JP2001007981A - Photoelectric converter and image pickup system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption and to obtain a constant read speed in the case of either high accuracy or usual accuracy by selecting any of a plurality of horizontal transfer means that are driven in response to a plurality of read modes. SOLUTION: Exposure data in respective pixels of a transfer selection MOS transistor(TR) and a photo diode are read to horizontal transfer sections 21-24 through signal lines. In the case of reading image data consisting of only one pixel among 4 pixels or in the case of summing parts of the 4 pixels at a floating gate provided to a source follower and reading the sum, the number of read data is reduced. In this case, only one line of the horizontal transfer section 21 is enough for the horizontal transfer line actually driven. In this case, the horizontal transfer sections 22-24 other than the above can be halted. Then the power consumption is reduced logically to 1/4 of the usual power consumption through this halt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a photoelectric conversion device having a plurality of horizontal transfer means, and an imaging system using the photoelectric conversion device.

[0002]

2. Description of the Related Art In recent years, in the field of information media, an imaging field for capturing a high-definition still image, such as a digital TV camera and a digital still camera, has been widely used.
There is a coexistence with an imaging field mainly for moving images, which has low pixels and is used for a camera for a TV or a portable device.

Further, as a photoelectric conversion device, a charge transfer device (hereinafter abbreviated as CCD), a CMOS sensor manufactured by a CMOS process, and the like are known.

Conventionally, as a photoelectric conversion device such as a CCD,
As shown in FIG. 7, in the photoelectric conversion device 80, the photoelectric charges converted by the photoelectric conversion elements 82 are sequentially transferred by the vertical CCD 81, and read by one horizontal CCD 83. The transfer photocharge is read out sequentially from the photoelectric conversion element 82 adjacent to the horizontal CCD 83 for one frame and then for the next one frame.

A photoelectric conversion device provided with a plurality of horizontal transfer registers is described in Japanese Patent Publication No. 2799008. This is a photoelectric conversion device 70 having two horizontal transfer registers 73 and 74, as shown in FIG. 6, and the signal converted into photoelectric charge by the photoelectric conversion element 72 is
The vertical CCDs 71 at normal double speed and the horizontal CCDs 73 and 74
And then output from the two horizontal CCDs. In this case, for example, reading is performed by the photoelectric conversion elements 72 in the odd rows and the photoelectric conversion elements 72 in the even rows. Accordingly, the transfer speed of the horizontal CCD itself in each row can be a normal reading speed in the case of outputting mainly a moving image signal mainly for an NTSC-TV or a portable device camera.

[0006]

The photoelectric conversion device as shown in FIG.
3, 74 are prepared. However, as described above, when used simultaneously as a low-pixel NTSC-TV camera or a high-pixel digital still camera, thinning or addition reading (low-pixel reading) from one photoelectric conversion device and a pixel unit Readout (high pixel count readout)
There are times when you want to do. If the horizontal transfer speed at that time is set to a constant read speed in both modes, the subsequent processing becomes easier. Further, there is a problem that driving a large number of horizontal transfer units consumes a large amount of power.

The present invention provides a photoelectric conversion device which can achieve low power consumption at a constant reading speed in both modes of reading an image such as a high-precision still image and reading an image such as a normal-precision moving image, and It is an object to provide an imaging system using the same.

[0008]

In view of the above problems, in a photoelectric conversion device provided with a plurality of horizontal transfer means, in a high pixel count read mode, all the horizontal transfer means are driven and read out in pixel units. On the other hand, in the low pixel number read mode, several to one of the entire horizontal transfer means are driven,
Reading is performed with the pixels added. During this time, the horizontal transfer means not used are stopped.

At this time, the number of horizontal transfer means used =
If (the number of high pixels / the number of low pixels) is set, the horizontal transfer speed is constant.

[Operation] As described above, by driving in accordance with the read mode, a single photoelectric conversion element can be used.
It is possible to read out a low number of pixels in pixel addition and a high number of pixels in pixel unit reading.

