JP2004364050A - Defective pixel correction method for solid-state imaging device, and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a defective pixel of the solid-state imaging device in a short period of time without the need for using a temperature sensor. <P>SOLUTION: When a power button 21 is operated to apply power to a digital camera 2, a CPU 33 of the digital camera 2 drives a lens motor 31 to adjust a focus of an imaging lens 11 relative to a scale 12, compares the focal position with a focal position of the imaging lens 11 with respect to the scale 12 at a temperature stored in an EEPROM 49 and calculates the ambient temperature of the imaging lens 11 on the basis of the result of comparison. The CPU 33 detects a position of a defective pixel on the basis of the calculated ambient temperature and a relation between the ambient temperature stored in the EEPROM 49 and the position of the defective pixel of a CCD 36. An image signal processing circuit 45 interpolates image data of the pixel detected by the CPU 33 by using image data of pixels around the detected pixel or a preset predetermined value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for correcting defective pixels of a solid-state imaging device, and an imaging apparatus.
[0002]
[Prior art]
As an imaging device, a digital camera that converts a subject image captured by a solid-state imaging device such as a CCD image sensor (CCD) into digital image data and stores the digital image data in a storage medium such as a built-in memory or a memory card is widely used. In recent digital cameras, in order to reduce the cost of the product, a low-priced plastic lens with excellent processability is used as an imaging lens for capturing subject light into the CCD.
[0003]
The plastic lens has an advantage in cost performance, but has a disadvantage that the in-focus position shifts due to a change in ambient temperature because of a high coefficient of thermal expansion. In order to solve this problem, there has been proposed an imaging apparatus that detects the temperature of a lens barrel that holds an imaging lens or the temperature of a CCD wiring board using a temperature sensor and corrects the deviation of the in-focus position based on the detection result. (See Patent Documents 1 and 2).
[0004]
On the other hand, as with the shift of the in-focus position, as a problem depending on temperature, there is a white spot image defect of CCD, which is a cause of remarkably degrading the image quality of the digital camera, so-called white scratch. To solve this problem, the temperature of the solid-state imaging device is detected by a temperature sensor, and a defective pixel detection circuit that varies a threshold value when detecting a defective pixel according to temperature information from the temperature sensor (see Patent Document 3). ), Or by closing the iris to shield the light receiving surface of the solid-state image sensor, and increasing the gain of an AGC (auto gain control) circuit that amplifies the image data output from the solid-state image sensor to detect defective pixels. A video camera (see Patent Document 4) that stores position information has been proposed.
[0005]
[Patent Document 1]
JP-A-8-114736 [Patent Document 2]
JP-A-9-304678 [Patent Document 3]
JP-A-5-268527 [Patent Document 4]
Japanese Patent Laid-Open No. 6-350926 [0006]
[Problems to be solved by the invention]
However, since the devices described in Patent Documents 1 to 4 use a temperature sensor, they are contrary to the trend of downsizing and cost reduction of products that are intensifying in recent years.
[0007]
An object of the present invention is to provide a method for correcting a defective pixel of a solid-state imaging device and an imaging apparatus that can detect defective pixels of the solid-state imaging device in a short time without using a temperature sensor.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 is directed to a method of correcting a defective pixel of a solid-state imaging device that images subject light captured from an imaging lens and outputs image data. The peripheral temperature of the imaging lens is calculated from the step of adjusting the focus of the imaging lens with respect to the image, and the comparison result of the in-focus position at that time and the in-focus position of the imaging lens with respect to a specific subject at a pre-stored temperature. A step of calculating, and a step of detecting the position of the pixel where the defective pixel is generated based on the calculated ambient temperature and the relationship between the pre-stored ambient temperature and the position of the pixel of the solid-state imaging device where the defective pixel is generated; A step of interpolating the image data of the detected pixel with the image data of the surrounding pixels or a predetermined value.
