Claims
- 1. Apparatus for recording information from an electrical signal onto a scanned medium comprising:
- means for providing a beam of high intensity light;
- means for modulating the light beam in accordance with the information content of an electrical signal;
- optical means for imaging said modulated beam to a spot in a focal plane at the surface of a light sensitive medium at a predetermined distance from said optical means;
- a multifaceted polygon having reflective facets for reflecting the modulated beam incident to it onto said medium and means for rotating said polygon such that the reflected light is scanned in successive traces across said medium;
- said optical means including a first lens, having power in one optical plane and substantially no power in the other plane, positioned in the optical path of said light beam between said light providing means and said polygon with its power plane substantially perpendicular to the axis of rotation of said polygon for providing a predetermined distribution of light incident upon said polygon; and
- a second lens, having power in one optical plane and substantially no power in the other plane, positioned in the optical path of the imaged beam between said optical means and said medium, with its power plane substantially parallel to the axis of rotation of said polygon, the aperture of said second lens being in convolution with the aperture of said optical means such that runout errors are corrected.
- 2. The apparatus as defined in claim 1 wherein said first and second lenses are cylindrical lenses.
- 3. The apparatus as defined in claim 2 wherein said light providing means is a finite source and the focal length of said first cylindrical lens is approximately equal to W.sub.h /tan .THETA., wherein W.sub.h is the horizontal size of the spot at said medium and .THETA. is the angular subtend of the emitting area of said light providing means.
- 4. The apparatus as defined in claim 2 wherein said light source is a laser which emits beam of collimated light of substantially uniform intensity.
- 5. The apparatus as defined in claim 4 wherein the focal length f.sub.o of said first cylindrical lens is approximately equal to h W.sub.h /2.44 .lambda. , where h is the diameter of the laser light beam directed at the focal point of said first lens, W.sub.h is the horizontal size of the spot at said medium, and .lambda. is the wavelength of the laser light beam.
- 6. The apparatus as defined in claim 4 wherein the focal length of said first cylindrical lens is approximately equal to h W.sub.h /2.0.lambda., where h is the diameter of the laser beam directed at the focal point of said first lens, W.sub.h is the horizontal spot size at said medium, and .lambda. is the wavelength of the laser light beam.
- 7. The apparatus as defined in claim 6 wherein said cylindrical lens has a focal number (f/number)2 .congruent. b'/[ 2 tan .beta. (b' + b)], where b is the distance of said lens from the origin of runout error, b' is the distance of said lens from said focal plane, and .beta. is the angular measure of runout error.
- 8. Apparatus for recording information from an electrical signal onto a scanned medium comprising:
- means for providing a beam of high intensity light;
- means for modulating the light beam in accordance with the information content of an electrical signal;
- first optical means, having power in one optical plane and substantially no power in the other plane, for expanding said modulated beam;
- second optical means in convolution with said first optical means, said second optical means defining a finite conjugate imaging system for imaging said expanded beam to a spot in a focal plane having a large depth of focus coextensive with the surface of a light sensitive medium at a predetermined distance from said second optical means;
- a multifaceted polygon having reflective facets positioned in the optical path of said imaged beam such that certain of said facets are illuminated to reflect said beam toward said medium;
- said first optical means being positioned with its power plane substantially perpendicular to the axis of rotation of said polygon;
- means for rotating said polygon such that said reflected beam is scaned through a scan angle to provide successive spot scaning traces across said medium, and
- third optical means, having power in one optical plane and substantially no power in the other plane, in the optical path of the imaged beam between said second optical means and said medium with its power plane substantially parallel to the axis of rotation of said polygon such that runout errors are corrected.
- 9. The apparatus as defined in claim 8 wherein said light source is a laser which emits a beam of collimated light of substantially uniform intensity.
- 10. The apparatus as defined in claim 9 wherein said first optical means is a first cylindrical lens and said third optical means is a second cylindrical lens.
- 11. The apparatus as defined in claim 10 wherein the focal length f.sub.o of said first cylindrical lens is approximately equal to h W.sub.h /2.44 .lambda., where h is the diameter of the laser light beam directed at the focal point of said first lens, W.sub.h is the horizontal size of the spot at said medium, and .lambda. is the wavelength of the laser light beam.
- 12. The apparatus as defined in claim 10 where the focal length f.sub.o of said first cylindrical lens is approximately equal to h W.sub.h /2.0 .lambda., where h is the diameter of the laser light beam directed at the focal point of said first lens, W.sub.h is the horizontal spot size of the spot at said medium and .lambda. is the wavelength of the laser light beam.
- 13. The apparatus as defined in claim 12 wherein said second optical means has a focal length f.sub.1 = (D.sub.T)/M+1/M+2 where D.sub.T is the distance of said first cylindrical lens from said medium and M is the desired spot size at the medium divided by W.sub.h.
- 14. A flying spot scanning sysem for recording information from a video signal onto a scanned medium comprising:
- a laser for emitting a beam of collimated light of substantially uniform, high intensity;
- means for modulating the light beam in accordance with the information content of a video signal represented by a stream of binary digits;
- means for focusing said beam to a spot upon the surface of a light sensitive medium;
- a multifaceted polygon having reflective facets positioned in the optical path of said focused beam such that certain of said facets are illuminated to reflect said beam toward said medium;
- said focusing means including a first cylindrical lens positioned with its power plane substantially perpendicular to the axis of rotation of said polygon;
- means for rotating said polygon such that said reflected beam is scanned through a scan angle to provide successive spot scanning traces across said medium; and
- a second cylindrical lens positioned in the optical path of said focused beam between said polygon and said medium with its power plane substantially parallel to the axis of rotation of said polygon such that runout errors are corrected.
- 15. The apparatus as defined in claim 14 wherein the focal length f.sub.o of said first cylindrical lens is approximately equal to h W.sub.h /2.44 .lambda., where h is the diameter of the laser light beam directed at the focal point of said first lens, W.sub.h is the horizontal size of the spot at said medium, and .lambda. is the wavelength of the laser light beam.
- 16. The apparatus as defined in claim 14 wherein the focal length f.sub.o of said first cylindrical lens is approximately equal to h W.sub.h /2.0 .lambda., where h is the diameter of the laser light beam directed at the focal point of said first lens, W.sub.h is the horizontal size of the spot at said medium, and .lambda. is the wavelength of the laser light beam.
- 17. The apparatus as defined in claim 16 wherein said cylindrical lens is positioned at a distance from said medium approximately equal to the focal length f.sub.2 of said lens.
RELATED APPLICATION
This application is a continuation application of application Ser. No. 426,890, filed Dec. 20, 1973 now abandoned.
US Referenced Citations (4)
Continuations (1)
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Number |
Date |
Country |
Parent |
426890 |
Dec 1973 |
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