JP2004064558A - Image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup device capable of improving the quality of an image obtained by imaging a moving object. <P>SOLUTION: An image pickup device 100 is provided with an MOS sensor 6 and a signal converter 7 for converting an image pickup signal outputted from the MOS sensor 6 into an image signal. The MOS sensor 6 is provided with n lines of photo diode lines 4 configured of a plurality of photo didoes 5, and a reading unit 1 for successively reading charges stored in each of those photo didoes 5 for each photo diode line 4, and for outputting it as an image pickup signal. In this case, a whole line reading period is configured to be shorter than one frame period for displaying images for one frame. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an imaging device equipped with a MOS sensor.
[0002]
[Prior art]
Conventionally, in order to obtain an image having a good S / N ratio, a CCD type solid-state imaging device (hereinafter, referred to as a CCD sensor) having a structure capable of completely transferring charges accumulated in a photodiode and realizing low noise characteristics is provided. ) Has been used. 2. Description of the Related Art In recent years, with the spread of cameras mounted on mobile phones, demand for an imaging device using a MOS sensor characterized by low power consumption has increased.
[0003]
As a difference between the CCD sensor and the MOS sensor, a video reading operation according to a driving method is different. In the case of a CCD sensor, it has a vertical CCD for transferring charge to a photodiode. Therefore, all the pixels of the charges accumulated in the photodiode are read out to the vertical CCD at the same time, and then the charges are sequentially transferred by the vertical CCD and read out as a video signal.
[0004]
On the other hand, since the MOS sensor does not have a vertical CCD for transferring charges, a structure is adopted in which charges are read out for each line and used as a video signal. In the charge accumulation period, which indicates a period in which charge is accumulated in the photodiode provided in the MOS sensor, there is a shift along the time axis corresponding to the read frame rate between the first read line and the last read line. Would.
[0005]
As a result, in the case of the CCD sensor, an image at the same time without distortion is captured in a moving subject accompanied by movement in the same frame, whereas in the case of the MOS sensor, the image of the subject is different from the actual one. Is distorted. Hereinafter, an imaging device using a conventional MOS sensor will be described with reference to the drawings.
[0006]
FIG. 4 is a block diagram illustrating a configuration of a conventional imaging device 90. The imaging device 90 includes a MOS sensor 96. The MOS sensor 96 has n rows (n is an integer of 2 or more) of photodiode rows 4 each including a plurality of photodiodes 5 arranged along the horizontal direction. The MOS sensor 96 is provided with a reader 91. In response to the read pulse generated by the timing generator 81, the readout unit 91 transfers the charges accumulated in the respective photodiodes 5 from the first photodiode row 4 to the nth photodiode row 4 to each photodiode. The signal is read out sequentially for each diode row 4 and output to the signal converter 7 as an imaging signal.
[0007]
The signal converter 7 converts an imaging signal output from the readout unit 91 provided in the MOS sensor 96 into an image signal for displaying an image of a subject according to the timing signal generated by the timing generator 81. Then, the image data is output to the outside of the imaging device 90 via the image signal output terminal 14.
[0008]
The operation of the imaging device 90 thus configured will be described. FIG. 5 is a diagram illustrating an image plane image 85 of a MOS sensor 96 provided in a conventional image pickup apparatus 90. FIG. 6 is a schematic waveform diagram for explaining the operation of the conventional imaging device 90.
[0009]
The imaging plane image 85 shows a read line image 86 of the first line, a read line image 87 of the second line, and a read line image 88 of the last line. Each of the readout line images 86, 87 and 88 is arranged at equal intervals on the imaging surface image 85 along the horizontal direction.
[0010]
The timing generator 81 generates a read pulse 10 for reading charges from the photodiodes 5 of the photodiode row 4 corresponding to the first line according to a frame reference signal 19 having a predetermined pulse every one frame period 3. Generate. The readout unit 91 provided in the MOS sensor 96 reads out charges from the photodiodes 5 of the photodiode row 4 corresponding to the first line according to the readout pulse 10 generated by the timing generator 81, and outputs the charges as an imaging signal. Output.
