JPH08255368A - Optical head - Google Patents

Abstract

PURPOSE: To sufficiently reduce return light quantity being a noise occurrence cause of a semiconductor laser by providing a light attenuator of a light energy attenuation means. CONSTITUTION: This optical head 3 is provided with a semiconductor laser oscillator 9 of a light generation means, the light attenuator 11f of the light energy attenuation means, a polarizing beam splitter prism 11b of a light splitting means and photodetectors 7, 8 of a light detection means. The semiconductor laser oscillator 9 outputs light for recording/reproducing information on/from an optical disk 1 with the energy so that a return light noise becomes nearly minimum. The light attenuator 11f attenuates the output energy of the light from the semiconductor laser oscillator 9 to the output required for recording/ reproducing the optical disk 1. The polarizing beam splitter prism 11b transmits through the light attenuated by the light attenuator 11f, and splits the reflected light of the light, and the photodetectors 7, 8 detect the split light. Thus, the return light quantity is reduced sufficiently, and the influence of a noise is reduced by attenuating a laser output to a level suitable for recording/ reproducing with the light attenuator 11f even when the output from the laser oscillator 9 is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for recording information on an optical disc as a recording medium and reproducing information recorded on the optical disc.

[0002]

2. Description of the Related Art An example of an optical disk device provided with an optical head for recording information on an optical disk and reproducing information recorded on the optical disk will be described. In the optical disk device, the optical disk is rotated and driven by a spindle motor, and a light beam (laser light) is applied to the optical disk from the objective lens of the optical head. By moving an optical head that radiates this light beam in the radial direction of the optical disc, the optical disc is scanned with the light beam.
By the scanning of the light beam, information is recorded on the optical disc, or the light beam reflected from the optical disc is received by the light receiving sensor of the optical head to reproduce the information.

By the way, an optical isolator composed of a polarization beam splitter prism and a quarter-wave plate is generally used for this optical head. This optical system called an optical isolator is used to prevent the laser light emitted from the semiconductor laser oscillator, which is the light source of the laser, from returning to the semiconductor laser oscillator and causing a resonance phenomenon in the semiconductor laser oscillator.

The polarization beam splitter prism that constitutes the optical isolator is a laser beam that enters the optical disk.
It is used for the purpose of separating the reflected light reflected from the optical disk. This polarizing beam splitter prism has 2
A polarizing film is applied to the inclined surface of each 45-degree right-angle prism, and they are bonded together to form a cube. By this polarizing film, the electric field component (P-polarized light) of the light wave parallel to the incident surface is passed, and the electric field component (S-polarized light) of the light wave perpendicular to the incident surface is reflected.

If the polarization direction of the linearly polarized light emitted from the semiconductor laser and the incident surface of the polarization beam splitter prism are made to coincide with each other, the linearly polarized light emitted from the semiconductor laser passes through almost 100% of the polarization beam splitter prism. (Actually, it is not 100% due to optical loss).

The linearly polarized light that has passed through the polarizing beam splitter prism becomes circularly polarized light after passing through the quarter-wave plate and enters the optical disk surface. The reflected light from the optical disk surface is
The circularly polarized light has the opposite rotation direction, passes through the quarter-wave plate again, and then becomes linearly polarized light orthogonal to the incident linearly polarized light (the optical axis of the quarter-wave plate is the light beam emitted from the semiconductor laser oscillator). Is inclined by 45 degrees from the polarization direction of, and the polarization direction of the light beam that has passed through this quarter wavelength plate twice is 9
It has rotated 0 degrees). When this linearly polarized light enters the polarizing beam splitter prism again, almost 100
% Reflected (actually 100 due to optical loss etc.)
%), And the total amount of light is incident on the light receiving sensor. That is, it is configured so that incident light does not return to the semiconductor laser.

[0007]

However, in reality, there are variations in the characteristics of components such as the semiconductor laser, the quarter-wave plate, and the polarization beam splitter, and incomplete (1/4 wavelength) when incorporated in the optical system. Misalignment of the optical axis of the plate, thickness error,
Due to the deviation of the incident angle of the light beam on the quarter-wave plate, the fluctuation of the wavelength of the light beam, etc., there is some amount of returning light (it is difficult to completely prevent the reflected laser light from returning to the semiconductor laser again).

Therefore, the reflected laser light reflected from the optical disk is returned to the semiconductor laser, causing a resonance phenomenon in the semiconductor laser and making the laser oscillation mode unstable (a cause of generation of semiconductor laser noise). When the oscillation mode of the laser becomes unstable, the laser light reflected from the optical disk and incident on the light receiving sensor is affected and unstablely fluctuates.

This fluctuation of the laser beam appears as noise when reproducing the information recorded on the optical disk, and there is a problem that the S / N (signal to noise ratio) is lowered. An object of the present invention is to provide an optical head capable of sufficiently reducing the influence of the amount of returning light which is a cause of noise generation of a semiconductor laser.

[0010]

The optical head of the present invention comprises:
Light generating means for outputting light for recording information on the optical recording medium or reproducing information recorded on the optical recording medium with energy at which return light noise is substantially minimized; Optical energy attenuating means for attenuating the energy of the emitted light to an output required for reproduction and recording of the optical recording medium; transmitting the light attenuated by the optical energy attenuating means, and separating the reflected light of the transmitted light And light detecting means for detecting the light separated by the light separating means.

[0011]

Since the optical head according to the present invention is provided with the optical energy attenuating means, even if the output of the laser that minimizes the amount of returned light is higher than the output suitable for reproduction / recording of the optical disk, the laser output is produced by the optical energy attenuating means. Play /
It can be used after being attenuated to a level suitable for recording. Therefore, the amount of returning light, which is a cause of noise of the semiconductor laser, can be sufficiently reduced, and the influence of noise in the optical disk device can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram and a block diagram illustrating the configuration of an optical disk device according to an embodiment of the present invention.

On the surface of the optical disk (optical recording medium) 1,
Recording tracks (grooves) are formed in a spiral shape or concentric circles. The optical disc 1 is rotated at a constant speed by a motor 2. The motor 2 is controlled by the motor control circuit 18.

The optical disk 1 is irradiated with a light beam from an optical head 3 provided below the optical disk 1.
This light beam optically reproduces information on the optical disc 1 or records information on the optical disc 1.

In addition to the recording film in which pits are formed, the optical disc 1 includes a recording film utilizing phase change or a multilayer recording film. There is also a magneto-optical disk capable of magneto-optically recording / reproducing information.

In the optical head 3, the objective lens 6 is held by a wire or a leaf spring (not shown). The objective lens 6 can be moved by the drive coil 5 in the focusing direction (optical axis direction of the lens) and by the drive coil 4 in the tracking direction (direction orthogonal to the optical axis of the lens).

The laser light generated by the semiconductor laser oscillator 9 driven by the laser control circuit 14 is
The optical disc 1 is irradiated with light through the collimator lens 11a, the optical attenuator 11f, the polarization beam splitter prism 11b, the quarter-wave plate 11e, and the objective lens 6. The collimator lens 11a is a lens for converting the divergent light emitted from the semiconductor laser oscillator 9 into parallel light. The optical attenuator 11f is particularly important in the present invention and attenuates the output of the laser light emitted from the semiconductor laser oscillator 9 (described in more detail later).

The reflected beam of the laser beam applied to the optical disk 1 again passes through the objective lens 6 and the quarter-wave plate 11e, is reflected by the polarization beam splitter prism 11b, and is converted into two light beams by the half prism 11c. To be separated.

One of the separated light beams is guided to the photodetector 7 via the focus detector 11d. The other separated light beam is guided to the photodetector 8 via the track detector 10.

The light beam generated from the semiconductor laser oscillator 9 is detected by the detector PD, and the detected signal is fed back to the laser control circuit 14. As a result, the output of the light beam generated from the semiconductor laser oscillator 9 is stabilized.

The detection signal from the photodetector 7 for focus detection is output to the differential amplifier OP2, the difference signal is obtained by the differential amplifier OP2, and the difference signal is supplied to the focusing control circuit 15. . The focusing control circuit 15 generates a focusing signal according to the difference signal. This focusing signal is given to the drive coil 5 via the amplifier 28. Therefore, the objective lens 6 is moved along the optical axis direction and maintained in the focusing state, and the minimum beam spot is formed on the optical disc 1.

