Original reading apparatus, having a filter, for reading a color original

• US 5,166,784 A
• Filed: 12/14/1990
• Issued: 11/24/1992
• Est. Priority Date: 10/25/1985
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Matsuoka, Nobuo, Suda, Kenichi, Hasegawa, Shizuo
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): VU, KIM Y
• Application Number:
  US07/628,942
• Time in Patent Office: 711 Days
• Field of Search: 358/75, 358/80, 358/475, 358/494, 355/35, 355/37, 355/69, 355/70
• US Class Current: 358/500
• CPC Class Codes: H04N 1/48 Picture signal generators for halftone screening H04N1/52

Abstract

A color original reading apparatus includes a filter having a long-wavelength invisible radiation absorption filter and a long-wavelength invisible radiation reflection filter, or includes a spectral distribution correction filter arranged in an optical path from an original illumination light source to a color image sensor via an original.

Claims

1. An original reading apparatus, including:

light source means for illuminating an original;

color image sensor means for receiving light reflected by the original and outputting signals respectively corresponding to a plurality of types of color information; and

invisible radiation removing filter means, arranged in an optical path from said light source means to said color image sensor means via the original, for removing long-wavelength invisible radiation, said filter means being provided with a long-wavelength invisible radiation absorption filter and a long-wavelength invisible radiation reflection filter.

2. An apparatus according to claim 1, wherein said color image sensor means comprises a plurality of small photoelectric transducer elements and color separation filter means, both of which are formed in a light-receiving portion of said color image sensor means, said color separation filter means being provided with a plurality of types of small filters each having a different color separation characteristic, said photoelectric transducer elements having spectral sensitivity for both visible light and long-wavelength invisible radiation, said color separation filter means having transmissivity characteristics for both the visible light and the long-wavelength invisible radiation.

3. An apparatus according to claim 2, wherein said long-wavelength invisible radiation absorption filter and said long-wavelength invisible radiation reflection filter are integrally formed.

4. An apparatus according to claim 3, wherein said long-wavelength invisible radiation reflection filter is deposited on said long-wavelength invisible light absorption radiation.

5. An apparatus according to claim 2, further comprising a focusing optical system for focusing an image of an original onto said light-receiving portion of said color image sensor means, wherein said light source means comprises a halogen lamp, and said invisible radiation removing filter means is arranged between said color image sensor means and focusing optical system.

6. An original reading apparatus comprising:

light source means for illuminating an original;

color image sensor means for receiving light reflected by the original and producing outputting signals respectively corresponding to a plurality of types of color information, said color image sensor means being provided with small photoelectric transducer elements for producing said output signals and having spectral sensitivity for both visible light and long-wavelength invisible radiation, and with color separation filter means having transmissivity characteristics for both the visible light and the long-wavelength invisible radiation, said color separation filter means being provided with a plurality of types of small color filters each having a different color separation characteristic; and

filter means arranged in an optical path from said light source means to said color image sensor means via the original, said filter means having a long-wavelength invisible radiation removal filter and a spectral distribution correction filter, said spectral distribution correction filter correcting the spectral distribution of visible radiation directed toward said color image sensor means so that the level differences between output signals from said photoelectric transducer elements that correspond to a white original are reduced; and

wherein said long-wavelength invisible radiation removal filter comprises a transparent long-wavelength invisible radiation absorption plate and a thin long-wavelength invisible radiation reflection film formed on said transparent long-wavelength invisible radiation absorption plate.

7. An apparatus according to claim 6, wherein said long-wavelength invisible radiation removal filter and said spectral distribution correction filter are formed integrally.

8. An apparatus according to claim 7, further comprising a focusing optical system for focusing an image of the original onto said color image sensor means, wherein said filter means is arranged between said color image sensor and said focusing optical system.

