JPS61247910A - Distance measuring method - Google Patents

Abstract

PURPOSE:To automate and speed up measurement by measuring the distance to the face to be measured from a focusing signal obtained at the condensing position. CONSTITUTION:The position and the focusing signal are in the good linear relation corresponding to the prescribed condensing position of a ring beam 14. Consequently, a condensing position ring beam 14 having a measuring range which enables to detect the position of an object 9 to be measured can be condensed by changing the condensing position to P1, P2, P3... and shifting the measuring range to A1, A2, A3... by using a focusing distance variable lens or the like. In other words, when the condensing position of the ring beam 14 is changed in order and the polarity of the focusing signal F is identified, since the polarity is changed between two condensing positions where the condensing lens 8 side and its opposite side approach the object 9 to be measured most via the object 9 to be measured, one side at least of two condensing positions makes the optimum condensing position at the measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a measuring method in a distance measuring device using a 1-yen convergent light beam.

(2) Prior Art Conventionally, there is a Japanese Patent Application No. 59-242490 filed by the applicant of the present invention regarding an optical distance measuring device. The distance measuring device proposed here is shown in FIG. In the figure, 1 is a laser light source, 2
is a collimator lens, 3 is a first conical mirror, 4 is a second conical mirror, and 5 is a variable focal length lens.

6 is a polarizing beam splitter, and 17 is a wavelength plate.

8 is a condensing lens, 9 is an object to be measured, 10 is a focus detection means,
11 is a processing device.

The laser light emitted from the laser light source 1 is turned into a flat beam by the collimator lens 2 and then passes through the first conical mirror 3. An annular light beam (hereinafter referred to as "light beam") whose center part is dark passes through the second conical mirror 4.

(referred to as a ring beam). This ring beam is formed by a variable focal length lens 5. Passes through polarizing beam splitter 6,
After the linearly polarized light is converted into circularly polarized light, it is projected onto an object to be measured 9 via a condenser lens 8 . The beam reflected by the upper surface of the object to be measured 9 is circularly polarized by the wavelength plate 7 through the condensing lens 8t, and then is reflected by the polarizing beam splitter 6. It is deflected and projected onto the focus detection means 10.

FIG. 2 shows the light-receiving surface of the focus detecting means 10, in which one annular ring sensor 12, 15 forms concentric circles.

The ring beam projected onto the focus detection means 10 changes its beam diameter according to the positional relationship between the focal position of the ring beam and the object to be measured 9, so that the focal position of the ring beam is on the upper surface of the object to be measured 9. When the ring sensors 12 and 1 match
By setting the beam diameter and the diameter of the ring sensors 12 and 13 so that the outputs obtained from each of the sensors 5 and 5 are equal, the change in the focusing state according to the position of the object to be measured 9 can be controlled by the ring sensor 1.
It can be detected by the output difference of 2.13. As shown in FIG. 3, the focus signal (usually the output difference of the ring sensors 12 and 13 normalized by the output sum) indicating the position of the object to be measured 9 and the focus state M is within a predetermined measurement range. A good linear relationship is maintained in the concavity.

Therefore, when performing all measurements using such a device, it is necessary to know the approximate location of the object to be measured in advance, or to place the object itself within a predetermined measurement range, which reduces measurement time. I can't.

Automation is also difficult and rare. Also, since the focal position of the ring beam with the best detection sensitivity is not known during measurement, it is virtually impossible to measure under the best conditions.

The measurement accuracy was also not sufficiently reliable.

(3) Summary of the invention The object of the present invention is to solve the above-mentioned drawbacks of the conventional art.

The object of the present invention is to provide a distance measuring method that can automate and speed up measurement.

In order to achieve the above object, the distance measuring method according to the present invention sequentially changes the focusing position of the ring beam at predetermined intervals, and uses a focusing detection means to detect the ring beam reflected on the surface to be measured. from two light condensing positions before and after the polarity of the focus signal obtained by the focus detection means changes.

A light focusing position having the surface to be measured within a measurement range in which the position of the surface to be measured and the focusing signal have a substantially linear relationship is determined, and the focusing signal is determined based on the focusing signal obtained at the focusing position. It is characterized by measuring the distance to the measurement surface.

