JP2002198506A - Solid-state image pickup element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pickup element which performs efficient image pick-up operation by only using the signal charges for effective image pickup areas without reading out useless signal charges. SOLUTION: This solid-state image pickup element has a read-out gate section 130 which reads out the signal charges stored in each photosensor of an image pickup section 110 to each transfer gate of a horizontal transfer register section 120. The gate section 130 is horizontally divided into three reading-out gate sections 130L, 130C, and 130R. The signal charges in three sensor rows 110L, 110C, and 110R are selectively read out to the horizontal transfer register section 120 by selectively controlling the divided reading-out gate sections 130L, 130C, and 130R by controlling the 'H' and 'L' of three read-out gate signals ROGL, ROGC, and ROGR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device such as a linear sensor or area sensor using a CCD, and more particularly to a solid-state imaging device capable of performing an efficient imaging operation using signal charges for an effective imaging region. The present invention relates to an imaging device.

[0002]

2. Description of the Related Art Conventionally, a CCD linear sensor as shown in FIG. 2 has been known as this type of solid-state imaging device.
The CCD linear sensor includes an imaging unit 10 having a plurality of photosensors for accumulating signal charges corresponding to the amount of received light, a horizontal transfer register unit 20 for transferring the signal charges accumulated in each photosensor of the imaging unit 10, and And a read gate (RO) for reading out signal charges accumulated in each photosensor of the imaging unit 10 to each transfer gate of the horizontal transfer register unit 20.
G) section 30.

FIG. 3 is a timing chart showing the operation of the CCD linear sensor shown in FIG. Imaging unit 1
Each of the photosensors 0 is provided with a photodiode in a semiconductor substrate, and accumulates signal charges corresponding to the amount of received light by photoelectric conversion of the photodiode.
In addition, the read gate unit 30 receives the read gate signal φ
It is driven by the ROG and performs an operation of reading signal charges accumulated in each photosensor of the imaging unit 10. That is, at the timing when the read gate signal φROG is set to “H”, the signal charges accumulated in each photosensor of the imaging unit 10 are read to each transfer gate of the horizontal transfer register unit 20. The horizontal transfer register unit 20 sequentially transfers signal charges read from each photosensor in accordance with the two-phase register transfer signals φ1 and φ2.

[0004] The signal charges transferred by the horizontal transfer register section 20 are output to a charge-to-voltage conversion section (FD; floating diffusion) 40 of an output section and converted into a voltage signal. This voltage signal is further sent to a signal processing circuit via a buffer or the like, and is subjected to predetermined signal processing. In such a linear sensor, signal charges that are no longer required in the imaging unit 10, the horizontal transfer register unit 20, and the readout gate unit 30 are respectively supplied to the overflow drain 50 at a predetermined timing.
Swept away.

[0005]

By the way, when an image is picked up by the above-described linear sensor, even if the pixel size of a document or the like to be scanned is small, the linear sensor reads out information of all areas. . For example, 600
In the case of a 0 pixel linear sensor as an example, the horizontal scanning is completed by transferring the horizontal transfer register 6000 times.
That is, since the linear sensor reads out a portion without a document and dummy information not required by the user, the scanning period becomes longer. Note that this is not limited to the linear sensor, and the same applies to the area sensor.

As described above, in the conventional solid-state imaging device,
Since all the pixel information within the angle of view determined by the imaging unit and the objective lens is read, if the image information necessary for the user exists only in a certain limited area, for example, signal processing for performing signal processing It was necessary to separately prepare an application or the like and perform image processing such as trimming. In addition, the user generally expects high-speed reading when the required angle of view of the pixel information is small. However, in the conventional solid-state imaging device, since the pixel information of all areas is read out, if the charge transfer speed and the scanning speed in the transfer register unit are constant, the pixel information is small despite the small amount. There is a problem that quick reading is difficult. In addition, if the charge transfer speed and the scanning speed in the transfer register unit are increased, the reading time can be reduced. However, high-frequency noise generated by the MOS transistor in the output unit, dull signal waveforms, crosstalk, and the like may cause significant deterioration in image quality.

