JPH02246025A - Optical recorder - Google Patents

Abstract

PURPOSE:To reduce optical elements and to drive an entire head optical part in focusing and tracking directions by allowing one hologram element to have a condensing function, a separating function and an astigmatism generating function for laser light. CONSTITUTION:A light beam emitted from a laser chip 13 arrives at the hologram element 14, where the light beam is condensed to irradiate the function film of a magneto-optical disk 5. The light beam reflected by the function film passes through the hologram element again and is diffracted in a direction different from a going direction for the second time, and it is guided to two photodetectors 15 and 16. At such a time, two diffracted light beams are allowed to have such a function that astigmatism, which is a focusing error signal, is generated, the focusing error signal is detected by the photodetector 16. Meanwhile, an electromagnetic coil 19 which generates a linear motion in a focusing direction and a tracking direction is attached to an optical unit and the coil itself is inserted into a magnetic gap consisting of a permanent magnet 20 and a yoke 21. Thus, the optical unit is made small in size and light in weight and the entire optical unit is driven in the focusing direction and the tracking direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording device. More specifically, the present invention relates to the structure of an optical head section of an optical recording device.

[Prior Art] FIG. 2 is a schematic diagram showing the main parts of a head of a magneto-optical recording device. The light emitted from the semiconductor laser 1 is converted into parallel light by a collimator lens 2, then its optical path is changed upward by a mirror 3, focused by a condenser lens 4, and irradiated onto a disk 5. The light reflected by the disk 5 returns along the optical path from which it came and is guided to a disk focus, track error detection system, and data detection system.

However, it is omitted in Fig. 2. FIG. 4 is a diagram showing details of the optical system. After passing through a collimator lens 2, the light emitted from the semiconductor laser 1 becomes parallel and enters a beam shaping prism 6. At this time, the laser enters the prism obliquely, so it is expanded in only one direction, and the elliptical beam is shaped into a perfect circle. This light passes through a prism, has its optical path changed upward by a flip-up mirror 3, and is then converted into an optical path by an objective lens 4.
The light is focused onto the disk 5. The reflected light containing information on the disk follows a reverse course through the objective lens 4 and flip-up mirror 3, and its optical path is converted by the beam splitter part 7 of the shaping prism and reaches the 1/2 wavelength plate 8. The 1/2 wavelength plate tilts the polarization direction of the light containing the information light read from the optical disk by 45 degrees, and guides the light to the polarizing beam splitter 9, which is the next analyzer. Here, the light that passes through the polarizing beam splitter 9 as it is becomes one of the differential outputs for detecting the tracking error signal by the push-pull method and for detecting the magneto-optical signal. Reference numeral 10 denotes a two-part photo sensor that converts the intensity of these information lights into electrical signals.

On the other hand, the light reflected by the polarizing beam splitter 9 enters an astigmatism generating optical system 11 that detects a focus error signal, and becomes the other differential output of the detection of the focus error signal and the magneto-optical signal. 12 detects these signals 4
It is a split photodetector.

[Problems to be Solved by the Invention] In such magneto-optical recording devices, the structure of the optical head is complex and the head has a large number of components, which increases the weight of the head, which poses a major obstacle to high-speed access. It has become. Furthermore, the large number of component parts of the head is disadvantageous in terms of cost, making it difficult to reduce the price. Furthermore, alignment of the optical system is time-consuming, which also leads to an increase in manufacturing costs.

In order to solve these problems, the present invention provides a mechanism capable of focusing and tracking the entire head by realizing a light and small optical head with a simple structure at a low cost.

[Means for Solving the Problems] The present invention provides a recording device using an optical recording medium, including a laser serving as a light source, condensing the light emitted from the laser onto the optical recording medium, and collecting light from the recording medium. A hologram optical element that branches reflected light and guides it onto a photosensor, and a photodetector that detects either or both of focusing and tracking error signals from the reflected light and reproduces a data signal. This is an optical recording device having a mechanism for simultaneously driving the entire optical head section in the focus direction and the track direction.

[Function] In the present invention, various functions of the optical system are multiplexed by using a hologram element, so the optical system can be simplified and lightweight. That is, by providing a single hologram element with a laser beam focusing function, a separating function, and an astigmatic function, the number of optical elements can be significantly reduced. Therefore, the entire head optical section can be driven in the focusing direction, tracking direction, and tracking direction.

[Example] FIG. 1 is a conceptual diagram showing the configuration of an optical head according to the present invention. The light emitted from the laser chip 13 reaches the hologram element 14, where it is focused and irradiated onto the functional film of the magneto-optical disk 5. The light reflected from the functional film passes through the hologram element again, is diffracted a second time in a different direction, and is guided to two photodetectors 15 and 16. At this time, since the two diffracted lights are functionalized to generate astigmatism which becomes a focus error signal, the photodetector 16 can detect the focus error. FIG. 3 is a plan view showing the arrangement of the laser chip 13 and photodetectors 15 and 16. Note that here, the photodetector 16 is divided into four parts for the astigmatism method.

In the push-pull method, the tracking signal can be detected by regarding the four divisions of the photodetector 16 as two vertical divisions and obtaining a difference signal. Alternatively, the photodetector 15 may be divided into two parts. Furthermore, in the sampling method, the sum signal of the photodetectors 15 and 16 may be extracted and the wobble bit signal may be reproduced to obtain a track error signal. Furthermore, it goes without saying that the layout of the photodetector changes depending on various focus and tracking error signal detection methods.

Now, the two diffracted lights are detected by the photodetector 15.1.
It passed through analyzer 17 and 18 before entering 6. This analyzer may be a plastic polarizing plate, the polarization directions of which are set in orthogonal directions. That is, by taking a difference signal between the optical signals entering the photodetectors 15 and 16, the data signal from the magneto-optical recording medium is reproduced. In addition, 2
4 schematically represents a laser light spot.

In this way, in the present invention, a hologram element capable of multiplexing light is provided with a function of condensing laser light and a function of dividing it to generate astigmatism, resulting in a significant reduction in the number of optical elements.

On the other hand, the above-mentioned optical unit is equipped with an electromagnetic coil 19 that generates linear motion in the focus direction and the track direction, and this coil itself is inserted into a magnetic gap made up of a permanent magnet 20 and a yoke 21. There is. That is, it can be considered that the optical unit itself is attached to the lens actuator instead of the conventional lens and objective lens of the actuator. Therefore, when a servo current fed back by the focus error signal and track error signal extracted from the optical unit is applied to the coil, the entire optical unit moves in the focus direction.
Driven in the track direction.

That is, according to the present invention, the entire head can be made up of only the part that conventionally drives the objective lens by taking advantage of the light weight of the hologram, and therefore it is possible to significantly downsize the head. In addition, 2 in the figure
2 is an optical unit and lead wires from a magnetic coil, and 23 is a bias magnetic field generating coil for a magneto-optical medium.

[Effects of the Invention] As described above, the present invention simplifies the optical head section of a magneto-optical recording device by using a hologram element and achieves a significant reduction in size and weight. Therefore, the entire optical unit can be driven in the focus direction and the track direction. It became possible to do so.

In other words, the present invention solves the problems of the size and weight of the head, which have been considered the biggest drawbacks of optical memory, so it is possible to achieve access speeds comparable to or even faster than hard disks, while at the same time reducing the size of the entire device. can also be achieved. Further, although the present invention has been described in detail using a magneto-optical recording device as an example, it goes without saying that it is applicable to various optical memory devices such as CDs, WOs, and others. Furthermore, even more interesting developments can be made by incorporating a preamplifier for signal reproduction along with the semiconductor laser and photodiode, or by using the lead wire from the optical unit in place of the leaf spring of the actuator.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the invention. FIG. 2 is a block diagram of a conventional optical head. FIG. 3 is a layout diagram of the laser and photodiode of the present invention. FIG. 4 is a layout diagram of conventional optical head components. Applicant: Seiko Epson Co., Ltd. Agent: Patent Attorney Kizo Suzuki and 1 other person: ES 口ε口 Figure 2

Claims (1)

[Claims] In a recording device using an optical recording medium, a laser serves as a light source, the light emitted from the laser is focused on the optical recording medium, and the light reflected from the recording medium is branched and guided onto a photosensor. The entire optical head section consisting of a hologram optical element and a photodetector for detecting either a focusing or tracking error signal or both from the reflected light and reproducing a data signal is simultaneously moved in the focusing direction. , and an optical recording device characterized by having a mechanism for driving in the track direction.