JP2723959B2 - Outgoing light inspection method for optical pickup - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emitted light inspection method for an optical pickup that inspects light emitted to an optical information recording medium through an objective lens.

2. Description of the Related Art Information is written / reproduced on / from various optical information recording media such as an optical disk, an optical card and an optical floppy disk by an optical pickup.

The general configuration of an optical pickup is shown in FIG. As shown in FIG. 5, a laser beam emitted from a laser diode 1 is coupled to a coupling lens 2.
After passing through a beam splitter (BS) 3 after being made into parallel light, the beam is made into convergent light by an objective lens 4 of an actuator section, and is irradiated in the form of a spot on the surface of an optical information recording medium such as an optical disk (not shown). You. The light reflective recording surface of the optical information recording medium is located at a position corresponding to the focal point 7 of the objective lens 4, and the light reflected by the light reflective recording surface of the optical information recording medium After being converted into parallel light at 4, the light is reflected by the beam splitter 3 and separated in a direction perpendicular to the outward path, and the separated light is received by a photodetector 5 disposed on the side of the beam splitter 3. . Then, recording / reproduction is performed based on a change in the amount of light or a change in the polarization state caused by the relative movement between the focal point 7 of the objective lens 4 and the recording surface.

By the way, inspection of the light output of such an optical pickup, that is, the light emitted to the optical information recording medium through the objective lens 4 is performed. Then, predetermined control operations such as laser power output control are performed based on the inspection result, for example, recording power setting and reproduction power setting are performed. In a general optical pickup inspection method, a light receiver is placed at a position indicated by reference numeral 6 or 6 'in FIG. 5 to perform the above-described inspection of light.

[Problems to be Solved by the Invention] However, if the optical system including the objective lens 4 is scratched, stained or adhered with dust due to environmental pollution or elapse of use time, as shown by reference numerals 8 and 9 in FIG. Scattered light will be generated. If the measurement of the emitted light is performed in a state where the scattered light is included, there arises a problem that the effective light power used for recording / reproducing is not measured. The optical power effective for recording / reproducing is the power of the convergent component converged on the focal point 7, and the other scattered light components due to the scattered lights 8, 9 are not used effectively for recording / reproducing.

In particular, when the optical system becomes dirty, the difference between the output power from the objective lens 4 and the effective light power becomes large. The contamination of the optical pickup occurs depending on the use time and the degree of contamination of the use environment. For example, when the optical disc system is used for 6 to 12 months in a class 1 million pollution environment, the optical pickup is used. The effective light power is reduced by about 30%, and the recording / reproducing function may be lost. Such a decline in functionality
This is a major problem in practical use of optical pickups.

Therefore, the present invention provides a method for inspecting an emitted light of an optical pickup, which can accurately measure an effective optical power used for recording / reproducing and can surely perform a subsequent control operation. The purpose is to do.

Means for Solving the Problems In order to achieve the above object, the present invention performs an inspection of light emitted to an optical information recording medium through an objective lens, and performs a predetermined control operation based on the inspection result. In the emitted light inspection method for an optical pickup, a light receiver is installed at a position where the cross-sectional diameter of the convergent light is smaller than 1/2 of the aperture diameter of the objective lens on the light emission side of the objective lens. Using a laser convergent light receiving element placed in the center of the and a scattered light receiving element placed around it,
By setting the diameter of the laser convergent light receiving element to a range that is equal to or smaller than 1/2 of the aperture diameter of the objective lens and larger than the convergent beam spot diameter, the light emitted from the objective lens, the objective lens And a scattered light component that converges on the converging point, and detects the scattered light component. From these detected components, the effective light power and the scattered light ratio of the light emitted from the objective lens are obtained.