[0011]
Then, the timing generator 81 generates the read pulse 10 for reading out the charges from the photodiodes 5 of the photodiode row 4 corresponding to the first line, and after the period 99 has elapsed, the timing generator 81 corresponds to the second line. A read pulse 10 for reading charges from the photodiodes 5 of the photodiode row 4 is generated. The readout unit 91 reads out charges from the photodiodes 5 in the photodiode row 4 corresponding to the second line and outputs the charge as an imaging signal in accordance with the readout pulse 10 generated by the timing generator 81.
[0012]
Similarly, after the readout unit 91 reads out charges from the third and subsequent lines in accordance with the readout pulse generated by the timing generator 8 and outputs the charge as an imaging signal, the timing generator 81 corresponds to the last line. A read pulse 10 for reading charges from the photodiodes 5 in the photodiode row 4 is generated. The readout unit 91 reads out charges from the photodiodes 5 in the photodiode row 4 corresponding to the last line and outputs the charge as an imaging signal in response to the readout pulse 10 generated by the timing generator 81.
[0013]
Therefore, in order to read all the lines, an entire line read period 92 corresponding to approximately one frame period 3 from the read pulse 10 of the first line to the read pulse 10 of the last line is required.
[0014]
Next, in response to the next pulse after one frame period of the frame reference signal 19, the timing generator 81 again outputs a read pulse for reading charges from the photodiodes 5 of the photodiode row 4 corresponding to the first line. Generate 10. In response to the read pulse 10 generated by the timing generator 81, the readout unit 91 reads out the charge again from the photodiodes 5 of the photodiode row 4 corresponding to the first line and outputs the charge as an imaging signal. As described above, the electric charge read by the reader 91 is the electric charge stored in each photodiode on the first line during the charge storage period 8.
[0015]
Then, the timing generator 81 generates the read pulse 10 for reading out the charges from the photodiodes 5 of the photodiode row 4 corresponding to the first line, and after the period 99 has elapsed, the timing generator 81 corresponds to the second line. A read pulse 10 for reading charges from the photodiodes 5 of the photodiode row 4 is generated. The readout unit 91 reads out charges from the photodiodes 5 in the photodiode row 4 corresponding to the second line and outputs the charge as an imaging signal in accordance with the readout pulse 10 generated by the timing generator 81. As described above, the charges accumulated in each photodiode on the second line during the charge accumulation period 8 are read out by the reader 91. Hereinafter, similarly, the timing generator 81 generates the read pulse 10 for reading out the charges from the photodiodes 5 of the photodiode row 4 corresponding to the last line. The readout unit 91 reads out charges from the photodiodes 5 in the photodiode row 4 corresponding to the last line and outputs the charge as an imaging signal in response to the readout pulse 10 generated by the timing generator 81. As described above, the charges accumulated in each photodiode 5 during the charge accumulation period 8 are read from each photodiode 5.
[0016]
The signal converter 7 performs general signal processing such as gamma correction, aperture processing, gain control processing, and offset control processing on the imaging signal output from the readout unit 91 to generate a multi-valued image signal. Then, the image signal is output from the image signal output terminal 14 to the outside.
[0017]
[Problems to be solved by the invention]
However, in the above-described configuration of the related art, the charge accumulation periods 8 in which charges are accumulated in the photodiodes 5 are shifted from each other by a period 99 along the time axis between adjacent lines. There is a problem that the image of the subject generated based on the charge read out every four is distorted along the vertical direction.
[0018]
7A is a diagram for explaining a conventional imaging device 90 and a subject 72 imaged by the imaging device 90. FIG. 7B is an image image of the subject 72 imaged by the conventional imaging device 90. FIG. When an image of a subject 72 moving in the moving direction 71 is captured by the image capturing device 90, the image 72 captured by the image capturing device 90 due to a shift along the time axis direction of the charge accumulation period 8 between adjacent lines. The image of the subject 72 is distorted. This image distortion becomes more remarkable as the time until the end of reading all the pixels of the MOS sensor is longer.
