WO2002001850A1 - Dispositif de correction du gamma - Google Patents

Dispositif de correction du gamma Download PDF

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Publication number
WO2002001850A1
WO2002001850A1 PCT/JP2001/005562 JP0105562W WO0201850A1 WO 2002001850 A1 WO2002001850 A1 WO 2002001850A1 JP 0105562 W JP0105562 W JP 0105562W WO 0201850 A1 WO0201850 A1 WO 0201850A1
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Prior art keywords
gamma correction
value
correction value
gamma
stored
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Application number
PCT/JP2001/005562
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English (en)
Japanese (ja)
Inventor
Fumio Fujimura
Original Assignee
Matsushita Electric Industrial Co. Ltd.
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Filing date
Publication date
Application filed by Matsushita Electric Industrial Co. Ltd. filed Critical Matsushita Electric Industrial Co. Ltd.
Publication of WO2002001850A1 publication Critical patent/WO2002001850A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/407—Control or modification of tonal gradation or of extreme levels, e.g. background level
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T5/00—Image enhancement or restoration
    • G06T5/90—Dynamic range modification of images or parts thereof
    • G06T5/92—Dynamic range modification of images or parts thereof based on global image properties

Definitions

  • the present invention relates to a gamma correction device, and more particularly to gamma correction when an image scanner is used as an imaging device.
  • gamma correction is performed with a display device such as a monitor for displaying a captured image in order to maintain the linearity of an output signal with respect to an input signal.
  • Gamma correction is performed so that the characteristics become linear.
  • the gamma correction value for the input signal is calculated in advance, the gamma correction table is stored in ROM, and the address of ROM is referred to by the input signal. This can be realized by outputting the gamma correction data stored in the address as an output signal.
  • This gamma characteristic differs for each element of the image scanner.However, most image scanners perform gamma correction with only one gamma correction value, and color differences may occur in scanned images due to differences in gamma characteristics for each element. Image quality degradation such as streaks and streaks has occurred.
  • shading correction has been performed to suppress the variation in the element characteristics.
  • variations in element characteristics can be suppressed by correcting the black level and white level of each element.
  • the image quality was degraded due to the characteristic variation of “1”.
  • the purpose of the method is not to reduce the capacity of the gamma correction table for each element, but the device has several types of gamma correction tables.
  • To reduce the size of the collection table there is, for example, a digital gamma correction method and an apparatus thereof disclosed in Japanese Patent Application Laid-Open No. 8-195895.
  • FIG. 28 is a block diagram showing a conventional device for performing gamma correction.
  • 280 1 is an input terminal to which data is input
  • 280 2 is an input terminal 280 1
  • the selection section, 2803 is a gamma characteristic correction section that processes the signal output from the input selection section 2802
  • 284 is the characteristic selection section
  • 2805 is the characteristic selection section 28004
  • the microprocessor 28006 that receives the output of the microprocessor 280 is a data storage unit that supplies data to the microprocessor 285.
  • Reference numerals 280 (1) to 280 (M) denote memories constituting the data storage unit 2806.
  • the data storage unit 2806 stores data of M gamma correction tables, and each gamma correction table stores one reference data and a plurality of difference values. Based on the gamma characteristic selection signal supplied from the characteristic selection unit 284, the microprocessor 285 selects reference data stored from the memory corresponding to the gamma characteristic selected from the data storage unit 286. , And a plurality of difference values are read.
  • the microphone processor 28005 restores the gamma characteristic table using the read reference data and a plurality of difference values, and the gamma characteristic correction section 2803 uses a look-up table form. save. Then, the gamma characteristic correction unit 2803 performs gamma correction by using the input video data as address data and outputting a gamma correction value corresponding to the address.
  • the storage capacity is reduced by storing the reference data and a plurality of difference values.
  • the data storage unit 286 stores the gamma correction value G (1) corresponding to the input data X (1) as the reference data, and stores the remaining data.
  • the gamma correction value is
  • the gamma correction data can be restored by integrating the k-th difference value from the reference data.
  • the storage capacity can be reduced.
  • the conventional gamma correction device has a problem that the storage capacity does not decrease in the low gradation region, that is, in the region where the value of the input data is small, because the amount of change in the gamma characteristic is large.
  • the gamma correction data of a certain element has the gamma correction characteristic as shown in FIG. 30 (a)
  • the difference value corresponding to input data 3 is 1 2 and the difference value corresponding to input data 4 is 6.
  • the capacity for storing the difference value must be such that the maximum value of the difference value can be stored. In this case, a storage capacity of 5 bits is required to store 17. In this way, when the input data is small, the difference value does not decrease due to the gamma characteristic of the element, and the storage capacity of the gamma correction value cannot be reduced.
  • the conventional gamma correction device does not perform gamma correction with a different gamma correction value for each element, but performs gamma correction with the same gamma correction value for each element.
  • gamma correction could be performed by preparing multiple gamma correction tables, different gamma corrections could not be performed for each element.
  • the conventional gamma correction device is configured as described above, and the same gamma correction table is prepared for each element, and the gamma correction is performed, so that the image quality deterioration cannot be sufficiently prevented.
  • the difference value does not become small due to the gamma characteristic of the element, and the storage capacity of the gamma correction value cannot be reduced efficiently.
  • the present invention has been made in order to solve the above problems, and has a high precision
  • 'To provide a gamma correction device capable of performing correction.
  • the storage capacity of the gamma correction value is small. It is an object of the present invention to provide a gamma correction device capable of: Disclosure of the invention
  • a gamma correction device is a gamma correction device for correcting gamma characteristics of a plurality of image sensors, wherein a gamma correction value storage for storing gamma correction values of all image sensors. Means, a gamma correction value selecting means for selecting a gamma correction value for each element from the gamma correction value storage means, and a gamma correction value selected by the gamma correction value selecting means for each element.
  • Gamma correction means for individually performing gamma correction.
  • the gamma correction device is the gamma correction device according to claim 1, wherein the gamma correction value storage means includes a discrete input device that reads a predetermined image. A gamma correction value for each element is stored, and an interpolation process is performed from an input value of a predetermined image and a gamma correction value stored in the gamma correction value storage means to calculate a gamma correction value for each element. It has gamma correction value interpolation means.
  • the gamma correction device is the gamma correction device according to claim 1, wherein the gamma correction value storage means is a discrete gamma correction device that reads a predetermined image.
  • the gamma correction value for an appropriate input value the gamma correction value for a low gradation part is stored more.
  • a gamma correction device is a gamma correction device for capturing gamma characteristics of a plurality of imaging devices, wherein the gamma correction value of the reference device and each of the devices that are positionally adjacent to each other.
  • Gamma correction value storage means for storing the difference value of the gamma correction values of the above with a predetermined storage capacity, the reference element uses the stored gamma correction value, and the other elements use the gamma correction of the reference element.
  • Gamma correction value calculation means for calculating a gamma correction value for each element by integrating the difference value of the element existing up to the position of the element with the value, and a gamma correction value calculated from the above calculated gamma correction value for each element.
  • gamma correction means for performing gamma correction is provided.
  • the gamma correction device is the gamma correction device according to claim 4, wherein the gamma correction value storage means includes a predetermined image. A gamma correction value corresponding to a discrete input value obtained by reading an image is stored, and an interpolation process is performed based on the input value and the gamma correction value of a predetermined image stored in the gamma correction value storage unit. The gamma correction value interpolation means for calculating the gamma correction value for each is provided.
  • the gamma correction device is the gamma correction device according to claim 4, wherein the gamma correction value storage means is a discrete gamma correction device that reads a predetermined image.
  • the gamma correction value for an appropriate input value the gamma correction value for a low gradation part is stored more.
  • a gamma correction device is a gamma correction device for capturing gamma characteristics of a plurality of image pickup devices, wherein a gamma correction value of a reference device and a device that is each positionally adjacent to each other.