The focus detection means usually has a ring sensor divided into two parts, an inner and an outer ring sensor, and calculates the output difference between the outer and inner parts of the ring sensor, or the output difference between the outer and inner parts of the ring sensor. The value normalized by is used as the focus signal.

With the change in the focusing position of the ring beam.

Compare the inner output of the ring sensor when the polarity of the focusing signal changes with the outer output of the ring sensor before the polarity of the focusing signal changes, or compare the output of the outer ring sensor when the polarity of the focusing signal changes, or The output from the outside of the ring sensor at 9 o'clock when the polarity changes is compared with the output from the inside of the ring sensor before the polarity of the focusing signal changes.

The distance to the surface to be measured can be measured using the focusing signal with the larger output.

If the measurement is carried out according to the method described above, the optimum light focusing position can be automatically detected and the distance to the surface to be measured can be measured at the mosquito light focusing position.

The basic principle of the distance measuring method according to the present invention will be explained below.

FIG. 4 is a detailed explanatory diagram of the present invention, in which the same members as in FIG. 1 are designated by the same numbers. In addition, 14 is a ring beam Ii! condensed by the condensing lens 8! ,,P2. P, are each condensing position of the ring beam 14 when changing the focal length of the optical system, M1. 2゜゜゜〜　　　　　　　　　　　　　　　　　　　　　　　　,P2　　　　　　　　　　　,P2　　　? ,
The measurement range is shown below.

In the apparatus shown in FIG. 1, as described above, there is a good linear relationship between a predetermined focusing position of the ring beam 14 and a focusing signal. Therefore, by using a variable focal length lens or the like, the focusing position is changed to P, , P, , P, . . . , and the measurement range is adjusted to 1. Mu3. By shifting the ring beam 14, the ring beam 14 can be focused on a focusing position having a measurement range in which the position of the object 9 to be measured can be detected.

For example, let the outputs from the ring sensors 12, 13 as shown in FIG. 2 be D, , D, respectively.

The focus signal is the difference signal D2-D, and the intensity signal is +D.

The value standardized by ? , that is, it can be expressed as. At this time, when the condensing position of the ring beam 14 is sequentially changed from the condensing lens 8 side as shown in FIG. Lens 8 and object to be measured 9
When the beam is between the two, the beam diameter is expanded and enters the condenser lens 8, and the condensing lens 8 converges the beam, so the beam is projected onto the ring sensors 12 and 15 with a smaller diameter than when focused. . Therefore, when the beam is on the opposite side from the lens 8, the beam diameter becomes smaller and enters the condensing lens 8, and becomes a diverging light by the condensing lens 8, so the beam diameter is smaller than when focused. becomes larger and is projected. Therefore, the value of 1 in-focus signal 1 is 51>0 according to equation (1). That is, the ring beam 14
Sequentially change the focus position and send the focus signal! If we determine the polarity of At least one of the two light focusing positions becomes the optimum light focusing position for measurement.

In the above description, the condensing position is sequentially changed from the condenser lens 8 side, but it may be sequentially changed from the side opposite to the condenser lens 8 via the object to be measured 9t. Further, it is preferable that the measurement ranges determined with each light collection position as the center are continuous, and it is acceptable for adjacent measurement ranges to partially overlap. Furthermore, in the above explanation, a standardized value is used as the focus point, but simply the difference signal D
2-D may be used as a focusing signal, or a difference signal may be used, and the value of -D2 may of course be used. However, when using the value of -D2 as a difference signal, the relationship between the object to be measured and the in-focus signal is 1% [contrary to that shown in Fig. 5, the relationship is a straight line sloping upward to the left; The way the focus signal changes in front and behind the object is also reversed.

Hereinafter, the present invention will be explained in detail with reference to Examples.

(4) Fruitful Example FIG. 5 shows a flowchart of the distance measuring method according to the present invention.

The apparatus shown in FIGS. 1 and 2 will be considered as an apparatus for measuring the distance to a surface to be measured by applying the distance measuring method shown in this embodiment. here.