An object of the present invention is to provide a solid-state imaging device capable of performing an efficient imaging operation using only signal charges for an effective imaging region without reading out useless signal charges. .

[0008]

In order to achieve the above object, the present invention provides an image pickup section having a plurality of photosensors for accumulating signal charges corresponding to the amount of received light, and an image pickup section provided in each of the photosensors of the image pickup section. A transfer register unit that transfers signal charges, a read gate unit that reads out the signal charges accumulated in each of the photosensors into the transfer register unit, and converts the signal charges transferred by the transfer register unit into a voltage signal and outputs the voltage signal The readout gate unit is configured by divided readout gates divided for each predetermined area unit of the imaging unit,
Control means for selectively driving the divided read gate unit to read out signal charges is provided.

In the solid-state image pickup device of the present invention, since the divided readout gate portion is selectively driven to read out the signal charges, it is possible to select a region from which pixel information is read out according to an object to be imaged. Therefore, by driving only the divided readout gates corresponding to the necessary imaging regions to read out the signal charges and transferring them by the transfer register unit, unnecessary signal charges are not read out, and only the signal charges for the effective imaging region are read out. , An efficient imaging operation can be performed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the solid-state imaging device according to the present invention will be described below. FIG. 1 is a schematic sectional view showing an embodiment in which the solid-state imaging device of the present invention is applied to a CCD linear sensor. The CCD linear sensor includes an imaging unit 110 having a plurality of photosensors for accumulating signal charges corresponding to the amount of received light, a horizontal transfer register unit 120 for transferring the signal charges accumulated in each photosensor of the imaging unit 110, and And a read gate (ROG) unit 130 that reads out signal charges accumulated in each photosensor of the imaging unit 110 to each transfer gate of the horizontal transfer register unit 120. In this example, the read gate unit 130 is divided into three in the horizontal transfer direction, and three divided read gate units 130L, 130C, and 130R are provided.

The divided read gate 13 on the left side is
0L is a signal for transferring a signal charge of a sensor array (sensor group) 110L existing in a left area of the imaging unit 110 to the horizontal transfer register 1;
20. This divided read gate unit 130L is driven by the read gate signal ROGL. Also, the central divided read gate unit 130C
The horizontal transfer register 120 transfers the signal charges of the sensor array (sensor group) 110C existing in the central region of the imaging unit 110
Is read out. This divided read gate unit 13
0C is driven by the read gate signal ROGC. The right divided read gate unit 130R reads the signal charges of the sensor array (sensor group) 110R existing in the right region of the imaging unit 110 to the horizontal transfer register 120. This divided read gate unit 130R
Are driven by the read gate signal ROGR.
In this example, three read gate signals ROGL, ROG
By controlling “H” and “L” of C and ROGR, three divided read gate units 130L, 130C,
130R to selectively control three sensor rows 110
The signal charges of L, 110C, and 110R are selectively read out to the horizontal transfer register unit 120.

Further, each photo sensor of the image pickup unit 110 includes:
A photodiode is provided in a semiconductor substrate.
The signal charge corresponding to the amount of received light is accumulated by photoelectric conversion of the photodiode. In addition, the horizontal transfer register unit 120 sequentially transfers signal charges read from each photosensor by two-phase register transfer signals φ1 and φ2. The signal charges transferred by the horizontal transfer register unit 120 are output to a charge-voltage conversion unit (FD) 140 of an output unit, and are converted into voltage signals. This voltage signal is further sent to a signal processing circuit via a buffer or the like, and is subjected to predetermined signal processing.