  • the difference value of the gamma correction value of the above is stored in a predetermined storage capacity, and when the difference value exceeds the predetermined storage capacity, the adjacent element exceeds the predetermined storage capacity by the difference value.
  • the gamma correction value storage means that adds and stores the value, and the reference element uses the stored gamma correction value, and the other elements use the gamma correction value of the reference element up to the position of the element.
  • Gamma correction value calculating means for calculating a gamma correction value for each element by integrating the differential values of the elements to be corrected, and gamma correction means for performing gamma correction for each element from the calculated gamma correction value. It is provided with.
  • the gamma correction device is the gamma correction device according to claim 7, wherein the gamma correction value storage means is a discrete gamma correction device that reads a predetermined image. The gamma correction value for the input value is stored. The gamma correction value is interpolated from the input value of the predetermined image and the gamma correction value stored in the gamma correction value storage means, and the gamma correction value for each element is obtained. It is provided with a gamma correction value capturing means for calculating the gamma correction value.
  • the gamma correction device is the gamma correction device according to claim 7, wherein the gamma correction value storage means is configured to read a predetermined image.
  • the gamma correction value for a typical input value the gamma correction value for the low gradation part is stored more.
  • the gamma correction device includes a plurality of imaging elements.
  • a gamma correction device that corrects the gamma characteristic of a child, the average value of the gamma correction value of each element for each input value and the difference value between the average value and the gamma correction value of each element are stored.
  • gamma correction means for performing gamma correction for each element.
  • the gamma correction device is the gamma correction device according to claim 10, wherein the gamma correction value storage means reads a predetermined image from a discrete image. A gamma correction value corresponding to a typical input value is stored. A gamma correction value is calculated from the input value of the predetermined image stored in the gamma correction value storage means and the gamma correction value. It is provided with a gamma correction value capturing means for calculating the gamma correction value.
  • the gamma correction device is the gamma correction device according to claim 10, wherein the gamma correction value storage means reads a predetermined image.
  • the gamma correction values for discrete input values are stored more.
  • a gamma correction device is a gamma correction device for correcting gamma characteristics of a plurality of imaging elements, wherein the gamma correction value of a reference element and a gamma correction value of a reference element are each different.
  • a gamma correction value storing means for storing a difference value between a gamma correction value between adjacent elements and a data length of the difference value; a reference element performs gamma correction by using a stored gamma correction value; For other elements, a gamma correction value calculating means for calculating a gamma correction value for each element by integrating a difference value of an element existing up to the position of the element with a gamma correction value of the reference element.
  • Gamma correction means for performing gamma correction for each element from the calculated gamma correction value.
  • the gamma correction device is the gamma correction device according to claim 13, wherein the gamma correction value storage means reads a predetermined image from a discrete image. A gamma correction value corresponding to a typical input value is stored, an interpolation process is performed from the input value of a predetermined image stored in the gamma correction value storage means and a gamma correction value, and a gamma correction value for each element is calculated. Equipped with gamma correction value capture means to calculate It is a thing.
  • the gamma correction device according to claim 15 of the present invention is the gamma correction device according to claim 13, wherein the gamma correction value storage means is a discrete gamma correction device that reads a predetermined image.
  • the gamma correction value for a typical input value is stored, the gamma correction value for the low gradation part is stored more.
  • a gamma correction device is a gamma correction device for correcting gamma characteristics of a plurality of imaging elements, wherein the gamma correction table storage means stores a plurality of gamma correction tables.
  • Gamma correction table selection information storage means for storing selection information for selecting a gamma correction table for each element; gamma correction table storage means; gamma correction table selection information storage means; A gamma correction table selecting means for selecting a gamma correction table corresponding to each child, and a gamma correction means for performing gamma correction based on the selected gamma correction table.
  • the gamma correction device is the gamma correction device according to claim 16, wherein the gamma correction table storage means has a gamma correction amount.
  • the gamma correction table with the smallest gamma correction amount or the gamma correction amount with the largest gamma correction amount is stored as the reference gamma correction table, and the other gamma correction tables are those whose reference gamma correction table has the smallest gamma correction amount.
  • the correction table when the gamma correction tables are arranged in ascending order of the gamma correction amount, the difference value of the adjacent gamma correction values is stored.On the other hand, the gamma correction amount is used as a reference gamma correction table.
  • the gamma correction tape Storing the difference value meets gamma ToTadashichi, those having a gamma correction table calculating means for calculating the gamma correction table and a gamma capturing positive table and the difference value of the reference.
  • the gamma correction device is the gamma correction device according to claim 16, wherein the gamma correction table selection means includes: The gamma that minimizes the least square sum of the gamma correction values with a plurality of gamma correction tables stored in the gamma correction table storage means This is to select a capture table.
  • a gamma correction apparatus is a gamma correction apparatus for correcting gamma characteristics of a plurality of imaging elements, wherein the gamma correction apparatus outputs an output characteristic correction value for an input value of a reference element before gamma correction.
  • An element characteristic that stores a certain element characteristic correction value and a difference value of an element characteristic correction value, which is an output characteristic correction value with respect to an input value before gamma correction, between elements adjacent in position with a predetermined storage capacity.
  • the correction value storage means and the reference element calculate a gamma correction value based on the stored element characteristic correction value, and the other elements exist in the element characteristic correction value of the reference element up to the position of the element.
  • An element characteristic calculation means for calculating a gamma correction value for each element by integrating the element difference values, and a gamma correction value for each element based on the calculated characteristic correction value for each element.
  • a calculating gamma correction value calculating means in which a gamma ToTadashi means for performing gamma correction for each element from the gamma correction value calculated above.
  • the gamma correction device according to claim 20 of the present invention is the gamma correction device according to claim 19, wherein the element characteristic storage means is configured to determine a position between adjacent elements in position.
  • the difference value of the element characteristic correction value is stored in a predetermined storage capacity, and when the difference value exceeds the predetermined storage capacity, an adjacent element adds and stores the excess value to the difference value. .
  • the gamma correction device is the gamma correction device according to claim 19, wherein the element characteristic correction value storage means is configured to correct element characteristic correction of the element.
  • the average value of the values and a difference value between the average value and the element characteristic correction value for each element are stored, and the element characteristic correction value calculating means converts the element value into an average value of the element characteristic correction value for each element.
  • the element characteristic correction value is calculated from the value obtained by adding the difference value for each element.
  • the gamma correction device is the gamma correction device according to claim 19, wherein the element characteristic storage means is a device which is positioned adjacent to the device. The difference between the element characteristic correction values is stored together with the data length.
  • the gamma correction device is the gamma correction device according to claim 19, wherein the element characteristic correction value storage means is configured to store a predetermined image.
  • the element characteristic correction value for the discrete input value obtained by reading The element characteristic correction value interpolation means calculates an element characteristic correction value for each element by performing an interpolation process from the input value of the predetermined image and the element characteristic correction value stored in the element characteristic correction value storage means. Is what you do.
  • the gamma correction device according to claim 24 of the present invention is the gamma correction device according to claim 19, wherein the element characteristic correction value storage means stores a predetermined image. When storing the element characteristic correction value for the read discrete input value, the element characteristic correction value of the low gradation part is stored more.
  • a gamma correction device that corrects the gamma characteristics of a plurality of imaging devices stores gamma correction values of all imaging devices.
  • Gamma correction value storage means e.g., a gamma correction value storage means, gamma correction value selection means for selecting a gamma correction value for each element from the gamma correction value storage means, and an element using the gamma correction value selected by the gamma correction value selection means.
  • a gamma correction unit that performs gamma correction individually for each device is provided.By performing gamma correction for each device, the gamma characteristics of the device can be corrected, and more accurate gamma correction can be performed. The effect that it can be obtained is obtained.
  • the gamma correction value storage means includes a discrete image read from a predetermined image. A gamma correction value for a specific input value is stored, and an interpolation process is performed based on the input value and the gamma correction value of a predetermined image stored in the gamma correction value storage means to calculate a gamma correction value for each element. Since gamma correction value capturing means is provided, only gamma correction values for discrete input values are stored, so that gamma correction can be performed for each element with a small storage capacity. Is received.
  • the gamma correction device in the gamma correction device according to claim 1, the gamma correction device according to claim 1, the gamma correction device according to claim 1, When the correction value storage means stores the gamma correction value for the discrete input value obtained by reading the predetermined image, the gamma correction value for the low gradation part is stored more, so that the amount of change is large. By storing more gamma correction values in the low gradation area, gamma correction can be performed for each element with less storage capacity and high accuracy. The effect that can be performed is obtained.
  • a gamma correction value of a reference device in a gamma correction device for correcting gamma characteristics of a plurality of image pickup devices, a gamma correction value of a reference device and a device that is positionally adjacent to each other
  • a gamma correction value storage means for storing a difference value between two gamma correction values with a predetermined storage capacity, and a gamma correction value stored as a reference element.
  • Gamma correction value calculating means for calculating a gamma correction value for each element by integrating the difference value of the element existing up to the position of the element with the gamma correction value, and a gamma correction value calculated from the calculated gamma correction value.
  • gamma correction means for performing gamma correction is provided for each element, the difference between the gamma correction values of elements adjacent in position is stored in a predetermined storage capacity, so that efficiency is improved. There is an advantage that it is possible to perform the gamma correction for each element in the absence storage capacity.
  • the gamma correction value storage means stores the discrete image obtained by reading a predetermined image.
  • the gamma correction values for the various input values are stored, and interpolation processing is performed from the gamma correction values and the input values of the predetermined image stored in the gamma correction value storage means to calculate the gamma correction values for each element.
  • Gamma correction value interpolation means for storing the difference value of the gamma correction value of the element adjacent in position with a predetermined storage capacity, and furthermore, only the gamma correction value for a discrete input value is stored.
  • the gamma correction value storage means reads a predetermined image from a discrete image.
  • the gamma correction value storage means reads a predetermined image from a discrete image.
  • the gamma correction value of the reference device in the gamma correction device for correcting the gamma characteristics of a plurality of imaging devices, the gamma correction value of the reference device And the difference value of the gamma correction value between the elements adjacent to each other with a predetermined storage capacity, and when the difference value exceeds the predetermined storage capacity, the difference value is calculated for the adjacent element.
  • the gamma correction value storage means for adding and storing the excess value, and the reference element uses the stored gamma correction value, and for the other elements, the gamma correction value of the reference element is added to the position of the element.
  • Gamma correction value calculation means for calculating a gamma correction value for each element by integrating the difference values of the existing elements, and gamma correction means for performing gamma correction for each element from the calculated gamma correction value.
  • the gamma correction value storage means stores a discrete image obtained by reading a predetermined image.
  • the gamma correction values for the various input values are stored, and interpolation processing is performed from the input values of the predetermined image and the gamma correction values stored in the gamma correction value storage means to calculate a gamma correction value for each element. Since the gamma correction value interpolation means is provided, even if the difference value exceeds the capacity for storing the difference value, the error can be minimized. Storing the correction value has the effect of reducing the storage capacity of the gamma correction value.
  • the gamma correction value storage means reads a predetermined image and stores the discrete image.
  • the gamma correction value storage means reads a predetermined image and stores the discrete image.
  • the gamma correction of each element for each input value is provided.
  • Gamma correction value storage means for storing an average value of the gamma correction values, a difference value between the average value and the gamma correction value for each element, and a gamma correction value for each element.
  • Gamma correction value calculating means for calculating a difference value for each element to calculate the gamma correction value, and gamma correction means for performing gamma correction for each element from the calculated gamma correction value. Since the gamma correction value is calculated by adding the difference value to the average value independently for each element, it is possible to perform the gamma correction accurately.
  • the gamma correction value storage means stores a predetermined image.
  • a gamma correction value corresponding to the read discrete input value is stored.
  • Interpolation processing is performed from the input value of the predetermined image and the gamma correction value stored in the gamma correction value storage means, and the gamma correction for each element is performed.
  • the gamma correction value interpolation means for calculating the correction value is provided, so that the gamma correction value can be calculated by adding the difference value to the average value independently for each element to calculate the gamma correction value. Also, by storing the gamma correction value for the discrete input value, the effect of reducing the storage capacity of the gamma correction value can be obtained.
  • the gamma correction value storage means stores a predetermined image.
  • more gamma correction values for the low gradation area are stored, so the difference value is added to the average value independently for each element.
  • the gamma correction value can be calculated to accurately perform gamma correction.
  • more low-gradation parts with a large change amount are stored more accurately to achieve storage capacity. Therefore, the effect of being able to reduce is obtained.
  • a gamma correction value of a reference element and a gamma correction value of a reference element are each set.
  • Gamma correction value storage means for storing the difference value between the gamma correction values of adjacent elements, the data length of the difference value, and the reference element perform gamma correction based on the stored gamma correction values.
  • the difference value of the element existing up to the position of the element is added to the gamma correction value of the reference element, thereby obtaining the element
  • Gamma correction value calculating means for calculating a gamma correction value for each element, and gamma correction means for performing gamma correction for each element from the calculated gamma correction value are provided.
  • the gamma correction value storage means reads a predetermined image.
  • a gamma correction value for a discrete input value is stored.
  • the gamma correction value is interpolated from the input value of the predetermined image and the gamma correction value stored in the gamma correction value storage means, and the gamma correction value for each element is obtained.
  • the gamma correction value interpolating means for calculating the gamma correction value is calculated, so that the difference value of the gamma correction value of the element adjacent in position is efficiently stored according to the magnitude of the difference value.
  • the gamma correction value storage means reads a predetermined image.
  • more gamma correction values are stored in the low gradation area, so that more gamma correction values are stored in the low gradation area with large changes.
  • the effect that gamma correction can be accurately performed for each element with a small storage capacity can be obtained.
  • a gamma correction table storage for storing a plurality of gamma correction tables Means, gamma correction table selection information storage means for storing selection information for selecting a gamma correction table for each element, and gamma correction table storage means and gamma correction table selection information storage means for each element.
  • Gamma correction table selection means for selecting the selected gamma correction table, and gamma correction means for performing gamma correction based on the selected gamma correction table, so that the gamma correction table selection information corresponding to each element is provided.
  • the gamma correction table storage means has the most gamma correction amount.
  • a small gamma correction table or a gamma correction table with the largest amount of gamma correction is stored as a reference gamma correction table, and the other gamma correction tables are based on the gamma correction table with the smallest gamma correction amount.
  • the gamma correction table is used, when the gamma correction tables are arranged in ascending order, the difference value of the gamma correction values that are adjacent to each other is stored.
  • the gamma correction table Has a gamma correction tape loss calculating means for storing a difference value between adjacent gamma correction values and calculating a gamma correction tape loss from the reference gamma correction table and the difference value.
  • the storage capacity of the gamma correction table storage means can be reduced by storing the difference value between the gamma correction tables having similar gamma correction characteristics. The effect that can be obtained is obtained.
  • the gamma correction table selecting means includes: The gamma correction table that minimizes the least square sum of the gamma correction values is selected from the table and the plurality of gamma correction tables stored in the gamma correction table storage means. By storing only the selection information of the gamma correction table for each element, the storage capacity can be reduced and the optimal gamma correction table can be selected accurately. can get.
  • a gamma correction device for correcting gamma characteristics of a plurality of imaging elements in a gamma correction device for correcting gamma characteristics of a plurality of imaging elements, a gamma correction device for input values of a reference element before gamma correction is provided.
  • the element characteristic correction value which is the output characteristic correction value
  • the difference value between the element characteristic correction value which is the output characteristic correction value for the input value before gamma correction, between the elements adjacent to each other, are predetermined.
  • the correction value storage means and the reference element calculate the gamma correction value based on the stored element characteristic correction value.
  • the element characteristic correction value calculating means for calculating the gamma correction value for each element by integrating the element characteristic correction value of the reference element with the difference value of the element existing up to the position of the element.
