JPS61186829A - Optical measuring method of shape - Google Patents

Abstract

PURPOSE:To measure the shape of a body finished with high workability whose surface is not rough and the shape in a layer of a transparent material with ease and high precision by detecting the displacement of diffracted light of specific degree of light which is diffracted by a body to be measured. CONSTITUTION:When light from a light source 1 is incident on the body D to be measured, the object body operates like a diffraction grating which diffracts the light in a fixed direction, thereby generating diffracted light. This diffracted light is supplied to a position sensor 4 through a lens 3. Then, the lens 3 and sensor 4 so installed that only diffracted light of predetermined degree among diffracted light beams of different degree generated by the object body D is supplied to the position sensor 4. Consequently, even if the measurement object part of the object body D is generated on the surface, so only the shape of the measurement object part of the object body D is measured with high sensitivity.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an optical structure that acts like a diffraction grating that diffracts light in a certain direction when the light is incident or transmitted. The present invention relates to a method for measuring the optical shape of an object to be measured.

(Prior art) Conventionally, the shape of the measured object is measured by entering light into the measured object and applying the scattered light or reflected light from the measured object to a position sensor that serves as a displacement detection element. It was known to do so.

(Problem to be Solved by the Invention) However, in a shape measuring method that uses scattered light from the object to measure the shape of the object, when the surface of the object is nearly mirror-like, In the shape measurement method, which cannot measure the shape of the object to be measured and uses reflected light from the object to measure the shape of the object, the object to be measured is, for example, an optical information recording medium. If there is a reflective surface other than the surface of the substrate that forms the information recording surface whose shape is being measured, the reflected light from the reflective surface may cause disturbance during measurement and cause the measurement results to be affected. The occurrence of errors has become a problem, and a shape measurement method that does not have these problems has been sought.

(Means for Solving the Problems) The present invention uses an optical structure as an object to be measured, which acts like a diffraction grating to diffract the light in a certain direction when the light is incident or transmitted. An optical shape measurement method that measures the shape of an object by transversely comparing the displacement of a specific order of diffracted light among the first or higher orders of light diffracted by the object. The present invention provides an optical shape measuring method that performs the following steps.

(Example) The following two concrete contents of the optical shape measuring method of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an example of a shape measuring device for measuring the shape of an object to be measured by applying the optical shape measuring method of the present invention. is a light source, and the light emitted from this light source is incident on the object to be measured via the lens 2.

Any light source may be used as the light source.

When a laser light source is used as the light source, for example, it is possible to perform measurements with a good S/N ratio. In Fig. 1, D is the object to be measured;
It is an optical structure that acts like a diffraction grating to diffract the light in a certain direction when light enters or passes through it, and as mentioned above, the light from the light source 1 passes through the lens 2. When the light is incident on the object to be measured, diffracted light is generated by the object to be measured.

The diffracted light generated by the object to be measured is applied to the position sensor 4 via the lens 3. Now, when light is incident on a diffraction grating, the diffracted light generated by the diffraction grating is, for example, when the incident light is given perpendicularly to the diffraction grating. It is well known that the output angle θ is expressed by the following equation.

θ= sin ' λ■/Ω (However, λ is the wavelength of the light incident on the diffraction grating, which is 9 m, which is the order of the diffracted light, and Q is the spacing of the diffraction grating.) As is clear from the above equation, the constant grating spacing Ω The output angle of the diffracted light generated by a diffraction grating having If the installation positions of the lens 3 and the position sensor 4 are determined so that only the diffracted light of a predetermined order is given to the position sensor 4 through the lens 3, it is possible to Of the generated diffracted lights of each member order, only the diffracted lights of a predetermined order can be applied to the position sensor 4 via the lens 3.

Note that the measuring device shown in the first figure shows an example of the configuration in which the light is incident perpendicularly to the object to be measured, but the angle of incidence of the incident light to the object to be measured is arbitrary. Good too. Furthermore, although lenses 2 and 3 are used in the measuring apparatus shown in FIG. 1, the optical shape measuring method of the present invention can also be carried out without using lenses 2 and 3. However, when lenses 2 and 3 are used as shown in the first figure, -11! l! ! This has the advantage that the influence of the tilt of the object to be measured on the measurement results can be reduced to an extent that the accuracy of measurement can be improved.

