JP2004112304A - Solid-state image pickup device, its drive method, and image pickup system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize thinning-out in the line, reduction of pixel information by addition, and shortening the time for reading one line corresponding to it in a moving image read drive, and to realize moving image display in a sensor with a high pixel number by increasing the number of read lines. <P>SOLUTION: A CCD image pickup element is provided with a plurality of two-dimensionally arranged photo diodes (PD) 1, a VCCD 2 to transfer the respective signal charges of a plurality of the photo diodes (PD) 1 in a columnar direction, a first HCCD 3 to transfer the respective charges in a row direction transferred by the VCCD 2 in a columnar direction, a second HCCD 5 arranged in parallel to the first HCCD 3 and constituted with less transfer stages than the first HCCD 3, a transfer gate 7 between the HCCDs to transfer the signal charges from the first HCCD 3 to the second HCCD 5, a first output amplifier 4 to output the charges transferred from the first HCCD 3 by converting them to a voltage, and a second output amplifier 6 to output the charges transferred from the second HCCD 5 by converting them to a voltage. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid-state imaging device, a driving method thereof, and an imaging system.
[0002]
[Prior art]
2. Description of the Related Art In recent years, applications for handling images on a computer have been dramatically increased. Here, the commercialization of digital cameras for capturing images into computers has become active. As a development trend of such an image sensor of a digital camera, a digital still camera (DSC) handling a still image is pursuing a direction toward increasing the number of pixels, and usually an image sensor of a moving image (video movie) camera. Has been standardized at 250,000 to 400,000 pixels, whereas digital still cameras have commercialized cameras using high-pixel imaging devices with 1.3 to 5 million pixels, and competition in the number of pixels will remain. He is not showing his appearance.
[0003]
Many DSCs adopt a method in which an image sensor (CCD sensor, CMOS sensor) used for photographing a still image is driven as a moving image, the image is processed, and the image is displayed on an electronic viewfinder (EVF). An optical viewfinder is also used, but the style that DSCs are taken naturally by EVF has permeated. A DSC having such an EVF also has a video output, and outputs a video signal corresponding to a television standard such as NTSC or PAL.
[0004]
The number of pixels of an image signal required for displaying such an EVF moving image or NTSC / PAL video signal is far smaller than that of a still image.
[0005]
First, looking at the number of display lines and the display cycle, for which the display standard is clear, the number of lines to be displayed is about 220 to 240 for EVF, about 240 for NTSC, and about 280 for PAL. The display cycle of an image is not specified in EVF, but is often displayed at 25 or 30 frames (frames) / sec (seconds). NTSC requires 30 frames / sec, and PAL requires 25 frames / sec. A liquid crystal display (LCD) for EVF display usually has a pre-stage circuit that obtains an NTSC or PAL video signal and converts it into a signal for LCD display. Therefore, the number of signal lines required for EVF is the number of PAL or NTSC lines.
[0006]
Now, in the image sensor used in the DSC, when the total number of pixels is 2,000,000 to 5,000,000, the number becomes 1200 to 2000 lines. The time for reading all the pixels is about 100 to 250 ms, and about 4 to 10 Frame / Sec. This is the case where the readout speed of the image sensor is set to read out one pixel in 50 ns. The readout frequency of the current CCD image sensor is about 20 MHz, which is about this level.
[0007]
Even if driven at twice the speed of a high-definition broadcast camera, the speed is 8 to 20 Frame / Sec, and repeated reading of all pixels from the image sensor is necessary for EVF display, video output of viewfinder images, and video recording. Is not the number of pieces. In addition, if the read drive frequency is increased, the power consumption of the camera increases, and the heat generated by the camera increases the dark current of the image sensor, thereby deteriorating the image quality.
[0008]
Therefore, since the number of lines of the image sensor is much larger than the number of lines required for an image for EVF or video display, the image sensor can perform a moving image reading method in which the number of lines to be read is reduced. Thus, a moving image reading driving method is provided. The number of lines in one frame output by such a moving image readout drive is about 200 to 300 lines, which is determined by thinning (signal charges of lines not to be read out are removed in the sensor) or by lines. This is done by means of adding (two or more lines of the same column of pixels are added together in the transfer CCD or the like) or by using them together to reduce the number of output lines.
[0009]
As an image sensor used for the DSC, an interline type CCD (charge coupled device) image sensor (hereinafter, “IT-CCD”) is often used. FIG. 5 shows a schematic configuration diagram of this IT-CCD.
[0010]
In FIG. 5, reference numeral 1 denotes a photodiode (PD) for converting optical information imaged in the image area into electric charges, which are arranged vertically and horizontally in the image area.
In addition, a color filter for transmitting light of each color component is formed on the upper part of the PD 1. In a DSC, this color filter is often configured in a so-called Bayer array in which primary colors (red R, green G, and blue B) are arranged in 2 × 2 pixels and are repeatedly arranged using these as basic units (see FIG. 5 is shown in a Bayer arrangement).
[0011]
Reference numeral 2 denotes a vertical transfer CCD (VCCD) for receiving a signal charge from the PD 1 and transferring the signal charge in the vertical direction. Normally, the VCCD 2 is of a four-phase driving system, and an image signal is read out in a two-field reading system in which one screen is a field of odd-numbered rows and a field of even-numbered rows, and one frame image is read out in two fields separately. .
[0012]
V1, V2, V3, and V4 in FIG. 5 are the four-phase electrodes of the VCCD 2, respectively. Normally, the electrode V1 is also provided with a function of reading from the PD on the R and G lines to the VCCD2 (below the adjacent V1 gate). The electrode V3 is provided with charge reading from the PD1 of the BG line.
[0013]
Reference numeral 3 denotes a horizontal transfer CCD (HCCD) for receiving charges of each line of the VCCD 2 and transferring the charges in a horizontal direction, which is normally configured for two-phase driving.
[0014]
Reference numeral 4 denotes an output amplifier that converts a signal charge transferred from the HCCD 3 into a voltage signal and outputs the voltage signal.
[0015]
As described above, in the related art, such an image sensor is driven by field readout in which two fields of odd and even lines are sequentially read.
[0016]
In the case of the sensor shown in FIG. 5, reading of the first field composed of RG lines is performed in the first field. When a high voltage is applied to the V1 gate, each charge on the RG line is transferred under the V1 electrode of the VCCD2. Thereafter, the phase of the electrodes V1, V2, V3, and V4 is changed, and a pulse of intermediate voltage-low voltage is applied. Thus, the signal is transferred to the HCCD 3 and transferred from the HCCD 3 to the output amplifier line by line to be output. The VCCD 2 is driven such that one line of electric charge is transferred to the HCCD 3 each time the HCCD 3 finishes reading one line of signal.
[0017]
When the reading of the charges in the first field (for one field screen composed of the RG lines) is completed (when all the charges in the VCCD 2 are read), the signal for one field screen composed of the GB lines is next. All of the charges are transferred to VCCD2. This is performed by applying a high voltage to the electrode V3. The electric charge transferred to the VCCD 2 is output by being driven in the same manner as in the first field by the RG line.
[0018]
By the way, as described above, such an IT-CCD is mainly used in DSC, but how to secure a frame reading speed at the time of a moving image by increasing the number of pixels is important. That has been a problem.
[0019]
Therefore, a method has been devised for reducing the number of read lines of one frame during a moving image. At present, as a method used in actual products, the electrodes V1 and V3 are divided into two, and the electrodes V1, V1 ', V3, and V3' are used. The electrodes V3 and V3 'are moved by applying the same drive pulse. At the time of moving images, a high voltage for reading from the PD to the V-CCD is applied to the electrodes V1 and V3, but the electrodes V1' and V3 'are read. By not applying the high voltage, the charge of the PD connected to the electrodes V1 ′ and V3 ′ is not read.
[0020]
In this method, the signal charge of the PD that has not been read is transferred to the sensor chip in the depth direction by an electronic shutter normally provided in an IT-CCD and an electronic shutter operation by a vertical overflow drain (VOD) structure for anti-blooming. , Is thrown away. This method is currently being used in a CCD image pickup device for DSC which has been commercialized, but as a patent, a fifth embodiment of Japanese Patent Application Laid-Open No. H10-256552 (FIG. 19). In the embodiment of the product, the electric charges of two consecutive lines in the horizontal CCD are added to the lines thinned out and left.
[0021]
By the way, the signal charges output for a moving image in this way have a specific number of about 200 to 300 lines. This is due to the configuration of the sensor. On the other hand, the DSC has a plurality of moving image drive modes such as EVF and video (NTSC, PAL, etc.) as described above, but the required number of lines is different. For this reason, a signal output for a moving image from the image sensor is once taken into a memory, and in a signal processing process, a necessary number of lines is resized by an interpolation process or the like, and output from each output terminal. Will be.
[0022]
[Problems to be solved by the invention]
However, the conventional solid-state imaging device for DSC has the following problems.
[0023]
1) As the number of pixels increases, the thinning rate at the time of moving images increases, and the deterioration of moving image quality also increases.
[0024]
2) As the number of pixels increases, the number of output lines during a moving image decreases.
[0025]
The two problems will be described below.
[0026]
When reducing the number of output lines of the image sensor, addition is more preferable in terms of image quality than thinning. When thinning is performed, moire of luminance and color increases, and the jaggedness of the oblique edge portion increases as the thinning amount increases. However, a driving example for realizing 30 frames / sec in a DSC CCD product on the market is as follows.
[0027]
In 2 million pixels, one line is read out of four lines, and three lines are removed.
With 3 million pixels, 2 lines are added and read out of 6 lines, and by removing 4 lines,
With 4 million pixels, 2 lines out of 8 lines are read out by adding and removing 6 lines.
With 5 million pixels, 2 lines out of 8 lines are read out and 6 lines are removed,
Each is realized.
