Image display apparatus

• US 7,423,661 B2
• Filed: 05/18/2004
• Issued: 09/09/2008
• Est. Priority Date: 05/19/2003
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Sagano, Osamu, Abe, Naoto
• Primary Examiner(s): Patel; Nitin
• Application Number:
  US10/847,415
• Publication Number:
  US 20040246277A1
• Time in Patent Office: 1,575 Days
• Field of Search: 345/204, 345690-695, 345 87-100, 348/671, 358/455, 358/456, 382/237, 382/274
• US Class Current: 345/690
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/2081 with combination of amplitude modulation and time modulation space and time error diffusion G09G3/2066
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: G09G 5/18 Timing circuits for raster scan displays specially adapted for television H04N ; synchronisation between the display unit and other display units, videodisc player G09G5/12

Abstract

Driving condition is determined so that the stimulating values of brightness with respect to drive data become closer to being regular in interval. As the drive condition, the frequency of a reference clock used for the pulse width modulation is changed to be higher than the range of high gradations in the range of low gradations in drive data. Accordingly, smaller increment in brightness in the range of low gradation and larger increment in the range of high gradations are achieved.

Claims

1. An image display apparatus comprising;

display elements, the display elements performing brightness gradation display by being applied with a modulated signal;

a modulation circuit for generating a modulated signal modulated based on incoming drive data; and

a clock supplying circuit for supplying a reference clock whereof the frequency changes at a predetermined cycle for controlling a pulse width of the modulated signal or at least one of the pulse width and a crest value transition to the modulation circuit,

wherein the modulation circuit generates such modulated signal that the difference in display brightness generated when making the display elements display by two modulated signals obtained based on the drive data having one gradation difference in a first range of gradations, which is part of an entire range of gradations of the incoming drive data, becomes smaller than the difference in display brightness in a second range of gradations, which is different from the first range of gradations,

wherein the modulation circuit enumerates the reference clock and controls the pulse width of the modulated signal or at least one of the pulse width and the crest value transition based on the enumerated value and the drive data, and

wherein a drive data converting unit for converting incoming data and outputting output signals as the drive data is provided in a previous stage of the modulation circuit, and the total number of gradations of the signals outputted from the drive data converting unit is smaller than the total number of gradations in data to be supplied into the drive data converting unit.

2. An image display apparatus according to claim 1, further comprising a signal processing circuit in a previous stage of the drive converting unit, wherein a signal processed by the signal processing circuit is supplied into the drive data converting unit.

3. An image display apparatus according to claim 2, wherein the signal processing circuit performs a color adjustment process for the signal supplied into the signal processing circuit.

4. An image display apparatus according to claim 2, wherein the signal processing circuit corrects a signal, which is supplied into the signal processing circuit and which corresponds to a predetermined display element out of the plurality of display elements, the signal being corrected based on the signals corresponding to other display elements.

5. An image display apparatus according to claim 2, wherein the drive data converting unit outputs incoming data after having converted so that a desired relation is achieved between incoming data and display brightness.

6. An image display apparatus according to claim 5, wherein the drive data converting unit converts incoming data so as to achieve a display at a brightness instructed by incoming data.

7. An image display apparatus according to claim 2, further comprising a non-linear converting unit in a previous stage of the signal processing circuit, wherein the non-linear converting unit performs non-linear conversion for moderating non-linear conversion of a signal to be supplied into the non-linear conversion unit performed by a sender of the signal in order to obtain the signal.

8. An image display apparatus according to claim 1, wherein the modulation circuit enumerates the reference clock and controls the pulse width of the modulated signal based on the enumerated value and the drive data, and the frequency of the reference clock in an area where the enumerated value is small differs from that in an area where the enumerated value is large.

9. An image display apparatus according to claim 8, wherein the modulation circuit performs a crest value modulation preference type combined modulation, which is the combination of the pulse width modulation and the crest value modulation based on the incoming drive data.

10. An image display apparatus according to claim 1, wherein the modulation circuit enumerates the reference clock and controls the pulse width of the modulated signal based on the enumerated value and the drive data, performs the crest value modulation preference type combined modulation, which is the combination of the pulse width modulation in which the pulse width is controlled and the crest value modulation for selecting at least two crest values, which bring the display elements into the different ON-states, and outputs the modulated signal to make the crest value vary in stages,

wherein the frequency of the reference clock is switched in stages, and

wherein the modulation circuit further includes a drive data converting unit for correcting variations in gradation caused by the fact that a portion where the crest value of the modulated signal changes in stages positions before and after the portion at which the frequency of the reference clock is switched.

11. An image display apparatus according to claim 1, wherein the display element is a cold cathode element.

12. An image display apparatus according to claim 1, wherein the display elements are interconnected into a matrix by a plurality of row wirings and column wirings,

wherein a row selecting circuit for selecting at least one row wiring out of the plurality of row wirings for a predetermined selection period is provided, and

wherein the modulation circuit supplies a modulated signal based on the drive data to the plurality of row wirings synchronously with the selection period.

13. An image forming apparatus according to claim 1, further comprising:

a signal processing circuit provided in a previous stage of the drive data conversion unit; and

a non-linear conversion unit provided in a previous stage of the signal processing circuit,

wherein the non-linear converting unit performs non-linear conversion for moderating non-linear conversion of a signal to be supplied into the non-linear conversion unit performed by a sender of the signal in order to obtain the signal.

14. An image display apparatus, comprising:

display elements, the display elements performing brightness gradation display by being applied with a modulated signal; and

a modulation circuit for generating a modulated signal modulated based on incoming drive data,

wherein the modulation circuit generates such modulated signal that the difference in display brightness generated when making the display elements display by two modulated signals obtained based on the drive data having one gradation difference in a first range of gradations, which is part of the entire range of gradations of the incoming drive data, becomes smaller than the difference in display brightness in a second range of gradations, which is different from the first range of gradations, and

wherein the modulation circuit performs the pulse width modulation preference type combined modulation, which is the combination of the pulse width modulation and the crest value modulation, for selecting at least two crest values for bringing the display element into the different ON-states based on the incoming drive data,

wherein one of the two crest values is to be used as a crest value for the portion of the modulated signal in which the crest value is increased, which corresponds to the increased amount of the drive data in the first range of gradations, and the other one is to be used as a crest value for the portion of the modulated signal in which the crest value is increased, which corresponds to the increased amount of the drive data in the second range of gradations, and

wherein a drive data converting unit for converting incoming data and outputting output signals as the drive data is provided in a previous stage of the modulation circuit, and the total number of gradations of the signals outputted from the drive data converting unit is smaller than the total number of gradations in data to be supplied into the drive data converting unit.

15. An image display apparatus according to claim 14, further comprising:

a signal processing circuit provided in a previous stage of the drive data conversion unit; and

a non-linear conversion unit provided in a previous stage of the signal processing circuit,

wherein the non-linear converting unit performs non-linear conversion for moderating non-linear conversion of a signal to be supplied into the non-linear conversion unit performed by a sender of the signal in order to obtain the signal.

16. An image display apparatus, comprising:

display elements, the display elements performing brightness gradation display by being applied with a modulated signal; and

a modulation circuit for generating a modulated signal modulated based on incoming drive data,

wherein the modulated circuit generates such modulated signal that the difference in display brightness generated when making the display elements display by two modulated signals obtained based on the drive data having one gradation difference in a first range of gradations, which is part of the entire range of gradations of the incoming drive data, becomes smaller than the difference in display brightness in a second range of gradations, which is different from the first range of gradations, and

wherein pulse width control is performed on the waveform of the modulated signal by the slot width, and

wherein crest value control is performed on crest values in each slot at least in n-stage from Al to An, where n is an integer number equal to or larger than two, and 0<

A1<

A2<

. . . An, corresponding to the different ON-states of the display element, and

wherein the waveform of the modulated signal having the portion rising to the predetermined crest value Ak, where k is an integer number between two and n inclusive, rises to the predetermined crest value Ak via the respective crest values from Ak-1 to A1 at least one slot each in sequence, and

wherein a drive data converting unit for converting incoming data and outputting signals as the drive data is provided in a previous stage of the modulation circuit, and the total number of gradations of the signals outputted from the drive data converting unit is smaller than the total number of gradations in data to be supplied into the drive data converting unit.

