Abstract

A color-temperature compensating system with an electrically controllable liquid-crystal filter and a color sensor mounted on a video camera has been developed for color image sensing. The filter contains two guest–host liquid-crystal devices with dichroic dyes that have strong light absorption for shorter-wavelength light; two devices are necessary because of the spectral difference between the sun and an incandescent lamp as light sources. The filter’s absorption is continuously controlled by the voltage applied to the filter. Because the filter is driven according to spectral information about the illumination detected by the color sensor, the color balance of the video image to be sensed can be compensated automatically and rapidly. This is especially useful for video image shooting in which a video camera experiences changes in illumination color temperatures.

© 2001 Optical Society of America

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References

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  1. J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).
  2. G. H. Heilmeir, L. A. Zanoni, “Guest–host interactions in nematic liquid crystals: a new electro-optic effect,” Appl. Phys. Lett. 13, 91–92 (1968).
    [CrossRef]
  3. H. Seki, T. Uchida, Y. Shibata, “Dichroic dyes for guest–host liquid-crystal cells,” Mol. Cryst. Liq. Cryst. 138, 349–365 (1986).
    [CrossRef]
  4. T. Uchida, H. Seki, C. Shishido, M. Wada, “Guest–host interactions in nematic liquid crystals with negative dielectric anisotropy,” IEEE Trans. Electron Devices ED-26, 1373–1374 (1979).
    [CrossRef]
  5. T. Uchida, H. Seki, C. Shishido, M. Wada, “Bright dichroic guest–host LCDs without a polarizer,” Proc. Soc. Inf. Disp. 22, 41–46 (1981).
  6. P. Sheng, “Introduction to the elastic continuum theory of liquid crystals,” RCA Rev. 35, 408–432 (1974).
  7. F. C. Frank, “On the theory of liquid crystals,” Discuss. Faraday Soc. 25, 19–28 (1958).
    [CrossRef]

2000 (1)

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

1986 (1)

H. Seki, T. Uchida, Y. Shibata, “Dichroic dyes for guest–host liquid-crystal cells,” Mol. Cryst. Liq. Cryst. 138, 349–365 (1986).
[CrossRef]

1981 (1)

T. Uchida, H. Seki, C. Shishido, M. Wada, “Bright dichroic guest–host LCDs without a polarizer,” Proc. Soc. Inf. Disp. 22, 41–46 (1981).

1979 (1)

T. Uchida, H. Seki, C. Shishido, M. Wada, “Guest–host interactions in nematic liquid crystals with negative dielectric anisotropy,” IEEE Trans. Electron Devices ED-26, 1373–1374 (1979).
[CrossRef]

1974 (1)

P. Sheng, “Introduction to the elastic continuum theory of liquid crystals,” RCA Rev. 35, 408–432 (1974).

1968 (1)

G. H. Heilmeir, L. A. Zanoni, “Guest–host interactions in nematic liquid crystals: a new electro-optic effect,” Appl. Phys. Lett. 13, 91–92 (1968).
[CrossRef]

1958 (1)

F. C. Frank, “On the theory of liquid crystals,” Discuss. Faraday Soc. 25, 19–28 (1958).
[CrossRef]

Aida, T.

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

Frank, F. C.

F. C. Frank, “On the theory of liquid crystals,” Discuss. Faraday Soc. 25, 19–28 (1958).
[CrossRef]

Fujikake, H.

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

Heilmeir, G. H.

G. H. Heilmeir, L. A. Zanoni, “Guest–host interactions in nematic liquid crystals: a new electro-optic effect,” Appl. Phys. Lett. 13, 91–92 (1968).
[CrossRef]

Iwashita, K.

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

Kawakita, M.

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

Kikuchi, H.

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

Seki, H.

H. Seki, T. Uchida, Y. Shibata, “Dichroic dyes for guest–host liquid-crystal cells,” Mol. Cryst. Liq. Cryst. 138, 349–365 (1986).
[CrossRef]

T. Uchida, H. Seki, C. Shishido, M. Wada, “Bright dichroic guest–host LCDs without a polarizer,” Proc. Soc. Inf. Disp. 22, 41–46 (1981).

T. Uchida, H. Seki, C. Shishido, M. Wada, “Guest–host interactions in nematic liquid crystals with negative dielectric anisotropy,” IEEE Trans. Electron Devices ED-26, 1373–1374 (1979).
[CrossRef]

Sheng, P.

P. Sheng, “Introduction to the elastic continuum theory of liquid crystals,” RCA Rev. 35, 408–432 (1974).

Shibata, Y.

H. Seki, T. Uchida, Y. Shibata, “Dichroic dyes for guest–host liquid-crystal cells,” Mol. Cryst. Liq. Cryst. 138, 349–365 (1986).
[CrossRef]

Shishido, C.

T. Uchida, H. Seki, C. Shishido, M. Wada, “Bright dichroic guest–host LCDs without a polarizer,” Proc. Soc. Inf. Disp. 22, 41–46 (1981).

T. Uchida, H. Seki, C. Shishido, M. Wada, “Guest–host interactions in nematic liquid crystals with negative dielectric anisotropy,” IEEE Trans. Electron Devices ED-26, 1373–1374 (1979).
[CrossRef]

Takizawa, K.

