Method and apparatus for calibrating iris of photographic printer
First Claim
1. A method of calibrating an adjustable iris in a photographic printer including a light source, a sensor intended to produce a variable output in response to changes in an aperture of the iris, a lens system for projecting an image from a photographic negative illuminated by the light source, and an image plane where the projected image is received by a photographic paper, the iris being located in a light path from the light source so as to control an amount of light passing from the negative through the lens system to the paper, said method comprising steps of:
- a) setting the iris at a reference aperture for a reference magnification of the lens system;
b) near the image plane, measuring a reference intensity of light transmitted from the light source through the iris, in an absence of a photographic negative;
c) calculating a modified intensity of light to be measured near the image plane after a predetermined change in stop number of the iris;
d) changing the aperture of the iris in a direction to cause the intensity of light near the image plane to change from the reference intensity to the calculated modified intensity;
e) during the changing, measuring the intensity of light near the image plane;
f) stopping the changing of the aperture when the intensity measured near the image plane equals the calculated modified intensity;
g) measuring an output Sv of the sensor when the intensity of light near the image plane equals the calculated modified intensity;
h) repeating steps c) to g) for successive predetermined changes in stop number of the iris; and
i) storing for use during operation of the photographic printer a correlation for each changed stop number among magnification settings of the lens system, the changed stop number and the output of the sensor at the changed stop number.
1 Assignment
0 Petitions
Accused Products
Abstract
An adjustable iris diaphragm assembly (26) in a zoom lens system (16) of a photographic printer (10) is calibrated for each magnification setting by progressively adjusting the aperture opening until a predetermined light intensity is detected by a sensor (36) near a paper plane of the printer and then determining an output voltage of a feedback sensor (88) of the iris diaphragm assembly. A correlation is established among magnification settings of the printer, iris stop settings, and sensor output voltages to enable the printer to accurately set the iris for a desired exposure.
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Citations
14 Claims
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1. A method of calibrating an adjustable iris in a photographic printer including a light source, a sensor intended to produce a variable output in response to changes in an aperture of the iris, a lens system for projecting an image from a photographic negative illuminated by the light source, and an image plane where the projected image is received by a photographic paper, the iris being located in a light path from the light source so as to control an amount of light passing from the negative through the lens system to the paper, said method comprising steps of:
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a) setting the iris at a reference aperture for a reference magnification of the lens system; b) near the image plane, measuring a reference intensity of light transmitted from the light source through the iris, in an absence of a photographic negative; c) calculating a modified intensity of light to be measured near the image plane after a predetermined change in stop number of the iris; d) changing the aperture of the iris in a direction to cause the intensity of light near the image plane to change from the reference intensity to the calculated modified intensity; e) during the changing, measuring the intensity of light near the image plane; f) stopping the changing of the aperture when the intensity measured near the image plane equals the calculated modified intensity; g) measuring an output Sv of the sensor when the intensity of light near the image plane equals the calculated modified intensity; h) repeating steps c) to g) for successive predetermined changes in stop number of the iris; and i) storing for use during operation of the photographic printer a correlation for each changed stop number among magnification settings of the lens system, the changed stop number and the output of the sensor at the changed stop number. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for calibrating an adjustable iris in a photographic printer including a light source, a sensor intended to produce a variable output in response to changes in an aperture of the iris, a lens system for projecting an image from a photographic negative illuminated by the light source, and an image plane where the projected image is received by a photographic paper, the iris being located in a light path from the light source so as to control an amount of light passing from the negative through the lens system to the paper, said apparatus comprising:
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a) means for setting the iris at a reference aperture for a reference magnification to of the lens system; b) means, near the image plane, for measuring a reference intensity of light transmitted from the light source through the iris, in an absence of a photographic negative; c) programmed computer means for calculating a modified intensity of light to be measured near the image plane after a predetermined change in stop number of the iris; d) means for changing the aperture of the iris in a direction to cause the intensity of light near the image plane to change from the reference intensity to the calculated modified intensity; e) means for stopping the changing of the aperture when the intensity measured near the image plane equals the calculated modified intensity; f) means for measuring an output Sv of the sensor when the intensity of light near the image plane equals the calculated modified intensity; and g) means for storing for use during operation of photographic printer a correlation for each changed stop number among magnification settings of the lens system, the changed stop number and the output of the sensor at the changed stop number. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification