JPH01269248A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To unite an optical recording and reproducing device with another optical member by joining the both curved surfaces of a first lens, which has a plain surface and a projecting surface, and a second lens, whose refraction factor is different, to have a plain surface and the recessed surface of a radius of curvature, whose refraction factor is almost same as the above mentioned projecting surface. CONSTITUTION:A synthetic optical member 90 is formed by joining the respective projecting surface and recessed surface of equal radius of curvature R91 and R92. Then, respective refraction factors n91 and n92 have the relation of n91>n92 and the member 90 is optically operated as a convex lens. A diffusing light flux outgoing from a semiconductor laser 1 is passed through a collimator lens 2 and condensed on the recording film of an information carrier 8 through a united light flux shaping prism 3, a beam splitter (BS) 4, a reflection mirror 5, a lambda/4 board 6 and an objective lens 7. The reflected light reversely advances and passes through a synthetic optical member 90 to be connected to the BS4. Then, the light is divided into two lights by a half prism 10 and incoming to a two-dividing optical detector 11. After that, the light is incoming through a knife edge 12 to a two-dividing optical detector 13 and tracking and focusing control is respectively executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording/reproducing device for recording, reproducing, or erasing information on an information carrier, and particularly relates to improvements in optical members used in the device.

[Conventional technology]

FIG. 6 is a perspective view showing a conventional optical recording/reproducing apparatus described in, for example, Japanese Patent Application Laid-Open No. 61-210541, and particularly illustrates the optical path and the state of each optical member provided on the optical path. . In the figure, (1) is a semiconductor laser as a light source, and (2) is a collimating lens. (3) is a beam shaping prism that shapes parallel beams, (4) is a polarizing beam splitter, (5) is a reflecting mirror, (6) is a quarter wavelength plate, and the beam shaping prism (3) is a polarizing beam splitter. (4), reflective mirror (5) and 174 wavelength plate (6)
are mutually integral. The integrated configuration of these optical members will be described in detail later. (7) is the objective lens,
(8) is an information carrier in which a recording film (8a) is formed;
(9) is a convex lens, Orj is a half prism, and θ0 is 2
The split photodetector is used to control the position of the objective lens (7) in the direction of arrow T for detecting track position errors. (+2) is a knife that blocks part of the luminous flux, +
A two-split photodetector 131 is used to control the position of the objective lens (7) in the direction of arrow F for detecting focus errors.

Next, the operation will be explained. The diverging light beam 0→ emitted from the semiconductor laser (1) is converged by the collimating lens (2) and converted into a parallel light beam u9. Parallel luminous flux (+51
further enters the beam shaping prism (3), and as shown in detail in Figure 7, its beam diameter is expanded to a beam diameter H.
becomes an expanded parallel light flux σ0. The expanded parallel beam ue passes through a polarizing beam splitter (4), is reflected by a reflecting mirror (5), passes through a quarter-wave plate (6), and is recorded on an information frame (8) by an objective lens (7). The light is focused into a minute spot on the film (8a). Next, 1 from information phase (8)
The reflected light is transmitted through the objective lens (7) and the quarter-wave plate (6).
, is reflected by the reflecting mirror (5), and is further reflected by the polarizing beam splitter (4) to become a reflected beam (17).The reflected beam u71 is condensed by the convex lens (9),
Approximately half of the amount of light passes through the half prism Ol and enters the two-split photodetector θ0 for detecting a track position error.

This two-split photodetector 00 is placed at a position shifted by a predetermined distance from the condensing point of the convex lens (9). Convex lens (9)
The other half of the luminous flux focused by is incident on the half pre-split photodetector 0J. This two-split photodetector 03 is placed at the focal point of the convex lens (9).

A track position error signal is obtained from the difference between the output signals of the two-split photodetector (+1), and a control circuit and an actuator (not shown) to which this signal is input control the objective lens (7) to the radius of the information carrier (8). It is driven in the direction indicated by arrow T in FIG. 6 to perform so-called tracking control in which the light spot follows the eccentricity of the information carrier (8) rotating around the center of rotation θ.

Further, a focus error signal is obtained from the difference between the output signals of the two-split photodetector u3, and the control circuit and actuator similarly drive the objective lens (7) in its focal direction, that is, in the direction shown by arrow F in FIG. So-called focusing control is performed to cause the light spot to follow the surface deflection of the information carrier (8). Note that the reproduction signal for reproducing the information recorded on the information carrier (8) can be obtained from the sum of the output signals of the two-split photodetector 01).

Among the optical members used in the optical recording and reproducing device, the beam shaping prism (3), the polarizing beam splitter (4),
The reflecting mirror (5) and the quarter-wave plate (6) are integrally constructed as described above, and this is for the following reason. That is, it goes without saying that each of these optical members of this device needs to satisfy each required optical function, but also the semiconductor laser (1), the information carrier (8), and the photodetector α003. High dimensional and surface accuracy is required, especially in the installation process, so that the mutual optical axes can be placed in a predetermined positional relationship.

Since this dimensional accuracy is originally required between each member, the accuracy of the optical system as a whole with respect to the casing of the optical recording/reproducing device only needs to fall within a certain predetermined error range. However, if each optical component is individually attached to the housing, the overall allowable error will be allocated to each component, so the precision required for each component will tend to become even stricter, and It is necessary to provide a positioning surface on the casing for each member, which makes the structure complicated and requires difficult processing. Therefore, by integrating a plurality of optical members into one piece, it is possible to simplify the structure and improve workability.

[Problem to be solved by the invention]

As explained above, it is desirable to integrate as many optical members as possible. However, in conventional optical recording and reproducing devices, the beam shaping prism (3), the polarizing beam splitter (4), the reflecting mirror (5), and the quarter-wave plate (6) are only fixed together as described above. . That is, since the optical member described above has a flat surface through which light enters and exits, it can be relatively easily integrated by joining adjacent flat surfaces. However, for example, the convex lens (9) has a convex surface on one of its light entrance/exit surfaces, and cannot be joined to the above-mentioned integral member having a planar structure, making it impossible to eliminate the above-mentioned drawbacks when the members are attached individually. There was a point.

This invention was made in order to solve the above-mentioned conventional problems, and it is an optical recording and reproducing method that allows optical members with curved surfaces, such as the convex lens (9), to be integrated with other optical members. The purpose is to obtain equipment.

[Means to solve the problem]

The optical recording/reproducing device according to the present invention is characterized in that at least one of the optical members to be integrally fixed is connected to a first lens in which one of the light entrance and exit surfaces is formed as a flat surface and the other as a convex surface, and a first lens having a refractive index as a first lens. A second lens, which is different from that of the first lens, has one of the light entrance and exit surfaces being flat and the other having a radius of curvature approximately equal to the convex surface of the first lens, and each formed on a concave surface joined to the convex surface. This is a synthetic optical member.

[For production]

The synthetic optical member in this invention has its first and second
Although both lenses optically function as convex or concave lenses due to the difference in their refractive index, structurally speaking, both of their light entrance and exit surfaces are flat, so they are also formed flat. It can be easily joined to other optical members, and the optical members can be more thoroughly integrated.

[Embodiments of the invention]

FIG. 1 is a perspective view showing an optical recording/reproducing apparatus according to an embodiment of the present invention, and corresponds to FIG. 6 of the prior art. In the figure, (1) to f81. Qtll~0 barrels are the same as in the conventional case, so the explanation will be omitted. ■ is the first lens T! detailed below! A convex lens as a composite optical member formed by joining J11 and a second lens (support), and includes conventional optical members such as a beam shaping prism (3), a polarizing beam splitter (4), a reflecting mirror (5), 1/4 wavelength plate (
6) and the half prism OI are combined into an integral structure.

Figure 2 shows the entire convex lens ■ and both lenses (9Ll
1921 is a perspective view showing the lens separated in the direction of the Y-axis, which is its optical axis, and FIG. 3 is a cross-sectional view of the convex lens ■ in FIG. 2 taken along a plane including the Y-axis and viewed from the X-direction. . In the figure, (9Ll is the first end face in the Y-axis direction formed on a plane perpendicular to the Y-axis, and the other on a spherical convex surface with a radius of curvature R9I whose center lies on the Y-axis. It is a lens whose refractive index is nl.On the other hand, ■ is a spherical concave surface with one end face on a plane perpendicular to the Y-axis and the other with a radius of curvature R92 whose center lies on the Y-axis. and a second lens formed respectively in the second lens, the refractive index of which is n!.

Here, the radius of curvature R, , R, and the refractive index n91 e
nl! are set so that the following relational expressions hold true.

R91” R92・・・・・・・・・・・・・・・・・・
・ (1) n9+ > 19g ・・・・
・・・・・・・・・・・・・・・ (2) That is, R91”
R9! Therefore, the convex and concave surfaces of both lenses (911 (support)) are in complete contact with each other, and when both convex surfaces are bonded together with an adhesive etc., the entire lens has a perfect rectangular outer shape, a composite optical member. ■It becomes.

