JP2000358198A - Solid-state imaging device - Google Patents

Abstract

(57) [Problem] To provide a solid-state imaging device having a planar configuration, which can increase the ratio of apertures despite its small size. SOLUTION: One pixel area PJ _{, K} is divided into nine small blocks, and one block includes a photodiode 12A and a pulse generator 20A. The other eight blocks include counters 51 to 58 for obtaining the first to eighth bit outputs, respectively. Counters 51-5
The first to eighth bit outputs obtained from 8 are output to the outside via the switch SW in accordance with ON / OFF control by the horizontal scanning circuit 34. Vertical scanning circuit 44
Selects a pixel region group in the row direction included in the solid-state imaging device SID.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solid-state imaging device for immediately extracting a photoelectrically converted electric signal as a digital signal.

[0002]

2. Description of the Related Art As is well known, by performing signal transmission and various kinds of signal processing in the form of digital signals, deterioration of the SN ratio can be extremely reduced. From this point of view, even in an imaging apparatus, an attempt has been made to digitize a video signal at an early signal processing stage as much as possible and then perform various processes.

However, in a conventional imaging apparatus, even when a photoelectrically converted signal is converted into a digital signal as soon as possible, each analog information obtained from a pixel of a solid-state imaging device is once converted into time-series analog information. After being taken out, it was converted to a digital signal by an AD (analog-digital) converter.

[0004] As long as such a configuration is adopted, analog signal processing in an image sensor before performing AD conversion is the same as before, and the problem there remains without being solved at all. That is, there is a defect that good imaging cannot be performed, for example, various types of noises are superimposed and the SN ratio cannot be sufficiently increased.

In view of the above points, the present applicant has already proposed a solid-state imaging device configured to directly convert an electric signal of each pixel photoelectrically converted in each pixel into a digital signal and perform signal processing ( Japanese Patent Publication No. Hei 7-99868 “Solid-state imaging device”).

The solid-state imaging device according to the above application digitally measures the number of arriving photons (photons) and sends out a digital signal for each pixel, and has a configuration as shown in FIG. ing. That is, first, a plurality of optical sensor units 8A are linearly arranged to form a line sensor,
This line sensor is sliced into a thickness of about 10 μm, and a predetermined number of the line sensors are vertically attached to each other to constitute a solid-state imaging device capable of capturing a two-dimensional image. Here, the vertical scanning circuit 16 has a function of specifying one of the horizontal scanning circuits 14 provided for each line sensor and specifying a horizontal scanning line.

As described above, in the configuration of FIG. 1, when arranging the optical sensor units 8A in a matrix on a two-dimensional plane, the line sensors are electrically insulated from each other and overlapped with each other. It enables dimensional scanning.

[0008]

However, in the conventional solid-state imaging device as shown in FIG. 1, in order to capture a two-dimensional image, the thinned line sensors must be stacked while being electrically insulated. Therefore, there is a problem that not only high technology is required but also production efficiency is not improved.

In order to make it possible to capture a two-dimensional image without stacking the thinned line sensors, a planar substrate on which a photosensor unit, a counter, a horizontal scanning circuit, a vertical scanning circuit, etc. are all mounted. I thought about adopting a configuration.

[0010] However, when such a plane configuration is adopted, an optical sensor and many other circuits must be included in a plane area corresponding to one pixel, so that it is necessary to directly detect incident light. There is a problem that the area, that is, the ratio of the openings, becomes very small.

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a solid-state imaging device having a planar configuration which can improve production efficiency without requiring advanced technology in view of the above points.

It is a second object of the present invention to provide a solid-state imaging device having a planar configuration, which can increase the ratio of the openings despite its small size.

[0013]

In order to achieve the above object, a solid-state imaging device according to the present invention comprises a light receiving means for transmitting a pulse-like signal corresponding to the number of incident photons on a two-dimensional substrate. A plurality of solid-state imaging devices arranged in a plane area corresponding to one pixel, the light receiving means,
Means for counting the pulse signal sent from the light receiving means.

