JP5028467B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus that processes an image signal.

  2. Description of the Related Art Conventionally, an image processing apparatus such as an electronic camera that records and reproduces still images and moving images captured by a solid-state imaging device such as a CCD using a memory card having a solid-state memory device as a recording medium is already on the market.

  Among these electronic cameras, by selecting the shooting conditions such as the aperture and shutter speed, the circuit gain is switched automatically or manually, and the sensitivity equivalent to the ISO sensitivity of the film in a silver halide camera. Some can switch conditions.

  By the way, when imaging using a solid-state image sensor such as a CCD, dark image data read after charge accumulation is performed in the same manner as in the main photographing without exposing the image sensor, and charge accumulation is performed with the image sensor exposed. It is possible to perform dark noise correction processing by performing arithmetic processing using the actual captured image data read after being performed.

  As a result, it is possible to correct the captured image data and capture a high-quality image with respect to image quality deterioration such as pixel current loss due to dark current noise generated in the image sensor and minute scratches inherent to the image sensor.

  In particular, dark current noise increases according to the charge accumulation time and the temperature rise of the image sensor with the passage of time, so that a large image quality improvement effect can be obtained when performing exposure at long seconds or exposure at high temperatures. Thus, dark noise correction processing is a useful function for users of electronic cameras.

  In addition to the dark noise correction processing as described above, there is a correction processing method by interpolation using adjacent pixels having no scratch, but the correction method for pixel defects due to scratches specific to the image sensor is not so flawed. When the number is large, the burden of image processing by the CPU or the like is large, and image quality deterioration due to interpolation cannot be ignored.

  FIG. 14 is a block diagram illustrating an example of a conventional image processing apparatus such as an electronic camera. The image sensor 600, an amplifier 601, an AD (analog-digital) converter 602, a system control unit 603, an image processing unit 604, a memory control unit 605, and a memory 606 are configured.

  The image sensor 600, the amplifier 601, the AD converter 602, and the image processing unit 604 are driven by various drive signals from the system control unit 603, and the image signal read from the image sensor 600 is the amplifier 601. , The signal is amplified to a predetermined signal amplitude and input to the AD converter 602. The digital output of the AD converter 602 is input to the image processing unit 604 and recorded in the memory 606 via the memory control unit 605.

  As the operation of the dark noise correction processing, first, in a state where the imaging device is not exposed, the darkness is the flow of the imaging device 600 → the amplifier 601 → the AD converter 602 → the image processing unit 604 → the memory control unit 605 → the memory 606. Image data is recorded in the memory 606.

  Next, in a state where the image sensor is exposed, the memory control unit 604 includes the main captured image data read in the flow of the image sensor 600 → the amplifier 601 → the AD converter 602 and the dark image data recorded in the memory 606. As the dark image data is subtracted from the actual captured image data by the image processing unit 604, dark current noise included in the actual captured image and slight scratches specific to the image sensor are obtained. The pixel deficiency due to is offset and corrected.

  In such a conventional image processing device such as an electronic camera, there is an appropriate signal dynamic range for storing pixel current noise due to dark current noise or minute flaws inherent to the image sensor in dark image data used for correction. is necessary.

  However, the required signal dynamic range of the dark image data also varies depending on the switching of the circuit gain according to the ISO sensitivity. Similarly, the signal dynamic range of the captured image data varies.

  The pixel defect noise that exceeds the signal dynamic range of the dark image data remains uncorrected, and the number and degree thereof vary depending on the ISO sensitivity.

  Also, even if the total exposure conditions including the aperture and shutter speed are the same, the signal dynamic range fluctuates for each ISO sensitivity, which may cause ups and downs in the dark part of the image after dark noise correction processing. There is a problem that the saturation level of the highlight portion varies.

  FIG. 15 is an example of a signal level diagram that well explains the above problem. For the bottom voltage of the AD converter 602 (input voltage corresponding to the digital lower limit 0), for example, b is the dark signal level (average value) of the output of the image sensor 600, and s is the upper limit of the used signal amplitude at ISO 100. If the amplification of the amplifier 601 is amplified with the dark signal level b as a reference, the output of the amplifier 601 is the dark signal level b and the upper limit of the imaging signal amplitude is (a × s). At this time, since the amplitude of pixel defect noise due to scratches included in the dark signal is also multiplied by a by the amplifier 601, a noise component lower than the bottom voltage of the AD converter 602 during the dark image period, or during the actual captured image period As a result, the noise component exceeding the top voltage of the AD converter 602 (the input voltage corresponding to the digital full code) remains without being canceled by the dark noise correction processing described above.

  At this time, the upper limit of the use signal amplitude of the sensor at ISO 200 is (s / 2), the amplification degree by the amplifier 601 is further 2a times twice that at ISO 100, and the output of the amplifier 601 is dark signal level b, Although the upper limit of the imaging signal amplitude is the same as a, the amplitude of the pixel defect noise due to the scratch included in the dark signal is multiplied by 2a by the amplifier 601, so the amplitude of the noise component included in the dark image or the actual captured image is This further increases, resulting in a further increase in noise components below the bottom voltage of the AD converter 602 during the dark image period and noise components above the top voltage of the AD converter 602 during the actual captured image period.

  This tendency becomes more prominent with an increase in circuit gain as the ISO sensitivity becomes higher. In an extreme case, the dark image or the dark-corrected image after dark correction is darkened due to the overrange of the captured image with respect to the AD converter 602. This also results in deterioration of image gradation such as whiteout.

  In addition, due to restrictions on the slew rate characteristics of the amplifier circuit, the signal dynamic range of the actual captured image data when gain is increased by saturation of an over-amplitude signal due to scratch noise or by switching the circuit gain according to the ISO sensitivity described above. As the number of pixels increases, the image signal delays due to the saturation of the over-amplitude signal due to overexposure, and the adjacent pixel signal is disturbed.

  FIG. 16 is an example of a signal level diagram that well explains the above problem. For example, if the upper limit of the used signal amplitude of the output of the image sensor 600 at ISO 100 is set to 1 (near the saturation level of the image sensor 600) and the amplification factor of the amplifier 601 is a, the image signal is output at the output of the amplifier 601. The upper limit of the amplitude is a. If the output of the amplifier 601 is viewed in one pixel period, a predetermined time usually expressed in units of [ns / V] is required at the rise and fall due to the slew rate characteristics of the amplifier 601. This time depends on the signal fluctuation level of the image sensor 600 and is directly proportional.

  This characteristic results in the output of the amplifier 601 being delayed with respect to the output of the image sensor 600. At this time, the upper limit of the use signal amplitude of the sensor at ISO 200 is 0.5 (near half of the saturation level of the image sensor 150), and the amplification degree by the amplifier 601 is 2a, which is twice that at ISO 100. However, the upper limit of the imaging signal amplitude in the output of the amplifier 601 does not become a, and in reality, the output of the imaging device 600 reaches a saturation level depending on the exposure condition and reaches a maximum exceeding 2a, and the delay due to the slew rate is correspondingly increased. The result is an increase in time. This tendency becomes more prominent as the circuit gain increases as the ISO sensitivity increases, disturbing the output of the succeeding adjacent pixels configured by other color filters, and spreading the scratch noise to the succeeding adjacent pixels and the color reproducibility in the saturation region. It will also result in deterioration of.

An object of the present invention is to prevent fluctuations in gradation in dark portions and highlight portions due to different ISO sensitivities.
Another object of the present invention is to appropriately correct pixel scratches in accordance with ISO sensitivity.
It is still another object of the present invention to prevent adjacent pixels from being disturbed by an excessive signal when the ISO sensitivity is different.

According to an aspect of the present invention, an imaging unit that converts an optical image of a subject into an image signal, a clipping unit that limits an output amplitude of the imaging unit, and the image signal whose amplitude is limited by the clipping unit and amplifying means for an offset adding means for adding an offset voltage to the amplified the image signal by the amplifying means, the image signal adding an offset voltage by the offset adding means is amplified by said amplifying means into a digital signal An AD converter that performs conversion, and an offset that sets an offset voltage according to sensitivity in the offset adder so that a noise signal included in the image signal amplified by the amplifier is within an input range of the AD converter. a voltage setting means, and based on an external control signal, the clip record corresponding to the sensitivity With Le is set to the clip means, the gain in accordance with the sensitivity image processing apparatus characterized by being set to the amplification means.

  According to the present invention, a high-quality image can be obtained regardless of sensitivity conditions.

1 is an overall configuration block diagram of an embodiment of the present invention. It is a flowchart of a part of main routine of a present Example. It is a flowchart of a part of main routine of a present Example. It is a flowchart of a part of main routine of a present Example. 3 is a flowchart of a distance measurement / photometry processing routine of the present embodiment. It is a flowchart of the imaging | photography process routine of a present Example. It is a flowchart of the dark taking-in processing routine of a present Example. It is a main block diagram of the first embodiment. It is a level diagram figure of the signal in the 1st example. It is a level diagram figure of the signal in the 2nd example. It is a one part flowchart in a 2nd Example. It is a main block diagram of the third embodiment. It is a level diagram figure of the signal in the 3rd example. It is a block diagram of a conventional example. It is a level diagram of a signal. It is a level diagram of a signal.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings.
1 to 13 are diagrams showing a configuration, an operation flow, and a signal level diagram of an embodiment of the present invention.
In FIG. 1, 100 is an overall view of the image processing apparatus. Reference numeral 12 denotes a shutter for controlling the exposure amount to the imaging unit 14, and reference numeral 14 denotes an imaging unit that converts an optical image into an electrical signal.

  The light beam incident on the lens 310 can be guided through the diaphragm 312, the lens mounts 306 and 106, the mirror 130, and the shutter 12 by the single lens reflex method, and can be formed on the imaging unit 14 as an optical image.

Reference numeral 16 denotes an A / D conversion unit that converts an analog signal output from the imaging unit 14 into a digital signal.
Reference numeral 18 denotes a timing generation circuit that supplies a clock signal and a control signal to the imaging unit 14, the A / D conversion unit 16, and the D / A converter 26, and is controlled by the memory control circuit 22 and the system control circuit 50.

  An image processing circuit 20 performs predetermined pixel interpolation processing and color conversion processing on the data from the A / D conversion unit 16 or the data from the memory control circuit 22. In the image processing circuit 20, a predetermined calculation process is performed using the captured image data as necessary, and the system control circuit 50 performs exposure control means 40 and distance measurement control means based on the obtained calculation result. TTL (through-the-lens) AF (autofocus) processing, AE (automatic exposure) processing, and EF (flash light control) processing can be performed.

  Further, the image processing circuit 20 performs predetermined arithmetic processing using the captured image data, and also performs TTL AWB (auto white balance) processing based on the obtained arithmetic result.

  In the present embodiment, since the distance measuring means 42 and the photometry means 46 are exclusively provided, AF (autofocus) processing, AE (automatic exposure) processing, EF using the distance measuring means 42 and photometry means 46 are used. (Flash dimming) processing may be performed, and AF (autofocus) processing, AE (automatic exposure) processing, and EF (flash dimming) processing using the image processing circuit 20 may not be performed. good.

  Alternatively, AF (autofocus) processing, AE (automatic exposure) processing, and EF (flash dimming) processing are performed using the distance measuring means 42 and the photometry means 46, and the image processing circuit 20 is used. An AF (autofocus) process, an AE (automatic exposure) process, and an EF (flash dimming) process may be performed.

  Reference numeral 22 denotes a memory control circuit that controls the A / D conversion unit 16, the timing generation circuit 18, the image processing circuit 20, the image display memory 24, the D / A converter 26, the memory 30, and the compression / decompression circuit 32.

  The data of the A / D converter 16 is written into the image display memory 24 or the memory 30 via the image processing circuit 20 and the memory control circuit 22 or the data of the A / D converter 16 is directly passed through the memory control circuit 22. It is.

  Reference numeral 24 denotes an image display memory, 26 denotes a D / A converter, and 28 denotes an image display unit composed of a TFT LCD or the like. Display image data written in the image display memory 24 passes through the D / A converter 26. Displayed by the image display unit 28.

  If the image data captured using the image display unit 28 is sequentially displayed, the electronic viewfinder function can be realized. Further, the image display unit 28 can arbitrarily turn on / off the display according to an instruction from the system control circuit 50. When the display is turned off, the power consumption of the image processing apparatus 100 can be greatly reduced. I can do it.

  Reference numeral 30 denotes a memory for storing captured still images and moving images, and has a sufficient storage capacity to store a predetermined number of still images and a predetermined time of moving images. Thereby, even in the case of continuous shooting or panoramic shooting in which a plurality of still images are continuously shot, it is possible to write a large amount of images to the memory 30 at high speed. The memory 30 can also be used as a work area for the system control circuit 50.

  Reference numeral 32 denotes a compression / decompression circuit that compresses and decompresses image data by adaptive discrete cosine transform (ADCT) or the like, reads an image stored in the memory 30, performs compression processing or decompression processing, and stores the processed data in the memory 30. Write to.

  Reference numeral 40 denotes shutter control means for controlling the shutter 12 in cooperation with the aperture control means 340 for controlling the aperture 312 based on photometric information from the photometry means 46.

  Reference numeral 42 denotes distance measuring means for performing AF (autofocus) processing. Light beams incident on the lens 310 are converted into an aperture 312, lens mounts 306 and 106, a mirror 130, and a distance measuring sub mirror (not shown) by a single-lens reflex system. , The in-focus state of the image formed as an optical image can be measured.

  Reference numeral 46 denotes photometric means for performing AE (automatic exposure) processing. Light rays that have entered the lens 310 are converted into an aperture 312, lens mounts 306 and 106, mirrors 130 and 132, and a photometric lens (not shown) by a single-lens reflex system. Then, the exposure state of the image formed as an optical image can be measured.

The photometry means 46 also has an EF (flash dimming) processing function in cooperation with the flash 48.
A flash 48 has an AF auxiliary light projecting function and a flash light control function.

  The system control circuit 50 controls the shutter control unit 40, the aperture control unit 340, and the distance measurement control unit 342 based on the calculation result obtained by calculating the image data captured by the imaging unit 14 by the image processing circuit 20. It is also possible to perform exposure control and AF (autofocus) control using the video TTL method.

  Further, AF (autofocus) control may be performed using both the measurement result by the distance measuring means 42 and the calculation result obtained by calculating the image data captured by the imaging unit 14 by the image processing circuit 20.

  The exposure control may be performed using both the measurement result obtained by the photometry unit 46 and the calculation result obtained by calculating the image data captured by the imaging unit 14 by the image processing circuit 20.

  Reference numeral 50 denotes a system control circuit that controls the entire image processing apparatus 100, and reference numeral 52 denotes a memory that stores constants, variables, programs, and the like for operation of the system control circuit 50. Reference numeral 54 denotes a display unit such as a liquid crystal display device or a speaker that displays an operation state or a message using characters, images, sounds, or the like in accordance with execution of a program in the system control circuit 50. One or a plurality of places are provided near the portion where they can be easily seen, and for example, a combination of an LCD, an LED, a sound generation element, and the like is used.

  In addition, the display unit 54 is partially installed in the optical viewfinder 104. Among the display contents of the display unit 54, what is displayed on the LCD etc. is, for example, single shot / continuous shooting display, self-timer display, compression rate display, number of recorded pixels, number of recorded images, number of remaining images that can be captured , Shutter speed display, Aperture value display, Exposure compensation display, Flash display, Red-eye reduction display, Macro shooting display, Buzzer setting display, Clock battery level display, Battery level display, Error display, Multi-digit number information display , Attachment / detachment state display of the recording media 200 and 210, attachment / detachment state display of the lens unit 300, communication I / F operation display, date / time display, display showing a connection state with an external computer, and the like.

  In addition, among the display contents of the display unit 54, what is displayed in the optical viewfinder 104 is, for example, in-focus display, shooting preparation completion display, camera shake warning display, flash charge display, flash charge completion display, shutter speed display, There are an aperture value display, an exposure correction display, a recording medium writing operation display, and the like.

  Further, among the display contents of the display unit 54, what is displayed on the LED or the like includes, for example, in-focus display, shooting preparation completion display, camera shake warning display, camera shake warning display, flash charge display, flash charge completion display, recording medium There are a writing operation display, a macro shooting setting notification display, a secondary battery charge state display, and the like.

  And what is displayed on a lamp etc. among the display contents of the display part 54 includes a self-timer notification lamp, for example. This self-timer notification lamp may be used in common with AF auxiliary light.

Reference numeral 56 denotes an electrically erasable / recordable nonvolatile memory, such as an EEPROM.
Reference numerals 60, 62, 64, 66, 68, and 70 are operation means for inputting various operation instructions of the system control circuit 50. Consists of multiple combinations.

  Here, a specific description of these operating means will be given. Reference numeral 60 denotes a mode dial switch, which is an automatic shooting mode, program shooting mode, shutter speed priority shooting mode, aperture priority shooting mode, manual shooting mode, depth of focus priority (depth) shooting mode, portrait shooting mode, landscape shooting mode, and close-up shooting. Each function shooting mode such as a mode, a sports shooting mode, a night view shooting mode, and a panorama shooting mode can be switched and set. Reference numeral 62 denotes a shutter switch SW1, which is turned ON during operation of a shutter button (not shown), and performs AF (auto focus) processing, AE (automatic exposure) processing, AWB (auto white balance) processing, EF (flash light control) processing, and the like. Instruct to start operation.

  Reference numeral 64 denotes a shutter switch SW2, which is turned on when the operation of a shutter button (not shown) is completed, and an exposure process for writing a signal read from the imaging unit 12 to the memory 30 via the A / D conversion unit 16 and the memory control circuit 22. Development processing using operations in the image processing circuit 20 and the memory control circuit 22, recording processing for reading image data from the memory 30, compression in the compression / decompression circuit 32, and writing the image data to the recording medium 200 or 210. Instructs the start of a series of processing operations.

  Reference numeral 66 denotes a playback switch, which instructs the start of a playback operation in which a shot image is read from the memory 30 or the recording medium 200 or 210 and displayed by the image display unit 28 in the shooting mode state.

  68 is a single-shot / continuous-shot switch. When the shutter switch SW2 is pressed, the single-shot mode is set to take one frame for standby, and continuous shooting is performed while the shutter switch SW2 is pressed. You can set the mode.

  70 is an operation unit composed of various buttons, a touch panel, etc., a menu button, a set button, a macro button, a multi-screen playback page break button, a flash setting button, a single shooting / continuous shooting / self-timer switching button, menu movement + (plus) Button, menu navigation-(minus) button, playback image + (plus) button, playback image-(minus) button, shooting quality selection button, exposure compensation button, date / time setting button, panorama mode shooting and playback Selection / switch button for setting selection and switching of various functions when performing, determination / execution button for setting determination and execution of various functions when performing shooting and playback in panorama mode, etc., ON / OFF of image display unit 28 Image display ON / OFF switch for setting OFF, Quick review for automatically playing back image data taken immediately after shooting -Quick review ON / OFF switch to set the function, compression mode switch to select the CCDRAW mode to select the compression rate of JPEG compression or digitize the image signal as it is and record it on the recording medium, Playback switch that can set each function mode such as playback mode, multi-screen playback / erase mode, PC connection mode, etc.Auto focus operation starts when the shutter switch SW1 is pressed, and once it is in focus There is an AF mode setting switch that can set the one-shot AF mode that keeps the state and the servo AF mode that keeps autofocusing continuously while pressing the shutter switch SW1.

  In addition, the functions of the plus button and the minus button can be selected more easily by providing a rotary dial switch.

  Reference numeral 72 denotes a power switch, which can switch and set the power-on and power-off modes of the image processing apparatus 100. Also, the power on and power off settings of various accessory devices such as the lens unit 300, the external strobe, and the recording media 200 and 210 connected to the image processing apparatus 100 can be switched.

  Reference numeral 74 denotes a real time clock circuit, whereby the system control circuit 50 measures the elapsed time and realizes various timer functions.

  80 is a power control means, which is composed of a battery detection circuit, a DC-DC converter, a switch circuit for switching a block to be energized, etc., and detects the presence / absence of a battery, the type of battery, the remaining battery level, and the detection result In addition, the DC-DC converter is controlled based on an instruction from the system control circuit 50, and a necessary voltage is supplied to each part including the recording medium for a necessary period.

  Reference numeral 82 denotes a connector, 84 denotes a connector, and 86 denotes a power source means including a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, a NiMH battery, or a Li battery, or an AC adapter.

  90 and 94 are interfaces with a recording medium such as a memory card or a hard disk, 92 and 96 are connectors for connecting to a recording medium such as a memory card or a hard disk, and 98 is a recording medium 200 or 210 attached to the connector 92 and / or 96. It is a recording medium attachment / detachment detecting means for detecting whether or not the recording medium is being used.

  In this embodiment, it is assumed that there are two interfaces and connectors for attaching the recording medium. Of course, the interface and the connector for attaching the recording medium may have a single or a plurality of systems and any number of systems. Moreover, it is good also as a structure provided with combining the interface and connector of a different standard.

  The interface and the connector may be configured using a PCMCIA card, a CF (Compact Flash (registered trademark)) card, or the like that conforms to a standard.

  In addition, when the interfaces 90 and 94 and the connectors 92 and 96 are configured using PCMCIA cards, CF (compact flash) cards, or other standards, LAN cards, modem cards, USB cards, IEEE1394 cards, P1284 cards By connecting various communication cards such as SCSI cards, communication cards such as PHS, etc., image data and management information attached to the image data can be transferred to and from other computers and peripheral devices such as printers. I can do it.

  Reference numeral 104 denotes an optical viewfinder, which can guide and display a light beam incident on the lens 310 through an aperture 312, lens mounts 306 and 106, and mirrors 130 and 132 as an optical image by a single lens reflex system. Accordingly, it is possible to perform shooting using only the optical viewfinder 104 without using the electronic viewfinder function of the image display unit 28. In the optical viewfinder 104, some functions of the display unit 54, for example, a focus display, a camera shake warning display, a flash charge display, a shutter speed display, an aperture value display, an exposure correction display, and the like are installed.

  A communication unit 110 has various communication functions such as RS232C, USB, IEEE1394, P1284, SCSI, modem, LAN, and wireless communication.

  Reference numeral 112 denotes a connector for connecting the image processing apparatus 100 to another device by the communication unit 110 or an antenna in the case of wireless communication.

  Reference numeral 120 denotes an interface for connecting the image processing apparatus 100 to the lens unit 300 in the lens mount 106, 122 denotes a connector for electrically connecting the image processing apparatus 100 to the lens unit 300, and 124 denotes the lens mount 106 and / or the connector. Reference numeral 122 denotes lens attachment / detachment detection means for detecting whether or not the lens unit 300 is attached.

  The connector 122 communicates control signals, status signals, data signals, and the like between the image processing apparatus 100 and the lens unit 300, and also has a function of supplying currents of various voltages. The connector 122 may be configured to transmit not only electrical communication but also optical communication, voice communication, and the like.

  Reference numerals 130 and 132 denote mirrors that can guide the light beam incident on the lens 310 to the optical viewfinder 104 by a single-lens reflex system. The mirror 132 may be either a quick return mirror or a half mirror.

  Reference numeral 200 denotes a recording medium such as a memory card or a hard disk. The recording medium 200 includes a recording unit 202 composed of a semiconductor memory, a magnetic disk, or the like, an interface 204 with the image processing apparatus 100, and a connector 206 for connecting to the image processing apparatus 100.

  Reference numeral 210 denotes a recording medium such as a memory card or a hard disk. The recording medium 210 includes a recording unit 212 composed of a semiconductor memory, a magnetic disk, and the like, an interface 214 with the image processing apparatus 100, and a connector 216 that connects to the image processing apparatus 100.

  Reference numeral 300 denotes an interchangeable lens type lens unit. Reference numeral 306 denotes a lens mount that mechanically couples the lens unit 300 to the image processing apparatus 100. The lens mount 306 includes various functions for electrically connecting the lens unit 300 to the image processing apparatus 100.

  Reference numeral 310 denotes a photographing lens, and 312 denotes an aperture. Reference numeral 320 denotes an interface for connecting the lens unit 300 to the image processing apparatus 100 in the lens mount 306, and reference numeral 322 denotes a connector for electrically connecting the lens unit 300 to the image processing apparatus 100.

  The connector 322 transmits a control signal, a status signal, a data signal, and the like between the image processing apparatus 100 and the lens unit 300, and also has a function of supplying or supplying currents of various voltages. The connector 322 may be configured to transmit not only electrical communication but also optical communication, voice communication, and the like.

  Reference numeral 340 denotes aperture control means for controlling the aperture 312 in cooperation with the shutter control means 40 for controlling the shutter 12 based on photometric information from the photometry means 46.

  Reference numeral 342 denotes distance measurement control means for controlling the focusing of the photographing lens 310, and reference numeral 344 denotes zoom control means for controlling zooming of the photographing lens 310.

  A lens system control circuit 350 controls the entire lens unit 300. The lens system control circuit 350 includes a memory for storing operation constants, variables, programs and the like, identification information such as a number unique to the lens unit 300, management information, function information such as an open aperture value, a minimum aperture value, a focal length, It also has a non-volatile memory function for holding current and past set values.

2 to 4 show flowcharts of the main routine of the image processing apparatus 100 according to the embodiment of the present invention.
The operation of the image processing apparatus 100 will be described with reference to FIGS. Upon power-on such as battery replacement, the system control circuit 50 initializes flags, control variables, and the like, and performs predetermined initial settings necessary for each unit of the image processing apparatus 100 (S101).

  The system control circuit 50 determines the setting position of the power switch 66, and if the power switch 66 is set to power OFF (S102), the display of each display unit is changed to the end state, and a flag, a control variable, etc. Required parameters, setting values, and setting modes including the image display unit 28 are recorded in the non-volatile memory 56, and a predetermined end process such as shutting off unnecessary power sources of the respective units of the image processing apparatus 100 including the image display unit 28 by the power control unit 80 is performed. After that (S103), the process returns to S102.

  If the power switch 66 is set to ON (S102), the system control circuit 50 determines that the remaining capacity and the operation status of the power supply 86 constituted by a battery or the like by the power control means 80 are the operations of the image processing apparatus 100. It is determined whether or not there is a problem (S104). If there is a problem, a predetermined warning is displayed by an image or sound using the display unit 54 (S105), and the process returns to S102.

  If there is no problem with the power supply 86 (S104), the system control circuit 50 determines the setting position of the mode dial 60. If the mode dial 60 is set to the photographing mode (S106), the process proceeds to S108.

  If the mode dial 60 has been set to another mode (S106), the system control circuit 50 executes processing corresponding to the selected mode (S107), and returns to S102 when the processing is completed.

  The system control circuit 50 determines whether or not the recording medium 200 or 210 is mounted, acquires management information of image data recorded on the recording medium 200 or 210, and determines whether the operation state of the recording medium 200 or 210 is image processing. It is determined whether or not there is a problem in the operation of the apparatus 100, particularly the recording / reproducing operation of the image data with respect to the recording medium (S108), and if there is a problem, a predetermined warning is displayed by an image or sound using the display unit 54. After performing (S105), it returns to S102.

  Determination of whether or not the recording medium 200 or 210 is mounted, acquisition of management information of image data recorded on the recording medium 200 or 210, and the operation state of the recording medium 200 or 210 are the operations of the image processing apparatus 100, particularly As a result of determining whether there is a problem in the recording / reproducing operation of the image data with respect to the recording medium (S108), if there is no problem, the process proceeds to S109.

  The system control circuit 50 checks the setting state of the single / continuous shooting switch 68 for setting single shooting / continuous shooting (S109). If single shooting is selected, the single / continuous shooting flag is set. If the continuous shooting is selected, the single / continuous shooting flag is set to continuous shooting (S111). If the flag setting is completed, the process proceeds to S113.

  According to the single-shot / continuous-shot switch 68, when the shutter switch SW2 is pressed, the single-shot mode in which one frame is shot to enter a standby state, and continuous shooting is performed while the shutter switch SW2 is pressed. It is possible to change the setting by arbitrarily switching the copy mode.

  The state of the single / continuous shooting flag is stored in the internal memory of the system control circuit 50 or the memory 52, and the process proceeds to S113.

  The system control circuit 50 displays various setting states of the image processing apparatus 100 using images and sounds using the display unit 54 (S113). If the image display of the image display unit 28 is ON, the image display unit 28 is also used to display various setting states of the image processing apparatus 100 using images and sounds.

  If the shutter switch SW1 is not pressed (S121), the process returns to S102.

  If the shutter switch SW1 is pressed (S121), the system control circuit 50 performs a distance measurement process to focus the photographing lens 10 on the subject, performs a photometry process, and determines an aperture value and a shutter time. Distance / photometry processing is performed (S122), and the process proceeds to S124. In the photometric process, the flash is set if necessary. Details of the distance measurement / photometry processing S122 will be described later with reference to FIG.

  Thereafter, the system control circuit 50 performs a dark capturing process of accumulating noise components such as dark current of the image sensor 14 for a preset time with the shutter 12 closed, and reading out the noise image signal after the accumulation ( S124), the process proceeds to S125.

  By performing the correction calculation process using the dark image data captured in the dark capturing process, the captured image data is related to image quality degradation such as dark current noise generated by the image sensor 14 and pixel defects due to scratches unique to the image sensor 14. Can be corrected. Details of the dark capturing process S124 will be described later with reference to FIG.

  If the shutter switch SW2 is not pressed (S125), the current process is repeated until the shutter switch SW1 is released (S126). If the shutter switch SW1 is released (S126), the process proceeds to S502.

  If the shutter switch SW2 is pressed (S125), the system control circuit 50 determines whether there is an image storage buffer area in the memory 30 that can store the captured image data (S127), and stores the image in the memory 30. If there is no area where new image data can be stored in the buffer area, a predetermined warning is displayed with an image or sound using the display unit 54 (S128), and the process proceeds to S502.

  For example, immediately after performing the maximum number of continuous shots that can be stored in the image storage buffer area of the memory 30, the first image to be read from the memory 30 and written to the storage medium 200 or 210 is still in the recording medium 200 or 210. An example of this state is an unrecorded state where one empty area cannot be secured in the image storage buffer area of the memory 30 yet.

  When the captured image data is compressed and stored in the image storage buffer area of the memory 30, it can be stored in consideration of the fact that the amount of compressed image data varies depending on the compression mode setting. Whether or not the area is on the image storage buffer area of the memory 30 is determined in S127.

  If there is an image storage buffer area capable of storing the image data captured in the memory 30 (S127), the system control circuit 50 reads out the imaged signal that has been imaged and accumulated for a predetermined time from the imaging unit 12, and performs A / D conversion. The photographing process of writing the image data photographed in a predetermined area of the memory 30 through the unit 16, the image processing circuit 20, the memory control circuit 22, or directly from the A / D converter through the memory control circuit 22 is executed ( S129). Details of the photographing process S129 will be described later with reference to FIG.

  When the photographing process S129 is completed, the system control circuit 50 reads a part of the image data written in the predetermined area of the memory 30 through the memory control circuit 22 and performs WB (necessary for performing the development process. White balance) integration calculation processing and OB (optical black) integration calculation processing are performed, and the calculation result is stored in the internal memory or the memory 52 of the system control circuit 50.

  The system control circuit 50 reads the captured image data written in a predetermined area of the memory 30 using the memory control circuit 22 and, if necessary, the image processing circuit 20, and stores the internal memory or memory of the system control circuit 50. Various development processes including an AWB (auto white balance) process, a gamma conversion process, and a color conversion process are performed using the calculation result stored in 52 (S132).

  Further, in the development processing, dark correction calculation processing for canceling dark current noise and the like of the imaging unit 14 is also performed by performing subtraction processing using the dark image data captured in the dark capturing processing.

  Then, the system control circuit 50 reads the image data written in the predetermined area of the memory 30 and performs the image compression processing according to the set mode by the compression / decompression circuit 32 (S133), and the image storage buffer of the memory 30 Image data that has been photographed and completed a series of processing is written in the empty image portion of the area.

  Along with execution of a series of photographing, the system control circuit 50 reads out the image data stored in the image storage buffer area of the memory 30 and uses a memory card, a compact flash card, or the like via the interface 90 or 94 and the connector 92 or 96. The recording process for writing to the recording medium 200 or 210 is started (S134).

  This recording start process is performed on the image data every time new image data that has been shot and finished a series of processes is newly written in the empty image portion of the image storage buffer area of the memory 30.

  Note that while writing image data to the recording medium 200 or 210, in order to clearly indicate that the writing operation is being performed, the display unit 54 performs a recording medium writing operation display such as blinking an LED.

  The system control circuit 50 determines whether or not the shutter switch SW1 is pressed (S135).

  If the shutter switch SW1 has been released (S135), the process returns to S102. If the shutter switch SW1 has been pressed (S135), the state of the single / continuous shooting flag stored in the internal memory of the system control circuit 50 or the memory 52 is determined (S136), and single shooting is set. If so, the process returns to S135 and the current process is repeated until SW1 is released.

  If continuous shooting has been set (S136), the flow returns to S125 to perform continuous shooting, and the next shooting is performed.

  FIG. 5 shows a detailed flowchart of the distance measurement / photometry process in S122 of FIG. In the distance measurement / photometry processing, the exchange of various signals between the system control circuit 50 and the aperture control means 340 or the distance measurement control means 342 is performed by the interface 120, the connector 122, the connector 322, the interface 320, and the lens control means. 350.

  The system control circuit 50 starts an AF (autofocus) process using the imaging unit 14, the distance measurement means 42, and the distance measurement control means 342 (S201).

  The system control circuit 50 causes the light beam incident on the lens 310 to enter the distance measuring means 42 through the stop 312, the lens mounts 306 and 106, the mirror 130, and the distance measuring sub mirror (not shown), thereby forming an optical image. The focus state of the formed image is determined, and the distance measuring means 42 is operated while driving the lens 310 using the distance control means 342 until the distance measurement (AF) is determined to be in focus (S203). The AF control for detecting the in-focus state is executed (S202).

  If distance measurement (AF) is determined to be in focus (S203), the system control circuit 50 determines a focused distance point from a plurality of distance measurement points on the shooting screen, and the determined distance measurement point. Ranging data and / or setting parameters are stored in the internal memory of the system control circuit 50 or the memory 52 together with the data, and the process proceeds to S205.

  Subsequently, the system control circuit 50 starts an AE (automatic exposure) process using the photometry means 46 (S205).

  The system control circuit 50 causes the light beam incident on the lens 310 to enter the photometric means 46 through the stop 312, the lens mounts 306 and 106, the mirrors 130 and 132, and a photometric lens (not shown), thereby forming an optical image. The exposure state of the formed image is measured, and photometric processing is performed using the exposure control means 40 (S206) until the exposure (AE) is determined to be appropriate (S206).

  If it is determined that the exposure (AE) is appropriate (S207), the system control circuit 50 stores the photometric data and / or the setting parameters in the internal memory or the memory 52 of the system control circuit 50, and proceeds to S208.

  The system control circuit 50 determines the aperture value (Av value) and the shutter speed (Tv value) according to the exposure (AE) result detected in the photometric process S206 and the shooting mode set by the mode dial 60. .

  Then, in accordance with the shutter speed (Tv value) determined here, the system control circuit 50 determines the charge accumulation time of the imaging unit 14, and performs the photographing process and the dark capturing process with the same charge accumulation time.

  Based on the measurement data obtained in the photometric process S206, the system control circuit 50 determines whether or not a flash is necessary (S208), sets a flash flag if the flash is necessary, and until the flash 48 is completely charged (S210). ) And charge the flash 48 (S209).

  When the charging of the flash 48 is completed (S210), the distance measurement / photometry processing routine S122 is terminated.

  FIG. 6 shows a detailed flowchart of the photographing process in S129 of FIG. In the photographing process, various signals are exchanged between the system control circuit 50 and the aperture control unit 340 or the distance measurement control unit 342 via the interface 120, the connector 122, the connector 322, the interface 320, and the lens control unit 350. Done.

  The system control circuit 50 moves the mirror 130 to the mirror-up position by a mirror driving unit (not shown) (S301), and the aperture control unit 340 performs the photometry data stored in the internal memory or the memory 52 of the system control circuit 50. The diaphragm 312 is driven to a predetermined diaphragm value (S302).

  The system control circuit 50 performs the charge clear operation of the imaging unit 14 (S303), starts the charge accumulation of the imaging unit 14 (S304), opens the shutter 12 by the shutter control unit 40 (S305), and performs imaging. The exposure of the unit 14 is started (S306).

  Here, it is determined whether or not the flash 48 is necessary based on the flash flag (S307), and if necessary, the flash is emitted (S308).

  The system control circuit 50 waits for the exposure of the imaging unit 14 to end according to the photometric data (S309), closes the shutter 12 by the shutter control means 40 (S310), and ends the exposure of the imaging unit 14.

  The system control circuit 50 drives the diaphragm 312 to the open diaphragm value by the diaphragm control means 340 (S311), and moves the mirror 130 to the mirror down position by the mirror driving means (not shown) (S312).

If the set charge accumulation time has elapsed (S313), the system control circuit 50 reads out the charge signal from the imaging unit 14 after completing the charge accumulation in the imaging unit 14 (S314), and the A / D conversion unit 16, The photographed image data is written to a predetermined area of the memory 30 via the image processing circuit 20, the memory control circuit 22, or directly from the A / D conversion unit 16 via the memory control circuit 22 (S315).
When the series of processing is finished, the photographing processing routine S129 is finished.

  FIG. 7 shows a detailed flowchart of the dark capturing process in S112 of FIG. 2 and S124 of FIG. After performing the charge clear operation of the imaging unit 14 (S401), the system control circuit 50 starts charge accumulation in the imaging unit 14 with the shutter 12 closed (S402).

  When the set predetermined charge accumulation time has elapsed (S403), the system control circuit 50 ends the charge accumulation of the image pickup unit 14 (S404), and then reads out the charge signal from the image pickup unit 14, and the A / D conversion unit. 16, the image data (dark image data) is written to a predetermined area of the memory 30 via the image processing circuit 20, the memory control circuit 22, or directly from the A / D converter 16 via the memory control circuit 22 (S405). ).

