JP2004023231A - Imaging device and portable telephone system provided with the imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device for correcting dark current noise including vertical noise without using a frame memory for storing an image signal for one frame with a large capacity. <P>SOLUTION: This imaging device is provided with: a vertical light shielding region signal selection circuit 61 for selecting an image signal outputted from a vertical light shielding region provided at an upper end part, for a plurality of lines, in the laying direction of lines in a light receivable region of an imaging element from signals in the whole light receivable region; a line memory 62 for storing the image signal outputted from the vertical light shielding region signal selection circuit 61 for one line; and a subtraction circuit 32 for subtracting the signal intensity of the image signal stored in the line memory 62 from the signal intensity of an inputted image signal when the image signal existing outside the vertical light shielding region is inputted among signals in the whole light receivable region so that the same image signals may correspond to each other in a horizontal address in the line. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an imaging device using a solid-state imaging device such as a CCD image sensor, and more particularly to an imaging device that corrects dark current noise including vertical noise.
[0002]
[Prior art]
2. Description of the Related Art In recent years, not only have digital still cameras been miniaturized and spread, but also communication devices such as mobile phones and information processing devices such as personal computers with an added imaging function have rapidly spread. As a solid-state imaging device to which an imaging function is added, an image sensor of a solid-state imaging device such as a CCD (Charge Coupled Device) or a MOS (Metal Oxide Semiconductor) image device is generally used. In general, the MOS image device is advantageous for miniaturization, and the CCD is advantageous for image quality. Hereinafter, the case of a CCD will be described.
[0003]
Next, a conventional method of correcting dark current noise including vertical noise will be described.
FIG. 14 is a block diagram of a conventional imaging device for correcting dark current noise including vertical noise, which is disclosed in, for example, Japanese Patent Application Laid-Open No. H11-298762.
[0004]
In the figure, 10 indicates a control circuit, 11 indicates a drive signal generation circuit, 13 indicates an image sensor, 14 indicates a sample and hold circuit, 15 indicates a digital processing unit, and 16 indicates a signal processing circuit. 17, 17 indicates a signal compression circuit, 18 indicates a storage medium, 21 indicates a lens, and 22 indicates a shutter. The digital processing unit 15 includes an analog / digital (A / D) conversion circuit 31, a frame memory 33, and a subtraction circuit 32.
[0005]
When the dark current noise is corrected by the imaging device in FIG. 14, first, the image signal output from the imaging device 13 is converted from an analog signal to a digital signal by the A / D conversion circuit 31 with the shutter 22 closed. The data is converted and stored in the frame memory 33. In this case, since the shutter 22 is closed, the image signal captured and stored in the frame memory 33 is only noise due to dark current. The noise in this case includes, for example, fixed pattern noise generated for each pixel when reading out signal charges due to variation in the characteristics of the scanning semiconductor, and switching generated when the photodiode of the image sensor is reset. Noise and the like.
[0006]
From the characteristics of the CCD and the like, noise due to dark current is conspicuous where the screen is dark, and the noise is reproduced as a fixed noise pattern regardless of the opening and closing of the shutter. The noise due to the dark current increases in proportion to the rise in the temperature of the CCD or its surroundings. In the vertical CCD section when the CCD is divided into a vertical section and a horizontal section in the moving direction of the charge, the charge is controlled by exposure control or the like. Has the characteristic that it increases in proportion to the increase in the accumulation time of the data. Among the fixed noise patterns generated due to the dark current, in particular, regarding the vertical noise generated as a bright line in the vertical transfer CCD unit, the number, the location, and the signal intensity of each solid-state image sensor are not constant and are conspicuous. There is a feature.
[0007]
Regarding the rise in the temperature of the CCD or its surroundings, in recent years, the use environment has deteriorated, and it has been required to be able to cope with a higher temperature environment. This is because, as described above, as a result of incorporating the imaging device into a mobile phone or the like, the portability is improved, and the device is treated as a daily necessity, not as a precision device. It is necessary to do it. Therefore, the dark current noise described above, particularly the vertical noise, is often used in an environment where the noise frequently occurs, and the correction of the dark current noise is becoming more important.
[0008]
The dark current noise may be reduced by, for example, reducing the level of the dark current noise by sampling the difference potential in the cycle of the clock signal using a correlated double sampling (CDS) circuit in the sample and hold circuit 14. Although it can be suppressed, not all dark current noise can be removed. Therefore, the digital processing unit 15 stores the image signal of one frame when the shutter 22 is closed in the frame memory 33 as dark current noise data, and the subtraction circuit 32 stores the image signal when the shutter is opened. The dark current noise is removed by subtracting the value of the data stored in the frame memory 33 from the value of the image signal of the frame.
[0009]
The image signal from which the dark current noise has been removed is subjected to gamma correction, color separation, and the like by the signal processing circuit 16 and compressed by the compression circuit 17 to reduce the capacity (information amount) and to be written to the storage medium 18. .
[0010]
Also, in the method disclosed in Japanese Patent Application Laid-Open No. H11-298762, the digital signal processing unit 15 uses a method described in Japanese Patent Application Laid-Open No. H11-298762 to convert one frame of image signal when the shutter 22 is closed into dark frame noise data as frame data. When storing the data in the memory 33, the signal is compressed and then stored. The subtraction circuit 32 subtracts the value of the compressed data stored in the frame memory 33 from the value obtained by signal compression of the image signal of one frame when the shutter is opened. Thus, in the method disclosed in Japanese Patent Application Laid-Open No. H11-298762, the memory capacity of the frame memory 33 is reduced.
[0011]
[Problems to be solved by the invention]
However, in the conventional dark current noise correction method described in Japanese Patent Application Laid-Open No. H11-298762, a relatively large capacity compressed image signal for one frame is stored in the frame memory 33 although the image signal is compressed. Requires a capacity (memory amount) for writing the data. In product design of most products including an image pickup device in recent years, space saving, cost reduction, and power consumption reduction are inevitable issues. Therefore, it is desired to reduce the amount of memory used. Therefore, the need for a frame memory for one frame of a compressed image signal for the correction of dark current noise means that the capacity in the housing required for the memory and the cost are one frame, and the power consumption of the memory is also low. This is a problem because it means one frame.