Therefore, since the effective light power and the scattered light ratio of the light emitted from the objective lens are obtained, the true recording / reproducing function and the degree of contamination of the optical system at the present time are accurately detected therefrom, and the state of the optical pickup is determined. It is surely grasped.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of an optical pickup device for carrying out the present invention. As shown in FIG. 1, a laser beam emitted from a laser diode 1 is converted into a parallel beam by a coupling lens 2, passes through a beam splitter (BS) 3, and then converges by an objective lens 4 in an actuator section. The light is irradiated to the surface of an optical information recording medium such as an optical disk (not shown) in the form of a spot. The light reflective recording surface of the optical information recording medium is located at a position corresponding to the focal point 7 of the objective lens 4.
The light reflected on the light reflective recording surface of the optical information recording medium is
After being made parallel by the objective lens 4, it is reflected by the beam splitter 3 and separated in a direction perpendicular to the outward path, and the separated light is received by a photodetector 5 arranged on the side of the beam splitter 3. It is supposed to be. Then, recording / reproduction is performed based on a change in the amount of light or a change in the polarization state caused by the relative movement between the focal point 7 of the objective lens 4 and the recording surface.

When such an optical output of the optical pickup, that is, the inspection of the optical power emitted to the optical information recording medium through the objective lens 4 is performed, the light receiver 10 is installed on the light emission side of the objective lens 4. This light receiver 10 is an objective lens 4
Disposed before and after the converging point 7, it is specifically placed cross-sectional diameter of the converging light beam in the smaller position than half of the opening diameter d _L of the objective lens 4.

The light receiver 10 is provided with an element 10a which is disposed at the center and receives the laser condensed light beam, and an element which is disposed around the laser light condensed light receiving element 10a and receives scattered light other than the laser light condensed light. 10b.
The diameter d _A of the laser condensed light receiving element 10a is
Open less than half the diameter _{d L (d L / 2 ≧} d A) preferably is set to 1/10 or less _{(d L / 10 ≧ d A} ), and set to a value in the range of greater than converged beam spot diameter Have been. The diameter d _B of the scattered light receiving element 10b is the opening diameter d _L of the objective lens 4
Is set to 1 to 10 times.

Output signals A and B representing respective detection outputs from the laser condensed light receiving element 10a and the scattered light receiving element 10b.
Are applied to an adder 11, and an output signal (A + B) representing the operation result of the adder 11 and an output signal B representing a detection output from the scattered light receiving element 10b are applied to a divider 12. ing. The output signal representing the operation result of the divider 12 is B / (A + B).

Here, the signal A represents the effective optical power which is the laser power contributing to the focused spot, the signal B represents the optical power of the scattered light which is the laser power which does not contribute to the focused spot, and the signal (A + B) ) Indicates the total power of the light emitted from the objective lens 4, and the signal B / (A + B) indicates the power ratio of the scattered light to the output power from the objective lens 4.

Next, an embodiment of a method for inspecting an emitted light of an optical pickup according to the present invention using such an apparatus will be described.

First, FIG. 2 shows the result when the 51/4 inch write-once optical disc device RD-5040WL manufactured by Ricoh Co., Ltd. was left in a class 3 million polluted environment. As shown in FIG. 2, as the dirt advances, the output light power (A + B) and the effective light power A from the objective lens gradually decrease, and the scattered light power B increases on the contrary. After 12 weeks, the objective lens becomes finely stained, and some light is remarkably scattered. At this time, the amount of decrease in the output light power (A + B) from the objective lens is very small, but the amount of decrease in the effective light power A is quite large, and the amount of increase in the scattered light power B is also quite large.

On the other hand, FIGS. 3 and 4 respectively show a comparison of the recording ability between a clean optical pickup and a dirty optical pickup. In each of these diagrams, the ordinate represents the contrast amount of the recording pit. First, as shown in FIG. 3, looking at the contrast amount (vertical axis) of the recording pit with respect to the output light power (A + B) (horizontal axis) of the objective lens, the control of the recording pit changes depending on the presence or absence of dirt. It is understood that the recording ability of the soiled optical pickup is reduced.
However, as shown in FIG. 4, when looking at the contrast amount (vertical axis) of the recording pit with respect to the effective light power A (horizontal axis), almost the same recording contrast can be obtained regardless of the presence or absence of dirt. Recognize.

