JPH0242645A - Optical head structure - Google Patents

Abstract

PURPOSE:To contrive the miniaturization of an optical head and the reduction in weight without wasting a detected light interrupted with a knife edge by composing a turning means of the reflecting surface of a reflecting body fixed to the same substrate as a first photodetector and composing a knife edge means of the edge of the reflecting body. CONSTITUTION:The optical head has the turning means to turn a part of a detected light 8 in a different direction, the knife edge means provided on a of optical paths for detecting a focus error condition, etc. The turning means is composed of a reflecting surface 16 of a reflecting body 15 fixed on a same substrate 9 as the first photodetector 13, and the knife edge means is composed of an edge 17 of the reflecting body 15. Thus, the turning means and knife edge can be provided on the single reflecting body 15, a part of the detected light 8 cannot be interrupted by the knife edge means, and the optical head can be miniaturized and, simultaneously reduced in weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Field of Application)] The present invention relates to a 4M optical head structure, and particularly to an optical head structure that can be made smaller and lighter.

<Prior art> Conventionally, there is a high-density recording and reproducing device that performs recording and reproducing by irradiating convergent light onto the recording surface of an optical disk as an optical head type recording medium and detecting the reflected light. . The optical disk used in this device has some warpage or distortion in Mt, and also has eccentricity due to an error in mounting the optical disk to the rotation axis. Therefore,
In order to make the optical head follow the fine recording track of the optical disk without being affected by these errors, the position of the optical head is controlled by detecting each error (A-scrap) and 1-racking.

As the detection light for each error detection, there is a type in which the direction of the reflected light from the optical disk is changed by a polarizing beam splitter, and this changed detection light is further divided into two directions through a half prism. Half of the detected light on one side is blocked by a knife edge, and the so-called knife edge method is used to detect, for example, two detection lights for focus error detection.
The beam is focused on the dividing line of the divided photodiode. In other words, if there is a shift in the focus direction, the focal position will shift to the front or back of the photodiode, so the shift can be easily detected by focusing the light on one of the two split photodiodes. . Also,
The other detection light separated by the half prism is focused on a dividing line of, for example, a two-split photodiode for tracking error detection. In this case as well, if there is a shift in the tracking direction, there will be a difference in brightness between the left and right sides of the condensing section, so the shift can be detected based on the difference in the output of the two-split photodiode.

According to the above structure, focus errors are detected using a knife in one of the detection lights split by the half prism, but half of the light beam incident on the focusing photodiode is blocked by the knife, so the blocked light beam is is a waste. Also, half prism,
Since the optical head and two sets of photodiodes are provided separately, there are many parts and many parts to attach them to, which increases the size and weight of the optical head, making it disadvantageous to achieve high-speed access. There is.

<Problems to be Solved by the Invention> In view of the problems of the prior art as described above, the main object of the present invention is to provide a method for detecting focus errors using the knife method in an optical head structure of the type that uses the knife method to detect focus errors. The object of the present invention is to provide an optical head structure that can be made smaller and lighter without wasting the detection light that is blocked by the detector, and by reducing the number of mounting points for each component.

[Structure of the Invention] Means for Solving the Problems According to the present invention, an object of the present invention is to detect a detection light beam in order to optically detect an error state in either tracking or focusing of an optical head. a first light-receiving element disposed in the optical path; a deflecting means for deflecting a portion of the detected light in a different direction; and a device for optically detecting an error state in either tracking or focusing. an optical head structure comprising: a second light receiving element disposed in the optical path of the detection light deflected; and a knife means disposed in either of the optical paths for detecting the focus error state. In this case, the direction changing means
This is achieved by providing an optical head structure characterized in that the light receiving element and the reflecting surface of a reflector are fixed on the same substrate, and the knife means consists of an edge of the reflector.

In this way, it is possible to detect a focus error by using the knife means consisting of the edge of the repellent for deflecting a part of the detection light, and also to combine the deflection means and the knife means into one unit. Since it can be provided on one reflector, the number of parts and the number of locations for mounting them can be reduced, and since a part of the detection light is not blocked by the knife means, there is no wasted part of the detection light.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the main parts of an optical head to which the present invention is applied. As shown in FIG. 1, a polarizing beam splitter 2 and a λ/4 plate 3 are arranged on the optical axis of the emitted light 1 irradiated toward the optical disk from a semiconductor laser as a light source (not shown). .

By the way, the output light 1 that has passed through the polarizing beam splitter 2
After passing through the λ/4 plate 3, it is reflected by the optical disk to become reflected light 4, which passes through the λ/4 plate 3 again and enters the polarizing beam splitter 2. In this case, the plane of polarization of the reflected light 4 differs from the plane of polarization of the emitted light 1 by 90 degrees. Therefore, the direction of the reflected light 4 is changed within the polarizing beam splitter 2 and is emitted as the detection light 8 from the right side of the polarizing beam splitter 2 in the figure.

A condenser lens 6 and a photometric sensor 7 are coaxially arranged on the optical axis of the detection light 8, and the detection light 8 is arranged coaxially to detect errors in focus and tracking.
The light is focused as convergent light by a condenser lens 6 onto a photometry sensor 1 Noah. In addition, although we have arranged everything from the semiconductor laser to the optical disk on the optical axis of the emitted light 1, it is also possible to arrange mirrors, etc. on the optical axis (to make it possible to change the direction of the optical axis more freely). This does not limit the placement of the .

FIG. 2 is a cross-sectional view of the photometric sensor 7 along the axial direction.
FIG. 3 is a view of the line ■-■ in FIG. 2. Second
As shown in FIG. 3, the substrate 9 of the photometric sensor 7
, a photodiode 13 as a light-receiving element for detecting a racking error and a photodiode 14 as a light-receiving element for detecting a force error are integrated.
Being CJed.

A photodiode 13 for detecting a tracking error is arranged in the optical path of the detection light 8, and a photodiode 14 for detecting a focus error is located at a predetermined distance from the photodiode 13.

As shown in FIG. 3, each of these photodiodes 13 and 14 is constituted by a photodiode element divided into four parts by mutually orthogonal dividing lines. The tracking photodiode 13 is connected to one of the dividing lines,
The focusing photodiode 14 is arranged so that the optical axis of the detection light 8 is perpendicular to the direction in which it deviates in the event of a tracking error, and the focusing photodiode 14 is arranged such that one segment υj line is on an extension of the dividing line of the photodiode 13. It is arranged to be located.

Further, as shown in FIG. 2, a detection light 8 is provided on the substrate 9.
A reflector provided with a reflective surface 16 that is inclined at a predetermined angle (for example, around 65 degrees) with respect to the surface of the substrate 9 so as to reflect half of the light flux on the photodiode 14 side toward the photodiode 14. A mirror body 15 is fixed so as to extend backwardly from the substrate 9. The edge 17 at the extending end of the mirror body 15 is formed as an edge in the Knifezi method that blocks half of the light beam, and the reflected light is divided so that the cross section forms a half-moon shape. In this way, half of the detection light 8 is directly focused on the tracking photodiode 13 without being blocked by the mirror 15, and the remaining half is reflected by the reflective surface 16. , the light is focused on the intersection of the dividing lines of the focusing foot diode 14. Note that each of the photodiodes 13 and 14 is electrically connected to a control circuit (not shown) via a lead wire (not shown) extending from the substrate 9.

Next, the method for detecting each error in tracking and error by each photodiode 13 and 14 will be described below.

As shown in FIG. 4, half of the detected light 8 is focused on the photodiode 13 in a half-moon shape, as shown by the imaginary line, and if a tracking error occurs, the leading axis will be This results in a shift in either the left or right direction. In addition, from each photodiode element, the detection signal E~[-1 corresponding to each irradiation pattern is (E+F) and (
G+H) are input to each amplifier 19 and 20, respectively, and the difference between (F+F> and (G+H) is outputted to the control circuit by amplifier 2).Therefore, a tracking error occurs. In this case, (E+F) and (G
+1-1), it is possible to detect the amount of racking error from 1 to 1.

In addition, in FIG. 5, the remaining half of the detection light 8 whose direction has been changed by the reflecting surface 16 is almost focused as shown by an imaginary line on the intersection of the dividing lines of the four divisions 741 to the diode 14. 15'X, indicating a state where no focus error has occurred. Similarly to the above, detection signals A to D corresponding to each irradiation pattern are generated from each photodiode element of the photodiode 14 as (A
-+-B) and (C+D>) are input to each amplifier 22.23, and furthermore, (A0B> and (C
+D) is outputted to the control circuit by the amplifier 24. Incidentally, as mentioned above, the light beam for focusing is
The cross section is divided into half-moon shapes by the edges 17 of 5 and the reflective surfaces 16.

When the focus changes and, for example, the focal position is in front of the photodiode 14, one side of the photodiode 14 (lower half side in the figure) as shown in FIG.
When the focal point position is on the back side of the photodiode 14, the light is focused on the other side of the photodiode 14 (the upper half side in the figure) as shown in FIG. Therefore, when a force error occurs, the output difference between (A + B) and (C + D) of the detection signals of each pair of diode elements of the photodiode 14 is used to detect the Direction and errors 1 can be easily detected. Note that the read signal is the sum of the detection signals E-H of the tracking photodiode 13 (EfF
10G+11).

Furthermore, according to this embodiment, since the photodiodes for detecting errors in focus and tracking are combined on one substrate, wiring to the photodiodes is simplified, and noise resistance can be improved. Since the tip shaft adjustment only needs to be done in one place, it has the effect of shortening the adjustment time.

Further, FIG. 8 shows a second embodiment of the invention based on the present invention.
3, the same parts as those in the previous embodiment are given the same reference numerals, and detailed explanation thereof will be omitted. In this second embodiment, the inclination angle of the reflective surface 16 of the mirror body 15 is 45 degrees, and in this case, the substrate 9 is bent at a right angle to form a single character shape, and the tracking The focusing photo diode A is placed on the light receiving surface of the photo diode 13
- The light-receiving surfaces of the cards 14 are arranged so as to be perpendicular to each other. In addition, each 7
The procedure for detecting each error using ToDie A-Code 13.14 is as follows:
Since this is the same as the previous embodiment, the explanation thereof will be omitted.

Further, FIG. 9 shows a second embodiment showing a third embodiment based on the present invention.
3, the same parts as those in the previous embodiment are given the same reference numerals, and detailed explanation thereof will be omitted. This third
In this embodiment, a prism is formed by bonding together a transparent body having a parallelogram cross section and a transparent body having a right triangular cross section, both of which are homogeneous and made of the same material, so as to have a trapezoidal cross section. The body 25 is provided so as to be in close contact with and cover both of the foot diodes 13 and 14.

According to this structure, the bonding surface of the prism body 25 is
It is located above the photodiode 13 and at an angle of 45 degrees with respect to the surface of the substrate 9, and the bonded surface has a reflective surface so that half of the detection light 8 is incident on the photodiode 14 side. A reflective film 26 is attached thereto.

Incidentally, the reflective film 27 having a refracted surface is directed toward the prism body 25 so that half of the detection light 8 whose direction has been changed by the reflective film 26 is focused on the photodiode 14.
It is pasted parallel to the Also in this third embodiment, the procedure for detecting errors by each photodiode 13, 14 is the same as in the previous embodiment, and therefore the explanation thereof will be omitted.

In addition, although a 4-split photodiode was used for each photodiode 13 and 14, in the photodiode 13 (E+
F) and (G1), and photodiode 14
So, we decided to divide it into (A+8> and (C+D>).
A split photodiode may also be used. Alternatively, each photodiode 13, 14 may be replaced. In this case, half of the detection light 8 is used directly for focus error detection, but the remaining half of the detection light 8 whose direction has been changed is used for that purpose. Each error detection can be performed by focusing at a point 9 in the middle of the optical path and using the virtual image for tracking error detection.

[Effects of the Invention] As described above, according to the present invention, errors in either tracking or focusing are detected by the detection light whose direction is changed on the reflecting surface of the reflector having a knife means for detecting focus errors. Since a part of the detection light is not blocked, there is no wasted part of the detection light.

Furthermore, since the deflection means and the knife means are provided in one reflector, the number of parts and the locations where they are attached can be reduced, the optical head can be made smaller and lighter, and high-speed access is possible. , the effect is extremely human.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the main parts of an optical head to which the present invention is applied. FIG. 2 is a cross-sectional view of the photometric sensor along the axial direction. FIG. 3 is a sectional view taken along the line ■--■ in FIG. 2. FIG. 4 is a schematic circuit diagram showing how to detect a tracking error. 5 to 7 are schematic circuit diagrams showing the focus error detection procedure. FIG. 8 is a diagram corresponding to FIG. 2 showing the second embodiment. FIG. 9 is a diagram corresponding to FIG. 2 showing the third embodiment. 1... Outgoing light 2... Polarizing beam splitter 3... λ/4 plate 4... Reflected light 6... Condensing lens 7... Photometry sensor 8... Detection light
9...Substrate 13.14...Photodiode

Claims (1)

[Claims] a first light-receiving element disposed in the optical path of the detection light to optically detect an error state in either tracking or focusing of the optical head; and a first light-receiving element for redirecting a portion of the detection light in a different direction. a second light-receiving element disposed in the optical path of the deflected detection light for optically detecting an error state in either tracking or focusing; and a knife edge means provided on either of the optical paths for detecting the light, wherein the direction changing means includes a reflector fixed on the same substrate as the first light receiving element. An optical head structure comprising a reflective surface, wherein the knife edge means comprises an edge of the reflector.