JPH034976Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial use) The present invention is an optical recording and reproducing device that optically records or reproduces information (including devices that have both recording and reproducing functions as well as devices that only have a reproducing function). ) regarding
In particular, it obtains a control signal for controlling the focus or tracking state of recording or reproducing incident light.

(Prior art and its problems) In an optical recording/reproducing device, a minute spot of incident light for recording or reproduction is always imaged on the information recording surface of the disk, and the focus and the spot are adjusted so that this minute spot follows the information track. Tracking servo is performed, and error signals for the focus and tracking servo are generated by receiving the reflected light from the disk with a detector consisting of, for example, four-divided photoelectric conversion elements, and converting the electrical signals extracted from each photoelectric conversion element into a predetermined signal. After adding the combinations of , they are obtained by forming a difference signal of the added signals.

However, since incident light with different power is used during recording and playback, and there are also variations in the light reflectance of the disk, these factors change the amount of light received by the detector, which may affect the magnitude of the error signal. There is a problem that the gain of the servo loop changes.

(Means and effects for solving the problems) The device of the present invention solves the above problems, and receives the transmitted or reflected light from the disk in parts and generates a difference signal between the corresponding electrical signals. means for obtaining a first electric signal; means for obtaining a second electric signal corresponding to the total amount of received light from the sum signal of the electric signals; and means for obtaining a division signal obtained by dividing a reference voltage by the second electric signal. , comprising means for multiplying the first electric signal and the division signal to obtain a multiplication signal, and using the multiplication signal as a control signal to a focus or tracking servo circuit,
The magnitude of the control signal is controlled according to the amount of light received, and is not changed by changes in the power of the incident light or changes in the optical reflectance of the disk.

(Example) Hereinafter, an example of the device of the present invention will be described with reference to the drawings.

In the figure, laser light emitted from a light source such as a semiconductor laser is converted into approximately circular parallel light through a collimating lens, a shaping prism, etc., and then passes through a beam splitter 1, a λ/4 plate 2, and an objective lens 3 to a disk. The recording or reproducing incident light is focused on the information recording surface of No. 4 as a minute spot.

On the other hand, the reflected light from the disk 4 returns to the incident optical path, but the reflected light from the beam splitter 1 passes through the cylindrical lens 5 and is received by the detector 6, which is made up of four photoelectric conversion elements 6a, 6b, 6c, and 6d. Ru. 7 and 8 are focusing and tracking actuators, respectively, which move the objective lens 3 in the vertical and horizontal directions in response to the respective outputs from the drive circuits 9 and 10.

Here, in the well-known astigmatism method using the cylindrical lens 5, the electric signals Sa, Sb,
For example, the addition signal (Sa + Sb), (Sc
+Sd) difference signal (Sa+Sb) - (Sc+Sd) to obtain the focus error signal, and the addition signal (Sa+Sc),
Tracking error signals can be obtained from the difference signal (Sa+Sc)-(Sb+Sd) of (Sb+Sd). In the figure, adders 11 to 14
are the addition signals (Sa+Sb), (Sc+Sd), and (Sa
+Sc), (Sb+Sd), and differential amplifier 1
5 and 16 are the difference signals (Sa+Sb)−(Sc+
Sd), (Sa+Sc)-(Sb+Sd).

The addition signal (Sa+Sb) from the adder 11 is sent to the amplifier 17, and the addition signal (Sc) from the adder 12 is sent to the amplifier 17.
+Sd) is input to the differential amplifier 15 via the amplifier 18, but one of the amplifiers 18 has a variable gain and is offset-adjusted at this stage. Similarly, adders 13 and 14 and differential amplifier 1
Amplifiers 19 and 20 are provided between the two amplifiers 6, and the gain of one amplifier 20 is variable.

Each difference signal from differential amplifiers 15 and 16 is input to multipliers 21 and 22, respectively. On the other hand, the adder 23 outputs an addition signal (Sa+Sb+
Sc+Sd), and this addition signal is sent to the divider 24
is input.

Here, for the multipliers 21, 22 and the divider 24, for example, a four-quadrant analog multiplier (linear IC8013) manufactured by Intersil Corporation of the United States is used, and in the multipliers 21, 22, the input signal to the X input terminal When the input signal to the X, Y input terminal is Y, the multiplication signal X・Y/10 is output, and in the divider 24, the input signal to the If Z, the division signal 10.Z/X is output.

The X input terminal of the divider 24 receives an addition signal corresponding to the total amount of received light, and the Z input terminal receives the reference voltage signal Vref, and the division signal of the divider 24 is a low-pass signal. The signals are inputted via the filter circuit 25 to the Y input terminals of the multipliers 21 and 22, respectively. The above difference signals are input to the X input terminals of the multipliers 21 and 22, respectively, and the multiplication signals of the multipliers 21 and 22 are input to the drive circuits 9 and 10 as focus and tracking error control signals Sfe and Ste. be done.

In the above configuration, the detector 6 due to a change in the power of the incident light or a change in the optical reflectance of the disk 4
The rate of change in the amount of received light at is expressed as H, and for simplicity, the difference signal to the multipliers 21 and 22 and the total amount of received light signal to the divider 24 are expressed as Sd and St, respectively. The signal is 10·Vref/H·St, and the focus or tracking error control signals Sfe and Ste input from the multipliers 21 and 22 to the drive circuits 9 and 10 are H·Sd/10×10·Vref/H·St. = Sd・Vref/St, and it is possible to obtain focus or tracking error control signals Sfe and Ste that are not affected by changes in the power of the incident light or changes in the light reflectance of the disk 4, resulting in always stable and accurate focus or tracking servo control. becomes possible.

Although the above embodiment has been described in relation to a device that detects focus and tracking error signals using the astigmatism method, it goes without saying that the present invention can also be applied to devices that use other detection methods such as the critical angle method. Moreover, it can be applied to devices that utilize not only reflected light but also transmitted light, and various other aspects can be changed without being limited to the embodiments.

(Effects of the invention) According to the invention described above, it is possible to realize an optical recording/reproducing device equipped with a focus or tracking servo system that is always stable and accurate without being affected by changes in the power of incident light or changes in optical reflectance of the disk. .

[Brief explanation of drawings]

The figure shows a block diagram of essential parts of an embodiment of the device of the present invention. 3... Objective lens, 4... Disc, 6... Detector, 6a, 6b, 6c, 6d... Photoelectric conversion element, 9, 10... Drive circuit, Sa, Sb, Sc, Sd
... Electrical signal, 11-14 ... Adder, 15,1
6... Differential amplifier, 21, 22... Adder, 24
...Divider, Sfe, Ste...Control signal, Sd...Difference signal, St...Sum signal.

Claims (1)

[Claims for Utility Model Registration] In an optical recording/reproducing device equipped with a focus or tracking servo circuit that controls the focus or tracking state of incident light on a disk, the transmitted or reflected light from the disk is received in divided light and the corresponding response is achieved. The first signal, which is the difference signal between the electrical signals
means for obtaining an electrical signal, means for obtaining a second electrical signal corresponding to the total amount of received light from the sum signal of the electrical signals, and means for obtaining a division signal obtained by dividing a reference voltage by the second electrical signal; An optical recording/reproducing apparatus comprising: means for multiplying the first electric signal by the division signal to obtain a multiplication signal, the multiplication signal being used as a control signal to the focus or tracking servo circuit.