A signal from the photodetector 8 for tracking detection is output to a differential amplifier OP1 via a high speed amplifier circuit 12 which will be described in detail later, and the differential signal is obtained by this differential amplifier OP1 and the difference signal is obtained. The signal is the tracking control circuit 16
Is supplied to. The tracking control circuit 16 generates a tracking signal according to the difference signal. This tracking signal is given to the drive coil 4 via the amplifier 27. Therefore, the orientation of the objective lens 6 is changed and the tracking state is maintained, and the tracking guide is tracked by the light beam.

Further, the tracking signal is given to the linear motor control circuit 17, the linear motor 41 is driven according to the drive signal from the linear motor control circuit 17, and the optical head 3 is moved in the radial direction of the optical disc 1. .

The focusing signal and the tracking signal are supplied to the A / D converter 21 and the bus 20 for the control related to the focusing control and the tracking control.
Is supplied to and processed by the CPU 23. In addition to the CPU 23, the bus 20 includes an operation panel 30, a memory 24, a D / A converter 22, and an interface 29.
Etc. are connected.

Further, the linear motor control circuit 17 corresponds not only to the tracking signal from the tracking control circuit 16 but also to an instruction from the operation panel 30. That is, the CPU 23 responds to the instruction from the operation panel 30.
And a voltage corresponding to the difference between the reference speed signal supplied via the D / A converter 22 and the current moving speed by the track counter signal is applied to the drive coil (conductor) in the linear motor 41, The optical head 3 is moved to a predetermined track.

As described above, the sum signal of the detection signals from the respective photodetecting cells of the photodetector 8 in the focusing state and the tracking state reflects the change in the reflectance from the pits (recording information) formed on the track. Has been done. This signal is supplied to the signal processing circuit 19, and this signal processing circuit 1
At 9, recorded information and address information (track number, sector number, etc.) are reproduced. The reproduced signal (reproduced information) reproduced by the signal processing circuit 19 is transferred to the interface circuit 29.
Is output to an information processing device (not shown) as an external device.

FIG. 2 is a circuit diagram for explaining the high speed amplifier circuit 12 of FIG. 1 in detail. In the movable part of the high-speed amplifier circuit 12, the output side of the high-speed operational amplifier 50 is connected to the inverting input side via the resistor R4 to form an amplification stage. Two photodiodes D1 constituting the photodetector 8
And D2 are commonly connected on the power supply Vcc side, and the inverting input side of the high speed operational amplifier 50 is connected to the commonly connected connection point 56. The connection point 56 is connected to the resistor R1.
Is connected to the power source Vcc via. The power supply Vcc is
It is connected to the non-inverting input side of the high speed operational amplifier 50 via the resistor R2.

In the fixed portion outside the optical head 3, the non-inverting input side of the high speed operational amplifier 50 is connected to the non-inverting input sides of the servo amplifiers 52 and 54 via the resistor R3. The anodes of the photodiodes D1 and D2 of the photodetector 8 are connected to the inverting input sides of the servo amplifiers 52 and 54. The output side of each of the servo amplifiers 52 and 54 is connected to the inverting input side via resistors R5 and R6. The inverting input sides of the servo amplifiers 52 and 54 are grounded via capacitors C1 and C2, respectively. Further, on the non-inverting input side of the servo amplifier 54,
The reference power supply Vref is connected.

In the circuit shown in FIG. 2, when a light beam is detected by the photodiodes D1 and D2 of the photodetector 8, the detected light beam is photoelectrically converted and a current is generated in each of the photodiodes D1 and D2. . The current signals generated in the photodiodes D1 and D2 are supplied to the servo amplifiers 52 and 54 from their anodes and amplified. The current signals amplified by the servo amplifiers 52 and 54 are voltage signals V1 (V1 = −I1 × R5) and V, respectively.
2 (V2 = -I2 × R6) converted to servo output V
1 and V2 are output to the differential amplifier OP1 in FIG.
A push-pull signal corresponding to the difference between the outputted servo outputs V1 and V2 is obtained from the differential amplifier OP1, and this push-pull signal is supplied to the tracking control circuit 16.

In the photodiodes D1 and D2 of the photodetector 8, the same current as the current supplied to the respective anode sides flows out from the cathode side. Therefore, the current (I1 + I2) flows through the common connection point 56. This current (I1 + I2) flows into the resistor R4, is converted into a voltage signal, and is voltage-amplified by the high speed operational amplifier 50 to generate a voltage signal V3 (V3 = (I1 + I2) R.
4) is output. This voltage signal V3 corresponds to an addition signal of the detection signals from the photodiodes D1 and D2 of the photodetector 8, and is therefore supplied to the signal processing circuit 19 as an information reproduction signal.

