HK5696A - Apparatus for the reproduction of data - Google Patents
Apparatus for the reproduction of data Download PDFInfo
- Publication number
- HK5696A HK5696A HK5696A HK5696A HK5696A HK 5696 A HK5696 A HK 5696A HK 5696 A HK5696 A HK 5696A HK 5696 A HK5696 A HK 5696A HK 5696 A HK5696 A HK 5696A
- Authority
- HK
- Hong Kong
- Prior art keywords
- output
- input
- focus
- error signal
- digital
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
- H03F1/303—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters using a switching device
- H03F1/304—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters using a switching device and using digital means
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0901—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following only
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/094—Methods and circuits for servo offset compensation
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only
- G11B7/0909—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only by astigmatic methods
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Optical Recording Or Reproduction (AREA)
- Amplifiers (AREA)
- Circuits Of Receivers In General (AREA)
- Indexing, Searching, Synchronizing, And The Amount Of Synchronization Travel Of Record Carriers (AREA)
- Signal Processing For Digital Recording And Reproducing (AREA)
Abstract
Apparatus for the reproduction of data which can be read contactlessly from a recording medium by means of an optical scanning device. Such apparatuses are equipped with a focus control circuit, in order to focus the light beam scanning the data onto the recording medium, and with a track control circuit, in order to be able to guide the light beam on the data tracks. However, the control amplifier (FR) of the focus control circuit is affected by an off-set voltage, which varies with the temperature and ageing of the control amplifier. In order to compensate automatically for the off-set voltage of the control amplifier (FR) of the focus control circuit, an input of the control amplifier (FR) is fed an off-set compensation voltage, which is varied until the high-frequency components of the focus error signal (FE) assume a minimum, since in this case the off-set voltage is optimally compensated. CD players, video-disc players, draw-disc players, magneto-optical equipment. <IMAGE>
Description
The invention relates to a device for reproducing data that is readable from the data traces of a recording medium by means of an optical scanning device, in which at least one beam of light can be focused on the recording medium by means of a focus control circuit and passed on the data traces by means of a track control circuit, in which the light beam is reflected from the recording medium onto a photodetector, by means of which an electric data signal, a focus error signal as the true value for the focus control circuit and a track error signal as the true value for the track control circuit are generated, in which the prohibited off-set voltage of the focus control circuit is compensated, four high-inverse photodetectors of the focus control circuit are also connected, the values of the light are minimized and the photodetector is not inverted, and the photodetector is also inverted, the photodetector is in the second and third positions, the photodetector is in the second position, and the photodetector is in the second position, the photodetector is in the third position, and the photodetector is in the second position.
Such devices, e.g. CD players, magneto-optical players and recorders, recorders and playback devices for draw discs or video recorders, are equipped with an optical scanning device consisting of a laser diode, several lenses, a prism beam splitter and a photodetector.
The light beam emitted by the laser diode is focused on the CD-ROM by means of lenses and reflected from there on a photodetector. From the output signal of the photodetector, the data stored on the CD-ROM and the actual value for the focus and the track circuit are obtained.
The focus control circuit is a coil whose magnetic field moves a lens along the optical axis, and which, by moving the lens, causes the light beam emitted by the laser diode to always be focused on the CD-ROM. The optical scanning device can be moved radially in relation to the CD-ROM by means of the track control circuit, often called radial drive.
In some devices, the radial drive is made up of a so-called coarse and a so-called fine drive. The coarse drive is for example made as a spindle, by means of which the entire optical scanning device from the laser diode, the lens, the prism beam separator and the photodetector can be radially moved. With the fine drive the beam of light can be tilted in a radial direction, for example, by a predefined small angle, so that the light beam can travel a small distance along a radius of the CD-board by this tilting movement alone.
In order to achieve an impeccable reproduction of the data, be it image and sound in a video player or just the sound in a CD player, in addition to a precise focusing of the light beam on the video or CD, a precise guidance along the data tracks of the plate is required.
To avoid interference with the data transmission by the off-set voltage of the control amplifier of the focus control circuit, it is necessary to compensate for the off-set voltage, but by manually adjusting a control circuit-based matching potentiometer, compensation can only be approximated, as changes in the off-set voltage due to temperature fluctuations and aging of the control amplifier are not taken into account.
JP-A-59 8144 has a circuit arrangement for compensating for the offset voltage in a focus control circuit, which includes a modulator that modulates the laser light focused on the recording medium. The modulation fractions in the focus error signal caused by the modulated laser light are detected and reduced to zero by a compensation voltage at the input of the control amplifier.
The invention is therefore intended to design a data reproduction device according to the general concept of claim 1 in such a way that the off-set voltage of the control amplifier in the focus control circuit is automatically compensated during operation without the need to provide an additional modulator to modulate the laser diode.
The invention solves this problem by the combination of features described in claim 1.
Show it
Figure 1 a photodetector of a CD player according to the inventionFigure 2 an embodiment of the invention.
Figures 1 and 2 illustrate the present invention.
The photodetector PD is shown in Figure 1 as the optical scanning device of a CD player, which focuses three laser beams L1, L2 and L3 on the CD plate.
In the photodetector, four square photodiodes A, B, C and D are placed together to form a square, with two other equally square photodiodes E and F facing each other diagonally.
The middle laser beam L1, focused on the four photodiodes A, B, C and D, produces the data signal HF = AS + BS + CS + DS and the focus error signal FE = (AS + CS) - (BS + DS). The two outer beams L2 and L3, of which the front L2 falls on the photodiode E and the rear L3 on the photodiode F, produce the trace error signal TE = ES - FS. AS, BS, CS, DS, ES and FS each denote the photodiode voltages A, B, C, D, E and F. Because the optical abrasive device in the middle beam length of the laser beam L1 provides an astigmatist collinear, the middle laser is more accurate when focusing on the four large ellipticals, while the A1 is more elliptically deflected, creating a photo-imaging image, while the D1 is elliptically deflected, creating an elliptic lens.
Figure 1a shows the case of focusing and precise tracking, which will be discussed later. Because the spot formed by the laser beam L1 on the large square is circular, the focus error signal is FE = (AS + CS) - (BS + DS) = 0.
In Figure 1b, the one case of deflection is shown, that the CD-plate is too far from the lens. The focus error signal FE is negative: FE = (AS + CS) - (BS + DS) < 0. At the negative value of the focus error signal FE, the focus control circuit detects that the distance between the CD-plate and the lens is too large.
The second case of deflection, where the lens is too close to the CD plate, is shown in Figure 1c. The focus error signal FE has a positive value: FE = (AS + CS) - (BS + DS) > 0. At the positive value of the focus error signal FE, the focus control circuit detects that the lens is too close to the CD plate.
The following is an explanation of the operation of the track guide by means of the track control circuit.
In Figures 1a, 1b and 1c, the laser beams L1, L2 and L3 follow the track exactly.
In Figure 1d, the case is shown where the laser beams L1, L2 and L3 are shifted to the right of the track. The track error signal takes a negative value: TE = ES - FS < 0.
In the opposite case, if the laser beams are shifted to the left of the track, the track error signal is positive: TE = ES - FS > 0.
Figure 2 first describes the construction of a first example and then explains its function.
In Figure 2, the interconnected cathodes of the four photodiodes A, B, C and D of the PD photodetector are at a voltage of +UB. The interconnected anodes of the photodiodes A and C are connected via a resistor R1 to the inverting input of a differential amplifier V, whose non-inverting input is connected via a resistor R2 to the also interconnected anodes of the diodes B and D. The output of the differential amplifier V, at which the focus error signal FE is detectable for the switching part of the focus circuit input, is connected to the input of a high-pass HP and its output is connected via a counter R3 to its inverting analogue E. The output of the high-pass E is connected to the output of a variable variable E. The output of a variable E is equivalent to the output value of a variable G. The output of a variable E. The output of a digital controller cannot be equivalent to the output of an MP4 or an MP4 controller.
The high-frequency portions of the focus error signal FE are sifted out by the HP highpass and passed to the input of the rectifier G. The rectifier G forms the peak, mean or effective value of the high-frequency portions of the focus error signal FE. For example, the analog-to-digital converter AD converts the analog peak value to a digital value and feeds it to the input of the control circuit MP. The control circuit MP now changes the digital value at its output A1 as long as the digital set-to-analog converter DA and the resistor R4 as off-set compensation voltage are fed to the non-inverting input of the differential amplifier V, until the digital value is executed at the output of the analog-to-digital signal.
Because the off-set voltage of the control amplifier V of the focus control circuit is constantly compensated for by the invention while the CD player is in operation, aging of the components and temperature changes no longer matter. The off-set compensation voltage is immediately corrected both for slow deviations of the off-set voltage due to aging, so-called drift, and for rapid deviations due to rapid temperature fluctuations.
The invention is not limited to CD players, but can be applied in a beneficial way to draw-disc players, video recorders and magneto-optical devices.
Claims (5)
- Device for the reproduction of data readable by means of an optical scanning device from the data tracks of a record medium, at least one light beam being focusable onto the record medium by means of a focus control loop and guidable on the data tracks by means of a tracking control loop, the light beam being reflected by the record medium onto a photodetector (PD), by means of which an electrical data signal (HF), a focus error signal (FE) as an actual value for the focus control loop and a tracking error signal (TE) as an actual value for the tracking control loop are produced, the high-frequency portions of the focus error signal (FE) being analyzed and minimized to correct the offset voltage of the control amplifier of the focus control loop, the light beam (L1) reading the data being focused onto four photodiodes (A, B, C, D), the cathodes, which are connected to one another, of the four photodiodes (A, B, C, D) being at a voltage (+UB), the anodes, which are connected to one another, of the first and second photodiodes (A, C) being connected to the inverting input of a differential amplifier (V), which supplies the focus error signal at its output and the non-inverting input of which is connected to the anodes, which are likewise connected to one another, of the second and third photodiodes (B, D), characterized in that the output of the differential amplifier (V), at which the focus error signal (FE) is detectable, is connected to the input of a high pass (HP), that the output of the high pass (HP) is connected to the input of a rectifier (G), the output of which is connected to the input of an analog-to-digital converter (AD), that the output of the analog-to-digital converter (AD) is connected to the input (E1) of a control circuit (MP), the output (A1) of which is connected to the input of a digital-to-analog converter (DA), that the output of the digital-to-analog converter (DA) is connected to the non-inverting input of the differential amplifier (V) and that the control unit (MP) changes the digital value at its output (A1) until the digital value at its input (E1) assumes a minimum.
- Device according to claim 1, characterized in that between the anodes, which are connected to one another, of the first and second diodes (A, C) and the inverting input of the differential amplifier (V) is a first resistor (R1), that between the anodes, which are connected to one another, of the third and fourth diodes (B, D) is a second resistor (R2), that the output of the differential amplifier (V) is linked back to its inverting input via a third resistor (R3) and that between the output of the digital-to-analog converter (DA) and the non-inverting input of the amplifier (V) is a fourth resistor (R4).
- Device according to claim 1 or 2, characterized in that the rectifier (G) acts as a peak detector.
- Device according to claim 1 or 2, characterized in that the rectifier (G) acts as a mean value former.
- Device according to claim 1 or 2, characterized in that the rectifier (G) acts as an r.m.s. value former.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19873732997 DE3732997A1 (en) | 1987-09-30 | 1987-09-30 | DEVICE FOR PLAYING BACK DATA |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| HK5696A true HK5696A (en) | 1996-01-19 |
Family
ID=6337266
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| HK5696A HK5696A (en) | 1987-09-30 | 1996-01-11 | Apparatus for the reproduction of data |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0309719B1 (en) |
| JP (1) | JP2956770B2 (en) |
| KR (1) | KR960016359B1 (en) |
| AT (1) | ATE78624T1 (en) |
| DE (2) | DE3732997A1 (en) |
| DK (1) | DK548288A (en) |
| ES (1) | ES2034068T3 (en) |
| GR (1) | GR3005801T3 (en) |
| HK (1) | HK5696A (en) |
| HU (1) | HUT63010A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03115918U (en) * | 1990-02-28 | 1991-12-02 | ||
| DE4102857A1 (en) * | 1991-01-31 | 1992-08-06 | Thomson Brandt Gmbh | Beam focussing control method for CD player - varying offset compensation voltage fed to focussing control circuit until bit error rate of scanned data signal reaches minimum |
| DE102006020830B4 (en) * | 2006-05-04 | 2014-02-13 | Siemens Aktiengesellschaft | Controller for a high-frequency amplifier |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS598144A (en) * | 1982-07-05 | 1984-01-17 | Trio Kenwood Corp | Optical information reader |
| JPS61177646A (en) * | 1985-02-04 | 1986-08-09 | インタ−ナショナル ビジネス マシ−ンズ コ−ポレ−ション | Optical disc |
| CA1261467A (en) * | 1985-11-28 | 1989-09-26 | Akira Minami | Focus servomechanism control system of optical disc system having offset setting means |
| DE3605561A1 (en) * | 1986-02-21 | 1987-08-27 | Thomson Brandt Gmbh | METHOD FOR COMPENSATING THE OFFSET VOLTAGE OF A CONTROL AMPLIFIER AND CIRCUIT ARRANGEMENT FOR IMPLEMENTING THE METHOD |
-
1987
- 1987-09-30 DE DE19873732997 patent/DE3732997A1/en not_active Withdrawn
-
1988
- 1988-08-19 EP EP88113479A patent/EP0309719B1/en not_active Expired - Lifetime
- 1988-08-19 ES ES198888113479T patent/ES2034068T3/en not_active Expired - Lifetime
- 1988-08-19 AT AT88113479T patent/ATE78624T1/en not_active IP Right Cessation
- 1988-08-19 DE DE8888113479T patent/DE3873004D1/en not_active Expired - Lifetime
- 1988-09-27 KR KR88012456A patent/KR960016359B1/en not_active Expired - Fee Related
- 1988-09-29 JP JP63242662A patent/JP2956770B2/en not_active Expired - Lifetime
- 1988-09-30 DK DK548288A patent/DK548288A/en not_active Application Discontinuation
- 1988-09-30 HU HU885108A patent/HUT63010A/en unknown
-
1992
- 1992-09-24 GR GR920402123T patent/GR3005801T3/el unknown
-
1996
- 1996-01-11 HK HK5696A patent/HK5696A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE3873004D1 (en) | 1992-08-27 |
| DK548288A (en) | 1989-03-31 |
| KR960016359B1 (en) | 1996-12-09 |
| ATE78624T1 (en) | 1992-08-15 |
| DE3732997A1 (en) | 1989-04-13 |
| DK548288D0 (en) | 1988-09-30 |
| EP0309719A1 (en) | 1989-04-05 |
| HUT63010A (en) | 1993-06-28 |
| ES2034068T3 (en) | 1993-04-01 |
| EP0309719B1 (en) | 1992-07-22 |
| GR3005801T3 (en) | 1993-06-07 |
| JPH01109539A (en) | 1989-04-26 |
| JP2956770B2 (en) | 1999-10-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PF | Patent in force | ||
| PE | Patent expired |
Effective date: 20080818 |