It is assumed that the focal length variable lens 5 can change the focusing position in p distance NO steps, and the two focusing positions closest to the surface to be measured, and the focusing position on the side of the focusing lens B are set. Among the ring-shaped sensors, 111112. Outside 41111
The outputs of 3 are respectively ff, , D'2. Also, the inner side 12 of the ring sensor at the focal position opposite to the condenser lens 8. The outputs of the outer side 15 are each D1 #"2. Furthermore, it is assumed that the outputs are in focus.

First, the ring beam is focused at the focal length closest to the condenser lens 8, and detection of the focus signal 1 is started. ? >O1, that is, the focal length is increased by +N by the variable focal length lens 5 until the convergence position of the ring beam is on the opposite side of the surface to be measured from the condenser lens 8, and each time the focus signal r is The polarity is determined and the output signal of the ring sensor 12 at the condensing position when IP>0 is stored.

Next, move -N away from the focal point when F>OK (I
position (close to the condenser lens).

The output signal D'2 of the ring sensor 13 at this time is stored.

Here, the magnitude ratio of the stored output signal RI and D- is 112
If D1≦2, the distance to the surface to be measured obtained from the focus signal 1 and the focal length at the current 1×0 condensing position is taken as the measured value. If D1>Dl2, then the current state again? The ring beam is focused at a position 5-1-N below the focusing position, which is <0, and the distance l to the surface to be measured obtained from the focusing signal y and focal length at this focusing position is
Let @I be the measured value. In addition, like this 1k D11! :D
The comparison with '2 is based on the measurement target that is closer to the surface to be measured out of the two light focusing positions via the surface to be measured and within the measurement range centered on the light focusing position (see Figure 3). This is done in order to detect the optimum light convergence position that includes the surface.

FIG. 6 shows another 70-chart diagram of the distance measuring method according to the invention. As the apparatus to which this method is applied, the apparatus shown in FIGS. 1 and 2 is considered as in the previous embodiment, and the amount of change in the focusing position N, the output signals of the ring sensors 12 and 13, , D2
．． D', .

Dl2. , focus signal 1, etc. are all treated as the same as in the previous embodiment.

First, start the device and receive a focusing signal from the ring sensors 12 and 13 at any light focusing position! Detect. Here, P
It is determined whether the current condensing position of the ring beam is on the condensing lens 8 side or on the opposite side when viewed from the surface to be measured.

When the focus signal F) is O, the focusing position of the ring beam is on the opposite side of the focusing lens 8 when viewed from the surface to be measured, so the focusing position is changed by -N from the current position to gradually focus. Bring it closer to the optical lens 8. At this time, the polarity of the focusing signal F is determined for each focusing position. F) If O, repeat this determination and P
(The output signal D'2t of the ring sensor 13 at the 9 o'clock condensing position when the temperature becomes O is stored.

Next, the ring beam is again focused at a focusing position 10N away from the current position F0, and the output signal D1 of the ring sensor 1-2 at this focusing position is stored. Stored output signal D'2. D.

are compared in size, and if D1≧D'2, the measured value obtained from the focus signal F at this condensing position and the focal length is taken as the distance to the surface to be measured. or.

If T's > Dl then F(O from the current position -
Focus the ring beam to a position N away.

The measured value obtained from the focus signal F and the focal length at this condensing position is defined as the distance to the direction to be measured.

Next, if the polarity of the focusing signal 1 immediately after the device is activated is y<o, the focusing position of the ring beam is on the focusing lens 8 side when viewed from the direction to be measured, so the focusing position is increased by +N from the current position. , and gradually move it away from ψ1 to the condensing lens. At this time, the polarity of the focus signal 1 is determined for each focus position.

If y<o, manipulate this determination and return y>.

The output signal D1 of the ring sensor 12 at the condensing position when singing is stored. Subsequently, the ring beam is focused again to a focusing position separated by [-N from the current position where F>0, and the output signal D'2 of the ring sensor 5 at this focusing position is
remember. Stored output signal D+ t''2t - magnitude comparison.

If D'2≧D, is the focus signal at this focal position? Let the measured value obtained from the focal length and focal length be the distance to the surface to be measured. Also, if D, )D'2, the ring beam is focused at a position 10N away from the current position, and the measured value obtained from the focus signal 1 and focal length at this focused position is used as the measurement value on the surface to be measured. The distance to

Also, during the measurement, is the 1st focus signal r? If = 0, the surface to be measured exists at the convergence position of the ring beam, so immediately,
The position of the surface to be measured is detected and the ninth thing happens.

In addition, each measurement range obtained by successively L′- according to the change in the light arrival position for each circle 1@N has an overlapped area as a filter, and if a surface to be measured exists in the overlapped area, it is an aggregate with each measurement range. The distance to the surface to be measured may be detected using the focusing signal F at either of the optical positions.

Measurement using the method described above is automatically controlled by a microcomputer built into the processing device 11 in the apparatus shown in FIG. You can get it.

In the above two embodiments, the two optical positions closest to the surface to be measured are detected, and the outputs D1 and D' of the ring sensor are detected.
2t - After detecting the optimal focusing position by comparing p, measure the distance from 1 focusing signal F to the surface to be measured, or memorize the focusing signal 1 or the measured value at each focusing position. Then, after detecting the optimal focus position, select the memorized focus signal corresponding to that position. Alternatively, there is also a method of calling the measured value.

Therefore, various applications other than the above-mentioned embodiments are possible without departing from the spirit of the present invention.

In addition, this embodiment describes a method for measuring the distance to the direction to be measured, and can be applied to, for example, a gap measuring device that measures the distance between a mask and a wafer in a semiconductor device. You can measure the distance between the two provinces by measuring each distance and taking the difference.

(5) Detailed explanation of the invention and to our friends: The distance measuring method according to the present invention is capable of automatically detecting the optimum light focusing position during measurement, and is capable of detecting the optimum light focusing position at high speed. This is a measurement method that can measure the distance to the measurement surface.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an original distance turbidimetric device. FIG. 2 is a diagram showing a ring-shaped sensor. FIG. 3 is a diagram showing the relationship between the focus signal and the position of the surface to be measured. FIG. 4 is a diagram explaining the basic principle of the distance measuring method according to the present invention. FIGS. 5 and 6 are flowcharts showing an example of the distance measuring method according to the present invention. 1... Laser light source 2... Collimator lens 3... First conical mirror 4... Second conical mirror 5... Variable focal length lens 6... Polarizing beam splitter 7. . . . K wavelength plate 8 . . . Condensing lens 9 . . . Measured object 10 . . . Focus detection means 11 . . . Processing equipment 12.13 . . . Ring-shaped sensor 1. Mu2. M3...Measurement range 1'FP...Focusing position tt zt s

Claims (3)

[Claims] (1) The focusing position of the annular light beam is sequentially changed at predetermined intervals, the annular light beam reflected on the surface to be measured is detected by a focus detection means, and a focus signal obtained by the focus detection means is obtained. From two light focusing positions before and after the polarity changes, a light focusing position is determined that has the surface to be measured within a measurement range in which the position of the surface to be measured and the focusing signal have a substantially linear relationship. , a distance measuring method characterized by measuring a distance from a focusing signal obtained at the light condensing position to the surface to be measured. (2) The focus detection means has an annular sensor divided into two parts, an inner and an outer part, and the difference in output between the outside and the inside of the annular sensor, or the output difference between the outside and the outside of the annular sensor. The value normalized by the sum of the inner outputs is defined as the focusing signal, and the inner output of the annular sensor when the polarity of the focusing signal changes and the circle before the polarity of the focusing signal changes. The distance measuring method according to claim (1), characterized in that the distance from the in-focus signal with the larger output to the surface to be measured is measured by comparing the output with the outer output of the annular sensor. . (3) The focus detection means has an annular sensor divided into two parts, an inner and an outer part, and the output difference between the outside and the inner part of the annular sensor is detected, or the output difference is transferred to the outside of the annular sensor. and the value normalized by the sum of the inner outputs is defined as the focus signal, and the output of the outer side of the annular sensor when the polarity of the focus signal changes and the value before the polarity of the focus signal changes. Distance measurement according to claim (1), characterized in that the distance from the focused signal having the larger output to the surface to be measured is measured by comparing the output from the inner side of the annular sensor. Method.