[0009]
The invention described in claim 2 includes an imaging lens that captures subject light, a focus adjustment unit that performs focus adjustment of the imaging lens, and a solid-state imaging device that captures the subject light and outputs image data. In the imaging apparatus, a storage unit that stores a focus position of the imaging lens with respect to a specific subject at a certain temperature, and a relationship between a peripheral temperature of the imaging lens and a pixel position of a solid-state imaging device in which a defective pixel is generated, The focus adjustment unit is driven to adjust the focus of the imaging lens with respect to a specific subject. From the comparison result between the focus position at that time and the focus position stored in the storage unit, the imaging lens From the temperature calculation means for calculating the ambient temperature, the calculated ambient temperature, and the relationship between the ambient temperature stored in the storage means and the position of the pixel, the defective pixel And defective pixel position detecting means for detecting the position of the pixel for generating the image data of the detected pixels, characterized by comprising a pixel interpolating means for interpolating the image data or a predetermined value, the peripheral pixels thereof. In addition, when the lens barrier which covers the front surface of the said imaging lens is provided, it is preferable to provide the scale for a focus adjustment in the surface facing the imaging lens of the said lens barrier as said specific subject.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2, a lens barrier 10 that can be slid in the direction of an arrow is provided on the front of a digital camera 2 to which the present invention is applied. A focus adjustment scale 12 is provided on a portion of the rear surface of the lens barrier 10 facing the imaging lens 11. In the digital camera 2, by sliding the lens barrier 10 to the open position shown in FIG. 1, the lens barrel 13 holding the imaging lens 11 is extended to the front, and the strobe light emitting unit 14 is exposed to be in a state where photographing is possible. . The imaging lens 11 is a plastic lens that is inexpensive and has excellent workability.
[0011]
A CCD 36 (see FIG. 3) is disposed behind the imaging lens 11. The imaging signal from the CCD 36 is converted into digital image data by an A / D converter 40 (see FIG. 3). This image data is displayed as a so-called through image on a liquid crystal display (LCD) 15 provided on the back of the digital camera 2. Further, the digital camera 2 is provided with a finder objective window 16 and a finder eyepiece window 17 that constitute an optical finder, through which a subject image is framed.
[0012]
A release button 18 is provided on the upper surface of the digital camera 2. The release button 18 is a two-step push switch. When the release button 18 is lightly pressed (half-pressed) after framing by the LCD 15 or the optical viewfinder, automatic exposure adjustment (AE), automatic focus adjustment (AF), etc. Various shooting preparation processes are performed.
[0013]
The image pickup signal subjected to the image pickup preparation process is data-locked until the release button 18 is released. In this state, when the release button 18 is pressed once more (fully pressed), the imaging signal for one screen subjected to the imaging preparation process is converted into image data, and then is detachably attached to the memory card slot 19. The data is stored in a storage medium such as the memory card 20 or the SDRAM 44 (see FIG. 3) to be loaded.
[0014]
On the back of the digital camera 2, in addition to the LCD 15, a power button 21 for switching on / off the power, a zoom operation button 22 for changing the zoom lens of the imaging lens 11 to the wide side and the tele side, and various modes are selected. An operation unit 25 (a portion surrounded by a one-dot chain line) including a mode changeover switch 23 and a cursor operation plate 24 for moving a cursor in a menu screen displayed on the LCD 15 is provided.
[0015]
The digital camera 2 can select a still image shooting mode for shooting still images, a moving image shooting mode for shooting movies, a playback mode for displaying captured images on the LCD 15, a setup mode for performing various settings, and the like. These modes are switched by sliding the mode switch 23.
[0016]
In FIG. 3 showing the electrical configuration of the digital camera 2, a lens motor 31 and an iris motor 32 are connected to the imaging lens 11 and the diaphragm 30. These motors 31 and 32 are driven and controlled via motor drivers 34 and 35 connected to the CPU 33, and perform shooting preparation processing by half-pressing the release button 18.
[0017]
The lens motor 31 operates the zoom lens of the imaging lens 11 to the wide side or the tele side in conjunction with the operation of the zoom operation button 22 to perform zooming of the imaging lens 11. Further, the focus lens is operated to adjust the focus of the imaging lens 11 so that the photographing conditions are optimized. The iris motor 32 operates the diaphragm 30 to adjust the exposure of the imaging lens 11.
[0018]
Behind the imaging lens 11, a CCD 36 that images subject light transmitted through the imaging lens 11 is arranged. A timing generator (TG) 37 controlled by the CPU 33 is connected to the CCD 36, and the shutter speed of the electronic shutter is determined by a timing signal (clock pulse) input from the TG 37.
[0019]
The imaging signal output from the CCD 36 is input to a correlated double sampling circuit (CDS) 38, and is output as R, G, B image data that accurately corresponds to the accumulated charge amount of each cell of the CCD 36. The image data output from the CDS 38 is amplified by an amplifier (AMP) 39 and converted into digital data by an A / D converter (A / D) 40.
[0020]
The image input controller 41 is connected to the CPU 33 via the bus 42 and controls the CCD 36, CDS 38, AMP 39, and A / D converter 40 in accordance with a control command from the CPU 33. The image data output from the A / D converter 40 is displayed on the LCD 15 via the LCD driver 43. Alternatively, it is displayed on the optical viewfinder via an optical viewfinder driver (not shown). Alternatively, it is stored in the SDRAM 44.
[0021]
The image signal processing circuit 45 performs various types of image processing such as gradation conversion, white balance correction, and γ correction processing on the image data. Image data that has been subjected to various processes in the image signal processing circuit 45 is converted into a luminance signal Y and color difference signals Cr and Cb by a YC conversion processing circuit 46. The compression / decompression processing circuit 47 performs image compression on the converted image data in a predetermined compression format (for example, JPEG format). The compressed image data is recorded on the memory card 20 via the media controller 48.
[0022]
In addition to the release button 18 and the operation unit 25 described above, an EEPROM 49 is connected to the CPU 33. The EEPROM 49 stores various control programs and setting information. The CPU 33 reads these pieces of information from the EEPROM 49 to the SDRAM 44, which is a working memory, and executes various processes.
[0023]
The bus 42 includes an AE detection circuit 50 that detects whether the exposure amount, that is, the shutter speed of the electronic shutter of the CCD 36 and the aperture value of the aperture 30 are appropriate for imaging, and whether the white balance correction is appropriate for imaging. An AWB detection circuit 51 for detection and a strobe control circuit 53 for controlling the operation of the strobe device 52 are connected. The detection circuits 50 and 51 sequentially transmit detection results to the CPU 33 via the bus 42 when the release button 18 is half-pressed. The CPU 33 controls the operations of the imaging lens 11, the diaphragm 30, and the CCD 36 based on the detection results transmitted from the detection circuits 50 and 51.
[0024]
As the flash mode of the strobe device 52, for example, an automatic flash mode that automatically flashes when the subject brightness is low, a forced flash mode that flashes regardless of the subject brightness, or a flash prohibit mode that prohibits strobe flash can be selected. It has become.
[0025]
The EEPROM 49 stores the in-focus position of the imaging lens 11 with respect to the scale 12 of the lens barrier 10 at a certain temperature, and the relationship between the ambient temperature of the imaging lens 11 and the position of the pixel of the CCD 36 where the defective pixel is generated. When the power button 21 is operated and the power of the digital camera 2 is turned on, the CPU 33 drives the lens motor 31 to cause the scale 12 to adjust the focus of the imaging lens 11. Then, the in-focus position at that time is compared with the in-focus position stored in the EEPROM 49, and the ambient temperature of the imaging lens 11 is calculated from the comparison result.
[0026]
The CPU 33 detects the position of the pixel where the defective pixel is generated from the relationship between the calculated ambient temperature and the ambient temperature stored in the EEPROM 49 and the position of the pixel of the CCD 36 where the defective pixel is generated. The image signal processing circuit 45 interpolates the image data of the pixels detected by the CPU 33 with the image data of the peripheral pixels or a predetermined value set in advance.
[0027]
Next, the effect | action by the said embodiment is demonstrated with reference to the flowchart of FIG. First, the power button 21 is operated to turn on the power of the digital camera 2, and an image pickup signal from the CCD 36 is taken in a state where the lens barrier 10 is closed. The lens motor 31 is driven by the CPU 33 and the focus of the imaging lens 11 is adjusted with respect to the scale 12 of the lens barrier 10.
[0028]
After the focus adjustment, the CPU 33 compares the in-focus position at that time with the in-focus position stored in the EEPROM 49, and the ambient temperature of the imaging lens 11 is calculated from the comparison result. Then, from the relationship between the calculated ambient temperature and the ambient temperature stored in the EEPROM 49 and the pixel position of the CCD 36 where the defective pixel is generated, the CPU 33 detects the position of the pixel where the defective pixel is generated.
[0029]
The detection result of the defective pixel position is transmitted to the image signal processing circuit 45, and the image data of the detected pixel is checked. As a result, when it is determined that the detected pixel is a defective pixel, interpolation is performed on the image data of the surrounding pixels or a predetermined value. On the other hand, when it is determined that the pixel is not a defective pixel, the image data is output as it is without performing the interpolation process. This pixel interpolation processing is performed on image data output from the CCD 36 in the subsequent photographing.
[0030]
After the defective pixel is detected, when the still image shooting mode is selected by the mode changeover switch 23, the subject light incident through the imaging lens 11 and the diaphragm 30 is photoelectrically converted by the CCD 36, sampled by the CDS 38, and AMP39 as RGB data. Is output.
[0031]
The image data output from the CDS 38 is amplified by the AMP 39 and converted into digital data by the A / D converter 40. The digitally converted image data is stored in the SDRAM 44 via the image input controller 41 and displayed on the LCD 15 as a through image. In this state, when the release button 18 is half-pressed, a shooting preparation process is performed, and shooting is performed when the release button 18 is fully pressed.
[0032]
The image data after photographing is subjected to various image processing including the above-described pixel interpolation processing in the image signal processing circuit 45, and then converted into the luminance signal Y and the color difference signals Cr and Cb by the YC conversion processing circuit 46, and compressed. The decompression processing circuit 47 performs compression processing. The compressed image data is recorded on the memory card 20 via the media controller 48.
[0033]
As described above, the ambient temperature is calculated using the temperature characteristics of the imaging lens 11, and the defective pixel of the CCD 36 is detected based on this, so there is no need to provide a temperature sensor. Further, it is possible to correct defective pixels only by adjusting the focus on the scale 12. Therefore, when applied to a low-priced model using a plastic lens as an imaging lens, a particularly excellent effect is exhibited.
[0034]
In the above embodiment, the digital camera 2 having the lens barrier 10 attached to the main body has been described as an example. However, the present invention is also effective for the lens barrel 13 and the main body having the lens barrier built therein. Further, the scale 12 is provided on the lens barrier 10 as a specific subject. However, when there is no lens barrier, a dedicated adapter for focus adjustment is prepared, and the dedicated adapter is fitted into the lens barrel so as to be defective. Pixel detection may be performed. Furthermore, in the above embodiment, the defective pixel is detected when the power is turned on, but the detection may be performed automatically or manually while the digital camera 2 is being used.
[0035]
【The invention's effect】
As described above, according to the defective pixel correction method and the imaging apparatus of the solid-state imaging device of the present invention, the focus of the imaging lens is adjusted with respect to a specific subject, and the in-focus position at that time is stored in advance. The ambient temperature of the imaging lens is calculated from the comparison result with the in-focus position of the imaging lens with respect to a specific subject at a certain temperature, the calculated ambient temperature, and the pre-stored ambient temperature and the solid-state imaging device in which defective pixels are generated. Since the position of the pixel where the defective pixel occurs is detected from the relationship with the position of the pixel, and the image data of the detected pixel is interpolated with the image data of the surrounding pixels or a predetermined value, a temperature sensor is used. Therefore, a defective pixel can be detected in a short time.
[Brief description of the drawings]
FIG. 1 is a front perspective view of a digital camera to which the present invention is applied.
FIG. 2 is a rear perspective view of the digital camera.
FIG. 3 is a block diagram showing an electrical configuration of the digital camera.
FIG. 4 is a flowchart showing a processing procedure for defective pixel correction.
[Explanation of symbols]
2 Digital camera 10 Lens barrier 11 Imaging lens 12 Scale 13 Lens barrel 15 Liquid crystal display (LCD)
18 Release button 20 Memory card 25 Operation unit 30 Aperture 31 Lens motor 33 CPU
36 CCD
44 SDRAM
45 Image signal processing circuit 49 EEPROM

Claims (3)

In a method for correcting defective pixels of a solid-state imaging device that images subject light captured from an imaging lens and outputs image data,
Adjusting the focus of the imaging lens for a specific subject;
Calculating the ambient temperature of the imaging lens from a comparison result between the in-focus position at that time and the in-focus position of the imaging lens with respect to a specific subject at a prestored temperature;
Detecting the position of the pixel where the defective pixel is generated from the calculated ambient temperature and the relationship between the pre-stored ambient temperature and the position of the pixel of the solid-state imaging device where the defective pixel is generated;
A method of correcting defective pixels of a solid-state imaging device, comprising: interpolating detected pixel image data with peripheral pixel image data or a predetermined value. In an imaging apparatus comprising: an imaging lens that captures subject light; a focus adjustment unit that performs focus adjustment of the imaging lens; and a solid-state imaging device that images the subject light and outputs image data.
Storage means for storing a focus position of the imaging lens with respect to a specific subject at a certain temperature, and a relationship between a peripheral temperature of the imaging lens and a pixel position of a solid-state imaging device in which a defective pixel is generated;
Drive the focus adjustment means to adjust the focus of the imaging lens for a specific subject,
Temperature calculation means for calculating the ambient temperature of the imaging lens from the comparison result between the focus position at that time and the focus position stored in the storage means;
A defective pixel position detecting means for detecting the position of the pixel where the defective pixel is generated from the calculated ambient temperature and the relationship between the ambient temperature stored in the storage means and the position of the pixel;
An image pickup apparatus comprising image data of a detected pixel and pixel interpolation means for interpolating the image data of peripheral pixels with a predetermined value. The imaging apparatus according to claim 2, further comprising: a lens barrier that covers a front surface of the imaging lens, wherein a focus adjustment scale is provided on a surface of the lens barrier facing the imaging lens as the specific subject. .

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