JPH0498626A - Optical pickup device - Google Patents

Abstract

PURPOSE:To suitably control the quantity of light by providing a photodetector arranged in an optical path from a deflecting prism to an objective lens so as to photodetect the light flux, and a control means to control the driving current of a semiconductor laser element based on the photodetection signal of this photodetector. CONSTITUTION:A deviation signal ER corresponding to deviation between a reference value VR and a photodetection signal SR is outputted from a differential amplifier 11 and applied to a semiconductor laser element driving circuit 13 to control the driving current of a semiconductor laser element 1. The circuit 13 controls the magnitude of a driving current ID impressed to the element 1 in a direction where the deviation signal ER is zero. When the quantity of light made incident to an objective lens 5 is lowered by sticking dirt onto optical parts, the quantity of light made incident to a photodetector 7 is lowered as well and therefore, a signal SR is lowered. Thus, the value of the signal ER outputted from the amplifier 11 becomes a value corresponding to the reduction in the quality of light made incident to the lens 5, and the circuit 13 changes the driving current ID so that the quantity of light made incident to the lens 5 can be coincident to a reference value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical pickup device that can control the output level of a semiconductor laser element to a predetermined value.

[Prior art] For example, in optical disk devices, magneto-optical disk devices, etc.
In an optical pickup device for recording/reproducing data on a storage medium, the amount of light from a semiconductor laser element used as a light source is controlled to a level necessary for recording and reproducing data.

Conventionally, the amount of light output from the semiconductor laser element has been determined using a light reception signal from a monitoring light receiving element housed in the envelope of the semiconductor laser element.

By the way, 1. For example, if dust or dirt enters the inside of an optical pickup device and adheres to the surface of the internal optical components, the transmittance and reflectance will decrease, and as a result, the intensity of light irradiated to the storage medium will decrease. As a result, data recording becomes incomplete, the S/N ratio of the reproduced signal decreases, and the reproduced data contains data errors.

An example of a method for solving this problem is disclosed in Japanese Patent Laid-Open No. 55-8006. In this conventional device, a prism is used to separate a part of the light beam guided from the semiconductor laser element onto the storage medium, and the separated light beam is received to determine whether the optical system is dirty.

[Problems to be Solved by the Invention] However, such conventional devices have the following disadvantages.

That is, since the prism that separates a part of the light beam is placed in front of the galvano mirror that guides the light beam that has passed through the prism to the objective lens, it is impossible to deal with the situation when the galvano mirror becomes dirty. This has caused the inconvenience that it is not possible to appropriately control the amount of light from the semiconductor laser element.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup device that can eliminate the disadvantages of the conventional device and appropriately control the light lf of a semiconductor laser element.

[Means for Solving the Problems] The present invention includes a light receiving element disposed in an optical path from a deflection prism to an objective lens to receive the light beam, and a driving of a semiconductor laser element based on a light reception signal of the light receiving element. It is equipped with a control means for controlling the current.

Also, a first light receiving element disposed in the optical path from the deflection prism to the objective lens and receiving the light beam, and a second light receiving element receiving a part of the signal light output from the semiconductor laser element. a differential amplifier that calculates the difference between the light receiving signal output from the first light receiving element and the light receiving element output from the second light receiving element; a comparator that compares the output of the differential amplifier with a predetermined value; selection means for selecting either the light reception signal of the first light reception element or the light reception signal of the second light reception element according to the output signal of the comparator; and a semiconductor laser based on the light reception signal selected by the selection means. The device is equipped with a control means for controlling the driving current of the element.

and a light receiving element that is disposed in the optical path from the deflection prism to the objective lens and receives the light beam.

An initial value setting means for outputting the initial value of the light reception signal of the light receiving element, and a reference value calculation for calculating a reference value of the light reception signal of the light receiving element based on the deviation between the light reception signal of the light receiving element and the set value of the initial value setting means. and a control means for controlling the drive current of the semiconductor laser element based on the deviation between the reference value calculated by the reference value calculation means and the light reception signal of the light reception element.

[Operation] Therefore, since the light receiving element detects the light flux output from the semiconductor laser element just before it enters the objective lens, the light flux irradiated onto the storage medium can be appropriately detected, and the light intensity of the semiconductor laser element can be adjusted. can be controlled appropriately.

In addition, in an optical pickup device equipped with a separating optical system, the light receiving signal of the light receiving element for detecting the light flux provided on the side of the fixed optical system and the light receiving signal of the light receiving element for detecting the light flux provided on the side of the separating optical system can be detected. Since the detection signal used to control the light amount of the semiconductor laser device is selected based on the deviation, even if a foreign object enters between the fixed optical system and the separation optical system, the detection signal used to control the light amount of the semiconductor laser device can be properly detected. Light amount control can be performed.

