Automatic focusing system

Details Automatic focusing system Automatic focusing system

1988-11-10

1990-04-24

Ng, Jin F.

Facsimile and static presentation processing

Facsimile

Recording apparatus

250201WD, H04N 5232

Patent

active

049204203

ABSTRACT:
There is provided an automatic focusing system which is used in a video camera or the like. A master lens is finely vibrated and moved by using a moving mechanism consisting of a stepping motor and a lead screw. A speed control circuit to set a moving speed of the master lens is provided. The moving speed of the master lens is set by an output signal of the speed control circuit and the master lens is moved by the moving mechanism. The moving speed of the master lens is optimally controlled and the out-of-step phenomenon in the stepping motor is eliminated. Since the master lens is accurately moved, the focusing operation is executed at a high accuracy. In addition, the influence by the unnecessary vibration (ringing) which is caused by the sudden change in moving speed of the master lens is eliminated. Therefore, since the master lens normally performs a predetermined micro vibration, the correct focusing can be accurately discriminated. Further, when a change in amount of the high frequency component of a video signal is large, since the moving speed of the master lens increases, the operating time until the correct focus is obtained is reduced.

REFERENCES:
patent: 3617633 (1971-11-01), Barr
patent: 4370038 (1983-01-01), Kimura
patent: 4484806 (1984-11-01), Onishi et al.
patent: 4611244 (1986-09-01), Hanma et al.
patent: 4706124 (1987-11-01), Baba et al.
patent: 4745484 (1988-05-01), Drexler et al.
National Technical Report, vol. 31, No. 6, (pp. 821-823).

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