Therefore, in the present embodiment, the effective optical power of the light emitted from the objective lens 4 is obtained based on the detection output signal A from the laser condensed light receiving element 10a of the light receiver 10, and the detection output signal A and the scattering Light receiving element 10b
Power ratio B / (A + B) of the scattered light to the output light power of the objective lens 4 based on the detection output signal B from
Is required. That is, the laser light emitted from the objective lens 4 is detected separately from a convergent light component condensed on the converging point 7 of the objective lens 4 and other scattered light components. Thus, the effective light power and the scattered light ratio of the light emitted from the objective lens 4 can be obtained.

Then, the current recording performance of the optical pickup can be accurately obtained from the test result of the effective optical power A (see FIG. 4), and the test result of the optical pickup can be obtained from the test result of the scattered light ratio B / (A + B). The degree of contamination at the present time can be accurately obtained. By controlling the output of the laser power based on the results of these two inspections, or by judging the deterioration state of the optical pickup,
An accurate optical recording system is diagnosed.

Note that the scattered light ratio can also be calculated as B / A.

[Effects of the Invention] As described above, the present invention provides an optical pickup which inspects light emitted to an optical information recording medium through an objective lens and performs a predetermined control operation based on the inspection result. In the emitted light inspection method, a light receiver is installed at a position where the cross-sectional diameter of the convergent light on the light emission side of the objective lens is smaller than 1/2 of the aperture diameter of the objective lens, and is disposed at the center of the light receiver. Laser convergent light receiving element, and using the scattered light receiving element disposed around it, the diameter of the laser convergent light receiving element is less than 1/2 of the aperture diameter of the objective lens and the convergent beam spot diameter Is set to be larger, the light emitted from the objective lens is detected by being divided into a convergent light component converging at the converging point of the objective lens and other scattered light components, and these detected light components are detected. The effective light power and the scattered light ratio of the light emitted from the objective lens are obtained from the respective components, and the true recording / reproducing function at the present time is determined from the effective light power and the scattered light ratio of the light emitted from the objective lens. And the degree of dirt on the optical system is accurately detected, and the state of the optical pickup is surely grasped.
It is possible to accurately measure the effective optical power used for reproduction, to reliably perform the subsequent control operation, and to notify the user of an abnormal state before the recording / reproduction function of the optical pickup is lost. The reliability of the optical pickup can be improved by preventing the recorded contents from being destroyed or damaged.

[Brief description of the drawings]

FIG. 1 is an explanatory side view showing an example of an optical pickup for carrying out the present invention, FIG. 2 is a diagram showing a change in optical power when an optical disk device is left in a certain contaminated environment, FIGS. 3 and 4 are diagrams showing a comparison of recording performance between a clean optical pickup and a dirty optical pickup, and FIG. 5 is an explanatory side view showing a general optical pickup. 1 ... Laser diode, 4 ... Objective lens, 10 ...
Photodetector, 10a: Laser focused light receiving element, 10b: Scattered light receiving element.

Claims (1)

(57) [Claims] An inspection method for an emitted light of an optical pickup, wherein inspection of light emitted to an optical information recording medium through an objective lens is performed and a predetermined control operation is performed based on the inspection result. A light receiver is installed at a position where the cross-sectional diameter of the convergent light on the light emission side is smaller than 1/2 of the aperture diameter of the objective lens, and a laser convergent light receiving element arranged at the center of the light receiver, By using a scattered light receiving element disposed therearound, by setting the diameter of the laser convergent light receiving element to a range that is equal to or smaller than 1/2 of the aperture diameter of the objective lens and larger than the convergent beam spot diameter, The light emitted from the objective lens is detected by being divided into a convergent light component converging at the converging point of the objective lens and other scattered light components. Light emitted inspection method of an optical pickup is characterized in that so as to obtain an effective optical power and the scattered light ratio of the emitted light.