JP2002281390A - Imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an imaging system with high performance not to generate degradation of image quality due to the increase of defects of pixels over aging by preventing erroneous detection due to reverse incident light through the finder. SOLUTION: A system controller 112 is provided with a defect data detecting part 112a to detect pixel defect data by analyzing a signal from a CCD 105 to be obtained at a light shielding state by a digital process 118, a defect compensation control part 112b to perform a pixel defect compensation processing to the signal to be obtained from the CCD 105 at main photographing and an eyepiece shutter control part 112c to drive an eyepiece shutter and to set it at a closed position when the eyepiece shutter is opened at the detection of the pixel defect data. The system controller 112 confirms an opening/closing state of the eyepiece shutter prior to the defect detection and when the eyepiece shutter is opened, starts the defect detection after performing driving to close it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus, and more particularly to an image pickup apparatus having a pixel defect compensation function.

[0002]

2. Description of the Related Art Imaging devices such as video cameras have been widely used. In recent years, electronic still cameras that mainly capture and record still images have also come into widespread use especially as digital cameras, and video movies mainly for recording moving images also have a still image capturing and recording function. Long-time exposure, which is mainly used for shooting still images, increases the exposure time by increasing the charge accumulation time in the image sensor, thereby enabling shooting without using auxiliary lighting such as a strobe even under low illumination. It is known as a technology.

On the other hand, an image pickup device such as a CCD has a dark output due to the presence of a so-called dark current, which is superimposed on an image signal, thereby deteriorating the image quality. If there is a pixel with a large dark output level, it is called a pixel defect,
It is widely practiced to supplement information using output information of neighboring pixels without using output information of the pixel. In the present specification, such a complementing process is referred to as pixel defect compensation. A predetermined (often 1/60 in NTSC) which is often determined on the premise of driving a moving image at the used frame rate
The dark output is evaluated at a standard exposure time of seconds or a predetermined margin based on the predetermined margin (for example, 1/15 second when the margin is 4 times), and a pixel having a large level is regarded as a defective pixel. Apply the pixel defect compensation.

Further, Japanese Patent Application Laid-Open No. 06-038113 discloses a technique for improving that a pixel defect involves temperature dependence and aging, so that it is not sufficient to evaluate a defective pixel just before shipment from a factory. It is known. That is, in this publication, the light receiving surface is shielded by closing the iris immediately after the power is turned on, and the CCD is used before the camera is used.
A technique for detecting a defective pixel by evaluating a dark output and performing defect compensation is described.

[0005]

However, even when the technique of acquiring defective pixel information by using the output of the image sensor under light-shielding by closing the iris is used, even if the technique of acquiring defective pixel information is used.
In a digital camera having an eye-reflection optical viewfinder, extra light may be input to the CCD due to reverse incident light from the optical viewfinder, resulting in erroneous detection.

In particular, since the degree of back-incident light from the optical finder varies depending on the environment around the camera at that time, a digital camera that automatically detects defective pixels differs from the actual degree of defect every time a defect is detected. An erroneous detection result is obtained, and the result is accumulated.

The present invention has been made in consideration of the above circumstances, and has as its object to prevent erroneous detection due to back-incident light from a finder and prevent image quality deterioration due to an increase in pixel defects with time. It is to provide a high-performance imaging device.

[0008]

In order to solve the above-mentioned problems, an image pickup apparatus according to the present invention comprises: an image pickup device; an image pickup optical system for inputting a subject image to the image pickup device; Optical finder means for observing a subject image; reverse incident light blocking means for blocking light from the optical finder means to the image sensor; and detection of pixel defect data by analyzing the output of the image sensor. And a defect correction means for correcting the output of the image sensor based on the pixel defect data detected by the defect data detection means, and detecting the defect data by the defect data detection means. If the back-incident light blocking means is open when performing the operation, the back-incident light blocking means is driven and closed, and then the defect data is detected. Characterized by comprising a control means.

In this imaging apparatus, there is provided a reverse incident light blocking means for blocking light from entering from the optical finder means to the image pickup device, and when detecting the defect data, the reverse incident light blocking means is open. Then, after the reverse incident light blocking means is driven and closed, defect data is detected. In this way, by adopting a configuration in which the back-incident light blocking means is closed by closing drive to detect the defect data, it is possible to prevent erroneous detection due to the back-incident light from the optical finder means. Therefore, correct defect detection can be automatically performed regardless of the surrounding environment.

Further, the present invention further comprises imaging light shielding means for blocking incident light from the imaging optical system to the image pickup device, and the defect data detecting means is provided by the imaging optical system by the imaging light shielding means. A dark output information analyzing means for analyzing an output of the image sensor obtained in this state while blocking incident light to the image sensor is included. As described above, when the dark output information of the image sensor is obtained, the back-incident light blocking unit is closed, and the defect data is detected in a state where the incident light to the image sensor is blocked, so that a so-called white defect pixel is detected. Can be checked with high accuracy.

As the defect correction, it is possible to use a defect compensation in which a pixel registered as a pixel defect address is complemented with information on neighboring non-registered pixels. In this case, in particular, the pixel defect address information stored in the storage unit is updated based on the pixel defect data newly detected by the storage unit that stores the pixel defect address information relating to the image sensor, and the pixel defect data newly detected by the defect data detection unit. It is desirable to further provide defect data management means. As a result, it is possible to cope with an increase in pixel defects over time, and it is possible to prevent image quality deterioration.

Whether the back-incident light blocking means is open or closed can be determined by an internal flag or the like of the control means. Preferably, means is further provided, and an actual setting state of the reverse incident light blocking means is determined based on a detection result by the setting state detecting means. In particular, when it is recognized based on the detection result by the setting state detecting means that the reverse incident light blocking means is not closed despite the execution of the closing drive of the reverse incident light blocking means, the defect data is detected by the defect data detecting means. By prohibiting the detection of abnormalities, and by issuing a warning and recording this as abnormal history information, even if the closing drive was not performed normally due to a drive system failure, etc. Generation can be eliminated, and reliability can be improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a digital camera according to an embodiment of the present invention.

In FIG. 1, reference numeral 101 denotes an imaging lens system including various lenses; 102, a lens driving mechanism for driving the lens system 101; 103, an exposure control mechanism for controlling the aperture and shutter device of the lens system 101; A low-pass and infrared cut filter; 105, a CCD color image sensor for photoelectrically converting a subject image; 106, a CCD driver for driving the image sensor 105;
A pre-processing circuit including a / D converter, etc .; 108, a digital processing circuit for performing various digital arithmetic processing such as gamma conversion; 109, a card interface; 110, a memory card; 111, an LCD image display system; Is shown. Reference numeral 112 in the figure denotes a system controller (CPU) for comprehensively controlling each unit,
Reference numeral 13 denotes an operation switch system including various SWs; 114, an operation display system for displaying an operation state, a mode state, and the like;
Reference numeral 15 denotes a lens driver for controlling the lens driving mechanism 102, 116 denotes a strobe as a light emitting unit, 117 denotes an exposure control driver for controlling the exposure control mechanism 103 and the strobe 116, and 118 denotes various setting information and the like. 1 shows a nonvolatile memory (EEPROM).

The camera of this embodiment has a known single-lens reflex optical viewfinder. However, the optical path branching to the optical finder is performed by a half mirror (prism).
FIG. 2 shows the structure around the optical finder.

When the mechanical shutter 103a provided as an iris in the exposure control mechanism 103 is open,
The subject image input from the lens system 101 is input to the imaging surface of the CCD 105 through the half mirror (prism) 201 and is branched by the half mirror (prism) 201. The aerial images branched by the prism 201 and formed on the primary image forming surface (dotted line between the prism 201 and the plane mirror 203) are formed on the plane mirrors 203 and 2.
Relay by the secondary imaging lens 204, the secondary imaging lens 204
The re-formed aerial image is magnified and observed by the loupe lens 204. It is also possible to arrange a screen on either the primary or secondary imaging plane so that focus can be confirmed.

Loupe lens 2 at the opening of the optical finder
Inside eyepiece 06, an eyepiece shutter 205 for blocking reverse incident light from the optical finder is provided. The eyepiece shutter 205 is electrically driven, and is driven and controlled by a drive signal from the system controller 112 to a closed position for blocking back incident light from an opening of the optical finder or an open position for releasing. As shown in FIG. 3, the eyepiece shutter 205 includes a light-shielding plate 205a made of a matte black painted resin plate.
A gear 205b is provided on the rotation shaft to which the light shielding plate 205a is attached. The gear 205b is a motor 205 as a driving mechanism of the eyepiece shutter 205.
The gear 205d is engaged with the gear 205d, and the light shielding plate 205a rotates between the closed position and the open position by driving the motor 205c.

The position of the eyepiece shutter 205, that is, the position of the light shielding plate 205a, can be detected by a sensor 207 composed of a photo interrupter or the like. , The eyepiece shutter 205 is opened and closed.

