transfer of the solid-state imaging device 150, in which an accumulation period for accumulating electric charges and a transfer period for transferring electric charges corresponding to each accumulated color are alternately repeated. It has become. FIG. 5B is a timing chart showing the period of the observation light incident on the solid-state imaging device 150. The period in which the observation light of each color is incident and the observation light are shielded. The period is alternately repeated. The details of the timing chart shown in FIG. 5 will be described below.
[0047]
As shown in FIG. 5, while the observation light of the R light of the living tissue 400 illuminated with the R illumination light is incident on the light receiving units 152a and 152b, the solid-state imaging device 150 includes the light receiving units 152a and 152b. In each of the light receiving elements, the charge due to the observation light of the R light is accumulated. When the observation light of R light enters the light receiving units 152a and 152b for a certain period, the illumination light is shielded for a certain period by the light shielding unit of the RGB rotation filter 220, and the observation light incident on each light receiving unit also stops for a certain period. During a period in which the observation light does not enter the light receiving sections 152a and 152b, the solid-state imaging device 150 shows each of the charges by the observation light of the R light accumulated in each of the light receiving elements of the light receiving sections 152a and 152b in FIG. According to the operation procedure, the data is transferred to the horizontal transfer units 154a and 154b, respectively, and added. The charge added by the horizontal transfer unit 154 is output from the amplifier 156 as image information of R light, and transmitted to the first-stage video signal processing unit 250.
[0048]
The solid-state imaging device 150 accumulates the electric charge by the observation light of the G light in the same manner, transfers the accumulated electric charge by the observation light of the G light to the horizontal transfer unit 154, and adds the electric charge. The charges added by the horizontal transfer unit 154 are output from the amplifier 156 as image information of G light, and transmitted to the first-stage video signal processing unit 250. Further, the solid-state imaging device 150 accumulates the charges by the observation light of the B light in the same manner, transfers the accumulated charges by the observation light of the B light to the horizontal transfer unit 154, and adds them. The charge added by the horizontal transfer unit 154 is output from the amplifier 156 as image information of B light, and transmitted to the first-stage video signal processing unit 250.
[0049]
As described above, the image information of each of the R light, the G light, and the B light output from the amplifier 156 is processed by the processor 200, so that a color image of one screen is formed. By repeating this operation at a predetermined cycle, the image of the living tissue 400 is displayed as a moving image on the monitor 300.
[0050]
FIG. 6 is a timing chart showing in detail the transfer operation of the charge accumulated in the light receiving element during the period T in FIG. The period T indicates a period in which the charges accumulated by the observation light of the G light are transferred to the horizontal transfer unit 154 and output from the amplifier 156 as image information of the G light. The charge transfer operation will be described below with reference to the timing chart shown in FIG.
[0051]
FIG. 6A shows V1 that causes the charges accumulated in each of the light receiving elements of the light receiving unit 152a to be sequentially transferred to the horizontal transfer unit 154a via the light receiving element of one line in the arrow Y direction located at the end of the light receiving unit 152a. 6 is a timing chart showing signal pulses. Also, FIG. 6B shows that the charges accumulated in each of the light receiving elements of the light receiving section 152b are sequentially transferred to the horizontal transfer section 154b via the light receiving element of one line in the arrow Y direction located at the end of the light receiving section 152b. 5 is a timing chart showing a pulse of a V2 signal to be performed. FIG. 6C is a timing chart showing a pulse of the H signal for transferring the charges transferred to the horizontal transfer unit 154 in the horizontal direction of the horizontal transfer unit 154, that is, in the direction of the arrow Y.
[0052]
As shown in FIG. 6, when the V1 signal is input to the light receiving unit 152a, all the electric charges accumulated in each of the light receiving elements of the light receiving unit 152a are shifted by one stage (one line) in the direction of the arrow X. As a result, each of the electric charges accumulated in the light receiving element of one line arranged closest to the horizontal transfer unit 154a shifts in the direction of the arrow X so that the charge coupling coincides with the direction of the arrow Y of the horizontal transfer unit 154a. Transferred to each of the elements.
[0053]
When the electric charge is transferred from the light receiving unit 152a to the horizontal transfer unit 154a, an H signal is input to the horizontal transfer unit 154, and the electric charge transferred to the horizontal transfer unit 154a is further transferred in the arrow Y direction. That is, as described in detail above, each charge transferred to each of the charge coupled devices of the horizontal transfer unit 154a is transferred to the corresponding charge coupled device of the horizontal transfer unit 154b by the H signal.
[0054]
When the charge transfer from the horizontal transfer unit 154a to the horizontal transfer unit 154b is completed, the V1 signal is input to the light receiving unit 152a, and the V2 signal is input to the light receiving unit 152b. Therefore, similarly to the above-described processing, all the electric charges accumulated in each of the light receiving elements of the light receiving unit 152a are shifted by one stage in the direction of the arrow X, and the light reception of one line arranged closest to the horizontal transfer unit 154a is performed. Each of the charges stored in the element is transferred to the horizontal transfer unit 154a. The V2 signal has the same function as the V1 signal. That is, all the electric charges accumulated in each of the light receiving elements of the light receiving section 152b are shifted by one stage in the direction of the arrow X, and the electric charges accumulated in the light receiving element of one line arranged closest to the horizontal transfer section 154b. Are transferred to the horizontal transfer unit 154b.
[0055]
As described above, when the charge is transferred from the light receiving unit 152b to the horizontal transfer unit 154b, the charge of the light receiving unit 152a1 line previously transferred from the horizontal transfer unit 154a is already accumulated in each of the charge coupled elements of the horizontal transfer unit 154b. Therefore, each of the charges on the light receiving section 152a1 line and each of the charges on the light receiving section 152b1 line are accumulated in the same charge-coupled device of the horizontal transfer section 154b, and as a result, the respective charges are added. .
[0056]
When the electric charge of the light receiving unit 152a1 line and the electric charge of the light receiving unit 152b1 line are added in the horizontal transfer unit 154b, the H signal is input to the horizontal transfer unit 154 again, and the electric charge added in the horizontal transfer unit 154b is amplified by the amplifier 156. And amplified and transmitted to the first stage video signal processing unit 250. At this time, the electric charges transferred to the horizontal transfer unit 154a by the V1 signal are transferred to the horizontal transfer unit 154b. When the V1 signal is again input to the light receiving unit 152a and the V2 signal is input to the light receiving unit 152b, the electric charge of the horizontal transfer unit 154b is added, and is swept out to the amplifier 156 by the H signal to be amplified and amplified. Sent to.
[0057]
The above-described series of operations is repeated until the charges of all lines accumulated in the light receiving units 152a and 152b are transmitted to the first-stage video signal processing unit 250. When the charges of all lines are output from the amplifier 156, the transfer operation in the period T ends, and the accumulation operation of the observation light of B light starts.
[0058]
FIG. 7 shows the relationship between the signal output (in other words, the accumulated charge amount) of the light receiving element included in the light receiving unit 152a and the light receiving unit 152b and the incident light amount of the observation light (strictly, the light amount incident on the optical path deflecting unit 140). It is the graph shown. The vertical axis of this graph indicates the signal output of the light receiving element, and the horizontal axis indicates the amount of light incident on the light receiving element.
[0059]
The characteristic A shown in this graph shows the relationship between the signal output of the light receiving element of the light receiving unit 152a and the incident light amount of the observation light (the light amount incident on the optical path deflecting unit 140). As described above, in the beam splitter 142a of the optical path deflecting unit 140, since the intensity ratio between the reflected light and the transmitted light is 2: 1, the amount of light incident on the light receiving unit 152a is 2/3 of the amount of incident observation light. Become. The signal output indicated by the characteristic A is a value corresponding to the accumulated charge amount of each of the light receiving elements of the light receiving section 152a transferred to each of the charge coupled elements of the horizontal transfer section 154a. The characteristic B indicates the relationship between the signal output of the light receiving element of the light receiving unit 152b and the incident light amount of the observation light (the light amount incident on the optical path deflecting unit 140). Similarly, the amount of incident light on the light receiving unit 152b is １ ／ of the amount of incident observation light. The signal output indicated by the characteristic B is a value corresponding to the accumulated charge amount of each of the light receiving elements of the light receiving section 152b transferred to each of the charge coupled elements of the horizontal transfer section 154b. The characteristic (A + B) indicates the relationship between the signal output after adding the signal outputs of the respective light receiving elements of the light receiving units 152a and 152b and the incident light amount of the observation light (the light amount incident on the optical path deflecting unit 140). It is a thing. That is, it shows the relationship between the signal output obtained from the light receiving unit 152 and the incident light amount of the observation light. The signal output indicated by the characteristic (A + B) is the accumulated charge amount of the horizontal transfer unit 154a and the horizontal transfer unit 154b added in the horizontal transfer unit 154b.