  By performing development processing using this dark capture data, it is possible to correct the captured image data with respect to image quality degradation such as dark current noise generated by the imaging unit 14 and pixel defects due to scratches specific to the imaging unit 14.

  The dark image data is held in a predetermined area of the memory 30 until a new distance measurement / photometry process is performed or the image processing apparatus 100 is turned off.

  The dark image data is then subjected to a photographing process. The dark image data is used when the photographed image data is read from the imaging unit 14 and the development process is performed.

Alternatively, the image capturing process is executed first, and the captured image data is read from the image capturing unit 14 and written in the memory 30, and is used when the developing process is performed using the dark image data.
Then, the dark capturing process routine S124 is terminated.

(First embodiment)
FIG. 8 is a block diagram showing a more detailed configuration of the inside of the image pickup apparatus unit 15 including the image pickup section 14 and the A / D conversion section 16 in the image processing apparatus 100, and plays a main role in this embodiment. Part.

  In FIG. 8, reference numeral 400 denotes an image sensor, which is a photoelectric conversion device such as a CCD. 401 is an amplifier that amplifies the amplitude of the output signal of the image sensor 400, 402 is an offset adder that adds a predetermined DC voltage to the amplified output of the amplifier 401, and 405 is an analog image output of the offset adder 402 that is converted into a digital signal. It is an A / D converter for conversion. Reference numeral 408 denotes a multi-channel D / A converter that supplies a plurality of DC voltages to the offset adder 402 and the A / D converter 405. Each DC voltage value is timed from the system controller 50 shown in FIG. It is controlled by a control bus 406 supplied via the generator 18.

  One channel output 407 of the output of the D / A converter 408 is supplied to the offset adder 402, whereby the DC voltage of the imaging signal supplied to the A / D converter 405 is switched. From the other channels of the output of the D / A converter 408, a bottom voltage 409 and a top voltage 410 that determine the analog input range of the A / D conversion 405 are output.

  The control bus 406 supplied from the timing generator 18 shown in FIG. 1 to the imaging device 400, the amplifier 401 of the imaging device unit 15 and the D / A converter 408 is exposed and read out by the imaging device 400. For controlling various drive pulses, a state control signal for switching the gain of the amplifier 401 to a plurality of predetermined values, and D / A output voltages for a plurality of channels of the D / A converter 408 A control signal is included, and these control values are switched according to photographing conditions such as ISO sensitivity.

  The image pickup signal read from the image pickup device 400 is amplified to a predetermined signal amplitude via the amplifier 401, added with a predetermined DC voltage by the offset adder 402, and then input to the AD converter 405. Is done. The digital output of the AD converter 405 is input to the image processing unit 20 of FIG. 1 and recorded in the memory 30 via the memory control unit 22.

  As described in the flowcharts of FIGS. 2 to 4, first, as an operation of the dark noise correction process, in a state where the image sensor is not exposed, the image sensor 400 → the amplifier 401 → the offset adder 402 → the AD converter 405 → image processing. The dark image data is recorded in the memory 30 in the flow of section 20 → memory control section 22 → memory 30.

  Next, in a state where the image sensor is exposed, the actual captured image data read in the flow of the image sensor 400 → the amplifier 401 → the offset adder 402 → the AD converter 405, the dark image data recorded in the memory 30, and Is read out via the memory control unit 22, and dark image data is subtracted from the actual captured image data by the image processing unit 20, so that the dark current noise and the image sensor included in the actual captured image are the same as the dark image. Pixel defects due to inherent minute flaws are offset and corrected.

  FIG. 9 is a level diagram of the output signal of the image sensor 400 of FIG. 8 and the output signal of the offset adder 402. Next, the signal processing in FIG. 8 will be specifically described using the signal level diagram of FIG.

  The dark image signal read without exposing the image sensor 400 is first output from the image sensor 400 with an offset voltage b with respect to the bottom voltage of the AD converter 405. If the maximum amplitude of a noise signal such as a flaw or a pixel defect included in the dark signal image signal is n, then the main image signal read out without exposing the image sensor 400 next to the dark image signal. Also, a noise signal having a maximum amplitude n correlated with the noise signal of the dark image signal is included. At this time, if the signal amplitude of the main image signal based on the dark image signal is s, and the gain setting by the amplifier 401 is a times when the sensitivity of the apparatus is ISO 100 setting, the amplified output by the amplifier 401 is the signal amplitude. Becomes (a × s), and the noise amplitude becomes (a × n).

  When the sensitivity of the apparatus is set to ISO 200, the dark image signal output from the image sensor 400 and the noise signal included therein are exactly the same as in the ISO 100 setting, but the dark image signal is used as a reference. The signal amplitude of the actual captured image signal becomes (s / 2) by the exposure amount of 1/2 when ISO 100 is set, and the gain setting by the amplifier 401 when ISO 200 is set is twice that when ISO 100 is set. It becomes a certain (2 × a) times. The amplified output by the amplifier 401 at this time has a signal amplitude of (a × s) and a noise amplitude of (2a × n). Therefore, when ISO 200 is set, the signal amplitude is the same and only the noise amplitude is doubled compared to when ISO 100 is set.

  Therefore, in this embodiment, when the sensitivity of the apparatus is set to ISO 100, the noise signal in the dark image signal, the signal amplitude in the actual captured image signal, and the noise signal included therein are appropriately AD. First, the gain of the amplifier 401 for setting ISO 100 is set in the flow of control of the system controller 50 → the timing generator 18 → the control bus 406 → the amplifier 401 so as to be within the input range of the converter 405.

  Next, in the control flow of the system controller 50 → the timing generator 18 → the control bus 406 → the D / A converter 408, the offset voltage c with respect to the bottom voltage of the AD converter 405 and AD The bottom voltage and top voltage of the converter 405 are set.

  That is, a bottom voltage lower than the lower limit of the noise signal component during the dark image period is set, and a top voltage higher than the upper limit of the image signal and the noise signal component included in the image signal during the main photographing period is set. The input amplitude range d of the AD converter 405 is given by the difference between the top voltage and the bottom voltage set at this time.

  Even when ISO 200 is set, the noise signal in the dark image signal, the signal amplitude in the actual captured image signal, and the noise signal included therein are appropriately AD-converted by the same procedure as in ISO setting. The offset voltage e with respect to the bottom voltage of the AD converter 405 and the bottom voltage and top voltage (input amplitude range f) of the AD converter 405 are set for the output signal of the amplifier 401 so as to be within the input range of the converter 405. Is done. That is, also in this case, a bottom voltage lower than the lower limit of the noise signal component during the dark image period is set, and a top voltage higher than the upper limit of the image signal and the noise signal component included in the image signal during the main photographing period is set. .

  By the way, when the ISO 200 is set, the signal amplitude is the same and only the noise amplitude is doubled compared to the ISO 100 setting. Therefore, in order to fit this noise signal in the input range of the AD converter 405, the corresponding amount is required. Therefore, the input range f at ISO 200 is larger than the input range d at ISO 100. Therefore, if the signal amplitude at the time of input to the AD converter 405 is the same, the digital output after A / D conversion is (d / f) times that of ISO 100, and this amount of gain correction is The image processing unit 20 in FIG. 1 performs the digital calculation.

  The offset voltages c and e and the bottom voltage and top voltage (input amplitude ranges d and f) of the AD converter 405 in each case of ISO 100 and ISO 200 set here are preliminarily stored in the non-volatile state shown in FIG. 1 as control parameters in the system. The data is stored in the memory, and is read and set by the system control unit 50 as necessary.