The sensor 207 is provided so that it can be reliably determined whether the eyepiece shutter 205 has actually been driven to the closed position and the open position. By using the detection signal from the sensor 207, even if any operation error occurs in the electric drive mechanism of the eyepiece shutter 205, whether the current position of the eyepiece shutter 205 is the closed position or the open position is determined. It can be correctly determined.

Of course, it is also possible to use control such that the eyepiece shutter 205 is regarded as being set to the closed position or the open position by energizing the motor for a predetermined time or longer without using a detecting means such as the sensor 207. it can. In this case, the current setting state of the eyepiece shutter 205 (whether it is the closed position or the open position) may be managed by an internal flag of the system controller 112.

Instead of controlling the motor energizing time as described above, another actuator such as a solenoid or a stepping motor may be used. Also in this case, the current setting state of the eyepiece shutter 205 can be managed by an internal flag of the system controller 112.
It is possible to correctly determine whether the current position 05 is the closed position or the open position.

In the camera of the present embodiment, the system controller 112 performs overall control, and controls the exposure control mechanism 103 and the CCD driver 106 to drive the CCD image pickup device 105 for exposure (charge accumulation). And read out the signal, A / D convert the signal through the pre-processing circuit 107, take it into the digital process circuit 108, perform various signal processing in the digital process circuit 108, and then perform the card interface 1
09 to the memory card 110.

The system controller 112 includes:
As shown in the figure, a defect data detection unit 112a for detecting pixel defect data by analyzing a signal from the CCD 105 obtained in a light-shielded state by a digital process circuit 108, and a signal obtained from the CCD 105 at the time of actual imaging. A defect correction control unit 112b for performing pixel defect compensation processing, and an eyepiece shutter control unit for driving the eyepiece shutter 205 to set it to the closed position when the eyepiece shutter 205 is open when pixel defect data is detected. 112c.

The pixel defect compensation processing is performed by the defect correction control unit 11
Based on the instruction from 2b, the process is executed in the digital process circuit 108 based on the address data of the defective pixel stored in the EEPROM 118 regarding the existing (latest) defect (hereinafter referred to as a registered defect). In the initial stage (when the camera is shipped from the factory), defect data acquired in the manufacturing adjustment process is registered as a registered defect.

Hereinafter, camera control by the system controller 112 will be described focusing on processing directly related to detection and compensation of pixel defects according to the present invention. However, in this camera, the digital processing of the signal level obtained from the CCD 105 is performed with 8 bits (0 to 255). Except for the parts specially described later, the description will be made assuming normal temperature.

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.
After the image signal is read out from the memory card and subjected to predetermined signal processing, it is recorded on the memory card 110. At this time, the registered defective pixel is accompanied by pixel defect compensation. After the defect compensation, the video signal processing up to the recording is appropriately used according to its necessity. It is known per se, for example, color balance processing, conversion into a luminance-color difference signal by matrix operation or its inverse conversion processing, Examples include false color removal or reduction processing by band limitation, various nonlinear processing represented by γ conversion, various information compression processing, and the like.

The defect compensation in the camera of this embodiment employs the well-known "complementation of a pixel in which a defect address is registered with a neighboring pixel". Among them, the four pixels closest to the defective pixel: In the case of an RGB Bayer array, for example, four G pixels adjacent to each other diagonally in four directions for G, and four pixels directly adjacent to R (or B) in four directions, up, down, left, and right. Four R (or B) located next to each other with one G in between
Pixel), the average value of four pixel information is substituted.

The camera detects a defect when necessary, and additionally updates the registered defect based on the result. Hereinafter, the defect detection operation will be described with reference to the flowchart of FIG.

First, prior to defect detection, the system controller 112 checks the open / closed state of the eyepiece shutter 205 and determines whether the eyepiece shutter 205 is closed (steps S101 and S102). It is most preferable to check the opening / closing state using the detection signal from the sensor 207, but in principle, it may be determined only by the internal flag.

When the eyepiece shutter 205 is in the closed state, the process directly proceeds to the following defect detection processing. When the eyepiece shutter 205 is in the open state, the system controller 112 controls the motor 205c.
Is driven to close the eyepiece shutter 205 (step S103), and it is determined whether or not the detection signal from the sensor 207 indicates the closed position (step S10).
4). At this time, if the detection signal from the sensor 207 does not indicate the closing position, that is, if the closing of the eyepiece shutter 205 is not confirmed despite the execution of the closing drive (NO in step S104), the driving system May cause the eyepiece shutter 205 to remain open. If the defect detection is performed in such a situation, there is a high possibility of erroneous detection. Therefore, in such a case, the defect detection (and the update of the defect address data of the EEPROM 118) is not executed (prohibited). This is a highly desirable configuration. Further, in such a case, a warning is given to the user by displaying a message indicating the occurrence of an abnormality or a buzzer sound to alert the user (step S109), and at the same time, the state of the occurrence of the abnormality is recorded in the EEPROM 118 and the repair service is performed. (Step S110) is a more desirable configuration.

The defect detection is performed as follows.

That is, the system controller 112
After the eyepiece shutter 205 is closed, the light receiving surface of the image sensor is shielded by the shutter device 103a included in the exposure control mechanism 103, and then test imaging is performed in the shielded state (steps S105 and S106). That is, the longest exposure time Tmax of the camera is set by the CCD driver 106 in the dark (the setting is arbitrary: the example value 5 s here)
To read out a test image pickup signal (dark output signal) and store it in the digital process 108. Then, the dark output signal is analyzed by the digital process 108, each output level is checked for all the data of the effective output pixels, and a digital comparison is made with the reference level to determine whether or not the data is defective (step S107).

The criterion is as follows. That is, if the output level of the pixel of interest is S, the defect is determined when s> 5, and the defect is determined to be non-defect when the output level is other than (s ≦ 5).

This means that the dark output level at the time of actual 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 according to the circumstances at the time of design. However, an appropriate value (about 5% or about 1 % Is also effective), the possibility that the effect of the dark output superimposed on the image becomes obvious 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 also be cited as one preferred embodiment. This means that the pixel information is completely discarded due to the superposition of, so that the overall image quality may be reduced. In reality, the reference level is set in consideration of these trade-off factors.

A pixel defect obtained by such a camera defect detection is called a detection defect.

Next, from the addresses of the detected defective pixels obtained as described above, those obtained by removing duplicate addresses of the registered defects already registered in the EEPROM 118 are obtained.
Additional registration is made in the EEPROM 118 (step S10).
8). At this time, the configuration may be such that the data of the detected defect is simply replaced with the existing registered data. However, in this case, if a detection error occurs for some reason such as noise at the time of new detection, pixels that were defective due to deterioration over time at the time of shipment from the factory are treated as non-defects, and defects are revealed. There is a possibility that it will be done. On the other hand, in the above-described embodiment, a defect obtained by removing the overlap with the existing registered defect from the detected defect is added to the existing data. ing.

The update of the data (the above-described defect detection and the additional update of the registered defect) is performed at an arbitrary necessary time, for example, every time the power of the camera imaging unit is turned on.

In this regard, some specific modifications will be described.
In the first example, the data is updated based on the clock function of the camera. In this example, 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. In this case, it is preferable to display a message such as "Camera is being set up" in an appropriate place, for example, on an electronic viewfinder using an LCD in order not to disturb the user. Thereafter, the data is not updated until the next update time comes, so there is no time lag for one day on that day. Since the data is not updated unless the power is turned on, there is no waste of power.

As a second modified example, there is one in which data is updated when an update time comes when the power is not turned on. For example, when the update time comes at 2 o'clock at midnight, once every three days, the camera may be turned on internally to update the data. In this case, updates are performed infrequently during times when the camera is unlikely to be used, so it is very unlikely that the user will be affected, and the user will have a time lag in almost any case. Can be used without. In this case, if a manual command to turn on the power is issued during the data update, the update operation is immediately stopped and the normal shooting function is prioritized, so that the time lag can be completely eliminated. It is possible.

Further, in any of the above-mentioned examples, it is more preferable that the user can arbitrarily change the setting of the renewal timing because the flexibility is increased. Also, instead of setting the update time every fixed cycle, a random time interval may be set at random, and the time may not be managed by a clock. For example, once every number of power-on times or once every number of shots It is also possible to set the update time with numerical information such as one 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.

Incidentally, if supplementary information is given regarding the quantization level of the AD converter used in the above embodiment, in reality,
Considering the existence of the error characteristic of the hardware of the AD converter and the fact that even if it does not exist, in principle, the quantization error near the minimum quantization level is relatively equivalent to 100%, An AD converter used for actual quantization in the embodiment is, for example, 10 which is larger than the quantization bit number (8 bits in the embodiment) of the image processing system.
It is more preferable to use bits or about 12 bits (or more), so that the effects of errors can be sufficiently reduced in the various calculations.

Although the defect detection in the above-described embodiment is intended only for a so-called white defect, for example, even when a black defect is detected by inputting white light to the image pickup surface by some method, the light input is not detected. Depending on the method, the influence of the back incident light from the finder may become a problem. It goes without saying that the present invention is just as suitable in such a case.

Further, the defect detection and correction in the above embodiment is an address registration and a complementation (applying data substitution) by neighboring pixel information performed based on the address registration.
The present invention is not limited to this. For example, an arithmetic-type pixel defect correction (analog defect detection and acquisition) in which, for example, a dark output level is obtained in a light-shielded state and the dark output level is subtracted from an image signal during main imaging. It is obvious that the present invention can be applied to data correction, and it is just as effective in eliminating the adverse effect of the back incident light.

In the above embodiment, a digital still camera has been described as an example, but the present invention can be similarly applied to a digital movie.

The above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effects described in the column of the effect of the invention can be solved. Is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.

[0046]

As described above, according to the present invention,
It is possible to realize a high-performance imaging device that does not cause erroneous detection due to reverse incident light from the finder and does not cause deterioration in image quality due to an increase in pixel defects over time.

[Brief description of the drawings]

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

FIG. 2 is an exemplary view for explaining an eyepiece shutter provided in the electronic camera of the embodiment.

FIG. 3 is an exemplary view for explaining a configuration of an eyepiece shutter provided in the electronic camera of the embodiment.

FIG. 4 is an exemplary flowchart for explaining a defect detection operation in the electronic camera of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Lens system 102 ... Lens drive mechanism 103 ... Exposure control mechanism 104 ... Filter system 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) 112a: Defect data detection unit 112b: Defect correction control unit 112c: Eyepiece shutter control unit 115: Eyepiece shutter

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // H04N 101: 00 H04N 101: 00 (72) Inventor Hideaki Yoshida 2-43-2 Hatagaya, Shibuya-ku, Tokyo No. Olympus Optical Co., Ltd. F term (reference) 5C022 AA13 AC02 AC03 AC08 AC09 AC18 AC51 AC69 AC74 CA00 5C024 BX01 CX22 CX23 CX24 GY01 HX29 HX58 HX60 5C052 AA17 AB03 CC01 DD02 DD08 GA02 GA03 GB09 GC08

Claims (8)

[Claims] 1. An imaging device, an imaging optical system for inputting a subject image to the imaging device, an optical finder for observing the subject image input by the imaging optical system, and Reverse incident light blocking means for blocking light from entering the image sensor, defect data detecting means for detecting pixel defect data by analyzing the output of the image sensor, and pixels detected by the defect data detecting means A defect correction unit for correcting the output of the image sensor based on the defect data; and the reverse incident light blocking unit is open when the defect data detection unit detects the defect data. An imaging apparatus comprising: a control unit that drives the incident light blocking unit, closes the driving unit, and executes detection of defect data. 2. The imaging optical system further includes an imaging light shielding unit that blocks incident light from the imaging optical system to the imaging device, wherein the defect data detection unit transmits the defect data to the imaging device by the imaging optical system by the imaging optical system. 2. The imaging apparatus according to claim 1, further comprising a dark output information analysis unit that analyzes an output of the imaging device obtained in this state while blocking incident light. 3. The pixel defect data is pixel defect address information indicating a pixel defect address, and the defect correction unit complements a pixel registered as the pixel defect address with neighboring unregistered pixel information. The imaging device according to claim 1, further comprising a defect compensation unit. 4. A storage means for storing pixel defect address information on the image sensor, and pixel defect address information stored in the storage means based on pixel defect data newly detected by the defect data detection means. 4. The image pickup apparatus according to claim 3, further comprising: a defect data management unit that updates the data. 5. The apparatus according to claim 1, further comprising a setting state detecting unit configured to detect a setting state of the reverse incident light blocking unit, wherein the control unit opens the reverse incident light blocking unit based on a detection result by the setting state detecting unit. The imaging apparatus according to any one of claims 1 to 4, wherein the imaging apparatus is configured to determine a closed setting state. 6. When the control means recognizes that the reverse incident light blocking means does not close based on the detection result by the setting state detecting means, despite the execution of the closing drive of the reverse incident light blocking means. 6. The imaging apparatus according to claim 5, wherein the apparatus is configured to prohibit detection of defect data by the defect data detecting means. 7. When the control means recognizes that the reverse incident light blocking means is not closed in spite of execution of the closing drive of the reverse incident light blocking means based on a detection result by the setting state detecting means. 7. The imaging apparatus according to claim 6, wherein the apparatus is configured to issue a warning. 8. When the control unit recognizes that the reverse incident light blocking unit is not closed despite execution of the closing drive of the reverse incident light blocking unit based on the detection result by the setting state detecting unit. And means for recording the information as abnormality history information.
An imaging device according to any one of the preceding claims.