JPS62112235A - Position detecting device for objective lens - Google Patents

Abstract

PURPOSE:To prevent the effect of the adverse influence to the motion of the lens barrel and to correctly detect the position of the objective lens by providing the reflecting means having a 1/4 wavelength plate and a reflection mirror in the lens- barrel as well as the objective lens. CONSTITUTION:At a glass plate 6 of a lens barrel 2, a 1/4 wavelength plate 7 and a reflection mirror 8 having the size of the extent that the information reading is not troubled are provided and a part of a main beam 3 is guided through the glass plate 6 and the 1/4 wavelength plate 7 to the reflection mirror 8. Since the luminous flux reflected by the reflection mirror 8 passes through the 1/4 wavelength plate 7 two times and the polarizing direction is rotated to 90 deg., the flux transmits a polarizing film 5a of a polarizing beam splitter 5. The reflecting light by the reflection mirror 8 to transmit the polarizing film 5a is received by a light receiving element 9 having light receiving areas 9a and 9b divided into two in the tracking direction, the output of respective light receiving areas 9a and 9b is supplied to a signal processing circuit 10 and in the signal processing circuit 10, the difference in the output of the complementarily changing light receiving areas 9a and 9b is detected. Thus, the position signal is obtained which shows the quantity and the direction of the dislocation from the neutral position of an objective lens 1 in the tracking direction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information reproducing device that reproduces information recorded on an optical recording disk, for example, in which a light spot beyond an objective lens that irradiates a light spot onto the disk is used. The present invention relates to a device for detecting a position in a direction perpendicular to an axis.

[Conventional technology]

In an optical information reproducing apparatus, a focusing servo and a tracking servo are generally applied so that a spot irradiated from an objective lens traces an information track in a converging state.

In such an optical information reproducing device, when performing random access to move the readout start position of the information track to an arbitrary location, tracking is forcibly removed and the pickup body with the objective lens is moved near the target track. The tracking servo is retracted by moving the objective lens, but in this case, depending on the position of the objective lens, the retraction of the tracking servo may not be stable and it may take time to reach the target track.

Conventionally, a method to solve this problem is to use a sensor to detect the movement of the objective lens in the tracking direction, and apply a brake to the objective lens based on the information obtained from this sensor when tracking is off. is known, and those shown in FIGS. 6 and 7 have been proposed as such objective lens position detection devices.

The position detection device shown in FIG. 6 holds an objective lens 101 and has electrodes on a lens barrel 102 that is movable in the tracking direction.
103, and fixed electrodes 104a are provided on both sides in the tracking direction, facing the electrode 103.

104b to form two variable capacitors, a high frequency power source 105 is connected between the electrode 103 and the fixed electrodes 104a and 104b, and changes in their capacitance are detected by a signal processing circuit 106. The position signal is obtained by using the

Further, the position detection device shown in FIG.
A total reflection prism 107 is installed in a lens barrel 102 that holds a total reflection prism 107. Light is projected from a light emitting element 108 onto this prism 107, and the light reflected by the prism 107 is divided into two in the optical axis direction to form light receiving areas 1i2109a and 109b. The light receiving element 109 receives the light, and each light receiving area Vl 109a, 10
A change in the output of 9b is detected by a signal processing circuit 110 and a position signal 19 is generated.

(Problems to be Solved by the Invention) However, the position detection device shown in FIG. 6 has the problem that the signal processing becomes complicated because it detects capacitance. In the position detection device shown in FIG. 7, there is a dedicated light emitting element 108 and a relatively large total reflection prism 107 that covers the movable plane in the tracking direction.
There is a problem in that it becomes large because of the need for it. Furthermore, in both devices, an electrode 1 is provided on the outer surface of the lens barrel 102.
03 and total reflection prism 107, the lens barrel 102
The center of gravity of the movable parts including
Undesirable high-order resonance occurs in the support mechanism that supports the servo and l-racking E with high accuracy in the focusing and tracking directions.
There is a problem that Nervo becomes impossible.

This invention was made by focusing on these conventional problems, and it can be made simple and compact, and is suitable for detecting the position of the objective lens with high accuracy without adversely affecting the 1j--bo system. An object of the present invention is to provide an objective lens position detection device configured as follows.

[Means and operations for solving the problem] In order to achieve the above object, the present invention holds an objective lens and includes an objective lens in a lens barrel that is movable in a predetermined direction perpendicular to its tip axis. A reflecting means having a single wavelength plate and a reflecting mirror is provided so as to reflect a part of the main beam entering the barrel while changing its polarization direction, and a reflecting means is provided in the optical path of the main beam entering the lens barrel. A polarizing beam splitter is provided that emits the light beam reflected by the main beam in a direction different from the optical path of the main beam. The light is received by a light receiving means having a light receiving area divided into at least two parts so as to obtain an output, and based on the output, the position of the objective lens in the direction of movement of the lens is detected.

〔Example〕

FIG. 1 shows a first embodiment of the invention. An objective lens 1 is held in a lens barrel 2 that is movable in one rotation direction indicated by a double arrow, and the objective lens 1 irradiates a main beam 3 onto an optical disc 4 in a spot shape. This implemented VAT is performed by providing a polarizing beam splitter 5 in the incident optical path of the main beam 3, and reflecting the main beam 3 with the polarized light 11!5a of the polarizing beam splitter 5 to the objective lens 1.
lead to.

Further, the lens barrel 2 is provided with a transparent glass plate 6, and this glass plate 6 has 1/4 of a large serration that does not interfere with information reading.
A wavelength plate 7 and a reflecting mirror 8 are provided to direct the main beam 3.
A part of the light is guided to a reflection mirror 8 through a glass plate 6 and a wave plate 7, and the light incident on this reflection mirror 8 is converted into 1.2 waves by the reflection mirror 8 through a plate 7 and a glass plate 6. Let them do it.

In this case, the light beam reflected by the anti-at mirror 8 passes through the wavelength plate 7 twice and its polarization direction is rotated by 90 degrees, so that the polarized light 11W5a of the polarizing beam splitter 5 is transmitted. In this embodiment, this polarizing film 5a
A light receiving element 9 having light receiving areas 9a and 9b that divides the light reflected by the reflecting mirror 8 into two in the tracking direction.
The outputs of the respective light receiving areas 9a and 9b are supplied to the signal processing circuit 10.

Here, when the light receiving element 9 is in the neutral position of the lens barrel 2, the light reflected by the reflecting mirror 8 is placed in the light receiving area 9 as shown in FIG. 2A.
It is arranged so that it is equally incident on a and 9b. In this way, when the lens barrel 2 moves to the left in FIG.
As shown in Figure B, the light receiving area 9a increases, and the light receiving area 9
It decreases in b. Also, when In2 moves to the right,
As shown in FIG. 2C, on the contrary, it decreases in the light receiving area 9a,
It increases in the light receiving area 9b. Therefore, in the signal processing circuit 10, the light receiving areas 9a and 9b change in a complementary manner.
By detecting the difference in the outputs of , it is possible to obtain a position signal representing γ and the direction of the deviation of the objective lens 1 from the neutral position in the tracking direction.

According to this embodiment, since a part of the main beam 3 is used, the position of the objective lens 1 can be detected with a simple configuration without using any special electric circuit or light source. Also,
Since the k-wavelength plate 7 and the reflection mirror 8 can be attached to the glass plate 6 and fitted into the lens barrel 2 in the same way as the objective lens 1, it is easy to align the center of gravity of the movable parts including the lens barrel 2. Become.

Therefore, undesired resonance will not occur, so
There is no adverse effect on focusing servo and tracking servo. Furthermore, the k-wavelength plate 7 and the reflection mirror 8 are arranged within the lens barrel 2, and the polarizing beam splitter 5 and the light receiving cable 9 can be arranged relatively freely with respect to the optical path of the main beam 3. , there is also the advantage that it can be made smaller.

FIG. 3 shows the main part of a second embodiment of the invention. In this embodiment, the light receiving element 9 is connected to the polarizing beam splitter 5.
The only difference from the first embodiment is that it is arranged parallel to the polarizing film 5a.

FIG. 4 shows the main part of a third embodiment of the invention. In this embodiment, a main beam 3 is transmitted through a polarizing film 5a of a polarizing beam splitter 5 and guided into a lens barrel 2 via a reflecting prism 11, and a light beam reflected by a reflecting mirror 8 in the lens barrel 2 is passed through a reflecting prism. The only difference from the first embodiment is that the light is reflected by the polarizing film 5a of the polarizing beam splitter 5 through the polarizing beam splitter 11 and received by the light receiving element 9.

These second and third embodiments can also achieve the same effects as the first embodiment.