Further, in the solid-state imaging device described above, it is possible to further include a unit for increasing an aperture ratio of the light receiving unit. Here, as means for increasing the aperture ratio of the light receiving means, a plurality of pixel regions forming an imaging surface,
An optical fiber for connecting the light receiving means corresponding to each of these pixel regions can be used. Further, as a means for increasing the aperture ratio of the light receiving means, an enlargement optical system disposed after the imaging lens, and a microlens attached to an incident surface of the light reception means for introducing output light from the enlargement optical system It is also possible to use further,
As means for increasing the aperture ratio of the light receiving means, a photoelectric conversion film may be attached over the entire incident surface of one pixel region, and a charge collecting electrode may be arranged between the photoelectric conversion film and the light receiving means. .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 In describing a solid-state imaging device according to the present embodiment,
First, a circuit configuration according to the present embodiment will be described, and then a specific pixel arrangement on a substrate will be described.

FIG. 2 shows a light detection circuit for one pixel in the solid-state imaging device. In this figure, 12A is a photodiode serving as a light detecting element, 11A is an FET switch for discharging accumulated charges, and 9A is an ON (ON) resistance for determining a discharge time constant. 20A is a pulse generation circuit, which outputs a pulse when the output voltage from the photodiode 12A exceeds a threshold voltage,
A reset pulse for returning the photodiode 12A to the initial state is generated. 51 to 58 are first bit outputs
This is a binary counter for obtaining the eighth bit output.

FIG. 3 shows a line sensor including a light detection circuit for one pixel shown in FIG. This drawing shows an embodiment in which a line sensor is formed on a single substrate according to a normal IC process.

In FIG. 3, 9A to 9N are on-resistances for determining a discharge time constant of accumulated charges, 20A to 20N are pulse generation circuits, and 30A to 30N are pulse generation circuits 20A to 20N.
A counter circuit (specifically, flip-flops are cascaded) that counts the pulse signals sent from N.

Reference numerals 12A to 12N denote photodiodes, and these photodiodes are arranged in a line on a light receiving surface from which photons arrive. Instead of the photodiodes 12A to 12N, a photoelectric conversion element such as a photoconductive film or a high-speed photomultiplier (for example, an avalanche photodiode, or a photodetector composed of a combination of a photocathode and a microchannel plate) is used. Can also be used.

11A to 11N are discharge switches for resetting the electric charges stored in the photodiodes 12A to 12N (specifically, FET switches are used as shown in FIG. 2). . Reference numeral 24 denotes a horizontal scanning circuit which sequentially reads out digital count values from the counter circuits 30A to 30N and simultaneously resets them. As a method for performing this reading, it is preferable to use a conventionally known address switching method.

When the line sensor shown in FIG. 3 is operated, first, a pulse signal corresponding to the number of incident photons is introduced into the counter circuits 30A to 30N for 1/30 second corresponding to one frame time, and the counting is completed. At this point, each of the counter circuits 3 is used by using the horizontal scanning circuit 24.
The count values are sequentially read from 0A to 30N. Then, after reading the count value, each of the counter circuits 30A to 30A
N is reset to zero, and the same operation is repeated thereafter. Thus, the illuminance on the light receiving surface can be directly converted into a digital signal for each pixel and output.

A two-dimensional sensor is constructed by arranging the line sensors shown in FIG. 3 in parallel (not shown).

FIG. 4 is a plan view schematically showing a substrate configuration in the present embodiment. In this figure, SID is a solid-state imaging device (Solid Imaging Device) formed on a flat substrate.
Device), and includes pixel regions P _{1,1 to} P _{M, N} of M rows and N columns arranged in a matrix. On the right side of the figure,
One pixel area P _{J, K} is drawn in an enlarged manner. Also, 3
4 is a horizontal scanning circuit, 44 is a vertical scanning circuit, and SW is a switch controlled by the horizontal scanning circuit 34.