Further, in such a linear sensor,
Unnecessary signal charges in the imaging unit 110, the horizontal transfer register unit 120, and the readout gate unit 130 are:
Overflow drain 1 at predetermined timing
In this example, the readout gate unit 130 is divided into three divided readout gate units 13 as described above.
The overflow drain 150 is connected to each of the divided read gate units 130L, 130C, and 130R because it is divided into 0L, 130C, and 130R. Then, each divided read gate unit 130L, 130
Unnecessary signal charges in C and 130R are swept away by the overflow drain 150 at a predetermined timing (sweep-out period).

Next, the operation of the linear sensor having the above configuration will be described using a specific example. Note that the above-described method of dividing the read gate unit 130 is appropriately determined based on the pixel size and pixel surface of the present linear sensor, the angle of view determined based on the relative position between the lens and the linear sensor, and the like. However, for the sake of simplicity, here, a total of 600 pixels divided into three by 2000 pixels
An example of the readout gate unit of the 0 pixel will be described.

First, the sensor array 11 on the left side of the imaging unit 110
When the target pixel can be sufficiently read at 0 L, the read is performed by setting only the read gate signal ROGL to “H” at the read timing, and the remaining two read gate signals ROGC and ROGR are set to “L”.
Leave as is. As a result, the central and right sensor rows 11
The signal charges stored in 0C and 110R are not read out,
The dummy signal charges are swept away by the overflow drain 150. As a result, the signal charges can be transferred to the output unit (FD unit 140) by performing the transfer 2000 times per horizontal scan. That is, when the horizontal transfer register unit 120 performs 2,000 transfers, all the signal charges of the transfer gates of the horizontal transfer register unit 120 corresponding to the left sensor row 110L have been completely transferred. It becomes empty, and the next imaging operation (charge reading operation) becomes possible. As a result, the horizontal synchronization period shown in FIG. 3 can be reduced.

In the scanner device using such a linear sensor, the signal charge is transferred in the horizontal direction by the horizontal scanning of the imaging unit 110, and then the linear sensor is moved relative to the original in the vertical direction. The horizontal scanning is performed, and the overall imaging speed (that is, the vertical scanning speed) can be increased in accordance with the effective pixel size of the original document by shortening the horizontal transfer time of the read signal charges by the horizontal scanning described above. It becomes possible.

In the above description, the left sensor row 1
Although the case where only 10 L of signal charge is read has been described, depending on the application, the central sensor row 11
Only the signal charge of 0C is read out, or the right sensor row 1
It is also possible to read out only 10R signal charges. Alternatively, when only the signal charges of the left sensor row 110L and the central sensor row 110C are read, or when only the signal charges of the central sensor row 110C and the right sensor row 110R are read, the left sensor row 11
It is also possible to read out only the signal charges of 0L and the right sensor row 110R.

In the above example, the case where the read gate is divided into three parts has been described. However, another division method may be adopted. Further, each divided read gate does not necessarily need to be divided at equal intervals. Further, as a specific method for selecting the above-mentioned readout area, for example, the selection can be made by an input accompanying an operation by an operator. For example, in various types of imaging devices provided with the solid-state imaging device of the present embodiment, an operation key that allows the operator to specify an imaging region may be provided, and a readout region may be selected based on the operation of the operation key. Good. Further, for example, in a scanner device or the like, when reading a document, an operation for setting the document size may be performed, and it is possible to select a read gate based on an input by such a setting operation. Alternatively, in a camera using a CCD, in a configuration in which the field of view is adjusted according to the subject, it is possible to detect an input by such an adjustment operation and select a readout gate based on the input.

Further, during the charge accumulation period of the imaging section,
A means is provided for detecting signal charges leaked from each photo sensor due to overflow for each divided area, and only an effective imaging area is automatically determined based on the detection signal, and an effective imaging area is read when reading the signal charges. It is also possible to adopt a configuration in which only one is selected and read. Further, some copiers and the like are provided with a pre-scan function for checking the document size in advance, and select such a pre-scan function by selecting a divided read gate in the solid-state imaging device of the present invention. To read out only a necessary pixel area.

