JPS6361427A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To read out a bit of recording information without saturating a signal detecting amplifier, by connecting in series a pair of photodetectors having photoelectric conversion functions in the direction of same polarity, and taking out a signal current equivalent to the difference of incident light quantities. CONSTITUTION:A magneto-optical pickup 13 is arranged oppositely to a magneto-optical disk 12 to be rotary-driven. A laser diode 15 is contained in the pickup 13, and an emitted laser beam is projected on the recording film 12a of the disk 12 through an objective lens 19. Reflected light is received at photodiodes (PD) 32A and 32B which form a signal detection circuit 31 passing through beam splitters 18 and 21, and analyzers 27A and 27B. The PDs 32A and 32B are connected in series in the direction of the same polarity, and the signal current equivalent to the difference of the incident light quantity from a connecting point connected in series, is taken out, and is inputted to an amplifier 33. The amplifier 33 converts and outputs the signal current to a voltage. Thus, it is possible to read out the bit of recording information without saturating the signal detecting amplifier.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an optical recording/reproducing device that detects differential signals by reducing the cost of bias voltage. [Prior Art] In recent years, the industry related to computerized information has made remarkable progress, and the information handled has changed dramatically. We are in a situation where the iI suspension is rapidly expanding. For this reason, it is now possible to optically record information at high density on a disc-shaped recording medium (hereinafter referred to as a disk) and to reproduce information at high speed by using laser light instead of conventional magnetic heads. The situation is such that optical recording and reproducing devices that can perform By the way, magneto-optical recording and reproducing devices that can freely rewrite and record recorded information are expected to be widely used in the future. In the above-mentioned magneto-optical recording and reproducing apparatus d3, the h method using a differential type is becoming mainstream as a signal detection system for detecting item (1) and converting it into an electric signal. This is because the noise caused by the birefringence caused by the disk substrate can be reduced by using the differential method. In magneto-optical disks, the medium is black and the LC Rayleigh light is
Based on the Vtk magnetic Kerr effect that receives polarized light in the direction of magnetization of the medium, the combination of "1" and "O" is used to detect magnetized information, but the Kerr rotation angle Since it is a very small angle, it is necessary to lower the angle 7 of the Cp detection system.In the conventional example, a differential amplifier 1 is used as shown in Fig. 5.In other words, from a disk (not shown) The returned light is received by the light-receiving elements of the bin photodiodes D1 and D2.The h-sodes of these bin photodiodes D+ and D2 are connected to the power supply terminal MO, respectively, and each anode is connected to an n-load resistor R, R
The signal is grounded through the terminal and applied to the input terminal of the differential amplifier 1. Since the anode potential changes due to the photocurrent corresponding to New Year's Day received by the diodes DI and D2, the differential valve of these seven node potentials is amplified and appears at the output terminal 2 of the differential amplifier 1. In the conventional example, for example, when a readout light is incident on the diode D1, a photocurrent flows in accordance with the readout light td, and the input No. 13 at the input end of the differential amplifier 1 becomes as shown in FIG. The signal component S due to the magneto-optical phenomenon is smaller than the bias component VB. This is the diode D+, which goes into D2 QJ
This is because the signal component due to the magneto-optical phenomenon in the return destination set is about one-tenth of that. Therefore, in order to fully extract the signal component appearing in the load resistor R, by making the load resistor R smaller and increasing the voltage VB, the change in the voltage component S of the small photocurrent becomes large. It becomes necessary to do so. If an attempt is made to sufficiently extract the signal component S in this manner, the DC bias component VB will increase. Since this DC bias component V[3 is input to the added state I' differential amplifier 1, only the differential valve is attempted to be amplified, and the DC bias component V 13 'b j
It is widened. [Problem to be solved by the invention 1] Therefore, in the conventional example described above, it is necessary to have an extremely wide dynamic range as an amplifier. - mode, during recording, amplitude-modulated laser light with high emission intensity is emitted, so that each of the differential amplifiers 1 as shown in FIG. 7(l) The amplitude input to the input terminal becomes small, causing the differential amplifier 1 to become saturated.When the differential amplifier 1 is saturated, as shown in FIG. 7(b), after the normal input is removed, However, a dead time Td occurs during which normal amplification cannot be performed for a while.