[0028]
Here, the read clock frequency of the sensor is the same from 2,000,000 to 4,000,000 pixels, but the frequency is increased at 5,000,000 pixels (about 4,000,000 to 5,000,000 pixel ratio). Normally, when adding charges, the CCD sensor for DSC uses a CCDC to add charges. Only about two pixels are realized as the number of pixels to be added, and more than that is rarely performed because other problems also occur. Therefore, since the number of addition lines cannot be increased any more, the number of thinned lines must be increased as the number of pixels increases.
[0029]
Normally, in the moving image read drive, data is read so that one field is output in a Bayer array. This is because they are used for applications requiring immediacy, such as EVF. In the EVF, continuous reading of one field is displayed. (In the case of a still image, since information of one frame is temporarily stored in a memory and then processed, information necessary for signal processing is to read out only RG lines in the first field and read out only GB lines in the next field. It is not always necessary to sequentially read out. However, since EVF requires immediacy, after the RB line, the GB line is read out so that image processing and display can be performed at this stage. is there.)
For this reason, in the case of a Bayer array 2-field readout CCD sensor, the basic unit of thinning is a multiple of 2, so for example, when 8 lines are used as the basic cycle of thinning, 10 lines are thinned. It is a cycle.
[0030]
Since the number of lines of the 5 million pixel sensor is about 2000 lines, the output is 250 lines in units of 8 lines and 200 lines in units of 10 lines.
[0031]
With the same driving frequency, even if it is simply estimated, in order to realize the same image display cycle, the thinning rate must be increased in proportion to the number of pixels. Looking at the number of pixels above, 2 million pixels are 1/4 line (4 times speed), 3 million pixels with 1.5 times the number of pixels and 1/6 lines (6 times speed) with 2 times 4 million pixels. It is 1/8 line (8 times speed).
[0032]
However, 5 million pixels require 1/10 line (10 times speed). In this case, the number of output lines is 200 lines, which is far more than the 240 to 250 lines required for moving image display described above. Since the number of lines is extremely small, the thinning rate is not changed by increasing the driving speed of the sensor.
[0033]
If the thinning rate is increased, it is necessary to resize an image of 200 lines to 240 to 250 lines. However, in this case, the image quality is deteriorated by originally using 1/8 line, and further, the image quality is further deteriorated by enlarging the line. Further, the process of expanding the number of lines is much more complicated than the process of reducing the number of lines.
[0034]
Incidentally, the original number of lines and the number of lines at the time of moving images of the image sensor having the number of pixels above are approximately as follows.
[0035]
For 2 million pixels, 1200 lines, 300 lines for moving images,
With 3 million pixels, the number of lines is 1500, the number of lines at the time of movie is 250,
With 4 million pixels, the number of lines is 1700, the number of lines during movie is 210,
With 5 million pixels, the number of lines is 2,000, the number of lines during movie is 250,
It has become.
[0036]
Therefore, although the number of lines at 4 million pixels is smaller than the number of moving image display lines, it is small, and the angle of view on display is only slightly reduced, so that it is not changed. If the number of lines is smaller than this, resizing for enlargement is indispensable. However, if the number of lines is excessively reduced, the image quality of the viewfinder becomes less informative, and if the number of lines is decreased excessively, recognition of the subject becomes difficult. As for an image desired as an EVF image, 240 images are desired.
[0037]
From the viewpoint of image quality, it is preferable to reduce the size of the information from the information more than the number of lines necessary for the moving image (reduce the effective thinning rate), but in the case of an image sensor having 3 million pixels or more, the necessary lines are secured. That is the situation at last. Increasing the number of addition lines lowers the effective thinning rate. However, as described above, there are restrictions on sensor production.
[0038]
By increasing the number of thinning lines in this way, EVF (or video) moving images have been made possible up to 5 million pixels, but in order to realize an area sensor with more pixels, the thinning rate must be changed. It will be difficult to do. This is because the number of pixels in one line increases in accordance with the increase in the number of pixels, and thus the readout time of one line increases.
[0039]
For this reason, the number of lines is reduced to 200 or less when the same drive frequency is used and a 30 Frame / Sec speed is realized. The only way to reduce the number of lines is to increase the driving frequency. However, driving at a higher speed increases power consumption. There is also a disadvantage that the drive speed and the number of readout lines (the number of pixels) are not simply proportional, and the higher the speed is, the lower the efficiency is. That is, the reading time for one line of the sensor is composed of the time for reading out the pixel charges in one line and the time for transferring from the VCCD to the HCCD. The former is proportional to the number of pixels, while the latter is a fixed time. The higher the speed, the greater the ratio of the latter time, and even if the speed is increased, the reading time for one line will not increase much.
[0040]
In this case, the frame speed is reduced. However, if the display cycle is reduced, the feeling that the image is displayed intermittently is lost, and the photographer loses the chance to take a picture.
[0041]
At present, up to about 6 million pixels can be realized by a conventional method, but it can be said that an EVF (or video) moving image cannot be realized with an image sensor having more pixels.
[0042]
Also, as will be described again, since the image quality deteriorates when the effective thinning rate is large, it is preferable to lower the effective thinning rate even with the above sensor of 3 to 6 million pixels. It is desirable to increase the number.
