KR101128227B1 - Imaging device calibration methods and imaging device calibration instruments - Google Patents

Abstract

An imaging device calibration method, an imaging device calibration device, and an imaging device are disclosed. According to one embodiment of the invention, the imaging device calibration method comprises the steps of emitting light for use in calibration of the imaging device 14, providing the emission characteristics of the light, and an image of the imaging device 14. Sensing the light using a sensor 46, generating sensor data indicating what has been detected using the image sensor 46, and generating the sensor data and the imaging device 14 Determining at least one optical characteristic of the imaging device 14 using the emission characteristic for use in calibration, wherein the at least one optical characteristic is applied to the imaging device 14 used to sense the light. Corresponds.

Description

Imaging Device Calibration Method and Imaging Device Calibration Device {IMAGING DEVICE CALIBRATION METHODS AND IMAGING DEVICE CALIBRATION INSTRUMENTS}

FIELD OF THE INVENTION The present invention relates to imaging device calibration methods, imaging device calibration devices, imaging devices and articles of manufacture.

Shooting systems of various designs have been used extensively to generate images. Exemplary imaging systems include copiers, scanners, cameras and recent digital cameras, and other devices capable of generating images. Color imaging systems have also been significantly improved and are becoming increasingly popular. The color imaging system may also be calibrated to increase the accuracy of various image processing algorithms (eg, light estimation, color correction, etc.) and to increase the color accuracy of the final reproduction.

For example, even identically configured imaging systems may differ from one another due to product tolerances or design changes. Referring to FIG. 1, there is shown a graph of relative responsiveness versus wavelength for two hundred digital cameras corresponding to the same product. FIG. 1 is a graph showing variation in responsiveness of blue, green, and red sensors of sampled cameras in each band (4, 6, and 8). Although the cameras are composed of identical components in structure, the illustrated band has a width that illustrates the magnitude of the deviation between the respective cameras.

One color correction technique uses reflective charts. Reflection charts can be used to quickly calibrate the camera and are relatively inexpensive. However, the calibration performed using the reflection chart may not be accurate enough for use with the camera. Monochromators, on the other hand, can very accurately calibrate color imaging systems, including cameras. However, calibration procedures using monochromators are relatively long to complete and expensive.

At least some features of the invention relate to improved calibration systems and methods.

According to a feature of the invention, an exemplary imaging device calibration method, imaging device calibration device, imaging device and article of manufacture are disclosed.

According to an embodiment of the present invention, a photographing apparatus calibration method includes the steps of emitting light for use in calibration of a photographing apparatus, providing an emission characteristic of the light, and using the image sensor of the photographing apparatus. Detecting the sensor; generating sensor data indicating what is detected using the image sensor; and using the generated sensor data and the emission characteristic for use in calibration of the imaging device. Determining at least one optical characteristic, the at least one optical characteristic corresponding to the imaging device used to sense the light.

According to another embodiment of the present invention, an imaging device calibration device is configured to provide a light source configured to emit light having a plurality of different spectral power distributions, and the light to an imaging device to be calibrated using the imaging device calibration device. An optical interface and processing circuitry for automatically controlling the emission of light from the light source to calibrate the imaging device.

Other embodiments are described as will become apparent from the following description.

1 is a graph of the responsiveness of a sampled imaging system.

2 is an explanatory diagram of an exemplary calibration device and imaging device according to an embodiment of the present invention.

3 is a functional block diagram of a circuit of a calibration apparatus according to an embodiment of the present invention.

4 is a functional block diagram of a circuit of a photographing apparatus according to an embodiment of the present invention.

5 is an explanatory diagram of an optical interface of a calibration device according to an embodiment of the present invention.

6 is a graph of wavelength versus wavelength of light emitted from an optical interface according to an embodiment of the present invention.

7 is a flowchart illustrating an exemplary photographing apparatus calibration method according to an embodiment of the present invention.

8A is a flowchart illustrating exemplary data collection in accordance with an embodiment of the present invention.

8 (b) is a flowchart illustrating exemplary data collection according to another embodiment of the present invention.

9 is a flowchart illustrating exemplary data processing in accordance with an embodiment of the present invention.

10 is a graph comparing exemplary calibration techniques.

11 is a graph comparing the estimated responsiveness and the relative responsiveness calibrated using the Macbeth chart calibration technique.

12 is a graph comparing the estimated relative responsiveness and the relative responsiveness corrected using the Macbeth DC chart.

13 is a graph comparing the estimated relative responsiveness and the relative responsiveness calibrated using the radioactive calibration device according to an embodiment of the present invention.

At least some features of the present invention provide an apparatus and method that allow for quick and accurate calibration of an imaging device. In one embodiment of the invention, optical characteristics such as the reactivity function and / or the transduction function of the imaging device may be measured to determine how the associated imaging device responds to the input optical signal. The optical properties thus determined can be used to calibrate each imaging device. According to an exemplary embodiment, the radiant light source disposed opposite the reflective configuration is used to determine the optical properties, allowing quick and relatively inexpensive calibration of the imaging device (eg on a production line) in real time.