[0060]
As described above, the intensity ratio between the light incident on the light receiving unit 152a and the light incident on the light receiving unit 152b is 2: 1 by the beam splitter 142a. The light receiving elements of the light receiving unit 152a and the light receiving unit 152b are optically equivalently arranged and have the same shape and the same characteristics. Accordingly, in the graph of FIG. Therefore, when the light receiving element of the light receiving unit 152a obtains the saturation signal output d with the incident light amount c of the observation light, the light receiving element of the light receiving unit 152b obtains the saturation signal output d with the incident light amount 2c of the observation light. This is the same as that the light receiving element of the light receiving unit 152a has twice the sensitivity as compared with the light receiving element of the light receiving unit 152b. In other words, the light receiving element of the light receiving section 152b has twice the dynamic range as compared with the light receiving element of the light receiving section 152a. In addition, the light receiving element of the light receiving unit 152a has a dynamic range that is 1.5 times that of the case where the observation light is directly received by the light receiving element without passing through the optical path deflecting unit 140. Therefore, the light receiving section 152 has a dynamic range three times as large as that when the observation light is directly received by the light receiving element without passing through the optical path deflecting section 140.
[0061]
As described above, when the light receiving unit of the solid-state imaging device 150 is a single light receiving unit 152a and directly receives the observation light with the light receiving element without passing through the optical path deflecting unit 140, the light receiving unit has an incident light amount of (2 / 3) It saturates at c. However, when the light receiving unit 152 includes the light receiving unit 152a and the light receiving unit 152b as in the present embodiment, the light receiving unit 152 is not saturated up to the incident light amount 2c. This means that the light quantity range in which the solid-state imaging device 150 can image is expanded, that is, the dynamic range is improved.
[0062]
The characteristic (A + B), which is the signal output characteristic of the light receiving section 152, has different characteristics depending on the incident light amount of the observation light between 0 and c and between c and 2c. When the incident light amount of the observation light is between 0 and c, electric charges are accumulated in the respective light receiving elements of the light receiving unit 152a and the light receiving unit 152b. Therefore, the slope of the characteristic (A + B) in the graph of FIG. The inclination with B is adjusted. Further, since the light receiving section 152a is in a saturated state when the incident light amount of the observation light is from c to 2c, electric charges are accumulated only in the light receiving element of the light receiving section 152b, and the characteristic (A + B) in the graph of FIG. The slope is equal to the characteristic B. Accordingly, when the incident light amount of the observation light is between 0 and c, the light receiving unit 152 of the present embodiment can obtain a higher signal output as compared with the case where the light receiving unit is a single light receiving unit 152a. In other words, the light receiving unit 152 of the present embodiment has high sensitivity. Further, when the incident light amount of the observation light is between c and 2c, a signal output can be obtained without saturation unlike the case where the light receiving unit is the single light receiving unit 152a. In other words, the light receiving unit 152 of the present embodiment has an expanded dynamic range.
[0063]
In the solid-state imaging device 150 of the present embodiment, a light receiving unit 152a and a light receiving unit 152b, which are two image areas, are arranged side by side along the longitudinal direction of the distal end of the electronic endoscope 100. Therefore, by providing the solid-state imaging device 150 of the present embodiment, the sensitivity of the solid-state imaging device to the dynamic range and the high luminance can be improved without increasing the diameter of the electronic endoscope or reducing the resolution of the observed image. Can be done.
[0064]
In the solid-state imaging device 150 of the present embodiment, the charge transfer path of the light receiving unit 152a and the light receiving unit 152b is formed by the horizontal transfer unit 154, which is a one-line charge-coupled device. Further, the horizontal transfer units 154 are arranged along the longitudinal direction of the distal end of the electronic endoscope 100. Therefore, the electric charges of the light receiving unit 152a and the light receiving unit 152b can be added without increasing the diameter of the electronic endoscope.