  • Gamma correction value calculating means for calculating a gamma correction value for each element from the calculated characteristic correction value for each element, and gamma correction means for performing gamma correction for each element from the calculated gamma correction value.
  • the gamma correction can be performed for each element with a smaller storage capacity by storing the difference between the characteristic correction values before gamma correction, where the difference in characteristics between the elements is small. 'Is obtained.
  • the element characteristic storage means includes a pair of elements adjacent in position.
  • the difference value of the element characteristic correction value of each element is stored in a predetermined storage capacity. Therefore, by storing the difference value of the characteristic correction value before gamma correction with a small difference in characteristics between elements with a predetermined storage capacity, it is possible to perform gamma correction for each element with a smaller storage capacity more efficiently. The effect is that it can be done.
  • the element characteristic correction value storage means includes: The average value of the characteristic correction values and the difference between the average value and the element characteristic correction value of each element are stored, and the element characteristic correction value calculating means calculates the average value of the element characteristic correction values of each element.
  • the element characteristic correction value is calculated from the value obtained by adding the difference value of each element, so that the difference value of the characteristic correction value before gamma correction, in which the characteristic difference between elements is small, is stored. The effect is obtained that the capacity can be reduced, and even if the difference value exceeds the capacity for storing the difference value, the error can be minimized.
  • the element characteristic storage means includes a pair of elements adjacent in position. Since the difference between the element characteristic correction values of the elements is stored together with the data length, the difference between the characteristic correction values before gamma correction where the characteristic difference between the elements is small By storing the values, the storage capacity can be reduced.In addition, for each element, a characteristic correction value is calculated by independently adding the difference value to the average value, and the gamma capture is calculated from the characteristic correction value. Since the positive value is calculated, the effect that the gamma correction can be performed accurately can be obtained.
  • the element characteristic correction value storage means reads a predetermined image.
  • the element characteristic correction value interpolating means stores the element value and the element characteristic correction value for the predetermined image stored in the element characteristic correction value storage means. Calculates the element characteristic correction value for each element by performing interpolation processing from, so that the difference value of the characteristic correction value before gamma correction where the characteristic difference between the elements is small is stored, and the discrete input value Storing the characteristic correction value has the effect of further reducing the storage capacity.
  • the element characteristic correction value storage means reads a predetermined image.
  • the element characteristic compensation IE values for discrete input values more element characteristic correction values in the low gradation area are stored, so that the characteristics before gamma correction have small differences in the characteristics between the elements.
  • the storage capacity is reduced, and by storing more characteristic correction values of the low gradation part where the amount of change becomes large after gamma correction, each element can be accurately stored with a small storage capacity. This has the effect that gamma correction can be performed.
  • FIG. 1 is a block diagram showing a configuration of a gamma correction device according to Embodiment 1 of the present invention.
  • FIG. 2 is a diagram showing a configuration of an image scanner to which the gamma correction device according to the first embodiment is applied.
  • FIG. 3 is a diagram illustrating an example of a gamma correction value of the gamma correction device according to the first embodiment.
  • FIG. 4 is a plot showing the configuration of a gamma correction device according to Embodiment 2 of the present invention.
  • FIG. 4 is a plot showing the configuration of a gamma correction device according to Embodiment 2 of the present invention.
  • FIG. 5 is a diagram showing an example of a grid used for calculating a gamma correction value.
  • FIG. 6 is a diagram showing an example of a gamma correction value for a 10-pattern gray chart.
  • FIG. 7 is a diagram for explaining an interpolation process for performing linear interpolation between data.
  • FIG. 8 is a diagram showing an example of a case where an ideal gamma curve whose gamma correction curve has a value of gamma 2.2 is linearly approximated by 10 discrete data.
  • FIG. 9 is a diagram illustrating an example of an interpolation process for minimizing an error from an ideal gamma curve by increasing the number of data in the low gradation area.
  • FIG. 10 is a block diagram showing a configuration of a gamma correction device according to Embodiment 3 of the present invention.
  • FIG. 11 is a diagram for explaining a method of calculating a difference value stored in a gamma correction value storage unit included in the gamma correction device according to the third embodiment.
  • FIG. 12 is a block diagram showing a configuration of a gamma correction device according to Embodiment 4 of the present invention.
  • FIG. 13 is a diagram for explaining a method for restoring a gamma correction value from a difference value of the gamma correction device according to the fourth embodiment.
  • FIG. 14 is a diagram for explaining a problem before using the interpolation method by the gamma correction device according to the fifth embodiment of the present invention.
  • FIG. 15 is a diagram for explaining an interpolation process using the gamma correction device according to the fifth embodiment of the present invention.
  • FIG. 16 is a block diagram illustrating a configuration of a gamma correction device according to a sixth embodiment of the present invention.
  • FIG. 17 is a diagram for explaining a difference value calculation method by the gamma correction device according to the sixth embodiment.
  • FIG. 18 is a block diagram showing a configuration of a gamma correction device according to Embodiment 7 of the present invention.
  • FIG. 19 is a diagram showing a gamma correction value storage circuit of the gamma correction device according to the seventh embodiment. It is a figure for explaining the recording method to a road.
  • FIG. 20 is an image diagram for explaining a state in which the data length of the difference value is stored together in the gamma correction value storage circuit of the gamma correction device according to the seventh embodiment.
  • FIG. 21 is an image diagram in the case of sequentially storing the data length of the gamma correction value and the gamma correction value according to the seventh embodiment.
  • FIG. 22 is a block diagram showing a configuration of a gamma correction device according to Embodiment 8 of the present invention.
  • FIG. 23 is a block diagram showing a configuration of a modification of the gamma correction device according to the eighth embodiment.
  • FIG. 24 is a block diagram showing a configuration of a gamma correction device according to Embodiment 9 of the present invention.
  • FIG. 25 is a diagram showing a relationship between element characteristics and ideal characteristics in the gamma correction device according to the ninth embodiment.
  • FIG. 26 is a diagram for explaining a difference value calculation method of the gamma correction device in the above embodiment 2.
  • FIG. 27 is a diagram conceptually illustrating a gamma correction method using a ROM storing a gamma correction table.
  • FIG. 28 is a block diagram showing a configuration of a conventional gamma correction device.
  • FIG. 29 is a diagram for explaining a gamma correction method using a conventional gamma correction device.
  • FIG. 30 is a diagram for explaining a difference value calculation method in a conventional gamma correction device.
  • FIG. 1 is a block diagram showing the configuration of the gamma correction device according to the first embodiment.
  • 101 is an image sensor such as a CCD
  • 102 is a CCD 1 0
  • a / D converter that converts the output of 1 to digital
  • 103 is the gamma correction circuit that receives the output of the AZD converter 102
  • 104 is the required gamma correction value from the gamma correction value storage circuit 105 Is a gamma correction table selection circuit
  • 106 is an element selection circuit.
  • the gamma correction is performed by the gamma correction circuit 103 using the individual gamma correction value for each device.
  • the gamma correction value for each element is stored in the gamma correction table stored in the gamma correction value storage circuit 105, and the gamma correction tape of the corresponding element is stored in the gamma correction table selection circuit 104.
  • the gamma correction circuit 103 performs gamma correction based on the gamma correction value in the selected gamma correction table.
  • the image scanner uses an image as shown in Fig. 2! : Reading. That is, in FIG. 2, reference numeral 201 denotes a read original, reference numeral 202 denotes illumination, and reference numeral 203 denotes a lens disposed between the read original 201 and the image sensor 204.
  • the reading principle is as follows.
  • the reading document 201 is illuminated by the illumination 202, the reflected light is imaged by the lens 203, and the light signal is converted into an electric signal by the image sensor 204.
  • the imaging element 204 is composed of a plurality of elements from element 1 to element N, and converts a light signal into an electric signal for each element.
  • gamma correction is performed by providing an individual gamma correction table for each element from the first element to the Nth element constituting the imaging element 204.
