JPS60166808A - Shape measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the shape at a high accuracy by employing a semiconductor position detector having a 2-D light receiving surface as a photoelectric converter for detecting the (0)th diffracted light and the (n)th diffracted light to correct the deviation in the surface to be measured not affected by distortion or the like thereof. CONSTITUTION:An object 11 to be inspected is a disc-shaped one like an optical video disc. Light outputted from a light source 12 comprising a laser unit is reflected with a mirror 13 and incident on the object 11 being inspected at the angle of theta0 with respect to the normal thereof. After the entry into the object 11 being inspected, reflected and diffracted light is detected with two 2-D type semiconductor position detectors 14 and 15 and a photodiode 16 and the outputs separately undergo a signal processing. The pitch P, width (a) and depth (h) are determined with a signal processing calculator 17 of such a type and shown on a display section 18. To measure the object 11 being inspected entirely, under the control of the signal processing calculator 17, a motor 19 is driven to rotate the object being inspected while it 11 is moved parallelly with a motor 20.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a method for determining the average width, depth, and pitch of irregularities (turns) in which basic patterns such as those on a video disc are arranged substantially regularly. The present invention relates to an improvement of a shape measuring device that can perform measurements even when there is distortion on a measuring surface.

[Technical background of the invention and its problems]

2. Description of the Related Art Conventionally, a device has been proposed for measuring the shape of a regular uneven pattern such as that seen on a video disc, which irradiates laser light and measures the diffracted light. (Unexamined Japanese Patent Publication No. 57
However, in such a device, if the surface to be measured is distorted or tilted, the average pitch of the uneven pattern will be inaccurate80, and the unevenness will be affected by so-called surface runout. There were also drawbacks such as inaccuracy in depth measurements.

In addition, if there is surface wobbling, there is also the drawback that the measurable range for changes in the diffracted light, such as deviations from the light-receiving surface of the detector, or changes in pitch, etc., is narrow.

[Purpose of the invention]

The purpose of this invention is to provide a shape measuring device that improves the above-mentioned problems and can correct surface wobbling without being affected by distortion of the surface to be measured and measure the shape with high accuracy. do.

[Summary of the invention]

This invention uses a two-dimensional semiconductor device detector or a semiconductor device detector having a two-dimensional light-receiving surface to detect the Oth-order diffraction light and the first-order diffraction angle (the first-order diffraction light is mainly used). . That is, the amount of surface wobbling of the surface to be measured is measured by detecting the position of the O-th order diffracted light (reflected light) using a two-dimensional semiconductor device detector. Next, the position of the 1st-order diffracted light is detected by a two-dimensional semiconductor device detector, and the 1st-order diffraction angle is calculated from the difference in position from the previous 0th-order diffracted light, and the amount of surface wobbling is corrected to accurately Measure pitch. This value is used to calculate the shape such as depth.

Furthermore, when objects with various pitches are input,
If there is surface wobbling, the measurable range becomes narrower. Therefore, the detector that detects the diffracted light of each order is placed on a freely movable drive system and moved to an optimal position for measurement. In this way, the measurable range is expanded.

〔Effect of the invention〕

As described above, since the amount of surface runout is measured and corrected using the measured value to calculate an accurate shape, highly accurate measurement is possible. Additionally, the mechanism becomes simpler as it does not require a high-precision autofocus mechanism like that found in optical disc players. This also makes it possible to achieve higher reliability and higher speed. In addition, since two semiconductor device detectors are used to detect the amount of surface runout, the speed is high, and since the light intensity can also be detected at the same time, there is no need for a special detector for detecting light intensity for shape measurement. This has the effect of simplifying the detection system.

Furthermore, since each detector can be moved to an optimal position, the measurable range for various pitches is expanded even if there is surface wobbling.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. First, the measurement principle and surface blur correction will be explained, and then an example of expanding the measurable range by optimally moving the detector will be explained.

In FIG. 1, the object 11 is disk-shaped like an optical video disk. The light emitted from the light source 12 consisting of a laser device is reflected by the mirror 13, and is at an angle of θ with respect to the normal to the subject 11. incident at an angle of Subject 11
After entering, the reflected and diffracted light is detected by two two-dimensional semiconductor device detectors (for example, manufactured by United Delactor or Hamamatsu Photonics, etc.) 14 and 15 and one photodiode 16, respectively. In the signal processing calculator 17 that processes the signal, the pitch 21 width a and the depth 1
1 is displayed on the display section 18.

