Method of positioning mask using variable mask mechanism and var

Details Method of positioning mask using variable mask mechanism and var Method of positioning mask using variable mask mechanism and var

1995-05-23

1996-05-07

Grimley, A. T.

Photocopying

Projection printing and copying cameras

Illumination systems or details

355 53, 355 77, 355 68, 355 46, G03B 2742, G03B 2752, G03B 2774

Patent

active

055151388

ABSTRACT:
A method of positioning a mask using a variable mask mechanism capable of displacing the mask for partially blocking a light beam for exposing a photosensitive material and of changing the amount of opening of an aperture through which the light beam passes, is provided which comprises the steps of measuring the density of each of images on a negative film in a state in which the mask is in alignment with a range in which the density of each image can be measured and thereafter shifting the mask to a range in which the images on the negative film can be exposed, thereby exposing the photosensitive material. Therefore, a position permissible range of the mask at the time of photometry and exposure is expanded. It is thus unnecessary to position the mask with accuracy higher than required. Further, the manufacturing cost of the variable mask mechanism can be reduced.

REFERENCES:
patent: 4093378 (1978-06-01), Horr et al.
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patent: 4668082 (1987-05-01), Terashita et al.
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patent: 4816874 (1989-03-01), Terashita et al.
patent: 4821073 (1989-04-01), Backus et al.
patent: 4937618 (1990-06-01), Ayata et al.
patent: 5006886 (1991-04-01), Susuki
patent: 5359389 (1994-10-01), Isohata

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