Real-time optical filtering method with improved filtered image detection and bandwidth adjustment

• US 4,426,663 A
• Filed: 01/06/1982
• Issued: 01/17/1984
• Est. Priority Date: 01/06/1982
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Ginsburg, Arthur P., Evans, David W.
• Primary Examiner(s): Chin, Tommy P.
• Application Number:
  US06/337,348
• Time in Patent Office: 741 Days
• Field of Search: 358/211, 358/225, 358/226, 358/42, 358/60, 358/61, 358/62, 358/63, 358/231, 358/232, 358/236, 350/103, 350/162 SF, 350/173, 350/174, 350/162.12, 350/162.15, 350/162.19, 356/345, 356/352, 356/354, 353/20
• US Class Current: 348/217.1
• CPC Class Codes: G02B 27/46 Systems using spatial filters

Abstract

In a system for real-time coherent optical filtering of visual imagery which encompasses a laser and a set of lenses for transmitting a visual target image of an input, a Fabry-Perot interferometer for filtering the target image to produce a filtered target image at an output having a predetermined bandwidth of spatial frequency information, the improvements relate to the output being in the form of a low-light level video system capable of detecting the filtered image even when at a low level of luminance, and a laser adjustable in operating power between low and high levels and in operating wavelength within a wide range for adjusting the bandwidths of the interferometer between narrow and broad ranges.

Claims

1. In a method of real-time coherent optical filtering of visual imagery including the steps of transmitting a visual target image of an input, filtering said transmitted target image to produce a filtered target image having a variable bandwidth of spatial frequency information, and projecting said filtered target image, the improvement which comprises the steps of:

(a) receiving said projected filtered target image and detecting said image even when at a low level of luminance; and

(b) coherently illuminating said visual target image of said input prior to said transmitting of the same, and adjusting said bandwidth of said filtering between narrow and broad ranges thereof, so as to vary the bandwidth of said spatial information, by varying the power at which said illuminating is carried out between low and high predetermined levels and by varying the wavelength at which said illuminating is carried out within a predetermined range.

2. The real-time coherent optical filtering method of claim 1, wherein a low-light level video system is used for receiving and detecting said image.

3. The real-time coherent optical filtering method of claim 1, wherein a laser adjustable in operating power between low and high levels and in operating wavelength within a predetermined wider range is used for coherently illuminating said visual target image and adjusting said bandwidth of said filtering.