Focus error detecting apparatus

Optical: systems and elements – Holographic system or element – Using a hologram as an optical element

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359569, 2502015, 369109, 369122, G02B 532, G11B 712, G01J 100

Patent

active

052334449

ABSTRACT:
A focus error detecting apparatus in which a light emitting and receiving element including a light emitting portion and light receiving portions all of which are formed in a common semiconductor substrate, a hologram element diffracts a light beam reflected by an object to generate plus and minus first-order diffraction light beams and to introduce an astigmatism into the plus and minus first-order diffraction light beams such that shapes of spots of the diffraction light beams formed on the light receiving portions of the light emitting and receiving element vary into substantially reverse directions to each other, and a focusing condition is detected in accordance with outputs of the light receiving portions. Therefore, in this apparatus, positioning adjustment of the light receiving portions with respect to the light emitting portion is not necessary, and thus a number of the adjusting process can be remarkably decreased and the cost for manufacturing the apparatus can be reduced. Furthermore, the focusing condition can be detected with high accuracy.

REFERENCES:
patent: 4804835 (1989-02-01), Ando
patent: 4857719 (1989-08-01), Ando
patent: 4858215 (1989-08-01), Yano et al.
patent: 4894815 (1990-01-01), Yamanaka
patent: 4945529 (1990-07-01), Ono et al.
M. Hirose, et al., "Monolithically Integrated GaAlAs Laser/Detector Array", Denishi Tsushin Gakkai OQE86 1-14, vol. 86, No. 8, pp. 73-77, Apr. 1986.

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