2, an imaging system 10 according to an embodiment of the present invention is shown. The illustrated imaging system 10 includes an imaging device calibration device 12 and an imaging device 14. In one embodiment where the one or more light sources of the imaging device calibration device 12 determine the calibration data and emit light used to calibrate the imaging device 14, the imaging device calibration device 12 may be referred to as a radiation calibration device. It may be.

In at least one embodiment, the calibration device 12 is used to provide calibration data that may be used to calibrate the imaging device 14. In at least some embodiments described herein, the calibration device 12 may operate in conjunction with the imaging device 14 to provide calibration data. The calibration data includes optical properties such as responsiveness and / or conversion function of each imaging device 14 in an exemplary embodiment. Calibration data can be used to calibrate the individual devices 14 used to obtain calibration data. For example, the image processing algorithm of the photographing apparatus 14 can be tailored to improve the photographing operation of the algorithm including the performance of the photographing apparatus 14 to produce a satisfactory and faithful image of the captured scene.

The photographing device 14 includes a color digital camera in the illustrated system. Other configurations of the imaging device 14 configured to generate image data in response to the received image are possible (eg, scanners, color copiers, color multifunction peripherals, etc.).

Referring back to the calibration device 12, an exemplary embodiment includes a light source 20, a light randimizer 22, and an optical diffuser 24. For ease of explanation, exemplary components 20, 22, 24 are shown in exploded view. In a typical embodiment of the calibration device 12, the components 20, 22, 24 are sealed against each other to prevent ambient light from being introduced into the calibration device 12 from each other. Processing circuitry of the calibration device 12 may be provided to control the calibration operation as described below with respect to the example circuit of FIG. 3.

The light source 20 may be implemented in other configurations in other embodiments of the calibration device 12. In addition, the light source 20 may be controlled to emit different light simultaneously and / or continuously in other embodiments. Different light includes light with different emission characteristics, such as different wavelengths, intensity of light or spectral power distribution.

For example, the configuration of the light source 20 has a plurality of zones 26 configured to emit light having different wavelengths and / or intensity of light with different zones 26. Thus, in the embodiment of the calibration device 12 of FIG. 2, the light of at least some zones 26 may be spatially and spectrally separated from the light of the other zones 26. In some embodiments, light of different wavelengths and / or intensities may be emitted simultaneously. In other embodiments described below, light of different wavelengths and / or intensities may be emitted continuously.

Individual zones 26 may include one or more light emitting devices (not shown). Exemplary light emitting devices include narrowband devices with increased accuracy compared to wideband reflective patches. The light emitting element in zone 26 includes light emitting diodes (LEDs) and a laser in an exemplary embodiment. Other configurations of light emitting devices in zone 26 may be used. In one embodiment, the individual zones 26 comprise 3 × 3 light emitting elements configured to emit light of the same wavelength and intensity.

In an exemplary embodiment, the light randomizer 22 includes a plurality of hollow tubes, each corresponding to an individual zone 26 of the light source 20. The light randomizer 22 is configured to provide light diffuser 24 with substantially uniform light for each zone 26. The inner surface of the tube of the light randomizer may be a relatively bright white matte surface. Other configurations of the optical randomizer 22 are possible. For example, the light randomizer 22 may include a single hollow tube in at least one embodiment of the apparatus 12 having only one light emitting zone as described below.

The light diffuser 24 provides substantially uniform light for each zone 26 (and individual zones 28 of the optical interface 27 described below) to the imaging device 14 for use in the calibration operation. And an optical interface 27 configured to provide. Other configurations of the optical interface 27 except for the illustrated light diffuser 24 may be used to output light to the imaging device 14. Exemplary light diffuser 24 comprises a translucent acrylic material. The exemplary light diffuser 24 shown is configured to output light corresponding to the light emitted by the light source 20. For example, the exemplary optical interface 27 includes a plurality of zones 28 corresponding to individual zones 26 of the light source 20. In other embodiments, more or fewer zones 28 may be provided corresponding to the number of zones 26 of the light source 20. In at least one embodiment, the light randomizer 22 and the light diffuser 24 provide different light corresponding to the individual zones 28, with each light having a respective zone 28 for each zone 28. Substantially uniform throughout the region. In other possible embodiments, other light diffusers may be implemented with an intermediate light source 20 and a light randomizer 22 or may be implemented within the light randomizer 22.

In one embodiment, the light randomizer 22 comprises a substantially rectangular aluminum tube corresponding to the zone 26 of the light source 20. The tube has a length of 2.5 inches and dimensions of 1 inch by 1 inch square between the light source 20 and the light interface 27. The interior surface of the tube may be coated with a white coating such as OP.DI.MA material having a part number of ODM01-F01 available from Gigahertz-Optik. The light diffuser 24 may comprise a plurality of pieces of white translucent acrylic material having a 020-4 part number available from Cyro Corporation, each piece having a thickness of 1/8 inch. Other configurations or embodiments are possible.

