United States Patent im
Snopko
[in 3,932,700 [45] Jan. 13, 1976
[54] FOCUS TRACKING REGISTRATION FOR
OPTICAL REPRODUCING SYSTEMS [75] Inventor: Paul A. Snopko, Chicago, 111.
[73] Assignee: Zenith Radio Corporation, Chicago, III.
[22] Filed: Feb. 4, 1974 [21] Appl. No.: 439,657
[52] U.S. CI 178/6.6 R; 179/100.3 V;
179/100.4 R; 250/201; 250/578
[51] Int. CI.2 H04N 5/76; Gl IB 11/18
[58] Field of Search 179/100.3 V, 100.3 B,
100.4 R, 179/100.4 A; 250/201, 208, 211 R, 578; 178/6.7 A, 6.7 R, 6.6 A, 6.6 R
[56 J References Cited
UNITED STATES PATENTS
3,198,880 8/1965 Toulon 179/100.3 V
3,553,455 1/1971 Sato et al 250/208
3,610,934 10/1971 Turner 250/201
3,673,412 6/1972 Olson 179/100.3 B
3,848,095 11/1974 Wohlmut 179/100.3 V
Primary Examiner—Bernard Konick
Assistant Examiner—Jay P. Lucas
Attorney, Agent, or Firm—Cornelius J. O'Connor
[57] ABSTRACT
A video disc reproducing system wobbles the reading beam across the storage track of the disc and the outputs of two photocells are added to develop both the information signal and a radial beam tracking signal employed to maintain tracking registration of the beam and the storage track. The outputs of these cells are also combined differentially to develop a focus tracking signal used to adjust the focal plane of the reading beam to maintain focus registration.
A search feature adjusts the focus conditions over a range but is disabled and is superseded by the focus tracking control arrangement once focus conditions are brought within the operating range of the focus tracking arrangement.
8 Claims, 7 Drawing Figures
