Electro-optical imaging system and lens therefor

• US 4,720,637 A
• Filed: 06/19/1986
• Issued: 01/19/1988
• Est. Priority Date: 06/19/1986
• Status: Expired due to Term

• Current Assignee: Senshin Capital LLC (Intellectual Ventures LLC)
• Original Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Inventors: Clark, Peter P.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Allen, Stephone B.
• Application Number:
  US06/876,004
• Time in Patent Office: 579 Days
• Field of Search: 250/578, 250/216, 358/43, 358/44, 358/55
• US Class Current: 348/340
• CPC Class Codes: G02B 27/46 Systems using spatial filters

Abstract

An electronic imaging system includes an optical system for imaging radiation from a scene onto the image sensing surface of an imaging device for a selected sample period. The imaging device may take the form of a two dimensional array of photoresponsive areas having a device specific upper spatial frequency limit. In order to eliminate alias signal components in the output video signal caused by spatial frequency components in the scene radiation greater than the Nyquist spatial frequency of the device, the optical system is designed to have a spatial frequency limit no higher than the Nyquist frequency of the imaging device and thus functions as a low pass optical filter. The spatial frequency response of the optical components can be controlled by controlling the rotationally symmetric aberrations, and in the preferred form, higher order terms, third and above, which contribute to the spherical aberration of a lens system are designed to have balancing non-zero values to provide the necessary characteristics of the modulation transfer function of the optical system.

Claims

1. An electro-optical imaging system comprising:

an electronic image sensor responsive to radiation from a scene for producing an electrical output signal corresponding to scene radiation imaged thereon, said electronic image sensor having a Nyquist spatial frequency limit; and

a lens for imaging scene radiation onto said electronic image sensor, said lens having rotationally symmetric aberrations over a range of apertures thereof for limiting its spatial frequency response over said range of apertures to a spatial frequency limit substantially equal to said Nyquist limit of said electronic image sensor to substantially eliminate undesirable image patterns due to aliasing.

2. The electro-optical imaging system of claim 1 wherein said lens has spherical aberrations controlled by third, fifth and higher order terms, said third, fifth and higher order terms controlled to balance one another for said range of apertures.

3. A lens for imaging radiation from a scene onto an image sensor having a given Nyquist spatial frequency response limit, said lens comprising:

at least first and second refracting surfaces aligned along an optical axis for imaging radiation from a scene onto the image sensor, said first and second refracting surfaces having rotationally symmetric aberrations controlled to limit said lens'"'"' spatial frequency response to that of the image sensor over a range of apertures to substantially eliminate undesirable image patterns due to aliasing.

4. The optical imaging apparatus of claim 3 wherein said first and second refracting surfaces have spherical aberrations controlled by third, fifth and higher order aberration terms, the third and fifth order terms controlled to balance one another for said range of apertures.