JP4100303B2 - Optical head evaluation method and apparatus - Google Patents

Description

The present invention relates to an apparatus for evaluating an optical head for reading and writing information on an optical disk type information storage medium, for example, a DVD (Digital Versatile Disk).

  In order to read information from an optical disk type high-density information storage medium and store information in this high-density information storage medium, an optical system capable of accurately irradiating light emitted from a light source to a target location is required. . Therefore, in particular, the objective lens of the optical system is required to have strict optical characteristics, and the objective lens must be inspected for aberrations and used with a desired characteristic. Furthermore, it is necessary to strictly adjust the attachment position of the objective lens.

  Therefore, as a method for inspecting and adjusting the objective lens, a method (diffractive interference method) in which aberration is detected by interference measurement and inspected and adjusted based on this is proposed (for example, see Patent Document 1). ). This diffraction interference method will be briefly described below with reference to FIG.

  FIG. 1 shows a schematic configuration of a conventional optical head inspection / adjustment apparatus using a diffraction interference method.

In FIG. 1, light 2 emitted from a light source 1 is converted into parallel light by a collimator lens 3 and enters an objective lens 4. The light emitted from the objective lens 4 enters the diffraction grating 5 while being condensed. From the diffraction grating 5, zero-order light and ± first-order light are generated. By adjusting the angle between the optical axes of the 0th order diffracted light and the + 1st order diffracted light, or the 0th order diffracted light and the −1st order diffracted light, the 0th order light and the + 1st order light, and the 0th order light and the −1st order light on the detection lens 6. Light overlaps and interference fringes occur. This pattern is received by the image receiving unit 7, analyzed by the signal processor 8 to detect aberrations, and displayed on the display unit 9. When the image receiving unit 7 receives an image, the image is formed by the imaging lens 10. An example of interference fringes obtained by the display unit 9 is shown in FIG. There are zero-order diffracted light, + 1st-order diffracted light and −1st-order diffracted light that are shifted by a certain distance, and interference fringes are formed in the overlapping portion. By analyzing the interference fringes, the wavefront aberration included in the light beam emitted from the objective lens 4 can be detected. Based on the detected wavefront aberration, the optical components such as the objective lens 4 are adjusted.
JP 2000-329648 A

  However, in the above conventional method, when the optical head is caused to emit light and is installed at a predetermined position with respect to the diffraction grating, there is a risk that the diffraction grating may be damaged because the temperature is raised by the collected light. There is a problem. This will be described with reference to FIGS.

  In FIG. 1, the light emitted from the objective lens 4 of the optical head 11 is condensed in a small area on the diffraction grating as shown in FIG. 3, and the energy is concentrated here. In the concentrated position, light is absorbed and the temperature rises. As the area of the condensed part is smaller, the energy concentrates and the temperature rises more easily. Here, a semiconductor laser is generally used as the light source 1 of the optical head 11 of FIG. Usually, the emission intensity of a semiconductor laser is controlled by the amount of current flowing.

  However, as is well known, the variation in emission intensity due to current is not small. Therefore, when trying to measure an optical head equipped with a semiconductor laser with high emission intensity, the energy when focused on the diffraction grating is high, and the diffraction grating is damaged due to local temperature rise. In order to prevent this phenomenon, a general method is to measure the intensity of the emitted light before installing a new optical power meter 12 and an emitted optical head under the diffraction grating as shown in FIG. The moving mechanism 13 is installed.

  The present invention solves the above-described conventional problems. When the optical head is made to emit light and is installed at a predetermined position with respect to the diffraction grating, the diffraction grating is damaged due to the temperature rise by the collected light. It is an object of the present invention to provide an optical head evaluation method and apparatus that do not have a risk of being lost.

