JPH0452810Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical record playback device that uses an optical system to faithfully and non-contactly play back records that were conventionally played using a needle-type cartridge.

In an optical record playback device, the light reflected from the sound groove wall of the record is received by the light receiving surface of the photodetector to form a playback signal. It is desirable to always form an image of a constant size regardless of the size of the image. and,
In order to satisfy this requirement, it is desirable to always focus the incident light on the sound groove wall surface, and furthermore, the modulation of the sound groove wall surface causes the reflected light to pass through various reflection paths by changing the angle between the light reflecting surface and the incident optical axis. It is required that the light be received at the same distance. Furthermore, although the light-receiving surface of the photodetector is formed of a material such as silicon, it is technically difficult to form such a material into a curved surface, so it is desirable to be able to form a planar surface.

The present invention provides a device that satisfies these conditions, and will be explained below using examples.

As shown in FIG. 1, incident lights 2, 2 from light sources 1, 1 such as laser diodes are made into parallel rays by lenses 3, 3, and then converged by converging lenses 4, 4, and then sent to half mirrors 5, 5. Via Vinyl 6
It is incident perpendicularly to the sound groove wall surfaces 6 ₁ , 6 ₁ . Then, the reflected light 2 ₁ , 2 ₁ reflected by the sound groove wall surfaces 6 ₁ , 6 ₁
is reflected by the half mirrors 5, 5 and received by the light receiving surfaces 7 ₁ , 7 ₁ of the photodetectors 7, 7.

The pair of optical pickups 8, 8 provided corresponding to the sound groove wall surfaces ₆₁ , ₆₁ are such that the incident light always remains in the sound groove when the sound groove wall surfaces ₆₁ , ₆₁ are displaced in the direction of the arrow shown in the figure. The focus is independently controlled by a control means (not shown) so as to focus on the wall surfaces 6 ₁ and 6 ₁ .

FIG. 2 shows the arrangement relationship between the half mirror 5 and the light-receiving surface 7 ₁ of the photodetector 7 and their shapes. The reflective surface of the half mirror 5 is the sound groove wall surface 6 ₁ which is the focus of the incident light 2. It has a semi-circular vertical side surface shape including a light reflection point 9, which is parallel to the sound groove wall surface ₆₁ , and whose rotation axis is a straight line that intersects with the rotation axis of the record 6, and the bottom surface of this semi-circular vertical shape. A semi-doughnut-shaped light receiving surface ₇₁ is located on a plane parallel to . In addition, 10
indicates the optical axis of the converging lens 4.

Here, FIG. 3 is a view of FIG. ₁ viewed from above, and FIG. ₂₁ is reflected at the center of the half mirror 5, and an image 11 shown by the solid line in _FIG .
form a. Note that if the focus of the incident light 2 is not controlled with respect to the displacement of the sound groove wall surface 6 ₁ in the direction of the arrow described above, the size of the image formed on the light receiving surface 7 ₁ will be the same as that of the images 11a' and 11a'' shown by broken lines. However, in the present invention, as described later, a focus control signal is formed and the focus is controlled, so there is no change in the image due to the displacement of the sound groove wall surface _{61.Furthermore} , the actual sound groove wall surface 6 ₁ is shown in Figure 3b,
Since the angle between the light reflecting surface of the sound groove wall surface 6 ₁ and the incident optical axis 10 changes as shown in c, the reflection path of the reflected light 2 ₁ changes according to this angle change, and the light receiving surface The position of the image formed on 7 ₁ is displaced as shown in FIG. 4 as images 11b and 11c corresponding to FIGS. Since the reflected light 2 ₁ has a reflective surface with a specific relationship to
is equidistant from the light receiving surface 7 ₁ regardless of its reflection path.
There is no change in the size of the image due to differences in the reflection path.

By making the incident light incident on the sound groove wall at the required angle, the paths of the incident light and reflected light are completely separated, and the reflected light is directly received by the light receiving surface of the photodetector without going through a half mirror. Conventionally, devices have been proposed that do this, but such devices require a light-receiving surface to have a curved shape.

The light-receiving surface 7 ₁ is divided into a first region 12 that receives light from the center of the image formed on the surface, and a second region 13 that receives light from the edges excluding the center of the image. As shown in FIG. 4, the first area is an area sandwiched by boundary lines l ₃ and l ₄ that are equidistant from the upper and lower long sides l ₁ and l ₂ of the light-receiving surface 7 ₁ , respectively, and the inside thereof is a boundary line. Divided into two by line _l5 , divided area 12a, 1
On the other hand, the second region 13 is formed from two divided regions 13c and 13d sandwiched by corresponding long sides l ₁ and l ₂ and boundaries l ₃ and l ₄ , respectively. The amounts of light Sa, Sb, Sc, and Sd received by 12a, 12b, 13c, and 13d are detected.

Each region 12 forming the first region 12
Difference signal (Sa-
The degree of modulation of the sound groove wall surface ₆₁ is detected from Sb) to form an audio signal, and in order to obtain the above-mentioned focus control signal, each of the areas 12a and 12b receives the light of the amount of light received by the first area 12. The sum signal (Sa+Sb) of the amounts Sa and Sb and the sum signal (Sc
+Sd) is formed. The ratio of the sum signal (Sa + Sb) and the sum signal (Sc + Sd) changes according to the change in the image size due to the focal shift of the incident light, so the first
By using the amount of light received in the area 12 and the amount of light received in the second area 13, and controlling the control means of the optical pickups 8, 8 so that the ratio of the two is always constant, the focus of the incident light 2 can be adjusted. It can always be tied on the sound groove wall surface ₆₁ .

As described above, according to the present application, the light-receiving surface of the photodetector can not only receive reflected light passing through various reflection paths at equal distances, but also have a planar shape. But it's very advantageous.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical record reproducing device according to an embodiment of the present invention, FIG. 2 is a perspective view of a half mirror and a photodetector used in the optical record reproducing device, and FIGS. The figures each show an explanatory diagram of the operation of the optical record reproducing apparatus. 2, 2...Incoming light, 2 ₁ , 2 ₁ ...Reflected light, 4,
4...Converging lens, 6...Record, 6 ₁ , 6 ₁
... Sound groove wall surface, 7, 7 ... Photodetector, 7 ₁ , 7 ₁ ...
... Light receiving surface, 11a, 11a', 11a', 11b, 1
1c...image, 12...first area, 13...second
area, 13c, 13b... divided areas of the second area.

Claims (1)

[Claims for Utility Model Registration] The laser beam transmitted through the half mirror is focused to form a minute spot on the sound groove wall surface of the record, is reflected on the sound groove wall surface, and is further reflected on the reflective surface of the half mirror. This is an optical record playback device that forms a playback signal by receiving reflected light on a light-receiving surface of a photodetector and forming an image of a certain size on the light-receiving surface, the central axis of which is the half mirror. Assuming an arbitrary cone that is perpendicular to the optical axis of the laser beam that passes through the disc, substantially intersects with the minute spot, and further intersects with the rotation axis of the record, the reflective surface of the half mirror is on the side surface of the cone. arranged and has a curved surface that matches the side surface of the arranged part, such that the light-receiving surface of the photodetector is arranged on the bottom surface of the cone and has a flat surface that matches the bottom surface of the arranged part. An optical record playback device characterized by the following configurations.