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:
Jun. 07, 1977
Filed:
Oct. 28, 1975
Victor A Misek, Hudson, NH (US);
Sanders Associates, Inc., Nashua, NH (US);
Abstract
Distance measurement is provided by an optical system which includes modulation detection apparatus for determining when the optics are a predetermined distance from an object. This is accomplished by detecting an in-focus condition in terms of the modulation content of a cross-correlated signal. When the device is used as a fuse, a fire control signal is initiated when the ordinance device carrying the fuse is at a predetermined distance from a target. The system includes a stationary cross-correlation grating set at an optimal single spatial frequency based on the resolution and more specifically the modulation transfer function of the optics used. The grating is located at the image plane of an optical imaging system and an optical wedge is mounted for rotation about optical axis of this system so that the image is circularly nutated in the plane of the cross-correlation grating. Light passing through the cross-correlation grating is directed to a detector whose output is then amplified, filtered and rectified to yield a signal proportional to the modulation content of the output signal from the detector, with 100 percent modulation indicating an in-focus condition. This signal is compared, in one embodiment, to the output of a second detector which establishes an adaptive threshold such that when this threshold is exceeded an alarm or fire control signal may be initiated. The threshold level corresponds to a modulation percentage indicative of an acceptable in-focus condition. The cross-correlation grating in a preferred embodiment takes on the form of a multi-apertured disc with the apertures arranged at the apices of a hexagonal pattern.