In addition, when the lens 3 is used as shown in Figure 1, the back focal point position of the lens 3 should be located closer to the lens 3 than the position of the position sensor (in Figure 1, f indicates the back focal length of lens 3). In the apparatus shown in Figure 1, by changing the setting of the focal length of the lens 3 and the distance between the lens 3 and the position sensor 4, the displacement of the object to be measured can be magnified on the position sensor at an arbitrary magnification. It is possible to cause this to occur.

Figure 2 shows that the diffracted light of a specific order generated by the object to be measured is detected by the position sensor when the object to be measured is at position A in the figure and at the mouth position in the figure. This figure is for illustrating and explaining that each reaches a different position on 4.

FIG. 3 also shows that the shape of the object to be measured by the optical shape measuring method of the present invention is, for example, the shape of the back surface of the transparent material layer or the shape of the inside of the transparent material layer. FIG. 6 is a diagram for explaining that even in such a case, the reflected light generated on the surface of the transparent material layer of the object to be measured does not cause disturbance during measurement.

In other words, in the optical shape measuring method of the present invention, a predetermined shape is generated by an optical structure that acts like a diffraction grating to diffract the light in a certain direction when the light is incident or transmitted. This is because the diffracted light of the given order is used to measure the shape of the object to be measured.
Even if the part to be measured on the object to be measured is, for example, the back side of a transparent material layer or inside the transparent material layer, no diffracted light is generated from the surface, so only the shape of the part to be measured in the object to be measured is highly accurate. It can be measured.

The position sensor 4 described above is commercially available under the name of position sensor 1. For example, a uniform resistive layer having a photoelectric effect is formed on the surface of a silicon substrate, and an electromotive force is generated by the incidence of light on the resistive layer. In addition, a pair of signal extraction electrodes are provided on the surface of the resistive layer, and a current proportional to the incident light flowing through the resistive layer is divided between the two electrodes and flows out. A device configured such that an amount of electricity in a current-voltage converted state is output from two electrodes may be used.

The output from the position sensor 4 described above is subjected to necessary signal processing in the signal processing circuit 5, and a signal corresponding to the incident position of the diffracted light on the position sensor 4 is outputted to the output terminal 6.

The signal processing circuit 5 receives the voltage Vl that is separately output from the two electrodes of the position sensor 4.

Addition circuit ADD that adds v2 and the voltages Vl and V
A subtraction circuit SυB that subtracts 2 and the above-mentioned subtraction circuit SOB
The output signal (Vl - V2) from is the dividend, and
Output signal (V1+V2) from the adder circuit ADD described above
A known configuration may be used, such as a divider circuit DIV that performs division using , as a divisor, and a characteristic correction circuit CCC (the characteristic correction circuit corrects the nonlinearity of the position sensor 4). ).

(Effects) As is clear from the detailed explanation above, the optical shape measuring method of the present invention has an effect similar to a diffraction grating that diffracts the light in a certain direction when the light is incident or transmitted. An optical shape measuring method using an optical structure as an object to be measured, in which the displacement of a specific order of diffracted light among the first or higher order diffracted light in the light diffracted by the object to be measured. Since the shape of the object to be measured is measured by detecting the It is possible to easily measure the shape of a workpiece that has a highly machined surface that is not rough, and it is also possible to easily measure the shape of a workpiece that has a highly processed surface that is not rough. However, with the optical shape measurement method of the present invention, it is also possible to measure the shape of the back surface of a layer of transparent material and the shape of the inside of a layer of transparent material. According to the optical shape measuring method of the present invention, all the problems in the conventional examples described above can be satisfactorily solved. The measuring method can be effectively used for measuring the shape of an optical information recording medium disk, such as one in which grooves or pits are arranged on a transparent substrate.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an exemplary configuration of a measuring device that performs optical shape measurement by applying the optical shape measurement method of the present invention, and FIGS. 2 and 3 show the operation of the optical shape measurement method of the present invention. It is an explanatory diagram.

Claims (1)

[Claims] An optical shape measurement method that uses an optical structure to be measured that acts like a diffraction grating to diffract the light in a certain direction when it is incident or transmitted through the object. An optical shape measurement method that measures the shape of an object by detecting the displacement of a specific order of diffracted light among the first-order or higher-order diffracted light in the diffracted light.