JP2002281388A - Imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of image quality due to the increase of defects of pixel over aging without generating problems in accordance with generation of time lag to be generated due to detection of detect data for compensation of the defects of pixel. SOLUTION: In a digital camera having an EEPROM 201 to register a pixel defect address as the defect data and a defect compensating part 202 to perform a compensation processing by adjacent pixel data based on the registered defect data, it is constituted so as to cope with deterioration of the defects of pixel over aging by providing a defect data detecting part 203 to newly detect the pixel defect address by analyzing the output of an image pickup device to be obtained at a state that incident light to the image pickup device is shielded and a defect data managing part 204 to update the defect data registered in the EEPROM 201 based on the newly detected defect data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an imaging device such as an electronic still camera (digital camera) or a video camera, and more particularly to an imaging device having a pixel defect compensation function.

[0002]

2. Description of the Related Art In recent years, electronic still cameras have been developed mainly for capturing and recording still images. In addition, a video camera for recording a moving image is provided with a still image recording function. When a still image is captured by these cameras, a so-called long-time exposure technique in which the exposure time is lengthened by lengthening the charge accumulation time in the image sensor is employed. With this long-time exposure technique, it is possible to take a picture even under low illuminance without using auxiliary lighting such as a strobe.

On the other hand, in the image pickup device, there is a dark output due to a so-called dark current or the like, and there is a problem that the dark output is superimposed on an image signal to deteriorate the image quality. The presence of a pixel having a high dark output level is called a pixel defect, and it is widely practiced to supplement the information using the output information of neighboring pixels without using the output information of the pixel. In this specification, such a complementing process is referred to as pixel defect compensation. As an example, a predetermined (N
In TSC, the dark output is evaluated at the standard exposure time of 1/60 second or 1/15 second when a predetermined margin is obtained based on the predetermined margin (based on the predetermined margin). Pixels having a large level are evaluated as defective pixels. There is an example in which the above-mentioned pixel defect compensation is applied.

Further, an image pickup device has been proposed which has been improved in that the evaluation of defective pixels is not sufficient just before shipment from the factory because pixel defects are accompanied by temperature dependence and changes with time (Japanese Patent Application Laid-Open No. HEI 9-163568). 6-38113). That is, this publication discloses that the light receiving surface is shielded from light by closing the iris immediately after the power is turned on, a defective pixel is detected by evaluating a CCD dark output prior to use of the camera, and information on the detected defective pixel is used. A technology for compensating for defects is described.

[0005]

However, in the digital camera as a completed product after shipment from the factory, when a defective pixel is detected every time the power is turned on and the defect is compensated as in the technique disclosed in the above-mentioned publication, This can be a disadvantage in operating the camera.

That is, in order to detect a defective pixel, an iris or a mechanical shutter is once operated to perform light shielding, and thereafter, an imaging operation (charge accumulation, transfer, signal reading) is performed, and this is obtained by data analysis. It is necessary to execute a sequence of writing defective pixel address data to the memory. Since this sequence requires a certain period of time (for example, several hundred ms to several s), the camera user is kept waiting during this time. For this reason, the camera user cannot understand why it takes a lot of time to enter the photographable (standby) state, which may cause confusion such as determining that the camera is out of order.

Further, even if the display function is devised to avoid misunderstanding, there is a high possibility that a photographing opportunity will be missed before photographing becomes possible. Needless to say, this problem is particularly serious in a still image camera which generally requires a high speed shooting.

On the other hand, the temperature characteristic of a pixel defect can be determined by using another known method such as incorporating a temperature sensor in the camera and storing defect data for each temperature when the camera is shipped. It is also possible to avoid such a method that requires a time lag. On the other hand, in order to apply the defect compensation to the aging deterioration of the pixel defect of the image sensor after the product is shipped, it is needless to say that the defect detection by the camera itself is inevitable.