In order to achieve the above object, the optical head evaluation technique of the present invention includes a diffraction grating that generates a deferred sharing interference light by diffracting the light from the optical head, and the sharing interference light from the diffraction grating. detecting a condenser lens causes the condenser, a receiver member for receiving the shearing interference light is condensed, the brightness of an area including a plurality of interference fringes in the shearing interference light receiving above image receptor a a processing unit, based on the brightness of the region including the interference fringes of the upper Symbol plurality is characterized in that chromatic and a device for evaluating the output light intensity of the optical head.

  With this configuration, since the irradiation energy is not concentrated on the local area on the diffraction grating, damage to the diffraction grating can be avoided.

  As described above, according to the optical head evaluation method and apparatus of the present invention, it is possible to provide an optical head evaluation method and apparatus that have no risk of damage to the diffraction grating.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 7 is a diagram showing a schematic configuration of the optical head evaluation apparatus according to Embodiment 1 of the present invention. In FIG. 7, the same components as those in FIG.

  In FIG. 7, reference numeral 14 denotes an optical axis direction moving mechanism capable of moving the optical head 11 in a direction substantially parallel to the optical axis of light passing through the diffraction grating 5. The laser in the optical head 11 is caused to emit light at a predetermined current location, and the optical head 11 is set so that the light spot of the optical head 11 is on a predetermined optical axis on the apparatus side. At this time, the position of the optical axis direction moving mechanism 12 is set so that the optical head 11 is set away from the diffraction grating 5 by a predetermined amount or close to a predetermined amount. With this setting, when the emitted optical head 11 is placed on a predetermined optical axis, the focused spot is not narrowed on the diffraction grating, for example, as shown in FIGS. As a result, the condensing spot does not become minimum, but expands to a predetermined size.

  An example of the interference pattern obtained when the light spot is not condensed on the diffraction grating 5 is shown in FIG. In the interference region, vertical interference fringes are generated as a defocus component due to the absence of the focused spot on the diffraction grating surface. Based on the brightness of the interference pattern, the light emission intensity of the light source in the optical head 11 is adjusted. After the intensity adjustment, the optical axis direction moving mechanism 14 moves the light spot on the diffraction grating 5 to remove the vertical stripe component due to defocusing, and then the interference fringe analysis is performed. A specific example of the procedure for obtaining the brightness of the interference pattern will be described below.

  In the interference region, vertical interference fringes are generated as a defocus component due to the absence of the focused spot on the diffraction grating surface. The generation of this pattern of interference fringes is described in detail, for example, in Patent Document 1. Among the interference patterns, the arithmetic processing unit 8 calculates a value obtained by adding the luminances of the respective pixels within an area including a plurality of vertical interference fringes. By handling a region including a plurality of interference fringes, the difference between the result of processing only the bright part of the interference fringe and the result of processing only the dark part is reduced. It is possible to reduce the influence of the interference pattern variation due to the variation of the positional deviation amount Δd, that is, the density variation of the interference fringe in the vertical direction. The intensity of light emitted from the head 11 can be obtained more accurately.

  With such a configuration, it is possible to obtain an optical head evaluation apparatus that does not have a risk of damaging the diffraction grating without installing a new optical power meter.

  In FIG. 7 and other drawings, means for adjusting the light amount of the light source is not described.

  In the configuration shown in FIG. 7, the optical axis direction moving mechanism 14 for moving the optical head is shown as a means for causing the positional deviation between the diffraction grating 5 and the light spot. However, as shown in FIG. Even if the diffraction grating moving mechanism 16 for moving the lens in the optical axis direction is installed, the same effect can be obtained. If Δd is too large, interference fringes cannot be obtained correctly, and if Δd is too small, the spot area is sufficiently small and a predetermined effect cannot be obtained. From this point of view, the following ranges can be preferably used.

  The optical head evaluation method and apparatus according to the present invention has such a feature that there is no risk of damaging the diffraction grating in a diffraction interference type optical characteristic evaluation apparatus. It can also be applied to optical unit adjustment inspection applications such as machining laser unit adjustment inspection and camera lens adjustment inspection.

