JP2583569B2 - Optical head device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device provided in a head section of an optical information recording / reproducing device or the like, and in particular, a focusing objective lens provided in an optical head. The present invention relates to an optical head device capable of detecting a displacement position of an optical head.

[Conventional technology]

Conventionally, an optical head is a light source such as a laser, a collimator lens that converts a light beam from the light source into a parallel light beam, an optical system such as an objective lens for narrowing down the light beam on the medium surface of the information recording medium and irradiating it as a smiling spot, and It is composed of a photodetector and the like for receiving the light beam reflected by the surface. At the time of recording, a light beam modulated by predetermined information and focused by an objective lens is irradiated onto the medium surface, and the information is recorded on the medium surface by a temperature rise or a chemical reaction. At the time of reproduction, light is received by a photodetector which is reflected from the medium surface and optically modulated by recorded information, and the optical signal detected here is converted into an electric signal to obtain desired reproduced information.

Information recording media used for such optical information recording and reproduction include optical video discs and optical digital media.
There are audio disks, optical cards, and the like. The information to be recorded is, for example, concentrically or spirally in the case of a disk-shaped medium (hereinafter referred to as an optical disk), or is arranged in parallel in the case of a card-shaped medium to form an information pattern. I have. This information pattern is asperities, presence or absence of bits,
Some are caused by a change in reflectance, a change in magnetization direction, or the like.

By the way, for example, when recording / reproducing information by rotating the above-mentioned optical disk, the information recording surface on the disk is several hundred μm in one rotation due to the warpage of the disk base, surface run-out, etc.
It moves up and down in the radial direction. Further, the information track on the disk also moves in the radial direction of several hundred μm during one rotation due to eccentricity, distortion and the like. Under such disc fluctuations, the light spot from the objective lens must always accurately follow the information tracks on the disc.

For this reason, various conventional means are used to perform auto-focusing control for controlling the distance between the objective lens and the disc as the information recording medium to a constant distance so that the focused light from the objective lens is always kept at a constant smiling spot. In addition, automatic tracking control for accurately tracing the information track is performed. The detection range of the error detection signal used for these controls is about ± several tens of μm for the focusing error signal and about ± several μm for the tracking error signal. However, as described above, in the case of an optical disk, the amount of fluctuation of the disk due to eccentricity or surface deviation is about ± several hundred μm in both the radial direction and the vertical direction of the disk. Therefore, before the focusing or the auto tracking control is started, or when such control is deviated due to an external impact or the like, it is necessary to pull the objective lens to the detection range of the error signal. . In order to perform such pull-in accurately and quickly, it is necessary to detect the absolute position of the objective lens within a range of ± 100 μm, which is the fluctuation amount of the disk. Further, when an error occurs in the error signal due to the optical blur caused by the movement of the objective lens, such a position detection of the objective lens is also required for controlling the movement of the objective lens.

As means for detecting the absolute position of the objective lens for this purpose, there is a conventional apparatus shown in FIG. The apparatus shown in FIG. 1 includes an objective lens 2 for focusing a light beam 3 emitted from a light source (not shown) on the medium surface of the information recording medium 1, and a cylindrical support 15 for supporting the objective lens. Then, the cylindrical magnetic members 8 and 9 provided via the magnetic gap 10, the magnet 7 which generates a parallel magnetic flux in the magnetic gap 10, and the support 15
The support 15 can be moved up and down through the cylindrical gap 6 by the electromagnetic force generating means including the coil 5 wound around the support. An LED 11 is provided at one end on the cylindrical magnetic body 9, and a phototransistor 12 is provided at a position facing the LED 11 via a cavity of the cylindrical magnetic body 9 in which the support 15 moves up and down. The light is emitted from the LED 11 toward the phototransistor 12 and is received by the phototransistor 12. With such a configuration, when the support 15 of the objective lens 2 moves up and down, the support 15
The tip of 15 blocks light emitted from the LED 11 toward the phototransistor 12, and the amount of light received by the phototransistor 12 changes according to the amount of movement of the support 15.
The displacement of the objective lens 2 can be detected from the output change amount from the phototransistor 12 thus obtained.

[Problems to be solved by the invention]

However, in the conventional device as described above, due to the deterioration of the LED 11, the light emission amount of the LED decreases with time, an offset occurs in the detection output of the phototransistor 12, and the modulation degree due to the movement of the objective lens is small. However, there is a problem that the influence is large as compared with the method described above and accurate position detection cannot be performed.