[0012]
For example, a line memory that stores only one line of image signal without using a frame memory that stores a relatively large image signal of one frame, or a frame memory that stores only several lines of image signal If it is possible to perform the correction of the dark current noise for each line or every several lines using the above, not only the above-described volume, cost, and power consumption in the housing will be advantageous, but also the correction required for the correction will be required. Although advantageous in terms of processing time, such an imaging device has not been known in the past.
[0013]
An object of the present invention is to provide an imaging device that corrects dark current noise including vertical noise without using a frame memory that stores an image signal for one frame having a large capacity, with the object of solving the above problem. With the goal.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, an image pickup apparatus according to the present invention as set forth in claim 1, wherein a line composed of multi-dot semiconductor light receiving elements is stacked in a light receiving area of the image pickup element in which the lines are arranged in the stacking direction. A vertical light-shielding area signal selecting circuit for selecting an image signal output from a vertical light-shielding area provided for a plurality of lines in at least one of the upper and lower ends in the direction from among signals of all light-receiving areas; A line memory for storing the image signal output from the selection circuit for one line, and a signal intensity of the input image signal when an image signal other than the vertical light-shielded area is input from among the signals of all light-receiving areas. And a subtraction circuit for subtracting the signal strength of the image signal stored in the line memory so that the horizontal address in the line corresponds to the same image signal.
[0015]
According to a second aspect of the present invention, in the image pickup apparatus according to the first aspect, the line memory stores an image signal for one line set in advance from a plurality of lines in the vertical light shielding area.
[0016]
According to a third aspect of the present invention, in the image pickup apparatus according to the first or second aspect, a vertical noise signal for deteriorating image display quality is obtained from an image signal for a plurality of lines output from a vertical light shielding area signal selection circuit. Address and signal strength in the same horizontal address in all the lines of a plurality of lines, and that the signal strength of the vertical noise signal is stronger than other random noise signals, A vertical noise detection circuit for determining and detecting the vertical noise signal based on at least one of the above, and the line memory stores an address and a signal strength in a line of the vertical noise signal output from the vertical noise detection circuit. .
[0017]
According to a fourth aspect of the present invention, there is provided the image pickup apparatus according to the third aspect, further comprising a temperature measurement circuit which is provided in contact with or near the image pickup device in order to measure a temperature change of the image pickup device. The directional noise detection circuit performs detection in accordance with a change in temperature of the image sensor.
[0018]
According to a fifth aspect of the present invention, there is provided the image pickup apparatus according to the first or second aspect, wherein the signal strength of the image signal for at least two lines from the image signals for a plurality of lines output from the vertical light shielding area signal selection circuit. And a light-shielding area signal integrating circuit for integrating the image signal integrated by the light-shielding area signal integrating circuit with the horizontal address of each line. An integration output division circuit for dividing the image signal by the number of lines of the image signal integrated by the integration circuit and outputting the divided image signal, wherein the line memory stores the image signal output from the integration output division circuit.
[0019]
In the image pickup apparatus according to the present invention, at least the upper and lower ends of the lines in the stacking direction of the lines are arranged in the light receiving area of the image sensor in which the lines formed of the multi-dot semiconductor light receiving elements are arranged in the stacking direction. A vertical light-shielding area signal selecting circuit for selecting an image signal output from a vertical light-shielding area provided for a plurality of lines in one of the signals from the entire light-receiving area, and an image output from the vertical light-shielding area signal selecting circuit A light-shielded area frame memory for storing at least two lines of signals, and an output of the image signal stored in the light-shielded area frame memory, the image signal stored in the light-shielded area frame memory being associated with the horizontal address of each line. A division circuit that divides the image by the number of lines and outputs the image. From the signal strength of the signal, the signal strength of the image signal output from the dividing circuit, a horizontal address in line characterized in that it comprises a subtraction circuit for subtracting so as to correspond with the same image signal with each other.
[0020]
According to a seventh aspect of the present invention, there is provided an imaging device having a storage function and an arithmetic function, and capable of changing processing content by an arbitrary program, and the arithmetic circuit according to any one of the first to sixth aspects. And a program memory for storing a program for executing a function of each circuit and each memory in the imaging device described in (1).
[0021]
An eighth aspect of the present invention provides a mobile phone device including the imaging device according to any one of the first to seventh aspects.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on illustrated embodiments.
Embodiment 1 FIG.
[0023]
FIG. 1 is a block diagram illustrating a schematic configuration of the imaging apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a control circuit 10 is, for example, a microcomputer or the like, and controls the operation of the entire imaging apparatus. The drive signal generation circuit 11 generates, for example, a horizontal scanning pulse or a vertical scanning pulse, or generates a clock signal as an original signal thereof. The image sensor 13 outputs an image signal that is converted into an electric signal by photoelectrically converting input light such as a CCD. As the sample and hold circuit 14, for example, a CDS circuit or the like that clamps the reference level of the image signal to a constant voltage, samples and holds the signal level, and outputs a potential difference between the reference level and the signal level is used.
[0024]
The digital processing unit 15 corrects dark current noise in the image signal. The lens 21 focuses input light (optical image) incident from the outside on the image sensor 13 described later. The shutter 22 switches between transmitting and blocking input light. The signal processing circuit 16 performs signal processing such as gamma correction, color separation, and white balance on the image signal, for example. The signal compression circuit 17 performs a compression process on the image signal. The storage medium 18 stores an image signal.
[0025]
In the digital processing unit 15, an A / D conversion circuit 31 that converts an image signal in an analog signal format into a digital signal format, and selects an image signal in a vertical light-shielded region, which will be described later, from image signals of one frame, and A vertical light shielding area signal selecting circuit 61 for outputting one line, a line memory 62 for storing the image signal of the vertical light shielding area for one line selected by the vertical light shielding area signal selecting circuit 61, and a newly input image signal And a subtraction circuit 32 for subtracting the level of the line of the image signal stored in the line memory 62 from the level of each line. In the present embodiment, the frame memory 33 for storing the image signal for one frame shown in FIG. 14 is not provided. Therefore, the subtraction circuit 32 does not perform the subtraction of the image signal for one frame, but performs the subtraction of the image signal for one line.
