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Double layered optical low pass filter permitting improved image resolution

  • US 4,009,939 A
  • Filed: 06/03/1975
  • Issued: 03/01/1977
  • Est. Priority Date: 06/05/1974
  • Status: Expired due to Term
First Claim
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1. An optical low pass filter for use in a color video system for monitoring an object scene having a color encoding striped filter for spatially modulating at least two selected primary color signals while passing a third luminance signal at a higher spatial frequency comprising:

  • a first phase retarding filter layer; and

    a second phase retarding filter layer, and respective filter layers including a plurality of phase retarding grating stripes, the respective first and second stripes having a nonparallel alignment relative to each other and providing a combined optical transfer function value characteristic of preventing the transmittance of the high spatial frequency signal components of the two selected primary colors while transmitting luminance signals at spatial frequencies above the cut off frequencies of the primary colors, the nonparallel grating stripes preventing spurious primary color signals not representative of the object scene while higher spatial frequency luminance signals are transmitted to provide an improved image resolution.

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