JP3149909B2 - Image sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor, and more particularly, to an image sensor using a TDI scan that can scan at high speed.

[0002]

2. Description of the Related Art A CCD line sensor is a one-dimensional sensor in which photo sensors for receiving image light are arranged in a line. When a two-dimensionally widened image is captured by the CCD line sensor, the CCD line sensor or the subject is moved to sequentially capture the subject one line at a time. Scanners using such a CCD line sensor are conventionally used in copiers, product inspections (FA), and the like.

[0003] However, when photographing a subject moving at high speed by the CCD line sensor, or when performing high-speed scanning such as photographing the subject by moving the CCD line sensor at high speed, the electric charge of each line is rapidly increased. Since the accumulation and the transfer must be repeated, the time during which the electric charge can be accumulated per line is shortened. For this reason, there is a problem that the amount of light of the obtained image is insufficient.

Therefore, when scanning a subject at high speed, TDI (Time Delay Integral) is used.
) sensor is used. TDI sensor is CC
The D line sensors are arranged in a plurality of stages in the scanning direction, and transfer the signal charges accumulated in the CCD of each line to the CCD of the next line in synchronization with the movement of the image. As a result, the signal charges are superimposed on the plurality of CCDs, and as a result, an image that sufficiently satisfies the light quantity can be obtained even in high-speed scanning.

[0005]

However, the above T
The scanning speed is also limited in the DI sensor. One of the factors is that there is a limit to the speed at which signal charges accumulated in the CCD can be shifted to the outside.
That is, the signal charge of each line is finally swept out as a serial analog signal to the outside and converted into a digital signal by the A / D converter. Cannot be raised above a certain limit.

Therefore, conventionally, in order to improve the scanning speed, a single line is divided into a plurality of patches, and charges accumulated in each patch are swept out as a serial analog signal, and A provided for each patch is provided. In some cases, a digital signal is converted by a / D converter. However, even in this case, there is a limit to the width that can be divided as a patch, and it is insufficient when high-speed scanning is desired.

[0007] The present invention has been made in view of such circumstances, and has as its object to provide an image sensor that enables high-speed scanning.

[0008]

According to the present invention, in order to achieve the above object, a photo sensor for receiving image light is arranged in a line, and a plurality of photo sensors arranged in a line are arranged in a scanning direction. The arrayed light receiving units are provided for each column in the scanning direction, and transfer the charges read from the photosensor in the scanning direction in synchronization with the scanning speed, and read the same read from the same column of photosensors. A column-direction charge transfer unit for superimposing a charge indicating an image, a plurality of line-direction charge transfer units for transferring the charge sent from the column-direction charge transfer in the line direction every predetermined column, and the line-direction charge transfer unit A digital signal conversion unit that converts a plurality of charge trains sent from the digital signal into digital signals, respectively, based on the digital signal output from the digital signal conversion unit. An image signal generating unit for generating an image signal, in that it consists of are characterized.

According to the present invention, the electric charge read from the photosensor is transferred in the scanning direction in synchronization with the scanning speed, and the electric charge indicating the same image read from the same row of photosensors is superimposed. Then, the charges transferred in the scan direction are generated in a row of charge in the line direction every predetermined column, and the charges transferred in each row in the scan direction are transferred in the line direction by a plurality of charge rows. Then, each charge train is independently converted into a digital signal, and an image signal is generated based on the digital signal.

[0010] This makes it possible to convert a charge sequence representing an image of one line into a digital signal by a plurality of processing circuits, thereby reducing the amount of data that must be processed by one processing circuit. The scanning speed can be increased. Further, by arranging the photosensors at a predetermined distance or more in the light receiving section,
The light receiving surface of each photo sensor can be enlarged by shifting the position of the peripheral circuit, and the amount of light received on each light receiving surface can be increased.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an image sensor according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of a sensor unit of an embodiment of an image sensor according to the present invention. The sensor unit 10 shown in FIG. 1 is a circuit board in which photo sensors arranged in a line are arranged in multiple stages, and the technology of a TDI scanner sensor is basically applied. As shown in FIG.
Is vertically above the subject 11 (in the direction indicated by the arrow A)
, And scans the image of the subject vertically downward. Then, the signal charges obtained by the photosensors of each line are sequentially transferred in the vertical direction (the direction of the transfer of the signal charges indicated by arrow A ') in synchronization with the scanning speed, and the signal charges of the same image are transferred in the same column. The signal charges are sequentially added by the photo sensor to increase the signal charge.

The sensor section 10 is divided into patches 12, 12, 12,... For parallel processing of signal charges for one line obtained by the photosensor by a plurality of processing systems. Each patch 12 is constituted by the same circuit having the same element arrangement, and transfers signal charges separately for each patch 12. As described above, the signal charges which are sequentially transferred in the vertical direction and reach the final stage are then transferred in the horizontal direction (arrow B in the drawing) in each patch.
(In the direction indicated by), are output to an A / D converter 14 provided at the subsequent stage provided for each patch 12, and are converted into digital signals. Therefore, the data amount that the A / D converter 14 has to process is smaller than in the case where it is not divided into patches, so that the data processing speed can be increased and the scan speed can be increased. Also,
As described later, the A / D converter 14 in each patch 12
Is constituted by a plurality of A / D converters, and data is divided and processed in each patch 12, so that the scanning speed can be further increased.

Next, the configuration of the image sensor according to the present invention will be described in detail by focusing on one patch 12. FIG. 2 is an enlarged view of a part of the configuration of the patch 12 of the sensor unit 10. In the patch 12, a plurality of photo sensors 20, 20, 20,... And a plurality of vertical CCD shift registers 22, 22, 22,. The array of the photosensors 20, 20, 20,...
Photosensors 20, 20, shown in the area of 12A ...
With the arrangement of 20... As a basic arrangement, they are arranged vertically and horizontally repeatedly.

Focusing on the section 12A where the patch 12 is located, the photosensors 20, 20, 20,... Are arranged diagonally. Specifically, FIG. 3 in which a part of the section 12A is enlarged.
As shown in (1), the photosensors 20 are sequentially arranged at positions separated by one pixel in the line direction and S lines (stages) in the scanning direction with respect to the photosensors 20 of a certain line. Note that the signal charges accumulated in each cell are shifted by one cell every time the image of the subject moves by one cell width, and the signal charges of the image of the next line are captured by each photosensor 20. The number of lines in the scanning direction is vertical C
It is determined by the number of cells of the CD shift register.

Although the arrangement of the photosensors 20 is not essentially related to increasing the scanning speed, for example, when a pinhole is inserted in front of the photosensor in order to increase the resolution of an image. It is especially effective for
In this case, it is necessary to arrange adjacent pinholes at a certain interval, and accordingly, an array is provided in which photosensors as shown in FIG.
The arrangement of the photosensors 20 is not limited to this, and may be adapted to the arrangement of the pinhole holes. Also,
When only high-speed scanning is intended, photo sensors may be provided in all CCD cells as in the related art.

Further, by arranging the photosensors apart from each other regardless of whether pinholes are used, it is possible to increase the light receiving surface of each photosensor 20 by shifting the arrangement of elements around each photosensor 20. Therefore, the amount of received light can be increased. The image light incident on each of the photosensors 20 arranged as described above is photoelectrically converted into a photocurrent. Then, this photocurrent is stored in a storage electrode (not shown) to become signal charges, and after the storage time has elapsed, a vertical gate C is generated by a shift gate pulse.
The data is transferred to the CD shift register 22. And vertical CC
The signal charges transferred to the D shift register 22 are sequentially transferred in the vertical direction by a vertical transfer pulse synchronized with the scan speed. In the CCD cells to which the signal charges are transferred from each photosensor 20, the signal charges of the image on the same line are sequentially added.

The signal charges transferred to the vertical CCD shift register 22 in this manner are finally transferred to the horizontal CCD shift register in the horizontal direction. FIG. 4 is a diagram showing a configuration of a horizontal CCD shift register provided after the patch 12. As shown in the figure, horizontal CCD shift registers 24, 24, 24,... Are provided in the last horizontal transfer section 12B showing the basic arrangement of the photosensors 20, and the photosensors 20, 20, 20,. It is arranged for each of the lines.

The signal charge transferred to each vertical CCD shift register 22 is transferred to the last photosensor 20 in each column.
Are provided to these horizontal CCD shift registers 24, 24, 24,... And sequentially shifted in the horizontal direction by horizontal transfer pulses. The signal charges swept out of the horizontal CCD shift registers 24, 24, 24,... Are converted into voltage signals by the floating capacitors 26, 26, 26,. 28, 28, 28, ...
And is input to the A / D converters 30, 30, 30,... Then, the A / D converters 30, 30, 30,...
Is converted into a digital signal.

Thus, also in each patch 12,
A / D converters 30, 30, 30,... Provided separately for each photo sensor 20 on the same line in the basic arrangement
Each of the A / D converters 30, 30, 30,
Can reduce the amount of data to be processed, and can increase the scanning speed. As described above, one line of image data is divided into a plurality of pixel data by the plurality of horizontal CCD shift registers 24, 24, 24,.
Are output from the D converters 30, 30, 30,..., It is necessary to delay the data output from each of the A / D converters 30, 30, 30,. .

Therefore, the CPU 32 shown in FIG.
The digital signal output from the converter is input to the memory 3
4, and once one line of pixel data is obtained, these pixel data are read out of the memory to form one line of image data and output to the subsequent processing circuit. Here, focusing on the image of a certain line, the signal charges of each pixel of this image move the CCD cells on the same line of the vertical CCD shift register 22 in the scanning direction.
When the horizontal CCD shift registers 24, 24, 24,... Of the horizontal transfer section 12B are reached, the horizontal shift registers 24, 24, 24,.
Moved to Therefore, between pixels at different positions of the horizontal CCD cyst register 24, the time for obtaining pixel data is delayed by the amount of transfer between the pixels.