In the above circuit, the current (I1 + I2) as the detection signal from the photodiodes D1 and D2 of the photodetector 8 is usually on the order of several μA.
Since the minute current as the detection signal is converted into the voltage signal by the high speed operational amplifier 50 in the vicinity of the photodiodes D1 and D2 of the photodetector 8, it is possible to prevent noise from being mixed in the reproduction signal in advance.

Further, an operational amplifier 50 for amplifying the reproduction signal
Since only this and its peripheral circuit portion are mounted on a carriage (not shown) that holds the optical head 3, an increase in the weight of the carriage can be minimized.
That is, the weight of the carriage can be sufficiently reduced as compared with the case where the amplifiers for the reproduction signal, the focusing signal, and the tracking signal are mounted on the carriage, and high-speed access is possible. Since the band required for the servo signal is several 100 KHz at most, the band of the servo amplifiers 52 and 54 is limited by the capacitors C1 and C2. In addition, the servo amplifiers 52 and 54 and their peripheral circuit components are provided on the fixed side outside the carriage.

The bias resistor R1 is a photodiode D.
It has a function as a bias resistance of 1 and D2. In the photodiodes D1 and D2, in order to obtain a high quality signal, the cathode potential is set to about 3 rather than the anode potential.
It is required to be higher than V. Therefore, the photodiodes D1 and D2 are reverse-biased by being pulled up to the voltage Vcc via the resistor R1. Further, the resistors R1, R2, R3, and R4 allow the high-speed operational amplifier 50 to function as a differential input amplifier.

The output V3 of the high speed operational amplifier 50 is V3 = Vref + {R3 / (R2 + R3)}  {(R1
+ R4) ・ (Vcc-Vref) / R1}-(Vcc-
Vref) .R4 / R1-R4 {-(I1 + I2)}.

Now, assuming that R1 = R2 and R3 = R4,
Since the second term and the third term of the above equation are canceled out, V3 = Vref−R4 {− (I1 + I2)} = Vref + R4 (I1 + I2), and there is no term dependent on the current voltage, and the influence of power supply voltage fluctuation I know that I will not receive it.

Since the output V3 is based on the voltage Vref, the output voltage reference can be set to any voltage regardless of the reverse bias potential of the photodiodes D1 and D2. The reverse bias voltage is
Since it is set by Vref + R3 (Vcc-Vref),
Since it is possible to freely set the ratio of the resistors R2 and R3, it is possible to prevent the reverse bias from affecting the output voltage of the high speed operational amplifier 50 and its current / voltage ratio.

As described above, the signal obtained from the anode side of the detection signal from the photodetector 8 is used for servo, and the signal obtained from the cathode side is used for data reproduction. Therefore, the band of the servo signal can be widened, and high-speed, for example, track count access of several 100 KHz can be performed.

Further, a high speed amplifier stage (5 for amplifying signals obtained from the cathode side of the photodiodes D1 and D2).
By mounting only 0) on the optical head, it is possible to realize a lightweight optical head while obtaining a reproduction signal of high quality. Further, a high speed amplification stage (50) for amplifying a signal obtained from the cathode side of the photodiodes D1 and D2.
Is constituted by the differential amplifier OP1, the reverse bias for the photodiodes D1 and D2 of the photodetector 8 and the output value of the high speed operational amplifier 50 can be freely set independently, and the output of the operational amplifier 50 can be set to the power supply voltage Vcc.
Can be unaffected by.

FIG. 3 is a graph illustrating the optical output-return optical noise characteristic of a general semiconductor laser oscillator. The vertical axis of this graph shows the return light noise (%), and the horizontal axis shows the optical output (mW) of the semiconductor laser oscillator. Hereinafter, the graph A and the graph B showing the optical output-return light noise characteristic will be described.

Graph A is a characteristic graph of a semiconductor laser oscillator in which the amount of returned light is minimum (A1) when the optical output is 2.6 mW. Graph B shows a characteristic graph of a semiconductor laser oscillator in which the amount of returned light is minimum (B1) when the optical output is 5.2 mW.

For example, it is assumed that the optimum focused beam output required for reproducing information (reproducing the optical disk 1) is 0.4 mW. At this time, the optical head 3 (collimator lens 11
a, the polarization beam splitter prism 11b, the quarter-wave plate 11e, and the objective lens 6) optical loss (optical system efficiency) attenuates the light beam output to about 30%. The light beam output of the semiconductor laser oscillator is about 1.3 mW.

However, as can be seen from graphs A and B, when the light beam output is 1.3 mW, the return light noise is a very large value (A2 in graph A and B in graph B).
2). Further, in the region where the returned light noise is practically the minimum (in the graph A, the optical output is around 2.6 mW, and in the graph B, the optical output is around 5.2 mW), the light beam output is too large to be used for reproducing information.

Therefore, in the present invention, the optical attenuator 11f is provided between the semiconductor laser oscillator 9 and the objective lens 6 so that the optical output that minimizes the returned optical noise can be used.

For example, it is assumed that the optimum focused beam output required for information reproduction is 0.4 mW and the optical beam output is attenuated to 30% due to the optical loss of the optical head 3. In this case, when a light beam output of 2.6 mW (output at which optical noise is approximately minimum) is used in the semiconductor laser oscillator having the characteristics of graph A, about 50% of the optical attenuator 11f is emitted from the semiconductor laser oscillator 9. Installed in the optical path of the light beam.
Then, the laser oscillated with the output of about 2.6 mW from the semiconductor laser oscillator is attenuated to the output of about 1.3 mW by the optical attenuator 11f (50% attenuation: A1 → A2 in FIG. 3), and the optical loss of the optical head. (30%) makes it optimal for information playback of approx.
Output of 4mW. Therefore, if an optical attenuator is used, a semiconductor laser oscillator with the characteristics shown in Graph A will have a light beam output of 2.6 mW.
Can be used, and optical noise when reproducing information can be minimized.

Light beam output of a semiconductor laser oscillator having the characteristics shown in graph B: 5.2 mW (output at which optical noise is approximately minimum)
In the case of using, about 75% of the optical attenuator 11f is installed in the optical path of the light beam emitted from the semiconductor laser oscillator 9. Then, the laser oscillated from the semiconductor laser oscillator with an output of about 5.2 mW is attenuated to an output of about 1.3 mW by the optical attenuator 11f (75% attenuation: B1 → B2 in FIG. 3), and the optical loss of the optical head is lost. Is about 0, which is optimal for information playback.
Output of 4mW. Therefore, if an optical attenuator is used, a semiconductor laser oscillator with the characteristics shown in Graph B will have a light beam output of 5.2 mW.
Can be used, and optical noise when reproducing information can be minimized.

Although the case where the optical attenuator is installed in the optical path of the light beam to attenuate the optical output has been described above, the optical head of the present invention can be applied to the case where an optical amplifier is installed in the optical path to amplify the optical output. . That is, when the beam output of the semiconductor laser oscillator required for reproducing information is larger than the optical output that minimizes the return optical noise, the optical output that minimizes the return optical noise is amplified by the optical amplifier. By doing so, even when the beam output required for information reproduction is larger than the optical output that minimizes the return optical noise, the optical output that minimizes the return optical noise can be used.

As a first specific example of the optical attenuator 11f, an ND (Neutral Densit) is generally used in an optical device.
y) Some use a filter called a filter. The ND filter controls the amount of light by dispersing a light absorbing substance in glass in a colloidal form. This ND
An antireflection coating (for example, an AR coating (anti re) is provided on the surface of the filter facing the semiconductor laser oscillator 9.
reflection coating), and antireflection coating may not be applied to the surface on which the reflected light from the optical disk is incident. This prevents the light beam emitted from the semiconductor laser oscillator 9 from being reflected by the surface of the ND filter and returning to the semiconductor laser oscillator 9 again, and allows the light beam reflected by the optical disk to pass through the ND filter. It is possible to prevent the light from entering the semiconductor laser oscillator 9.

Furthermore, as a second specific example of the optical attenuator 11f, there is one that uses an aperture (a diaphragm, an iris diaphragm, etc.) whose aperture ratio can be adjusted. That is, if this aperture is installed in the optical path of the light beam and the aperture diameter is appropriately adjusted, the amount of light emitted from the semiconductor laser oscillator 9 (incident light with respect to the aperture) can be controlled (attenuated) by appropriately changing the aperture ratio. You can

The present invention is not necessarily limited to use with a light beam output (2.6 mw in Graph A, 5.2 mW in Graph B) where the amount of returned light is strictly minimum. For example, according to the present invention, by adjusting the optical attenuation rate of the attenuator 11f as necessary, other than a light beam output that minimizes the amount of return light (a light beam output that reduces the amount of return light compared to the conventional light beam output). Can also be applied to.

