JPH0216245Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] This invention particularly relates to a measuring instrument most suitable for measuring the depth of a signal pit (hereinafter simply referred to as a pit), which is a signal groove of an optical disk. It is.

[Conventional technology]

Optical disks such as video disks and DAD (digital audio disks)
A master master disc is formed by irradiating a photo resist master disc with a photo resist liquid applied to the surface of a glass plate to form pits consisting of spiral recesses, and then nickel electroforming is applied to this master master master disc. to form a nickel stamper.

Then, a plastic mold disk is formed by resin-molding this nickel stamper, and a reflective film is formed by vapor-depositing aluminum on the surface of this plastic mold disk, and a reflective film is formed on the top surface of this reflective film. A commercially available optical disk is formed by gluing a highly transparent plastic such as acrylic resin.

Optical discs are manufactured through the processes described above, but if the transfer of the nickel stamper from the master disc and the transfer from the nickel stamper to the plastic mold disc are not performed accurately, problems may occur during playback. fidelity will be degraded.

Conventionally, it has been known to measure the fidelity of transfer for each semi-finished disk by measuring the depth of the pits.

That is, this method, as shown in Figure 1,
The depth of the pits 1a can be indirectly determined by measuring the intensity of the laser light using a diffraction phenomenon that occurs when, for example, a laser beam is irradiated onto the pit 1a surface of the disk 1 as a semi-finished product such as a nickel stamper or a plastic mold board. This is a method of knowing.

Note that ξ is a coordinate axis in the track (tangential) direction that extends along the pit row through the midpoint of the short side of pit 1a, and η is a coordinate axis that is perpendicular to the coordinate axis ξ and extends through the midpoint of the long side of pit 1a. Z is the coordinate axis in the radial (tracking) direction, Z is the coordinate axis extending perpendicular to the plane formed by the two coordinate axes ξ and η, p is the wavelength of pit 1a, β is the length of pit 1a, and r is q represents the width of the pit 1a, and q represents the track pitch of the pit 1a, respectively.

As shown in FIG. 2, as a method for indirectly knowing the depth of the pit 1a by measuring the intensity of the light beam, among the transmitted light irradiated onto the disk 1, zero-order light 2a having a different degree of curvature is used. , primary light 2b, secondary light 2c
The depth of pit 1a can be indirectly determined by measuring the intensity of...
As shown in the figure, among the reflected lights irradiated onto the disk 1, zero-order light 2a, first-order light 2b, and
There is a reflection measurement method that indirectly determines the depth of the pit 1a by measuring the intensity of the secondary light 2c.

Of these, the details of the apparatus in the transmission measurement method will be explained based on FIG. 4. From the light emitter 3,
A laser beam (He-Ne laser beam) 4 of 1 mW, λ = 6328 Å is modulated via a chopper 5 to irradiate the disk 1 without being affected by external light, and depending on the presence or absence of the pit 1a, The intensity of the ±1st-order lights 2b and 2'b, which have different transmittances due to the diffraction phenomenon that occurs, is subjected to optical-to-electrical conversion by a light receiver 6 such as a light receiving element, then amplified by an amplifier 7 and displayed on a synchroscope 8. The level is displayed by the waveform,
The depth of pit 1a is measured from the wave height.

Expressing this in the formula, 1st order diffraction efficiency = 1st order diffraction light intensity / 0th order light intensity =1st order photocurrent/0th order photocurrent =f(d,a,h) becomes.

Here, f is the function, d is the duty, a is the width of the pit 1a, h is the depth of the pit 1a, and if the duty d and width a are known, the depth h of the pit 1a is
can be known.

By the way, since the duty d and the width a are almost constant under conditions such as mastering, by comparing the first-order diffraction efficiency of each disk 1 as the object to be measured, it is possible to determine the diameter of the pit 1a formed by the injection extrusion method. It becomes possible to perform a relative comparison of the depth h.

[The problem that the idea attempts to solve]

However, in the conventional device as described above, the measurement location on the disk 1 is not constant, resulting in poor reproducibility.Moreover, in order to perform the measurement, for example, two types of laser beams, the zero-order light 2a and the first-order light 2b, are required. However, only one light receiver 6 is equipped.

Therefore, each time a measurement is made, it is necessary to move the light receiver 6 and repeat the measurement individually, making it impossible to obtain a stable measurement value, resulting in a decrease in measurement accuracy.

This is because if the measurement distance is not constant, the light level changes as the square of the distance, resulting in a decrease in accuracy, and there is a large error in reading the measurement value between operators.