17. An image display apparatus according to claim 16, further comprising:

a signal processing circuit provided in a previous stage of the drive data conversion unit; and

a non-linear conversion unit provided in a previous stage of the signal processing circuit,

wherein the non-linear converting unit performs non-linear conversion for moderating non-linear conversion of a signal to be supplied into the non-linear conversion unit performed by a sender of the signal in order to obtain the signal.

18. An image display apparatus, comprising:

display elements, the display elements performing brightness gradation display by being applied with a modulated signal; and

a modulation circuit for generating a modulated signal modulated based on incoming drive data,

wherein the modulated circuit generates such modulated signal that the difference in display brightness generated when making the display elements display by two modulated signals obtained based on the drive data having one gradation difference in a first range of gradations, which is part of the entire range of gradations of the incoming drive data, becomes smaller than the difference in display brightness in a second range of gradations, which is different from the first range of gradations, and

wherein pulse width control is performed on the waveform of the modulated signal by the slot width, and

wherein crest value control is performed on crest values in each slot at least in n-stages from A1 to An, where n is an integer number equal to or larger than two, and 0<

A1<

A2<

. . . An, corresponding to the different ON-states of the display element, and

wherein the waveform of the modulated signal having the portion falling from the predetermined crest value Ak, where k is an integer number between 2 and n inclusive, rises to the predetermined crest value Ak via the respective crest values from Ak-1 to A1 at least one slot each in sequence, and

wherein a drive data converting unit for converting incoming data and outputting signals as the drive data is provided in a previous stage of the modulation circuit, and the total number of gradations of the signals outputted from the drive data converting unit is smaller than the total number of gradations in data to be supplied into the drive data converting unit.

19. An image display apparatus according to claim 18, further comprising:

a signal processing circuit provided in a previous stage of the drive data conversion unit; and

a non-linear conversion unit provided in a previous stage of the signal processing circuit,

wherein the non-linear converting unit performs non-linear conversion for moderating non-linear conversion of a signal to be supplied into the non-linear conversion unit performed by a sender of the signal in order to obtain the signal.

20. An image display apparatus, comprising:

display elements, the display elements performing brightness gradation display by being applied with a modulated signal; and

a modulation circuit for generating a modulated signal modulated based on incoming drive data,

wherein the modulated circuit generates such modulated signal that the difference in display brightness generated when making the display elements display by two modulated signals obtained based on the drive data having one gradation difference in a first range of gradations, which is part of the entire range of gradations of the incoming drive data, becomes smaller than the difference in display brightness in a second range of gradations, which is different from the first range of gradations,

wherein pulse width control is performed on the waveform of the modulated signal by the slot width and crest value control is performed on crest value in each slot at least in n-stages from A1 to An, where n is an integer number equal to or larger than two, and 0<

A1<

A2<

. . . An,

wherein the waveform which is increased in gradation with respect to the predetermined waveform of the modulated signal has such a shape that a unit waveform block which is determined by the slot width and the crest value An-An-1, . . . or A2-A1, or the difference in crest value between the crest value A1 and the crest value which is a drive threshold of the light-emitting element, is added by priority to a point where the maximum crest value Ak including k=1 is lower and the maximum crest values continue by priority,

wherein at least one of crest values is set to have a different display brightness from the case in which the crest values 0, A1, A2, . . . An-1, An are set to values to have a linear characteristic with respect to the display brightness, and

wherein a drive data converting unit for converting incoming data and outputting signals as the drive data is provided in a previous stage of the modulation circuit, and the total number of gradations of the signals outputted from the drive data converting unit is smaller than the total number of gradations in data to be supplied into the drive data converting unit.

21. An image display apparatus according to claim 20, wherein the modulation waveform is such that the waveform obtained by increasing one more gradation and adding the unit waveform block to the waveform whereof a number of slots with the maximum crest value Ak is S-2(k-1), where the maximum slot value represented by S has a shape in which the crest value of any slot out of the K+1st to the S-kth slots is changed from Ak to Ak+1.

22. An image display apparatus according to claim 20, further comprising:

a signal processing circuit is provided in a previous stage of the drive data conversion unit; and

a non-linear conversion unit provided in a previous stage of the signal processing circuit,

wherein the non-linear converting unit performs non-linear conversion for moderating non-linear conversion of a signal to be supplied into the non-linear conversion unit performed by a sender of the signal in order to obtain the signal.