The figure which shows schematic structure of the conventional diffraction interference apparatus The figure which shows the outline of the interference fringe obtained with the conventional diffraction interference apparatus The figure which shows the position of the diffraction grating and light spot in the conventional diffraction interference apparatus The figure which shows the outline which provided the movement mechanism in the conventional diffraction interference apparatus The figure which shows the positional relationship of the diffraction grating and light spot which concern on embodiment of this invention The figure which shows the positional relationship of the diffraction grating and light spot which concern on embodiment of this invention The figure which shows schematic structure which concerns on embodiment of this invention The figure which shows an example of the interference fringe which concerns on embodiment of this invention, and an example of a process area | region The figure which shows schematic structure which concerns on embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Diffraction grating 6 Detection lens 7 Image receiving part 8 Signal processor 9 Display part 10 Imaging lens 11 Optical head 14 Optical axis direction moving mechanism

Claims (8)

(A) a diffraction grating that diffracts light from the optical head to generate defocused shearing interference light;
(B) a condenser lens causes light collecting the shearing interference light from the diffraction grating,
(C) a receiver member for receiving the shearing interference light is condensed,
A processing device for detecting the brightness of an area including a plurality of interference fringes in (d) above image receiving shearing interference light receiver in body,
(E) the optical head evaluation apparatus characterized by having a device for evaluating the output light intensity of the optical head based on the brightness of the region including an interference fringe of said plurality. (A) a diffraction grating that diffracts light from the optical head to generate defocused shearing interference light;
(B) a condenser lens causes light collecting the shearing interference light from the diffraction grating,
(C) a receiver member for receiving the shearing interference light is condensed,
(D) a processing device that detects wavefront aberration from an interference image of sharing interference light received by the receiver and detects brightness of a region including a plurality of interference fringes in the sharing interference light ;
(E ) an apparatus for evaluating the emitted light intensity of the optical head based on the brightness of the region including the plurality of interference fringes ;
(F) An optical head evaluation apparatus comprising: an adjustment device that adjusts an optical component in the optical head based on the wavefront aberration . The apparatus for evaluating the emitted light intensity of the optical head is an apparatus for evaluating the emitted light intensity of the optical head based on an average brightness of the entire region including the plurality of interference fringes. The optical head evaluation apparatus according to claim 1. Positional deviation amount [Delta] d between the focusing position and the diffraction grating surface by the condenser lens, 0.01μm ≦ Δd ≦ 1mm optical head evaluation apparatus according to any one of claims 1, wherein 3 to be satisfied. (A) diffracting light from the optical head to generate defocused shearing interference light;
(B) collecting and receiving shearing interference light from the diffraction grating; and
(C) detecting the brightness of a region including a plurality of interference fringes in the received sharing interference light;
(D) having a step of evaluating the emitted light intensity of the optical head based on the brightness of the region including the plurality of interference fringes.
An optical head evaluation method. (A) diffracting light from the optical head to generate defocused shearing interference light;
(B) collecting and receiving shearing interference light from the diffraction grating; and
(C) detecting wavefront aberration from an interference image of the received sharing interference light and detecting brightness of a region including a plurality of interference fringes in the sharing interference light;
(D) evaluating the emitted light intensity of the optical head based on the brightness of the region including the plurality of interference fringes;
(E) adjusting an optical component in the optical head based on the wavefront aberration.
An optical head evaluation method. The step of evaluating the emitted light intensity of the optical head is a step of evaluating the emitted light intensity of the optical head based on an average brightness of the entire region including the plurality of interference fringes. 7. The optical head evaluation method according to claim 5 or 6 . The optical head evaluation method according to any one of claims 5 to 7 , wherein a positional deviation amount Δd between a condensing position by the condensing lens and the diffraction grating surface satisfies 0.01 μm ≦ Δd ≦ 1 mm .

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