However, it is not generally considered that such a time-dependent deterioration of a pixel defect increases rapidly in a short time. For example, one pixel is generated one day due to the influence of cosmic rays or natural radioactivity, and several weeks later. It occurs with a very low probability, such as the occurrence of one pixel. Of course, once a defect occurs, it is virtually impossible that it physically disappears, so even if it is at one pixel level, leaving it alone will cause the defect to be permanently manifested, and the effect is a failure Although it is large enough to be said to have the same meaning as, but at least if this can be recovered in the image recording of the camera at a short time, the probability of causing damage to the user that the defect becomes apparent becomes extremely small. . Further, even if a defect may become apparent, the defect is limited to one time, and the disadvantage is practically negligible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to eliminate the problem associated with the occurrence of a time lag caused by the detection of defective data for pixel defect compensation. It is an object of the present invention to provide a high-performance imaging apparatus which does not substantially cause image quality deterioration due to an increase in the number of target pixel defects.

[0011]

(Structure) In order to solve the above problem, the present invention employs the following structure.

That is, according to the present invention, in an image pickup apparatus, an image pickup device for picking up a subject image, a storage unit for registering a pixel defect address of the image pickup device as defect data, and the storage unit for an output of the image pickup device Defect compensation means for performing compensation processing based on neighboring pixel data based on the defect data registered in the image sensor, and analyzing the output of the image sensor obtained in a state where light incident on the image sensor is cut off, thereby analyzing the pixel defect address. Defect data detection means for newly detecting the defect data, and defect data management means for updating the defect data registered in the storage means based on the defect data newly detected by the defect data detection means. It is characterized by.

Here, preferred embodiments of the present invention include the following. (1) The defect data management means additionally registers, with respect to the registered defect data which has already been registered, a pixel defect address of newly detected defect data which is newly detected and which does not overlap with a pixel defect address of the registered defect data. Be configured to (2) The defect data management means, for the initially registered defect data registered at the time of factory shipment, a pixel defect address of newly detected defect data newly detected which does not overlap with a pixel defect address of the initially registered defect data. Must be configured to additionally register

(3) Clock means, and update time setting means for setting, based on the date and time data of the clock means, a data update time as a timing at which the update of defect data should be repeated at predetermined time intervals. Chronological data updating means for detecting and updating the defect data based on the updating time set by the updating time setting means.

(4) The chronological data updating means is configured to detect and update defective data in response to power-on after the data update time has arrived. (5) The chronological data updating means is configured to detect and update defective data in response to the arrival of the data updating time when the power is not turned on.

(Operation) According to the present invention, there is provided an image pickup apparatus having a storage unit for registering a pixel defect address as defect data and a defect compensation unit for performing a compensation process using neighboring pixel data based on the registered defect data. A pixel defect address is newly detected by analyzing an output of the image sensor obtained in a state in which light incident on the image sensor is blocked, and defect data registered in the storage unit is determined based on the newly detected defect data. By updating, the defect data registered in the storage means has a temporal pixel defect caused by the influence of cosmic rays and natural radioactivity in addition to the initial pixel defect at the time of factory shipment. Therefore, by performing the compensation process using the neighboring pixel data based on the defect data registered in the storage unit, it is possible to prevent the image quality from deteriorating due to an increase in pixel defects over time.

Further, by performing the additional registration at a low frequency by the clock function of the self, the detection operation becomes unnecessary at the time of normal photographing, so that no time lag occurs. Further, since the defect data is periodically updated, the defect is not left out, so that it is possible to effectively prevent the defect from appearing.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

(Embodiment) FIG. 1 is a block diagram showing a basic configuration of a digital camera according to an embodiment of the present invention.

In the figure, reference numeral 101 denotes a lens system including various lenses, and reference numeral 102 denotes a lens driving mechanism for driving the lens system 101. Reference numeral 103 denotes an exposure control mechanism for controlling the exposure, which includes an aperture and a drive mechanism for driving the aperture, and is provided for controlling the aperture by limiting the amount of incident light of light rays passing through the lens system 101. I have. Reference numeral 104 denotes a filter system having a filter for low-pass and infrared cut, and reference numeral 105 denotes a CCD color image sensor. Light rays that have passed through the exposure control mechanism 103 are guided to the image sensor 105 via the filter 104. Therefore, an image corresponding to the subject is formed on the image sensor 105.

107 is a gain control amplifier, A
A pre-processing circuit including a / D converter and the like. An imaging signal obtained by the imaging element 105 is input to the pre-processing circuit 107, and a digitized pixel signal is output from the pre-processing circuit 107. Reference numeral 108 denotes a digital process circuit for performing a color signal generation process, a matrix conversion process, and other various digital processes. The digital process circuit 108 generates color image data by processing the digitized image signal. Is done. 109 is a card interface connected to the digital process circuit 108, and 110 is a CF (Co)
mpact Flash Memory Card) or a memory card such as a smart media, and 111 is an LCD image display system. The memory card 110 stores color image data, and the LCD display system 111 displays color image data.

Further, in the figure, reference numeral 112 denotes a system controller (CPU) for overall control of each unit, 113 denotes an operation switch system comprising various SWs, and 114 denotes an operation display for displaying an operation state, a mode state, and the like. System, 115 is a lens driver for controlling the lens driving mechanism 102, 116 is a strobe as a light emitting means, 117 is an exposure control driver for controlling the exposure control mechanism 103 and the strobe 116, and 118 is various kinds of setting information and the like. 1 shows a non-volatile memory (EEPROM) for performing the operation. Here, the image defect data is stored in advance in the EEPROM 118 together with various setting information and the like.

In the digital camera of this embodiment, the system controller 112 performs overall control, and in particular, a shutter device included in the exposure control mechanism 103 and the CCD image pickup device 10 by the CCD driver 106.
5, the exposure (charge accumulation) and the signal readout are performed by controlling the driving of the pixel 5, and the detection of the pixel defect described below is performed using the output level information stored in the digital process 108 via the preprocess 107. Is what you do.

FIG. 2 is a block diagram functionally showing a configuration of a main part in the present embodiment. 201 is an EEPROM for storing defect data, 202 is a pixel defect compensating means, 2
03 is a defect data detection means, and 204 is a defect data management means. These are controlled by the digital process circuit 108 and the EEPROM under the control of the system controller 112.
This is realized by controlling M118.

The EEPROM 201 is the EEPROM 1
The EEPROM 201 stores address data relating to existing (latest at that time) defect data (hereinafter referred to as registered defect data). Initially (when the camera is shipped from the factory), defect data acquired in the manufacturing adjustment process is registered as a registered defect.

The defect compensating means 202 performs a complementing process for defective pixels by neighboring pixels.
02, an EEPROM is used for the input image data.
The registered defect data stored in 118 is read, and pixel defect compensation processing such as adjacent complementation is performed based on the defect data. In the defect data detection means 203, a pixel defect address is newly detected by analyzing the output of the image sensor obtained in a state where light incident on the image sensor is blocked. Then, the defect data management means 204 uses the EEPROM 201 based on the newly detected defect data.
The defect data registered in is updated.

Hereinafter, camera control by the system controller 112 will be described focusing on processing directly related to detection and compensation of pixel defects and management of defect detection timing in the present embodiment. However, in this camera, digital processing of the signal level is performed by 8 bits (0 to 255). Also, description will be made assuming normal temperature, except for the parts described later.

Prior to photographing, an exposure time required for photographing is set based on a manual setting or a photometric result. Next, the camera waits for a shooting trigger command for the main imaging, and upon receiving the command, performs exposure based on a predetermined exposure control value, reads out an imaging signal, performs predetermined signal processing, and then performs memory processing on the memory card 11.
Record at 0. At this time, the registered defective pixel is accompanied by pixel defect compensation. The video signal processing up to the recording after the defect compensation is appropriately used according to its necessity. The video signal processing is known per se, for example, a color balance processing, a conversion into a luminance-color difference signal by a matrix operation or a reverse conversion processing thereof, Examples include false color removal or reduction processing by band limitation, various nonlinear processing represented by gamma conversion, various information compression processing, and the like.

In this camera, the defect compensation employs the well-known "complementation of a pixel in which a defect address is registered with a neighboring pixel", and a specific complementing method is "a very close same-color pixel (of the same-color pixel). 4 closest to the defective pixel
Pixels: In the case of an RGB Bayer array, for example, four G pixels adjacent diagonally in four directions for G, and one G between R (or B) instead of directly adjacent in four directions of up, down, left, and right
Is used instead of the average value of the four pixel information corresponding to the four R (or B) pixels located next to each other.

The camera detects a defect when necessary, and additionally updates the registered defect based on the result. The defect detection is performed as follows. FIG. 3 shows a flowchart in this case.