It is assumed that the surface shape of the optical video disc is as shown in FIG. In this case, to calculate p+a+h, the intensity of the 0th-order diffracted light is 1°, the intensity of the 1st-order diffracted light is In, and the intensity of the 21st-order diffracted light is 14n. According to the following formulas can be used.

Here, the angle θ. From FIG. 1, θ is the incident angle at the laser tip, and is the diffraction angle of the first diffracted light.

Now, in order to measure the entire surface of the subject 11, under the control of the signal processing computer 17, the motor 9 is driven to rotate the subject, and the motor 20 is also used to rotate the subject 11.
What is necessary is to perform the measurement by moving in parallel. Alternatively, the light source 11, mirror 13, detectors 14, 15, and 16 may be provided on the same stage and moved in parallel, and the subject 11 may be rotated only by the motor 20 to measure the entire surface of the subject. .

Next, the image blur correction process will be explained.

Now, consider the case where the disk surface is tilted only at θ as shown in FIG. At this time, the incident angle of the light incident on the optical disc is θ. From θ. = θk, the pitch P and depth 1h can be calculated using (Equation 11 and (3)
), the following equations are obtained.

λ Now, the angle θ0 of the 0th order diffracted light (reflected light) is expressed by the following equation as shown in FIG.

θ0−θ. -2θ makes θ=LA(θ0-00)...song (6). Also, the angle θ1 of the first-order diffracted light is shown in Figure 3 as θ = 00−
〇Therefore, θ=θ0-θ1 (7). Therefore, equations (4) and (5) become equations (6),
It is sufficient to use θ and θ determined by equation (7). In this way, it is possible to correct the influence of surface wobbling.

Next, a processing method using an output signal of a two-dimensional semiconductor device sensor (PSD) will be specifically described.

Two PSDs are arranged as seen in FIG.

The center position of the PSD for 0th-order light detection is θc0, and the 1st
The center position of the PSD for secondary light detection is assumed to be θc″.

Since the output signal of the PAD is proportional to the position of the light incident on the PSD, the output signal X of the PSD 14 shown in FIG. 4 corresponds to the position θ0 of the 0th order diffracted light. 1 and X
. ′ has the following relationship.

Here, r is a percentage of the detection size of the PSD, and R is the distance from the reflective surface of the optical disk to the detector.

Similarly, the following relationship exists between the position θ1 of the first-order diffracted light and the output signals X, I, X,'' of the PSD 15.

In addition, the intensity of the 0th order diffraction light is calculated. , the first-order diffracted light intensity is 1, then the relationship with the output of the PSD is as follows.

Therefore, if we set ln=11, we can calculate (41, (21, (according to formula 51), p + a + h, respectively.In addition, the respective numerical values at this time are (6), I, +81,
(9) , (If you request Equation 11, it becomes possible to determine the shape parameters p, a, and h without being affected by surface runout.

That is, as shown in FIG.
Enter. Therefore, the 0PU17 sends a signal to the analog multiplexer 21, selects each output signal, sends it to the A/D converter 22, converts it into a digital signal, and inputs the signal to the 0PU17.

This signal is processed as described above. The results are displayed on the display unit 18 inputted from the color ORT, for example, in the form of maps, graphs, etc., which are divided by color. In this way, it is possible to measure the shape of the guide groove of the optical disc without being affected by surface runout.

Next, an example will be described in which each of the detectors 14, 15, and 16 is moved to an optimal position, and it becomes possible to measure disks with various pitches and many surface wobbles.

FIG. 5(a) is a diagram of the moving system of the detector.

FIG. 5(I)) is a view seen from arrow A point in FIG. 5(a).

Light emitted from the laser light source 12 is irradiated onto the optical disc 11 by the Mi 2-13. The direction of the 0th order diffracted light reflected by the surface of the optical disk 11 is fixed unless there is surface wobbling. Furthermore, even if there is some surface wobbling, it can be detected by a fixed detector if it is not too large. For example, in equation (8), R=60
wm, 1 = 6 mm (in the case of a detector with an effective light receiving surface of 12 dragon mouths), the detection range of the 0th order diffracted light is ±5.7°
becomes. Therefore, according to equation (6), ±2.
Even fluctuations within 80 can be detected. Incidentally, the surface fluctuation on the surface of a normal optical disk is much smaller than this value.