Since the light receiver 6 is moved and measurements are repeated individually, the measurement time becomes longer, and if the light source light intensity level changes during repeated measurements,
The accuracy of the value of the diffraction efficiency decreases.

Furthermore, in order to eliminate the above-mentioned drawbacks, if multiple light receivers are provided for transmission measurement method, reflection measurement method, multiple types of disks (objects to be measured), and diffracted light, the device becomes larger. There are drawbacks.

This idea was created in view of the above-mentioned shortcomings, and it is possible to stably measure the intensity of the light beam in a short time, and to reduce the measurement reading error with constant reproducibility of the measurement location of the object to be measured. The purpose of the present invention is to provide an optical disk pit measuring instrument that can be used for both transmission measurement and reflection measurement, and can be easily miniaturized even when adapted to measure multiple types of objects. be.

[Means to solve the problem]

The optical disk pit measuring device according to this invention rotates on a circle around the central axis of the measuring table, and has two supports that can be fixed at arbitrary positions on the circle, and these two supports. The device is equipped with two light receivers each attached to the body to receive light transmitted through or reflected by the object to be measured.

[Effect]

The optical disc pit measuring device according to this invention can receive light from an object to be measured using two light receivers by rotating two supports and fixing them at predetermined positions.

Therefore, measurements can be made with a constant measurement distance, and 2
By rotating and fixing the two supports, it is also possible to correspond to transmission measurement method and reflection measurement method.

〔Example〕

An example of this invention is shown below in Figures 5 and 6.
This will be explained based on the diagram.

In addition, in Figures 5 and 6, Figures 1 to 4
The same parts as those in the figure are given the same reference numerals.

This embodiment basically includes an object to be measured 10 such as a nickel stamper as a semi-finished product of an optical disk such as a video disk or a DAD, or a plastic mold disk, and a device to be measured. A measuring table 11 to be set, a motor 12 for rotating the object to be measured 10 at a constant speed, a feeding mechanism 13 for reciprocating the object to be measured 10 on the measuring table 11, and a laser beam to the object to be measured 10. a light emitter 3 for irradiating light 4;
Light receivers 14 and 15 formed of light receiving elements to detect the laser beam 4 irradiated onto the object to be measured 10
and a positioning means 16 for fixing the light receivers 14 and 15 at arbitrary positions around the measuring table 11.

The measuring table 11 is mounted on the basic base 17 through a fixed boss 18 that is fitted into and fixed to the basic base 17.
9 and is fixed.

Reference numeral 20 denotes a mounting frame fixed to the fixed boss 18 with bolts 21.

The feed mechanism 13 also includes a screw shaft 23 coaxially attached to a motor shaft 22a of a motor 22 provided on the side surface of the mounting frame 20 via a joint 22b,
3 and to which the motor 12 is fixed, and pillars 26 and 27 erected on a mounting board 25 to rotatably support the screw shaft 23.

28 is a stopper mechanism for moving the screw cylinder 24 a certain distance;
is a protrusion 24a protruding from the lower end of the screw tube 24.
and a position regulating switch 29, which is disposed oppositely on the mounting board 25 so as to be spaced apart from the protruding piece 24a.
Formed from 30.

32 is a shield box that covers the light emitter 3.

Further, the light receivers 14 and 15 are attached to columns 33 and 34 that are rotatably erected on the outer periphery of the measurement table 11, and as means for rotatably attaching the columns 33 and 34 to the measurement table 11, The mounting pieces 33a, 34a fixed at right angles to the lower ends of the columns 33, 34 are movably inserted into the gap 19 of the basic base 17, and the protrusions 36 attached to the mounting pieces 33a, 34a via coil springs 35 are inserted. Measuring table 1
It is inserted into an annular groove 37 provided on the outer periphery of the lower surface of 1.

Further, a positioning means 16 for fixing the light receivers 14 and 15 at arbitrary positions around the measuring table 11.
, a recessed portion 37 into which a projection 36 biased by a coil spring 35 falls into an annular groove 37.
Provide a.

The light receivers 14 and 15 are fixed by movable screws 39 within slits 38 provided in the supports 33 and 34 in order to adjust the mounting height relative to the supports 33 and 34.

40 is a mirror for changing the optical path of the laser beam 4 emitted from the light emitter 3; 5 is a chopper placed between the mirror 40 and the object to be measured 10; When the laser beam 4 is projected, the laser beam 4 is supplied as modulated light to the object to be measured 10, thereby making the measurement more precise without being influenced by extraneous light from the surroundings.

Reference numeral 41 denotes an operation section in which a power supply, a computer, etc. are built-in.

One embodiment of this invention is constructed as described above,
To perform measurements, the object to be measured 10, which is a nickel stamper as a semi-finished product of an optical disk such as a video disk or DAD, or a plastic mold disk, is moved by a motor 12 using a clamper.
clamp to the motor shaft 12a.

Then, the laser beam 4 is emitted from the light emitter 3, the optical path is changed by the mirror 40, and then it is projected into the slit of the chopper 5 to become modulated light.Then, the laser beam 4 is made to be a modulated light so as not to be affected by external light. The object 10 is irradiated and measured, and the measuring method will be described in detail below.

First, the object to be measured 10 is rotated at a constant speed by the motor 12, and the screw shaft 2 of the feed mechanism 13 is rotated at a constant speed by the motor 12.
3 is rotated by a motor 22, and a screw tube 24 screwed into a screw shaft 23 moves, whereby the laser beam 4 is radiated onto the object 10 to be measured in the radial direction.

The feed mechanism 13 is capable of reciprocating in the radial direction of the object to be measured 10, but a protrusion 24a protruding from the lower end of the screw tube 24 controls the position regulation switch 2.
It is movable by the distance that turns on 9 and 30.

Further, a support 3 is provided on the outer periphery of the circular measuring table 11.
Since the light receivers 14 and 15 attached to 3 and 34 are movably attached, the light receivers 14 and
15 can be used as a transmission type measuring device if it is moved to the opposite side of the object to be measured 10 from the emitter 3, and the receivers 14 and 15 are placed on the same side of the object to be measured 10 as the emitter 3. When moved, it can be used as a reflective measuring device.

Also, during measurement, the light emitted from the light emitter 3,
Laser light 4 whose optical path is changed by mirror 40
When used as a transmission type measuring instrument by moving and setting one optical receiver 14 on the extension line so that the optical axis always passes through the center of the measuring table 11, the optical axis is detected by the optical receiver 14. Light becomes 0th order light,
The light detected by the light receiver 15 set at an arbitrary angle from the light receiver 14 becomes primary light.

In this case, the set position of the two light receivers 14 and 15 is set by the protrusion 3 which is energized by the coil spring 35.
6 is a recessed portion 37a, 3 provided at a predetermined position within the annular groove 37, for example, at an arbitrary angle with respect to the extension line of the optical axis.
7a, the supports 33 and 34 to which the light receivers 14 and 15 are attached can be positioned and set at predetermined positions.

Further, in the case of a reflection type measuring instrument, the positions of the pillars 33 and 34 can be easily determined by similarly lowering the protrusions 36 provided at predetermined positions into the recesses 37a and 37a.

The mounting height of the receivers 14 and 15 is determined by screw 3.
Adjustment can be easily made by loosening the screw 9 and moving it within the slit 38, and then tightening the screw 39.

Note that the processing of the light transmitted through the object to be measured 10 or the light reflected from the object to be measured 10 detected by the light receivers 14 and 15 is performed in the same manner as known methods.

[Effect of idea]

As described above, according to this invention, the measurement table rotates on a circle around the central axis, and the object to be measured is transmitted through two supports that can be fixed at any position on the circle. Since each light receiver is attached to receive the light reflected by the object to be measured, the intensity of the light beam can be measured stably in a short time under the same conditions. The measurement location can be measured with constant reproducibility and measurement reading errors can be reduced.

Furthermore, it can be used for transmission measurement methods and reflection measurement methods, and has the effect of facilitating miniaturization even when adapted to measuring multiple types of objects to be measured.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the disk surface in an enlarged state, Fig. 2 is an explanatory diagram showing the conventional transmission measurement method,
Figure 3 is an explanatory diagram also showing the reflection measurement method, and Figure 4.
The figure is a schematic diagram of a conventional device that uses the transmission measurement method.
FIG. 5 is a plan view showing an embodiment of the optical disk pit measuring device of this invention, and FIG. 6 is a side view of the same. 3... Light emitter, 4... Laser light, 10... Measured object,
DESCRIPTION OF SYMBOLS 11... Measuring stand, 14, 15... Light receiver, 16... Positioning means, 33, 34... Support column.

Claims (1)

[Claims for Utility Model Registration] A measuring table for setting an object to be measured such as an optical disk; a light source for irradiating light to the object placed on the central axis of the measuring table; two supports that can be rotated on a circle around the central axis of the measuring table and fixed at arbitrary positions on the circle; An optical disk pit measuring instrument comprising: two light receivers for receiving light transmitted or reflected by the object to be measured.