[0043]
The present invention has been made to solve such a conventional problem. For example, in a moving image readout drive, etc., pixel information is reduced by thinning out and adding lines, and the time required to read one line is reduced accordingly. And to increase the number of readout lines, for example, to realize moving image display on a high pixel sensor.
[0044]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is realized by the following solid-state imaging device, a driving method thereof, and an imaging system.
[0045]
That is, in a solid-state imaging device having a plurality of photoelectric conversion units and a plurality of transfer units, one of the plurality of transfer units reads out all or a predetermined number of signal charges of the plurality of photoelectric conversion units. The other transfer means is realized in a solid-state imaging device characterized in that it is an output line for reading out signal charges of the photoelectric conversion means in a smaller number than the one transfer means.
[0046]
Further, in a two-dimensional solid-state imaging device having a plurality of two-dimensionally arranged photoelectric conversion units and a plurality of transfer units, the solid-state imaging device is characterized in that the output stages of the plurality of transfer units are different from each other. You.
[0047]
Also, a plurality of two-dimensionally arranged photoelectric conversion means, a vertical transfer means for transferring respective signal charges of the plurality of photoelectric conversion means in a column direction, and a row direction transferred from the vertical transfer means, respectively. A first horizontal transfer means for transferring the charge of the first horizontal transfer means, a second horizontal transfer means provided in parallel with the first horizontal transfer means, and having a smaller number of transfer stages than the first number of horizontal transfer stages; Transfer means for transferring signal charges from the first horizontal transfer means to the second horizontal transfer means; and transfer means for converting the charges transferred from the first horizontal transfer means into a voltage for output. The present invention is realized in a solid-state imaging device including a first output unit and a second output unit that converts a charge transferred from the second horizontal transfer unit into a voltage and outputs the voltage.
[0048]
Further, the solid-state imaging device described above is realized in a solid-state imaging device having a horizontal charge thinning drain for removing a part of each charge in the row direction transferred by the vertical transfer means.
[0049]
Further, the above-mentioned solid-state imaging device is realized in a solid-state imaging device having a unit for adding a part of each electric charge in the row direction transferred by the vertical transfer unit.
[0050]
Also, a plurality of two-dimensionally arranged photoelectric conversion means, a vertical transfer means for transferring respective signal charges of the plurality of photoelectric conversion means in a column direction, and a row direction transferred from the vertical transfer means, respectively. And a second horizontal transfer means provided in parallel with the first horizontal transfer means and having fewer transfer stages than the first horizontal transfer stage. Transfer means for transferring signal charges from the first horizontal transfer means to the second horizontal transfer means; and transfer means for converting the charges transferred from the first horizontal transfer means into a voltage. And a second output means for converting the electric charge transferred from the second horizontal transfer means into a voltage and outputting the voltage. Of the first row is the first The horizontal transfer means are transferred to the flat transfer means, and thereafter, the respective charges in the row direction transferred from the vertical transfer means are driven to be added, thinned, or added and thinned to transfer the horizontal transfer means. Through the second horizontal transfer means.
[0051]
Also, a plurality of two-dimensionally arranged photoelectric conversion means, a vertical transfer means for transferring respective signal charges of the plurality of photoelectric conversion means in a column direction, and a row direction transferred from the vertical transfer means, respectively. A first horizontal transfer means for transferring the charge of the first horizontal transfer means, a second horizontal transfer means provided in parallel with the first horizontal transfer means, and having a smaller number of transfer stages than the first number of horizontal transfer stages; Transfer means for transferring signal charges from the first horizontal transfer means to the second horizontal transfer means; and transfer means for converting the charges transferred from the first horizontal transfer means into a voltage for output. A solid-state imaging device including a solid-state imaging device including a first output unit and a second output unit configured to convert a charge transferred from the second horizontal transfer unit into a voltage and output the voltage; The imaging device removes all pixel charges of the imaging device. A first mode in which an image is formed by extruding an image, and the solid-state imaging device continuously outputs the moving image by reducing the number of pixels by adding or thinning out all the pixels of the image sensor or by adding and thinning out. And a second mode for generating an image. In the first mode, the signal charge of the solid-state imaging device is output from the first output means via the first horizontal transfer means, and In this mode, the signal charges of the solid-state imaging device are output from the second output means via the second horizontal transfer means, thereby realizing the solid-state imaging device.
[0052]
Further, the present invention is realized in an imaging system including the above-described solid-state imaging device, an optical system that forms light on the solid-state imaging device, and a signal processing circuit that processes an output signal from the solid-state imaging device. You.
[0053]
According to the above-described means, in the present invention, in moving image readout driving and the like, it is possible to reduce pixel information by thinning out and adding lines and to shorten the one-line readout time accordingly, thereby increasing the number of readout lines. For example, it realizes moving image display in a high pixel sensor.
[0054]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0055]
[First embodiment]
FIG. 1 shows a configuration of a CCD imaging device (solid-state imaging device) according to a first embodiment of the present invention. The CCD imaging device of the first embodiment is applied to an interline type CCD (IT-CCD). In FIG. 1, the same reference numerals are given to the same IT-CCD configuration as in the conventional example, and the description thereof will be simplified or omitted.
