JPS6199946A - Optical information reproducing device - Google Patents

Abstract

PURPOSE:To execute automatically and quickly a strong adjustment against a flaw of a recording carrier and a variation of a reflection factor or a transmittivity by reading the information in accordance with the output from a recording signal component detecting means for detecting a recording signal component, and adjusting the DC bias voltage of a position control means. CONSTITUTION:When an error signal is selected by switching a changeover switch 23, a focused point control system is oscillated by the second offset component in the error signal, and a voltage corresponding to a relative position error generated at that time appears. In this case, when a recording signal component contained in the error signal is detected by a recording signal component detecting means 22, and a bias adjusting means 9 is adjusted so that the recording signal component goes to '0', the second offset component also goes to '0'. A balance adjustment is executed in a state that the relative position error is minimum, therefore, it is unnecessary to execute repeatedly the balance adjustment and the bias adjustment. Therefore, a strong adjustment against a flaw of a recording carrier, and a variation of a reflection factor and a transmittivity can be executed automatically, quickly and exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information reproducing device for optically reading information from a record carrier having information tracks.

Conventional Structures and Problems There are already commercially available optical data files, video disc players, continuous disc players, and the like as information reproducing devices that optically read information from a record carrier having an information track. These information reproducing devices require accurate tracking control and focusing point control because of their high recording density. For example, in the tracking control of a compact disc player, it is necessary to suppress the tracking error to 0.1 μm or less for an eccentricity of several hundred μm. In addition, it is necessary to control the focusing point to a focusing error of 1 μm or less for a surface runout of several hundred μm. If there is a scratch on the record carrier and a disturbance enters the tracking control system or focus control system, the control system will be disturbed and the track will jump to a nearby track or go out of focus depth, making it impossible to read the information. Something happened. This tendency was particularly noticeable in compact disc players with slow track linear speeds, as the passage time through the defective portion was long. Therefore, the tracking control system and focusing point control system must be adjusted so that the control systems are not shaken by scratches on the record carrier.

FIG. 1 is a block diagram showing an example of a focusing point control system of a conventional information reproducing device, in which 1 is an information track, 2 is a record carrier, and 3 is a focusing point control system.
is a light source, 4 is a beam splitter, S is a focus lens, 6 is a photoelectric converter, 7 is /< lance adjustment means, 8 is a differential amplification means, 9 is an offset adjustment means, 10 is a gain adjustment means, 11 is a light spot movement means, 12 is a differential amplifier;
13 is an adder, and 14 is a recording signal reading means.

The operation of the focusing point control system configured as described above will be briefly explained below. The light beam generated from the light source 3 is transmitted to a beam splitter 4. A very small light spot is connected to the information track 1 on the record carrier 2 through the focus lens 6, and after being modulated according to the state of the information track 1, it enters the focus lens 6 again and is reflected by the beam splitter 4. An image is formed on the photoelectric converter 6. The output of the photoelectric converter 6 is combined by an adder 13, and outputs the original recording signal according to the state of the information track 1, and also outputs a signal according to the relative position error between the focal position (minimum light spot position) and the information track. Outputs a detection signal pair. The method of obtaining the detection signal pair is 2.
The astigmatism method utilizes the fact that the shape of the image on the photoelectric converter changes according to the relative position error using two lenses with astigmatism in different directions, and the critical angle of the prism is used. The critical angle method, the Fuco method using Naifetsugi, etc. are generally known. The pair of detection signals is adjusted by the balance adjustment means 7 so that their levels are equal when the relative position error is 0, and then the difference is taken by the differential amplifier 12 to produce an error signal that fluctuates plus or minus depending on the relative position error. Become. The balance adjustment means 7 and the differential amplifier 12 constitute a differential amplification means 8. The error signal is amplified to a required amplitude by the gain adjustment means 8, and the optical focus moving means 11 moves the focus lens 5 to align the focal position with the information track. The offset adjustment means 9 is provided to cancel electrical and mechanical unbalanced components of the focusing point control system. Here, after the focus position is adjusted by the offset adjustment means 9, when the level of each pair of detection signals is adjusted to be equal by the balance adjustment hand 7, a deviation from the previously adjusted focus position occurs. For this reason, it is actually necessary to perform offset adjustment and balance adjustment alternately and repeat them, and there are disadvantages such as it takes time to automatically perform offset adjustment and /(lance adjustment), and it does not match the optimal value. Furthermore, even if the balance has already been adjusted by some method, if the error rate of the signal read from the information track is used to detect the focal point position, there is a drawback that the offset adjustment takes time.

Purpose of the Invention The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide an optical information reproducing device that automatically and quickly makes strong adjustments against scratches on a record carrier and changes in reflectance and transmittance. be.

Structure of the Invention The present invention comprises a record carrier having an information track written with a recording signal modulated so that the direct current component does not change, a light source that generates a luminous flux, and an optical convergence means that connects a very small light spot to the information track. and at least one set of detection devices that read the recorded signal from changes in reflected light or transmitted light from the information track, and differentially change depending on the relative position error between the information track and the optical spot. information reading means for outputting a signal pair; differential amplification means for differentially amplifying the detection signal pair and outputting an error signal; and moving the optical spot so as to minimize the relative position error based on the error signal. a recording signal component detection means for detecting the recording signal component of the error signal; and a recording signal component detection means for detecting the recording signal component of the error signal; It is equipped with a bias adjustment means for adjusting the DC bias voltage of the position control means consisting of a light spot moving means, and automatically and quickly makes strong adjustments against scratches on the record carrier and changes in reflectance and transmittance. It is something that can be done.

DESCRIPTION OF EMBODIMENTS FIG. 2 is a block diagram showing an embodiment of the present invention, in which 1 is an information track, 2 is a record carrier, 3 is a light source, 4 is a beam splitter, 6 is a focus lens, 6 is a photoelectric converter, 7 is a balance adjustment means, 8 is a differential amplification means, 9 is an offset adjustment means, 1o is a gain adjustment means, 11 is a light spot moving means, 12 is a differential amplifier, 13 is an adder, 14 is a recording signal reading means, 2o is a sub-differential amplification means, 22 is a recording signal component detection means, and 23 is a changeover switch. 6
The operation of the focusing point control system of the optical information reproducing apparatus in this embodiment configured as described above will be described below. The luminous flux generated from the light source 3 passes through the beam splitter 4
．． A very small light spot is connected to the information track 1 on the record carrier 2 through the focus lens 6, and after being modulated according to the state of the information track 1, it enters the focus lens 5 again and is reflected by the beam splitter 4. An image is formed on the photoelectric converter 6. The photoelectric converter 6 applies an information signal according to the state of the information track 1, and outputs a pair of detection signals according to the relative position error between the focal position (minimum light spot position) and the information track. The detection signal pair is balanced by the balance adjustment means 7.
The difference is removed by the differential amplifier 12, resulting in an error signal that swings positive or negative depending on the relative position error. The balance adjustment means 7 and the differential amplifier 12 constitute a differential amplification means 8. Further, the sub-differential amplification means 20 generates a sub-error signal by simply taking the difference between the pair of detection signals. After the sub error signal and the error signal are switched by a changeover switch 23, they are amplified to a required amplitude by a gain adjustment means 8, and a light spot moving means 11 moves a focus lens 6 to align the focal position with the information track.

The offset adjustment means 9 is an electrical part of the focusing point control system.

It is provided to cancel mechanical unbalance components. Here, the error signal before adjustment includes a first offset component that fluctuates due to changes in light intensity caused by positional deviation of the photoelectric converter 6 or variations in each gain, and a first offset component that fluctuates due to changes in light intensity caused by positional deviation of the photoelectric converter 6 or variations in each gain, and a first offset component caused by offset voltage of the circuit or adjustment deviation of the mechanical system. A second offset component that does not vary due to changes in the amount of light is included. The first offset component is applied to the balance adjustment means 7, and the second offset component is applied to the bias adjustment means 9. However, in general, each offset component cannot be separated when there is no change in the amount of light. However, since the amount of light incident on the photoelectric converter 6 changes depending on the recording signal, it is sufficient to examine how the error signal changes. Therefore, first, the changeover switch 23 is switched to select the sub-error signal, and the offset adjusting means 9 adjusts the sum of the first offset component and the second offset component to 0, thereby minimizing the relative position error. In this state, the recording signal component included in the error signal is detected by the recording signal component detecting means 22, and the balance adjusting means 7 is adjusted so that the recording signal component becomes zero. For example, since the recording signal used in a compact disc player is modulated so that the DC component does not change, the recording signal component detection means 22 changes the polarity of the error signal depending on, for example, 1.0 of the recording signal. The configured synchronous detection circuit can be used. When the relative position error is the minimum in the above adjustment, the error signal does not include the first offset component. Next, when the changeover switch 23 is switched to select the error signal, the focusing point control system is swayed by the second offset component in the error signal, and a recording signal component corresponding to the relative position error that occurs at that time is recorded. If the bias adjustment means 9 is adjusted so that the recording signal component detected by the signal component detection means 22 becomes O, the second offset component also becomes zero. That is, with this configuration, the balance adjustment is performed until 't' when the relative position error is minimum, so there is no need to repeatedly perform balance adjustment and bias adjustment. In addition, if the balance has already been adjusted by some means or if balance adjustment is not necessary, the recording signal component detection means 22 simply detects the recording signal component included in the error signal so that the recording signal component becomes 0. It is only necessary to adjust the bias adjustment means 9 accordingly. Although the focused point control system has been described here, it is not limited to the focused point control system, but may also include, for example, a tracking control system that uses a tracking error detection method that utilizes the fact that the far field image of the information track changes due to diffraction of the information track. It is clear that the present invention is also applicable to

Effects of the Invention As is clear from the above description, the present invention provides a record carrier having an information track on which a recording signal modulated so that the direct current component does not change, a light source that generates a luminous flux, and a light source that generates a luminous flux on the information track. An optical convergence means that connects a very small light spot, reads information from changes in reflected light or transmitted light from the information track, and differentially reads information based on a relative positional error between the information track and the optical spoiler/above. information reading means for outputting at least one pair of changing detection signals, differential amplification means for differentially amplifying the pair of detection signals and outputting an error signal, and minimizing the relative position error from the error signal. and a recording signal component detection means for detecting the recording signal among the error signals, and an information reading means according to the output of the recording signal component detection means; It is configured to have a bias adjustment means for adjusting the DC bias voltage of the position control means consisting of the differential amplification means and the optical spot moving means, and the balance has already been adjusted by some means, or the balance adjustment If this is not necessary, it is possible to automatically and quickly make adjustments that are strong against scratches on the record carrier and changes in reflectance and transmittance.

Even when balance adjustment is required, the differential amplification means includes balance adjustment means for changing the gain for one signal of the pair of detection signals relative to the gain for the other signal, and furthermore, the differential amplification means and a sub differential amplification means connected in parallel with the detection signal image pair to differentially amplify the pair of detection signal images and output a sub error signal, and inputting either the error signal or the sub error signal to the optical spot moving means. and a changeover switch for inputting the sub-pigeon difference signal to the light spot moving means, and when the changeover switch is closed on the side where the sub-pigeon difference signal is input to the optical spot moving means, the information reading means and the sub-direction switch are arranged so that the relative position error is minimized. Differential amplification means.

Adjusting the DC bias of the sub-position control means consisting of the light spot moving means, and in this state adjusting the balance adjustment means 5 according to the output of the recording signal component detection means;
The changeover switch is configured to be closed on the side where the error signal is input to the optical spot moving means, and since there is no need to perform balance adjustment and bias adjustment, it is possible to It is possible to automatically, quickly and accurately make adjustments that are strong against scratches and changes in reflectance and transmittance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a focusing point control system of a conventional information reproducing apparatus, and FIG. 2 is a block diagram showing an embodiment of the focusing point control system of an optical information reproducing apparatus of the present invention. 6...Photoelectric converter, 7...Balance adjustment means, 8...Differential amplification means, 9...
Offset adjustment means, 10...Gain adjustment means, 11...Light spot moving means, 20...
... Sub-differential amplification means, 22 ... Recording signal component detection means, 23 ... Changeover switch. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (2)

[Claims] (1) A record carrier having an information track written with a recording signal modulated so that the DC component does not change, a light source that generates a luminous flux, and an optical convergence means that connects an extremely small light spot to the information track; Reading a recording signal from changes in reflected light or transmitted light from the information track, and outputting at least one pair of detection signals that differentially change depending on a relative positional error between the information track and the light spot. recording signal reading means; differential amplification means for differentially amplifying the pair of detection signals and outputting an error signal; and light spot movement for moving the light spot so as to minimize the relative position error based on the error signal. recording signal component detection means for detecting the recording signal component of the error signal; and the information reading means, the differential amplification means, and the optical spot moving means according to the output of the recording signal component detection means. 1. An optical information reproducing device comprising: bias adjustment means for adjusting a DC bias voltage of a position control means comprising: (2) The differential amplification means includes a balance adjustment means for changing the gain for one of the pair of detection signals relative to the gain for the other signal, and is further connected in parallel with the differential amplification means to The sub-differential amplification means for differentially amplifying the pair of detection signals and outputting a sub-error signal, and a changeover switch for inputting either the error signal or the above-mentioned sub-error signal to the optical spot moving means, When the changeover switch is closed on the side where the error signal is input to the optical spot moving means, the recording signal reading means, the sub-differential amplifying means, and the optical spot moving means are arranged so that the relative position error is minimized. The DC bias of the sub-position control means consisting of the above is adjusted, and in this state, the above-mentioned balance adjustment means is adjusted according to the output of the recording signal component detection means, and the above-mentioned The optical information reproducing apparatus according to claim 1, characterized in that the changeover switch is configured to close.