Image forming apparatus

• US 6,021,223 A
• Filed: 10/31/1997
• Issued: 02/01/2000
• Est. Priority Date: 11/01/1996
• Status: Expired due to Term

• Current Assignee: Hamamatsu Photonics KK, Technical University of Denmark
• Original Assignee: Hamamatsu Photonics KK, Risø National Laboratory
• Inventors: Toyoda, Haruyoshi, Gluckstad, Jesper
• Primary Examiner(s): Kelley, Christopher S.
• Application Number:
  US08/962,446
• Time in Patent Office: 823 Days
• Field of Search: 382/210, 382/211, 382/214, 359/237, 359/240
• US Class Current: 382/214
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: G02B 27/52 Phase contrast optics in microscopes G02B21/14
• CPC Class Codes: G03H 2225/25 Optically addressed SLM [OA-SLM]
• CPC Class Codes: G03H 2225/32 Phase only
• CPC Class Codes: G06E 3/00 Devices not provided for in group G06E1/00, e.g. for processing analogue or hybrid data
• CPC Class Codes: G06E 3/005 using electro-optical or opto-electronic means

Abstract

An image H(x, y) for displaying a target image G(x, y) is displayed on a liquid-crystal display panel and illumination light from an illumination light source is made to pass therethrough to form an image on a PALSLM. Read light hν is radiated to the PALSLM and a phase-modulated light image α(x, y) read out of the PALSLM is subjected to Fourier transform by a lens. A phase contrast filter gives a predetermined phase shift to only the zero-order light component of Fourier light image α_f (x, y). The phase-shifted light image is subjected to inverse Fourier transform by a lens to project an output image O(x, y) to an output plane. A light image O'"'"'(x, y) branched by a beam sampler is picked up by a pickup device and an evaluation value calculating unit evaluates conformity between the image O(x, y) and the image G(x, y). A control unit performs feedback control of optical characteristics of the illumination light source, PALSLM, and phase contrast filter, based on the evaluation result.

Claims

1. An image forming apparatus for forming a two-dimensional optical image, based on electric image information, comprising:

an operation optical system, said operation optical system having at least

a light transmission type display device for, based on said electric image information, displaying a two-dimensional input image corresponding thereto,

an illumination device for radiating illumination light to the display image on said display device,

read light generating means for emitting coherent read light,

optical address type two-dimensional spatial light modulating means irradiated by a two-dimensional intensity light image formed according to said two-dimensional input image by said illumination light transmitted by said display device, said spatial light modulating means phase-modulating the read light radiated from said read light generating means according to a spatial light intensity distribution of the two-dimensional intensity light image to output a two-dimensional phase-modulated light image having a spatial light intensity distribution,

a Fourier lens for converting said phase-modulated light image to a Fourier light image,

a phase contrast filter, provided on a Fourier plane of said Fourier lens, for phase-shifting a zero-order light component of said Fourier light image, and

an inverse Fourier lens for undergoing inverse Fourier transform of said Fourier light image to output said optical image; and

operation controlling means for applying a desired ideal image to be formed as said optical image to a theoretical characteristic of said operation optical system, thereby reversely calculating said electric image information.

2. An image forming apparatus according to claim 1, wherein said Fourier lens and inverse Fourier lens are lenses for two-dimensional Fourier transform.

3. An image forming apparatus according to claim 1, wherein said Fourier lens is a first lens for one-dimensional Fourier transform, said inverse Fourier lens is a second lens for one-dimensional inverse Fourier transform, and a Fourier transform plane of said first lens and an inverse Fourier transform plane of said second lens are arranged in a same orientation.

4. An image forming apparatus according to claim 3, wherein a third lens having the same optical characteristics as said first lens is positioned perpendicular to said first lens.

5. An image forming apparatus according to claim 1, wherein said phase contrast filter is a transmission type filter for transmitting said Fourier light image.

6. An image forming apparatus according to claim 1, wherein said phase contrast filter is a reflection type filter for reflecting said Fourier light image.

7. An image forming apparatus according to claim 1, wherein said phase contrast filter has such structure that a dielectric multilayer film having a predetermined light transmittance is interposed between a light modulating material layer biased at a predetermined voltage and a photoconductor layer and that said Fourier light image is made incident to said light modulating material layer and is reflected by the dielectric multilayer film to be outputted, and

wherein a part of the zero-order light component of said Fourier light image transmitted by said dielectric multilayer film changes an electric characteristic of said photoconductor layer, thereby changing a birefringence distribution of said light modulating material layer, and said light modulating material layer phase-shifts and outputs said Fourier light image reflected by the dielectric multilayer film.

8. An image forming apparatus according to claim 1, wherein said operation controlling means comprises:

evaluation value calculating means for observing the optical image outputted from said inverse Fourier lens to evaluate conformity between said optical image and said desired ideal image, and

variable control means for variably controlling an optical characteristic of said operation optical system, based on a result of said evaluation by said evaluation value calculating means.