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

Uchida, T.

H. Seki, T. Uchida, Y. Shibata, “Dichroic dyes for guest–host liquid-crystal cells,” Mol. Cryst. Liq. Cryst. 138, 349–365 (1986).
[CrossRef]

T. Uchida, H. Seki, C. Shishido, M. Wada, “Bright dichroic guest–host LCDs without a polarizer,” Proc. Soc. Inf. Disp. 22, 41–46 (1981).

T. Uchida, H. Seki, C. Shishido, M. Wada, “Guest–host interactions in nematic liquid crystals with negative dielectric anisotropy,” IEEE Trans. Electron Devices ED-26, 1373–1374 (1979).
[CrossRef]

Umeda, S.

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

Wada, M.

T. Uchida, H. Seki, C. Shishido, M. Wada, “Bright dichroic guest–host LCDs without a polarizer,” Proc. Soc. Inf. Disp. 22, 41–46 (1981).

T. Uchida, H. Seki, C. Shishido, M. Wada, “Guest–host interactions in nematic liquid crystals with negative dielectric anisotropy,” IEEE Trans. Electron Devices ED-26, 1373–1374 (1979).
[CrossRef]

Yonai, J.

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

Zanoni, L. A.

G. H. Heilmeir, L. A. Zanoni, “Guest–host interactions in nematic liquid crystals: a new electro-optic effect,” Appl. Phys. Lett. 13, 91–92 (1968).
[CrossRef]

Appl. Phys. Lett. (1)

G. H. Heilmeir, L. A. Zanoni, “Guest–host interactions in nematic liquid crystals: a new electro-optic effect,” Appl. Phys. Lett. 13, 91–92 (1968).
[CrossRef]

Discuss. Faraday Soc. (1)

F. C. Frank, “On the theory of liquid crystals,” Discuss. Faraday Soc. 25, 19–28 (1958).
[CrossRef]

IEEE Trans. Electron Devices (1)

T. Uchida, H. Seki, C. Shishido, M. Wada, “Guest–host interactions in nematic liquid crystals with negative dielectric anisotropy,” IEEE Trans. Electron Devices ED-26, 1373–1374 (1979).
[CrossRef]

Mol. Cryst. Liq. Cryst. (1)

H. Seki, T. Uchida, Y. Shibata, “Dichroic dyes for guest–host liquid-crystal cells,” Mol. Cryst. Liq. Cryst. 138, 349–365 (1986).
[CrossRef]

Proc. Soc. Inf. Disp. (1)

T. Uchida, H. Seki, C. Shishido, M. Wada, “Bright dichroic guest–host LCDs without a polarizer,” Proc. Soc. Inf. Disp. 22, 41–46 (1981).

RCA Rev. (1)

P. Sheng, “Introduction to the elastic continuum theory of liquid crystals,” RCA Rev. 35, 408–432 (1974).

Trans. Inst. Electron. Inf. Commun. Eng. (1)

J. Yonai, H. Fujikake, T. Aida, H. Kikuchi, M. Kawakita, K. Takizawa, K. Iwashita, S. Umeda, “Color balancing filters using liquid crystal for image pickup,” Trans. Inst. Electron. Inf. Commun. Eng. J83-C, 415–421 (2000).

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Figures (16)

Fig. 1
Fig. 1

Principle of compensating the color temperature of a video image with the LC filter.

Fig. 2
Fig. 2

Normalized radiation spectra from a blackbody of different temperatures.

Fig. 3
Fig. 3

Schematic diagram of the LC filter with dichroic dyes: (a) and (b) without and with a sufficient applied voltage, respectively.

Fig. 4
Fig. 4

Transmission spectra of light from the LC devices containing the different dyes.

Fig. 5
Fig. 5

Transmission spectra of light from the LC filter when nonpolarized light is incident on it.

Fig. 6
Fig. 6

Simulated LC molecular alignment in the LC device driven by various applied voltages.

Fig. 7
Fig. 7

Dependence of the calculated tilt angle of LC molecules on the distance from the substrate.

Fig. 8
Fig. 8

Chromaticity diagram of xenon lamp light through the LC filter.

Fig. 9
Fig. 9

Color temperature of light transmitted from the LC filter versus various applied voltages.

Fig. 10
Fig. 10

Block diagram of the color sensor and control unit for driving the LC filter.

Fig. 11
Fig. 11

Spectral sensitivity of the photosensors in the color sensor.

Fig. 12
Fig. 12

Appearance of the two photosensors attached to the color sensor unit.

Fig. 13
Fig. 13

Dependence of output voltage of the photodiodes on the illuminance.

Fig. 14
Fig. 14

Appearance of the fabricated color sensor and control unit mounted on a video camera.

Fig. 15
Fig. 15

Appearance of the LC filter: (a) and (b) without and with an applied voltage of 5Vrms, respectively.

Fig. 16
Fig. 16

Experimental results for color-temperature compensation of the developed system. (a) Video image under indoor incandescent light. (b) and (c) Images captured under solar light without and with color compensation, respectively.

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