FIG. 5 shows the photo sensor 20 in the horizontal transfer section.
It is the figure which showed the arrangement | sequence of 20, 20, .... As shown in the figure, the Nth photo sensor in the vertical direction and the Mth photosensor in the horizontal direction from the upper left are (N, M). Pixel data obtained from the signal charge at the position of each photosensor at the time T _i is defined as (N, M, T _i ). At the time T _i , the signal charge of the image of interest is shifted to the uppermost photosensor (1,
M), the pixel data at the position of these photosensors (1, M) in this image is (1, M,
T _i ) (M is an integer from 1 to m).

Next, at time T _{i + s} , the signal charge of the image of interest is transferred onto the line of the photosensor (2, M). Note that _Ti is the time at which the signal charge is shifted by one line in the scanning direction each time i increases by one, and S represents the interval in the scanning direction of the photosensor 20 by the number of lines as shown in FIG. Value. Therefore, the pixel data at the position of these photosensors (2, M) of the image of interest is obtained as (2, M, T _{i + s} ).

Similarly, at the time T _{i + s (n−1)} , the signal charge of the image of interest is the last stage of the photo sensor (n,
The pixel data at the position of these photosensors (n, M) of the image of interest is transferred as (n, M, _{Ti + s (n-1)} ). After all, the pixel data on the same line is composed of (N, M, T _{i + s (N−1)} ) pixel data. Here, N is an integer from 1 to n, and M is an integer from 1 to m.

Then, the CPU 32 extracts the pixel data indicated by (N, M, T _{i + s (N−1)} ) from the pixel data recorded in the memory 34, thereby obtaining one line of image data. (Image signal). Note that the above description is about processing in each patch 12, but image data of the entire sensor unit 10 can be obtained by combining image data obtained in each patch 12.

As described above, in the above embodiment, the pixel data of the image on the same line is stored in each horizontal CCD shift register 24,
, 24, 24,... At predetermined time intervals.
The horizontal transfer section 12B shown in FIG. 6 is configured as a horizontal transfer section 12C shown in FIG.
.. May be configured to be transferred to the last line by the CD shift registers 22, 22, 22,. In this case, since the signal charges of the image on the same line are simultaneously transferred to the horizontal CCD shift registers 24, 24, 24,..., Each pixel data of the image on the same line is obtained at the same time.

[0026]

As described above, according to the image sensor of the present invention, the electric charge read from the photosensor is transferred in the scanning direction in synchronization with the scanning speed, and the same image read from the same row of photosensors is displayed. Superimpose charge. Then, the charges transferred in the scan direction are generated in a row of charge in the line direction every predetermined column, and the charges transferred in each row in the scan direction are transferred in the line direction by a plurality of charge rows. Then, each charge train is independently converted into a digital signal, and an image signal is generated based on the digital signal. As a result, a charge sequence representing an image for one line can be converted into a digital signal by a plurality of processing circuits, so that the amount of data that must be processed by one processing circuit can be reduced, and the scanning speed can be reduced. Can be faster.

Further, by arranging the photosensors at a predetermined distance or more in the light receiving portion, the light receiving surface of each photo sensor can be enlarged by shifting the position of the peripheral circuit, and the light receiving amount on each light receiving surface can be increased. Can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a sensor unit of an embodiment of an image sensor according to the present invention.

FIG. 2 is an enlarged view of a configuration of a part of a patch of a sensor unit.

FIG. 3 is an enlarged view of a part of a predetermined section of the patch;

FIG. 4 is a diagram illustrating a horizontal CC provided after each patch;
FIG. 3 is a diagram illustrating a configuration of a D shift register.

FIG. 5 is a diagram illustrating an array of photosensors in a horizontal transfer section in a patch.

FIG. 6 is a diagram illustrating a horizontal CC provided after each patch;
FIG. 3 is a diagram illustrating a configuration of a D shift register.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Sensor part 11 ... Subject 12 ... Patch 14 ... A / D converter 20 ... Photo sensor 22 ... Vertical CCD shift register 24 ... Horizontal CCD shift register 26 ... Floating capacitor 28 ... Preamplifier 30 ... A / D converter 32 ... CPU 34 ... Memory

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-46373 (JP, A) JP-A-57-166767 (JP, A) JP-A-4-56461 (JP, A) JP-A-1- 302974 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 1/04-1/207 H04N 1/024-1/036

Claims (2)

(57) [Claims] 1. A photo sensor for receiving image light is a scan sensor.
A light receiving unit in which a plurality of photo sensors arranged in the scanning direction are arranged in a line direction perpendicular to the scanning direction, and a plurality of photo sensors arranged in the scanning direction are provided for each column in the scanning direction. with transfers to read a in synchronization with the scan speed scanning direction charge from the scan direction charge transfer section for superimposing a charge indicating the same picture read from the same column of the photo sensor, the scan direction charge transfer section A plurality of line-direction charge transfer units that transfer the charges sent from the line direction in every predetermined column, and a digital signal conversion unit that converts each of the plurality of charge trains sent from the line-direction charge transfer unit into a digital signal. An image signal generation unit that generates an image signal based on the digital signal output from the digital signal conversion unit. The image sensor according to claim. 2. The image sensor according to claim 1, wherein the photo sensors of the light receiving section are arranged at a predetermined distance or more.