OPTICAL PROJECTION SYSTEM WITH ENHANCED COLOR RESOLUTION

• US 3,585,283 A
• Filed: 09/24/1969
• Issued: 06/15/1971
• Est. Priority Date: 09/24/1969
• Status: Expired due to Term

• Current Assignee: Michael Graser Jr
• Original Assignee: Michael Graser Jr
• Inventors: Graser, Michael Jr.
• Application Number:
  US04/860,532
• Time in Patent Office: 629 Days
• US Class Current: 348/764
• CPC Class Codes: H04N 9/3108 by using a single electronic spatial light modulator

Abstract

In light value projection apparatus employing a medium deformable by a scanning electron beam into a plurality of diffraction gratings, each grating controlling the light of a respective primary color, improved resolution of magenta light is achieved by furnishing only red and blue video signals below a selected cutoff frequency to red and blue modulators respectively, and by furnishing only the red and blue video signals above this frequency or the luminance signals above this frequency, to a magenta modulator. The magenta modulator carrier frequency is selected to exceed the beat frequency between the red and blue diffraction gratings. The red, blue and magenta modulator output signals are combined bore being applied to electron beam deflection plates.

Claims

1. In an optical projection system wherein an image to be displayed in color is formed by impingement of an electron beam on a light modulating medium, said electron beam being neglected over the surface of said medium in accordance with three separate signals representing three primary colors respectively, apparatus for improving resolution of the display image, said apparatus comprising:

means generating four independent carrier frequencies;

first modulating means modulating a first one of said carrier frequencies with a first one of said three separate signals;

first electron beam deflection means coupled to said first modulating means for deflecting said electron beam in accordance with the modulated first carrier frequency;

second modulating means modulating a second one of said carrier frequencies with the second one of said three separate signals whenever said second one of said three separate signals is below a first predetermined frequency;

third modulating means modulating the third one of said carrier frequencies with the third one of said three separate signals whenever said third one of said three separate signals is below a second predetermined frequency, said second predetermined frequency being substantially equal to said first predetermined frequency;

fourth modulating means modulating the fourth one of said carrier frequencies with a fourth signal of frequency whenever either of said second and third ones of said three separate signals is above said first and second predetermined frequency, respectively; and

second electron beam deflection means coupled jointly to said second, third and fourth modulating means for deflecting said electron beam in accordance with the modulated second, third and fourth carrier frequencies.

2. The system of claim 1 including means coupling said second One of said three separate signals to said fourth modulating means whenever the frequency of the second signal exceeds said first predetermined frequency, and means coupling said third one of said three separate signals to said fourth modulating means whenever the frequency of the third signal exceeds said second predetermined frequency.

3. The system of claim 2 wherein said means coupling said second one of said three separate signals to said fourth modulating means and said means coupling said third one of said three separate signals to said fourth modulating means each comprises a frequency diplexer.

4. The system of claim 1 including a first low-pass filter furnishing said second one of said three separate signals to said second modulating means, a second low-pass filter furnishing the third one of said three separate signals to said third modulating means, and a high pass filter furnishing said fourth signal to said fourth modulating means.

5. The system of claim 4 wherein said fourth signal comprises a luminance signal.

6. In an optical projection system wherein an image to be displayed in color is produced by diffraction gratings formed in a light modulating medium in accordance with three separate signals representing three primary colors respectively, a method for improving resolution of the displayed image, said method comprising:

forming a first diffraction grating in said light modulating medium in accordance with a first one of said three separate signals;

forming second diffraction grating in said light modulating medium in accordance with a second one of said three separate signals whenever said second one of said three separate signals is within a first predetermined frequency range;

forming a third diffraction grating in said light modulating medium in accordance with the third one of said three separate signals whenever said third one of said separate three signals is within a second predetermined frequency range substantial coinciding with said first frequency range, said second and third diffraction gratings producing a beat frequency grating therebetween; and

forming a fourth diffraction grating in said light modulating medium in accordance with a fourth signal of frequency above the frequency of said first and second predetermined frequency ranges whenever either of said second and third ones of said three separate signals is above the frequencies of said first and second predetermined frequency range, respectively, said fourth diffraction grating being of higher grating frequency than said beat frequency grating.

7. In an optical projection system wherein an image to be displayed in color is produced by diffraction gratings formed in a light modulating medium by three separate signals representing three primary colors respectively, said gratings being formed by impingement of an electron beam on said medium, a method for improving resolution of the displayed image, said method comprising:

deflecting said electron beam along a first direction in accordance with a first one of said three separate signals so as to form a first diffraction grating in said light modulating medium;

deflecting said electron beam along a second direction in accordance with a second one of said three separate signals whenever said second one of said three separate signals is below a predetermined frequency so as to form a second diffraction grating in said light modulating medium;

deflecting said electron beam along said second direction in accordance with the third one of said three separate signals whenever said third one of said three separate signals is below said predetermined frequency so as to form a third diffraction grating in said light modulating medium, said second and third diffraction gratings producing a beat frequency grating therebetween; and

deflecting said electron beam along said second direction in accordance with a fourth signal of frequency above said predetermined frequency whenever either of said second And third ones of said three separate signals is above said predetermined frequency so as to form a fourth diffraction grating in said light modulating medium, said fourth diffraction grating being of higher grating frequency than said beat frequency grating.

8. The method of claim 7 including the step of deriving said fourth signal from said second and third ones of said three separate signals.

9. The method of claim 7 wherein said fourth signal comprises a luminance signal.