9. An image forming apparatus for forming a two-dimensional optical image, based on electric image information, comprising:

an operation optical system, said operation optical system having at least

a self-emission type display device for, based on said electric image information, radiating a two-dimensional intensity image corresponding thereto,

read light generating means for emitting coherent read light,

an optical address type two-dimensional spatial light modulator irradiated by the two-dimensional intensity light image produced by said display device, said spatial light modulator phase-modulating the read light radiated from said read light generating means according to a spatial light intensity distribution of the two-dimensional intensity light image to output a phase-modulated light image having a spatial light intensity distribution,

a Fourier lens for converting said phase-modulated light image to a Fourier light image,

a phase contrast filter, provided on a Fourier plane of said Fourier lens, for phase-shifting a zero-order light component of said Fourier light image, and

an inverse Fourier lens for undergoing inverse Fourier transform of said Fourier light image to output said optical image; and

operation controlling means for applying a desired ideal image to be formed as said optical image to a theoretical characteristic of said operation optical system, thereby reversely calculating said image information.

10. An image forming apparatus according to claim 9, wherein said Fourier lens and inverse Fourier lens are lenses for two-dimensional Fourier transform.

11. An image forming apparatus according to claim 9, wherein said Fourier lens is a first lens for one-dimensional Fourier transform, said inverse Fourier lens is a second lens for one-dimensional inverse Fourier transform, and a Fourier transform plane of said first lens and an inverse Fourier transform plane of said second lens are arranged in a same orientation.

12. An image forming apparatus according to claim 11, wherein a third lens having the same optical characteristics as said first lens is positioned perpendicular to said first lens.

13. An image forming apparatus according to claim 9, wherein said phase contrast filter is a transmission type filter for transmitting said Fourier light image.

14. An image forming apparatus according to claim 9, wherein said phase contrast filter is a reflection type filter for reflecting said Fourier light image.

15. An image forming apparatus according to claim 9, wherein said phase contrast filter has such structure that a dielectric multilayer film having a predetermined light transmittance is interposed between a light modulating material layer biased at a predetermined voltage and a photoconductor layer and that said Fourier light image is made incident to said light modulating material layer and is reflected by the dielectric multilayer film to be outputted, and

wherein a part of the zero-order light component of said Fourier light image transmitted by said dielectric multilayer film changes an electric characteristic of said photoconductor layer, thereby changing a birefringence distribution of said light modulating material layer, and said light modulating material layer phase-shifts and outputs said Fourier light image reflected by the dielectric multilayer film.

16. An image forming apparatus according to claim 9, wherein said operation controlling means comprises:

evaluation value calculating means for observing the optical image outputted from said inverse Fourier lens to evaluate conformity between said optical image and said desired ideal image, and

variable control means for variably controlling an optical characteristic of said operation optical system, based on a result of said evaluation by said evaluation value calculating means.

17. An image forming apparatus for forming an optical image, based on electric image information, comprising:

an operation optical system, said operation optical system having at least

read light generating means for emitting coherent read light,

an electrical address type two-dimensional spatial light modulator for phase-modulating said read light according to said electric image information to output a two-dimensional phase-modulated light image having a spatial light intensity distribution,

a Fourier lens for undergoing Fourier transform of said phase-modulated light image to a Fourier light image,

a phase contrast filter, provided on a Fourier plane of said Fourier lens, for phase-shifting a zero-order light component of said Fourier light image, and

an inverse Fourier lens for undergoing inverse Fourier transform of said Fourier light image to output said optical image; and

operation controlling means for applying a desired ideal image to be formed as said optical image to a theoretical characteristic of said operation optical system, thereby reversely calculating said image information.

18. An image forming apparatus according to claim 17, wherein said two-dimensional spatial light modulator is a liquid-crystal display panel.

19. An image forming apparatus according to claim 17, wherein said Fourier lens and inverse Fourier lens are lenses for two-dimensional Fourier transform.

20. An image forming apparatus according to claim 17, wherein said Fourier lens is a first lens for one-dimensional Fourier transform, said inverse Fourier lens is a second lens for one-dimensional inverse Fourier transform, and a Fourier transform plane of said first lens and an inverse Fourier transform plane of said second lens are arranged in a same orientation.

21. An image forming apparatus according to claim 20, wherein a third lens having the same optical characteristics as said first lens is positioned perpendicular to said first lens.

22. An image forming apparatus according to claim 17, wherein said phase contrast filter is a transmission type filter for transmitting said Fourier light image.

23. An image forming apparatus according to claim 17, wherein said phase contrast filter is a reflection type filter for reflecting said Fourier light image.

24. An image forming apparatus according to claim 17, wherein said phase contrast filter has such structure that a dielectric multilayer film having a predetermined light transmittance is interposed between a light modulating material layer biased at a predetermined voltage and a photoconductor layer and that said Fourier light image is made incident to said light modulating material layer and is reflected by the dielectric multilayer film to be outputted, and

wherein a part of the zero-order light component of said Fourier light image transmitted by said dielectric multilayer film changes an electric characteristic of said photoconductor layer, thereby changing a birefringence distribution of said light modulating material layer, and said light modulating material layer phase-shifts and outputs said Fourier light image reflected by the dielectric multilayer film.

25. An image forming apparatus according to claim 17, wherein said operation controlling means comprises:

evaluation value calculating means for observing the optical image outputted from said inverse Fourier lens to evaluate conformity between said optical image and said desired ideal image, and

variable control means for variably controlling an optical characteristic of said operation optical system, based on a result of said evaluation by said evaluation value calculating means.