In the above example, the case where the solid-state imaging device of the present invention is applied to a linear sensor has been described.
The present invention can also be applied to an area sensor that captures a two-dimensional image by arranging photosensors in a matrix. In this case, the transfer register section includes a vertical transfer register and a horizontal transfer register. The read gate section may be divided only in the horizontal transfer direction of the imaging section, The section may be divided in both the horizontal transfer direction and the vertical transfer direction.

[0021]

As described above, in the solid-state imaging device according to the present invention, the readout gate for reading out signal charges from the imaging section to the transfer register section is divided for each predetermined area unit of the imaging section, and each divided readout is performed. The gate portion is selectively driven to read out signal charges. Therefore, by driving only the divided readout gates corresponding to the necessary imaging regions to read out the signal charges and transferring the signal charges by the transfer register unit, unnecessary signal charges are not read out and the signal charges for the effective imaging region are not read. , An efficient imaging operation can be performed. Therefore, it is possible to shorten the imaging time. In addition, since the scanning period in the imaging unit can be shortened, dark current generated in the transfer register unit can be suppressed. As a result, high-speed reading can be performed without increasing the operating frequency and preventing image quality deterioration.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration example of a CCD linear sensor to which the present invention is applied.

FIG. 2 is a schematic sectional view showing a configuration example of a conventional CCD linear sensor.

FIG. 3 is a timing chart showing the operation of the CCD linear sensor shown in FIG.

[Explanation of symbols]

110 ... Imaging unit, 110L, 110C, 110R ...
Sensor row, 120 horizontal transfer register section, 130
Read gate unit, 130L, 130C, 130R ...
Divided read gate section, 140 ... Charge-voltage conversion section, 1
50 Overflow drain.

Claims (9)

[Claims] An imaging unit having a plurality of photosensors for accumulating signal charges corresponding to the amount of received light; a transfer register unit for transferring the signal charges accumulated in each photosensor of the imaging unit; and each of the photosensors A read gate unit for reading the signal charges stored in the transfer register unit; and an output unit for converting the signal charges transferred by the transfer register unit to a voltage signal and outputting the voltage signal, wherein the read gate The unit is configured by a divided read gate divided for each predetermined area unit of the imaging unit, and provided with control means for selectively driving the divided read gate unit to read signal charges. Solid-state imaging device. 2. The image capturing section is configured as a linear sensor that captures a one-dimensional image using one or a plurality of sensor rows in which each photo sensor is arranged in one direction, and the transfer register section includes a sensor of the image capturing section. 2. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is one or a plurality of horizontal transfer registers provided along a column. 3. The read gate unit is divided in a horizontal transfer direction of the imaging unit.
The solid-state imaging device according to any one of the preceding claims. 4. The image pickup section is configured as an area sensor that picks up a two-dimensional image by arranging each photo sensor in a matrix, and the transfer register section includes a plurality of transfer sensors provided along each of the photo sensors. 2. The solid-state imaging device according to claim 1, further comprising: a vertical transfer register, and a horizontal transfer register provided at an output end of the vertical transfer register. 5. The read gate unit is divided in a horizontal transfer direction of the imaging unit.
The solid-state imaging device according to any one of the preceding claims. 6. The solid-state imaging device according to claim 4, wherein the read gate unit is divided into a horizontal transfer direction and a vertical transfer direction of the imaging unit. 7. The solid-state imaging device according to claim 1, wherein the control unit selectively reads the signal charges by selectively driving the divided read gate unit based on an external input. 8. The solid-state imaging device according to claim 7, wherein the external input is input based on an artificial operation. 9. A detecting unit for detecting a non-imaging area when an image of a subject is imaged by the imaging unit, wherein the control unit selectively selects the divided read gate unit based on a detection signal of the detecting unit. 2. The solid-state imaging device according to claim 1, wherein the driving is performed to read out the signal charges.