Infrared wink ranging system

• US 4,785,322 A
• Filed: 12/10/1987
• Issued: 11/15/1988
• Est. Priority Date: 12/10/1987
• Status: Expired due to Term

• Current Assignee: Senshin Capital LLC (Intellectual Ventures LLC)
• Original Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Inventors: Whiteside, George D., Harrison, George C.
• Primary Examiner(s): ADAMS JR, RUSSELL E
• Application Number:
  US07/131,095
• Time in Patent Office: 341 Days
• Field of Search: 354/403, 354/415, 354/482
• US Class Current: 396/106
• CPC Class Codes: G02B 7/32 using active means, e.g. light emitter including both an active and a passive focus detecting device G02B7/285; using ultrasound G02B7/40
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: G03B 2215/0507 Pop-up mechanisms
• CPC Class Codes: G03B 7/17 Selection of modes in flash units by exposure control arrangements

Abstract

A black, infrared pass filter is disposed in front of the strobe element of an automatic rangefinding camera to provide an infrared ranging wink for ranging during the pre-exposure steps of a camera cycle. As the cycle continues, the filter is temporarily displaced from in front of the strobe element to allow a visible light, flash firing for scene illumination. Once the exposure firing is complete, the filter resumes its original position in front of the strobe element such that the filter allows only infrared light to be transmitted from the strobe element except during exposure strobe firing.

Claims

1. In a photographic camera having a strobe unit for emtting a flash containing both visible and infrared light, and means for initiating an exposure cycle including activation of the strobe unit to provide a pre-exposure flash for determining subject distance and an exposure flash for illuminating the photographic scene during film exposure, the improvement comprising:

a filter for blocking visible illumination and passing infrared radiation;

means for mounting said filter on the camera for movement between a first position in which it is in blocking relation to emissions from said strobe unit directed toward the scene and a second position in which it is displaced from said strobe unit to allow unobstructed passage or light emitted by said unit toward the scene; and

means for automatically displacing said filter during a single exposure cycle from its said first to its said second position after activation of said strobe unit to provide the pre-exposure flash, thereby automatically providing illumination of the scene with infrared illumination for distance determination and visible light from said strobe unit for film exposure.

2. A photographic camera comprising:

a camera actuator;

an electronic flash unit operable to direct illumination along a given path to the scene to be photographed, said flash unit providing both visible and infrared illumination;

an infrared pass filter mounted for movement between a first position in blocking relation to said given path and a second position in unblocking relation to said given path;

drive means operable for displacing said filter between its first and second position; and

means responsive to operation of said actuator for firing said flash unit prior to film exposure to produce a pre-exposure flash for determining subject distance, for actuating said camera to provide a film exposure, and for firing said flash unit during said film exposure to produce an exposure flash for providing at least supplemental scene illumination for film exposure, said actuator responsive means including means for operating said drive means to displace said filter from its first to its said second position following said pre-exposure flash and prior to said exposure flash such that visible illumination emitted by said flash unit is blocked from said scene during said pre-exposure flash and transmitted to said scene during said exposure flash.

3. The camera of claim 2 wherein said actuator responsive means additionally operates said drive means to return said filter to its said first position following said exposure flash.

4. The camera of claim 2 wherein said filter is mounted for pivotal movement around an axis generally normal to the plane of said filter.

5. A method of operating an automatic rangefinding camera having a strobe unit, said method comprising the steps of:

placing a visible light blocking, infrared pass filter in a blocking position in front of said strobe element;

producing an infrared wink by firing said strobe element with said filter in its said blocking position;

determining subject distance in accordance with the reflection of said wink from the scene to be photographed;

then displacing said blocking filter from its said blocking position in front of said strobe element; and

exposing a frame of film retained in said camera and producing a visible light exposure flash during said exposure by firing said strobe element.

6. The method of claim 5 further comprising the step of replacing said blocking filter in said position in front of said strobe element following said producing of an exposure flash in preparation for the next ranging wink.