JPS6010373B2 - optical recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an optical recording/reproducing device that uses a laser or the like to record a signal on a recording medium and reproduces it. The present invention relates to a recording/reproducing device.

Generally, when recording a signal on a recording medium optically, a lens is used to illuminate a light beam, and the recording medium is placed at a position with the highest energy density for recording.

By recording in this way, the recording density can be increased and recording can be performed using a light source with low radiant energy. However, when tracking and reproducing using a split analyzer, if the recording medium is placed at the position with the highest energy density, tracking will not occur. The reason for this will be explained using a simple optical system shown in FIG.

To simplify the explanation, the explanation will be based on geometric optics, and it will be assumed that there is no lens aberration. 1 is a light source, 2 is a condensing lens,
3 is a condensing point, 4 and 4' are analyzers, and 5 is a differential amplifier.

Reference numerals 6, 6', and 6'' are plates for blocking light, which are conveniently provided to explain the focal point.

When the plate 6 is moved in the direction of arrow B in the figure, the amount of light received by the analyzers 4, 4' changes, so that an output is generated in the differential amplifier 5. Also, when the plate 6'' is moved in the direction of the misprint, an output is generated in the differential amplifier 5. However, the plate on the condenser lens 2 side with the condensing point 3 as a 6 and when the plate 6'' on the detector 4.4' side is moved, the phase of the output of the differential amplifier 5 with respect to the direction in which the plate moves is completely opposite. When the plate 6' is moved in the direction of the arrow, the analyzer 4.
4' is simultaneously irradiated with light and not irradiated with light, so that no output is generated in the differential amplifier 5, and the output is always zero with respect to the movement of the plate 6'. Therefore, the focal point 3
Even if you place a recorded recording medium at the position and try to track the recorded track, tracking will not be possible because a tracking signal cannot be obtained. This is because even if a part of the condensing point, that is, the light spot in the general rule, is missing, the same amount of light will be irradiated to the analyzers placed at different positions, and no difference signal will be obtained. FIG. 2 shows that tracking is performed by receiving transmitted light with a split analyzer. 7 is a light source, 8 is a reflective mirror for tracking, 9 is a condensing lens, 10 is a recording medium, 11 and 11' are tracking analyzers, 12 and 12' are preamplifiers, 13 is a differential amplifier, and 14 is the aforementioned reflector. This is a drive circuit for the mirror 8.

Tracking signal detection in this case will be explained with reference to FIG. 3. FIG. 3 is an enlarged view of the recording medium 10. 15 is a track on which a signal is recorded, 16 is an unrecorded area between the tracks 15, and 17 is a light beam spot on the recording medium.

The difference in the amount of transmitted light between the recorded portion 15 and the unrecorded portion 16 is detected by the analyzers 11 and 11', and the reflecting mirror 8 is driven to perform tracking. In this case, as described above, if there is a focal point of the condenser lens 9 on the recording medium 10, no tracking signal is generated in the differential amplifier, so tracking cannot be performed. Therefore, during reproduction, the condenser lens 9 may be moved so that the condensing point of the condenser lens 9 is above or below the recording medium 10.

Conversely, the recording medium 10 may be moved, but it is very difficult to move the recording medium 10 because the amount of movement is extremely small. The above has described tracking performed by detecting the amount of transmitted light, but the same applies to tracking performed by detecting the amount of reflected light.

No matter what kind of structure the analyzer has, for example, even if it consists of a plurality of areas or a plurality of analyzers, the recording section 15 and the uninstalled green section 16 are Regarding tracking performed by detecting the difference in the amount of transmitted light or the amount of reflected light, if the focal point of the condensing lens 9 is on the recording medium 10, the tracking signal cannot be detected, so tracking cannot be performed. In view of the above-mentioned prior art, the present invention narrows down the light beam to the position with the highest energy density (
This problem is solved by shifting the position of the convergence point of the light beam.

The details of the present invention will be explained below with reference to the drawings. Fourth
The figure shows an embodiment of the present invention, in which tracking is performed using the amount of transmitted light and focusing is performed using the amount of reflected light.

13 is a light source, 19 is an optical modulator, 20 is a pinhole, 21
2 is an intermediate lens, 22 is a half mirror, 23 is a reflection mirror for tracking, 24 is a voice coil incorporating a condensing lens, 25 is a recording medium, 26 is a tracking analyzer, 27 and 27' are preambles, and 28 is a differential dynamic amplifier, 29
30 is a focusing analyzer, 31, 31' is a preamplifier 33 is a drive circuit for the voice coil 24, 34 is a switch, and 35 is a constant voltage device that outputs a constant voltage. Focusing involves detecting vertical fluctuations of the recording medium 25 with the analyzer 30,
This is done by driving the voice coil 24. In the case of records,
With the switch 34 open, the voice coil 24
Focusing control is applied so that the condensing point of the condenser lens incorporated in the condenser lens is located on the recording medium 25.

During reproduction, the switch 34 is short-circuited and a constant voltage is applied to the focusing control system. The sensitivity of the voice coil is X/V, the open loop gain of the focusing control system with respect to a constant voltage is G, the amplification factor of the drive circuit 33 with respect to a constant voltage is ○, and the output voltage of the constant voltage device 35 is V2 (wV). ), then approximately ×・G.・When reproducing V2/G (〃), the focusing position can be shifted. The opening and closing of the switch are completely reversed, and the switch 3 is
4 may be short-circuited to perform focusing control so that the light condensing point is on the recording medium 25, and during reproduction, the switch 34 may be opened to perform focusing control. Note that if a constant voltage is applied to the focusing control system that optically detects the light focusing position and electrically drives the focusing lens, an error in the focusing position will occur depending on the voltage, making it difficult to maintain a fixed light focusing position. It can be shifted.

As described above, in the present invention, during recording, the recording medium is directed to the part with the highest energy density, and during reproduction, since tracking cannot be performed as it is, a means is provided to control the positional relationship between the recording medium and the focal point. The present invention provides a device that has both recording and playback functions.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a condensing point in an optical recording/reproducing device, Fig. 2 is an explanatory diagram of a track recording device, Fig. 3 is a partially enlarged view of a recording surface of a recording medium, and Fig. 4 is an illustration of an embodiment of the present invention. FIG. 1 is a configuration diagram of an optical recording/reproducing device. 18...Light source, 22...Half mirror, 23. ...Reflection mirror for tracking, 24...
...Voice coil, 25...Recording medium, 26
...Tracking detector, 29...Drive circuit, 30... Focus control detector, 33...Drive circuit, 34...Switch, 35... Constant voltage source. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A light source that generates a light beam for recording and reproducing information, a lens for converging the light beam onto a recording medium, and a lens driving device for driving the lens to change the focal point position. A plurality of analyzers are arranged close to each other so as to simultaneously receive the reflected light or transmitted light of the light beam from the recording medium, and a tracking signal is obtained from the difference in output between the analyzers, and a tracking signal is obtained from the output difference between the analyzers. What is claimed is: 1. An optical recording and reproducing apparatus comprising means for controlling tracking, characterized in that the optical recording and reproducing apparatus is provided with means for changing the relationship between a recording medium and a focal point position during recording and during reproduction.