First, the light receiving surface of the image sensor 105 is shielded from light by a shutter device included in the exposure control mechanism 103 (S
1) Test imaging is performed in the light-shielded state (S2). That is, the longest exposure time Tmax of the present camera is set by the CCD driver 106 in the dark (setting is arbitrary: the example value 5 s here).
Test charge signal (dark output signal)
Is read and stored in the digital process 108 (S
3). Each output level is checked for all the stored data of the effective output pixels, and a digital comparison with the reference level is performed to determine whether or not the data is defective (S4).

The criteria are as follows. That is, if the output level of the target pixel is P, the defect is determined when P> 5, and the defect is determined to be non-defect otherwise (P ≦ 5). This means that the dark output level at the time of main imaging is allowed up to about 2% of the maximum full range 255.

Here, the judgment reference level of about 2% is merely an example, and can be arbitrarily set at the time of design according to circumstances. If an appropriate value of the above level (for example, about 5% or about 1% is also effective) is selected, the possibility that the effect of the dark output superimposed on the image becomes apparent becomes sufficiently low. If this is selected to be 0%, it is possible to completely eliminate the pixel on which the dark output is superimposed. In this respect, this can be cited as a preferred embodiment. On the contrary, this means that the pixel information is completely discarded due to the superimposition of a slight dark signal, and therefore, the overall image quality may be reduced. In reality,
The reference level is set in consideration of these trade-off factors.

The specific steps after step S4 are as follows. First, after designating the first address (S5), it is determined whether or not P> 5 for this address (S6). If P> 5 is determined in step S6, it is determined that there is a pixel defect (S7), and the address of the detected pixel defect is temporarily stored (S8). Step S6
If it is determined that P ≧ 5, it is determined that there is no defect (S9). Then, it is determined in step S10 whether the address is the last address (S10). If the address is not the last address, the next address is specified (S11), and the process returns to step S6. If it is determined in step S10 that the address is the last address, the address of the temporarily stored pixel defect is stored in the EEPROM 201.
(S12).

When updating the defect data in the EEPROM 201, the address of the detected defective pixel, from which the duplicate of the registered defect is removed, is additionally registered. At this time,
The configuration may be such that the data of the detected defect is simply replaced with the existing registration data. However, in this case, if a detection error occurs due to some cause such as noise at the time of new detection, a pixel which was defective due to deterioration over time at the time of shipment from the factory is treated as a non-defect, and the defect becomes apparent. There is a possibility that it will be done. On the other hand, in the present embodiment, a defect obtained by removing the overlap with the existing registered defect from the detected defect is added to the existing data. Therefore, there is an effect that the once registered defect can be prevented from reappearing. are doing.

Updating of the data (detection of the defect and additional update of the registered defect) is performed based on the clock function of the camera. In this embodiment, the update time is set once a day at 2:00 midnight. When the update time comes, the data is updated when the power is turned on for the first time thereafter. At this time, in order not to confuse the user, for example, a display such as “Camera is being set up” is displayed in a suitable place,
It is preferable to display the information on an electronic viewfinder according to H.11. Thereafter, the data is not updated until the next update time comes, so that there is no time lag on the day. Further, since the data is not updated unless the power is turned on, useless power is not consumed.

(Modification) As a modification, a data update is performed when an update time comes when the power is not turned on. For example, when the update time comes at 2:00 midnight, once every three days, the power of the camera may be internally turned on and the data may be updated. In this case, the update is generally performed infrequently during the time when the camera is unlikely to be used, so that the possibility of affecting the user is extremely small, and the user is almost always used. Can be used without time lag. In this case, if there is a manual command to turn on the power during the data update, the update operation is immediately stopped, and the priority is given to the normal shooting function, so that the time lag can be completely eliminated. is there.

Further, in any of the above-mentioned examples, it is more preferable that the user can arbitrarily change the setting of the renewal time because the degree of freedom is increased. Furthermore, instead of setting the update timing at regular intervals, random irregular time intervals may be set, or time management using a clock may be performed. The renewal time can be set based on numerical information such as once every time. However, since the temporal change of the pixel defect is usually a stochastic phenomenon, the periodic time management as in the above embodiment is more preferable.