Next, the diffraction position of the first-order diffracted light depends on the amount of surface wobbling and the pitch P. Therefore, in the case where single samples of various pitches P are inserted, the position of this first-order diffracted light moves greatly, making it impossible to detect it with a fixed detector. Although it is not possible to inspect optical disks with various pitches in the normal C manufacturing process, there may be optical disks with various pitches under development.

Even in this case, it is difficult to manufacture with a continuous pitch change, and in most cases, a fixed range is manufactured with a constant pitch. In this case, move the detector to the optimal position as follows.

First, a point with no surface wobbling is found on the optical disk so that the position of the 0th order diffracted light is approximately at the center of the detector 14. This can be found by moving the optical disk until the first term of equation (8) becomes approximately O. Next, the detector 15 is moved to bring the position of the first-order diffracted light to the center of the detector 15. This includes a pulse motor 51 shown in FIG.
and transfer this rotational force to the arm 5 attached to this motor.
2, and moves the detector 15 provided at the tip of the reader in a circular motion. At this time, it is moved so that the first term of equation (9) becomes approximately O. From this movement amount θcl
is determined. Next, the position of the second-order diffracted light detector 16 may be determined in the same manner as in the above algorithm if a two-dimensional semiconductor device detector is used for this diffracted light (second-order). However, the detection of the second-order diffracted light does not need to be performed using a two-dimensional semiconductor device detector.

Here, a semiconductor detector that can only measure light intensity is used. In this case, the first-order diffracted light θ is calculated using equations (8), (9), and (7). Next, double the diffraction angle and Oc
It is sufficient to move the detector 16 for detecting the second-order diffraction light by the sum of 0 and 2θ+θC0.

To do this, the pulse motor 53 shown in FIG.

By doing this, the detector 14°15.16 that detects the 0th-order diffracted light, the 1st-order diffracted light, and the 2nd-order diffracted light is
#1 detects light at the center of the detector, and the amount of deviation is only due to surface wobbling. This is similar to the case of the O-order diffraction light described above, so in this case, it is possible to measure even if the optical disc has surface wobbling within ±28°.

[Other embodiments of the invention]

In the above explanation, an example of a guide groove of an optical disc was described, but the present invention is also applicable to the application example described in Japanese Patent Application Laid-Open No. 57-187604.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is a sectional view showing the specific structure of the object to be examined, Fig. 3 is a diagram showing the position of diffracted light in a state where there is surface wobbling, and Fig. 4 5 is a diagram showing the positional relationship between a two-dimensional semiconductor device detector and diffracted light, and FIG. 5 is a diagram showing a moving system of the detector. 11... Subject, 12... Light source, 13... Mirror, 14.15... Two-dimensional semiconductor device detector, 16.
... Photoelectric converter, 17 ... OPU, 18 ... Display unit, 19 ... 1 stage, 20 ... Horizontal movement stage, 21 ... Multiplexer - 122 ... A/D converter , 51.53...Pulse motor. Agent Patent Attorney Kensuke Chika (and 1 other person) No. 1
Figure 3 Figure 4

Claims (1)

[Claims] fl) A light source that generates substantially coherent light, and a means for irradiating the light emitted from the light source onto a concave-convex pattern in which the basic pattern is arranged substantially regularly, obtained by this means. Each photoelectric converter detects the 0th and 2nth order diffracted light, and the signal of the nth law diffracted light and the signal of the 2nd order diffracted light obtained by these photoelectric converters p1 is the average of the basic pattern. In the shape measuring device, the width of the 0th-order diffracted light and the n-th modal diffracted light are calculated based on the average depth in the basic pattern. A shape measuring device characterized in that a semiconductor device detector having a two-dimensional light receiving surface is used as a photoelectric converter for detecting light. (2) The shape measuring device according to claim 1, further comprising a moving means for moving a detector for detecting the 0th-order diffracted light, the n-th method diffracted light, and the 2nd-order diffracted light.