JPS63306540A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To always enable a proper offset elimination even if a quantity of stray light is varied in accordance with a variation of a quantity of light of a light source by utilizing an output signal of a stray light detecting means for outputting a signal in accordance with the stray light, for an offset adjusting means. CONSTITUTION:When a light source 1 is emitted, a photoelectric current in response to its quantity of light, i.e., an output signal in proportion of its stray light is generated by a photodiode 20, and this is converted into voltage by a current/voltage conversion circuit 21, and voltages at fixed terminals of volumes 15 and 16 connected with the output of the conversion circuit 21 are increased or decreased in accordance with the quantity of light of the light source 1 so as to make their offset adjusting amts. variable. On the other hand, a photoelectric current due to the stray light, outputted from a bisect photodetector 11 is inputted to current/voltage conversion circuit 13 and 14 respectively, while at the same time, the offset adjusting voltages by resistors 17 and 18 connected with the volumes 15 and 16 are also inputted, so that a portion of the photoelectric current due to the stray light is deducted. By this method, the proper offset elimination can always carried out, even if the quantity of stray light is varied, because of the offset adjusting voltages being simultaneously varied.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a device for recording or reproducing information on, for example, an optical disc that can be optically recorded or reproduced, and particularly relates to an adjustment of an offset included in a control signal thereof. This invention relates to a device with an improved circuit.

[Conventional technology]

For example, 1μm x 1μ on an optically recordable and reproducible disc.
To record minute bits of m or less, or to reproduce the bits already recorded on the disk, a focus servo is used to always focus the light source on the disk, or a focus servo is used to always focus the light source on the disk, or a light beam is always placed on the recorded bit string. A tracking servo is essential for beam irradiation.

Figure 3 shows, for example, the focus servo system that was presented at the 11th Optical Symposium (Ban 10 of the Society of Applied Physics '86.73).
1 is a diagram showing an example of a conventional optical recording/reproducing device equipped with a tracking servo mechanism.

In Figure 3, (1) is a light source such as a semiconductor laser, (2 is
) is a polarizing beam splitter used as an optical element to separate the light beams, (3) is a collimator lens that converts the light beam emitted from the polarizing beam splitter (2) into parallel light, and (4) is the polarizing beam splitter that separates the light beams. (5) is a recording medium, (6) is an objective lens for irradiating a light beam onto the recording medium (5), and a lens drive mechanism for performing focus servo and tracking servo. Equipped with: (Illustration omitted) (7) is the recording medium (
5) a wedge prism that collects the reflected light for focus servo; (8) a concave lens for adjusting the focusing optical path length of the light beam from this wedge prism (7);
(9) is the half prism percentage to split the light beam into two
(10) s (1 is a photodetector that detects a focus error signal and a tracking error signal, respectively.

The state of the light beam on the focus detector (10) and tracking detector (11) changes as shown in FIG. 4 due to surface deflection or eccentricity of the recording medium (1).

This will be explained using tracking as an example. (11) is a photodetector composed of two divided photodiodes, (12
) indicates a light beam spot. (a) shows a state shifted to the left in the figure from the track center, (b) shows an on-track state, and (0) shows a state shifted to the right in the figure from the track center. When the light beam deviates from the track center in this way, the light distribution on the photodetector changes accordingly. Therefore, a tracking error signal can be obtained by extracting the differential signals of the two photodiodes. Regarding focus, a focus error signal can be obtained using the same principle.

However, the optical components shown in Fig. 6 have a considerable amount of unnecessary reflection, which enters the photodetector (10) # (11) separately from the reflected light from the recording medium (5). It's coming. This light is called stray light, and the resulting deviation of the photodetector output is called an offset due to stray light. Further, stray light increases or decreases depending on the increase or decrease in the number of light sources. When this is superimposed on the normal error signal, the servo is applied in a state that deviates from the normal basic point, just focus, and on-track position.

FIG. 5 shows an example of an offset adjustment circuit in a conventional tracking error detection means disclosed in Japanese Utility Model Application No. 59-145726. (1 is a photodiode divided into two by a photodetector, (15) and (14) are current-voltage conversion circuits that convert the photocurrent of the photodetector (11) into voltage,
(15) is a volume for offset adjustment, (19) is a differential amplifier for obtaining a differential signal from the output of the current-voltage conversion circuit (137e (14)), and resistor R1#"l
11M eRa and OF 7 amplifier (OF 13 I
: Consists of. Also, (17) is the volume (15)
This is a resistor for supplying the voltage from the differential amplifier (19) to the differential amplifier (19).

Next, the operation will be explained. When reflected light enters the photodetector (11), a photocurrent is generated in the photodetector (11), which is converted into a voltage by the current-voltage conversion circuit (14).
Differential amplifier (19) (: Obtains tracking error signal by inputting.

If stray light enters this, an extra photocurrent is generated in the photodetector (11), resulting in a signal in which a certain value is superimposed on the original tracking error signal.

A so-called offset occurs. This offset is canceled as follows.

Since the voltage set by the offset adjustment volume (15) is applied to the differential amplifier (19) through the resistor (17), the offset can be removed by adjusting the volume (15).

[Problem that the invention seeks to solve]

Since the offset adjustment circuit in a conventional optical recording/reproducing device is configured as described above, the offset due to stray light can be removed for a certain amount of light from the light source, but in an optical recording/reproducing device that performs recording/reproducing, Since it is necessary to vary the amount of light from the light source, and the stray light also changes accordingly, there is a problem in that offset due to stray light can only be removed at a certain amount of light from the light source.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an optical recording/reproducing device having an offset adjustment circuit that can eliminate offset caused by stray light even if the amount of light from a light source is changed.

[Means for solving problems]

The optical recording/reproducing apparatus according to the present invention is provided with a stray light detection means that outputs a signal corresponding to stray light, and is configured so that the output signal of the stray light detection means is used in the offset adjustment means.

[For production]

The optical recording/reproducing apparatus according to the present invention uses the output signal of the stray light detection means for the offset adjustment means, thereby achieving the following:
For example, when the amount of light from a light source increases, the amount of stray light also increases.
Even if the amount of stray light increases, offset adjustment is performed accordingly to eliminate offset due to stray light.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. Note that the same or equivalent parts as in the above-mentioned prior art are given the same reference numerals, and the explanation thereof will be omitted.

In Figure 1, (1) is a light source such as a semiconductor laser, (20
) is a photodiode that detects the light intensity of this light source (1), (21) is a current-voltage conversion circuit that converts the photocurrent of this photodiode (20) into voltage, and (22) is a photodiode that detects the light intensity of the light source (1). Reference voltage input terminal for setting%
(25) is a drive circuit that compares the levels of the current-voltage conversion circuit (2) and the reference voltage input terminal (22) and flows a current to the light source (1). The photodiode (20) and the current-voltage conversion circuit (21) constitute a stray light detection means (24).(15) , (16) are volumes, the fixed terminal 10,000 is grounded, and the other is connected to the output of the current-voltage conversion circuit Is (21). (17), (18) are the volumes (15), (16) This is a resistor for supplying the voltage set by the current voltage converter circuit (1 ri, (14 month = 14 months). The above volume (15), (16 J, resistance (1 υ, (18 month two off sellers) 1M adjustment means It consists of

Next, the operation will be explained. When the light source (light source) emits light, the photodiode (20) passes light according to the amount of light, that is, generates an output signal according to the stray light. (15) and (16).

The voltage at the fixed terminal of the volume (15) s (16 J) connected to the output of the current-voltage conversion circuit (21) increases or decreases depending on the light source scene to vary the offset adjustment amount. Accompanying two-part photodetector (
Figure 2 shows the changes in the amount of stray light shining on two people in November. 10,000 photodetectors (11!L) and the other (11b
). Stray light is generated due to unnecessary reflection by optical components, etc., and depends on the amount of light from the light source, and tends to increase as the amount of light increases.

The reason why the slopes of the two straight lines are different is that the amount of stray light incident on the two divided photodetectors (11) is different.

The photocurrent due to stray light appearing at the output of the two-divided photodetector (11) is input to the current-voltage conversion circuit (1a) (14), but at the same time, the photocurrent is input to the volume (15), (16).
) The offset adjustment voltage is also input through the resistors (17) and (18) connected to the resistors (17) and #(18), and the photocurrent due to stray light is subtracted. Even if the amount of light from the light source changes and the amount of stray light changes, the offset adjustment voltage also changes at the same time, so it is possible to always perform appropriate offset removal. In addition, the volume (1
5) e Setting (16) is performed to adjust the amount of correction for the inclination of the amount of stray light shown in FIG. 2. Once the initial setting is made, there is no need to make any further changes.

In the first embodiment, a photodiode (2o) and a current-voltage conversion circuit (21) of a light source sight control system were used as the stray light detection means (24), but a light source sight control system was also provided as shown in FIG. The device may be configured using the voltage of the reference voltage input terminal (22) for setting the light amount of the light source. The operation of the light amount control system in this case will be described. When the light source (1) emits light, the photodiode (20) generates a photocurrent corresponding to the amount of light. In the current-voltage conversion circuit (21), the photocurrent is extracted as a voltage and fed back to the positive input of the drive circuit (2).In this drive circuit (23), the voltage and current at the reference voltage input terminal (22) are Compare the output voltage of the voltage conversion circuit (21) and drive the light source (1) with the output signal,
Performs feedback control of the light amount control system. That is,
The amount of light from the light source is controlled by the voltage set at the reference voltage input terminal (22). Therefore, the reference voltage input terminal (2
By using the voltage 2) as an offset adjustment voltage, offset adjustment is performed according to the amount of light from the light source, that is, stray light.

It goes without saying that the Oki photodiode (20 Tama) and other photoelectric conversion elements C may be replaced. It goes without saying that various other modifications and changes are possible.

〔Effect of the invention〕

As described above, according to the present invention, the stray light detection means for outputting a signal corresponding to stray light is provided, and the output signal of this stray light detection means is configured to be used in the offset adjustment means, so that the amount of stray light changes due to changes in the amount of light from the light source. Even if the offset is removed, the offset can always be removed appropriately.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an offset adjustment circuit which is a main part of an optical recording/reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing characteristic factors showing the relationship between the amount of light from the light source and the amount of stray light. J.
FIG. 4 is an explanatory diagram of error detection in the tracking servo and focus servo, and the fifth cause is a diagram showing the offset adjustment circuit of the conventional device. (1) is a light source, (10) e (11) is a photodetector, (
24) is a stray light detection means s; (25) is an offset adjustment means. Note that the same reference numerals in the figures indicate the same or equivalent parts. 1111 Figure 2-11t, red circle l → Figure 3, Figure 4, 5WJ

Claims (2)

[Claims] (1) means for irradiating light emitted from a light source onto a recording medium; a photodetector for receiving reflected light from the recording medium and outputting a signal according to information contained in the reflected light; In an optical recording/reproducing apparatus, the optical recording/reproducing apparatus is provided with a means for adjusting an offset due to stray light contained in an output signal, and a stray light detecting means for outputting a signal according to stray light is provided, and the output signal of the stray light detecting means is sent to the offset adjusting means. An optical recording/reproducing device characterized in that it is configured to be used. (2) The optical recording and reproducing apparatus according to claim 1, wherein means for detecting the amount of light from a light source is used as the stray light detecting means.