The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 22, 1981
Filed:
Mar. 04, 1980
Duncan B Campbell, Santa Barbara, CA (US);
Other;
Abstract
A free space communication receiver including a lens and a photodetector spaced along the optical axis of the lens is provided with a drive for changing the distance between the lens and photodetector to thereby shift the focal point of radiation passing through the lens relative to the photodetector. A signal level detector provides an output signal level in response to the signal from the photodetector. A logic control such as a microprocessor is connected between the signal level detector and the drive for the lens. Provided that the output signal level is below a given high threshold signal level, an automatic self-focus operation takes effect, wherein as the drive moves the focal point of the lens closer to the photodetector, the resulting increase in the output signal level maintains the operation of the drive through the logic control or microprocessor until such time as the focal point coincides with the photodetector. Further movement by the drive results in defocusing and a decrease in the signal. This decrease in the signal is detected and automatically reverses the direction of the drive so that an automatic sensing of the peak signal results. This basic automatic self-focus control works in conjunction with attenuation networks to provide a very wide range automatic gain control for the entire system. Moreover, the self-focus feature compensates for changes in the lens focal length as a result of variations in ambient temperature.