JPH02195535A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate the need of a half mirror for separating a luminous flux for detecting a focusing error and a luminous flux for detecting a tracking error and to enhance the utilization efficiency of light by making the light shielding area of a light shielding plate a reflecting surface. CONSTITUTION:Light reflected on an information recording surface 11 reversely passes through a condensing lens 10 and enters the half mirror 9. Some quantity of the light is transmitted straight through the half mirror 9 and the remaining quantity of the light is bent at right angles. The bent returning light 13 is divided into four parts by the light shielding plate 1. The two parts thereof are transmitted straight and the other two parts are reflected. By respectively changing the direction of the transmitted light by a combination prism 6, the light is condensed on a four-division photodetector 8 by a convex lens 7 and th deviation of a distance between an optical head and the recording surface 11, that means, the focusing error, is detected from the positional deviation. Meanwhile, the reflected light is transmitted straight through the half mirror 9 and converged on a two-division photodetector 15 by a converging lens 14 so as to detect the positional deviation of a spot, that means, the tracking error. Thus, the half mirror is made needless and the focusing error is accurately detected.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention records and reproduces information using light. [Prior Art] In general, optical information recording and reproducing devices of type H are: In order to accurately and efficiently apply a light spot to the source medium, it is necessary to finely adjust the light spot.

For this reason, the apparatus requires a track error detection system for finely adjusting the positional deviation of the light spot, and a focus error detection system for finely adjusting the focus deviation of the light spot.

Conventionally, the method used is to separate the light reflected from the medium surface into signal detection light and error detection light, and then separate the error detection light into track error detection light using a half mirror.
The method was to separate the light into focus error detection light.

FIG. 3 shows the configuration of a conventional example. Parallel light 12 obtained from a semiconductor laser or the like (not shown) is changed in direction by a half mirror 9, travels backward through the condenser lens, and separates returned light 13 as the error detection light. The returned light 13 is turned into a light beam 19 for track error detection by a half mirror 17.
and a focus error detection light beam 18. Track error detection uses a so-called bush-pull method that utilizes diffracted light on the medium surface. Therefore, the track error detection light beam 19 is converged by the converging lens 14 and detected by the two-split photodetector 15.

On the other hand, the focus error detection light beam 18 is
In order to remove as much as possible the interference portion 5 of the diffracted light due to the pull method, more of the zero-order diffracted light component 4 is extracted through the light shielding plate 1b having the light shielding area 16, and the light path splitter 6. A focus error is detected by a four-split photodetector 8 via a convex lens 7.

FIG. 4 shows the above-mentioned light shielding plate 1b. The light shielding plate 1b is divided into four regions, each of which is divided into two transmissive regions 2 and two light shielding regions 16. Correspondingly, the return light 13 is
Most of the interference portion 5 is blocked, and a large amount of the zero-order diffracted light component 4 is transmitted.

The dotted line is the third-order diffracted light component.

[Problem to be solved by the invention]

The above-described conventional optical information recording and reproducing apparatus requires a half mirror to separate the light beam for tracking error detection and the light beam for focus error detection, which inevitably increases the number of parts.

In addition, in order to accurately detect focus errors, the transmission area is limited, but this requires a strong light beam for focus error detection, and a half mirror is used to convert the returned light into the focus error detection light beam and track error. The conventional method of separating the light beam into a detection light beam has the disadvantage that the light beam becomes weak.

[Means to solve the problem]

The optical information recording and reproducing apparatus of the present invention includes a half mirror that reflects parallel light in the direction of an information recording surface, and a half mirror that reflects parallel light in the direction of an information recording surface.
a condensing lens that condenses the reflected light from the information recording surface onto the information recording surface;
The return source sun-shaped beam reflected by the information recording surface and obtained via the condensing lens/half mirror is formed by two lines passing through the center of the optical axis in a plane perpendicular to the optical axis, with the optical axis as the center, Divide into four radial regions and create a diagonal set of 2
A light-shielding plate with a transmission region for the component and a light-shielding region for the remaining diagonal pair of two components is arranged symmetrically with the transmission region centered around the zero-order diffracted light component only, with ±-next-order prior light present. , and a light-shielding plate arranged such that the light-shielding region matches the third-order diffracted light component, and the light has been transmitted through the transmission region of the light-shielding plate.
An optical path splitter that splits each of the two sector-shaped luminous fluxes into different directions, and two
In an optical information recording/reproducing device comprising a convex lens that converges a light beam and two two-split photodetectors that detect the two light beams converged by the convex lens, the light shielding plate area of the light shielding plate is a reverse slope. , for the two fan-shaped beams reflected by the reflecting surface and obtained via the half mirror, a dividing line is formed at the adjacent vertices of the two fan-shaped beams narrowed by the converging lens, which narrows the beam diameter. An optical information recording/reproducing device characterized by adding a two-split photodetector arranged so that the photodetector passes through the two-split photodetector.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 2, parallel light 12 obtained from a semiconductor laser or the like (not shown) passes through a half mirror 9, and is condensed by a condenser lens 10 and irradiated onto an information recording surface 11. The light reflected on the information recording surface 11 passes through the condensing lens 10
Go in the opposite direction and enter Half Mirror 9. In the half mirror 9, a certain amount of the light is transmitted straight through, and the rest is bent at right angles. (Toward the lower right of the drawing) The bent return light 13 is divided into four parts by the light shielding plate 1.

Of these, two parts are transmitted straight through and the other two parts are reflected. The transmitted light is changed in direction by a combination prism 6 and condensed by a convex lens 7 onto a four-split photodetector 8.
1, a focusing error is detected. On the other hand, the reflected light passes straight through the half mirror 9 and is converged on the two-split photodetector 15 by the converging lens 14, where a spot positional shift, that is, a tracking error, is detected.

Next, the light shielding plate 1 will be explained with reference to FIG. The light shielding plate 1 is diagonally divided into four areas, and two sets facing each other at the midpoint have the same properties, and can be divided into two areas in terms of properties.

The purpose of dividing into four regions is to prevent the interference portion 5 between the zero-order diffraction light component 4 and the third-order diffraction light component used for tracking error detection in the Bush-Pull method from affecting focusing error detection. be. Therefore, the purpose can be achieved even if the area division method is not the division method shown in FIG. 1. The four areas are divided into a transmission area and a reflection area, and in this embodiment, the area where most of the interference portion used for tracking error detection falls is the reflection area, and only the zero-order diffracted light component 4 is placed in the reflection area. The affected area is made transparent.

〔Effect of the invention〕

As explained above, the present invention makes the light shielding area of the light shielding plate a reflective surface, thereby reducing the focus error detection light flux.
By eliminating the need for a half mirror for separating the light flux for tracking error detection and increasing light utilization efficiency, it is possible to secure a sufficient amount of light for focus error detection even if the angle of the transmitted light area of the light shielding plate is small. This has the effect of making it possible to obtain a stable focus error with less tracking error leakage by using the light beam from which the ±-next-next-next light component has been completely eliminated.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a light shielding plate in the present invention,
FIG. 2 is a basic configuration diagram of an embodiment of the present invention, FIG. 3 is a basic configuration diagram of an embodiment of the prior art, and FIG. 4 is a diagram showing an embodiment of a light shielding plate of the prior art. la, lb... Light shielding plate, 2... Transmission area, 3... Reflection area, 4... Zero-order diffraction light component, Death... interference part.

Claims (1)

[Claims] A device that records, plays, or only plays back information using optical means. It uses light reflected from the recording surface to detect track errors, which are misalignment of a light spot, and focus errors, which are misalignments of a light spot. In an optical information recording and reproducing device that performs detection, a light shielding plate having a reflective area and a transmitting area is used as means for separating the reflected light into a light beam for detecting the track error and a light beam for detecting the focus error. An optical information recording and reproducing device characterized by: