JPS60226030A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain always stable focus and tracking control by providing a differential amplifier circuit for detecting a differential signal of dividing photodetecting elements detecting focus or a tracking error, an additional amplifier circuit for detecting the signal summed up said dividing photodetecting element and a division circuit for dividing the differential signal by the sum signal. CONSTITUTION:When it is defined that a signal from the dividing photodetecting element 10a is (a) and a signal from the element 10b is (b), an output signal, i.e. a focus error signal, of the differential amplifier circuit 11 goes to (b-a) and an output signal 22 of the additional amplifier circuit 20 goes to (a+b). If the intensity of light detected by the dividing photodetecting elements at a recording time is k times that of reproducing, the error signal 21 goes to k(b-a). When the focus error signal 21 is divided by the sum signal 22 in the division circuit 23, the output signal 24 of the division circuit 23 goes to the formula I at a reproducing time and the formula II at a recording time, so that the values of the formulas I and II are always constant independently of the value of k. Consequently, the focus error signal 24 is not varied in both the recording and reproducing times.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to an optical recording/reproducing device.

[Prior art]

The focus control systems that have been proposed for optical recording and reproducing devices include the astigmatism method, the Naifetsu method,
The push-pull method, the 6-beam method, etc. have been proposed as tracking control systems using the critical angle method. These methods either use different optical systems or have the same control circuit system, as shown in the schematic diagram of FIG. A conventional example will be explained below with reference to FIG. 1oα, 1ob
is a split light-receiving element, in which a light beam from a laser light source or the like passes through an optical system, hits the information recording surface of the optical disk, and is reflected and guided. 10
Differential amplifier circuit 11 for detecting the difference signal between α and 1OA
As a result, a focus error signal 12 is obtained. This signal 12 drives the actuator 15 by the drive circuit 14, and seven orcus control is performed.

When recording information, the laser light source is pulse-modulated to record information on the optical disk, but the optical output at this time is several times stronger than that for reproduction, so the split light receiving element jug, The amount of light incident on 10b is also several times greater during recording than during reproduction. As a result, the focus error signal 1
2 becomes larger, the gain of the 7 orcus control system also becomes larger. In order to always perform constant focus control, a gain switching circuit 13 is required to switch the gain of the control system during recording and reproduction. Although 7 orcasing has been described above, tracking is also performed in a similar manner. However, with the above method, there is a problem in that the noise during gain switching causes 7 orcus deviations and track skips, which causes erroneous recording and erroneous playback. The purpose is to always perform stable focus and tracking control without having to switch the gains of the focus control circuit and tracking control circuit during recording and playback. An object of the present invention is to provide an optical recording/reproducing device.

〔overview〕

The optical recording/reproducing device of the present invention includes: a differential amplifier circuit for detecting a difference signal of divided light receiving elements for focus or tracking error detection; a summing amplifier circuit for detecting a sum signal of the divided light receiving elements; It is characterized by having a division circuit for dividing the difference signal by the sum signal.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples.

#! 2FXJ is a block diagram showing one embodiment of the present invention. In Figure 11M2, the same parts as in Figure 1 are indicated by the same numbers. Assuming that the signal from the divided light receiving element 10α is α and the signal from the split light receiving element 10b is b, the output signal 21 of the differential amplifier circuit 11, that is, the focus error signal is (b−α). On the other hand, the output signal 2 of the summing amplifier circuit 20
2 becomes ('10b). If the intensity of the light received by the divided light-receiving elements during recording is doubled during reproduction, the error signal 21 will be kb-, α=k(,6-α).On the other hand, the sum signal 22 will be &b+ α=k(b+α).When the focus error signal 21 is divided by the sum signal 22 by the division circuit 23, the output signal 24 of the division circuit 23 becomes as follows during reproduction.