FIG. 5 shows a fourth embodiment of the invention. In this embodiment, two reflecting sections are provided on the glass plate 6, one consisting of a wavelength plate 7a and a reflecting mirror 8a, and the other consisting of a quarter wavelength plate 7b and a reflecting mirror 8b. and is reflected by the polarizing beam splitter 5.
A light receiving area 12a to 1 is obtained by dividing the light beam that passes through the polarizing film 5a into four parts such that two light receiving areas #4 correspond to each reflecting part.
The light is received by the light receiving element 12 having a diameter of 2d, and the sum of the outputs of the light receiving areas [12a and 12c on one side corresponding to each reflecting part] and the sum of the outputs of the light receiving areas 12b and 12d on the other side are added to each adding circuit. 13a and 13b, and these adder circuits 13a and 13 in the signal processing circuit 10.
The only difference from the first embodiment is that the position signal of the objective lens 1 is obtained based on the difference in the outputs of 1).

In this embodiment, two reflecting parts are provided, and a light receiving area on one side corresponding to each reflecting part is lit! Since the position of the objective lens 1 is detected based on the difference between the sum of the outputs of the light receiving areas 12a' and 12c and the sum of the outputs of the light receiving areas 12b and 12d on the other side, the effect of the first embodiment is achieved. In addition, highly accurate position detection can be performed.

Note that this invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, in the embodiment shown in FIG.
They may be arranged as shown in the figure, or an optical system as shown in FIG. 4 may be applied to receive the reflected light from each reflecting section.

(Effects of the Invention) As described above, according to the present invention, the reflecting means having the radio wave plate and the reflecting mirror is provided in the lens barrel in the same way as the objective lens, so that it has no negative effect on the movement of the lens barrel. It is possible to accurately detect the position of the objective lens without causing interference.Also, since a part of the main beam is used for position detection, there is no need to use a special electric circuit such as a capacitor or a dedicated light source. Therefore, it can be easily and compactly made.

[Brief explanation of drawings]

Fig. 1 shows a first embodiment of the invention, Fig. 2 A to C
3 is a diagram showing the main part of the second embodiment of the present invention, FIG. 4 is a diagram showing the main part of the third embodiment, and FIG. 5 is a diagram showing the main part of the third embodiment. FIGS. 6 and 7 are diagrams showing conventional techniques. 1... Objective lens 2... Lens barrel 3... Main beam 4... Optical disk 5... Polarizing beam splitter 5a... Polarizing film 6... Glass plate 7...
- Wave head 8... Reflection mirror 9... Light receiving element 9a, 9b... Light receiving area 10... Signal processing circuit 11... Reflecting prism 7a, 7b...
・1/4 wavelength plate 8a, 8b...reflection mirror 12
... Light-receiving cables 12a to 12d... Light-receiving areas 13a, +3b... Addition circuit patent applicant Olympus Optical Industry Co., Ltd. No.
Figure 2 Figure 3 Figure 1 Qa Exit Figure 7 Procedures Amendment Written on December 12, 1985 Mr. Michibu Uga, Commissioner of the Patent Office 1, Indication of Case 1985 Patent Application No. 251836 No. 2, Name of the invention Objective lens position detection device 3, ? Relationship with the case of the person making the correction Patent applicant (OA7) Olympus Optical Industry Co., Ltd. 4, Agent 1
・Correct it to "Status". 2. On page 8, line 14, "these electrodes" is corrected to "these forces. poles." 3. On page 4, line 15, "to wear" is corrected to "to wear."

Claims (1)

[Claims] 1. It is installed in a lens barrel that holds an objective lens and is movable in a predetermined direction perpendicular to its optical axis, and reflects a part of the main beam that enters the lens barrel by changing its polarization direction. a reflecting means having a /4 wavelength plate and a reflecting mirror; disposed in the optical path of the main beam entering the lens barrel;
a polarizing beam splitter that emits the light beam reflected by the reflecting means in a direction different from the optical path of the main beam; and a polarizing beam splitter arranged to receive the light beam reflected by the reflecting means emitted from the polarizing beam splitter, and the lens barrel. a light receiving means having a light receiving area divided into at least two parts so as to obtain complementary outputs according to the movement of the lens barrel, and detecting the position of the objective lens in the moving direction of the lens barrel based on the output of the light receiving means. An objective lens position detection device comprising means.