〔Purpose〕

The present invention has been made in order to solve the above-described problems of the conventional technology, and has a simple configuration, and can be performed for a long time without being affected by environmental changes such as ambient temperature or changes over time. It is an object of the present invention to provide an optical head device capable of accurately detecting the position of an optical system over time.

[Means for solving the problem]

According to the present invention, there is provided an optical head device including a fixed member and a moving member to which an optical system is fixed, wherein the fixed member and the moving member each include a light-emitting element on one of the members. A light receiving element is provided, and a reflection plate for reflecting the light beam emitted by the light emitting means and irradiating the light beam to the light receiving element is provided on the other member. And a difference detection means for detecting a difference between the light emission amount and the light emission amount of the light emitting element is controlled based on a difference between the light emission amounts detected by the difference detection means. This is achieved by the optical head device.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing one embodiment of the optical head device of the present invention.

In FIG. 1, portions having the same functions as the portions shown in the conventional example of FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, the optical head device of this embodiment
Except for the objective lens position detecting means in the conventional apparatus shown in FIG. The optical position detecting means in the present embodiment is a light emitting element driven by a variable constant current source 30 capable of flowing a current of an arbitrary value to the reflecting mirror 22 provided on the support 15. The light emitted from the light emitting diode 20 is irradiated, and the reflected light is received by a phototransistor 21 which is a light receiving element, and an output photoelectrically converted by the phototransistor is amplified by an amplifier 31. Light emitting diode
Since the reference numeral 20 and the photodiode 21 are fixed on the cylindrical magnetic body 9, the position of the support pair 15, that is, the position of the objective lens 2 can be obtained from the amount of light incident on the photodiode 21.

Since the light emission amount of the light emitting diode 20 changes with time, in the present invention, the light emission amount is corrected as a stage before performing the position detection.

The reference numeral 40 denotes an indicator for setting the position of the light emitting diode 20 at the time of correcting the light emission amount. Coil 5 with the support
By supplying a current sufficient to allow the support 15 to contact the support 40, the support 15 is fixedly held at a fixed position. The fixed holding position is a position at which the amount of light required for correction can be obtained without limiting the movable range of the objective lens.

In this fixed state, the output of the phototransistor 21 is input to an A / D converter (analog / digital converter) 32 via an amplifier 31. The controller 34 outputs the output of the A / D converter 32 to a reference value stored in advance (that is,
Desired light-emitting diode light emission) and compare the difference
It is output to the D / A converter 33.

The movable current source 30 changes the light emitting diode drive current value based on the output from the D / A converter 33 to set the light emission amount of the light emitting diode to a constant value without a change over time.

After the correction operation, the current flowing through the coil 5 to fix the support 15 at a constant level is cut off, the support 15 returns to the steady position, and the position detection is in a normal operation state.

In the above-described embodiment, the detection of the position of the objective lens in the focus direction by the optical position detection means has been described. However, it is apparent that the same effect can be obtained with the same configuration in the tracking direction.

Further, in the above-described embodiment, the description has been made by using the optical disk. However, the information recording medium is not limited to this, and the present invention is effective even with an optical card, an optical tape, or the like.

〔The invention's effect〕

As described above, according to the present invention, the light emission amount of the light emitting element of the position detector is variably set to a predetermined amount by holding the objective lens at a predetermined position for correcting the light emission amount before sending the position detection signal. Since the position detection signal is extracted after controlling the current source, accurate position detection of the optical system (objective lens) is possible with a simple configuration for a long time and without being affected by environmental changes such as ambient temperature. The optical head device described above can be provided.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an optical head device according to the present invention, and FIG. 2 is a sectional view showing a conventional example of the optical head device. DESCRIPTION OF SYMBOLS 1 ... Information recording medium, 2 ... Objective lens, 20 ... Light emitting diode, 21 ... Photodiode, 22 ... Reflection mirror, 30 ... Variable current source, 31 ... Amplifier, 32 ... A / D conversion , 33 ... D / A converter, 34 ... Controller.

Claims (1)

(57) [Claims] 1. An optical head device comprising a fixed member and a moving member to which an optical system is fixed, wherein the light emitting element and the light emitting element optically detect a position of the moving member with respect to the fixed member. An optical position detecting means including a light receiving element for receiving the light beam emitted by the light emitting device, and a difference between a light amount received by the light receiving element and a reference light amount when the moving member is positioned at a predetermined position with respect to the fixed member. An optical head device comprising: a difference detecting unit that detects the light amount; and a control unit that controls the light emitting element based on the difference so that the light emitting amount of the light emitting element becomes the reference light amount.