Automatic camera focusing means

• US 4,103,309 A
• Filed: 05/11/1976
• Issued: 07/25/1978
• Est. Priority Date: 05/11/1976
• Status: Expired due to Term

• Current Assignee: Massa Products Corporation
• Original Assignee: Donald P. Massa, Fred M. Dellorfano Jr
• Inventors: Massa, Frank
• Primary Examiner(s): Hayes, Monroe H.
• Application Number:
  US05/685,429
• Time in Patent Office: 805 Days
• Field of Search: 354/25, 352/141
• US Class Current: 352/140
• CPC Class Codes: G02B 7/40 using time delay of the reflected waves, e.g. of ultrasonic waves

Abstract

A movie camera is provided with an automatic focusing adjustment mechanism which is responsive to a control signal which is generated by an ultrasonic range finder attached to the camera. The camera is automatically kept in focus as the distance of the subject from the camera is varied.

Claims

1. In combination in a photographic camera, a lens characterized in that its field of view is defined by the angle θ

₁, a directional electroacoustic transducer characterized in that its main beam angle is defined by the angle θ

₂, means for attaching said transducer to said camera with the axis of maximum sensitivity of said transducer mounted parallel to the axis of said lens, said transducer further characterized in that its beam angle θ

₂ is not greater than θ

₁, a first electrical circuit means for operating said electroacoustic transducer as an echo-ranging system and generating a first reference electrical signal which varies as a function of the distance between the transducer and the subject toward which the lens is facing, a second electrical circuit means for generating a second reference electrical signal which varies as a function of the focus setting position of the lens, automatic focus-adjusting means including an electrically-operated drive system adapted for adjusting the position of said lens, control signal means for operating said automatic focus-adjusting means, means for continually comparing said first and said second reference signals, said signal comparison means characterized in that said control signal is generated whenever said first and said second reference signals are not equal, said electrically-operated drive system characterized in that it is responsive to said control signal, whereby said electrically-operated drive system is activated to adjust the position of said lens until said first and second reference signals are equal, whereby said lens is automatically kept in focus on the subject toward which the lens is facing, and further characterized in that the beam angle of said electroacoustic transducer lies within the approximate range 10°

to 30°

.

2. In combination in a photographic camera, a lens characterized in that its field of view is defined by the angle θ

₁, a directional electroacoustic transducer characterized in that its main beam angle is defined by the angle θ

₂, means for attaching said transducer to said camera with the axis of maximum sensitivity of said transducer mounted parallel to the axis of said lens, said transducer further characterized in that its beam angle θ

₂ is not greater than θ

₁, a first electrical circuit means for operating said electroacoustic transducer as an echo-ranging system and generating a first reference electrical signal which varies as a function of the distance between the transducer and the subject toward which the lens is facing, a second electrical circuit means for generating a second reference electrical signal which varies as a function of the focus setting position of the lens, automatic focus-adjusting means including an electrically-operated drive system adapted for adjusting the position of said lens, control signal means for operating said automatic focus-adjusting means, means for continually comparing said first and said second reference signals, said signal comparison means characterized in that said control signal is generated whenever said first and said second reference signals are not equal, said electrically-operated drive system characterized in that it is responsive to said control signal, whereby said electrically-operated drive system is activated to adjust the position of said lens until said first and second reference signals are equal, whereby said lens is automatically kept in focus on the subject toward which the lens is facing, and further characterized in that the magnitude of the secondary lobes in the directional pattern of said electroacoustic transducer are reduced in sensitivity in comparison with the sensitivity along the main axis of the transducer by a ratio at least as great as 10 to 1.