EP0035236A1
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EP
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Tracking servo control device
Assignee: Toshiba Corp
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Filing: 1981-02-25
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Granted: —
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Expires: 2001-02-25
Abstract
Abstract A single laser beam emitted from a laser generator (12) driven by a laser driver (14) in a record mode is alternately switched between a recording beam with large power and a tracking beam with small power. The beam switched is focused onto an optical disc (42) through a laser beam transmitting section (30) and then is reflected from the optical disc (42). The reflected laser beam from the optical disc is received by a pair of photo detecting elements (72, 74) in a two-divided way. Pulsate signal components with peaks corresponding to the recording beam contained in the output signals produced from the photo detecting elements (72, 74) are removed by sample-hold circuits (88, 90) in a wave-shaping section (80). A level difference between the output signals from the wave-shaping section (80) is detected by a differential amplifier (130). The output signal (TC) from the differential amplifier (130), that is, a tracking control signal, drives a drive section (132) to move an optical head (82).
Inventors
- 👤 Tsuneshi Yokota
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 17:06
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/0901; G11B7/12
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
215 words
A tracking servo control device for a disc (42, 200) for optically recording desired information signal comprising light source means (10) for radiating a coherent light beam with a single wavelength, light beam transmitting means (30) for focusing the light beam at a desired location on the disc (42, 200) and for picking up a light beam reflected from the disc (42, 200), photoelectric transducing means (70) optically coupled with said light beam transmitting means (30) for receiving the reflected light beam in a two-divided way and for producing first and second signals corresponding to the amounts of the two-divided reflected light beams, and drive means (132) for mechanically driving at least said light beam transmitting means, characterized by further comprising wave-shaping means (80, 216) connected to said photoelectric transducing means (70) for removing undesired signal components contained in the first and second signals derived from said photoelectric transducing means (70) and for producing third and fourth signals corresponding to the first and second signals, and signal generating means (130) connected between said wave-shaping means (80, 216) and said drive means (132) for detecting a level difference between the third and fourth signals and for producing a fifth signal (TC) corresponding to the level difference detected to control the operation of said drive means (132).
Claim 2
Dependent Claim
215 words
A tracking servo control device for a disc (42, 200) for optically recording desired information signal comprising light source means (10) for radiating a coherent light beam with a single wavelength, light beam transmitting means (30) for focusing the light beam at a desired location on the disc (42, 200) and for picking up a light beam reflected from the disc (42, 200), photoelectric transducing means (70) optically coupled with said light beam transmitting means (30) for receiving the reflected light beam in a two-divided way and for producing first and second signals corresponding to the amounts of the two-divided reflected light beams, and drive means (132) for mechanically driving at least said light beam transmitting means, characterized by further comprising wave-shaping means (80, 216) connected to said photoelectric transducing means (70) for removing undesired signal components contained in the first and second signals derived from said photoelectric transducing means (70) and for producing third and fourth signals corresponding to the first and second signals, and signal generating means (130) connected between said wave-shaping means (80, 216) and said drive means (132) for detecting a level difference between the third and fourth signals and for producing a fifth signal (TC) corresponding to the level difference detected to control the operation of said drive means (132).
Claim 3
Dependent Claim
47 words
A tracking servo control device according to claim 1, characterized in that the disc (42, 200) includes a guide path (46, 204) extending with a desired configuration and a metal film (48) which deforms when exposed to a light beam having a higher intensity than predetermined intensity.
Claim 4
Dependent Claim
51 words
A tracking servo control device according to claim 1, characterized in that said light source means (10) includes a laser generator (12) for generating a laser beam with a desired intensity, and a laser driver (14) for selectively changing an intensity of the laser beam radiated from said laser generator (12).
Claim 5
Dependent Claim
53 words
A tracking servo control device according to claim 3, characterized in that said laser driver (14) switches the laser beam from said laser generator (12) between a first laser beam with a first intensity as a reproducing laser beam and a second laser beam with a second intensity as a recording laser beam.
Claim 6
Dependent Claim
69 words
A tracking servo control device according to claim 1, characterized in that said photoelectric transducing means (70 ' ) includes first and second photo detecting elements (72, 74) arrayed in the radius direction of the disc (24, 200) to produce the first and second signals corresponding to the amounts of the light beams reflected from the disc (24, 200), from said first and second photo detecting elements (72, 74).
Claim 7
Dependent Claim
193 words
A tracking servo control device according to claims 1 and 5, characterized in that said wave-shaping means (80) is comprised of first and second preamplifier means (84, 86) respectively connected to said first and second photo detecting elements (72, 74) for amplifying the first and second output signals, first and second sample-hold circuit means (88, 90) respectively connected to said first and second preamplifier means (84, 86) for sampling and holding signal levels before a desired period during the desired period, first and second bandpass amplifier means (110, 112). for respectively amplifying only desired frequency components contained in the signals produced from said first and second sample-hold circuit means (88, 90), analog.switch means (92) connected to said first and second sample-hold circuit means (88, 90) for selectively transferring the output signals from said first and second sample-hold circuit means (88, 90) to said first and second bandpass amplifier means (110, 112), and first and second envelope detecting means (114, 116) respectively connected to said first and second bandpass amplifier means (110, 112) for detecting envelope waves of signal components contained in the output signals from said first and second bandpass amplifiers (110, 112).
Claim 8
Dependent Claim
164 words
A tracking servo control device according to claims 1 and 5, characterized in that said wave-shaping means (216) is comprised of first and second preamplifier means (84, 86) respectively connected to said first and second photo detecting elements (72, 74), first and second envelope detecting means (22-4, 226) respectively connected to said first and second preamplifier means (84, 86) for detecting envelope wave signals with high potential contained in the output signals generated from said first and second preamplifier means (84, 86), third and fourth envelope detecting means (220, 222) respectively connected to said first and second preamplifier means (84, 86) for detecting envelope wave signals with low potential contained in the output signals generated from said first and second amplifier means (84, 86), and analog switch means (92) for selecting either of the high potential envelope signal from said first and second envelope detecting means (224, 226) and the low potential envelope signal from said third or fourth envelope detecting means (220, 222).
Claim 9
Dependent Claim
39 words
A tracking servo control device according to claim 1, characterized in that said signal generating means (1-30) comprises a differential amplifier for detecting a level difference between the third and fourth signals produced from said wave-shaping means (80, 216).
Claim 10
Dependent Claim
71 words
A tracking servo control device according to claim 1, characterized in that said drive means (132) comprises a linear motor mechanism (136) for mechanically moving at least said light beam transmitting means (30), and a driver (134) for controlling a direction and an amount of the operation of said linear motor mechanism (136) in response to a sign and an amplitude of said fifth signal from said signal generating means (130).
Claim 11
Dependent Claim
32 words
A tracking servo control device according to claim 1, characterized in that said light beam transmitting means (30) and said photoelectric transducing means (70) are together packed in an optical head (82).
References Cited (Backward Citations)
US4198657A
Cited
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