As shown on the right side of FIG. 4, one pixel area P _{J, K} is divided into nine small blocks, and a photodiode 12A and a pulse generation circuit 20A (see FIG. 2) are provided in the center block. It is included. The eight peripheral blocks surrounding the central block include counters 51 to 58 (see FIG. 2) for obtaining the first to eighth bit outputs, respectively. The first to eighth bit outputs obtained from the counters 51 to 58 are output to the outside via the switch SW in accordance with ON / OFF control by the horizontal scanning circuit 34. At this time, the vertical scanning circuit 44 selects a pixel region group in the row direction (horizontal direction in FIG. 4) included in the solid-state imaging device SID. That is, one pixel area P _{J, K} is selected by the horizontal scanning circuit 34 and the vertical scanning circuit 44, and this pixel area P _{J, K} is selected.
Each bit output is obtained from _{J and K.}

FIG. 5 is a diagram for explaining a state in which the vertical scanning circuit 44 selects a pixel area group in the row direction. In this figure, the same components as those in FIG. 4 are denoted by the same reference numerals. As is apparent from FIG.
FET switches are respectively connected between the output terminal of 58 and the output extraction line, and each FET switch is turned on by a gate control signal output from the vertical scanning circuit 44.
/ OFF. Thus, from the selected specific pixel area PJ _{, K} , the first bit output B1 to the eighth bit output B
8 is supplied to the switch SW (FIG. 4). FIG. 6 illustrates this state from another viewpoint.

In this embodiment, a light receiving means is arranged at a central portion in a plane area corresponding to one pixel, and means for counting the pulse-like signal sent from the light receiving means are arranged so as to surround the light receiving means. Although the example has been described, the arrangement method is not limited to this, and various variations can be considered.

In the present embodiment, the photodiode and other plural circuits are formed in a planar manner, so that the first
A parallel signal composed of the bit output B1 to the eighth bit output B8 can be output sequentially (that is, in time series) for each pixel.

Embodiment 2 In Embodiment 1 described above, the solid-state imaging device SID formed on a flat substrate is described.
The aperture ratio as the image sensor is limited only by the planar configurations shown in FIGS. 4 to 6.

Therefore, in the second embodiment described here,
In order to further increase the aperture ratio, as shown in FIG. 7, the photoelectric conversion film 70 is attached to the incident light beam side of the solid-state imaging device SID, so that the substantial aperture ratio is set to 100%.
That is, a pixel electrode 72 for collecting electric charges is provided on the photodiode 12A, and at the same time, the photoelectric conversion film 70 is laminated on the pixel electrode 72.

With such a configuration, electrons (or holes) converted by the photoelectric conversion film 70 can be collected only in the photodiode portion, and the optical signal can be used without waste.

Embodiment 3 In Embodiment 2 described above, since the imaging surface is large, a large photographic lens is required. On the other hand, there is no idea of intentionally increasing the size of the entire image pickup apparatus. Therefore, there was no idea of using an enlargement optical system after the photographing lens. However, in the present image sensor SID which performs processing for each pixel, the ratio of the photodiode (photosensitive portion) to the area of one pixel region becomes very small, and the image sensor itself becomes large. It will become. In this case, a large photographic lens may be used, but the lens itself becomes large, and a special lens must be designed.

Therefore, in the third embodiment described here,
As shown in FIG. 8, an enlargement optical system 68 is provided in front of the image sensor SID, and a microlens 66 is provided immediately before the image sensor SID. It is configured to concentrate only on

That is, an image is enlarged by an enlargement optical system 68 corresponding to the size of the image sensor SID while using a small photographic lens 60 as usual and keeping the normal focal plane small. A micro lens 66 is provided for each pixel in order to collect light only at a necessary portion in the region.

In the third embodiment, since the conventionally used small photographing lens 60 can be used and the incident light can be used without waste, it is apparently photographed with a small image pickup device and another processing circuit is used. The same effect as when image processing is performed can be obtained. In addition, a great merit that image processing can be freely performed within one pixel is added.

As described above, the image formed by the photographing lens 60 is enlarged to a required size by the enlargement optical system 68,
Then, by condensing the light on the photodiode portion by the micro lens 66, it is possible to collect light information only in the light sensitive portion in each pixel, and at the same time, the photographing lens can use an ordinary general small lens, The special effect is obtained.