  • the gamma correction value storage circuit 105 stores the gamma correction table for each element.
  • the gamma correction value storage circuit 105 stores the value shown in FIG. 3 (b). It will be remembered. In this case, the gamma correction value is represented by 8 bits, that is, 1 byte.
  • the gamma correction value storage circuit 105 stores 256 gamma correction values for the input values 0 to 255 of the first element in one byte, and then the gamma correction value of the second element. Are stored in a single byte. In this way, all gamma correction values up to the Nth imaging element are stored.
  • the gamma correction table selection circuit 104 calculates the gamma correction value of the Nth element from the gamma correction value stored in the gamma correction value storage circuit 105. It is necessary to select the gamma correction value of the Nth element on the gamma correction value storage circuit 105.
  • a gamma correction table is prepared for each element in the gamma correction value storage circuit 105, and the correction table corresponding to each pixel is stored in the gamma correction table selecting means 10. Since gamma correction is selected by using 4 to perform gamma correction, highly accurate gamma correction can be performed, and deterioration in image quality can be suppressed.
  • FIG. 4 is a circuit block diagram of a gamma correction device according to the second embodiment.
  • the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and differ from FIG. 1 in that a gamma correction value interpolation circuit 404 and a pattern value storage circuit 408 are added.
  • a gray chart whose value is known in advance as shown in Fig. 5 is read from a scanner, the gamma correction value is calculated from the gray chart value and the read value, and the gray chart is calculated.
  • the gamma correction value for the input value that does not exist is calculated by interpolating the value by linear interpolation or curve interpolation.
  • the gamma correction value storage circuit 105 stores the gamma correction value for the gray chart pattern, and if the gamma correction value is interpolated by interpolating processing, the storage capacity can be reduced. be able to. For example, see Figure 5. Thus, in the case of a 10-pattern gray chart, the storage capacity can be reduced to 10/256 compared to storing gamma correction values for continuous input data from 0 to 255. . The method of calculating the gamma correction value will be described below.
  • the gamma correction value storage circuit 105 stores gamma correction values for the number of patterns for each element. For example, gamma correction values for a gray chart of 10 patterns are as shown in FIG.
  • the pattern value is the value obtained by measuring the pattern for each gradation of the gray chart with a measuring instrument.
  • the gamma correction table selection circuit 104 selects a gamma correction table for each element, and sends the gamma correction value to the gamma correction value interpolation circuit 404.
  • the gamma correction value interpolation circuit 404 interpolates the gamma correction value from the gamma correction value selected by the gamma correction table selection circuit 104 and the pattern value stored in the pattern value storage circuit 408. I do. For example, when the gamma correction value of the first element in FIG. 6 is interpolated, as shown in FIG. 7, the interpolation processing can be performed by interpolating a straight line between the data. For example, the gamma correction value Y for the pattern value X from 25 to 50 is
  • Gamma correction can be performed for each element by the gamma correction circuit 103 based on the gamma correction value interpolated by the gamma correction value interpolation circuit 404 in this manner.
  • more gamma correction values may be stored for a pattern in a low gradation area, that is, a pattern in a dark area. This is because the gamma correction curve has a large change in the low gradation area, and therefore, the gamma correction accuracy can be improved by taking more data in this area.
  • the sag chart used for calculating the gamma correction value should be a chart having more low gradation parts, that is, a chart having more patterns close to black, or a gray chart.
  • the gamma correction values in the low gradation area can be stored in the gamma correction value storage circuit 105 more. is there.
  • the gamma correction value for the discrete input data is stored in the gamma correction value storage circuit 105, and the pattern value storage circuit 4 storing the discreteness of the input data is stored.
  • the gamma correction value interpolation circuit 404 uses the pattern value including the corresponding input data from 08 and the gamma correction value stored in the gamma correction value storage circuit 105 to perform interpolation processing.
  • the gamma correction is calculated by calculating a gamma correction value, so that gamma correction can be performed for each pixel, and image quality degradation can be suppressed.
  • the storage capacity can be reduced, and costs can be reduced.
  • the error due to the interpolation processing can be reduced, and the accuracy of gamma correction can be further improved.
  • any element may be used as a reference element.
  • any number of reference elements may be provided.
  • the case where the gamma correction value corresponding to the discrete input value is stored and the case where 10 patterns of the delay chart are stored have been described, but the number of patterns is not limited to this.
  • interpolation may be performed not by linear approximation but by a curve such as a quadratic curve.
  • FIG. 10 is a block diagram showing the configuration of the gamma correction device according to the third embodiment.
  • the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and a gamma correction value calculation circuit 100 is provided instead of the gamma correction table selection circuit 104 in FIG.
  • the gamma correction value storage circuit 1005 stores the gamma correction table of the reference element and the gamma correction table of each of the other elements as a difference value with respect to the reference element. 5 is provided.
  • the operation will be described. After the input image is captured by the image sensor 101 and the input signal is digitized by the A / D converter 102, the gamma correction is performed by the gamma correction circuit 103 using individual gamma correction values for each device. Do.
  • the gamma correction value is obtained by calculating the gamma correction value of the element selected by the element selection circuit 106 from the gamma correction value stored in the gamma correction value storage means 1005. Calculate in 4.
  • the gamma correction table for each element from the first element to the Nth element is not stored as it is, but the gamma correction table for the element serving as a reference is stored in position.
  • the storage capacity is reduced.
  • Gamma correction is generally performed using gamma correction values for input data stored in ROM in a table format, as shown in Fig. 27. As described above, if this gamma correction table is to be provided for each element, for example, for 6 elements of 8 bits of R, G, and B colors,
  • the gamma correction table of the reference element stores the gamma correction value in the ROM as before, but for the other elements, the difference is stored by storing the difference value of the gamma correction table between the elements adjacent in position. To be smaller.
  • a table 111 shows gamma correction values for each element, and stores gamma correction values for input values of the first to fourth elements.
  • element 1 is the reference element and element 1 is 8-bit gun The correction value is stored.
  • the difference value of the gamma correction value between elements adjacent in position is stored. That is, the difference value is stored for the second element such as a difference value for each input value with the first element, and for the third element, a difference value for each input value with the second element.
  • the difference value of the input value 1 of the second element is the difference value between the second element gamma correction value 18 and the first element gamma correction value 21, the difference value is 1 3 (1 8-2 1 ).
  • the difference value is calculated in this manner, a value as shown in the table 1102 in FIG. 11 is obtained.
  • the difference values in Table 1102 are differences between adjacent pixels, so the difference value is significantly smaller than the original gamma correction value due to the small difference in element characteristics.
  • the value is between 1 and 3. Since storing these numerical values requires only 3 bits, the storage capacity can be reduced to about 3/8.
  • the reference element gamma correction value thus calculated and the difference value are stored in the gamma correction value storage circuit 1005.
  • the difference value is sequentially stored in three bits.
  • the gamma correction table of the gamma correction value storage circuit 1005 has the gamma correction table of the first element and the difference value 1 has the second element.
  • the gamma correction value is sequentially stored as the difference value between the third element and the first element, and the difference value ⁇ 2 as the difference value between the third element and the second element.
  • the gamma correction value calculation circuit 1004 restores the gamma correction value for each element from the reference element gamma correction value and the difference value stored in the gamma correction storage circuit 1005. This restoration method will be described with reference to FIG.
  • the gamma is corrected using the stored gamma correction value.
  • Make corrections For example, when the input image data is 3, gamma correction can be performed by outputting a value 34 corresponding to the input value 3 as output data.
  • the gamma correction value is calculated by adding the value obtained by integrating the difference value up to the element position to the gamma correction value of the reference element, and the gamma correction is performed. For example, number 4 When calculating the gamma correction value corresponding to the input value 0 of the element, the gamma correction value corresponding to the input value 0 of the first element, which is the reference, is 0, and the difference value of the second element is 1, 3, Since the difference value of the element is 11 and the difference value of the fourth element is 2, the value obtained by integrating these values is the gamma correction value. That is,
  • the gamma correction value is calculated. Looking at the table 111 of FIG. 11, it can be seen that the gamma correction value corresponding to the original input value 0 of the fourth element is 2, so that the gamma correction value can be faithfully restored. Similarly, for other elements, a gamma correction value for each element can be calculated by adding a value obtained by integrating the difference value up to the element position to the gamma correction value of the reference element.
