Multiple frequency ranging apparatus for focus control
US4435055A · kind A · utility
10Cited by
2References
25Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Aug 12, 1981 |
| Grant date | Mar 6, 1984 |
| Priority date | — |
| Expiry date | Aug 12, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S15/36
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A photoplotter includes an autofocus control for maintaining a precise focal distance between a photohead in the plotter and the film surface which is exposed by the head. The autofocus control employs a dual frequency ultrasonic ranging apparatus which permits coarse focus control at one frequency and fine focus control at a second, higher frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.