[0065]
The above is the embodiment of the present invention. The present invention is not limited to these embodiments, and can be modified in various ranges.
[0066]
In the present embodiment, the relationship between the signal output of the light receiving unit 152 and the incident light amount of the observation light is the characteristic (A + B) shown in FIG. 7, but this characteristic is not limited to that of the present embodiment. For example, the relationship between the intensity of the reflected light and the intensity of the transmitted light may be different such that the former has smaller characteristics than the latter. In order to make these characteristics different, in the optical path deflecting unit 140 of the present embodiment, a beam splitter 142a having a different splitting characteristic with respect to observation light may be disposed in the distal end of the electronic endoscope 100. In particular, when a beam splitter 142a having an intensity ratio of reflected light to transmitted light of 1: 1 is used, not only the dynamic range but also the linearity can be improved.
[0067]
In the embodiment of the present invention, different amounts of observation light are guided to the light receiving units 152a and 152b by the splitting characteristics of the beam splitter 142a with respect to the observation light, and the respective sensitivity characteristics are different. A light-reducing member such as an ND filter may be arranged on the front surface of one of the light-receiving sections to make the sensitivity characteristics for high luminance different. Also, the incident efficiency of the microlenses provided in each of the light receiving elements of the light receiving unit 152a and the incident efficiency of the microlenses provided in each of the light receiving elements of the light receiving unit 152b are made different from each other, and May have different sensitivity characteristics to high luminance.
[0068]
Further, in the embodiment of the present invention, the solid-state imaging device 150 is a monochrome CCD, but may be a color CCD in which a color filter is provided for each light receiving element. In this case, since it is not a frame sequential method, the RGB rotation filter 220 becomes unnecessary, and the solid-state imaging device is driven at the timing of charge accumulation / transfer different from that of the present embodiment.
[0069]
Further, in the embodiment of the present invention, the solid-state imaging device 150 has two image areas of the light receiving unit 152a and the light receiving unit 152b, but these image areas may be three or more.
[0070]
【The invention's effect】
As described above, the solid-state imaging device according to the present invention is configured such that, on a single semiconductor substrate that is formed to be long in a predetermined direction, each charge accumulated in at least two light receiving units arranged in different regions in the predetermined direction is used. It is added and output. Therefore, it is possible to output image information with an improved dynamic range without increasing the size of the apparatus or reducing the resolution in a direction orthogonal to the predetermined direction.
[0071]
Further, the electronic endoscope of the present invention includes a solid-state imaging device in which at least two light receiving sections are arranged in different regions in a predetermined direction on a single semiconductor substrate formed to be long in a predetermined direction, The respective electric charges accumulated in these light receiving units are added and output. Therefore, an image with an improved dynamic range can be output without increasing the diameter of the electronic endoscope or reducing the resolution. Therefore, it is possible to output image information capable of improving the dynamic range and obtaining a smooth image without increasing the burden on the patient or reducing the sharpness of the image.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an electronic endoscope apparatus including an electronic endoscope according to an embodiment of the present invention.
FIG. 2 is a side sectional view schematically showing an internal structure of a distal end portion of the electronic endoscope according to the embodiment of the present invention.
FIG. 3 is a top view schematically illustrating a configuration of a solid-state imaging device provided in a distal end portion of the electronic endoscope according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating a charge transfer operation of the solid-state imaging device.
FIG. 5 is a timing chart showing a period of imaging and transfer of the solid-state imaging device and a period of observation light incident on the solid-state imaging device.
FIG. 6 is a timing chart showing in detail a transfer operation of charges accumulated in the light receiving element during a period T of FIG. 4;
FIG. 7 is a graph showing a signal output characteristic with respect to an incident light amount of each of the light receiving elements provided in the light receiving unit.
[Explanation of symbols]
100 electronic endoscope
140 Optical path deflection unit
142a beam splitter
150 solid-state image sensor
152a, 152b light receiving unit
154a, 154b horizontal transfer unit
500 Electronic endoscope device

Claims (15)

A solid-state imaging device having a light-receiving unit in which a plurality of light-receiving elements for receiving light from an imaging target are arranged in a matrix on a single semiconductor substrate formed to be long in a predetermined direction,
At least two light receiving units including a first light receiving unit and a second light receiving unit in different regions in the predetermined direction,
A first transfer unit that is a transfer destination of the charge accumulated in the plurality of light receiving elements of the first light receiving unit;
At least two transfer units including: a second transfer unit that is a transfer destination of the charge accumulated in the plurality of light-receiving elements included in the second light-receiving unit;
Addition for adding the charges transferred to the at least two transfer units including the charges transferred to the first transfer unit and the charges transferred to the second transfer unit, and outputting the added charges to the outside And an output unit. 2. The solid-state imaging device according to claim 1, wherein an arrangement of the plurality of light receiving elements included in each of the at least two light receiving units is the same. Each of the charges stored in each of the at least two light receiving units is transferred to each of the at least two transfer units for each of the charges stored in the light receiving element row in the predetermined direction,
3. The solid-state imaging device according to claim 2, wherein the addition output unit adds the transferred electric charges in each row of the light receiving elements and outputs the added electric charges to the outside. The solid-state imaging device according to claim 3, wherein the at least two transfer units are included in elements arranged in a line in the predetermined direction. A light beam splitting unit that splits a light beam from the imaging target into a first light beam and a second light beam is disposed on the front surface of the light receiving unit, and the first light beam is guided to the first light receiving unit, The solid-state imaging device according to claim 1, wherein the second light beam is guided to the second light receiving unit. The light beam splitting means is a beam splitter, the first light beam is a light beam reflected by the beam splitter, and the second light beam is a transmitted light beam by the beam splitter. Solid-state imaging device. The solid-state imaging device according to any one of claims 1 to 4, wherein a dimming unit is disposed on a front surface of one of the first light receiving unit and the second light receiving unit. . A solid-state imaging device having a light receiving section in which a plurality of light receiving elements for receiving reflected light from an observation target are arranged in a matrix on a single semiconductor substrate formed long in a predetermined direction is provided in a tip portion. An electronic endoscope provided with
The solid-state imaging device, at least two light receiving units including a first light receiving unit and a second light receiving unit in different regions in the predetermined direction,
A first transfer unit that is a transfer destination of the charge accumulated in the plurality of light receiving elements of the first light receiving unit;
At least two transfer units including: a second transfer unit that is a transfer destination of the charge accumulated in the plurality of light-receiving elements included in the second light-receiving unit;
Addition for adding the charges transferred to the at least two transfer units including the charges transferred to the first transfer unit and the charges transferred to the second transfer unit, and outputting the added charges to the outside An output unit;
Further, the electronic endoscope is arranged so that a longitudinal direction of the semiconductor substrate coincides with a longitudinal direction of the distal end portion. The electronic endoscope according to claim 8, wherein each of the at least two light receiving units is positioned approximately equivalently optically. 10. The electronic endoscope according to claim 8, wherein an arrangement of the plurality of light receiving elements included in each of the at least two light receiving units is the same. Each of the charges stored in each of the at least two light receiving units is transferred to each of the at least two transfer units for each of the charges stored in the light receiving element row in the predetermined direction,
The electronic endoscope according to claim 10, wherein the addition output unit adds the transferred electric charges of each row of the light receiving elements and outputs the added electric charges to the outside. The electronic endoscope according to any one of claims 8 to 11, wherein the at least two transfer units are included in elements arranged in a line in the predetermined direction. A light beam splitting unit that splits a reflected light beam from the observation target into a first light beam and a second light beam is disposed on the front surface of the light receiving unit, and the first light beam is guided to the first light receiving unit, The electronic endoscope according to any one of claims 8 to 12, wherein a second light flux is guided to the second light receiving unit. 14. The beam splitter according to claim 13, wherein the beam splitter is a beam splitter, the first beam is a beam reflected by the beam splitter, and the second beam is a beam transmitted by the beam splitter. Electronic endoscope. 13. The electronic endoscope according to claim 8, wherein a dimming unit is disposed on a front surface of one of the first light receiving unit and the second light receiving unit.

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