  In the setting, the input range of the AD converter 405 is variable between d and f (f> d) between ISO 100 and ISO 200. However, the offset voltage and the AD converter are set so that the noise signal in the dark image signal, the signal amplitude in the actual captured image signal, and the noise signal included therein are appropriately within the input range of the AD converter 405. Setting the input range of 405 is the main point of the present embodiment, and of course, the input range can be fixed (f = d) along the main point. In this case, since the input range at the time of ISO 100 is essentially raised from the necessary range d to f, the quantization noise at the time of A / D conversion increases accordingly. However, since there is no fluctuation in the input range, there is an advantage that gain correction by digital calculation for each ISO is unnecessary.

  In this embodiment, the ISO sensitivity is set only for ISO 100 and ISO 2002. However, the present embodiment can be applied to a higher ISO sensitivity setting, and the same effect can be expected.

(Second embodiment)
By the way, only the dark noise correction processing using the dark image as in the above-described embodiment increases the input range required for the noise signal as the amplitude of the noise signal included in the actual captured image signal increases. However, since the increase in quantization noise caused by this causes deterioration of the actual captured image signal, it is particularly necessary to deal with all the scratches such as a high ISO sensitivity condition and a scratch noise with a small frequency but extremely high level skip. Is difficult.

  Therefore, the second embodiment is a method in which a correction processing method based on interpolation using adjacent pixels having no flaws is combined with the above-described embodiment and adapted well.

  The basic configuration of hardware and the flow of the main routine are exactly the same as those described in the first embodiment with reference to FIGS. 1 to 8, and are omitted here, and only the parts different from the first embodiment are described. Will be explained.

  FIG. 10 is a level diagram of the output signal of the image sensor 400 of FIG. 8 and the output signal of the offset adder 402.

  In FIG. 10, the difference from the first embodiment is how to give each AD input range to the AD input signal when ISO 100 and ISO 200 are set. That is, in the first embodiment, the noise signal in the dark image signal, the signal amplitude in the actual captured image signal, and the noise signal included therein are all within the input range of the AD converter 405. However, in this embodiment, noise outside the input range is partially set. In the same manner as in the above embodiment, the noise outside the input range is processed by the system control unit 50 in FIG. 1 by the image processing unit 20 after the dark noise correction processing using the dark image is completed. Correction is performed by interpolation using adjacent pixels that are free from scratches. Correction by interpolation is performed by replacing the data of the corresponding flaw pixel with the calculation results of the upper and lower and left and right adjacent pixels, and the algorithm is various, but the content is not mentioned here. Of course, these arithmetic processes may be realized by a hardware method.

  The positions of defective pixels and the size of the flaw due to a flaw unique to the image sensor 400 are detected in advance, and are grouped into a plurality of groups according to the size of the flaw. The method of setting the input range of the AD converter 405 for each ISO sensitivity setting is determined based on the magnitude of noise and the number of noise generated outside the input range.

  FIG. 11 shows an example of a defect correction flow by interpolation for each ISO sensitivity in accordance with the three sensitivity conditions of ISO100, ISO200, and ISO400.

  Here, in order from the largest scratch, according to the size of the scratch, the scratch group 1, the scratch group 2, the scratch group 3, and the number of scratches in each group are set to a predetermined number. Grouped into two groups. Each group is held in the nonvolatile memory of FIG. 1 together with scratch position information. At the time of defect correction, these data are read out as needed to correct the defect pixel.

  First, branch processing is performed according to the ISO sensitivity setting condition (S401). In the case of ISO 100, only correction by the scratch group 3 is performed (S404), and the process is terminated. In the case of ISO 200, correction by the scratch group 2 is performed (S403), and then only correction by the scratch group 3 is performed (S404), and the process ends. In the case of ISO400, the correction by the scratch group 1 is performed (S402), the correction by the scratch group 2 is subsequently performed (S403), the correction by the scratch group 3 is subsequently performed (S404), and the process ends.

  As a result, the higher ISO sensitivity increases the number of defect groups to be corrected, and the processing is divided so that larger defects and more defects are corrected.

  The number of scratches corrected by this interpolation takes into account the balance between image quality degradation due to an increase in the noise range in dark noise correction processing and image quality degradation and processing load (processing time) in scratch correction processing due to interpolation. Are optimally distributed for each ISO sensitivity condition.

  In this embodiment, the ISO sensitivity setting is described only for three cases of ISO100, ISO200, and ISO400. However, the present invention can be applied to a further high ISO sensitivity setting, and the same effect is expected. it can.

(Third embodiment)
By the way, when the gain is increased by switching the circuit gain in accordance with the ISO sensitivity, the signal dynamic range of the actual captured image data increases, and due to restrictions on the slew rate of the circuit, the over-amplitude signal due to overexposure, scratch noise, etc. As described in the above-described conventional example, there is a problem that a delay of an image signal occurs due to saturation and interference occurs with respect to subsequent adjacent pixel signals.

  In this case, the scratch correction method in which the scratch pixel is interpolated by the adjacent pixel due to the spread of the scratch noise to the subsequent adjacent pixel does not work very effectively.

  Therefore, for over-amplitude signals due to overexposure, scratch noise, etc., we have devised to suppress oversaturation of the output of the amplifier circuit for each ISO sensitivity so that scratch correction by interpolation works more effectively, or color reproduction in the saturation region The third embodiment is a method for preventing the deterioration of the property.

  The basic configuration of hardware and the flow of the main routine are exactly the same as those described in the first embodiment with reference to FIGS. 1 to 7, and are omitted here, and only the parts different from the first embodiment are described. Will be explained.

  FIG. 12 is a block diagram showing a more detailed configuration of the inside of the image pickup apparatus unit 15 including the image pickup section 14 and the A / D conversion section 16 in the image processing apparatus 100, and plays a main role in this embodiment. Part.

  In FIG. 12, reference numeral 500 denotes an image sensor, which is a photoelectric conversion device such as a CCD. Reference numeral 511 denotes a clip circuit that limits the output amplitude of the image sensor 500, reference numeral 501 denotes an amplifier that amplifies the output signal of the clip circuit 511, reference numeral 502 denotes an offset adder that adds a predetermined DC voltage to the amplified output of the amplifier 501, Reference numeral 505 denotes an A / D converter that converts the analog imaging output of the offset adder 502 into a digital signal. Reference numeral 508 denotes a multi-channel D / A converter that supplies a plurality of DC voltages to the clip circuit 511, the offset adder 502, and the A / D converter 505. Each DC voltage value is controlled by the system control shown in FIG. Control is performed by a control bus 506 supplied from the unit 50 via the timing generator 18.

  One channel output 512 of the output of the D / A converter 508 is supplied to the clip circuit 511, and the other one channel output 507 of the output of the D / A converter 508 is supplied to the offset adder 502. As a result, the DC voltage of the imaging signal supplied to the A / D conversion 505 is switched. From other channels of the output of the D / A converter 508, a bottom voltage 509 and a top voltage 510 that determine an analog input range of the A / D conversion 505 are output.

  Then, the image sensor 500, the amplifier 501 of the image pickup apparatus unit 15, and the D / A converter 508 supplied from the timing generator 18 shown in FIG. For controlling various drive pulses for controlling, etc., a state control signal for switching the gain of the amplifier 501 to a plurality of predetermined values, and D / A output voltages of a plurality of channels of the D / A converter 508. These control values are switched according to photographing conditions such as ISO sensitivity.

  The image pickup signal read out from the image pickup device 500 is amplified to a predetermined signal amplitude via the clip circuit 511 and the amplifier 501, and after a predetermined DC voltage is added by the offset adder 502, AD conversion is performed. Is input to the device 505. The digital output of the AD converter 505 is input to the image processing unit 20 of FIG. 1 and recorded in the memory 30 via the memory control unit 22.

  As described in the flowcharts of FIGS. 2 to 5, first, as an operation of dark noise correction processing, in a state where the image sensor is not exposed, the image sensor 500 → the clip circuit 511 → the amplifier 501 → the offset adder 502 → the AD converter. Dark image data is recorded in the memory 30 in the flow of 505 → image processing unit 20 → memory control unit 22 → memory 30.

  Next, in a state where the image sensor is exposed, the actual image data read in the flow of the image sensor 500 → the clip circuit 511 → the amplifier 501 → the offset adder 502 → the AD converter 505 and the recorded image data are recorded in the memory 30. The dark image data is read out via the memory control unit 22, and the dark current data included in the actual captured image as in the dark image is obtained by subtracting the dark image data from the actual captured image data by the image processing unit 20. Pixel deficiencies due to noise and minute flaws inherent to the image sensor are offset and corrected.

  The operation of the dark noise correction processing around this is the same as the above except that a clip circuit 511 is newly added between the image sensor 500 and the amplifier 501.

  FIG. 13 is a level diagram for one pixel period of the output signal of the image sensor 500 of FIG. 12 and the output signal of the amplifier 501. Next, the signal processing in FIG. 12 will be described in detail using the signal level diagram of FIG.

  The maximum range of the photographic signal can be defined as the amplitude from the dark signal level at the output of the imaging device 500 to the upper limit level that is actually used as the imaging signal.

  When the sensitivity of the apparatus is set to ISO 100, the maximum range of the photographing signal at this time is set as a reference value 1. The clip level voltage in the clip circuit 511 when ISO 100 is set is set by the system control unit 50 to a voltage that is equal to or slightly larger than the maximum range of the imaging signal. If the gain setting of the amplifier 501 when ISO 100 is set is a times, the amplified signal output of the amplifier 501 at this time becomes the value a. In this case, for example, even if an excessive signal level greatly exceeding the maximum range of the photographic signal is generated in the output of the imaging device 500 regardless of the original imaging signal level due to the influence of scratch noise or the like, the clip circuit 511 Since an output level higher than the set clip voltage is not applied to the amplifier 501, the output of the amplifier 501 is the same as or slightly larger than the upper limit value a of the amplified output amplitude in this case as well. The delay of the image signal due to oversaturation does not disturb the subsequent adjacent pixels.

  Further, when the sensitivity of the apparatus is set to ISO 200, the maximum range of the photographing signal at this time is 0.5, which is a half of that when ISO 100 is set, so that the clip in the clip circuit 511 when ISO 200 is set The level voltage is set by the system control unit 50 to a voltage equal to or slightly larger than the maximum range. The gain setting of the amplifier 501 when ISO 200 is set is 2a times that is twice that when ISO 100 is set, and the amplified signal output of the amplifier 501 at this time is the value a. In this case, an excessive signal level exceeding the maximum range 0.5 of the photographic signal can easily be generated depending on exposure conditions as well as the influence of scratch noise or the like, but it exceeds the clip voltage set by the clip circuit 511. Since the output level of the amplifier 501 is not given to the amplifier 501, the output of the amplifier 501 again remains the same as or slightly larger than the upper limit value a of the amplified output amplitude. The signal delay does not interfere with subsequent adjacent pixels.

  In this embodiment, the ISO sensitivity setting is described only in two cases of ISO 100 and ISO 200. However, the maximum use range of the shooting signal is defined for the higher ISO sensitivity setting, and the clip is set. This can be applied by setting the clip level voltage in the circuit 511 to a voltage that is equal to or slightly larger than the maximum range of the imaging signal, and a similar effect can be expected.

  In the first to third embodiments, the processing means corresponds to at least one of the offset adder 402, the AD converter 405, the image processing circuit 20, and the clip circuit 511, and the control means is the system control circuit 50. It corresponds to.

  According to the first embodiment, even if the signal dynamic range of the dark image fluctuates by switching the circuit gain according to the ISO sensitivity, the offset addition means or the input range conversion means of the AD conversion means The dark level of the captured image and the saturation level of the highlight part can be set appropriately, so even if the exposure conditions are the same, if the ISO sensitivity is different, the dark part will rise and fall, or the saturation level of the highlight part will vary Therefore, it is possible to obtain a coherent captured image without depending on the difference in ISO sensitivity.

  Further, according to the second embodiment, by switching the circuit gain according to the ISO sensitivity, even if the pixel defect noise exceeds the signal dynamic range of the dark image, the number of defect correction is switched by the defect correction means. Therefore, it is possible to solve the problem that scratches remain without being corrected for each ISO sensitivity. Therefore, it is possible to obtain a high-quality captured image having no defect regardless of differences in ISO sensitivity.

  Further, according to the third embodiment, when the actual captured image data has an excessive amplitude due to scratch noise or the like, or when the gain is increased by switching the circuit gain according to the ISO sensitivity, the actual captured image data has an excessive amplitude. Even in such a case, the signal level of the actual captured image can be set to an appropriate signal level that does not saturate the circuit by the clip level switching means, so that the signal delay due to scratch noise and the slew rate characteristic at the time of circuit saturation at high ISO sensitivity As a result, the subsequent adjacent pixel signal is not disturbed, so that it is possible to solve the problem that the flaws remain without being corrected, and further, hue distortion in the high luminance part and color jump in the high chroma part. It is possible to obtain a stable captured image without any problem.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

12: Shutter 14: Imaging unit 16: A / D conversion unit 18: Timing generation circuit 20: Image processing circuit 22: Memory control circuit 24: Image display memory 26: D / A converter 28: Image display unit 30: Memory 32 : Image compression / decompression circuit 40: Shutter control means 42: Distance measurement means 46: Photometry means 48: Flash 50: System control circuit 52: Memory 54: Display unit 56: Non-volatile memory 60: Mode dial switch 62: Shutter switch SW1
64: Shutter switch SW2
66: Playback switch 68: Single / continuous shooting switch 70: Operation unit 72: Power switch 74: Real time clock 80: Power control means 82: Connector 84: Connector 86: Power supply means 90: Interface 92: Connector 94: Interface 96: Connector 98: Recording medium attachment / detachment detection means 100: Image processing apparatus 104: Optical finder 106: Lens mount 110: Communication means 112: Connector (or antenna)
120: interface 122: connector 130: mirror 132: mirror 200: recording medium 202: recording unit 204: interface 206: connector 210: recording medium 212: recording unit 214: interface 216: connector 300: lens unit 306: lens mount 310: Shooting lens 312: Diaphragm 320: Interface 322: Connector 340: Exposure control means 342: Distance measurement means 344: Zoom control means 350: Lens system control circuit 400: Image sensor 401: Amplifier 402: Offset adder 405: AD converter 408: D / A converter 500: Image sensor 501: Amplifier 502: Offset adder 505: AD converter 508: D / A converter

Claims (3)

Imaging means for converting an optical image of a subject into an image signal;
Clip means for limiting the output amplitude of the imaging means;
Amplifying means for amplifying the image signal whose amplitude is limited by the clip means;
Offset addition means for adding an offset voltage to the image signal amplified by the amplification means;
AD conversion means for converting the image signal amplified by the amplification means and added with the offset voltage by the offset addition means into a digital signal;
An offset voltage setting means for setting an offset voltage according to sensitivity in the offset addition means so that a noise signal included in the image signal amplified by the amplification means falls within an input range of the AD conversion means;
Have
An image processing apparatus, wherein a clip level corresponding to the sensitivity is set in the clip unit based on an external control signal, and a gain corresponding to the sensitivity is set in the amplification unit. The image processing apparatus according to claim 1 , further comprising an input range setting unit that sets an input range of the AD conversion unit according to the sensitivity. The sensitivity, the image processing apparatus according to claim 1 or 2 including the ISO sensitivity.

Images