[0019]
SUMMARY An advantage of some aspects of the invention is to provide an imaging device that can improve the quality of an image of a moving subject, which is obtained by solving the problem.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, an imaging apparatus according to the present invention includes a MOS solid-state imaging device (hereinafter, referred to as a “MOS sensor”) that outputs an imaging signal of an image of a subject, and an imaging device that outputs the imaging signal output from the MOS sensor. A signal converter for converting an image of the subject into an image signal for displaying the image of the subject, wherein the MOS sensor is configured by a plurality of photodiodes each arranged along a horizontal direction. N rows of photodiodes (n is an integer of 2 or more) and charges accumulated in the respective photodiodes are stored in each photodiode row from the first photodiode row to the nth photodiode row. And a readout unit for sequentially reading out and outputting as an image pickup signal, and a photo diode constituting the first row of photodiodes. The entire line readout period from reading out the charge stored in the diode to reading out the charge stored in the photodiodes constituting the n-th photodiode row is longer than the storage time of the charge stored in the photodiode. It is characterized by being shorter.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
In the imaging device according to the present invention, from reading out the charges accumulated in the photodiodes constituting the first photodiode row to reading out the charges accumulated in the photodiodes constituting the n-th photodiode row Is shorter than one frame period for displaying one frame of image. For this reason, the distortion of the image of the subject due to the shift along the time axis during the charge accumulation period indicating the period in which the charge is accumulated in the photodiodes constituting each photodiode row is caused by human visual sensitivity characteristics. It is small enough to be ignored. As a result, an imaging device capable of obtaining a high-quality image can be provided.
[0022]
In the all-line readout period, distortion of the image of the subject due to a shift along the time axis between the charge accumulation periods indicating the periods in which charges are accumulated in the photodiodes constituting each photodiode row is caused by humans. It is preferable that the length be short so as to be sufficiently small to be negligible in terms of visibility characteristics.
[0023]
Preferably, the all-line readout period is shorter than 1/30 second.
[0024]
It is preferable that the reader reads out the electric charges stored in the respective photodiodes for each photodiode row in accordance with a predetermined read pulse.
[0025]
It is preferable that the apparatus further comprises a timing generator for generating the predetermined read pulse and supplying the read pulse to the reader.
[0026]
It is preferable that the timing generator generates the predetermined read pulse such that the entire line read period is shorter than 1/30 second.
[0027]
It is preferable that the image processing apparatus further includes a memory for storing the image signal converted by the signal converter for one frame.
[0028]
It is preferable that the image processing apparatus further includes a memory controller that reads and outputs the image signal of the one frame stored in the memory during one frame period in a next frame period.
[0029]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0030]
FIG. 1 is a block diagram illustrating a configuration of an imaging device 100 according to the present embodiment. The imaging device 100 includes the MOS sensor 6. The MOS sensor 6 has n rows (n is an integer of 2 or more) of photodiode rows 4 each constituted by a plurality of photodiodes 5 arranged along the horizontal direction.
[0031]
The MOS sensor 6 is provided with the reader 1. In response to the read pulse generated by the timing generator 11, the readout unit 1 transfers the charges accumulated in the photodiodes 5 from the first photodiode row 4 to the n-th photodiode row 4, respectively. The signal is read out sequentially for each diode row 4 and output to the signal converter 7 as an imaging signal.
[0032]
The signal converter 7 converts an imaging signal output from the readout unit 1 provided in the MOS sensor 6 into an image signal for displaying an image of a subject according to the timing signal generated by the timing generator 11. Then, the data is stored in the memory 12.
[0033]
The imaging device 100 includes a memory controller 13. The memory controller 13 reads out the image signal for one frame stored in the memory 12 during one frame period in the next frame period, and outputs it to the outside of the imaging device 90 via the image signal output terminal 14.
[0034]
The operation of the imaging device 100 configured as described above will be described. FIG. 2 is a diagram showing an imaging surface image 15 of the MOS sensor 6 provided in the imaging device 100 according to the present embodiment, and FIG. 3 is a schematic waveform diagram for explaining the operation of the imaging device 100. .
[0035]
The imaging surface image 15 shows a read line image 16 of the first line, a read line image 17 of the second line, and a read line image 18 of the last line. The readout line images 16, 17, and 18 are arranged at equal intervals on the imaging surface image 15 along the horizontal direction.