Referring to FIG. 3, an exemplary circuit 30 of the calibration device 12 is shown. The circuit 30 shown includes a communication interface 32, a processing circuit 34, a storage circuit 36, a light source 20 and an optical sensor 38. In other embodiments, other circuit components may be provided.

The communication interface 32 is configured to establish communication of the calibration device 12 with respect to the external device. Exemplary configurations of the communication interface 32 include USB ports, serial or parallel connections, IR interfaces, wireless interfaces, or any other configuration capable of unidirectional or bidirectional communication. Any suitable data can be communicated using communication interface 32. For example, as described below, communication interface 32 may be used to deliver one or more emission characteristics of light source 20 and / or one or more determined optical characteristics of each imaging device 14 to be calibrated. Can be.

In one embodiment, processing circuit 34 may include circuitry configured to implement a desired program. For example, processing circuit 34 may be implemented in a processor or other structure capable of executing executable instructions, such as software and / or firmware instructions. Other example embodiments of processing circuits include hardware logic, PGAs, FPGAs, ASICs, state machines, and / or other structures. An example of such a circuit 34 is merely illustrative and other configurations are possible.

Processing circuit 34 may be used to control the operation of calibration device 12. In one embodiment, the processing circuit 34 automatically controls the timing of the emission of light from the device 12 (e.g., simultaneously and / or successively from the device 12 with light of different wavelengths and / or intensities). To control the timing of emission. In one embodiment, the processing circuit 34 may automatically control the timing and emission of light without user intervention.

Storage circuitry 36 is configured to store electronic data and / or programs, such as executable instructions (eg, software and / or firmware), calibration data, or other digital information, and may include processor usable media. Can be. In addition to the calibration data described above, additional exemplary calibration data may include one or more emission characteristics of light emitted using the optical interface 27 of the calibration device 12. As disclosed below, exemplary emission characteristics include a spectral power distribution (SPD) of light emitted at optical interface 27 in accordance with one embodiment of the present invention. The spectral power distribution includes emission characteristics including the wavelength of emitted light and the intensity of light associated with each individual wavelength of light.

Processor usable media includes, in an exemplary embodiment, any article of manufacture capable of containing, storing, or maintaining programs, data, and / or digital information for use by or in connection with an instruction execution system comprising processing circuitry. do. For example, example processor usable media may include any of physical media such as electronic media, magnetic media, optical media, electromagnetic media, infrared media, or semiconductor media. Some other specific examples of processor available media include portable magnetic computer diskettes, such as floppy diskettes, zip disks, hard drives, random access memory, read only memory, flash memory, cache memory and / or programs, data or other digital information. It is not limited to other configurations that can be stored.

The light source 20 may be configured in an exemplary arrangement as described above. For example, the light source 20 may be configured to emit light of different wavelengths and / or intensities in one embodiment. Different wavelengths and / or intensities of light may be defined by multiple zones 26 as described above. In another embodiment, the light source 20 is configured to emit light that is substantially constant in wavelength and / or intensity. Multiple spatially separated filters disposed downstream of the light source 20 and corresponding to the zone 26 may be used to provide light of all wavelengths and / or intensities as required, as described below. In other embodiments, the light source 20 may be configured to emit different light in turn using a single zone. Other arrangements are possible.

The light sensor 38 is optically coupled to the light source 20 and configured to receive the emitted light. In one embodiment, the optical sensor 38 is implemented as a photodiode, although other configurations are possible. In some embodiments one or more optical sensors 38 may be disposed within the optical randomizer 24. (For example, in the exemplary configuration described herein, one optical sensor 38 may be disposed within the optical randomizer 22 implemented as a single hollow tube). In other arrangements with multiple zones 26, the optical sensor 38 may be optically coupled to the zone 26 via a suitable light pipe (not shown) or other configuration and may emit light having different wavelengths and / or intensities. It may correspond to.

The light sensor 38 is configured to monitor the light emitted for calibration purposes of the calibration device 12 in one embodiment. For example, at least some configuration of the light source 20 may provide light that drifts over time in wavelength and / or intensity. The light sensor 38 may be used to monitor light and may be used to indicate to the user that the device 12 has failed to calibrate and that service is required. For example, if the intensities of light with different wavelengths are different from each other, the calibration device 12 may be considered to be unable to calibrate. Exemplary recalibration of the calibration device 12 may include re-determining the emission characteristics (eg, spectral power distribution) of the light emitted at the optical interface 27.

4, the imaging device 14 is illustrated as a digital camera in an exemplary configuration. As mentioned above, the imaging device 14 may be implemented to generate an image from the scene or the received light in other configurations. In the illustrated configuration, the imaging device includes a processing circuit 40, a storage circuit 42, a strobe 44, an image sensor 46, a filter 48, an optical device 50, and a communication interface 52. .

