JPH04206048A - Optical head - Google Patents

Abstract

PURPOSE:To form a compact, thin optical head by providing a concave mirror having a filter so that the light from a semiconductor laser is reflected in the direction of about 90 degrees with respect to the emitting direction of the light and a spot is formed on a light recording medium. CONSTITUTION:The shape of a concave mirror 2 has a spheroid surface or a curved surface which is approximate to the spheroid so that the light emitted from a semiconductor laser 1 is reflected in the direction of about 90 degrees and the focal point is focused on a light recording medium 5. The mirror 2 is formed of glass or plastic material. An optical filter 3 is formed on the surface of the concave mirror 2. A part of the light emitted from the semiconductor laser 1 is reflected, and a part of the remaining light is transmitted. A photodetector 4 is formed as a unitary body with the concave mirror 2. The light is modulated in amount of light with pits formed in the light recording medium 5 and reflected. The light transmitted through the concave mirror 2 is detected. In this way both operations of a rise-up mirror and an objective lens are performed with one concave mirror 2. Thus, the number of optical parts is decreased, and the optical head can be made compact and thin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical head used for recording and reproducing an optical recording medium.

2. Description of the Related Art In recent years, optical recording media have attracted attention as large-capacity memories, but the optical heads used for recording and reproducing them are also small and compact.
There has been a demand for thinner products, and various improvements have been made.

A conventional optical head will be explained below.

FIG. 3 shows a conventional optical head, with FIG. 3(a) being a front view and FIG. 3(b) being a side sectional view. This optical head detects the phase difference between pit signals of the optical recording medium 17 and generates a focus control signal. Regarding the configuration of this optical head, 11 is a semiconductor laser, and 16 is a half mirror that branches light emitted from the semiconductor laser 11 into an objective lens 15 and a light receiving element 14. half mirror
The laser beam separated by 16 enters the rising mirror 13 and is focused on the optical recording medium 17 through the objective lens 15. The reflected light carrying information about the pits of the optical recording medium 17 passes through the objective lens 15, the rising mirror 13, and the half mirror 16 again, and is guided to the light receiving element 14. The light receiving element 14 separates and detects a data signal and a temporal phase difference signal used for focus and tracking control from the pit signal of the optical recording medium 17.

However, in the conventional configuration described above, the objective lens 15 must be placed above the mirror 13 to focus the light onto the optical recording medium 17, which creates extra space.
There has been a problem in that it is difficult to realize a thinner optical head.

The present invention solves the above-mentioned conventional problems, and is more compact and
The purpose is to provide a thin optical head.

Means for Solving the Problems In order to achieve this object, the optical head of the present invention is installed so as to reflect light in a direction approximately 90 degrees with respect to the emission direction of a semiconductor laser and further to form a spot on an optical recording medium. a concave mirror; a filter formed to reflect part of the light incident on the concave mirror and transmit the remaining light; and a filter configured to detect the light reflected from the optical recording medium and transmitted through the concave mirror. The light-receiving element is provided with a light-receiving element.

Function: With this configuration, a single concave mirror serves as both the raising mirror and the objective lens, making it possible to reduce the number of optical components and make the optical head smaller and thinner.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an optical head according to a first embodiment of the present invention, in which 1 is a semiconductor laser, and 2 is a concave mirror that reflects the light emitted from the semiconductor laser 1 in a 90 degree direction and further emits light. The shape of the recording medium 5 is an ellipsoid of revolution or a curved surface similar to the ellipsoid so as to connect unfocused points on the recording medium 5, and is made of glass or plastic material. Reference numeral 3 denotes an optical filter formed on the surface of the concave mirror 2, which has the function of reflecting part of the light emitted from the semiconductor laser 1 and transmitting the remaining part. Reference numeral 4 denotes a light receiving element, which is formed integrally with the concave mirror 2 and is for detecting the light that is modulated and reflected in the amount of light by the focus formed on the optical recording medium 5, and further transmitted through the concave mirror 2. It consists of a split photodetector.

In the optical head configured as described above, the light incident on the light receiving element 4 is divided into two parts: the light that is emitted from the semiconductor laser 1 and directly transmitted through the concave mirror 2; The light that is modulated in light amount by the pit and reflected is incident on the concave mirror 2 again, and both of the transmitted light are detected. The former includes only DC components, and the latter includes AC components due to pit modulation. However, in the optical head of this embodiment, by detecting both the focus and tracking error signals by detecting the temporal phase difference, it is possible to detect both the data and the servo error signals using only their alternating current components. , the influence of the DC component is removed.

FIG. 2 is a block diagram of an optical head according to a second embodiment of the present invention, in which 1 is a semiconductor laser, 2 is a concave mirror, 3 is a filter, 4 is a light receiving element, and 5 is an optical recording medium. The operation is similar to the first embodiment. In the second embodiment, a part of the multi-divided photodetector of the light receiving element 4 is used as a light receiving section 6,
The concave mirror 2 is provided with a lens section 7 for monitoring the amount of diverging light emitted from the semiconductor laser 1 and for guiding a part of the light emitted from the semiconductor laser 1 to the light receiving section 6 on the outer periphery of the concave mirror 2. are doing. Further, the concave mirror 2 and the lens portion 7 are integrally formed, and no extra optical parts are required. With this configuration, the output power of the semiconductor laser 1 can be monitored using the same number of parts as in the first embodiment, and a high-performance optical head can be realized.

In this embodiment, the lens portion 7 has a convex surface, but it may have a flat surface, a concave surface, or any other shape as long as it guides a portion of the light emitted from the semiconductor laser 1.

Effects of the Invention As described above, the present invention makes it possible to realize an optical head that is much smaller and thinner than the conventional one by using a concave mirror with a filter that reflects part of the light incident on the front surface and transmits the remaining light. It is.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an optical head in a first embodiment of the present invention. FIG. 2 is a configuration diagram of an optical head in a second embodiment of the present invention. 3a and 3b are a front view and a side sectional view of a conventional optical head. 1... Semiconductor laser, 2... Concave mirror,
3... Filter, 4... Light receiving element, 5
...... Optical recording medium, 6... Light receiving section, 7.
...Lens section. Name of agent: Patent attorney Haruaki Koba and two others Figure 2 Figure 3 (o) (b) /(

Claims (4)

[Claims] (1) A semiconductor laser, a concave mirror installed to reflect the light in a direction approximately 90 degrees to the emission direction of the semiconductor laser and further form a spot on the optical recording medium, and a portion of the light incident on the concave mirror. An optical head comprising: a filter formed to reflect the remaining light and transmit the remaining light; and a light receiving element provided to detect the light reflected from the optical recording medium and transmitted through the concave mirror. (2) The optical head according to claim 1, wherein the concave mirror has a spheroidal surface or an approximate shape thereof. (3) A part of the light emitted from the semiconductor laser is transmitted through a part of the concave mirror or a part of the outer periphery of the concave mirror, and is made to enter the light receiving surface provided in the light receiving element for detecting the output power of the semiconductor laser. Claim 1 in which a flat or convex surface is provided on the
Or the optical head according to claim 2. (4) The optical head according to claim 3, wherein the concave mirror and the light receiving element are integrally formed.