Fourth Embodiment In the third embodiment shown in FIG. 8, the image pickup element S is moved from the first focal plane (in FIG. 8, it is described as "normal focal plane").
There is a problem that the distance to the ID becomes long.

Therefore, in the fourth embodiment, in order to reduce the size of the entire image pickup unit, as shown in FIG.
One end face of the TF is connected to the photodiode in each pixel area of the image sensor SID, and the other end face is bundled as small as possible so that the relative positional relationship of each optical fiber OPTF does not change. I do. This allows
Since the imaging surface can be made smaller, the conventional small photographing lens 60 can be used.
And the incident light can be guided to the light receiving portion (photodiode) of each pixel without waste. As a result, the distance between the taking lens 60 and the image sensor SID can be made shorter than in the case of FIG.

As described above, in the fourth embodiment, one end face of the optical fiber OPTF is arranged so as to be equal to the pitch of the pixel area, and the other end face is arranged as small as possible. The light passed through each optical fiber OPTF is guided to a predetermined photodiode without waste.

[0039]

As described above, according to the present invention, it is possible to realize a solid-state imaging device having a planar configuration which can improve the production efficiency without requiring advanced technology.

Further, according to the present invention, it is possible to realize a solid-state imaging device having a planar configuration in which the ratio of openings can be increased despite its small size.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a conventional technique related to the present invention.

FIG. 2 is a circuit diagram showing a light detection circuit for one pixel of the solid-state imaging device according to the present invention.

FIG. 3 is a configuration diagram of a line sensor including a photodetection circuit for one pixel shown in FIG. 2;

FIG. 4 is a plan view schematically showing a substrate configuration in the first embodiment.

FIG. 5 is a plan view schematically showing a substrate configuration in the first embodiment.

FIG. 6 is a plan view schematically showing a substrate configuration in the first embodiment.

FIG. 7 is an explanatory diagram showing a second embodiment.

FIG. 8 is an explanatory diagram showing a third embodiment.

FIG. 9 is an explanatory diagram showing a fourth embodiment.

[Explanation of symbols]

9A to 9N On-resistance 12A to 12N Photodiode 20A to 20N Pulse generation circuit 30A to 30N Counter circuit 34 Horizontal scanning circuit 44 Vertical scanning circuit 51 to 58 Binary counter SID Solid-state imaging device P _{J, K} formed on a flat substrate One pixel area

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Miho Nakayama 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation F-Term in the Broadcasting Research Institute (reference) 4M118 AA10 AB01 BA05 CA02 CA14 DD09 DD12 GD03 HA23 5C024 AA01 CA12 DA07 EA04 FA01 FA11 GA01 GA04 GA31 HA16

Claims (5)

[Claims] 1. A solid-state imaging device in which a plurality of light receiving means for transmitting a pulse-like signal corresponding to the number of incident photons are two-dimensionally arranged on a flat substrate, wherein a flat area corresponding to one pixel is provided. Wherein the light receiving means and a means for counting the pulse-like signal transmitted from the light receiving means are arranged therein. 2. The solid-state imaging device according to claim 1, further comprising: a unit configured to increase an aperture ratio of said light receiving unit. 3. The solid-state imaging device according to claim 2, wherein, as means for increasing an aperture ratio of the light receiving means, a plurality of pixel areas forming an imaging surface and the light receiving means corresponding to each of the pixel areas. A solid-state imaging device, characterized by using an optical fiber for connecting the two. 4. The solid-state imaging device according to claim 2, wherein, as means for increasing the aperture ratio of said light receiving means, an enlargement optical system disposed downstream of an imaging lens and output light from said enlargement optical system are introduced. And a microlens attached to the incident surface of the light receiving means. 5. The solid-state imaging device according to claim 2, wherein a photoelectric conversion film is attached over an entire incident surface of one pixel region as a means for increasing an aperture ratio of the light receiving unit, and the photoelectric conversion film and the light receiving unit are attached. And a charge collecting electrode disposed between the two.