JPH0411926B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing device.

Conventional configuration and its problems In an optical recording and reproducing device that records and reproduces information signals concentrically or spirally on a disc-shaped record carrier, a laser beam as a light source is directed to a recording site on the record carrier with a diameter of 1 μm. Focuses on a very small spot,
Performs high-density information recording and reproduction. For this reason, very high precision is required for focus control to accurately focus the laser beam onto the recording site of the record carrier.

FIG. 1 shows an example of a conventional optical recording/reproducing device. In the conventional apparatus shown in FIG. 1, a record carrier 1 is driven by an electric motor 2 at a predetermined rotational speed. The amount of light emitted from the laser light source 3 is controlled according to the output of the laser drive circuit 5, and during recording, the amount of emitted light is intensity-modulated according to the output of the recording signal 6, and during reproduction, the amount of light emitted is controlled to be a weak reproduction light amount. be done. A beam 4 emitted from a laser light source 3 passes through a beam splitter 7 and a mirror 8 vibrated by a tracking drive element 9, and is projected onto a recording region of the record carrier 1 by a condenser lens 10. In this apparatus, in order to position the recording portion of the record carrier 1 at a position where the light beam 4 is most focused by the condensing lens 10, the reflected light from the record carrier 1 is directed to the mirror 8 and the beam splitter 7. The light is guided to the cylindrical lens 11 through the cylindrical lens 11, and the light shape of the cylindrical lens 11 is detected by the photodetector 12 to detect the distance between the condenser lens 10 and the recording site of the record carrier 1,
The focus control circuit 13 directs the condenser lens 10 to a luminous flux 4.
A focus control system was constructed by controlling the coil current of a focus drive element 14 of a voice coil motor type that moves in the direction of the optical axis. Laser light source 3, beam splitter 7, mirror 8, tracking drive element 9, focusing lens 10, focus drive element 14, cylindrical lens 11, photodetector 12
The optical system is installed on a transfer table 16, and the transfer table 16 is moved in the radial direction of the record carrier 1 by a transfer motor 17 to set the recording/reproducing position. During reproduction, in order for the light beam 4 to accurately trace the recording track, the relative positional relationship between the light beam 4 and the recording track is detected by the photodetector 12, and the tracking drive element 9 is controlled by the tracking control circuit 15. to perform tracking control.

In this device, a beam splitter 7, a cylindrical lens 11, and a photodetector 1, which constitute a focus detection optical system, are used to position the recording portion of the record carrier 1 at the position where the light beam 4 is most focused.
It is necessary to finely adjust the settings in step 2 and set them with high precision of several microns. Especially when recording,
In addition to utilizing the output light of the light source 3, in order to achieve high-density recording, a condensing lens 10 that generally has a large aperture NA is used, so the position of the recording region of the record carrier 1 is approximately ±1 μm from the convergence position of the light beam 4. must be located with high precision. Therefore, a particularly highly accurate focus detection optical system is required.

However, it is difficult to maintain such a highly accurate focus detection system over a wide temperature range and over a long period of time due to changes due to distortion of the mechanism mounting mechanism due to temperature changes, changes in the temperature characteristics of the photodetector 12, changes over time, etc. It was difficult.

OBJECT OF THE INVENTION The present invention aims to provide a device that compensates for the effects of such temperature changes and changes over time, accurately focuses a beam of light onto the recording site of a record carrier, and always provides optimal recording and reproducing characteristics. This is the purpose.

Structure of the Invention In order to achieve the above object, the present invention provides a record carrier having a recording track on which an address signal is recorded in advance, a light source for recording a signal on the record carrier, and a light source for recording a signal on the record carrier. an optical system for converging and irradiating an output light beam onto the recording region of the record carrier; a means for detecting a state in which the light beam of the light source is focused on the recording region of the record carrier; and an output of the detecting means. focus control means for controlling the convergence state; adjustment means for adjusting the state of the focus control means; and amplitude detection means for reproducing the address signal recorded on the recording track and detecting the reproduced amplitude of the address signal. The apparatus further includes logic control means for detecting the output of the amplitude detection means and controlling the adjustment means.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the drawings. FIG. 2 shows a record carrier 1 used in the present invention. The record carrier 1 is provided with recording tracks 21 as track grooves for clarifying the position where signals are recorded, and each groove track has a track groove. An address signal 22 corresponding to the address signal 22 is recorded in advance using an optical method such as a concavo-convex pattern or a bright/dark pattern.

A method of recording a signal on the recording track 21 of such a record carrier 1 will be explained with reference to FIG. Components in FIG. 8 that are similar to those in FIG. 1 are designated by the same numbers. The record carrier 1 is rotated by an electric motor 2 at a predetermined number of rotations. The luminous flux 4 of the laser light source 3 emitted by the drive circuit 5 with a drive current according to a signal passes through a spot lens 23, a beam splitter 7, a tracking mirror 8, and a condensing lens 10, and is irradiated onto the recording region of the record carrier 1. be done. In order to accurately irradiate a signal onto the recording track 21 in FIG. 2, a tracking servo similar to the conventional example shown in FIG. 1 is required. Furthermore, it is necessary to accurately focus the light beam 4 on the recording site of the record carrier 1, but the focus control system constituting this servo system is required to have extremely high precision as described above. However, the conventional control system has the disadvantage that it cannot cope with temperature changes and changes over time in components, etc., but the present invention improves these conventional drawbacks. That is, the light beam 4 irradiated onto the recording area of the record carrier 1 is reflected and returns to the condensing lens 1.
0, is reflected by the beam splitter 7 through the tracking mirror 8, and is reflected by the cylindrical lens 1.
1 and is irradiated onto a photodetector 12. Photodetector 1
2 is composed of four photodetector elements (a), (b), (c), and (d). The outputs of the elements (a) and (c) are added to the adder circuit 24, and )(d) output is the adder circuit 25
is added to and added to. The outputs of the adder circuits 24 and 25 are added to the differential amplifier circuit 26 and added to the adder circuit 2.
4 and the adder circuit 25 is obtained. The output of the differential amplifier circuit 26 is a signal corresponding to the relative position between the recording area of the record carrier 1 and the condensing lens 10. In the conventional apparatus, the optical system is configured such that when the output voltage of the differential amplifier circuit 26 becomes approximately 0, the emitted light beam 4 of the laser light source 3 is irradiated to the recording region of the record carrier 1 in the most converged state. The control system is configured so that the output of the differential amplifier circuit 26 is always approximately zero. However, with this method, if the optical system changes due to temperature or the like, that is, if the set position of the optical components (including the photodetector 12) changes due to temperature, or if the elements of the photodetector 12 and the addition circuit 24 , 25. When the differential amplifier circuit 26 causes output fluctuations due to temperature or due to aging of components, the convergence state changes, the recording state changes and the recording characteristics deteriorate, In a bad case, the light beam 4 will not be converged on the recording area of the record carrier 1, and the spot diameter will become large, resulting in a case where no recording is made.

In FIG. 3, the output of the differential amplifier circuit 26 is amplified by an amplifier circuit 27, and then passed through a drive control circuit 28 to drive a voice coil motor type focus drive that moves the condenser lens 10 in the optical axis direction of the condenser lens 10. A conventionally known focus control system is configured by controlling the coil current of the element 14. Furthermore, addition circuit 2
The outputs of 4 and 25 are summed and amplified by a summing amplification circuit 29. The output of the summing amplifier circuit 29 corresponds to the output of the signal recorded on the recording track 21. Therefore, during reproduction, this signal serves as a reproduction output of the address signal and information signal recorded on the recording track 22. If no information signal is recorded on the recording track 22, only the address signal is reproduced. The amplitude of this reproduction signal corresponds to the state in which the laser beam 4 is focused on the recording region of the record carrier 1, and when this reproduction signal is at the maximum, the laser beam 4 is most concentrated on the recording region of the record carrier 1. It becomes a state of being. Therefore, if the control system is configured so that the reproduced signal is always approximately at its maximum, the focus control system will always be optimal, and if recording is performed in this set state, optimal recording can be performed. The output of the amplitude detection circuit 30 is A/D converted by an A/D converter 31, and the output is detected by a logic control circuit 32. The logic control circuit 32 is an A/D
Detects the state where the output of converter 31 is maximum,
The focus control system is finely adjusted by controlling the output voltage of the fine adjustment voltage generating circuit 33, and the convergence position of the light beam 4 is finely adjusted.

When recording information signals with this device,
First, the apparatus is put into a reproduction mode, and the drive circuit 5 is controlled by the logic control circuit 32 to turn the output light of the laser light source 3 into a weak reproduction light, which is irradiated onto the recording track to be recorded. Therefore, the address signal of the recording track is reproduced and detected as the output of the A/D converter 31. Next, the logic control circuit 32 changes the fine adjustment voltage generation circuit 33 in either direction to obtain a corresponding reproduction signal, but if the output is in the direction of increasing, it changes the output until it continues to increase and addresses the The position where the reproduction amplitude of the signal reaches its peak is detected, and the fine adjustment voltage generation circuit 33 is set.
After the fine adjustment voltage generation circuit 33 is set, the logic control circuit 32 switches the drive circuit 5 to the recording mode and records the information signal. Although it is possible to set such optimal conditions for each recording, it is recommended that you turn off the power to the device based on the general usage conditions, etc.
It may be configured to be performed only the first time it is turned on. In this way, optimal recording can always be performed regardless of temperature and changes over time. At the time of reproduction, the recording track 22 to be reproduced may be irradiated with the light beam 4 to maximize the reproduction amplitude of the address signal, or the information signal may be reproduced.

Note that the present invention is not limited to this example,
Various modifications can be made.

Effects of the Invention According to the present invention, the temperature and temporal change of the optical system,
Furthermore, it is possible to always obtain optimal recording and reproducing conditions regardless of the temperature of the photodetecting element and the circuit system and changes over time, and the quality of recording and reproducing signals can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional apparatus, FIG. 2 is an explanatory diagram of a record carrier used in the present invention, and FIG. 3 is a schematic diagram of an embodiment of the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Record carrier, 3... Laser light source, 7... Beam splitter, 8... Mirror, 10... Condensing lens, 12... Photodetector, 14... Focus drive element, 21... Recording track , 22... Address signal, 24, 25... Addition circuit, 26... Differential amplifier circuit, 28... Drive control circuit, 29... Addition amplifier circuit, 30... Amplitude detection circuit, 31...
A/D converter, 32...logic control circuit, 33
...Fine adjustment voltage generation circuit.

Claims (1)

[Claims] 1. A record carrier having a recording track on which an address signal is recorded in advance, a light source for recording a signal on this record carrier, and an optical system for converging and irradiating the output light beam of this light source onto the recording part of the record carrier. a system, means for detecting a state in which the light beam of the light source is focused on a recording region of the record carrier, a focus control means for controlling the convergence state based on the output of the detection means, and a state of the focus control means. an amplitude detecting means for reproducing the address signal recorded on the recording track and detecting the reproduced amplitude of the address signal; and detecting an output of the amplitude detecting means to control the adjusting means. 1. An optical recording/reproducing device characterized by having a logic control means for controlling