In addition, supplementing the quantization level of the A / D converter used in the embodiment,
If there is an error characteristic of the / D converter hardware, or even if it does not exist, the quantization error is relatively equivalent to 100% in principle near the minimum quantization level. Considering this, the A / D converter used for actual quantization in the above embodiment is larger than the number of quantization bits (8 bits in the embodiment) of the image processing system, for example, about 10 bits or 12 bits (more than that). It is more preferable to use the method of (1), which can sufficiently reduce the influence of errors in the calculation of each of the above arithmetic expressions.

Although several examples have been specifically described above as the embodiments and the modified examples of the present invention, the present invention is not limited to these and can take any form as long as it is described in the claims. Needless to say,

[0041]

As described above in detail, according to the present invention, in addition to the storage means for registering a pixel defect address as defect data and the defect compensation means for performing a compensation process using neighboring pixel data based on the registered defect data. A defect data detecting means for newly detecting a pixel defect address by analyzing an output of the image pickup element obtained in a state in which light incident on the image pickup element is blocked; and a storage means based on the newly detected defect data. By providing defect data management means for updating the defect data registered in the camera, the degree of freedom in the execution timing of defect detection becomes extremely high, and the time lag can be reduced by reducing the frequency of detection and performing detection when the camera is not used. It is possible to cope with the deterioration over time of the pixel defect without practically causing a problem such as increase in power consumption.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a digital camera according to an embodiment of the present invention.

FIG. 2 is a block diagram functionally showing a configuration of a main part in the embodiment.

FIG. 3 is a flowchart for explaining pixel defect detection and updating of a defect address.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Lens system 102 ... Lens drive mechanism 103 ... Exposure control mechanism 104 ... Mechanical shutter 105 ... CCD color image sensor 106 ... CCD driver 107 ... Preprocess circuit 108 ... Digital process circuit 109 ... Card interface 110 ... Memory card 111 ... LCD image display System 112 ... System controller (CPU) 113 ... Operation switch system 114 ... Operation display system 115 ... Lens driver 116 ... Strobe 117 ... Exposure control driver 118 ... Non-volatile memory (EEPROM) 201 ... EEPROM 202 ... Pixel defect compensation means 203 ... Defect Data detection means 204 ... Defect data management means

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideaki Yoshida 2-43-2 Hatagaya, Shibuya-ku, Tokyo F-term in Olympus Optical Industry Co., Ltd. 5C022 AA13 AB37 AB40 AC42 AC69 CA00 5C024 BX01 CX22 CX23 GY01 HX29 HX46 HX58

Claims (6)

[Claims] An image pickup device for picking up an image of a subject; storage means for registering a pixel defect address of the image pickup element as defect data; and an output of the image pickup element for storing defect data registered in the storage means. Defect compensation means for performing compensation processing based on neighboring pixel data based on the pixel data; and defect data for newly detecting the pixel defect address by analyzing an output of the image sensor obtained in a state where light incident on the image sensor is blocked. An imaging apparatus comprising: a detection unit; and a defect data management unit that updates defect data registered in the storage unit based on defect data newly detected by the defect data detection unit. 2. The method according to claim 1, wherein the defect data management means is configured to determine, for the registered defect data that has already been registered, a pixel defect address of newly detected defect data that does not overlap with a pixel defect address of the registered defect data. The imaging apparatus according to claim 1, wherein the imaging apparatus is configured to additionally register. 3. The defect data management means according to claim 1, further comprising, for the initially registered defect data registered at the time of shipment from the factory, the pixel defect address of the initially registered defect data among the pixel defect addresses of newly detected defect data newly detected. 2. The imaging apparatus according to claim 1, wherein the apparatus is configured to additionally register non-overlapping ones. 4. Clock means, and update time setting means for setting a data update time as a timing at which the update of the defect data should be repeated at predetermined time intervals based on the date and time data of the clock means. 4. A chronological data updating means for detecting and updating the defect data based on the updating time set by the updating time setting means. Imaging device. 5. The apparatus according to claim 4, wherein said chronological data updating means is configured to detect and update defective data in response to power-on after the data update time has arrived. An imaging device according to any one of the preceding claims. 6. The chronological data updating means is configured to detect and update defect data in response to the arrival of the data update time when the power is not turned on. The imaging device according to claim 4.