US 4,920,419 A · Zoom lens focus control device for film video player

Abstract

A device (10) controls the focus in a film video player (11) for projection of at least a portion of a film image (F) onto a sensor (16) that generates a corresponding video signal from the sensor image. The film video player (11) has a fixed focal length lens (15) and includes a zoom motor (25) and related elements for changing the magnification of the sensor image with respect to the film image, sensor motor (34) and related elements for adjusting the focus of the sensor image, and a microprocessor (40) and related elements for determining the necessary adjustment to and for controlling the sensor motor to maintain the focus of the sensor image at any selected magnification without cam surfaces. Device (10) determines actual lens focal length upon power-up, eliminating focus variances due to manufacturing and installation, and maintains apparent zoom rate constant throughout the selected range of magnifications.

Claims13

Dependent claims

A device to control the focus in a film video player for projection of at least a portion of a film image carried by a film image mount onto a sensor which generates a corresponding video signal from a sensor image, the film video player having a fixed focal length lens located on an optical axis between said film image mount and said sensor to project said portion onto said sensor, said device comprising:

means for moving said lens axially of said film image mount for selectively changing the magnification of the sensor image with respect to the film image;
means for moving said sensor axially of said film image mount mechanically independently of movement of said lens by said lens moving means for adjusting the focus of the sensor image;
and, means for determining the necessary adjustment and for controlling said means for adjusting to maintain the focus of the sensor image for changes in the selected magnification.

A device to control the focus in a film video player for projection of at least a portion of a film image onto a sensor which generates a corresponding video signal from a sensor image, the film video player having a fixed focal length lens, comprising:

means for selectively changing the magnification of the sensor image with respect to the film image;
means for adjusting the focus of the sensor image without cam surfaces;
and, means for determining the necessary adjustment and for controlling said means for adjusting to maintain the focus of the sensor image for changes in the selected magnification;
wherein said means for changing the magnification includes means for selectively varying the distance between the lens and film image, said means for adjusting the focus of the sensor image includes means for selectively varying the distance between the sensor and the lens, and said means for determining the necessary adjustment to and controlling said means for adjusting includes electronic circuit means for determining the conjugate distances between the lens and film image and between the sensor and the lens to maintain the focus of the sensor image at any selected magnification.

1 more element

Dependencies are inferred from the claim text.

Zoom lens focus control device for film video player

Life of this patent

Zoom lens focus control device for film video player

Life of this patent

Abstract

Claims13