Also, when reading out a low number of pixels, the horizontal transfer means to be driven is limited, so that the other inactive horizontal transfer means does not consume power, thereby reducing power consumption.

If the number of horizontal transfer means used = (the number of high pixels / the number of low pixels), the horizontal transfer speed becomes constant.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described.
This will be described in detail with reference to the drawings.

An embodiment of the present invention will be described below with reference to FIG. 2 for a CMOS sensor provided with a source follower for every four pixels.

The sensor unit 4 in FIG. 2 includes P11, P12, P
A source follower is provided for every four pixels 21 and P22. This will be described with reference to FIG.
2, PD21 and PD22 are photodiodes, and the photocharges accumulated by receiving light from the subject are selected from the selection signal lines TX11 to TX22.
When the transfer selection MOS transistor 22 is turned on, it is selected and transferred to the source follower MOS transistor T4 having a floating gate. Prior to this series of operations, the capacitance of the floating gate provided at T4 is reset to a constant potential by a reset MOS transistor T3 controlled by a reset pulse RSφ.

As described above, the transfer selection MOS transistors TX11 to TX22 and the photodiode PD1
Each pixel P composed of PD1, PD12, PD21, PD22
Exposure data in each of the pixels 11 to P22 is read out to the horizontal transfer units 21 to 24 through the signal line 40.

Such a photoelectric conversion element 4 has a horizontal direction 20.
00, and 1000 pixels in the vertical direction. Here, the total number of pixels of 2,000,000 pixels is 1/6 of one frame period.
When read in 0 seconds, the image data transfer clock is
(｛200000 pixels × 60｝ 1 / sec = 120MH)
z) is required.

However, the photoelectric conversion device of the present embodiment
The image data transfer clock is (120 MHz / 4 columns = 30 MHz) because of having the horizontal transfer units 21 to 24 of columns.
Only needs to be done.

On the other hand, in the sensor unit 4 shown in FIG. 2, when reading out image data of only one pixel among the four pixels P11 to P22, one part of the four pixels is replaced by a floating gate provided in the source follower T4. When adding and reading, the number of read data is (2 million pixels / 4
= 500,000 pixels). At this time, in order to read data without changing the processing speed of the post-processing unit, (500
000 pixels × 60 seconds = 30 MHz). Therefore, when reading out 1/4 of the pixels by the CMOS sensor, the horizontal drive actually driven only needs to be performed in one column of the horizontal transfer unit 21 as shown in FIG.

The other horizontal transfer units 22 to 24 can be stopped. The power consumption is logically １ ／ of the normal power consumption due to this pause.

In the present embodiment, the CMOS sensor provided with a source follower for every four pixels and the driving horizontal transfer section 21 are limited. However, the present invention relates to a plurality of columns of horizontal transfer sections and their driving and pausing. And this is not the case. That is, a source follower may be provided for each pixel, or another pixel configuration such as a configuration without a source follower may be used.

FIG. 1 is a diagram showing a configuration of an imaging system according to the present invention. Here, the photoelectric conversion unit is performed by light from a subject passing through the aperture blade 1 and being imaged on the photoelectric conversion element 4 by the focusing or objective lens 1. Reference numeral 3 denotes a combination of an optical low-pass filter that cuts high frequencies of light to prevent moiré, a color correction filter corresponding to the characteristics of the photoelectric conversion element, and a filter that cuts infrared rays other than visual wavelengths. Group.

The photoelectric conversion signal converted by the sensor unit 4 including a plurality of photoelectric conversion elements shown in FIGS. 2 to 4 is horizontally shifted by a timing signal such as a clock or a selection pulse from the timing generator TG8. Pixel positions are selected and scanned two-dimensionally by an X address selection unit 6 as a register and a Y address selection unit 5 as a vertical shift register, and read out to a timing adjustment unit 7. The timing adjustment unit 7 adjusts timing such as a read time of an output (one or a plurality of outputs) from the photoelectric conversion element 4. The photoelectric conversion signal is controlled by the AGC 10 in amplitude voltage gain of the read pixel signal,
The digital signal is converted by the D converter 11.

The camera digital signal processor DSP 12 performs image processing of a moving image or a still image. For still images, one-frame images are subjected to signal processing such as gathering and smoothing, and for moving images, continuous image signals are sequentially converted to compressed images in real time or at high speed by using the DRAM 13 for each frame, or thinned / inserted. Or signal processing. Further, the MPU 14 outputs a gain control signal to the AGC circuit 10, sets parameters used for image processing to the camera DSP 12 to the camera DSP 12, performs automatic exposure AE, and performs auto focus AF processing. I do. The oscillator 9 includes an aperture blade 1, a timing generator TG8, a camera DSP 12, an MPU 1
4 are supplied with various clocks and timing pulses.

The DRAM 13 is used as a temporary storage area when the camera DSP 12 performs image processing, and the image recording medium 18 is used as a non-volatile storage area, a software program of the MPU 14, and an output of the camera DSP 12. The image recording medium 18 is, for example, a smart media, a magnetic tape, an optical disk, or the like.

A video encoder 15, a CRT 16, and the like are provided to perform display after the image processing. The viewfinder 17 is, for example, an LCD, and is used for confirming a subject before storing the image on the image recording medium 18. These output devices are CR
Not limited to T16 and viewfinder 17, a printer or the like may be used. The CRT 16 may be a recent liquid crystal display panel, a plasma display panel, a display panel using an electron-emitting device, or the like.

In FIG. 1, one set of the AGC 10 and the A / D 11 is provided.
Reading at 1, P12,... Requires a processing speed of 120 MHz.

In order to avoid this, as shown in FIG.
Four sets of C 100 to 103, four sets of A / D 110 to 1
13. There is a method of providing four sets of camera DSPs 120 to 123. In this case, a set of post-processing units, for example, AG
C100, A / D110, and camera DSP120
Processing speed is the image data transfer time (1 second / 30 MHz)
$ 33nsec).

In the above configuration, when reading out image data of only one pixel out of the four pixels P11 to P22, a part of the four pixels is added by the floating gate provided in the source follower T4, and one column of horizontal data is read out. When reading is performed by the transfer unit 21, for example, the horizontal transfer unit, the post-processing is performed by the AGC 100,
Only the A / D 110 and the camera DSP 120 are required, and the remaining AGCs 101 to 103, the A / Ds 111 to 113, and the camera DSPs 121 to 123 can be suspended.

In the case of the above-described one-column transfer, the horizontal transfer unit, AG
The power consumption of the C, A / D, and camera DSP units is approximately 1 /
It becomes 4.

In the case of reading a still image at a high definition, if the real-time signal processing is not required, the reading time is reduced to about 1/4 as in the case of the one-column transfer. By specifying the reading of all pixels to the horizontal transfer unit 21 and sequentially reading the other three pixels, low-speed reading is possible. In the case of high-speed reading such as a moving image, all pixels are read. By reading out only 1/4 of the middle pixels, it is not necessary to significantly increase the speed.

In the above embodiment, the CMOS sensor mainly based on the CMOS process has been described.
The present invention can be applied to the case where a plurality of horizontal transfer units using D sensors are provided, as long as the read transfer circuits of each CCD sensor are transferred using a multi-layer substrate, respectively.

[0033]

According to the present invention, in a photoelectric conversion element having a plurality of rows of horizontal transfer sections and an imaging system using the same, a plurality of horizontal transfer sections and / or driving of a subsequent processing section are provided. By performing the pause, the processing speed can be made constant and the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration block diagram of an imaging system using a photoelectric conversion device of the present invention.

FIG. 2 is a schematic block diagram of a photoelectric conversion device of the present invention.

FIG. 3 is a schematic block diagram of a photoelectric conversion device of the present invention.

FIG. 4 is a circuit diagram of four pixels of the photoelectric conversion device of the present invention.

FIG. 5 is a schematic configuration block diagram of an imaging system using the photoelectric conversion device of the present invention.

FIG. 6 is a schematic block diagram of a conventional photoelectric conversion device.

FIG. 7 is a schematic block diagram of a conventional photoelectric conversion device.

[Explanation of symbols]

 Reference Signs List 1 aperture blade 2 lens 3 ray correcting unit 4 sensor unit 5 Y address selecting unit 6 X address selecting unit 7 timing adjusting unit 8 timing generator TG 9 oscillator 10 AGC 11 analog / digital (A / D) converting unit 12 camera DSP unit DESCRIPTION OF SYMBOLS 13 DRAM memory 14 MPU (microprocessor) 15 Video encoder 16 CRT 17 View finder 18 Image recording medium 21-24 Horizontal transfer part 40 Vertical output line 100-103 AGC 110-113 A / D conversion part 120-123 Camera DSP

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiro Endo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Seiji Hashimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon F-term within the company (reference) 4M118 AA04 AA10 AB01 BA10 BA14 CA02 DD09 DD12 FA06 FA44 GC11 GC20 5C051 AA01 BA03 DA06 DB01 DB08 DB12 DB18 DE02 DE15 DE17 EA03 EA09

Claims (13)

[Claims] 1. A photoelectric conversion device comprising a plurality of horizontal transfer means for reading signals from a plurality of arranged pixels, wherein the plurality of horizontal transfer means to be driven are selected according to a plurality of read modes. Photoelectric conversion device. 2. A plurality of read modes, wherein a first horizontal transfer speed in a first read mode and a second horizontal transfer speed in a second read mode are the same speed. The photoelectric conversion device according to claim 1. 3. The method according to claim 2, wherein the first readout mode is a pixel-by-pixel readout for reading out all pixels, and the second readout mode is a pixel addition readout of a part of all the pixels. The photoelectric conversion device according to claim 2. 4. The photoelectric conversion device according to claim 1, wherein horizontal transfer means other than the driven horizontal transfer means are stopped. 5. The photoelectric conversion device according to claim 4, wherein the post-processing unit connected to the suspended horizontal transfer unit is also suspended. 6. The number of horizontal transfer means = (high pixel count / high pixel count), wherein the plurality of horizontal transfer means have a high pixel count for reading out all of the pixels and a low pixel count for reading out some of the pixels. The photoelectric conversion device according to any one of claims 1 to 5, wherein the horizontal transfer speed of the horizontal transfer for reading out the high pixel count and the low pixel count is constant, as well as a low pixel count. . 7. The plurality of horizontal transfer means, four photodiodes, respective transfer switches for transferring respective photocharges of the four photodiodes by a transfer selection pulse, and transferring the photocharges. 7. Four horizontal transfer means for reading out each of the photodiodes from a photoelectric conversion unit in which four pixels each including a source follower circuit having a floating gate are arranged as an area sensor. 3. The photoelectric conversion device according to 1. 8. The post-processing unit includes an AGC unit that controls a read level, an A / D conversion unit that converts an output of the AGC unit into a digital signal, and a camera digital signal processing unit that processes the digital signal. The photoelectric conversion device according to claim 5, wherein: 9. An imaging system using the photoelectric conversion device according to claim 4, wherein a post-processing unit connected to the suspended horizontal transfer unit is also suspended. 10. A plurality of arranged pixels, a plurality of horizontal transfer means for reading a signal in a horizontal direction from the plurality of arranged pixels, and a first for reading out a signal for each pixel from the horizontal transfer means among the pixels. And a driving unit for selecting the horizontal transfer unit to be driven according to the mode, while controlling a second mode for reading out a signal obtained by adding signals of a plurality of pixels from the horizontal transfer unit. A photoelectric conversion device characterized by the above-mentioned. 11. The number of said horizontal transfer means to be driven when reading out signals in said first mode is made larger than the number of said horizontal transfer means to be driven when reading out signals in said second mode. 2. The method according to claim 1, wherein
The photoelectric conversion device according to 0. 12. The photoelectric conversion device according to claim 10, wherein a signal reading speed in the first mode and a signal reading speed in the second mode are the same. 13. The apparatus according to claim 1, wherein said horizontal transfer means which is not driven according to said mode is suspended.
The photoelectric conversion device according to any one of 0 to 12.