In one embodiment, processing circuit 40 may be implemented similar to processing circuit 34 described above and may include circuitry configured to implement desired programming. Other exemplary embodiments of the processing circuit may include the operation of the imaging device 14 (eg, control strobe 44, optical device 50, information collection and storage, processing of image data, communication with external devices, and the like. Different and / or alternative hardware to control other required operations). An example of such a processing circuit 40 is merely illustrative and other configurations are possible.

The storage circuit 42 is configured to store electronic data (eg image data) and / or programs (eg software and / or firmware), or other digital information, such as executable instructions and at least one embodiment. It may include a processor usable medium similar to the storage circuit 36 described above.

Strobe 44 includes a light source configured to provide light for use in imaging operations. Processing circuit 40 controls the operation of strobe 44 in the described embodiment. Strobe 44 may be disabled or may be used alone or in combination with other external light sources (not shown).

Image sensor 46 is configured to provide raw image data of a plurality of raw images. Unprocessed image data includes digital data corresponding to a plurality of pixels of an unprocessed image formed by image sensor 46. For example, an unprocessed image includes bytes corresponding to red, green, and blue colors in each pixel in an exemplary RGB application. Other embodiments may use or provide other color information. Image sensor 46 may include a number of photosensitive elements, such as photodiodes, that correspond to pixels and provide raw digital data available for generating an image. For example, image sensor 46 may include a raster of photosensitive elements (or referred to as pixels) arranged in a 1600 x 1280 matrix in one possible configuration. Other raster configurations are possible. Photosensitive devices include charge coupled devices (CCDs) or CMOS devices in an exemplary configuration. In one particular embodiment, image sensor 46 may utilize X3 technology in a sensor array available from Foveon, Inc.

The filter 48 is provided upstream of the image sensor 46 to perform the necessary filtering on the light received by the image sensor 46 before being sensed by the image sensor 46. For example, in one embodiment, filter 48 may remove infrared light received by imaging device 14.

Optical device 50 includes an appropriate lens and aperture configured to focus and direct the given light to produce an image using image sensor 46. In one embodiment, a suitable motor (not shown) may be controlled by the processing circuit 40 to perform the desired manipulation of the optical device 50.

The communication interface 52 is configured to establish communication with the photographing device 14 with respect to the external device (eg, the calibration device 12). Exemplary configurations of the communication interface 52 include a USB port, a serial or parallel connection, an IR interface, a wireless interface, or any other arrangement capable of unidirectional or bidirectional communication. The communication interface 52 may be configured to be connected to the communication interface 32 of the calibration device 12 or other external device to exchange any suitable data. For example, communication interface 52 may be used to receive one or more emission characteristics of light source 20 and / or one or more determined optical characteristics of imaging device 14. In addition, the communication interface 52 may output sensor data generated by the image sensor 46, and as described below, an image processing operation including an operation of determining optical characteristics of the imaging device 14 It can be used to implement

5, an exemplary configuration of optical interface 27 is shown. The illustrated optical interface 27 corresponds to the embodiment of the calibration device 12 shown in FIG. 2 and includes a plurality of zones 28 of light of different wavelengths and / or intensities.

In the illustrated configuration, the optical interface 27 includes a plurality of colored row 60 zones and a single white row 62 zone. In other embodiments of the optical interface 27 more or less zones with different wavelengths and / or intensities may be provided.

Row 60 of colored zones provides multiple zones 28 of light of different wavelengths. For example, in the illustrated embodiment, row 60 continuously increases in wavelength in increments of 25 nm from ultraviolet (375 nm) to infrared (725 nm), providing spectrally spatially separated light. Zone 28. In the illustrated embodiment, row 62 includes multiple zones W1-W5 with the same relative spectral power distribution. The relative light intensity of the white patch can be 0.01, 0.03, 0.10, 0.30, and 1 for every zone W1-W5.

According to the exemplary embodiment of FIG. 5, the number of light emitting devices and / or driving current of the light emitting devices can vary between each zone 28 to provide a desired spectral power distribution of the emitted light. Other configurations are possible in other embodiments.

In one embodiment, the zones 28 of FIG. 5 may be numbered in order from 1 to 15 from left to right for each row starting from the top row to the bottom row. Exemplary light emitting devices may include LEDs available from Roither Lasertechnik and have the following part numbers for each zone 28: (1) 380D30, (5) HUBG-5102L, (13) ELD-670- 534, (14) ELD-700-534, and (15) ELD-720-534. The remaining exemplary light emitting devices can include LEDs available from Opto, USA, with the following part numbers for each zone 28: (2) L513SUV, (3) L513SBC-430NM, (4) L513NBC , (6) L513NBGC, (7) L513NPGC, (8) L513UGC, (9) L513NYC-E, (10) L513UOC, (11) L513NEC, (12) L513TURC and (W1-W5) L513NWC.

In this embodiment, the drive current may be constant (eg, 18-20 mA) per light emitting device in all of the zones 28 in row 60. The number of light emitting elements per zone 28 is (1) 4, (2) 1, (3) 14, (4) 2, (5) 4, (6) 3, (7) 1, (8) 27, It changes according to (9) 3, (10) 2, (11) 1, (12) 2, (13) 2, (14) 2, and (15) 1. The number of light emitting elements in the individual zones 28 in row 62 may be the same (eg, four), and the following exemplary drive currents are the individual zones W1-W5 of zones 28. Every 0.2, 0.6, 2,6 and 20 mA. The above examples are illustrative and other configurations or modifications are possible.

As will be described in detail below, by using the optical interface 27 of FIG. 5 that includes a region 28 of varying wavelengths and / or intensities, the light emitted from the optical interface 27 using the imaging device 14. Simultaneous determination of the reactivity and conversion function of the imaging device 14 is made possible by light, for example, by simple exposure of the imaging device 14. Other configurations of the optical interface 27 (eg, to provide an optical interface in which only wavelengths or intensities vary between the zones 26, and a single emission that continuously emits light of the same wavelength and / or intensity Providing a zone-only optical interface, etc.) is possible as disclosed herein.

Providing light of different wavelengths by the calibration device 12 may be used to determine the responsiveness function of the imaging device 14. In the embodiment of the optical interface 27 described in FIG. 5, the area 26 of the rows 60 spatially separated by spectra simultaneously emits light in multiple zones 26 in the row 60 to expose one time. By this, the reactivity function by the imaging device 14 can be determined.

Referring to FIG. 6, the emission of light through the optical interface 27 (ie, the light reception by the imaging device 14) may be optimized to facilitate determination of the responsiveness function of the imaging device 14 to be calibrated. The graph of FIG. 6 illustrates the spectral power distribution of light emitted by light source 20 and provided to zone 28 of optical interface 27 that facilitates reactivity analysis of the imaging device. The spectral power distribution includes exemplary luminance values for the zone 28 of the optical interface 27 shown in FIG. 5 with increasing wavelength from left to right along the x-axis.

As mentioned above, the number of light emitting elements of the light source 20 can be varied to provide different light intensities for each zone 26. In other embodiments, the number of light emitting devices may be the same for each zone 26 and the drive current of the light emitting devices in each zone 26 may be varied to provide the desired light intensity. Other arrangements may be used that provide the desired spectral power distribution. In one embodiment, the intensity of light approximating the exemplary spectral power distribution shown in FIG. 6 may be selected during calibration of the calibration device 12 itself. Once the appropriate drive current (or other configuration parameter) of the light emitting device in each zone 26 is determined, the device 12 can be calibrated to drive the light emitting device using the determined drive current or the determined parameter. In one embodiment, the light emitting elements in each zone 26 may be driven using the same drive current, but the drive currents used to drive the light emitting elements in different zones 26 may be different. As mentioned above, other configurations may be used than in varying the number and / or drive current of the light emitting elements in each zone 26.

In addition, the spectral power distribution of the light emitted from the optical interface 27 using the drive current can be determined following calibration of the device 12. In one embodiment, the spectral power distribution of the light emitted at the optical interface 27 can be measured using a spectral radiometer. The measured spectral power distribution of the calibration device 12 is stored as the emission characteristic of the calibration device 12 using the storage circuit 36 or other suitable circuitry to be used continuously during the calibration operation of the one or more imaging devices 14. Can be. The new drive current and / or spectral power distribution may be determined during the recalibration of the device 12.

Emission characteristics may also be provided and stored for each zone 28 of the row 62. As mentioned previously, at least some zones 28 may be configured to vary the intensity of light of light of a given wavelength (eg, zones of row 62). Data relating to the intensity of light corresponding to zone 28 may be stored as emission characteristics for later use in calibration of one or more imaging devices 14. Light intensity data may also be extracted from the spectral power distribution of the light emitted in zone 28 in row 62.

Referring to FIG. 7, an exemplary method for performing calibration of the imaging device 14 using the calibration device 12 is shown. Other methods may include more steps, fewer steps, or other steps.

In step S1, an embodiment of the calibration device 12 having a light source is provided with at least one emission characteristic of the light emitted from the light source.

In step S2, the imaging device 14 to be calibrated is aligned with the calibration device 12.

In step S3, the image sensor 46 of the photographing apparatus 14 is exposed to light emitted from the light source.

In step S4, the image sensor 46 senses light and generates sensor data indicating what is detected by the image sensor 46.

In step S5, the appropriate processing circuit uses the emission characteristics and the sensor data to determine the optical characteristics of the imaging device 14. The optical characteristic can be used to calibrate the imaging device 14. The example method of FIG. 7 can be repeated for another imaging device 14.

The flowchart of FIG. 8A shows an exemplary method for collecting information during calibration of an associated imaging device 14 using the calibration device 12 described with reference to FIG. 2.

In step S10, the imaging device to be calibrated is aligned to receive light emitted from the optical interface of the calibration device 12. Once aligned, the light source 20 of the calibration device 12 is controlled to emit light at the zone 28 of the optical interface 27. The imaging device 14 focuses the optical interface 27 and exposes the image sensor 46 to the light at the calibration device 12 to receive the light emitted from the optical interface 27 (eg, to take a picture). It is configured to

In step S12, sensor data is generated by the image sensor 46 in accordance with the exposure in step S10. In one embodiment, the individual pixels of image sensor 46 are configured to provide sensor data consisting of RGB values. The pixel position of the image sensor 46 may correspond to the region 28 of the optical interface 27. Thus, the RGB values from the individual pixels corresponding to the individual zones 28 may be converted to a single average RGB value per individual zone 28 using processing circuits 34 and 40 or other desired circuitry in one embodiment. It can also be averaged to provide. According to one embodiment, the sensor data including the average RGB value can be used for calibration of the imaging device 14 as described below.

The information collection operation is described below for another embodiment of the calibration device 12. The calibration device 12 according to the present embodiment includes an optical interface having a single zone (not shown) for outputting light for calibration of the imaging device 14. For example, as described above, as opposed to the arrangement of light emitting devices having different wavelengths and / or intensities depending on the zones 26, light emitting devices of light sources having different wavelengths or intensities are distributed around the entire area of the optical interface zone.

In one embodiment, it is desirable for the light emitting element of the light source to provide a substantially uniform light distribution over the entire area of the optical interface zone. In one possible embodiment, light emitting devices having 20 different wavelengths or intensities may be arranged in rows and columns adjacent to each other in turn to emit substantially uniform light at that wavelength or intensity over the entire region of the optical interface. . Other distribution patterns of light emitting devices are also possible.

In one embodiment, only light emitting elements of a common wavelength or intensity can be controlled to emit light at a particular point in time. According to this embodiment, the light emitting element of the first wavelength light can be controlled to emit substantially uniform light over the entire area of the zone. Thereafter, the light emitting elements of the remaining wavelengths may be sequentially controlled to emit light of each wavelength in turn, providing a temporary and spectral distribution of the emitted light. If present, light emitting elements of different intensities for a given wavelength may in turn be individually configured to emit light, enabling the conversion calibration operation described in detail below. Thus, in one embodiment, light emitting elements of individual wavelengths or intensities may be configured to emit respective light. More specifically, light emitting devices having a common wavelength are controlled to emit light starting at 375 nm and reaching 725 nm, and then emitting light of the light emitting devices configured to emit light of a common wavelength and varying intensities of W1 to W5. do. The imaging device 14 may sense light of the emitted wavelengths 375 nm-725 nm and intensities W1-W5, respectively, in one embodiment. The sensor data for each wavelength and intensity of light is then provided by the imaging device 14.

Referring to FIG. 8B, an exemplary data collection operation according to the second embodiment described above having a single interface optical interface 27 emitting continuous different light is described.

In step S20, the calibration device is controlled to emit light of a single wavelength. The image sensor of the imaging device to be calibrated is exposed to the emitted light.

In step S22, the average RGB value of each wavelength can be determined from the pixel sensor data of the image sensor using the processing circuits 34 and 40 or other desired circuits.

The process then returns to step S20, whereby the calibration device controls the emission of light of the next wavelength, thereby enabling the generation of sensor data of each wavelength using the imaging device 14. The process of FIG. 8B may repeatedly provide sensor data having an average RGB value in the disclosed embodiment by a number of different wavelengths or intensities of emitted light using a calibration apparatus.

The above-described embodiment is provided to describe an exemplary data collection technique for performing a calibration operation of the imaging device. Other data collection methods and / or devices may be used in other embodiments.

Referring to Fig. 9, the acquired data is processed to determine the calibration data of the imaging device 14. Exemplary processing includes determining calibration data that includes the optical characteristics (eg, reactivity and / or conversion functions) of each imaging device 14 according to one embodiment. As mentioned above, the processing circuits 34 and 40 and / or other suitable processing circuitry may perform the information collection operation. Similarly, processing circuits 34 and 40 and / or other suitable processing circuits may be used to process the acquired data, for example as in FIG. In addition, data collection and processing may be performed by the same or different processing circuits.

In the exemplary process of FIG. 9, optical properties including the reactivity and conversion function of the imaging device 14 are determined. In other embodiments, either the reactivity or conversion function, and / or other characteristics of the imaging device may be determined. In addition, additional optical characteristics or other information for use in calibration of the imaging device 14 may be determined. For example, the reactivity and / or conversion function may be further processed by appropriate processing circuits 34, 40, or other processing circuitry (not shown). For example, a color correction matrix, an illumination estimation matrix and / or other information may be derived from the responsiveness and conversion function.

Steps S30-S34 describe an exemplary process of determining the reactivity function of the imaging device 14.

Steps S40-S44 describe an exemplary process of determining the conversion function of the photographing apparatus 14. Other processing in accordance with other arrangements (not shown) may be used.