[0036]
The timing generator 11 generates a read pulse 10 for reading charges from the photodiodes 5 of the photodiode row 4 corresponding to the first line according to a frame reference signal 19 having a predetermined pulse every one frame period 3. Generate. The readout unit 1 provided in the MOS sensor 6 reads out charges from the photodiodes 5 of the photodiode row 4 corresponding to the first line according to the readout pulse 10 generated by the timing generator 11, and outputs the charges as an imaging signal. Output.
[0037]
Then, the timing generator 11 generates a read pulse 10 for reading out charges from the photodiodes 5 in the photodiode row 4 corresponding to the first line, and after a lapse of the period 9, the timing generator 11 corresponds to the second line. A read pulse 10 for reading charges from the photodiodes 5 of the photodiode row 4 is generated. The readout unit 1 reads out charges from the photodiodes 5 in the photodiode row 4 corresponding to the second line and outputs the charges as an imaging signal in accordance with the readout pulse 10 generated by the timing generator 11.
[0038]
Similarly, after reading charges from the third and subsequent lines, the timing generator 11 generates a read pulse 10 for reading charges from the photodiodes 5 of the photodiode row 4 corresponding to the last line. The readout unit 1 reads out charges from the photodiodes 5 in the photodiode row 4 corresponding to the last line and outputs the charges as an imaging signal in response to the readout pulse 10 generated by the timing generator 11.
[0039]
Therefore, in order to read all the lines, the entire line read period 2 from the read pulse 10 of the first line to the read pulse 10 of the last line is required.
[0040]
In the imaging device 100 according to the present embodiment, the all-line reading period 2 is shorter than the one-frame period 3. In the all-line readout period 2, the distortion of the image of the subject caused by the period 9 representing the shift along the time axis of the charge accumulation period 8 of each line is sufficiently small to be negligible in terms of human visibility characteristics. As described above, the length is preferably shorter, and is preferably shorter than 1/30 second. The timing generator 11 generates the read pulse 10 so that the all-line read period 2 is shorter than 1/30 second.
[0041]
If the entire line readout period 2 is shorter than 1/30 second, the shift along the time axis between the charge accumulation period of the photodiode on the first line and the charge accumulation period of the photodiode on the last line is 1/30. Less than a second.
[0042]
A change of a moving object at 30 frames / second or less has a characteristic that it is indistinguishable from a moving object according to human visibility characteristics. For this reason, if the entire line readout period 2 is shorter than 1/30 second, the distortion of the image of the subject becomes sufficiently small to be negligible in terms of human visibility characteristics.
[0043]
Next, in response to the next pulse after one frame period of the frame reference signal 19, the timing generator 11 reads the read pulse for reading out the electric charge from the photodiode 5 of the photodiode row 4 corresponding to the first line again. Generate 10. In response to the read pulse generated by the timing generator 11, the readout unit 1 reads out the charge again from the photodiodes 5 in the photodiode row 4 corresponding to the first line and outputs the charge as an imaging signal. As described above, the charges accumulated in the respective photodiodes on the first line during the charge accumulation period 8 are read out by the reader 1.
[0044]
Then, the timing generator 11 generates a read pulse 10 for reading out charges from the photodiodes 5 in the photodiode row 4 corresponding to the first line, and after a lapse of the period 9, the timing generator 11 corresponds to the second line. A read pulse 10 for reading charges from the photodiodes 5 of the photodiode row 4 is generated. The readout unit 1 reads out charges from the photodiodes 5 in the photodiode row 4 corresponding to the second line and outputs the charges as an imaging signal in accordance with the readout pulse 10 generated by the timing generator 11. As described above, the charges accumulated in the photodiodes on the second line during the charge accumulation period 8 are read out by the reader 1. Similarly, after the charges are read from the photodiodes on the third and subsequent lines, the timing generator 11 generates a read pulse 10 for reading the charges from the photodiodes 5 of the photodiode row 4 corresponding to the last line. Generate. The readout unit 1 reads out charges from the photodiodes 5 in the photodiode row 4 corresponding to the last line and outputs the charges as an imaging signal in response to the readout pulse 10 generated by the timing generator 11. As described above, the charges accumulated in each photodiode 5 during the charge accumulation period 8 are read from each photodiode 5.
[0045]
The signal converter 7 performs gamma correction, aperture processing, gain control processing, offset processing on the imaging signal output from the readout unit 1 based on the clock signal, horizontal reference signal, and vertical reference signal generated by the timing generator 11. General signal processing such as control processing is performed to generate an image signal for one frame, and the image signal is stored in the memory 12.
[0046]
The memory controller 13 reads out the image signal for one frame stored in the memory 12 during one frame period in the next frame period, and outputs it via the image signal output terminal 14.
[0047]
As described above, according to the present embodiment, the charges accumulated in the photodiodes 5 constituting the first photodiode row 4 are read out, and then the photodiodes constituting the n-th photodiode row 4 are read out. The entire line readout period 2 until the stored charge is read out is shorter than the one frame period 3 for displaying one frame of image. For this reason, the distortion of the image of the subject caused by the shift along the time axis during the charge accumulation period 8 indicating the period in which the charges are accumulated in the photodiodes 5 constituting the respective photodiode rows 4 is caused by human visibility. It is sufficiently small that it can be ignored in characteristics. As a result, an imaging device capable of obtaining a high-quality image can be provided.
[0048]
Further, according to the present embodiment, the image signal for one frame stored in the memory 12 is read and output by the memory controller 13 during one frame period in the next frame period. For this reason, compatibility with the conventional imaging device can be provided.
[0049]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an imaging device capable of improving the quality of an image of a moving subject.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an imaging device according to an embodiment.
FIG. 2 is a diagram illustrating an image of an imaging surface of a MOS sensor provided in the imaging device according to the present embodiment.
FIG. 3 is a schematic waveform diagram for explaining the operation of the imaging device according to the present embodiment.
FIG. 4 is a block diagram illustrating a configuration of a conventional imaging device.
FIG. 5 is a diagram illustrating an image of an imaging surface of a MOS sensor provided in a conventional imaging device.
FIG. 6 is a schematic waveform diagram for explaining the operation of a conventional imaging device.
7A is a diagram for explaining a conventional imaging device and a subject imaged by the imaging device, and FIG. 7B shows an image of an image of the subject imaged by the conventional imaging device. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Readout device 2 All line readout period 3 1 frame period 4 Photodiode row 5 Photodiode 6 MOS sensor 7 Signal converter 8 Charge accumulation period 9 Period 10 Readout pulse 11 Timing generator 12 Memory 13 Memory controller 100 Imaging device

Claims (8)

A MOS solid-state imaging device (hereinafter, referred to as a “MOS sensor”) that outputs an imaging signal of an object,
An image pickup apparatus comprising: a signal converter that converts the image pickup signal output from the MOS sensor into an image signal for displaying an image of the subject.
The MOS sensor includes n rows (n is an integer of 2 or more) of photodiode rows each including a plurality of photodiodes arranged in a horizontal direction;
A readout unit that sequentially reads out the charges accumulated in each photodiode from the first photodiode row to the nth photodiode row for each photodiode row and outputs the charge as an imaging signal;
The entire line readout period from reading out the charges stored in the photodiodes forming the first photodiode row to reading out the charges stored in the photodiodes forming the nth photodiode row is as follows: An imaging device, wherein the period is shorter than the period in which charges are stored in the photodiode. In the all-line readout period, distortion of the image of the subject due to a shift along the time axis between the charge accumulation periods indicating the periods in which charges are accumulated in the photodiodes constituting each photodiode row is caused by humans. The imaging device according to claim 1, wherein the length of the imaging device is shortened so as to be sufficiently small to be negligible in terms of visibility characteristics. The imaging apparatus according to claim 1, wherein the all-line reading period is shorter than 1/30 second. The imaging apparatus according to claim 1, wherein the readout unit reads out the electric charges stored in each of the photodiodes for each of the photodiode rows according to a predetermined readout pulse. The imaging apparatus according to claim 1, further comprising a timing generator that generates the predetermined read pulse and supplies the read pulse to the reader. The imaging device according to claim 5, wherein the timing generator generates the predetermined read pulse such that the all-line read period is shorter than 1/30 second. The imaging apparatus according to claim 1, further comprising a memory that stores the image signal converted by the signal converter for one frame. The imaging apparatus according to claim 1, further comprising: a memory controller that reads out and outputs the image signals of the one frame stored in the memory during one frame period in a next frame period.

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