9. An original reading apparatus, comprising:

a light source for illuminating an original;

a color image sensor for receiving light from the original and for outputting color information signals;

an array of short-focus image-forming elements for image-forming light obtained by irradiating the original by said light source on said color image sensor;

long-wavelength invisible radiation removing means for removing long-wavelength invisible radiation from said light source; and

spectral distribution correcting means for decreasing output level differences corresponding to each of the color information signals from said color image sensor;

wherein said long-wavelength invisible radiation removing means and said spectral distribution correcting means are arranged integrally and are disposed between said array of short-focus image-forming elements and said color image sensor.

10. An original reading apparatus according to claim 9, wherein said spectral distribution correcting means has a transmissivity of wavelength corresponding to each of the color image signals, in which the transmissivity of wavelength corresponding to a blue color of light is greater than the transmissivity of wavelength corresponding to a green color of light, and the transmissivity of wavelength of the green color of light is greater than the transmissivity of the wavelength corresponding to a red color of light.

11. An original reading apparatus according to claim 9, wherein the transmissivity of said spectral distribution correcting means is such that the output level differences from said color image sensor corresponding to blue color, green color and red color of light are substantially equal to zero.

12. An original reading apparatus according to claim 9, wherein said light source is a halogen lamp.

13. An original reading apparatus according to claim 9, wherein said long-wavelength invisible radiation removing means comprises a portion for absorbing infrared and a portion for reflecting near-infrared.

14. An original reading apparatus according to claim 9, wherein said color image sensor comprises a plurality of photoelectric transducer elements for producing said color information signals, said original reading apparatus further including a plurality of amplifiers for amplifying output signals from said photoelectric transducer elements respectively corresponding to the different colors, said amplifiers having an identical arrangement.

15. An original reading apparatus according to claim 13, wherein the portion for absorbing infrared light comprises a plate-like glass, and wherein the portion for reflecting the near-infrared light comprises an optical thin film vaporized onto said glass.

16. An original reading apparatus according to claim 9, wherein said spectral distribution correcting means is provided on a surface of said long-wavelength invisible radiation removing means.

17. An original reading apparatus according to claim 16, wherein said spectral distribution correcting means comprises an optical thin film vaporized onto said large-wavelength invisible radiation removing means.

18. An original reading apparatus, comprising:

a light source for illuminating an original;

a color image sensor for receiving light from the original and for outputting color information signals;

a long-wavelength invisible radiation removing filter for removing long-wavelength invisible radiation from said light source; and

a single spectral distribution correcting filter for decreasing output level differences corresponding to the color information signals from said color information sensor;

wherein said long-wavelength invisible radiation removing filter and said spectral distribution correcting filter are disposed in an optical path of the light from the original irradiated by said light source to said color image sensor and wherein said long-wavelength invisible radiation removing filter is disposed between said light source and said spectral distribution correcting filter in the light path.

19. An original reading apparatus according to claim 18, wherein said long-wavelength invisible radiation removing filter comprises a plate-like glass, and wherein said spectral distribution correcting filter is provided on a surface at a light outputting side of said plate-like glass.

20. An original reading apparatus according to claim 19, when said spectral distribution correcting filter comprises an optical thin film vaporized onto said plate-like glass.

21. An original reading apparatus according to claim 18, wherein said light source comprises a halogen lamp.

22. An original reading apparatus, comprising:

a light source for illuminating an original;

a color image sensor for receiving light from the original and for outputting color information signals;

long-wavelength invisible radiation removing means for removing long-wavelength invisible radiation from said light source; and

spectral distribution correcting means for decreasing output level differences corresponding to each of the color information signals from said color image sensor,

wherein said long-wavelength invisible radiation removing means and said spectral distribution correcting means are arranged integrally.

23. An original reading apparatus according to claim 22, wherein said spectral distribution correcting means is provided on a surface of said long-wavelength invisible radiation removing means.

24. An original reading apparatus according to claim 23, wherein said spectral distribution correcting means comprises an optical thin film vaporized onto said large-wavelength invisible radiation removing means.

25. An original reading apparatus according to claim 23, wherein said color information signals are signals representing blue, green and red.