In step S30, the sensor data obtained at the image sensor 46, including the average RGB value of the individual zones 28 of the row 60 in the illustrated embodiment, may define the matrix r.

In step S32, the emission characteristics, including the spectral power distributions SPDs of the zones 28 in the illustrated embodiment, may define the matrix S.

In step S34, the reactivity function (R) can be determined using the matrices (r, S), in which the formula R = pinv (S ^T ) r ^T in the disclosed embodiment.

The transformation function may be determined in conjunction with the determination of the reactivity function in the illustrated embodiment.

Referring to step S40, the sensor data from the image sensor 46, which includes the average RGB value of the individual zones 28 of the row 62 in the disclosed embodiment, may define a matrix r _w .

In step S42, the emission characteristic, including the spectral power distribution of zone 28 in the illustrated embodiment, may define a matrix S _w .

In step S44, the transform function g (x)-> g (1 ^T S _w ) = r _w in the illustrated embodiment can be solved using the matrix r _w .

The above-described method of FIG. 9 can be used to determine one or more optical characteristics of each imaging device 14 that provided each sensor data representing a circuit of the imaging device 14, so that the above-described process can be used to determine the angle to be calibrated. Executed for each imaging device 14 to determine the appropriate one or more optical characteristics of each imaging device 14. The above-described method of FIG. 9 is exemplary and other processes or methods may be used in other embodiments to determine the reactivity and / or conversion function or other optical properties of the imaging device 14.

Once determined, the optical characteristics can be used to calibrate each imaging device 14. For example, optical characteristics, including responsiveness and conversion functions, increase the accuracy of the image processing algorithms (e.g., illumination estimation and color correction) of each imaging device 14, increase the color accuracy of the final reproduction, and It can be used to increase the color accuracy of the reproduction.

As disclosed in one embodiment, the components of the exemplary device and / or method imaging device 14 (eg, sensor 46, filter 48, etc.) may be used to determine if there is a defect. have. For example, the ability of each imaging device 14 to remove infrared or other light can be monitored using the calibration device 12 configured to emit infrared or other light described above. For example, in response to light emitted from the optical interface 27 of the calibration device 12, sensor data generated by each imaging device 14 receives infrared or other light from which the filter 48 has been removed. If indicated to be included in the light, the filter of the imaging device 14 configured to remove any light (eg infrared light) may be identified as a defect.

In one embodiment, if the optical characteristic is determined using the calibration device 12 (or other external processing circuitry of the imaging device 14). The determined optical characteristic can be communicated to each imaging device 14 performing the appropriate calibration. Alternatively, the circuit 40 of the imaging device 14 may determine the optical characteristics of each device 14. In other embodiments, calibration may be performed outside of the imaging device 14 using the determined optical properties, and the corrected image processing algorithm may be provided to each imaging device 14 continuously. In yet another embodiment, the circuit 40 of the imaging device 14 is configured to utilize the determined (eg, internally or externally determined) optical properties such that calibration of the imaging device 14 can be performed internally. Can be. In summary, any suitable processing circuit may be configured to generate the optical properties of one or more respective imaging devices 14, and the same or different processing circuits may utilize one or more optical properties to calibrate the optical properties.

Referring to FIG. 10, there is shown a graph of the singular value distribution of another calibration method that includes an exemplary emission feature compared to the use of reflective patches (Macbeth and Macbeth DC) and monochrome devices.

The relatively high and constant singular value decomposition using the example radioactive calibration device 12 of FIG. 2 is similar to the results achieved using the monochromator, with Macbeth with a non-constant, relatively steeply decreasing slope in each curve. The results obtained through Macbeth and MacbethDC reflective patches are much exceeded. The accuracy of the calibration method depends on how the reflective patches or light emitting elements are correlated in spectra to each other. If there are many correlated patches or light emitting elements, less accurate calibration is required. This is because the calibration technique reverses the image shaping equations that calculate the camera responsiveness function. When the spectrum or correlated patch or light emitting element is inverted, a noise estimate of the camera responsiveness function is produced. The reflective function of the patch or the singular value of the spectral power distribution of the light emitting device indicates the accuracy of a given method. If the singular value is greater than 0.01 (less can be considered too much noise), the accuracy of the method is high (see FIG. 10). Basically, the number of singular values represents the number of patch colors or light emitting elements that affect the calibration results.

11 through 13, the example radiation calibration apparatus 12 of FIG. 2 for a Macbeth reflective patch (FIG. 11), a Macbeth DC reflective patch (FIG. 12) and a D1 digital camera available from Nikon. Exemplary relative responsiveness determined using (FIG. 13) is illustrated individually in a graph calibrated using a monochromator. The calibration device 12 of FIG. 2 increases the accuracy of determining the relative responsiveness of a given imaging device 14 compared to the use of reflective patches (eg, Macbeth and MacbethDC).

