JPH02272304A - Optical axis movement measuring instrument - Google Patents

Abstract

PURPOSE:To perform accurate measurement without receiving the influence of the change of laser beam quantity by measuring the intensity of laser light used for the measurement and correcting a measured value in accordance with the intensity. CONSTITUTION:The laser beam from a laser 11 is bisected by a half mirror 12 and respectively received by a four-division photodetector 13 and a photodetector 14 for monitoring a light quantity. The quadrisected photodetector 13 has four photodetector parts A, B, C and D divided in X and Z directions which are nearly perpendicular to the optical axis of the laser beam and perpendicular to each other. The signal of the laser beam quantity received by the respective surfaces is arithmetically operated by an arithmetic operation circuit 15 to measure positional deviation in vertical and horizontal directions. Measurement errors occurring with the change of the laser beam quantity are corrected with a signal from the photodetector 14 for monitoring a light quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical axis movement measuring device used in an optical disk master exposure machine and the like.

[Conventional technology]

Conventionally, as an optical axis movement measuring device, there is one that measures the moving distance of the optical axis of a laser beam using a position detection element. Other optical axis movement measuring instruments include a pair of two-split light-receiving elements oriented in two directions perpendicular to each other, and the laser beam is split into two by a light splitting means such as a half mirror or beam splitter. JP-A No. 52-45840 discloses a method (2) in which light is received by a pair of two-split photodetectors and the moving distance of the optical axis of the laser beam is measured from the output signal of the pair of two-split photodetectors;
It is known from JP-A No. 62-280713, 1985 IEICE General Conference Report 1055R Laser Optical Axis Variation and Its Control Method. Furthermore, the error in the relative position of the two laser beams is detected using a four-part light receiving element,
A device that keeps the distance between the two laser beams constant by controlling one of the two laser beams based on the error signal ■
is known from Japanese Patent Application Laid-Open No. 62-283426.

[Problem to be solved by the invention]

The resolution of the above-mentioned optical axis movement measuring device (2) is currently 10 μm, making it impossible to measure with higher precision.

Moreover, since the measurement resolution changes due to changes in the amount of light, the amount of light must be kept constant.

In addition, since the optical axis movement measuring device (2) uses a pair of two-split light-receiving elements, the arrangement and alignment of the optical axis become complicated, making it impossible to improve accuracy and increasing the size.

The optical axis movement measuring device (2) measures the distance of movement of the optical axis of the laser beam without considering the light intensity and tip aperture, so it is not possible to tell whether the optical axis has changed or the light intensity or tip aperture has changed.

The optical axis of the laser beam is always changing, and especially when the laser is warming up (starting), the temperature inside the laser tube is changing until the temperature inside the laser tube is sufficiently warmed up. Once the laser has completed warming up, the fluctuations in the optical axis of the laser beam will become minute. Therefore, when using a stable laser beam, always warm up for 1 to 2 hours, but the time when the laser beam reaches a stable state can be determined by measuring the distance the optical axis of the laser beam moves using the optical axis movement measuring device mentioned above. Even when measured, it was not clear. This is because the above-mentioned optical axis movement measurement device measures the distance traveled by the optical axis of the laser beam without taking into account the light intensity and tip aperture of the laser beam, so it is not possible to tell whether the optical axis has changed or the light intensity or tip aperture has changed. be.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks, and to provide an optical axis movement measuring device that can perform accurate and highly accurate measurements and can be made compact.

[Means to solve the problem]

In order to achieve the above object, the invention of claim 1 includes a light splitting means for splitting light into two, a 4-split light receiving element for receiving one light from the light splitting means, and a light receiving element for receiving one light from the light splitting means, and a light receiving element for receiving one light from the light splitting means. Difference signals in two directions perpendicular to each other are obtained from the four output signals from the light receiving element for detecting the amount of light and the four-division light receiving element, and these difference signals are sent to the light receiving element for monitoring the light amount. The invention further comprises arithmetic means for correcting the amount of light according to the output signal, and the invention according to claim 2 includes light splitting means for splitting light into two, and one light from the light splitting means. A 4-split light receiving element that receives light, a light aperture measuring means that detects the aperture of the other light from the light splitting means, and a difference signal in two directions perpendicular to each other from the four output signals from the 4-split light receiving element. and calculation means for correcting these difference signals according to the aperture using the output signal of the optical aperture measuring means.

[For production]

In the invention of claim 1, the light is split into two by the light splitting means, one light from the light splitting means is received by a four-split light receiving element, and the amount of the other light from the light splitting means is used for light amount monitoring. Detected by a light receiving element. The arithmetic means calculates difference signals in two directions perpendicular to each other from the four output signals from the four-divided light receiving element, and corrects these difference signals according to the amount of light using the output signal of the light receiving element for monitoring the amount of light.

In the invention of claim 2, the light is split into two by the light splitting means, one light from the light splitting means is received by the four-split light receiving element, and the aperture of the other light from the light splitting means is measured by the optical aperture measurement. Detected by means. The calculation means calculates two directions perpendicular to each other from the four output signals from the four-part light receiving element.
and correct these difference signals according to the aperture using the output signal of the optical aperture measuring means.

〔Example〕

FIG. 1 shows an embodiment of the invention.

This embodiment is used to check the warming-up time of the Ar+ laser of the optical disk master exposure machine, and one laser beam from the laser 11 is used to
The light is divided into two by 2 and received by the 4-split light receiving element 13 and the light receiving element 14 for monitoring the amount of light. 4
As shown in FIG. 2, the divided light-receiving element 13 has four light-receiving parts A, B, C, and D divided in the X and Z directions, which are substantially perpendicular to the optical axis of the laser beam and perpendicular to each other. 12
A spot S is irradiated with laser light from. This 4
The center of the divided light-receiving element 13 coincides with the center of the spot S when it is at a normal position, and the arithmetic circuit 15 is constructed as shown in FIG. Output signal a of each light receiving section A, B, C, D of the four-divided light receiving element 13.

b, c, and d are binarized at zero level by comparators 16 to 19 to become pulse signals, and adders 20 to 23 add two mutually different signals (a+b).
L(c+d), (a+d), (b+c).

Each output signal (a + b), (c +
d) is subtracted by the subtracter 24 and becomes a difference signal in the X direction = (a + b) - (c + d), and the adder 22
．． 23 output signals (a+d) and (b+c) are subtracted by subtracter 2.
4, the difference signal in the Z direction is m = (a + d) -
(b+c). The light receiving element 14 for monitoring the amount of light detects the amount of laser light, and its output signal is binarized at zero level by the comparator 26. The correction circuit 27 receives the difference signals in the X and Z directions from the adders 24 and 25! =(a+b)-(c+d), m=(a+d)
(b+C), based on the pulse signal n from the comparator 26, a coefficient of 1. is corrected by multiplying by , and the result is j=((a
+b) (c + d)) X kz, k = ((
a+d)-(b+c))Xk is output as a measurement signal indicating the optical axis movement distance of the laser beam. The signals of each part of this arithmetic circuit 15 are as shown in FIG. 5, and the relationship between the light intensity of the laser beam, the coefficient □lk2, and the measured value of the optical axis movement of the laser beam (j, k) is shown in FIG. In this way, the measured value (j, k) of the amount of optical axis movement of the laser beam is no longer affected by the light intensity of the laser beam. The coefficient k2 is determined by experiment, and Figures 7 and 8 show the optical axis movement amount of the laser beam and the difference signal in the X direction and Z direction when the light intensity of the laser beam determined by experiment is 0.03 mW. ! Indicates the relationship with +m. 9th
Figures and Figure 10 show that the amount of laser light determined by experiment is 0.0.
Figures 11 and 12 show the relationship between the amount of optical axis movement of the laser beam and the difference signal of 2m in the X and Z directions in the case of 5a+v.
The optical axis movement amount of the laser beam and the difference signal in the X direction and the two directions in the case of ! The relationship with 1m is shown. Figures 13 and 14 show the relationship between the amount of laser light and the coefficient □lkm obtained through experiments, and from this experimental result, tk2 is □=
8.5 X 10-'x+2.02X10-', k,
=8.25X10-'x+2.4X10-4.

Here, X is a value indicating the amount of laser light.

FIG. 15 shows another embodiment of the invention.

This embodiment is a difference signal in the X direction and two directions in the above embodiment! Instead of correcting 1m according to the amount of laser light,
The difference signal in the direction and the Z direction is corrected according to the aperture of the laser beam.

One laser beam from the laser 11 is divided into two beams by a half mirror 12, and each beam is received by a four-split light receiving element 13 and a light receiving element 28 for monitoring the optical aperture. The optical aperture monitor light receiving element 28 detects the aperture of the laser beam from the half mirror 12, and the arithmetic circuit 29
It is configured as shown in Figure 6.

This arithmetic circuit 29 includes adders 20 to 2 similar to those in the previous embodiment.
3. Includes subtractors 24 and 25, and if the output signal of the subtractor 24 is y, then y = 'x k ' = 0.0402 φ-0・"9φ: laser beam aperture ': correction coefficient .From these formulas, x = y / k' = y 10.0402・φ
-0・G59, and when converted to logarithmic representation, 1
ogx =1.396+0.6591ogφ10log
It becomes y. Considering the constant term on the left side of this equation, log
By calculating x, = 0.6591ogφ+logy, the amount of optical axis movement of the laser beam (corrected for errors due to changes in aperture or aperture settings) can be obtained. Therefore, the output signal of the subtraction Q24 is determined by the positive/negative determining section 30 as to whether it is positive or negative.
The output signal of is inverted by the inverter 31. If the output signal of the subtracter 24 is positive, it is sent to the logarithmic amplifier 33 through the gate 32 according to the output signal of the positive/negative determining section 30.
If it is negative, it is inverted by the inverting circuit 34 and then the inverter 3
1 output signal passes through the gate 35 to the logarithmic amplifier 33.
sent to. Further, the output signal of the optical aperture monitoring light receiving element 28 is amplified by a logarithmic amplifier 36 and multiplied by a coefficient k'' (=0.659) by a coefficient multiplier 37, and the output signal of the logarithmic amplifier 33 is multiplied by a coefficient The output signals of the device 37 are added together.

Similarly, a positive/negative determining section 39 determines whether the output signal of the subtracter 25 is positive or negative, and the output signal of the positive/negative determining section 39 is inverted by an inverter 40 . and subtractor 25
If the output signal is positive, it is sent to the logarithmic amplifier 42 via the gate 41 based on the output signal of the positive/negative determining section 39, and if it is negative, it is inverted by the inverting circuit 43 and then passed through the gate 44 based on the output signal of the inverter 40. The signal is then sent to the logarithmic amplifier 42. Further, the output signal of the logarithmic amplifier 36 is multiplied by a coefficient by a coefficient multiplier 46, the output signal of the logarithmic amplifier 42 is added to the output signal of the coefficient multiplier 46 in an adder 47, and the output signal of the adder 38.47 is added. A signal is output as a measurement signal indicating the optical axis movement distance of the laser beam.

17 and 18 show actual measured values of the relationship between the amount of optical axis deviation and the difference signal in the Figures 19 and 20 show the aperture φ of the laser beam in the above embodiment.
The actual measured value of the relationship between the amount of optical axis deviation and the difference signal in the X direction and the two directions when = 1.08 is shown.

FIGS. 21 and 22 show the amount of optical axis deviation and the X direction when the aperture φ of the laser beam is φ=2.1 in the above example.
Figures 23 and 24 show actual measured values of the relationship with the difference signals in two directions, and Figures 23 and 24 show the aperture φ of the laser beam in the above example.
3.2, actual measured values of the relationship between the optical axis deviation amount and the difference signals in the X direction and the Z direction are shown.

