05773810 is referenced by 304 patents and cites 7 patents.

A method for generating, substantially in real time, a user perceptible indication of the degree to which the distance between a handheld imaging device and a target object approximates the in-focus distance therebetween. A stored image of the target object is sampled, in accordance with a pattern of sampling addresses, to determine the magnitude of the slopes of the transitions of the stored image. The stored image is also sampled to determine the contrast value of the stored image. The highest magnitude slope values and the image contrast value are combined to produce a focus metric signal that is indicative of the degree to which the imaging device approximates an in-focus condition. The focus metric signal is then used to generate a user perceptible signal that can be utilized by an operator to move the imaging device toward its in-focus distance.

Title
Method for generating real time degree of focus signal for handheld imaging device
Application Number
8/625111
Publication Number
5773810
Application Date
March 29, 1996
Publication Date
June 30, 1998
Inventor
Andrew Longacre Jr
Skaneateles
NY, US
Robert M Hussey
Liverpool
NY, US
Agent
Wall Marjama & Bilinski
Assignee
Welch Allyn
NY, US
IPC
G06K 7/10
View Original Source