[0026]
The drive signal generation circuit 11 supplies a drive pulse to the image sensor 13 and supplies a horizontal synchronization signal and a vertical synchronization signal to the sample and hold circuit 14 and the digital processing unit 51. The control circuit 10 outputs a control signal for controlling the drive signal generation circuit 11, the digital processing unit 51, the signal processing circuit 16, the signal compression circuit 17, and the storage medium 18.
[0027]
The image signal output from the imaging element 13 is supplied to the A / D conversion circuit 31 in the digital processing unit 51 after the sample and hold processing is performed by the sample and hold circuit 14.
[0028]
The A / D conversion circuit 31 performs an automatic gain control (AGC) process on the image signal, and converts the analog signal into a digital signal. The image signal in the digital signal format output from the A / D conversion circuit 31 supplies the image signal to the subtraction circuit 6 of one of the branched systems and the same image signal to the light-shielded area signal integration circuit 81 of the other system. Supply signal. The number of bits of the digital signal output from the A / D conversion circuit 31 is, for example, 10 bits in the case of the present embodiment.
[0029]
FIG. 2 shows the arrangement of the vertical transfer CCD section / horizontal transfer CCD section in the CCD in the image pickup apparatus of the present embodiment, the arrangement of the effective pixel area / vertical light shielding area / horizontal light shielding area in the light receiving area (sensor area), FIG. 4 is a diagram illustrating a positional relationship between vertical noises.
[0030]
The CCD 13 serving as an image pickup device includes a vertical transfer CCD unit 40 in which electric charge of each pixel formed of a semiconductor light receiving element is transferred in a vertical (up / down) direction, and an electric charge transferred from the vertical CCD 40 in a horizontal direction sequentially for each line. To the horizontal transfer CCD unit 41 for input to the output unit 48. The output unit 48 converts the electric charge transferred from the horizontal transfer CCD unit 41 into a signal voltage and outputs the signal voltage to, for example, the sample and hold circuit 14.
[0031]
The vertical transfer CCD unit 40 obtains an effective pixel area 46 as an imaging area and a black reference in an entire light-receiving area (sensor area) in which lines composed of multi-dot semiconductor light receiving elements are arranged in the stacking direction. Of light-shielding areas 47. The light-shielding region 47 further includes a vertical light-shielding region 47a provided for a plurality of lines at the upper end in the line stacking direction, and a horizontal pixel provided for a plurality of pixels (dots) at the right end of the effective pixel region 46 and the vertical light-shielding region 47a. And a light-shielding region 47b.
[0032]
The vertical light shielding area 47a is an area for determining a vertical black reference, and the horizontal light shielding area 47b is an area for determining a horizontal black reference. In the present embodiment, the number of lines in the pixel array in the vertical light-shielding region 47a is eight, and the number of pixels in the pixel array in the horizontal light-shielding region 47b is 30.
[0033]
The vertical noise signal 49 is a noise signal that appears not only in the effective pixel area 46 (video area) but also uniformly at the same horizontal address in the vertical light shielding area 47a, and has a correlation in the vertical direction (stacked in the vertical direction). Appearing at the same horizontal address of each line). Also, since the vertical noise signal 49 originally enters the vertical light-shielding region 47a for obtaining the vertical black reference, the calculation of the black reference value of the vertical noise signal 49 requires the vertical noise reference. The signal strength of the signal 49 will be obtained. Therefore, if the value of the vertical noise signal 49 detected in the vertical light shielding area 47a is subtracted from the effective image signal of the same horizontal address in the effective pixel area 46 (= including the vertical noise signal 49), the vertical noise signal Thus, it is possible to obtain a normal image without any adverse effect due to 49.
[0034]
In the light receiving area of the CCD 13, lines composed of multi-dot semiconductor light receiving elements (photodiodes) are arranged in the stacking direction, and a vertical light shielding area 47a is provided at the upper end of the line in the stacking direction as shown in FIG. However, depending on the mounting direction of the CCD 13, it may be the lower end.
[0035]
FIG. 3 is a schematic diagram illustrating a basic configuration of a CCD in the imaging device according to the present embodiment.
In the figure, reference numeral 46a denotes a photodiode having a photoelectric conversion function of converting incident light (optical image) into signal charges. Reference numeral 40 denotes a vertical transfer CCD. The signal charge photoelectrically converted by the photodiode is transferred to the vertical transfer CCD after a predetermined time, and then transferred to the horizontal transfer CCD 41. The vertical noise signal 49 shown in FIG. 2 has the same horizontal address of all lines in the light receiving area SA (= light receiving area = sensor area) in which the effective pixel area 46 (image area) and the vertical light shielding area 47a are combined. And a dark current generated in a fixed pattern in common with the vertical transfer CCD.
[0036]
FIG. 4 is a diagram illustrating an example of a signal level distribution of an image signal for an arbitrary one line in a vertical light shielding area of a CCD in the imaging apparatus according to the present embodiment.
[0037]
The horizontal axis is the position of the horizontal pixel, and the vertical axis is the signal level. As shown in the figure, the signal level of the image signal (noise) of the horizontal address generated by the vertical noise signal 49 is lower than the signal level of the image signal (noise) of the random noise 49a generated at other horizontal address locations. It is a prominent value.
[0038]
Here, first, the dark current will be further described. The dark current is charge accumulated with the passage of time even when light is blocked. In a CCD, dark current appears as a fixed pattern, and the number of occurrences is usually doubled for a temperature rise of 7 to 8 ° C. The dark current is added to the signal charges in the vertical transfer CCD 40 when the signal charges are transferred by the vertical transfer CCD 40. Also, in the case of the charge image indicated by the vertical noise signal 49 in FIG. 2 in the dark current, the signal intensity of the noise signal increases as the temperature of the image pickup device (CCD) 13 increases. However, when the charge transfer speed is reduced by the exposure control and the charge accumulation time in the vertical transfer CCD is extended, the signal strength of the noise signal is increased accordingly.
[0039]
FIG. 5 is a flowchart of an operation of correcting dark current noise including vertical noise in the imaging device 1 according to the first embodiment of the present invention.
[0040]
The charge of one line from the vertical transfer CCD 40 of the image pickup device 13 is transferred to the horizontal transfer CCD 41 and the output unit 48 in this order and output as an image signal. Is transferred to the A / D conversion circuit 31 (S1).
[0041]
An image signal is output from the A / D conversion circuit 31 to the subtraction circuit 32 and the vertical light shielding area signal selection circuit 61. The vertical light shielding area signal selection circuit 61 detects whether or not a vertical synchronizing signal is input in the input image signal (S2). If the vertical synchronization signal is detected (S2: YES), the stored contents of the line memory 62 are cleared (S3). If the vertical synchronization signal is not detected (S2: NO), the input image signal is It is determined whether the signal is not a signal from the effective pixel area but a signal from the vertical light shielding area (S4). If the signal is from the vertical light-blocking area (S4: YES), it is determined whether or not the image signal is from a specific line in which it is confirmed in advance that there are no missing pixels in a plurality of lines in the vertical light-blocking area. Is performed (S5). If the specific line is a line having a defect in a pixel in the line, there is a possibility that the correction accuracy of the vertical noise may be deteriorated. Each line in the line may be inspected, and any pixel in the line may be arbitrarily selected from those having no defect.
[0042]
If the signal is not a signal from the vertical light shielding area (S4: NO), it means that the image signal is from the effective pixel area. Therefore, the stored content is read from the line memory 62 (S8), and the effective pixel area is read by the subtraction circuit 32. Then, the content stored in the line memory 62 is subtracted from the image signal received from the CPU (S9), and the presence or absence of the image signal of the next line is confirmed (S7). Note that the processing corresponding to the first line immediately after the start of the input of the image signal of one frame after the vertical synchronization signal is a vertical light-blocking area, so the processing branches off in step S4 and the processing in step S8 is not performed. Otherwise, since the data of the image signal (dark current noise) has not been written in the line memory 62, the processing in step S8 is not performed. The processing in step S8 is performed on the second and subsequent lines after the input of the image signal of one frame after the vertical synchronization signal is started.
[0043]
When the input image signal is an image signal from a specific line (S5: YES), the image signal is written into the line memory 62 (S6), and when the input image signal is not an image signal from the specific line (S5: NO). Is checked for the presence or absence of the image signal of the next line (S7).
[0044]
If there is an image signal of the next line (S7: NO), the process returns to step S1 to process the image signal of the next line, and if there is no image signal of the next line (S7: YES), the process ends. I do.
[0045]
In step S9, the output from the line memory 62 is supplied to the subtraction circuit 6. The subtraction circuit 6 converts the image signal including the vertical noise signal 49 output line by line from the effective pixel area 46 of the image sensor 13 into an image signal of only the vertical noise signal 49 stored in the line memory 62 (fixed). Pattern noise signal). Then, only the component of the vertical noise signal 49 is removed from the image signal of the effective pixel area 46, and the next signal processing circuit 16 processes a good image signal in which the vertical noise has been corrected. And a good image can be reproduced.
[0046]
The image signal stored in the line memory 62 in step S6 is a fixed value during the period in which the image signal of one frame is supplied, and the vertical noise of the image signal for each line of the effective pixel area 46 in steps S8 and S9. Used for correcting the signal 49.
[0047]
As described above, in the imaging apparatus according to the present embodiment, the image signal can be corrected by removing the vertical noise generated by the dark current without using the frame memory, and a good image signal can be output. In addition, when inspecting each line in the vertical light-shielded area on a manufacturing line of an imaging device and arbitrarily selecting pixels having no defects in the pixels in the line, it is necessary to avoid deterioration in the correction accuracy of the vertical noise. it can.
[0048]
Embodiment 2 FIG.
FIG. 6 is a block diagram illustrating a schematic configuration of an imaging device according to Embodiment 2 of the present invention.
The imaging device 2 according to the present embodiment illustrated in FIG. 6 and the imaging device 1 according to the first embodiment illustrated in FIG. 1 are partially different in the internal configuration of the digital processing unit 52, and the other configurations are the same as those according to the first embodiment. Is the same as
[0049]
The digital processing unit 52 has a vertical noise detection circuit 71 for detecting a horizontal address where a vertical noise occurs in an image signal of a specific line, in addition to the same configuration as in the first embodiment. As a detection method, for example, as shown in FIG. 4, detection is performed by setting a threshold value or the like by utilizing that the signal level of the vertical noise signal 49 is more prominent than other random noise. Can be.
[0050]
The vertical noise detection circuit 71 determines the address and signal strength of the vertical noise signal 49 for deteriorating the image display quality from a plurality of lines of the image signals output from the vertical light shielding area signal selection circuit 61 by a plurality of lines. And that the signal strength of the vertical noise signal 49 is higher than that of the other random noise signals 49a. I do.
[0051]
FIG. 7 is a flowchart of an operation of correcting dark current noise including vertical noise in the imaging device 2 according to the second embodiment of the present invention.
[0052]
The flowchart of the present embodiment shown in FIG. 7 is different from the flowchart of the first embodiment shown in FIG. 5 in that the image signal input in step S5 is an image signal from a specific line (S5: YES). Before writing the image signal into the line memory 62 (S6), the vertical noise detection circuit 71 detects a horizontal address in the image signal at which vertical noise occurs (S11). But others are the same.
[0053]
In the present embodiment, by detecting the horizontal address in the image signal at which the vertical noise occurs, the writing to the line memory in step S6 is limited to the horizontal address at which the vertical noise occurs. As a result, the line memory reading in step 8 and the process of subtracting the read data from the image data in step S9 only need to be performed for the horizontal address at which the vertical noise occurs, and therefore the vertical noise in the imaging device is included. Processing efficiency and processing speed for correcting dark current noise can be improved.
[0054]
As described above, in the imaging device of the present embodiment, the image signal can be corrected by removing the vertical noise generated by the dark current without using the frame memory, and in addition to being able to output a good image signal, Thus, processing efficiency and processing speed for correcting dark current noise including vertical noise can be improved.
[0055]
Embodiment 3 FIG.
FIG. 8 is a block diagram illustrating a schematic configuration of an imaging device according to Embodiment 3 of the present invention.
In the image pickup device 2a of the present embodiment shown in FIG. 8 and the image pickup device 2 of the embodiment 2 shown in FIG. A temperature measurement circuit 19 is provided in the second embodiment, and the vertical noise detection circuit 71 performs detection in accordance with a change in the temperature of the image sensor 13, but the other configuration is the same as that of the second embodiment.
[0056]
The temperature measurement circuit 19 is configured by, for example, a thermocouple or the like, and is installed in contact with the housing of the imaging device 13. Then, the voltage according to the temperature change of the image sensor 13 is input to the control circuit 10 by the temperature measurement circuit 19. The vertical noise detection circuit 71 detects a vertical noise signal 49 when a temperature change is detected by the temperature measurement circuit 19.
[0057]
As an operation of correcting the dark current noise including the vertical noise in the imaging device 2a of the present embodiment, the image signal input in step S5 in the flowchart of the present embodiment shown in FIG. If the signal is an image signal (S5: YES), the temperature measurement result changes before the vertical noise detection circuit 71 detects a horizontal address in the image signal at which vertical noise occurs (S11). It is determined whether or not there is, and if there is a change in the temperature measurement result, the process proceeds to step S11, where the vertical noise signal 49 is detected and written into the line memory. Steps S11 and S6 are omitted and, for example, the data written in the line memory in one previous frame is used, but the other is the same.
[0058]
In the present embodiment, the vertical noise signal 49 generally fluctuates when the temperature changes, but is generated fixedly when the temperature is constant. When the temperature does not change in cooperation with the temperature measurement result, the image signal data of the vertical noise detected from the image signal of the previous one frame and already written in the line memory is used, and a new horizontal address is used. Detection and writing to the line memory were not performed. As a result, when the temperature is constant, the process of detecting the vertical noise signal 49 and writing it to the line memory is omitted, so that useless processing is eliminated, and the processing efficiency of correcting dark current noise including vertical noise in the imaging apparatus. And increase the processing speed, so that extra power is not consumed.
[0059]
As described above, in the imaging apparatus according to the present embodiment, the image signal can be corrected by removing the vertical noise generated by the dark current without using the frame memory, and a good image signal can be output. In addition to being able to improve the processing efficiency and processing speed for correcting dark current noise including directional noise, eliminating unnecessary processing and consuming no extra power, the processing efficiency and processing speed are further improved. Can be.
[0060]
Embodiment 4 FIG.
FIG. 9 is a block diagram illustrating a schematic configuration of an imaging device according to Embodiment 4 of the present invention.
The imaging device 3 according to the present embodiment illustrated in FIG. 9 and the imaging device 1 according to the first embodiment illustrated in FIG. 1 are partially different in the internal configuration of the digital processing unit 53, and the other configurations are the same as those according to the first embodiment. Is the same as
[0061]
In the digital processing unit 53, in addition to the same configuration as in the first embodiment, a light-shielded area signal integration circuit 81 that integrates image signals of a plurality of specific lines, and an integrated output of the light-shielded area signal integration circuit 81, An integrated output division circuit 82 for dividing by the integrated specific number of lines is provided.
[0062]
The light-shielded area signal integration circuit 81 integrates the signal strength of at least two lines of image signals from the image signals of a plurality of lines output from the vertical light-shielded area signal selection circuit 61 so as to correspond to the horizontal address of each line. (to add. The integral output division circuit 82 divides the result of the integration (addition) by the specific number of lines to obtain an average value.
[0063]
FIG. 10 is a flowchart of an operation of correcting dark current noise including vertical noise in the imaging device 3 according to Embodiment 4 of the present invention.
[0064]
The flowchart of the present embodiment shown in FIG. 10 is different from the flowchart of the first embodiment shown in FIG. 5 in that the image signal input in step S5 is an image signal from a specific line (S5: YES). ), Before the image signal is written into the line memory 62 (S6), the light-shielded area signal integration circuit 81 integrates (adds) the image signals of the plurality of specific lines (S21), and the integration (addition). ) The difference is that the result is divided by the specific number of lines to obtain an average value, but the other is the same. The vertical light-shielding region 47a has, for example, eight lines, and sets the number of specific lines to four.
[0065]
The average value stored in the line memory 62 is a fixed value during the period in which the image signal of one frame is supplied, and is a fixed value of the vertical noise signal 49 and the random noise 49 a of the image signal for each line of the effective pixel area 46. Used for correction.
[0066]
In the present embodiment, an average value is obtained from the image signals of a plurality of specific lines, and in the writing to the line memory in step S6, the average value is written. As a result, in the line memory reading in step 8 and the process of subtracting the read data from the image data in step S9, the average value is read and the average value is subtracted from the input image signal. In addition to the vertical noise of the fixed pattern, random noise of each specific line can be averaged and detected.
[0067]
For example, as for the vertical noise signal 49 shown in FIG. 4, since the signal (intensity) level is prominent and the position of the generated horizontal address is fixed, no matter which specific line is selected in which vertical light shielding area. Although the signal (intensity) level can be detected with a uniform signal intensity, the signal (intensity) level is smaller than the vertical noise signal 49 and changes with time, and a random noise component 14a generated at a random horizontal address position in a comb-like manner is represented by one line It cannot be specified (detected) with an image signal.
[0068]
Therefore, in the present embodiment, a random noise component other than the vertical noise component in the dark current is specified (detected) by calculating the averaging for the specific number of lines, and the component is also used as the image in the effective pixel area. Correction accuracy is further improved by subtracting from the data.
[0069]
In the averaging performed in steps S21 and S22, the image signal data of the specific line being processed and the image signal data newly determined to be the specific line in step S5 are simply added and divided by two. Instead, take the averaging while weighting.
[0070]
For example, when writing the image signal data of the first line in the specific line of the vertical light-shielded area to the line memory 62 as a, the averaging of the image signal data b of the second line and the image signal data a of the first line is performed. The image signal data calculated and written in the line memory 62 is (a + b) / 2. Next, when the image signal data c on the third line and the image signal data (a + b) / 2 on the 1 + 2 line are simply averaged, the result is (a + b + 2c) / 2, not (a + b + c) / 3. Therefore, for example, the image signal data is weighted for each line so that a value obtained by adding and averaging the image signal data of the third line and writing it as (a + b + c) / 3 is written in the line memory 62. Although the case where the number of specific lines (n) is three has been described above, the average value written in the line memory 62 is also (a + b + c +) when the number of specific lines (n) is four or more. .. + N) / n is weighted for image signal data for each line.
[0071]
In particular, when the imaging device is incorporated in a mobile phone device, it is assumed that the imaging device will be used in a high-temperature environment as described above. Below, random noise also increases. Therefore, if the random noise component of the dark current is also detected and averaged from the image data of a plurality of specific lines as in the present embodiment, and the component is also reduced from the image data of the effective pixel area, the high-temperature It is possible to prevent a decrease in correction accuracy due to the influence of random noise that increases in an environment.
[0072]
In the present embodiment, the vertical light shielding area 47a is set to 8 lines, and the specific number of lines is set to 4. However, as long as the specific line number does not exceed the number of lines in the vertical light shielding area 47a. Any number may be set.
[0073]
In addition, the light-shielding area signal integration circuit 81 selects any one of the lines in the vertical light-shielding area 47a as a specific line and averages its image signal, thereby improving the detection accuracy of the vertical noise signal 49. And the accuracy of correction can be increased.
[0074]
For example, when a defective pixel is found in the vertical light-shielding region 47a during product inspection on a product line of an imaging device or the like, for example, one line including the pixel is excluded from the specific line for performing averaging. By doing so, a line including only normal pixels can be set as a specific line. From the specific line, a plurality of continuous lines or an arbitrary discontinuous line may be freely selected in combination, or all may be selected.
[0075]
As described above, in the imaging apparatus according to the present embodiment, the image signal can be corrected by accurately removing the vertical noise generated by the dark current without using the frame memory, and a good image signal can be output. In addition, random noise components can also be removed and corrected, and the correction accuracy can be further improved.
[0076]
Embodiment 5 FIG.
FIG. 11 is a block diagram illustrating a schematic configuration of an imaging device according to Embodiment 5 of the present invention.
The imaging device 4 according to the present embodiment illustrated in FIG. 11 and the imaging device 3 according to the fourth embodiment illustrated in FIG. 9 are partially different in the internal configuration of the digital processing unit 54, and the other configurations are the same as those according to the fourth embodiment. Is the same as
[0077]
In the digital processing unit 54, instead of the light-shielded area signal integration circuit 81 of the fourth embodiment, a light-shielded area frame memory 91 for storing image signals of a plurality of specific lines in a vertical light-shielded area, Is divided by the stored specific number of lines. In the present embodiment, the line memory 62 is not provided.
[0078]
The light-shielded area frame memory 91 stores image signal values of a plurality of (at least two or more) specific lines selected from the vertical light-shielded area. The light-shielded area frame memory 91 may store the values of the image signals of all the specific lines. The division circuit 92 divides the stored content by the stored specific number of lines to obtain an image signal for one line (vertical noise component + random noise component).
[0079]
FIG. 12 is a flowchart of an operation of correcting dark current noise including vertical noise in the imaging device 4 according to Embodiment 5 of the present invention.
[0080]
The flowchart of the present embodiment shown in FIG. 12 is different from the flowchart of the fourth embodiment shown in FIG. 10 in that the image signal input in step S5 is an image signal from a specific line (S5: YES). ), The image signal is written to the light-shielded area frame memory 91 (S32), and the integration (addition) processing of the image signal before writing to the light-shielded area frame memory 91 is eliminated. However, since the image signals for a plurality of specific lines are stored in the light-shielded area frame memory 91, the stored content is divided by the specific number of lines to obtain an image signal for one line (vertical noise component + random noise component). The same is true for the determination of the component).
[0081]
If the image signal input in step S4 is not the image signal from the vertical light shielding area 47a (S4: NO), the image signals for a plurality of specific lines are read from the light shielding area frame memory 91 instead of the line memory. The image signal (vertical direction noise component + random noise component) for one line is obtained by dividing by the specific number of lines stored in the division circuit 92, and the other is the same.
[0082]
By employing the light-shielded area frame memory 91 instead of the line memory 62, when detecting the vertical noise signal 49 in the vertical light-shielded area 47a, the image signals for a specific number of lines are collectively stored (stored). The division circuit 92 thereafter calculates the vertical noise plus random noise component for one line by dividing the content stored in the light-shielded area frame memory 91 by the specific number of lines.
[0083]
In the present embodiment, since the frame memory of the vertical light shielding area is used instead of the line memory, an average obtained by integrating or adding the image signals for each line of the vertical light shielding area and dividing by the specific number of lines is stored. It is no longer necessary to store the image signal for each of the plurality of lines in the frame memory as it is, and divide the image signal by the specific number of lines immediately before subtraction by the subtraction circuit 32. Further, in the present embodiment, even if the frame memory is used, not all image data for one frame including the effective pixel area is stored, but a specific line of the vertical light shielding area (for example, 8 (For the line) is stored in the light-shielded area frame memory 91. Therefore, what is stored in the light-shielding area frame memory 91 is the image signal data of only a few lines (for example, eight lines) designated as the vertical light-shielding area, and all the lines of the effective pixel area as in the related art. The memory capacity is much smaller than when storing the data.
[0084]
As described above, in the present embodiment, since the light-shielded area frame memory 91 is used, it is only necessary to calculate the data of one line of vertical noise by dividing by the specific number of lines in the stage before the subtraction (S9). As in the fourth embodiment, the image signal can be corrected by accurately removing the vertical noise generated by the dark current without using the frame memory for the entire frame, and in addition to outputting a good image signal, In addition to removing and correcting noise components, it is not necessary to once add an image signal for each line, so the circuit can be simplified and processing efficiency for correcting dark current noise including vertical noise can be improved. Processing speed can be improved.
[0085]
Embodiment 6 FIG.
FIG. 13 is a block diagram illustrating a schematic configuration of an imaging device according to Embodiment 6 of the present invention.
The imaging apparatus 5 according to the present embodiment illustrated in FIG. 13 and the other embodiments illustrated in FIGS. 1, 6, 9, and 11 are partially different in the internal configuration of the digital processing unit 55. Other configurations are the same as those of each embodiment.
[0086]
In the digital processing unit 55, instead of the vertical light shielding area signal selection circuit 61, the line memory 62, and the subtraction circuit 32 of the first embodiment, for example, various programs such as a microcomputer (CPU: central processing element) are used. Operation circuit 101 capable of performing various operations. The arithmetic circuit 101 includes a program memory 101a.
[0087]
The arithmetic circuit 101 replaces the vertical light shielding area signal selection circuit 61, the line memory 62, the vertical noise detection circuit 71, and the subtraction circuit 32 in the second embodiment by changing the program. In the case of the fourth embodiment, it replaces the vertical light shielding area signal selection circuit 61, the line memory 62, the light shielding area signal integration circuit 81, the integration output division circuit 82, and the subtraction circuit 32. In this case, it replaces the vertical light shielding area signal selection circuit 61, the light shielding area frame memory 91, the division circuit 92, and the subtraction circuit 32.
[0088]
That is, in the present embodiment, the functions realized by hardware in the first to fourth embodiments are realized by software by the program and the arithmetic circuit 101. Therefore, the operation of this embodiment is the same as any one of the flowcharts of FIGS. 5, 7, 10, and 12 corresponding to each of the above embodiments.
[0089]
Further, in the present embodiment, since the arithmetic circuit 101 capable of easily changing the processing content by changing the program is used, for example, the vertical noise signal 49 is detected from the image signal of the vertical light shielding area 47a. In such a case, statistical processing based on the horizontal address data of the acquired vertical noise signal 49 can be performed.
[0090]
Statistical processing in this case is processing of calculating the maximum value, the minimum value, the average, the standard deviation, and the like of image signals (signals in a vertical light-shielded region) of several lines having the same horizontal address, and using the calculation results. It is. For example, first, a standard deviation is calculated for several lines of image signals (signals in the vertical light-shielded region) having the same horizontal address, and by referring to the standard deviation value, the vertical noise and the signal intensity of data for each line are not constant. By selecting random noise, it becomes possible to correct only vertical noise.
[0091]
As described above, in the present embodiment, the arithmetic circuit 101 operated by a program is used, so that any of the processing contents described in the first to fourth embodiments can be easily changed. Statistical processing is performed on each data for correcting noise used in the first to fourth embodiments, so that the correction accuracy can be further improved.
[0092]
Further, when each of the above-described embodiments is applied to an imaging device incorporated in a mobile phone device, the mobile phone device is often used in a high-temperature environment. The effect of correcting the current noise becomes even more remarkable. Therefore, when the imaging device of the present invention is used in a mobile phone device, even when the imaging device of the mobile phone device is used in a high-temperature environment, dark current noise including vertical noise is corrected and good imaging is performed. can do
[0093]
In each of the above-described embodiments, a case where a CCD is used as an image sensor is described. However, the present invention can be applied to other solid-state image sensors such as a MOS image device. Further, the imaging device of the present invention can be applied not only to a digital still camera and an imaging device incorporated in the above-described mobile phone, but also to a case where the imaging device is incorporated in an information processing device such as another communication device or a personal computer. Similarly, the above effects can be obtained.
[0094]
【The invention's effect】
Since the present invention is configured as described above, it has the following effects.
According to the first aspect of the present invention, the vertical light shielding area signal is selected and stored in the line memory. Therefore, the image signal can be corrected by removing the vertical noise generated by the dark current without using the frame memory. It is possible to output various image signals.
[0095]
According to the second aspect of the present invention, each line in the vertical light-shielded area is inspected in a manufacturing line of an imaging device or the like, and pixels in the line are arbitrarily selected from those having no defect. Deterioration of the correction accuracy of the vertical noise can be avoided.
[0096]
According to the third aspect of the present invention, the vertical noise is detected from the vertical light-shielded area signal and the data is stored in the line memory using the horizontal address thereof. Processing efficiency and processing speed for correcting current noise can be improved.
[0097]
According to the fourth aspect of the present invention, the temperature of the image sensor is measured, and when the temperature does not change, the detection of the vertical noise signal and the storage of the data in the line memory are omitted, and the image of the previous frame is omitted. Since the data obtained from the signal is used, unnecessary processing is eliminated and unnecessary power is not consumed, so that processing efficiency and processing speed can be further improved.
[0098]
According to the fifth aspect of the present invention, since the light shielding area signal integration circuit and the integration output division circuit are used, in addition to the above-described effects, the random noise component can be removed and corrected, and the correction accuracy can be further improved. Can be done.
[0099]
According to the sixth aspect of the present invention, since the light-shielded area frame memory that does not need to once add the image signal for each line is used, in addition to the above-described effect, the image signal is divided by the specific number of lines before the subtraction to obtain one line. , The circuit can be simplified, and processing efficiency and processing speed for correcting dark current noise including vertical noise can be improved.
[0100]
According to the seventh aspect of the present invention, since the arithmetic circuit operated by the program is used, in addition to the above-described effects, the processing content can be easily changed, and the statistical processing is performed on each data for noise correction. By carrying out, the correction accuracy can be further improved.
[0101]
According to the eighth aspect of the present invention, since the imaging device of the present invention is used in the mobile phone device, even when the imaging device of the mobile phone device is used in a high-temperature environment, dark current noise including vertical noise is corrected. And an image can be satisfactorily captured.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of an imaging device according to a first embodiment of the present invention.