(b-α)/(h+α) ・・・・・・When recording to the 0th order, k(b-α)/k(b+α) =(b-IL)/(b+a) ・-・・・■ . ■
The values of and ■ are always equal regardless of the value of k. In this way, the focus error signal 24 does not vary between recording and reproduction. The actuator 15 can be controlled by passing this error signal 24 through the drive circuit 14.

The above is an example of 7-orcus control, but tracking control can also be implemented using a similar method, so the details thereof will be omitted.

FIG. 3 shows the differential amplifier circuit 11 of FIG. Addition amplifier circuit 2
This is an example of an implementation circuit of the 0 and division circuit portions. 10t1
, 104 is a divided light receiving element such as a photodiode, 51
-52 is a preamplifier, 54, 57.42 is an operational amplifier,
43 is a multiplier.

A signal 32 obtained by amplifying the signal from the divided light-receiving element 10a by the preamplifier 30 is denoted by a8, and a signal 35 obtained by amplifying the signal from the divided light-receiving element 10A by the preamplifier 31 is denoted by a8.

A and bl are added by an adder circuit using an operational amplifier 54 to obtain a sum signal -As (αs+bs).

Here, A is the amplification degree of the adder circuit. On the other hand, by a differential amplifier circuit using an operational amplifier 37, (Ll and bl
The difference between A and A is calculated and is the difference signal 41.

(# J, % +&P Shinkai f-11? >> η
1 * IJ Ken Tom 416 represents the amplification degree of the width plane path.

Next, a multiplier 43 is inserted into the negative feedback part of the operational amplifier 42,
If the resistors 44 and 45 are set to the same value, a divider circuit that divides the difference signal 41 by the sum signal 40 is formed. Output 46 of the divider circuit
becomes as follows.

...■ Here, A3 is the amplification degree of the multiplier 43. Note that the amplification degree of each arithmetic circuit is Al m A! @'J are both positive values.

On the other hand, the signal α1. obtained from the split light receiving element. b.

Both include a reproduction signal component and a recording signal component.

In order to eliminate the influence of these components, the frequency response of the adder circuit is limited by the resistor 36 and capacitor '55, and the frequency response of the differential amplifier circuit is limited (to about 10 KEZ) by the resistor 39 and capacitor 58. For example, the signal 46 no longer includes a recording signal component.

〔effect〕

As described above, according to the present invention, stable focus and tracking control can always be performed even without a circuit for switching the gain of the focus control system during recording and reproduction.

Furthermore, due to variations in the light reflectance of the information surface of the optical disc, the error signal fluctuates and becomes difficult to focus.

Tracking will not become unstable. Further, the present invention has the advantage that recording and reproduction of a plurality of optical disks having different reflectances can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional optical recording/reproducing device. fM2 diagram is a block diagram of an embodiment of the present invention. FIG. 3 shows an embodiment of the division circuit section. 10α, 10b...Divided light receiving element 11...
... Differential amplifier circuit 13 ... Gain switching circuit 14 ... Drive circuit 15 ... Actuator 20 ... Addition circuit 23 ...・Divider circuit 30.5i... Preamplifier 34.37.42... Operational amplifier 43...
・Applicant for multipliers and above Patent attorney Tsutomu Mogami Suwa Seikosha Co., Ltd.

Claims (1)

[Claims] In order to correctly focus the light emitted from a light source such as a laser onto the recording surface of an optical disc (hereinafter referred to as focusing), the difference between the divided light receiving elements (1), such as the astigmatism method, Naifezi method, and critical angle method, is used. A focusing control system that uses the signal as a focus error signal, and a system for making the position of the light spot follow the reference groove (hereinafter referred to as pre-group) provided on the optical disk or the recorded pit row (hereinafter referred to as tracking). In an optical recording and reproducing apparatus having a tracking control system, which uses a difference signal from a divided light receiving element (2) such as a push-pull method; Mobiga tree method as a tracking error signal, the divided light receiving element (1)
and (2) an optical recording/reproducing apparatus, comprising a division circuit for dividing the sum signal and the tracking error signal by the sum signal.