Fully automatic focusing projector

Claim 2

In a projector having a housing, an illuminated optical axis, means on the housing for supporting a film transparency in a predetermined reference plane along the optical axis for projecting an image of a supported film transparency onto a viewing surface in a plane spaced from the objective lens, and drive means for moving the objective lens along the optical axis; the improvement comprising: means for sensing the distance between the objective lens and the viewing surface and for generating a signal indicative of such distance; and control means responsive to said signal for actuating the drive means to move the objective lens to a position along the optical axis to maintain the distance between the reference plane and the objective lens a predetermined function of the distance between the viewing surface and the objective lens, whereby the projected image is in focus at the viewing surface.

Claim 3

The improvement as defined in claim 1 wherein said sensing and signal generating means comprises: a radiation source; first optical means forming an image of said radiation source at the plane of the viewing surface, from which the image is reflected; differential radiation-sensitive means for generating a signal indicative of the position of radiation impinging thereon; and second optical means for reimaging the reflected image upon said radiation-sensitive means at a position which is a function of the position of the objective lens along the optical axis and the distance between the viewing surface and the objective lens.

Claim 4

The improvement as defined in claim 2 wherein said first optical means includes filter means between said radiation source and said planar surface for removing the visible portion of the radiation.

Claim 5

In a projector having a housing, an illuminated optical axis, means on the housing for supporting a film transparency in a predetermined film plane along the optical axis, an objective lens having a focal length f Mounted on the housing a distance d'' from the film plane for movement along the optical axis for projecting an image of a supported film transparency onto a planar surface spaced a distance d from the objective lens, and drive means for moving the objective lens along the optical axis; the improvement comprising: means for sensing the distance d and for generating a signal indicative of such distance; and control means responsive to said generated signal for activating the drive means to move the objective lens to a position wherein d'' equals f+ f2/(d-f)

Claim 6

In a projector having a housing, an illuminated optical axis, means on the housing for supporting a film transparency in a predetermined film plane along the optical axis, an objective lens having a focal length f Mounted on the housing a distance d'' from the film plane for movement along the optical axis for projecting an image of a supported film transparency onto a planar surface spaced a distance d from the objective lens, and drive means for moving the objective lens along the optical axis; the improvement comprising: means for sensing the distance d and for generating a signal indicative of such distance; and control means responsive to said generated signal for activating the drive means to move the objective lens to a position wherein d'' equals f+ f2/(d-f)

Claim 7

In a projector having a housing, an illuminated optical axis, means on the housing for supporting a film transparency for movement along the optical axis relative to a reference plane, an objective lens mounted on the housing for movement along the optical axis for projecting an image of a supported film transparency onto a viewing surface in a plane spaced from the objective lens, first drive means for moving a supported transparency relative to the reference plane, and second drive means for moving the objective lens along the optical axis; the improvement comprising: means for sensing the distance between the objective lens and the viewing surface and for generating a signal indicative of such distance; control means responsive to said signal for activating the second drive means to move the objective lens to a position along the optical axis to maintain the distance between the reference plane and the objective lens a predetermined function of the distance between the viewing surface and the objective lens; means for detecting the position of a supported film transparency relative to the reference plane and for generating an error signal indicative of any difference between the position of the transparency and the reference plane; and means responsive to said error signal for activating the first drive means to move the transparency toward the reference plane.

Claim 8

In a projector having a housing, an illuminated optical axis, means on the housing for supporting a film transparency for movement along the optical axis relative to a reference plane, an objective lens mounted on the housing for movement along the optical axis for projecting an image of a supported film transparency onto a viewing surface in a plane spaced from the objective lens, first drive means for moving a supported transparency relative to the reference plane, and second drive means for moving the objective lens along the optical axis; the improvement comprising: means for sensing the distance between the objective lens and the viewing surface and for generating a signal indicative of such distance; control means responsive to said signal for activating the second drive means to move the objective lens to a position along the optical axis to maintain the distance between the reference plane and the objective lens a predetermined function of the distance between the viewing surface and the objective lens; means for detecting the position of a supported film transparency relative to the reference plane and for generating an error signal indicative of any difference between the position of the transparency and the reference plane; and means responsive to said error signal for activating the first drive means to move the transparency toward the reference plane.

Claim 9

The improvement as defined in claim 5 further comprising: means for disabling said distance sensing and signal generating means when a film transparency is supported in the housing; and means for disabling said first drive means when a film transparency is not supported in the housing.

Claim 10

The improvement as defined in claim 5 wherein said sensing and signal generating means comprises: a radiation source; a first optical means for forming an image of said radiation source at the plane of the viewing surface, from which it is reflected by the viewing surface; differential radiation-sensitive means for generating a signal indicative of the position of radiation impinging thereon; and second optical means for reimaging the reflected image upon said radiation-sensitive means at a position which is a function of the position of the objective lens along the optical axis and the distance between the viewing surface and the objective lens.

Claim 11

The improvement as defined in claim 7 wherein said position detecting and error signal generating means comprises: third optical means for forming an image of said radiation source on a supported film transparency, from which the image is reflected; and fourth optical means for reimaging the image reflected from the transparency upon said radiation-sensitive means at a position which is a function of the supported film transparency relative to the reference plane.

Claim 12

In a projector having a housing, an illuminated optical axis, means on the housing for supporting a film transparency for movement along the optical axis relative to a reference plane, and an objective lens mounted on the housing for movement along the optical axis for projecting an image of a supported film transparency onto a viewing surface in a plane spaced from the objective lens, the improvement comprising: a drive motor; a transmission shiftable between a first condition interconnecting said driVe motor and said objective lens and a second condition interconnecting said drive motor and said transparency supporting means; means for selectively shifting said transmission between its first and second conditions; means for sensing the distance between the objective lens and the viewing surface and for generating a signal indicative of such distance when said transmission is in its first condition for energizing said drive motor to move the objective lens to a position along the optical axis to maintain the distance between the objective lens and the reference plane a predetermined function of the distance between the objective lens and the viewing surface; and means for detecting the position of a supported film transparency relative to the reference plane and for generating an error signal indicative of any difference between the position of the transparency and the reference plane when said transmission is in its second position for energizing said drive motor to move the transparency toward the reference plane.

Claim 13

In a projector having a housing, an illuminated optical axis, means on the housing for supporting a film transparency for movement along the optical axis relative to a reference plane, and an objective lens mounted on the housing for movement along the optical axis for projecting an image of a supported film transparency onto a viewing surface in a plane spaced from the objective lens, the improvement comprising: a drive motor; a transmission shiftable between a first condition interconnecting said driVe motor and said objective lens and a second condition interconnecting said drive motor and said transparency supporting means; means for selectively shifting said transmission between its first and second conditions; means for sensing the distance between the objective lens and the viewing surface and for generating a signal indicative of such distance when said transmission is in its first condition for energizing said drive motor to move the objective lens to a position along the optical axis to maintain the distance between the objective lens and the reference plane a predetermined function of the distance between the objective lens and the viewing surface; and means for detecting the position of a supported film transparency relative to the reference plane and for generating an error signal indicative of any difference between the position of the transparency and the reference plane when said transmission is in its second position for energizing said drive motor to move the transparency toward the reference plane.

Claim 14

The improvement as defined in claim 9 wherein said transmission shifting means comprises: means for shifting said transmission to its first condition when a film transparency is supported in said housing; and means for shifting said transmission to its first condition when a film transparency is not supported in said housing.