FIG. 2 shows the arrangement of a vertical transfer CCD unit / horizontal transfer CCD unit in a CCD, the arrangement of an effective pixel area / vertical light shielding area / horizontal light shielding area in a light-receiving area (sensor area), and FIG. 5 is a diagram illustrating a positional relationship of vertical noise.
FIG. 3 is a schematic diagram illustrating a basic configuration of a CCD in the imaging device of FIG. 1;
FIG. 4 is a diagram illustrating an example of a signal level distribution of an image signal for an arbitrary line in a vertical light shielding area of a CCD in the imaging device of FIG. 1;
FIG. 5 is a flowchart of an operation of correcting dark current noise including vertical noise in the imaging device of FIG. 1;
FIG. 6 is a block diagram illustrating a schematic configuration of an imaging device according to a second embodiment of the present invention.
FIG. 7 is a flowchart of an operation of correcting dark current noise including vertical noise in the imaging device of FIG. 6;
FIG. 8 is a block diagram illustrating a schematic configuration of an imaging device according to a third embodiment of the present invention.
FIG. 9 is a block diagram illustrating a schematic configuration of an imaging device according to a fourth embodiment of the present invention.
FIG. 10 is a flowchart of an operation of correcting dark current noise including vertical noise in the imaging device of FIG. 9;
FIG. 11 is a block diagram illustrating a schematic configuration of an imaging device according to a fifth embodiment of the present invention.
12 is a flowchart of an operation of correcting dark current noise including vertical noise in the imaging device of FIG. 11;
FIG. 13 is a block diagram illustrating a schematic configuration of an imaging device according to a sixth embodiment of the present invention.
FIG. 14 is a block diagram of a conventional imaging device that corrects dark current noise including vertical noise.
[Explanation of symbols]
1, 2, 2a, 3, 4, 5, 200 imaging device, 10 control circuit, 11 drive signal generation circuit, 13 imaging device, 14 sample hold circuit (CDS circuit), 15 digital processing unit, 16 signal processing circuit, 17 Signal compression circuit, 18 storage medium, 19 temperature measurement circuit, 21 lens, 22 shutter, 31 analog / digital (A / D) conversion circuit, 32 subtraction circuit, 33 frame memory, 40 vertical transfer CCD, 41 horizontal transfer CCD, 46 Effective pixel area, 46a photodiode, 47 shading area, 47a vertical shading area, 47b horizontal shading area, 48 output section, 49 vertical noise signal (component), 49a random noise signal (component), 61 vertical shading area signal selection circuit , 62 line memory, 71 vertical noise detection circuit, 81 shading area signal Min circuit 82 integrated output division circuit, 91 light shielding area frame memory, 92 division circuit, SA light-receiving region.

Claims (8)

In the light receiving area of the imaging device in which the lines composed of the multi-dot semiconductor light receiving elements are arranged in the stacking direction, from the vertical light shielding area provided for a plurality of lines in at least one of the upper and lower ends of the lines in the stacking direction A vertical light shielding area signal selection circuit for selecting an image signal to be output from signals in the entire light receiving area;
A line memory for storing an image signal output from the vertical light shielding area signal selection circuit for one line;
When an image signal other than the vertical light-shielded area is input from among the signals of the entire light-receiving area, the signal strength of the image signal stored in the line memory is calculated based on the signal strength of the input image signal. And a subtraction circuit for performing subtraction so that the horizontal addresses correspond to the same image signal. 2. The image pickup apparatus according to claim 1, wherein the line memory stores a preset one-line image signal from a plurality of lines in the vertical light-blocking area. From the image signals for a plurality of lines output from the vertical light-shielding area signal selection circuit, a vertical noise signal generated in common with the same horizontal address of the plurality of lines and having a signal intensity larger than that of other noise signals, Vertical noise detection circuit to detect the horizontal address and signal strength of
The imaging apparatus according to claim 1, wherein the line memory stores an address and a signal strength in a line of the vertical noise signal output from the vertical noise detection circuit. In order to measure a temperature change of the image sensor, a temperature measurement circuit is provided in contact with or near the image sensor,
The imaging apparatus according to claim 3, wherein the vertical noise detection circuit performs detection in accordance with a temperature change of the imaging device. From a plurality of lines of image signals output from the vertical light-shielding area signal selection circuit, a light-shielding area signal integration circuit for integrating signal strengths of image signals for at least two lines so as to correspond to a horizontal address of each line;
Integral output division in which the output of the image signal integrated by the light-shielding area signal integration circuit is divided by the number of lines of the image signal integrated by the light-shielding area signal integration circuit and output while corresponding to the horizontal address of each line. And a circuit,
The imaging device according to claim 1, wherein the line memory stores an image signal output from the integration output division circuit. In the light receiving area of the imaging device in which the lines composed of the multi-dot semiconductor light receiving elements are arranged in the stacking direction, from the vertical light shielding area provided for a plurality of lines in at least one of the upper and lower ends of the lines in the stacking direction A vertical light shielding area signal selection circuit for selecting an image signal to be output from signals in the entire light receiving area;
A light-shielded area frame memory for storing image signals output from the vertical light-shielded area signal selection circuit for at least two lines;
A division circuit that divides the output of the image signal stored in the light-shielded region frame memory by the number of lines of the image signal stored in the light-shielded region frame memory and outputs the image signal while corresponding to the horizontal address of each line;
When an image signal other than the vertical light-shielded area is input from among the signals of the all light-receiving areas, the signal strength of the image signal output from the division circuit is calculated from the signal strength of the input image signal in a line. And a subtraction circuit for performing subtraction so that the horizontal addresses correspond to the same image signal. An arithmetic circuit having a storage function and an arithmetic function and capable of changing processing contents by an arbitrary program;
7. An image pickup apparatus comprising: an arithmetic circuit; and a program memory for storing a program for executing a function of each circuit and each memory in the image pickup apparatus according to claim 1. A mobile phone device comprising the imaging device according to claim 1.

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