  • the gamma correction value calculation circuit 1004 calculates and calculates the gamma correction value for each element selected by the element selection circuit 106 from the reference element gamma correction tape hole and the difference value.
  • Gamma correction can be performed by the gamma correction circuit 103 from the gamma correction value for each element.
  • the difference value between the gamma correction value of the reference element and the gamma correction value of the element adjacent in position is predetermined in the gamma correction storage circuit 1005.
  • Gamma correction is performed using the stored gamma correction value for the reference element, and gamma correction is performed for the other elements by integrating the gamma correction value of the reference element with the differential value up to the element position. Since the gamma correction is performed by calculating the value, the gamma correction can be performed for each pixel, which can suppress the deterioration of the image quality and the gamma correction data for each element with a small storage capacity. Can be memorized.
  • the storage capacity may be changed such that the lower gray scale side stores it as 4 bits and the other gray scales stores it as 2 bits. Good. This is because, as described above, the gamma correction value of the element tends to fluctuate on the low gradation side, so that the difference value becomes large. This is because storage capacity may be wasted. Therefore, as described above, the storage capacity may be changed between the low gradation side and the rest for efficient storage.
  • Embodiment 4 a gamma correction device according to Embodiment 4 of the present invention will be described.
  • This embodiment has a feature in which the configurations of the above-described second embodiment and the third embodiment are combined. That is, in FIG. 12, the same reference numerals as those in FIGS. 4 and 10 indicate the same or corresponding parts, and 1204 indicates the value obtained from the gamma correction value storage circuit 1005.
  • Gamma correction that calculates an appropriate gamma correction value by interpolation using the output of the gamma correction value calculation circuit 104 and the pattern value output from the pattern value storage circuit 408 It is a value interpolation circuit.
  • the gamma correction value storage circuit 1005 stores the gamma correction value for the gray chart pattern, and interpolates the gamma correction value by interpolation. By doing so, it is possible to perform gamma correction with a small storage capacity. That is, the gamma correction value storage circuit 1005 stores the reference element gamma correction table values and the difference values for the number of patterns. 'For example, data as shown in the first 3 (a) view tables are stored. The gamma positive value calculation circuit 1005 calculates the gamma correction value of each element by the method described above. In the case of the table shown in Fig. 13 '(a), element 1 is the reference element, so elements 2 to N are the reference elements. The gamma correction value can be calculated as shown in the table shown in FIG. 13 (b) by adding up the value obtained by integrating the difference values of.
  • the gamma correction value capturing circuit 1204 calculates the gamma correction value from the gamma correction value calculated from the gamma correction value calculation circuit 1005 and the pattern value stored in the pattern value storage circuit 408. Performs interpolation. With regard to this capturing method, interpolation processing is performed according to the method described in the second embodiment.
  • Gamma correction can be performed for each element by the gamma correction circuit 103 based on the gamma correction value interpolated by the gamma correction value interpolation circuit 124 in this manner.
  • the gamma correction storage circuit 1005 stores the gamma correction value of the reference element and the difference value of the gamma correction value of each element stored discretely, The reference element performs gamma correction based on the stored gamma correction value, and the other elements perform gamma correction by calculating an appropriate gamma correction value by interpolation processing in the gamma correction value interpolation circuit 124.
  • Gamma correction for each pixel This makes it possible to suppress deterioration in image quality and to store gamma correction data for each element with a smaller storage capacity.
  • the gamma correction curve has a large change in the low gradation area
  • discrete data is used for the purpose of improving the gamma correction accuracy by taking more data in this area.
  • more gamma correction values for the pattern of the low gradation part that is, the pattern of the area ⁇ ⁇ may be stored.
  • any element may be used as a reference element.
  • any number of reference elements may be provided. Also, the case where the gamma correction value for a discrete input value is stored and the case where 10 patterns of a gray chart are stored has been described, but the number of patterns is not limited to this.
  • interpolation may be performed using a curve such as a 'quadratic curve' instead of performing linear approximation.
  • a gamma correction device according to a fifth embodiment of the present invention will be described with reference to the drawings.
  • the configuration and the basic operation of the gamma correction device according to the fifth embodiment are the same as those described in the third embodiment, except that the gamma correction value storage circuit Rather than storing the difference value of the gamma correction values between elements as it is, if the difference value exceeds the capacity to store the difference value, the next adjacent element adds the excess value to the difference value Is stored as a difference value.
  • the operation will be described in detail.
  • storing the difference value in a predetermined storage capacity greatly simplifies the process of restoring the original gamma correction value.
  • the difference value is larger than the predetermined storage capacity and the storage capacity is exceeded.
  • the gamma correction value is calculated by integrating the difference value as it is, the original gamma correction value cannot be restored.
  • the gamma correction value is In the case where the difference value is stored in 4 bits, the difference value for each element is as shown in Table 1402 in FIG. With 4 bits, values from 8 to 7 cannot be stored.For example, the gamma correction value of element 1 corresponding to input value 1 is 16, the gamma correction value of element 2 is 26, and the difference value is 2. Despite being 10, it exceeds 4 bits and is stored as difference value 7.
  • the gamma correction value corresponding to the input value 1 of the fourth element is 17.
  • the error is added to the next difference value so that the error does not affect the gamma correction value calculation of the next element.
  • the gamma correction value storage circuit 1005 stores the difference value of the gamma correction value between the elements that are adjacent in position, the difference value When the storage capacity is exceeded, the difference value is added to the difference value in the next adjacent element, and the difference value is stored as the difference value.Therefore, gamma correction must be performed for each element with a small storage capacity. When the difference value exceeds the capacity for storing the difference value, the error can be minimized.
  • the gamma correction values for the continuous input data are not stored in the element characteristic correction value table, as described in the second embodiment, but the gamma correction values for the discrete input data are stored.
  • the storage capacity can be further reduced.
  • the gamma correction value for the discrete input value can be stored, the gamma correction value for the low gradation part pattern, that is, the pattern in the dark area is stored more, so that the gamma correction in the low gradation part is stored.
  • Gamma correction accuracy can be improved in a region where the change of the positive curve is large.
  • any element may be used as a reference element.
  • any number of reference elements may be provided.
  • FIG. 16 is a block diagram showing the configuration of the gamma correction device according to the sixth embodiment.
  • the same reference numerals as those in FIG. 1 denote the same or corresponding parts
  • 1604 denotes the average value of the gamma correction values of the elements, and the average value and the gamma correction value of each element.
  • This is a gamma correction value calculation circuit that calculates a gamma correction value based on the value output from the gamma correction value storage circuit 1605 that stores the difference value of.
  • the difference value from the average value of the gamma correction value for each element is stored, It is characterized by performing gamma correction.
  • the gamma correction value storage circuit 1605 calculates and stores the average value of the gamma correction value for each input value and the difference value between the gamma correction value for each element and the average value. For example, if the gamma correction value for each element is as shown in Table 1701 in Fig. 17 (a), the average value and the difference value with respect to the average value are as shown in Fig. 17 (b). It is calculated as shown in Table 1702. For example, when the average value of the gamma correction values of the respective elements with respect to the input value 1 is 21, the gamma correction value of the first element is 16, and the difference value 15 is stored as the difference value.
  • the average value and the difference value are calculated and stored in the gamma correction value storage circuit 1605. Therefore, the average value of each input value is stored in the average value data of the gamma correction value storage circuit 165, and the difference value ⁇ 1 is the difference value of the first element, and the difference value ⁇ 2 is the second element. It is stored as a difference value. By storing the difference value from the average value as the gamma correction value, the storage capacity can be reduced.
  • the element selected by the element selection circuit 1606 from the average value data and the difference value stored in the gamma correction value storage circuit 1605. Calculate the gamma correction value.
  • the first device creates a gamma correction table by adding the difference value ⁇ 1 to the average value data
  • the second device creates a gamma correction table by adding the difference value ⁇ 2 to the average value data. be able to.
  • the average value of the gamma correction values of the elements and the difference value between the average value and the gamma correction value of each element are stored in the gamma correction value storage circuit 1605.
  • the average value of the gamma correction values output from the gamma correction value storage circuit 1605, and the difference between the average value and the gamma correction value of each element The gamma correction value is calculated from the value obtained by adding the difference value for each element to the average value of the gamma correction values for each element using the values and the gamma correction circuit 106.
  • the gamma correction value is calculated by independently adding the difference value to the average value for each element, so that gamma correction can be performed accurately and the difference value of each element is stored independently. Therefore, if the difference value exceeds its storage capacity, the error does not affect the gamma correction of other elements.
  • the gamma correction value storage circuit 1605 does not store the gamma correction values for continuous input data, but instead stores gamma correction values for discrete input values. If the correction value is stored, the storage capacity can be reduced.
  • FIG. 18 is a block diagram showing the configuration of the gamma correction device according to the seventh embodiment.
  • the same reference numerals as those in FIG. 10 denote the same or corresponding parts
  • 1804 denotes a gamma correction value storage circuit 1805 in which the data length of the difference value is stored together.
  • This is a gamma correction value calculation circuit that calculates a gamma correction value by receiving an output.
  • the basic operation is the same as that described in the third embodiment, except that the difference value is not stored in a predetermined storage capacity, but the storage capacity is changed according to the magnitude of the difference value. Are different.
  • the operation will be described in detail.
  • the difference value of the gamma correction value between the elements adjacent in position when the difference value of the gamma correction value between the elements adjacent in position is calculated, the difference value takes various values, so that the difference value is stored in a certain storage capacity. It may be inconvenient to memorize. Therefore, by changing the storage capacity according to the magnitude of the difference value, the difference value can be flexibly stored. At that time, by storing the data length of the difference value together, the gamma correction value can be accurately restored.
  • the difference value of the second element is shown in the table of Fig. 19 (b). It is calculated as shown.
  • the difference value is sequentially recorded as a data length and a difference value as shown in FIG. I will remember. In the case of Fig. 20, the data length is stored in 3 bits, and then the difference value is stored.
  • the data length can be stored in 3 bits by storing the data length as 0 if the difference value is 1 bit, 1 if the difference value is 2 bits, 7 if the difference value is 8 bits, and so on.
  • the difference value of the second element corresponding to the input value 0 is 0, and can be represented by 1 bit, so that the data length is stored as 0.
  • the difference value corresponding to the input value 1 is 10 and can be expressed by 5 bits, the data length is stored as 4.
  • the calculated data length and difference value are sequentially stored as shown in FIG.
  • the difference value can be accurately stored, and the difference value can be adjusted according to the size of the difference value. Can be stored efficiently.
  • the gamma correction value storage circuit 1805 does not store the gamma correction value for the continuous input data, but stores the gamma correction value for the discrete input value. If the information is stored, the storage capacity can be reduced.
  • the gamma correction value can be restored more accurately, so that the accuracy of gamma correction can be improved.
  • FIG. 22 is a block diagram showing a configuration of the gamma correction device according to the eighth embodiment.
  • reference numeral 2204 denotes a gamma correction table selection circuit, which includes an output of a gamma correction table storage circuit 222 composed of a plurality of gamma correction tables, and a gamma correction table corresponding to each element.
  • the predetermined data is selected from the output of the gamma selection value storage circuit 222 in which the number of the gamma is recorded.
  • a plurality of gamma correction tables are prepared in advance, and The storage capacity of the gamma correction value is reduced by selecting a certain gamma correction table.
  • the gamma correction table storage circuit 222 stores N gamma correction tables. A number is assigned to each gamma correction table, a gamma correction table is selected by the number for each element, and gamma correction is performed from the selected gamma correction table.
  • the gamma selection value storage circuit 222 stores a selection number for selecting a gamma correction tape for each element. For example, when the first element selects the gamma correction table 3, the selection number 3 is stored in the gamma selection value storage circuit 222 as the first element table selection number.
  • the gamma correction table selection circuit 222 selects the gamma correction table of the corresponding element from the gamma correction table storage circuit 222 with reference to the selection number of the gamma selection value storage circuit 222. Then, the gamma correction circuit 103 performs gamma correction based on the selected gamma correction table.
  • the overall storage capacity can be reduced. For example, when preparing gamma correction tables for 640 elements, if the gamma correction tables for all elements are prepared individually, the force required for 640 staples Since some devices have gamma characteristics, if 100 gamma correction tables are sufficient, the gamma correction table can be stored with a capacity of 100/6640. In this case, since the capacity of the gamma selection value storage circuit 222 is small, it can be ignored.
  • the gamma selection table (gamma selection value storage circuit 222) is stored in the ROM of the scanner body, and the gamma correction table (gamma correction table storage circuit) is stored in the personal computer. 2 2 0 6).
  • the ROM of the scanner itself has a limited capacity, but when storing it on the personal computer side, a much larger storage capacity can be prepared compared to the ROM of the scanner itself.
  • the ROM capacity of the image scanner can be reduced and more gamma correction tables can be stored.
  • an accurate gamma correction table for each element is calculated, and the table selection number for each element is calculated by comparing the gamma correction table with the gamma correction table prepared in the gamma correction table storage circuit 222 in advance.
  • the gamma correction table can be selected accurately.
  • the gamma correction table storage circuit 2307 stores a reference gamma correction table serving as a reference and a difference value between each gamma correction table and the reference gamma correction table. You may make it. By storing the difference value, the storage capacity of the gamma correction table 2307 can be further reduced.
  • the reference gamma correction table select the gamma correction table with the smallest gamma correction amount. In this case, the gamma correction table is arranged in the order of the smaller gamma correction amount, and the difference value of the gamma correction table is calculated.
  • the difference value ⁇ 1 of the gamma correction table 2307 stores the difference value between the gamma correction table having the second smallest gamma correction amount and the gamma correction table having the smallest gamma correction amount.
  • the difference value ⁇ 2 has a gamma correction table having the third smallest gamma correction amount
  • the difference value with the gamma correction table having the second smallest gamma correction amount is stored.
  • the gamma correction table with the largest gamma correction amount is selected, and when the gamma correction tables are arranged in descending order of the gamma correction amount, the order is adjacent.
  • the difference value of the gamma correction value in the gamma correction table may be stored.
  • the gamma correction value calculation circuit 2306 can calculate the gamma correction table by integrating the difference value with the reference gamma correction table. This is the same as the method described in the third embodiment. For example, if the gamma correction tables are stored in ascending order of the gamma correction amount, the fourth gamma correction table with the smallest gamma correction amount will be the difference value ⁇ 1, difference value ⁇ 2, difference value Value ⁇
  • a plurality of gamma correction tables are stored in the gamma correction table storage circuit 222 in advance, and the gamma correction values are stored in the gamma selection value storage circuit 222 for each element.
  • the selection information of the correction table is stored, and the gamma correction table selection circuit 222 is used to store the gamma correction table corresponding to the tape number stored in the corresponding gamma selection value storage circuit 222.
  • the gamma correction table storage circuit 2307 stores a reference gamma correction table serving as a reference, and a difference value between each gamma correction table and the reference gamma correction table.
  • the storage capacity of the correction table can be further reduced.
  • FIG. 24 is a block diagram showing the configuration of the gamma correction device according to the ninth embodiment.
  • reference numeral 2404 denotes a gamma correction value calculation circuit for calculating a gamma correction value based on a characteristic correction value output from an element characteristic correction value calculation circuit 2405 described later;
  • Reference numeral 5 denotes a characteristic correction of the element selected by adding a value obtained by integrating the difference value up to the element position to a reference element characteristic correction table stored in an element characteristic correction value storage circuit 2406 described later.