When this occurs, there are drawbacks such as the inability to read the address mark in the information area following the recording area. In addition, as shown in FIG. 8, current-voltage conversion amplifiers 3A and 3B are arranged on the anode side of the diodes Di and D2 to convert the photoelectric current 'flZ of each of the diodes D+ and D2 into a voltage with a width of 11. (There is a conventional example in which the input is input to the differential amplifier jS 1, but there is also a conventional example in which the input is input to the differential amplifier 1 after amplification. Furthermore, between the inverting input terminal and the output terminal of each amplifier 3Δ. ) ° = resistance rf
', rf are connected respectively. The conventional example J3 also suffers from the same drawbacks. The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an optical recording/reproducing device that can effectively extract only differential signal components without saturating the signal detection amplifier. . [Means and effects for solving the problem] In the present invention, a pair of photodetecting elements are connected in series in the same direction, canceling the in-phase component and outputting only one differential signal three components. By forming the signal detection means, it is possible to eliminate the influence of common mode components such as bias voltage and to effectively detect only differential signal components. [Example] The present invention will be specifically described below with reference to the drawings. 1 and 2 relate to a first embodiment of the present invention, FIG. 1 shows the circuit configuration of a signal detection circuit forming the first embodiment, and FIG. 2 shows a magneto-optical recording and reproducing circuit. Accepts Hikari Pai series. As shown in FIG. 2, a magneto-optical pickup 13 111 is a spindle U-type which faces a magneto-optical disk 12 which is rotationally driven. This (optical) pickup 13 is attached to the key 11 ridge 14.

['', (magneto-optical) disk 1
A field coil 14 for applying a bias magnetic field is arranged on the opposite side of the disk 12 from the pickup 13 in J3. Currents in opposite directions are passed during recording and erasing, and a bias magnetic field in the opposite direction is applied to the disk 12. A laser diode 15 is housed in the pickup 13, and the laser diode For example, the P-polarized laser beam emitted by the collimator lens 16 is made into a parallel beam by the collimator lens 16, and then enters the shaping prism 17.The shaping prism 17 converts the laser beam into a circular beam, which then enters the beam splitter 18. The light flux that has passed through the beam splitter 18 is focused by the objective lens 19 and irradiated onto the recording film 12a of the disk 12.The light reflected by the recording film 12a is directed in the direction of magnetization of the irradiated portion of the recording film 12a; In other words, depending on the N pole or the S pole, the plane of polarization rotates by a small angle in opposite directions (due to the magnetic Kerr effect).The light reflected by this recording 11012a is partially reflected by the beam splitter 18, and this reflected light is The light is further divided into reflected light and transmitted light by the beam brick 21.The reflected light is then incident on the critical angle prism 22, and the light reflected on the slope of the critical angle prism 22 is divided into four parts for control purposes. 1
1 detector 23 receives the light. A focus error signal is generated in this 4-split photodetector 23 in the vertically adjacent elements in Figure 2, and a focus error signal is generated in the vertically adjacent elements in Figure 2. A rack error signal is generated at the output. On the other hand, the light 1 transmitted through the beam splitter 21,
For example, if the light leakage direction is 1/2 wavelength plate 25 (K45°
After being rotated, the light enters a beam splitter 26 that transmits 50% of the light and reflects the remaining 50%, where it is divided into transmitted light and reflected light. Therefore, the transmitted light and the anti-Q4 light pass through the analyzers 27Δ, 27B, respectively, and are received by the bin photodiodes 32Δ, 32[3, which form the signal 8 detection circuit 31, which is the main part of the first embodiment. . The analyzers 27Δ, 27B are set so as to pass the light in the orthogonal polarization direction, or the light polarized in the angular direction rotated by the Kerr effect, and these analyzers 27Δ, 28Δ
The light that has passed therethrough is received by bin photodiodes 32A and 32B, which serve as detector elements for detection. Therefore, according to FIG. 1, the circuit configuration is reliable.
The recorded information can be read by adjusting the size of the disc to an appropriate size. Signal detection (pin) photodiode 32Δ. 32B are connected in series in the same polarity direction, and 1
The 1:c connected connection point is connected to the output terminal of the signal detection circuit 31 via the resistor R1', and is also connected to the inverting input terminal of the current-voltage conversion amplifier 33. Also, a photodiode 32A is connected in series. The cathode of one photodiode 32A and the anode of photodiode 32B in 32B are connected in series to bias power supply Vt+] and Vb2 (the positive electrode of one bias power supply Vb1 and the negative electrode of the other bias power supply Vb2). Both bias power supplies Vb, , Vb21.11 have equal voltages and are connected to the photodiodes 32Δ and 32B connected in series with equal voltages (overlapping with Vb), respectively (in the opposite direction). The connection point between these two bias power supplies Vb+ and Vb2 is the ground terminal of the analog signal 8 system, and the non-inverting input terminal of the amplifier 33 is connected to this terminal. is connected to the anti-IIλ input terminal and output terminal of the amplifier 33 for negative feedback. In the first actual flow example configured in this way, the dynamic f'F- will be explained below. Now, suppose that a snowy light is incident on both A-to-die A-dodes 32△ and 3213, and it passes through the first A-dode A-dore 32△ to lj
7L current flows into the inverting input *i: of the 4-radiator 33, and 7L current flows through the H inverting formula No. I7
If so, the absolute 1+a of the currents Ib+ and Ib- due to both are equal and the polarities are opposite, so the current flowing in and out of the inverting input terminal is killed by H1 and becomes zero. A1-
The differential valves 8 of guides 32Δ and 32B are manually operated at the inverting input terminals, and are hardly affected by the bias voltage at J3 in the conventional example. On the other hand, if there is a difference in the amount of light incident on the first diode 32, 32B by the amount of light J due to the Kerr effect, ΔIb = Ib- at the inversion horn end. -1b-
current flows. Therefore, the amplifier 33 is operated so that the potential at the inverting input terminal becomes zero (equal to the potential at the non-inverting input terminal, that is) with respect to the non-inverting input terminal, and as a result, the output An output voltage of VO=ΔIb−Rr is obtained. In other words, only the current of the differential valve is input to the amplifier 33, which converts it into a voltage and outputs it. Therefore, the drawback of the prior art in that the bias voltage is input to the input terminal of the amplifier and the signal cannot be sufficiently amplified is eliminated. Furthermore, since only the differential valve is input to the amplifier 33, it is possible to prevent the amplifier 33 from becoming saturated when the high-intensity ray+f is emitted when switching from the reproduction mode to the recording mode. Therefore, it is possible to prevent dead time from occurring in the conventional example. Therefore, according to the first embodiment, a sufficiently wide signal detection system can be used as a signal detection system without using a high voltage source. FIG. 3 shows a signal detecting circuit 41 in accordance with the second embodiment of the present invention (υ(iJ').
:33 is not used, both ]J1-diode 32Δ'. One end of the other negative resistor 1) r' is connected to the connection point of 32B' to form the output end of the detection signal 8. Also, this resistance r<r'
The other end is connected to the connection point of both bias power supplies vb1' and b2'. This embodiment is the same as the first embodiment by omitting the jM width transducer 33)
It has a similar wearing effect at 19. Incidentally, although the amplifier 33 can be omitted in this second embodiment, the voltage generated in the differential current J, C, and resistor Rf' between the two bias power supplies Vl11' and Vb2' is the bias voltage at J3. It is necessary that it is sufficiently small compared to the voltage (Vb'). Otherwise, the reverse bias and bias applied to each photodiode 32ΔI, 32@r will decrease, resulting in poor frequency characteristics.
Ru. FIG. 4t shows a signal detection circuit 51 in J3 according to a third embodiment of the present invention. This signal detection circuit 51 uses a constant cardiac pressure circuit 52 with good tracking characteristics to detect two bias voltages vb, -
vb(q) prevents bias voltage fluctuations from coloring the signal component. In other words, positive and negative voltages ←vi through the rectifier/smoothing circuit.
, -Vi, for example, one voltage +Vi is a three-terminal constant voltage IC53, etc., and the positive bias voltage Vb is 1"i. However, the output terminal of this IC53 and the output of the increase amplifier 54 (... A resistor R1, R1 with a characteristic of 11'A is connected between the two and the resistance value is 11'A. It is compared with the ground potential applied to the terminal.By this comparison, the output of the differential amplifier 55 is %::L, and the constant voltage IC
Constant current If-V of rl in conjunction with positive voltage b due to 53
b. In addition, there is a condenser C1 between the positive and negative output terminals and the ground.
CI is interposed and -C is present. In FIG. 1, the signal detection circuit 51 shown in FIG.
Bias 'Ichigen Vb1. The construction is the same as in FIG. 1 except that Vb2 is replaced with a constant voltage circuit 52. It is not limited to this, but can be widely applied to the detection system of optical recording and reproducing devices with a difference of 1' JJ signal 8. For example, 1 to 7/2 1
The same applies when detecting the signal g using the differential method using J3 in the control system of a pumping servo system or a fusing servo system';q. 'ru. In addition, tracking 1 Nobo system Dokafu A-Casing green-
When performing differential g detection for one cog signal in the bo system, the present invention uses υGJ g detection T
- If you go through the stages properly, you can amplify the focus error (ΔS) or track error (I) without saturating the bow, so it is possible to amplify the focus error (ΔS) or track error (I) without saturating the bow. [Effects of the Invention] As described above, according to the present invention, a pair of photodetecting elements that determine the photoelectric conversion capability are directly connected, and the connection point is Since a signal detecting means is formed to extract a signal current corresponding to the difference in the amount of light entering and entering both photodetecting elements, a differential signal can be extracted without saturation due to bias voltage.

[Brief explanation of the drawing]

1 and 2 relate to a first embodiment of the present invention, and FIG. 1 shows a signal detection circuit in the first embodiment.
The figure is a configuration diagram showing the optical system of the first actual droplet example, Figure 3 is a circuit diagram of the signal detection circuit included in the second embodiment of the invention, and Figure 4 is a circuit diagram of the signal detection circuit in the third embodiment of the invention. Circuit diagram showing the signal detection circuit, ≠≠Divider 4;=B=#S2C]2mBe3
-4 Ogami 4 cities 14 rows μ '-'--”-13-book 14↓
'JAL@;1i==d--5F path 4 Figure 2 Figure 5 shows the signal detection circuit of the conventional example 1'' circuit diagram, Figure 6 shows the signal applied to the input terminal in the conventional example of Figure 5 Figure 7 is an explanatory diagram showing how the amplifier becomes saturated when a large amplitude signal is input during recording in the conventional example J3, and Figure 8 is an explanatory diagram of another conventional example. This is a circuit diagram of the signal detection circuit. 11...Recording/reproducing device 12...(light) γ disk 13...Pickup 15...Sea 1f Gui A-do 1...Objective Lens 26... Beam bricks 27△, 27B... Analyzer 31... IΩ detection circuit 32△, 3213... Fold A1-Die Δ-D33...
Amplifier Fig. 1 Fig. 2 Fig. 7 Fig. 8 +V Fig. 3 Fig. 5 Fig. 4 Fig. 6

Claims (1)

[Claims] In an optical recording and reproducing device that reads recorded information using a differential optical system, a pair of photodetecting elements having a photoelectric conversion function are connected in series in the same polarity direction, and the connection point What is claimed is: 1. An optical recording/reproducing device comprising means for extracting a signal current corresponding to the difference in the amount of light incident on both photodetecting elements from the light detecting element.