Further, since the reference value used for controlling the light amount is set in accordance with the variation in the light amount of the optical system, the light amount of the semiconductor laser element can be controlled with higher accuracy.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an optical system of an optical pickup device according to an embodiment of the present invention. This optical pickup device is
The optical system is housed in one housing.

In the figure, the light beam output from the semiconductor laser device 1 is converted into parallel light by the collimating lens 2, and then enters the beam splitter 3, passes through its surface 3a, is guided to the deflection prism 4, and is deflected. Most of the light is reflected by the prism 4 and guided to the objective lens 5, where it is focused and irradiated onto the storage medium 6. Also,
The light beam passing through the deflection prism 4 is received by the light receiving element 7.

The reflected light from the storage medium 6 is converted into substantially parallel light by the objective lens 5, reflected off the deflection prism 4, guided to the beam splitter 3, reflected off the surface 3b of the beam splitter 3, and then passed through the condenser lens 8. The light is focused and received by the light receiving element 9.

Further, the objective lens 5 is provided with an objective lens moving mechanism 5a that moves the objective lens 5 in the focusing direction and the tracking direction.

Then, based on the light reception signal of the light receiving element 9, a focusing error signal, a tracking error signal of the objective lens 5,
Then, a reproduced signal is obtained. Further, based on the focusing error signal and the tracking error signal, the focusing servo control means and the tracking servo control means control the objective lens moving mechanism 5a, and
performs positioning control of the focused light beam.

FIG. 2 shows an example of a light amount control system for the semiconductor laser device 1. As shown in FIG. Note that this figure shows the mode at the time of data reproduction.

In the figure, the light reception signal SR of the light receiving element 7 is
0 to the positive input terminal of the differential amplifier 11.

The negative input terminal of the differential amplifier 11 is connected to the light receiving element 7 when the optical surface of the optical components of the optical pickup device is clean and the output light amount of the semiconductor laser element 1 is at the reference value. A reference value VR corresponding to the magnitude of the obtained light reception signal is added by a reference value setter 12.

As a result, the differential amplifier 11 outputs a deviation signal ER corresponding to the deviation between the reference value VR and the light reception signal SR. It has been added to 13.

The semiconductor laser element drive circuit 13 drives the semiconductor laser element 1
The magnitude of the drive current ID applied to the semiconductor laser element 1 is controlled so that the deviation signal ER becomes zero.

Therefore, if dirt adheres to the optical components of the optical pickup device and the amount of light incident on the objective lens 5 decreases, the amount of light incident on the light receiving element 7 will also decrease with the decrease in the amount of light. The light reception signal S output from 7
R decreases.

As a result, the deviation signal E output from the differential amplifier 11
The value of R becomes a value corresponding to a decrease in the amount of light incident on the objective lens 5, so that the semiconductor laser element active circuit 13 adjusts the drive current so that the amount of light incident on the objective lens 5 matches the reference value. Change ID.

As a result, the output light amount of the semiconductor laser element 1 is controlled so that the amount of light incident on the objective lens 5 becomes a predetermined value, and as a result, the amount of light incident on the objective lens 5 is controlled to a predetermined value. .

By the way, when dirt adheres to the reflective surface of the deflection prism 4, the amount of reflected light and the transmitted light do not match, so the amount of light incident on the light receiving element 7 and the amount of light incident on the objective lens 5 do not match.

That is, as shown in FIG. 3(a), the deflection prism 4
When dust G is attached to the reflective surface of , the transmitted light is
This is the part of the incident light flux that is not blocked by the dust G.

On the other hand, as shown in FIG. 2B, the reflected light beam becomes a part that is not blocked by the dust G when reflected, of the part that is not blocked by the dust G when it is incident.

Therefore, the amount of reflected light is smaller than the amount of transmitted light, and for example, the ratio of the amount of reflected light to transmitted light is 2:5.

FIG. 4 shows a light amount control system according to another embodiment of the present invention that can eliminate such a difference in light amount between reflected light and transmitted light.

In the figure, the light reception signal SR of the light receiving element 7 is
0 to the analog/digital converter 15;
This analog/digital converter 15 converts it into a corresponding digital light reception signal DR, and the light amount data holding circuit 1
6 and comparator 17.

The light amount data holding circuit 16 samples and stores the digital light reception signal DR, for example, at the first timing when the optical pickup device accesses a newly installed storage medium, and the stored data DRa is used for error detection. It is applied to one input end of circuit 18.

The initial value setting circuit 19 stores initial value data RFa corresponding to the amount of light received by the light receiving element 7 in an initial state, and the initial value data RFa is added to the error detection circuit 18 as reference data. .

The error detection circuit 18 detects the error between the initial value data RFa and the stored data DRa, and the test result is as follows.
It is added to the light amount reference value setting circuit 20 as an error signal ERa.

The light amount reference value setting circuit 20 determines an error in the amount of light incident on the objective lens 5 based on the error signal ERa, and also sets a light amount reference value RF necessary to eliminate the error.
The light quantity reference value RFb is applied to the reference value input terminal of the comparator 17. For example, as described above, when the light amount ratio of reflected light and transmitted light is 2=5, the light amount reference value setting circuit 20 sets the error signal ERa to 572.
The multiplied value is determined as a light amount error.

The comparator 17 outputs the digital light reception signal DR and the light amount reference value RF.
b, and the comparison result is added to the digital/analog converter 21 as control data CDa.

The digital/analog converter 21 converts the control data CDa into a corresponding analog control signal CAa, and the analog control signal CAa is applied to the current control circuit 22.

The current control circuit 22 supplies a drive current I to the semiconductor laser element 1.
D is applied, and the magnitude of the drive current ID is controlled based on the analog control signal CAa.

In this way, in this embodiment, the light intensity difference from the initial value is determined based on the light reception signal SR of the light receiving element 7, and the drive current ID to be applied to the semiconductor laser element 1 is determined based on the determination result. Since it is controlled, objective lens 5
When the amount of incident light changes over time, the drive current ID applied to the semiconductor laser element 1 is changed so as to eliminate the change over time.
is controlled, the amount of light incident on the objective lens 5 can always be set to an appropriate value.

FIG. 5 shows that the deflection prism 4 and objective lens 5 of the optical pickup device are housed in a separate housing separate from other optical components, and only this separated housing is moved in the radial direction of the storage medium. This enables high-speed data access. In this figure, the same or corresponding parts as in FIG. 1 are given the same reference numerals.

In the figure, a semiconductor laser element 1, a collimating lens 2, a beam splinter 3. The light receiving element 9 and the light receiving element 25 that receives the light beam reflected from the surface 3a of the beam splitter 3 are housed in a fixed housing CAI, and the deflecting prism 4, the objective lens 5, the objective lens moving mechanism 5a, and the The light receiving element 7 is housed in a housing CA2.

In addition, in order to maintain the optical path connecting the fixed case CAL and the separated case CA2, the fixed case CAL and the separate case CA2 are connected to each other.
Cover glasses 26 and 27 are fitted into the openings formed in each of the openings 2 to maintain airtightness of the fixed casing CAI and the separated casing CA2.

FIG. 6 shows an example of a light amount control system applied to the optical pickup device of FIG. 5. In addition, in the same figure, the second
Identical and corresponding parts to those in the figures are given the same reference numerals.

In the figure, the light reception signal SR of the light receiving element 7 is
The light reception signal SS of the light receiving element 25 is applied to the positive side input terminal of the differential amplifier 32 and one switching input terminal 33a of the switch 33 via the amplifier 34, side input terminal and the other switching input terminal 33b of the switching device 33.

The differential amplifier 32 calculates the difference between the light-receiving signal SR and the light-receiving signal SS, and the result of the calculation is applied to the comparison signal input terminal of the comparator 35 as a difference signal EE.

The reference value setter 36 stores a reference value REe of the difference signal EE, and the reference value REe is applied to the reference signal input terminal of the comparator 35.

The comparator 35 compares the difference signal EE with the reference value REe, and when the difference signal EE becomes larger than the reference value REe, raises its output signal BE to a logic H level. 33 and output to an external device (for example, a control device) as an error signal.

The switch 33 selects the received light signal SR applied to the switching input terminal 33a when the signal BE applied from the comparator 35 is at the logic L level, and when the signal BE is at the logic H level. , the light reception signal ss applied to the switching input terminal 33b is selected, and the selection specific power is:
With the above configuration, the amount of light received by the light receiving element 7 and the amount of light received by the light receiving element 25 are almost equal, so that the amount of light received by the light receiving element 25 is approximately equal to the amount of light received by the light receiving element 25. The difference signal EE becomes smaller than the reference value REe.

As a result, the signal BE output from the comparator 35 becomes a logic L level, and the switch 33 selects the light reception signal SR and applies it to the differential amplifier 11.

Therefore, the drive current In applied to the semiconductor laser element 1 is controlled according to the amount of light received by the light receiving element 7, and the amount of light incident on the objective lens 5 is controlled to a predetermined value.

Here, for example, if a foreign object or the like enters the optical path from the fixed housing CAL to the separated housing CA2 and the amount of light received by the separated housing CA2 is significantly reduced, the amount of light received by the light receiving element 7 is significantly reduced. As a result, the difference signal EE output from the differential amplifier 32 increases significantly.

As a result, the output signal BE of the comparator 35 rises to the logic H level, which causes the switch 33 to select the received light signal SS applied to the switching input terminal 33b and apply it to the differential amplifier 11, while also The device is notified of an abnormality in the optical system.

As a result, instead of the rapidly changing light reception signal SR,
Since the light reception signal SR is applied to the differential tank S unit 11, it is possible to avoid a situation where the drive current ID applied to the semiconductor laser device 1 by the semiconductor laser device active circuit 13 increases significantly, and the semiconductor laser device 1 is not damaged. It is possible to prevent such accidents.

By the way, in the above embodiment, the reflected light from the deflection prism is guided to the objective lens, but the present invention can be similarly applied to an optical pickup device that guides the transmitted light from the deflection prism to the objective lens. can.

[Effects of the Invention] As explained above, according to the present invention, the light beam output from the semiconductor laser element is detected by the light receiving element immediately before it is incident on the objective lens, so that the light beam irradiated onto the storage medium is detected. The light flux can be detected appropriately, and the light amount of the semiconductor laser element can be appropriately adjusted to mi#.

In addition, in an optical pickup device equipped with a separating optical system, the light receiving signal of the light receiving element for detecting the light flux provided on the side of the fixed optical system and the light receiving signal of the light receiving element for detecting the light flux provided on the side of the separating optical system can be detected. Based on deviation.

Since the pressure detection signal used to control the light intensity of the semiconductor laser element is selected, the light intensity of the semiconductor laser element can be appropriately controlled even in a situation where a foreign object enters between the fixed optical system and the separation optical system. be able to.

Further, since the reference value used for controlling the light amount is set in accordance with the variation in the light amount of the optical system, it is possible to control the light amount of the semiconductor laser element with higher accuracy.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an optical pickup device according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a light amount control system of the device in FIG. 1, and FIG. 3(a). (b) is a schematic diagram for explaining the difference in the amount of light between reflected light and transmitted light, FIG. 4 is a block diagram showing another example of the light amount control system of the device shown in FIG. 1, and FIG. A schematic configuration diagram showing an optical pickup device according to another embodiment, and FIG. 6 is a block diagram showing an example of a light amount control system of the device in FIG. 5. 7.25... Light receiving element, 11.32... Differential amplifier, 12... Reference value setter, 13... Semiconductor laser element drive circuit, 15... Analog/digital converter, 1
6... Light amount data holding circuit, 17.32... Comparator, 18... Error detection circuit, 19... Initial value setting circuit, 20... Light amount reference value setting circuit. 21...Digital/analog converter, 22...Current control circuit, 33...Switcher.

Claims (3)

[Claims] (1) In an optical pickup device that aligns the optical axis of signal light output from a semiconductor laser element with the optical axis of an objective lens via a deflection prism, the light flux is arranged in the optical path from the deflection prism to the objective lens. 1. An optical pickup device comprising: a light-receiving element that receives light; and a control means that controls a drive current of a semiconductor laser element based on a light-receiving signal of the light-receiving element. (2) The optical axis of the signal light output from the semiconductor laser element is aligned with the optical axis of the objective lens via the deflection prism, and the deflection prism and objective lens are separated from other optical systems in the radial direction of the storage medium. In an optical pickup device that is moved, a first light receiving element is disposed in the optical path from the deflection prism to the objective lens and receives the light beam, and a first light receiving element receives a part of the signal light output from the semiconductor laser element. a second light-receiving element; a differential amplifier that calculates the difference between the light-receiving signal output from the first light-receiving element and the light-receiving element output from the second light-receiving element; a comparator for comparing the value, and a light receiving signal of the first light receiving element or a second light receiving element depending on the output signal of this comparator.
An optical pickup comprising: a selection means for selecting one of the light reception signals of the light reception element; and a control means for controlling a driving current of a semiconductor laser element based on the light reception signal selected by the selection means. Device. (3) In an optical pickup device that aligns the optical axis of signal light output from a semiconductor laser element with the optical axis of an objective lens via a deflection prism, the light flux is arranged in the optical path from the deflection prism to the objective lens. a light-receiving element that receives light; an initial value setting means that outputs an initial value of a light-receiving signal of the light-receiving element; A reference value calculation means for calculating a reference value of a signal, and a control means for controlling a driving current of a semiconductor laser element based on a deviation between a reference value calculated by the reference value calculation means and a light reception signal of the light receiving element. An optical pickup device featuring: