JPS61250855A - Detector of optical information signal - Google Patents

Abstract

PURPOSE:To attain stable signal detection by irradiating an irradiated laser light from a semiconductor laser onto an information recording medium via an objective lens and using a condensor lens arranged at the outer circumferential side of an objective lens so as to collect a diffracted light reflected and diffracted from the information recording medium thereby detecting the signal. CONSTITUTION:An optical disc 1 is driven by a spindle motor and provided with a recording track comprising spiral or concentric pit string and an optical pickup 2 detects a signal. In the optical pickup 2, the laser light irradiated from a semiconductor laser 3 in the direction A is irradiated as a fine spot on the optical disc 1, its reflected light is diffracted by the pit on the optical disc 1 and made incident in the semiconductor laser 3 as a returned light via an objective lens 4. The output of the semiconductor laser 3 changes according to the change in the returned luminous amount and detected by a photodetector 5. The reflected light subject to difraction by the pit on the optical disc 1 is irradated to the outside of the incident light into the optical disc 1, collected by a condensor lens 7 and detected by photodetectors 8,9.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an optical information signal detection device.

(Prior Art) In an optical disc device, an optical disc is rotated by a spindle motor, and an optical pickup optically detects a signal from a recording track consisting of a spiral or concentric pit row on the optical disc. The optical pickup moves in the radial direction of the optical disc to track recording tracks on the optical disc. Tracking servo is also performed by detecting the tracking error and moving the optical pickup to eliminate it. There are various types of optical pickups, and signals due to pit rows and 1~ratkink errors are detected by various methods.

(Problems to be Solved by the Invention) Various methods have been used to detect the signal due to the 1-pitch sequence and the 1-hertz kink error, but all methods have problems with stability.

(Means for Solving the Problems) The present invention irradiates an information recording carrier with a laser beam emitted from a semiconductor laser through an objective lens, and transmits the diffracted light reflected and diffracted by the information recording carrier through the objective lens. The signal is detected by condensing light using a condensing lens placed on the outer periphery of the sensor, and the signal can be detected stably.

(Example) FIG. 1 shows an embodiment of the invention.

This embodiment is an example in which a signal is detected from an information recording medium 1 made of an optical disc in an optical disc device. The optical disk 1 is provided with a recording track consisting of a spiral or concentric pit row, is rotationally driven by a spindle motor, and a signal is detected by an optical pickup 2. The optical pickup 2 is moved in the radial direction of the optical disc 1 by a device (not shown) to track the recording track on the optical disc 1, and may be of either a slide type or a swing arm type. In this optical pickup 2, the laser beam emitted from the semiconductor laser 3 in the direction A is irradiated onto the optical disk 1 as a minute spot through the objective lens 4, and the reflected light is diffracted by the pits on the optical disk 1. objective lens 4
The light returns to the semiconductor laser 3 via the light source and enters the semiconductor laser 3 as a return light. The output of the semiconductor laser 3 changes in response to changes in the amount of returned light, and this is detected by the photodetector 5. High frequency (RF)
) The detection circuit 6 detects a high frequency signal caused by a pit on the optical disk 1 from the output signal of the photodetector 5.

Further, the reflected light that has been diffracted by the pits on the optical disc 1 is emitted (reflected) outward from the incident light on the optical disc 1 as shown by arrow B, and is focused by the condensing lens 7 and sent to the photodetectors 9 and 10. Detected by

The photodetectors 8 and 9 are arranged outside the circular photodetector 5 as shown in FIG. It is configured in an arc shape that is symmetrical about orthogonal axes. As shown in FIG. 3, the condenser lens 7 is made of a plastic lens or the like and is integrally formed with the objective lens 4, and is formed into an annular shape or a shape corresponding to the photodetectors 8 and 9. The output signals of the photodetectors 8 and 9 are inputted to the subtraction circuit 12 via amplifiers 10 and 11, and the difference between them is obtained as a tracking error signal, and this tracking error signal causes the optical pickup 2 to track the recording track using a device (not shown). Tracking servo is performed by moving so that there is no deviation.

In this embodiment, if the condenser lens 7 is placed at a position 7A behind the objective lens 4, as shown in FIG. By arranging it on the outer peripheral side of the objective lens 4, this problem does not occur and the diffracted light can be efficiently focused. Further, when the objective lens 4 is moved in the optical axis direction by the focus servo system, the condenser lens 7 is moved in accordance with this movement to perform focus servo.

In the above embodiment, the scoop method is adopted in which the output of the semiconductor laser 3 is detected by the photodetector 5 to detect a signal due to the pit, but FIG. An example is shown below. In this embodiment, in the above embodiment, the output signals of the amplifiers to, 1.1 are added by the adder circuit 13, and the RF multiplied signal by the pit is detected, and APC (Aut.

A power control circuit 14 controls the drive current of the semiconductor laser 3 based on the output signal of the photodetector 5 to keep the amount of light output from the semiconductor laser 3 constant.

(Effects of the Invention) As described above, according to the present invention, the laser beam emitted from the semiconductor laser is irradiated onto the information recording carrier through the objective lens, and the diffracted light reflected and diffracted by the information recording carrier is reflected and diffracted by the objective lens. Since the signal is detected by condensing the light with the condensing lens arranged on the outer circumferential side of the condenser lens, the signal can be detected stably.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing one embodiment of the present invention, Fig. 2 is a plan view showing a photodetector of the same embodiment, Fig. 3 is a cross-sectional view showing a lens of the same embodiment, and Fig. 4 is the same. FIG. 5, which is a diagram for explaining the condensing lens of the embodiment, is a schematic diagram showing another embodiment of the present invention. 1... Optical disk, 3... Semiconductor laser, 4
...Objective lens, 5,8.9...Photodetector, 7
····Condenser lens. Procedural amendment dated July 1, 1985 1, Case indication 1985 Patent Application No. 92961 2, Name of the invention Optical information signal detection device 3, Person making the amendment Relationship to the case Patent applicant name (223) ) Sankyo Seiki Seisakusho Co., Ltd. 4,
Agent Address: 4-5-4 Kyodo, Setagaya-ku, Tokyo "
Column 6 of ``Detailed Description of the Invention'' Contents of Correction (1) ``In a simplified optical pickup'' is inserted at the beginning of line 7 on page 2 of the specification.

Claims (1)

[Claims] Laser light emitted from a semiconductor laser is irradiated onto an information recording carrier through an objective lens, and the diffracted light reflected and diffracted by the information recording carrier is focused by a condensing lens disposed on the outer circumferential side of the objective lens to generate a signal. An optical information signal detection device configured to detect.