[0050]

According to the present invention, it is possible to provide an optical head capable of sufficiently reducing the amount of returning light which is a cause of noise of a semiconductor laser and reducing the influence of noise in an optical disk device.

[Brief description of drawings]

FIG. 1 is a circuit diagram and a block diagram illustrating the configuration of an optical disc device according to an embodiment of the invention.

FIG. 2 is a circuit diagram illustrating in detail the high speed amplifier circuit of FIG.

FIG. 3 is a graph showing a light output-return light noise characteristic of a general semiconductor laser oscillator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk (optical recording medium) 2 ... Motor 3 ... Optical head 4, 5 ... Drive coil 6 ... Objective lens 7, 8 ... Photodetector (photodetection means) 9 ... Semiconductor laser oscillator (light generation means) 10 ... Track Detectors 10, 11 ... Collimator lens 11b ... Polarizing beam splitter prism (light separating means) 11c ... Half prism 11d ... Focus detector 11e ... Quarter wave plate 11f ... Optical attenuator (light energy changing means, light energy attenuating means) ) 12 ... High-speed amplifier circuit 14 ... Laser control circuit 15 ... Focusing control circuit 16 ... Tracking control circuit 17 ... Linear motor control circuit 18 ... Motor control circuit 19 ... Signal processing circuit 20 ... Bus 21 ... A / D converter 22 ... D / A converter 23 ... CPU 24 ... Memory 29 ... Interface 30 ... Operation panel 41 ... Near motor 50 ... High speed operational amplifier 52, 54 ... Servo amplifier C1, C2 ... Capacitor D1, D2 ... Photodiode ND filter (light energy changing means, light energy attenuating means) AR coat (attenuating transmission / reflecting means)

Claims (5)

[Claims] 1. Light generating means for generating light for recording information on an optical recording medium or reproducing information recorded on the optical recording medium; energy of light output from the light generating means. An optical head comprising: a light energy changing means for changing the light energy; and a light detecting means for detecting the reflected light of the light changed by the light energy changing means. 2. Light generation means for outputting light for recording information on an optical recording medium or reproducing information recorded on the optical recording medium with energy such that return optical noise is substantially minimized; A light energy attenuating means for attenuating the energy of the light output from the light generating means to an output required for reproduction and recording on the optical recording medium; and transmitting the light attenuated by the light energy attenuating means, An optical head comprising: a light separating means for separating reflected light of light; and a light detecting means for detecting the light separated by the light separating means. 3. Light generating means for outputting light for recording information on an optical recording medium or reproducing information recorded on the optical recording medium with energy such that return light noise is substantially minimized; Attenuating means for attenuating the energy of the light output from the light generating means to an output required for reproduction and recording of the optical recording medium without substantially changing the phase thereof; and the light attenuated by the attenuating means. An optical head comprising: a light separating means for transmitting and separating the reflected light of the transmitted light; and a light detecting means for detecting the light separated by the light separating means. 4. Light generating means for outputting light for recording information on an optical recording medium or reproducing information recorded on the optical recording medium with energy such that return light noise is substantially minimized; Attenuating transmission reflection means for transmitting the energy of the light output from the light generating means while attenuating to the output required for reproduction and recording on the optical recording medium, and reflecting the reflected light of the transmitted light: the attenuated transmission reflection Light separating means for further transmitting the light attenuated and transmitted by the means and separating reflected light of the transmitted light; and light detecting means for detecting the light separated by the light separating means. And an optical head. 5. Light generating means for generating light for recording information on an optical recording medium or reproducing information recorded on the optical recording medium; and the light generated by this light generating means Optical means for guiding to an optical recording medium; light detecting means for detecting reflected light guided to the optical recording medium by the optical means and reflected from the optical recording medium; between the light generating means and the optical means And a light attenuating means for attenuating the output of the light generated from the light generating means to an output of the light that minimizes the light returning to the light generating means without being detected by the light detecting means. An optical head characterized by comprising.