Table 1 compares the calibration procedure using the reflection chart, calibration device 12 and monochromator of FIG. 2. The calibration device 12 of FIG. 2 provides the given imaging device 14 with the shortest calibration time (ie, slightly shorter than the reflection chart). No uniformity of the external light source is required as in a shorter time than the reflection chart and the monochromator (ie, the color can be temporarily corrected to space in the composition of FIG. 2 instead of as temporarily as the monochromator). Since the external light source of the light does not need to be uniform (eg, the exemplary device 12 emits the required light itself), the calibration device 12 has the shortest calibration time of the compared device.

Table 2 compares the approximate costs of the devices configured to perform the three calibration methods described above.

Table 3 compares the number of singular values of the three methods and devices, including the calibration device of FIG. Other embodiments of the calibration device 12 may include more or fewer wavelengths and / or intensities of light as desired. For example, the embodiment of the device 12 described above includes 20 types of different light. In other embodiments, suitable numbers of other types of light (wavelength and / or intensity) may be used in succession, in multiple zones, or in accordance with other suitable schemes.

Because reflection charts have patch colors that are highly correlated with broadband, they are only used in approximately four methods that can be used for calibration. This is typically not suitable for the calibration of imaging device 14 including a camera. Monochromator devices, on the other hand, typically use narrowband light sources, leading to more than 50 calibration methods. Thus, the monochromator produces calibration results with increased accuracy, but the calibration time is relatively long and the cost is relatively expensive. The example calibration device 12 of FIG. 2 yields 15-20 associated methods, for example, more than the proper calibration results of a typical imaging device 14 (eg, a digital camera). However, it does not suffer the cost and long calibration time of the monochromator or use external lighting as used for reflective patches.

Accordingly, at least some features of the present invention allow for quick, accurate and relatively inexpensive determination and calibration of the reactivity and conversion functions of the imaging device 14, and in at least one embodiment for calibrating the imaging device on a manufacturing line. Can be used. As described above, the imaging device 14 using the same model or the same type of components may have different reactivity and conversion functions because of manufacturing variations in the sensor and / or color filter. The calibration device 12 described in the present invention may be used to determine the optical characteristics of the imaging device 14 and to calibrate the imaging device 14 before the imaging device 14 is sent to a customer or distributor. Relatively fast and accurate calibration can improve the overall color reproduction quality of the individually calibrated imaging device 14.

The calibration device 12 or the method disclosed herein may also be used by a professional or prosumer photographer for calibration of the high performance imaging device 14. It is believed that such correction will improve the overall color reproduction quality of the resulting image produced by such a calibrated imaging device 14. At least some such correction features may focus on the professional market, where correction features typically use image data that is not processed by the imaging device 14, and the image data that is not processed is developed for this market. This is because it is provided by the imaging device 14.

The protection sought by the present invention is not limited to the embodiments presented by way of example only, but only by the scope of the appended claims.

Claims (10)

In the imaging device calibration method, Emitting light for use in calibration of the imaging device 14, Providing emission characteristics of the light; Sensing the light using the image sensor 46 of the imaging device 14, Generating sensor data indicative of sensing using the image sensor 46; Determining at least one optical characteristic of the imaging device 14 using the generated sensor data and the emission characteristic for use in calibration of the imaging device 14, The at least one optical characteristic corresponds to the imaging device 14 used to sense the light. How to calibrate the shooting device. The method of claim 1, The at least one emission characteristic comprises a spectral power distribution of the light How to calibrate the shooting device. The method according to claim 1 or 2, Emitting the light comprises simultaneously emitting different light using a plurality of light emitting elements, Determining the optical characteristic comprises using the simultaneously emitted light to determine the at least one optical characteristic including reactivity and conversion How to calibrate the shooting device. The method according to claim 1 or 2, The determining of the optical characteristic is performed outside of the photographing apparatus 14, The method further comprises transferring the at least one optical characteristic to the imaging device 14. How to calibrate the shooting device. The method according to claim 1 or 2, Determining the optical characteristic includes determining using the imaging device 14 How to calibrate the shooting device. In the imaging device calibration instrument 12, A light source 20 configured to emit light having a plurality of different spectral power distributions, An optical interface 27 configured to provide the light to the imaging device to be calibrated using the imaging device calibration device 12; A processing circuit 34 configured to automatically control the emission of light from the light source 20 to calibrate the imaging device 14, A communication interface 32 for communicating data external to the imaging device calibration device 12 with respect to at least one emission characteristic of the emitted light to calibrate the imaging device 14. Shooting Device Calibration Device. The method of claim 6, The processing circuit 34 is configured to automatically control the emission of the light without user intervention. Shooting Device Calibration Device. 8. The method according to claim 6 or 7, The processing circuit 34 is configured to automatically control the timing of emission of the light from the light source 20. Shooting Device Calibration Device. 8. The method according to claim 6 or 7, The optical interface 27 includes a plurality of zones 28 having different wavelengths of light. Shooting Device Calibration Device. 8. The method according to claim 6 or 7, The optical interface 27 includes a plurality of zones 28 having the same wavelength of light and different light intensities. Shooting Device Calibration Device.

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