25 and 26 show actual measured values of the relationship between the optical axis deviation amount and the difference signal in the X direction and the two directions when the aperture φ of the laser beam is set to φ=3.81 in the above embodiment.

FIGS. 27 and 28 show the relationship (correction curve) between the coefficients (difference signals in the X and Z directions/optical axis deviation amount) and the aperture of the laser beam for these actually measured values.

〔Effect of the invention〕

As described above, according to the invention of claim 1, there is a light splitting means that splits light into two, a four-split light receiving element that receives one of the lights from the light splitting means, and a four-split light receiving element that receives one of the lights from the light splitting means. Difference signals in two directions perpendicular to each other are obtained from the four output signals from the light receiving element for monitoring the light amount, which detects the amount of light, and the four-split light receiving element, and these difference signals are output from the light receiving element for monitoring the amount of light. Since it is provided with arithmetic means for correcting the amount of light according to the signal, accurate and highly accurate measurement is possible even when the amount of light changes, and furthermore, miniaturization is possible.

According to the second aspect of the invention, there is provided a light splitting means for splitting light into two, a four-split light receiving element for receiving one of the lights from the light splitting means, and an aperture of the other light from the light splitting means. and an optical aperture measuring means for detecting the aperture, and difference signals in two directions perpendicular to each other are obtained from the four output signals from the four-split light receiving element, and these difference signals are applied to the aperture by the output signal of the optical aperture measuring means. Since it is provided with calculation means for correcting accordingly, it is possible to perform accurate and highly accurate measurements, and furthermore, miniaturization is possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a plan view showing a four-division light receiving element of the same embodiment. Fig. 3 is a block diagram showing the arithmetic circuit of the same embodiment, Fig. 4 is a characteristic diagram showing the relationship between light intensity and correction coefficient of the same embodiment, and Fig. 5 is a timing chart showing signal waveforms of various parts of the same embodiment. The chart, FIG. 6, shows the amount of laser light, correction coefficient,
Figures 7 to 12, which show the relationship between the measured values of the optical axis movement of the laser beam, show the relationship between the optical axis movement of the laser beam and the difference signals in the X and Z directions at each light intensity in the same example. 13 and 14 are characteristic diagrams showing the relationship between the amount of laser light and the coefficient in the same embodiment, FIG. 15 is a block diagram showing another embodiment of the present invention, and FIG. FIGS. 17 to 26 are block diagrams showing the arithmetic circuit of the same embodiment. FIGS. 28 and 28 are characteristic diagrams showing the relationship between the coefficient (X direction, difference signal in two directions/optical axis deviation amount) and the aperture of the laser beam in the same embodiment. 12... Half mirror 113... 4-division light receiving element,
14... Light receiving element for light amount monitoring, 15... Arithmetic circuit, 28... Light receiving element for light aperture monitoring, 29...
Arithmetic circuit. Also Figure 9 Quantity 2 = Fu- Dust Diagram

Claims (1)

[Scope of Claims] 1. A light splitting means for splitting light into two, a four-split light receiving element for receiving one of the lights from the light splitting means, and a light receiving element for receiving one of the lights from the light splitting means, and a light amount of the other light from the light splitting means. Difference signals in two directions perpendicular to each other are obtained from the four output signals from the light receiving element for monitoring the amount of light to be detected and the four-division light receiving element, and these difference signals are used to calculate the amount of light using the output signal of the light receiving element for monitoring the amount of light. An optical axis movement measuring instrument characterized by comprising: arithmetic means for correcting according to. 2. A light splitting means for splitting light into two, a 4-split light receiving element for receiving one light from the light splitting means, and a light aperture measuring means for detecting the aperture of the other light from the light splitting means. and calculating means for determining difference signals in two directions perpendicular to each other from the four output signals from the four-split light receiving element and correcting these difference signals according to the aperture using the output signal of the optical aperture measuring means. An optical axis movement measuring instrument characterized by comprising: