JPS6260141A - Reflective optical disk reader - Google Patents

Abstract

PURPOSE:To improve the degree of freedom for distribution of an optical system by turning a half mirror which lead the reflected light to the direction different from an incident optical path round a focusing optical path together with a light emitting means and a detecting means. CONSTITUTION:The reflected light traces back an incident optical path and returns to a half mirror 5 from an optical disk 1 and about half of the reflected light transmits the mirror 5 and reaches a photodetector 20. Here a tracking error signal is obtained by calculating the difference between the sums of output signals of photodiodes P1 and P2 and photodiodes P3 and P4 of the detector 20. In this case, the coincidence is required between the tangential direction DS of a track on the disk 1 and the dividing direction between the diodes P1/P2 and P3/P4. In this constitution, the mirror 5 is turned by an angle theta from the horizontal position where a semiconductor laser 3 is set together with said laser 3. Thus it is possible to turn the radius direction CS of the disk 1 and the direction RS of a focusing optical path can be turned by the angle theta from the 45 deg. positional relation. As a result, the free relationship is secured between the disk 1 and the focusing optical path.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Industrial Application Field] The present invention relates to a reflective optical disc reading device, and more specifically, the present invention relates to a reflective optical disc reading device, and more specifically, by detecting reflected light from a reflective optical disc with a photodetector, a 74- The present invention relates to a reflective optical disc reader configured to detect a dregs error signal and a tracking error signal.

[Prior Art] Conventionally, in this type of reflective optical disc reading device, the optical disc is illuminated with a 11 beam, the reflected light is made into a convergent light by a collimating lens, and then enters a half mirror to form the incident light. It separates the optical path from the optical path and generates astigmatism.
By detecting this with a photodetector, the focus error signal is increased by one. In addition, in addition to the focus error signal, a reflective optical disc reader requires a dragging error signal, which is detected using the photodetector described above by utilizing the diffraction of light by the edges of the pits of the optical disc. Things are also known.

FIG. 6 is an explanatory diagram showing the configuration of an optical system for detecting such focus error signals and tracking error signals. As shown in the figure, the laser beam output from the semiconductor relay LS passes through a half mirror 11m and a total reflection mirror Fm.
After being reflected by the optical disc Od, the optical disc Od
The light is focused on the top. The reflected light from the optical disk Qd follows the above-mentioned optical path in reverse, but a part of the reflected light passes through the half mirror 1.
m, passes through the concave lens C1, and reaches the photodetector Dt. Since the anti-01 light from the optical disk ○d is converged by the collimating lens, it is half mirror 1-1.
Astigmatism occurs when passing through n. When the focus is not accurately taken, both axes of an elliptical light spot generated on the photodetector Dt are in the direction of arrows C and B in FIG. 6. Therefore,
The photodetector Dt is constituted by four parts divided from four photodiodes, etc., and the division direction is the same as above A and B.
If configured to rotate by 45 degrees with respect to the direction, the focus shift (focus error signal FE) can be detected as the difference between the sum signals of the diagonals using the output signals from the four parts. On the other hand, tracking error signal MTE
is detected as the difference between the sum signals from two adjacent parts of the photodetector □t by the so-called power field method, which uses the diffraction of light by the edges of pits on the optical disk, for example, by the push-pull method. be.

[Problems to be solved by the invention] However, in such reflective optical disc reading devices,
Since the astigmatism is obtained by a half mirror, the directions of both axes of the elliptical light spot are fixed, and in order to obtain the racking error signal TE by 1q, a convergent optical path from the total reflection mirror to the photodetector is required. A problem has frequently arisen in that the direction (direction of arrow C in FIG. 6) must be set at 45 degrees with respect to the radial direction of the optical disc (direction of arrow C in FIG. 6). This is due to the characteristic of the power field method that in the light reflected from the optical disk, the tangential direction of the optical disk (arrow direction in FIG. 6) must coincide with the dividing direction of the photodetector.

Therefore, when using a half mirror to separate the incident light and the reflected light and to generate astigmatism, there is a problem that there is almost no degree of freedom in the arrangement of the optical system with respect to the optical disk. For this reason, it may be difficult to reduce the size of the reflection type optical disk reader when the number of stages is doubled.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and to provide a reflective optical disc reading device with increased flexibility in the arrangement of an optical system.

Structure of the Invention [Means for Solving the Problems] In order to achieve the above object, the present invention has the following structure as a means for solving the problems. That is, a light emitting means for illuminating a reflective optical disk on which information is recorded through a predetermined incident optical path, and a light emitting means disposed in the incident optical path to direct the light incident from the light emitting means to a predetermined area on the optical disk. an objective lens and a collimating lens that converge the reflected light from the optical disk and return it to the incident direction;
At least a portion of the reflected light that is disposed in the incident optical path and returns via the objective lens and the collimating lens,
a half mirror that guides the reflected light in a direction different from the incident optical path to form a converging optical path for the reflected light and produces astigmatism in the reflected light; It has a detection section that detects the intensity of light, and is arranged so that both axes of the elliptical light spot of the reflected light with reduced astigmatism are diagonal to the divided detection section, and the detection section a detection means for outputting at least a focus error signal and a tracking error signal based on the intensity of the reflected light detected by each of the reflective optical disc reading apparatuses for reading information recorded on the optical disc, This is a reflective optical disc reading device characterized in that a half mirror is configured by rotating a half mirror together with the light emitting means and the detecting means by a predetermined angle about the convergent optical path as an axis.

[Function] The reflective optical disc reading device of the present invention having the above configuration converts the light output from the light emitting means and reflected by the half mirror into parallel light using the collimating lens, and then condenses the light onto the optical disc using the objective lens. irradiate the optical disk, and return the reflected light from the optical disk to the half mirror as convergent light via the objective lens and collimating lens,
This half miter separates a part of the reflected light to avoid forming a convergent optical path and generates astigmatism, and the intensity of this reflected light is detected by a detection section divided into at least two or more parts, and the intensity of the reflected light is detected by a detection section divided into at least two or more parts. A detection means outputs a dwarf error signal and a tracking error signal. Moreover,
In the reflective optical disk reading device of the present invention, both axes of the elliptical light point of the reflected light that has astigmatism caused by the half mirror are arranged at diagonal corners of the divided detection section, and this relationship is Since the half mirror and the light emitting means are configured to rotate by a predetermined angle around the convergent optical path while maintaining the optical disk, there is no need to limit the converging optical path to the half direction of the optical disk at 45 degrees. Design of convergent optical path
It works to allow a high degree of freedom in placement.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a perspective view showing the configuration of an optical system of a q.1 type optical disk reading device as an embodiment of the present invention.

In this embodiment, the optical disc 1 is configured to be irradiated with a laser beam from the bottom surface to read recorded information.

As shown in the figure, the laser light (wavelength 780 nm) output from the semiconductor laser 3 as a light emitting means is transmitted through a half mirror.
5 and guided to a total reflection mirror 7. The laser beam is further reflected by the total reflection mirror 7, and enters the condenser lens 15 which houses the collitter 1 to the lens 9 and the objective lens 11 therein. Here, the semiconductor laser 3 is provided at a position where the laser light it outputs forms an angle .theta. with respect to the horizontal direction, and the half mirror 5 is also provided with an inclination angle corresponding to this angle.

The semiconductor laser 3 outputs laser light with a certain spread from the pn junction of GaAQAS, so after collimating this into parallel light with the collimating lens 9, it is passed through the objective lens 1.
1 to focus the light onto the optical disk 1. At this time, the focus of the laser beam is on the surface of the optical disc 1, so when there are no pits, the intensity of the reflected light returning to the objective lens 11 from the optical disc 1 is high, but when there are pits, the intensity of the reflected light returning to the objective lens 11 is high. The incident light is diffracted and the intensity of the reflected light returning to the objective lens 11 is small.

The reflected light is reflected by the objective lens 11. The convergent light passes through the collitter 1 to the lens 9 and returns to the half mirror 5 from the total reflection mirror 7 by retracing the entrance optical path.

The half mirror 5 reflects about 1/2 of the incident light toward the semiconductor laser 3, but transmits the rest. At this time, the transmitted convergent light is directed in the direction of the axis of the half mirror 5, as shown by the arrow A in Figure 1.
s direction).

The convergent light that has been transmitted through the half mirror 5 and has astigmatism passes through the concave lens 17 and reaches the photodetector 20 . Photodetector 2
0 is the four photodiodes PI.

P2. P3. P4, and in terms of shape, it is divided into approximately four equal parts around the optical axis of the convergent light.

The directions of this division are a direction rotated by 45 degrees with respect to the direction in which astigmatism occurs (direction of arrow As), and a direction perpendicular thereto. As a result, when the optical disk 1 moves away from the objective lens 11, as shown in FIG. 2(A), the long sleeve of the elliptical light spot in the convergent light coincides with the direction of the diagonal photodiodes PI and P3, On the other hand, when the optical disc 1 approaches, as shown in FIG. 2(b), its long sleeve is connected to another diagonal photodiode P2. It corresponds to the direction of P4. Therefore, as shown in FIG. 3, the sum signal of the respective output signals output from the diagonal photodiodes PI, P3, and P2 to P4 is added to the paralysis device ADD1. ADD2, and the difference between the sum signals is sent to the differential amplifier DF.The output signal becomes the focus error signal "E", so the cylindrical coil ( (not shown) can be applied to a known focus servo, such as one controlled by the focus error signal FE.

On the other hand, the tracking error signal TE is detected by the adjacent photodiodes pl, p2, and P3 of the photodetector 20.
．． It is obtained by taking the difference between the sum signals of the respective output signals output by P4 (FIG. 4). At this time, optical disc 1
In the optical system, the tangential direction of the upper track (direction of arrow DS in Figure 1) connects photodiodes P1 and P2 and P3 and P.
It must match the direction that divides 4. In this embodiment, as described above, the laser beam output from the semiconductor laser 3 forms an angle θ with respect to the horizontal direction, that is, the half mirror 5 is used together with the semiconductor laser 3, with the above-mentioned convergent optical path as the axis. The semiconductor laser 3 is rotated at an angle θ from the horizontal position in which it is normally installed. As a result, the radial direction of the optical disk 1 (arrow direction CS in FIG. 1) and the direction of the convergent optical path (arrow direction CS) 1 (arrow direction R5 direction) is not limited to 45 degrees, and from the positional relationship of 45 degrees, the above angle θ
can take a rotated position. optical disc 1
FIG. 5 shows the direction of the convergent optical path for θ-0° and θ-45°.

As explained above, in the reflective optical disc reading device of this embodiment, the relationship between the optical disc 1 and the convergence optical path of the reflected light for reading the optical disc 1 can be freely designed. Therefore, it becomes easy to downsize the anti-OrJ type optical disc reading device. Further, since the separation of the optical paths and the generation of astigmatism are performed by a single half mirror 5, effects such as a reduction in the number of parts, miniaturization of the optical system, and improvement in reliability are also obtained.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment in any way, and can be applied to any video disc player 17, digital audio disc player, etc. It goes without saying that the invention can be implemented in various ways without departing from the scope of the invention.

Effects of the Invention As described in detail below, the reflective optical disc reading device of the present invention uses a power field including a push-pull method using diffraction of pits to detect a focus error signal due to astigmatism caused by a half mirror. The relative position of the reflective optical disk and the optical system can be freely changed by changing the rotation angle of the half mirror, while the optical system is configured to detect the tracking error signal. This has the excellent effect of increasing the degree of freedom of As a result, it has become easier to downsize the device.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an optical system of a reflective optical disk reading device as an embodiment of the present invention, and FIG. 2 (A>, (
B) is an explanatory diagram showing the appearance of an elliptical light spot due to astigmatism, FIG. 3 is a configuration diagram of a circuit that outputs a focus error signal eFE, and FIG. 4 is a configuration diagram of a circuit that outputs a tracking error signal TE. FIG. 5 is an explanatory diagram showing the relative positional relationship between the optical disk and the optical system, and FIG. 6 is a perspective view showing the configuration of a conventional optical system.

Claims (1)

[Scope of Claims] 1. A light emitting means for illuminating a reflective optical disc on which information is recorded through a predetermined incident optical path; an objective lens and a collimating lens that converge light onto a predetermined area on the optical disk and return the reflected light from the optical disk to the incident direction; At least a portion of the reflected light that comes
a half mirror that guides the reflected light in a direction different from the incident optical path to form a converging optical path for the reflected light and produces astigmatism in the reflected light; It has a detecting section for detecting, and is arranged so that both axes of the elliptical light spot of the reflected light with the astigmatism are located diagonally to the divided detecting section, and each of the detecting sections detects the a detection means for outputting at least a focus error signal and a tracking error signal based on the intensity of the reflected light; and a reflective optical disc reading device for reading information written on the optical disc, wherein the half mirror is connected to the A reflective optical disc reading device, characterized in that the light emitting means and the detecting means are rotated by a predetermined angle about the convergent optical path as an axis.