JPS5845631A - Optical system driving device in recording information reader - Google Patents

Abstract

PURPOSE:To drive an optical system with less power consumption, by providing at least a pair of electromagnets which clip an optical system and drive it, flowing a current to the electromagnets alternately and driving them. CONSTITUTION:A lens barrel 1 made of a magnetic substance is driven with pair electromagnets 2a, 2b and 3a, 3b. In this case, tracking and tangential error signals are inputted to driving circuits 4a, 4b and transistor pairs Q1a, Q1b: Q2aQ2b are activated in response to the polarity of each error signal to switch a driving current applied to each electromagnet. Then, the direction of the force exerted to the lens barrel 1 made of the magnetic substance is inverted and a current only in response to the error signal is applied, allowing to improve the utility of a power supply.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical system drive device in a recorded information reading device.

In an optical recording information reading device, a video disk, which is an information recording medium, is formed with minute grooves (indentations) in the form of a spiral track according to the quality of the video on its surface. It records signals.

When using such a video disc, the disc is rotated at a predetermined number of revolutions and rotated on the first rack of the video disc. A beam of light is irradiated, and changes in the intensity of the reflected light or transmitted light are converted into electrical signals, which are then reproduced as a bio-based bow.

In the reproduction of a video disc (c), the irradiation light must be controlled in the radial direction of the disc, that is, in the direction of the driving force (Tranogingza, 'Ip), so that the four beams of light that illuminate the recording track must always be accurate.
It is necessary to control the tangential direction of the irradiation light to the track, that is, the Tanzen/He/Luca direction (Tanzen/Yalzer + 1
' )is necessary. There is a space for reading information, l
? Irradiate the recording light onto the disc]
- An optical system driving device is used that drives the Mero optical system according to a tracking error signal and a tanno-entical error signal. Of course, in order to accurately converge the irradiated light onto the recording surface of the disk, the position Nfl in the direction perpendicular to the recording surface of the optical system, that is, in the focus direction, is adjusted.
1 flil (focus direction 2j?) is also not performed.

Conventionally, various configurations of such optical system drive devices have been proposed. One of the methods is to place vibrating mirrors for tracking lasers and tanno-unshalzers in the optical path between the laser light source and objective lens that make up the optical system, and to use these vibrating mirrors for each error signal. Tracking direction and tank 1. - There is a configuration in which the optical axis is deflected in the longitudinal direction.

In such a configuration, in order to move 1+ light from the objective lens for deflecting the light incident on the objective lens by t'', a large deflection gap is required. As a result, it is necessary to have a wide field of view for the objective lens, which has disadvantages in terms of weight, size, and price.As another drive method, a moving coil (, +
There is also a so-called electrodynamic driving force method in which a p-Lewis coil is installed and the optical system is driven in combination with a fixed magnetic circuit, but since the coil is placed on the side to be driven, the direction in which the feed line is driven is You will need as many as you need. This is the biggest drawback in small and lightweight drive systems, and its effects on mechanical dynamics, mechanical reliability, and optical static r1'
t: There are some factors that cannot be ignored in terms of placement accuracy, etc., and if the coil becomes very small, the heat dissipation conditions for the heat generated will be poor, so the optical system components that are the driven objects will be affected. This will have a negative impact on Furthermore, when the drive coil becomes the driven body, J = the weight of the hem is the vibration wheel n.
Since l([] is added as 1, there is a disadvantage that the conversion dynamic name + is disadvantageous.

11 - In order to eliminate the above-mentioned drawbacks, a drive device that uses an electromagnet and uses the attractive force of the electromagnet to drive the optical system in a direction perpendicular to the optical axis 1 (tracking direction, tannoentical force direction) is JP-A-55-14 (i635
proposed in No.

When using an electromagnet, the force acting between the electromagnet and the driven object is proportional to the square of the magnetic flux, so if the magnetic flux proportional to the signal current of the 1sine wave is 13 = cosωt, the force is Proportional 1-1 A constant attractive force independent of frequency and a force at twice the frequency of the signal current are generated, and no force at the same frequency as the signal current is injected. However, if we add the DC deflection magnetic flux 13o, (1-3o+I(rncos bat) =I(o
-+-211o1. (,,cnsω is 10B,,,c
o s ωt, and the third term can be omitted under the conditions of 14o>>B, m,
A force with the same frequency as the signal current will be generated.

However, if the magnetic bias (DC deflection magnetic flux 11o) is increased by J, a direct current ffl, which is related to the input signal, will be generated and switched, so the bias must be canceled somewhere. This bias can be canceled by supporting the driven body with an elastic body and using the stiffness of the elastic body, but in this case, in order to widen the dynamic range, it is necessary to increase the distance between the electromagnet and the driven body. Also, it is necessary to provide enough DC magnetic field (DC bias) to prevent the generated magnetic field from becoming negative even at the maximum input signal. That is, even when the input signal is zero, a correspondingly large attractive force acts between the electromagnet and the driven body.

An elastic body with stiffness commensurate with its suction force.
When supporting a driven body, a fairly large stiffness is required regardless of its vibration weight.

On the other hand, once the stiffness and vibration weight are determined, the resonance frequency of the vibration system is determined, and below the resonance frequency there is a constant amplitude band, so the sensitivity of the acceleration amplitude is -12df1
/act attenuates toward the low range.

In other words, low frequency sensitivity deteriorates. This poses a big problem when it comes to singing. This is because, as described above, when trying to increase the maximum amplitude, the resonance frequency increases and the low frequency sensitivity decreases. -F: If a large DC magnetic field is generated to enable a large input signal to be input, an even greater stiffness is required, resulting in a vicious cycle in which the resonance frequency is discriminated.

For this reason, as mentioned above! In Samurai Kaisho 55-1.46635, problem 1-1 was fundamentally solved by generating a DC magnetic field from the opposite side instead of the stiffness of the elastic body and applying a force in the opposite direction. There is.

In other words, the electromagnetic force generated by the electromagnetic type has only an attractive force, so even if the magnetic field becomes fJ (the direction is reversed), the direction of the force does not change 1 to 1. Therefore, by applying a DC bias to an AC magnetic field, the direction of the magnetic field can be changed. This prevents reversal and cancels direct current forces by vector synthesis at the point of force application. This DC bias is shown in Figure 1 +"b"'lr
It is given by In this case, even when the current flowing through G71 is flowing through one electromagnet, the other electromagnet has I, #, □1. This means that a current is flowing, and a driving force is also generated in the opposite direction to the direction in which it is intended to be driven.

1. In the drive device of Japanese Patent Application Laid-Open No. 55-116635, The force generated against the drive current has components that cancel each other out, so it is inefficient, and since the current needs to flow, the negative 4■ is large and the power usage is poor. It has the disadvantage of being damaged.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide an optical system and a drive device in a recorded information reading device that can improve the utilization of power supply.

In the optical system 1 driving device according to the present invention, at least one pair of electromagnets are disposed opposite to each other with the optical system in between in a direction perpendicular to the optical axis of the optical system, and the pair of electromagnets When supplying a drive current according to a predetermined error signal, the drive current supplied to the pair of electromagnets is switched depending on the polarity VC of the predetermined error signal.

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 2 is a schematic perspective view showing a part of the optical system and the drive mechanism of the drive device according to the present invention. is configured. The lens barrel 1 is made of a magnetic material. The area around the 1/lens tube I is vertically 1-ff with respect to the optical axis 0.
The lens barrel 1
Two pairs of electromagnets 2a and 2h and 3a and 3b are arranged facing each other with the electromagnets 2a and 2h in between, and these constitute one driving mechanism in the dragging direction and the longitudinal direction. Note that a drive mechanism in the optical axis direction, that is, in the tannon-no-yarka direction is not illustrated. A support means (not shown) for the lens barrel is supported so as to be movable in the reno A-screw direction, the tracking direction, and the tansy L/y direction.

FIG. 3 is a circuit diagram showing the overall configuration of the optical system 1 driving device according to the present invention, in which a driving current is applied to electromagnets 2a, 2b, 3a, and 3b according to a predetermined error signal, that is, a tracking error signal and a Tanzen/Gill error signal. Drive circuits 4a and 4b are provided for supplying the power.

The drive circuit 4a includes a differential amplifier 5 whose non-inverting input terminal is grounded, a feedback resistor 1 connected between the output terminal of the differential amplifier and the inverting input terminal, and the output of the differential amplifier 5. A pair of linear transistors Q1a, Q1. and input resistance J(
,,1 becomes the inverting input of the differential amplifier 5!・Transistor Q1 (1
, , Ql are activated to switch the drive current supplied to the electromagnets 2a and 2b. Similarly, the drive circuit 4b includes a differential amplifier 6, transistors Q2a, +Q2b
, an input resistance layer, and feedback resistances n and f2, and a transistor Q2
a.Q2. The configuration is such that the drive current supplied to the electromagnets 3α and 3b is switched by operating the electromagnets 3α and 3b.

In this way, by switching the drive current supplied to the electromagnet pair according to the polarity of the error signal, it is possible to reverse the direction of the force acting on the lens barrel 1, and by supplying only the current according to the error signal. Because it is good, power usage can be improved. Ma/ζ, when an attractive force is acting on one electromagnet, the attractive force on the other electromagnet becomes zero, so the conversion efficiency improves. Historically, optical systems with good transmission characteristics can be easily driven because they can be driven directly without using an elastic body. At the same time, due to the small movement of the magnetic body (lens 1h1) in the magnet W, the electromagnetic braking effect on the abnormal vibration (() also becomes small.

In addition, in the embodiment (rc) described in "-", two pairs of electromagnets were provided and the structure was configured to be capable of driving in two force directions 'Fl perpendicular to the optical axis, but the structure is such that it can drive in only one direction. -) is also fine. Although a lens barrel made of a magnetic material is used, the same effect can be obtained even if the lens barrel is made of a non-magnetic material and a magnetic material is provided at least in the portion of the lens barrel that faces the electromagnet.

[Brief explanation of the drawing]

Fig. 1 is a waveform diagram for explaining the operation of the conventional example, Fig. 2 is a schematic perspective view showing a part of the drive mechanism of the optical system and drive device according to the present invention, and Fig. 3 1r, 1 according to the present invention. FIG. 2 is a circuit diagram showing the overall configuration of an optical system drive device. Explanation of symbols of main parts

Claims (1)

[Claims] 4P for reading information in the recording part of the recording medium
An optical system 1 driving device for driving an optical system for irradiating the optical system with at least one light 11 (i K force II 7 and I a pair of electromagnets, a magnetic body provided in a portion of the optical system that faces at least the pair of electromagnets, and a drive circuit that supplies a drive current to the pair of electromagnets according to a predetermined error signal. An optical system drive device in a recorded information reading device, wherein the drive circuit is configured to switch one drive current to be supplied to the pair of electromagnets in accordance with the polarity of the predetermined error signal.