Next, it will be explained with reference to FIG. 4 that this composite optical member t91 optically functions as a convex lens.

FIG. 4 is a view of the main optical path section of the present invention viewed from the direction of arrow Z in FIG. However, for convenience, the portion of the knife 0~ and the two-split photodetector a3 is placed 90 degrees around its optical axis.
°Drawing rotated.

When this lens action is expressed by the focal length f, its value is as shown in the following equation.

Here, considering the refractive index relationship (2), f>O from equation (3).

That is, the synthetic optical member (2) optically serves as a convex lens since f>o and condenses the reflected light flux Oη.

Therefore, this embodiment also achieves the same operation as the conventional device.

However, in terms of construction, the integration of optical members has been expanded to include the convex lens (9), which corresponds to the conventional convex lens (9), to the half prism O■, so the dimensional accuracy and surface precision for installation need to be changed. In this type of optical recording/reproducing device, where the conditions for setting the positioning surface on the body are particularly severe, the precision of the setting is substantially reduced, and the number of positioning surfaces on the housing can be reduced, so the overall structure of the device is improved. This makes it easier to process, improves workability, and lowers the cost.

In the above embodiment, the first lens (9D is a flat surface).
Although the convex lens and the second lens ω are constructed with a concave-plane lens, as shown in Fig. 5, it is also possible to combine a plane-concave lens and a convex-plane lens. Left. However, in this case, in order to function as a condensing lens as in the example shown in FIG. be.

n114 < nts
・・・・・・・・・・・・・・・・・・ (4)
Furthermore, as another example of application, if you want to make the synthetic optical member function as a light beam enlarger, the one shown in Fig. 4 may be
u < n92 *nu4 for the one in Figure 5>
Each refractive index may be set so as to satisfy the relationship nss.

In addition, in the above embodiment, the radius of curvature R of all rocks is
et and RH are made completely equal, but if the adhesive used to join both curved surfaces is selected appropriately, even if there is a slight difference in both radii, the gap based on this difference can be filled with the above adhesive without causing any practical problems. It may be applicable in some cases.

The following will explain what should be considered regarding the relationship between the refractive index of the convex lens (2) and its adjacent optical member (4101).In other words, the refractive index of the polarizing beam splitter (4) explained in the example of FIG. It is desirable that n4 be set equal to the refractive index n91 of the first lens all, and that the refractive index nlo of the half prism 02 be equal to the refractive index n92 of the second lens (decoy).

This is because the refractive index is constant before and after the interface between each optical member, so the light flux does not undergo unnecessary reflection at this interface, which has the advantage of reducing the amount of attenuation of the light flux.

〔Effect of the invention〕

As described below, the present invention includes a predetermined first lens having a flat surface and a convex surface, and a concave surface having a refractive index different from that of the first lens, the flat surface and the convex surface having approximately the same radius of curvature. By joining both curved surfaces of lens 2 and 2 to form a composite optical member, and joining this to other optical members, the integration of optical members can be applied over a wider range, and the accuracy of the equipment can be improved. This substantially reduces the need for positioning surfaces on the casing, simplifies the overall structure of the device, improves workability, and lowers the cost.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an optical recording/reproducing device according to an embodiment of the present invention, FIG. 2 is a perspective view showing details of the synthetic optical member shown in FIG. 1, and FIG. FIG. 4 is a cross-sectional view of the main optical path section of FIG. 1 viewed from the Z direction, and FIG. FIG. 6 is a perspective view showing a conventional optical recording/reproducing apparatus, and FIG. 7 is an optical path diagram showing a part of the optical path shown in FIG. 6. In the figure, (1) is a semiconductor laser, (8) is an information carrier, ◇υαJ is a two-split photodetector, ■ is a synthetic optical member, ■ is a first lens, and ■ is a second lens. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] A plurality of optical members each having a flat light input/output surface are integrated by joining adjacent light input/output surfaces to each other,
In an optical recording and reproducing device that is installed on an optical path between a light source, an information carrier, and a photodetector to record and reproduce information, at least one of the optical members is configured such that one of the light input and output surfaces is flat and the other is a convex surface. The first lens formed respectively has a refractive index different from the refractive index of the first lens, and one of the light entrance and exit surfaces has a flat surface and the other has a radius of curvature that is approximately equal to the convex surface of the first lens. An optical recording/reproducing device characterized in that the optical recording/reproducing device is a composite optical member including second lenses formed on concave surfaces joined to the convex surface, respectively.