  • An element characteristic correction value calculation circuit for calculating a value, and an element characteristic correction value storage circuit 2404 stores an output characteristic correction value corresponding to an input value of the element before performing gamma correction.
  • the basic operation is the same as that of the third embodiment described above. However, instead of storing the gamma correction table, an element characteristic correction value that is an output characteristic correction value for an input value of an element before performing gamma correction is obtained. The difference is that they are stored.
  • the characteristics of the ideal element before gamma correction are linear with respect to the input data, as shown in Fig. 25.
  • JP ⁇ 1 Raw actual elements are offset from the linear characteristic as shown in the second 5 FIG. Therefore, the characteristic correction value for correcting the deviation from the ideal characteristic is stored to correct the characteristic, and a uniform gamma correction process is performed on the corrected characteristic value.
  • the characteristic correction value before gamma correction is stored.
  • the difference value for each element can be reduced as compared with the case where This is the characteristic that when the gamma correction is performed, the characteristics of each element greatly vary in the low-gradation area due to a large change in characteristics.
  • the element characteristics before gamma correction are such that the output value with respect to the input value is almost linear. Therefore, the characteristics do not change significantly, and the difference value for each element can be reduced.
  • the characteristic correction value for each element is as shown in Table 2601 in FIG. 26, and is a value that is almost linear with respect to the input value. Therefore, the difference between the elements adjacent in position is also as shown in Table 260 of FIG. 26, and it is necessary to make the difference smaller than when the difference of the gamma correction value is obtained. Can be.
  • the difference value is a value between 1 and 2 and the difference value can be expressed with 2 bits, so the storage capacity of the gamma correction value can be set to about 2Z8. it can.
  • the element characteristic correction value storage circuit 2406 stores a reference element characteristic correction table that is used as a reference when calculating the original characteristic correction value from the difference value, and a difference value between the characteristic correction values of the elements adjacent in position. Are stored in order.
  • the element characteristic correction table of the first element is stored in the reference element characteristic correction table
  • the difference value ⁇ 1 is the difference value between the element characteristics of the second element and the first element.
  • the difference value ⁇ 2 stores the adjacent difference value such as the difference value of the element characteristics between the third element and the second element with a predetermined storage capacity.
  • the element characteristic correction value calculation circuit 2405 stores the element characteristic correction value of the element selected by the element selection circuit 2407 in the element characteristic correction value storage circuit 2. It is calculated by adding a value obtained by integrating the difference values up to the element position to the reference element characteristic correction table stored in 406.
  • the gamma correction value calculating circuit 2404 compares the gamma correction value corresponding to the output monitor characteristics with the characteristic correction value for each element calculated by the element characteristic correction value calculating circuit 2405. Is calculated.
  • a gamma correction value is calculated so that the reciprocal of the gamma characteristic is 0.45.
  • the gamma correction value for the input value in that case is
  • the gamma correction for each element can be performed with a small storage capacity by storing the element characteristic correction value before the gamma correction.
  • the difference value stores the difference value. If the excess capacity is exceeded, a value obtained by adding the excess value to the difference value may be stored as a difference value in the next adjacent element. By adding the excess value to the difference value of the next element, data can be restored with a minimum error.
  • the element characteristic correction value for each input value is stored.
  • the difference between the characteristic correction value and the average value of each element may be stored. In this way, when the difference value exceeds the storage capacity because the difference value of each element is stored independently, it is possible to prevent the error from affecting the gamma correction of other elements. it can.
  • the difference value of the characteristic correction value between the elements adjacent in position may be stored as the data length and the difference value.
  • the difference value can be stored flexibly, and the element characteristic correction value can be accurately restored by storing the data length of the difference value together.
  • the element characteristic correction value table does not store characteristic correction values for continuous input data from 0 to 255, but rather stores discrete characteristic values. Characteristic correction values for various input data may be stored.
  • element characteristic values corresponding to discrete input values are stored, as described in Embodiment 2, accuracy is improved by storing more data in a low gradation area, that is, in a dark area. Can be done.
  • the first element is used as a reference element as a reference element. However, any element may be used as a reference element. Furthermore, instead of having only one reference element, any number of reference elements may be provided. Industrial applicability
  • a gamma correction device includes a gamma correction value storage unit that stores a gamma correction value for each image sensor, and performs a gamma correction process in which a gamma correction value is selected for each element, thereby achieving high accuracy.
  • Gamma correction to provide an image with little image quality degradation.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Picture Signal Circuits (AREA)
  • Facsimile Image Signal Circuits (AREA)
  • Image Processing (AREA)

Abstract

La présente invention concerne un dispositif de correction du gamma permettant de réduire l'encombrement mémoire de la valeur de la correction du gamma, quelle que soit la longueur de la donnée introduire. La logique est de prendre la valeur de correction du gamma pour la donnée introduite discrète et de la ranger dans un circuit de mémoire de valeur de correction du gamma (105) de façon à calculer une valeur appropriée de correction du gamma permettant d'effectuer une correction du gamma par une procédure d'interpolation menée au niveau d'un circuit d'interpolation de valeur de correction du gamma (404). Cette procédure implique l'utilisation d'une valeur de courbe contenant une donnée d'entrée applicable provenant d'un circuit de mémoire de valeur de courbe (408) faisant de la mémorisation avec le degré discret de la donnée d'entrée et la valeur de correction du gamma mémorisée dans le circuit de mémoire de valeur de correction du gamma (105).
PCT/JP2001/005562 2000-06-29 2001-06-28 Dispositif de correction du gamma WO2002001850A1 (fr)

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JP2000197049A JP3552996B2 (ja) 2000-06-29 2000-06-29 ガンマ補正装置

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CN1320826C (zh) * 2003-10-30 2007-06-06 精工爱普生株式会社 图像处理电路、图像显示装置以及图像处理方法
US8094238B2 (en) 2006-04-11 2012-01-10 Panasonic Corporation Video signal processing device and video signal processing method
US10097739B2 (en) 2016-09-16 2018-10-09 Kabushiki Kaisha Toshiba Processing device for performing gamma correction

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JPWO2006057314A1 (ja) * 2004-11-25 2008-06-05 株式会社インフォワード 画像処理装置および画像処理方法
JP4534943B2 (ja) * 2005-10-06 2010-09-01 富士ゼロックス株式会社 変換テーブルの作成方法、画像処理装置及びプログラム
TWI343044B (en) 2006-05-15 2011-06-01 Princeton Technology Corp Adaptive gamma transform unit and related method
JP5052917B2 (ja) * 2007-03-06 2012-10-17 古河電気工業株式会社 光出力制御装置およびその制御方法
JP2009049752A (ja) 2007-08-21 2009-03-05 Nec Electronics Corp 映像信号処理装置、映像信号処理方法、及び表示装置
JP5100623B2 (ja) * 2008-11-27 2012-12-19 三菱電機株式会社 画像読取装置及び色補正係数生成方法

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JPH01160177A (ja) * 1987-12-16 1989-06-23 Canon Inc 画像読み取り装置
JPH03136466A (ja) * 1989-10-20 1991-06-11 Fuji Photo Film Co Ltd シェーディング補正方法
JPH04371073A (ja) * 1991-06-20 1992-12-24 Mitsubishi Electric Corp 画像読取装置
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JP2000244739A (ja) * 1999-02-22 2000-09-08 Ricoh Co Ltd 画像読取装置

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1320826C (zh) * 2003-10-30 2007-06-06 精工爱普生株式会社 图像处理电路、图像显示装置以及图像处理方法
US8094238B2 (en) 2006-04-11 2012-01-10 Panasonic Corporation Video signal processing device and video signal processing method
US10097739B2 (en) 2016-09-16 2018-10-09 Kabushiki Kaisha Toshiba Processing device for performing gamma correction

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