[0056]
In the CCD image sensor shown in FIG. 1, reference numeral 1 denotes a photodiode (PD) as a photoelectric conversion element for converting light information imaged in an image area into electric charges, and is arranged vertically and horizontally in the image area. . In addition, a color (color) filter for transmitting light of each color component is formed in the upper part of the PD 1, and symbols R, G, and B are types of color filters, and are arranged in a Bayer array.
[0057]
Reference numeral 2 denotes a vertical transfer CCD (hereinafter, “VCCD”) as a vertical transfer means for receiving a signal charge from the PD 1 and transferring the signal charge in the vertical direction. Also has a four-phase drive configuration as in the conventional example. In FIG. 1, the wirings of the four electrodes, V1, V2, V3, and V4 are omitted, but they have the same configuration as the conventional example shown in FIG.
[0058]
Reference numeral 3 denotes a horizontal transfer CCD (hereinafter, referred to as a "first HCCD") as a conventional horizontal transfer CCD as first horizontal transfer means for receiving charges of each line of the VCCD 2 and transferring the charges in a horizontal direction. It is configured for driving. Although the wiring is also omitted, it has the same configuration as the conventional example.
[0059]
Reference numeral 4 denotes an output amplifier (hereinafter, referred to as a "first output amplifier") as a first output means, which converts signal charges transferred from the first HCCD 3 into a voltage signal (CCD output 1). Output.
[0060]
In FIG. 1, a second horizontal output system that runs along a first horizontal output system (first HCCD 3 and CCD output 1) is provided as a constituent element of the present invention. That is, reference numeral 5 denotes a horizontal transfer CCD (hereinafter, "second HCCD") as a second horizontal transfer means constituting a second horizontal output system, which is configured for two-phase driving similarly to the first HCCD 3. The number of transfer stages is set to １ ／ of that of the first HCCD 3. The signal charge read by the second HCCD 5 is converted into a voltage signal by an output amplifier (hereinafter, “second output amplifier”) 6 as a second output means, and is read as the CCD output 2.
[0061]
Reference numeral 7 denotes a transfer gate between HCCDs as transfer means between horizontal transfer means for transferring charges from the first HCCD 3 to the second HCCD 5. The HCCD transfer gate 7 has three stages of the first HCCD 3 (a set of electrodes H1 and H2 is called one stage. This means that one column (column) of charges moves to the position of the next column. ) Is provided for one path (that is, one path for one stage of the second HCCD 5). When a pulse is applied to the electrode on the inter-HCCD transfer gate 7, the signal charges in the cells of the first HCCD 3 adjacent to the inter-HCCD transfer gate 7 are transferred to the cells of the second HCCD 5 adjacent to the inter-HCCD transfer gate 7. The internal potential is configured as follows.
[0062]
Reference numeral 8 denotes a horizontal charge thinning drain for eliminating charges in one of three columns. In FIG. 1, columns 2, 5, 8,... Are counted from the left column in the figure of the VCCD 2 and are provided corresponding to the cells of the first HCCD 3 below the VCCD 2 every other two columns. Thereby, after the charge of the VCCD 2 to be thinned enters the cell of the first HCCD 3 adjacent to the VCCD 2, the drain gate provided between the cell in contact with the drain of the first HCCD 3 (not shown) and the horizontal charge thinning drain 8 is changed. By opening, the signal charges to be thinned are swept away by the horizontal charge thinning drain 8.
[0063]
Here, the reading operation of the CCD image pickup device of the first embodiment will be described. This read operation is executed individually according to the mode for reading a still image and the mode for reading a moving image.
[0064]
First, at the time of reading a still image (reading of all pixels), signal charges are read out by the first output system, that is, the first HCCD 3 and the first output amplifier 4, by performing the same operation as in the conventional example. At this time, the transfer gate 7 between HCCD and the drain gate are fixed to a potential serving as a wall. Further, the second HCCD 5 is stopped.
[0065]
Next, at the time of reading a moving image, the following operation is performed.
[0066]
First, the signal charge for one line from the VCCD 2 is transferred to the first HCCD 3 in the same manner as in the still image reading mode of the conventional CCD image sensor or the CCD image sensor of the present embodiment. After the signal charge for one line is transferred to the first HCCD 3, the drain gate is driven so as to sweep out the charges in the cells of the first HCCD 3 adjacent to the signal charge to the drain 8, and at the same time, the transfer gate between the HCCDs is transferred. 7 is driven so as to transfer the signal charges in the cells of the first HCCD 3 adjacent thereto to the cells of the second HCCD 5 adjacent thereto.
[0067]
At this time, in the first HCCD 3, the electrode in the cell in which the electric charge is stored (this electrode is referred to as H1 like the conventional wiring) is driven to perform this transfer, but is not in contact with the VCCD 2. The side electrode (referred to as H2) is fixed at a potential to be a wall.
[0068]
Similarly, in the second HCCD 5, an electrode (referred to as HH1) in the cell which is in contact with the inter-HCCD transfer gate 7 is driven so as to receive the electric charge transferred through the inter-HCCD transfer gate 7 (note that the inter-HCCD transfer gate 7). The electrode on the side not in contact with the transfer gate 7 is called HH2).
[0069]
By operating in this manner, among the charges of one line transferred to the first HCCD 3, the signal charges of 1, 4, 7,... Columns are transferred to the second HCCD 5 (see the arrow a1 in FIG. 1), 2, 5,. The charge of the column 8 is eliminated by the horizontal charge thinning drain 8 (see the dotted arrow a2 in FIG. 1), and the charge of the column 3, 6, 9,... Remains stored in the cells of the first HCCD 3 which are in contact with the VCCD 2. Become.
[0070]
Next, the charges in the cells in contact with the VCCD 2 of the 3, 6, 9... Columns of the first HCCD 3 are transferred to the cells in contact with the inter-HCCD transfer gate 7 (see arrow a3 in FIG. 1). The first HCCD 3 is driven such that it is transferred through the inter HCCD transfer gate 7 into the cell in contact with the inter HCCD transfer gate 7 of the second HCCD 5 (see arrow a4 in FIG. 1). The electrode HH1 of the second HCCD 5 and the transfer gate 7 between the HCCDs are driven (at this time, the electrode H2 of the first HCCD 3 and the electrode HH2 of the second HCCD 5 are fixed to a potential state to be a wall).
[0071]
Here, in the cell in contact with the HCCD transfer gate 7 of the second HCCD 5, both charges of columns 1 and 3, both charges of columns 4 and 6, both charges of columns 7 and 9, are added together. Will be accumulated.
[0072]
The signal charges in which the lateral information of the CCD image sensor is reduced to １ ／ are sequentially output from the second output amplifier 6 by driving the second HCCD 5. At this time, the second HCCD 5 has one-third the number of stages of the first HCCD 3 and outputs one line of information in one-third of the time when data is read from the first HCCD 3. Needless to say, the first HCCD 3 is stopped during the line output driving when the second HCCD 5 is driven.
[0073]
By the above method, the reading time for one line is reduced to 1/3. However, although there is an increase in the time required for the movement from the first HCCD 3 to the second HCCD 5 and the charge addition, HCCD, HCCD Since the capacity of the inter-transfer gate 7 is light, the driving time is extremely short, which is about the time for transferring data for several stages by the HCCD, which is only a very small time for one line reading time.
[0074]
In this manner, by performing the thinning-out addition on the horizontal side and providing a reading system dedicated to EVF, the reading time can be reduced by the reduced reading time by the thinning-out addition. In order to reduce the reading time, the thinning was added only to the vertical side, but it is now also allocated to the horizontal side, so the thinning rate on the vertical side can be reduced, and the thinning on the horizontal side should be about the same. With the balanced thinning ratio in the vertical and horizontal directions, it is possible to reduce the deterioration of the image quality during EVF and video driving. As a result, even in an area sensor having 6 million pixels or more, which has not been established in the conventional example, it is possible to drive a moving image for EVF or video. As a supplement, in the horizontal thinning-out addition, another color between the same colors is thinned out by adding the same color, and the output of the CCD becomes a Bayer array, so that it is not necessary to change the configuration of the signal processing for the output.
[0075]
That is, according to the present embodiment, by separately providing the HCCD for reading a still image and the HCCD for reading a moving image, it is possible to reduce pixel information by thinning out and adding in a line in reading a moving image, and one line corresponding to the thinning. The reading time can be reduced. This makes it possible to increase the number of readout lines for moving images, and to easily realize moving image display in a conventional method, which is extremely difficult with a high-pixel sensor of 6 million pixels or more, and a DSC of 6 million pixels or more. This enables a product with an EVF function. Further, even in a sensor having 6 million pixels or less, the thinning that has conventionally been imposed only on the vertical side is distributed to the horizontal side, so that it is possible to reduce the deterioration of image quality in moving images.
[0076]
[Second embodiment]
FIG. 2 shows a configuration of a CCD imaging device (solid-state imaging device) according to a second embodiment of the present invention. In FIG. 2, the components indicated by 1 to 8 are the same as those of the first embodiment shown in FIG. 1, and the difference is that the charges of 3, 6, 9... (See the dotted arrow a5 in FIG. 2). Therefore, according to the structure of the second embodiment, it is not necessary to add the charges of the columns 1, 4, 7,... And the charges of the columns 3, 6, 9,. Become.
[0077]
Whether the structure of the first embodiment shown in FIG. 1 is selected or the structure of the second embodiment shown in FIG. 2 is selected may be determined according to the sensitivity required at the time of EVF. In the structure of the first embodiment shown in FIG. 1, by adding two pixels of the same color in the horizontal direction, the sensitivity is doubled as compared with the structure of the second embodiment shown in FIG.
[0078]
Also, in the configuration of the second embodiment shown in FIG. 2, a drain gate (not shown) for two, five, eight,... Columns and a three, six, nine,. At the time of addition, the drain gates for the columns 3, 6, 9,... Are fixed at the wall potential, and the other electrodes are driven in the same manner as in the first embodiment. , And the drain gates for the columns 3, 6, 9,... Can be selectively used by driving the same.
[0079]
Needless to say, even in the structure of the second embodiment, the output image is output in the Bayer array, and the read time of one line is reduced to 1/3.
[0080]
[Third embodiment]
FIG. 3 shows a configuration of a CCD imaging device (solid-state imaging device) according to a third embodiment of the present invention. In FIG. 3, the components indicated by 1 to 8 are the same as those in FIGS. 1 and 2 except for two-column reading (see arrows a6 and a7 in FIG. 3) and two-column thinning (FIG. 3 (see arrows a8 and a9). That is, in FIG. 3, the signal charges in the 1, 2, 5, 6, 9, 10,... Columns are respectively transferred to the second HCCD 5, and the signal charges in the 3, 4, 7, 8, 11, 12,. , Respectively, are swept away by the thinning drain 8.
[0081]
Therefore, according to the structure of the third embodiment, the number of transfer stages of the second HCCD 5 is set to の of that of the first HCCD 3, so that the read time of one line is reduced to １ ／.
[0082]
In the first embodiment, the readout time of one line is reduced to one third of that in the case of reading out all pixels by adding two columns and thinning out one column among three columns adjacent to one line. In the embodiment, of the three columns adjacent to one line, two columns are thinned out (when two pixels are added, two columns are added and one column is thinned out as in the first embodiment), so that the read time of one line is read out by all pixels. In the third embodiment, of the four columns adjacent to one line, the readout time of one line is reduced to half that of the case of reading out all the pixels by thinning out two columns. However, the present invention is not limited to these configurations and driving methods, and the configurations and driving methods of the columns to be read, the columns to be thinned out, and the columns to be added are within the scope of the present invention. Yibin be modified and carried out.
[0083]
Next, an imaging system (imaging device) using the CCD imaging device (solid-state imaging device) of the first to third embodiments will be described. An embodiment in which the solid-state imaging device of the present invention is applied to a digital camera will be described in detail with reference to FIG. FIG. 4 is a block diagram showing a case where the solid-state imaging device of the present invention is applied to a digital camera.
[0084]
In FIG. 4, reference numeral 101 denotes a barrier that serves both as protection of the lens and as a main switch; 102, a lens for forming an optical image of a subject on the solid-state imaging device 104; 103, a diaphragm for varying the amount of light passing through the lens 102; A solid-state imaging device for capturing a subject formed by the lens 102 as an image signal, an A / D converter 106 for performing analog-digital conversion of an image signal output from the solid-state imaging device 104, and an A / D converter 107 A signal processing unit for performing various corrections on the image data output from the unit 106 and compressing the data; a solid-state imaging device 104, an imaging signal processing circuit 105, an A / D converter 106, a signal processing unit 107; A timing generation unit that outputs a timing signal, 109 is various operations and a total control / operation that controls the entire still video camera. , 110 is a memory unit for temporarily storing image data, 111 is an interface unit for recording or reading on a recording medium, and 112 is a detachable semiconductor memory or the like for recording or reading image data. A recording medium 113 is an interface unit for communicating with an external computer or the like.
[0085]
Here, the operation of the digital camera at the time of shooting in the above-described configuration will be described.
[0086]
First, when the barrier 101 is opened, the main power is turned on, then the power of the control system is turned on, and further, the power of the imaging system circuit such as the A / D converter 106 is turned on.
[0087]
Then, in order to control the amount of exposure, the overall control / arithmetic unit 109 opens the aperture 103, and the signal output from the solid-state imaging device 4 is converted by the A / D converter 106 and then sent to the signal processing unit 107. Is entered. Exposure calculation is performed by the overall control / calculation unit 109 based on the data. The brightness is determined based on the result of the photometry, and the overall control / calculation unit 109 controls the aperture according to the result.
[0088]
Next, based on the signal output from the solid-state imaging device 104, high-frequency components are extracted, and the distance to the subject is calculated by the overall control / calculation unit 109. Thereafter, the lens is driven to determine whether or not the lens is in focus. If it is determined that the lens is not in focus, the lens is driven again to measure the distance.
[0089]
Then, after the focus is confirmed, the main exposure starts. When the exposure is completed, the image signal output from the solid-state imaging device 104 is A / D converted by the A / D converter 106, passes through the signal processing unit 107, and is written in the memory unit by the overall control / operation 109. Thereafter, the data stored in the memory unit 110 is recorded on a removable recording medium 112 such as a semiconductor memory through a recording medium control I / F unit under the control of the overall control / arithmetic unit 109. Further, the image may be processed by directly inputting it to a computer or the like through the external I / F unit 113.
[0090]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the pixel information by thinning out and adding lines, and to shorten the one-line reading time accordingly, and to increase the number of reading lines. A moving image can be displayed on the sensor.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a solid-state imaging device (CCD imaging device) according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram illustrating a solid-state imaging device (CCD imaging device) according to a second embodiment of the present invention.
FIG. 3 is a configuration diagram illustrating a solid-state imaging device (CCD imaging device) according to a second embodiment of the present invention.
FIG. 4 is a block diagram showing a case where the solid-state imaging device (CCD imaging device) of the first to third embodiments of the present invention is applied to a digital camera (imaging device).
FIG. 5 is a configuration diagram showing a conventional solid-state imaging device (CCD imaging device).
[Explanation of symbols]
1 Photodiode (PD)
2 Vertical transfer CCD (VCCD)
3 First horizontal transfer CCD (first HCCD)
4 First output amplifier
5 Second horizontal transfer CCD (second HCCD)
6 second output amplifier
7 HCCD transfer gate
8 Horizontal charge thinning drain

Claims (8)

In a solid-state imaging device having a plurality of photoelectric conversion means for converting an incident optical signal into signal charges, and a plurality of transfer means for transferring the signal charges converted by the photoelectric conversion means,
One transfer means of the plurality of transfer means reads out all or a predetermined number of signal charges of the plurality of photoelectric conversion means,
The solid-state imaging device according to claim 1, wherein the other transfer means of the plurality of transfer means reads out a smaller number of signal charges of the plurality of photoelectric conversion means than the one transfer means. A plurality of two-dimensionally arranged photoelectric conversion means for converting an incident optical signal into a signal charge, and a plurality of transfer means for transferring each signal charge in the row direction converted by the photoelectric conversion means. In a solid-state imaging device,
The solid-state imaging device, wherein the plurality of transfer units are configured with different numbers of transfer stages. A plurality of photoelectric conversion means arranged two-dimensionally and converting incident optical signals into signal charges;
Vertical transfer means for transferring the signal charges converted by the plurality of photoelectric conversion means in a column direction,
First horizontal transfer means for transferring respective signal charges in the row direction transferred in the column direction by the vertical transfer means;
A second horizontal transfer means provided in parallel with the first horizontal transfer means and having a smaller number of transfer stages than the first horizontal transfer means;
Transfer means between horizontal transfer means for transferring signal charges from the first horizontal transfer means to the second horizontal transfer means;
First output means for converting the electric charge transferred by the first horizontal transfer means into a voltage and outputting the voltage;
A solid-state imaging device comprising: a second output unit that converts the electric charge transferred by the second horizontal transfer unit into a voltage and outputs the voltage. The solid-state imaging device according to claim 3,
A solid-state imaging device further comprising a horizontal charge thinning drain for removing a part of each charge in the row direction transferred by the vertical transfer means. The solid-state imaging device according to claim 3,
A solid-state imaging device further comprising means for adding a part of each of the electric charges in the row direction transferred by the vertical transfer means. A plurality of photoelectric conversion means arranged two-dimensionally and converting incident optical signals into signal charges;
Vertical transfer means for transferring the signal charges in the row direction of the plurality of photoelectric conversion means in the column direction;
First horizontal transfer means for transferring respective charges in the row direction transferred by the vertical transfer means;
A second horizontal transfer means provided in parallel with the first horizontal transfer means and having a smaller number of transfer stages than the first horizontal transfer stage;
Transfer means between horizontal transfer means for transferring signal charges from the first horizontal transfer means to the second horizontal transfer means;
First output means for converting the signal charge transferred by the first horizontal transfer means into a voltage and outputting the voltage;
A solid-state imaging device comprising: a second output unit that converts a signal charge transferred by the second horizontal transfer unit into a voltage and outputs the voltage;
A first mode of reading out signal charges of all pixels of the solid-state imaging device to form an image,
A second mode of adding the signal charges of all pixels of the solid-state imaging device, or thinning out, or reducing the number of pixels by performing addition and thinning out to continuously output and generate a moving image,
In the first mode, the signal charge of the solid-state imaging device is output from the first output means via the first horizontal transfer means, and in the second mode, the signal charge of the solid-state imaging device is converted to the signal charge of the solid-state imaging device. 2. A solid-state imaging device, wherein the output from the second output unit is performed via the second horizontal transfer unit. A plurality of photoelectric conversion means arranged two-dimensionally and converting incident optical signals into signal charges;
Vertical transfer means for transferring the signal charges in the row direction of the plurality of photoelectric conversion means in the column direction;
First horizontal transfer means for transferring respective charges in the row direction transferred in the column direction by the vertical transfer means;
A second horizontal transfer means provided in parallel with the first horizontal transfer means and having fewer transfer stages than the first horizontal transfer means;
Transfer means between horizontal transfer means for transferring signal charges from the first horizontal transfer means to the second horizontal transfer means;
First output means for converting the signal charge transferred by the first horizontal transfer means into a voltage and outputting the voltage;
A second output means for converting a signal charge transferred by the second horizontal transfer means into a voltage and outputting the voltage, and comprising:
Transferring each electric charge in the row direction transferred by the vertical transfer means to the first horizontal transfer means;
Thereafter, each of the charges in the row direction is driven to be transferred by adding or thinning out, or adding and thinning out, and transferred to the second horizontal transferring means through the horizontal transferring means transferring means. A method for driving a solid-state imaging device, comprising: A solid-state imaging device according to any one of claims 1 to 6,
An imaging system comprising: an optical system that forms light on the solid-state imaging device; and a signal processing circuit that processes an output signal from the solid-state imaging device.

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