Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1990-09-10
1991-05-28
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369 4424, G01J 120
Patent
active
050197010
ABSTRACT:
An automatic focusing apparatus having an objective lens for forming a beam from a semiconductor laser as a spot image on an image subjecting face, a driving unit for driving the objective lens in a direction parallel to an optical axis thereof, a beam splitter disposed between the semiconductor laser and the objective lens, a pair of grids for generating a moire image displaced in a travelling path of a beam returning from the image subjecting face and reflected by an inclined prism face of the beam splitter, a photo detector for detecting the moire image generated by the grids and an control unit for evaluating a focusing error based on a variation in the moire image pattern and for controlling the driving unit so as to correct the focusing error. The first grid and the second grid are interspaced in parallel to each other along a beam axis and angularly displaced from each other about the beam axis.
REFERENCES:
patent: 3245307 (1966-04-01), De Lang
patent: 3962720 (1976-06-01), Braat
patent: 4475182 (1984-10-01), Hosaka
patent: 4503324 (1985-03-01), Yokota
patent: 4651314 (1987-03-01), Yoshikawa et al.
Focusing Errors in a Collimating Lens or Mirror: Use of a Morie Technique, Fouere et al., Applied Optics, vol. 13, No. 6, 1974.
Japan. J. Appl. Phys. 9 (1970) 1011-1012: "Theoretical Interpretation of Moire Pattern Two Grids of Parallel Lines".
Mino Masayuki
Yagoto Mitsutoshi
Minolta Camera Kabushiki Kaisha
Nelms David C.
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