JPH07117412B2 - Distance measuring method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an astigmatic distance measuring method and apparatus, which is one of the methods for measuring the distance to a point to be measured by measuring the degree of focusing.

[0002]

2. Description of the Related Art Conventionally, an absolute distance to a measured point or a moving distance (that is, a displacement amount) of a measured point itself from a reference position.
The astigmatism method is well known as a method of measuring.

The principle of this method will be described with reference to FIG. In the figure, P is a measured point located on the optical axis 1, and the light flux from this measured point P is guided to the light receiving element 4 through the objective lens 2 and further the cylindrical lens 3. Here, since the astigmatism is generated by passing the light beam bundle through the cylindrical lens 3, when the measured point P is at a predetermined reference position P _O , the image projected on the light receiving element 4 is as shown in FIG. Although it becomes a circle 5 as shown in b), when the measured point P is on the optical axis 1 at a position P _S closer to the objective lens 2 than the reference position P _O , it is projected on the light receiving element 4. The image is shown in Figure 8 (a).
When the measured point P is located on the optical axis 1 at a position P _L farther from the objective lens 2 than the reference position P _O , the image projected on the light receiving element 4 is as shown in FIG. A vertically elongated ellipse 7 as shown in FIG. Therefore, by reading such a change in the image with the light receiving element 4 whose light receiving surface is divided into a plurality of parts (for example, divided into four), it is possible to measure which position the measured point P is based on the reference position P _O. It becomes possible to do.

When actually using the measuring method based on the principle of such astigmatism, in order to reduce the error due to the change in the amount of received light, the obtained data is divided by the total amount of received light, or the total amount of received light is constant. The amount of light emission is controlled so that However, during measurement when the actual measured point is located on a curved surface with a relatively large inclination such as a turning surface or on a step with a sharp edge, due to the influence of the diffraction image, etc. Since very high-intensity light is incident on the beam, the amplitude of the cross-sectional curve of the surface to be measured may be measured several times to several tens of times larger than it actually is. That is, in the measurement by the simple astigmatism method, the surface state of the surface to be measured, in other words, is greatly affected by the variation in the light intensity distribution of the received light flux, so that it is difficult to always perform high-precision measurement. Has become.

Therefore, in JP-A-62-2109 and JP-A-62-2110, a light receiving line bundle from a point to be measured is divided into two directions by a beam splitter, and one light beam bundle is separated from the conventional one. Similar to the point aberration method, the light beam is incident on the first four-division light receiving element through a cylindrical lens, and the other light beam is passed through another cylindrical lens which is arranged by rotating 90 ° relative to the cylindrical lens and the second cylindrical lens. It is incident on the split photodetector and the first 4
The calculated value S _A = {(A1 + A3)-(A2 + A4)} / (A1 + A2 + A3 + A4) obtained from the outputs A1, A2, A3, A4 of the divided light receiving element and the outputs B1, B2, B3 of the second four divided light receiving element. B
By taking the differential output S _g (= S _A −S _B ) with the calculated value S _B = {(B1 + B3) − (B2 + B4)} / (B1 + B2 + B3 + B4) obtained from 4, the above-mentioned influence can be reduced. What has been done has been disclosed.

[0006]

According to the above method, the intensity is locally high (or low) only on a specific light receiving surface.
When light is incident, the adverse effect of this light beam on the measurement accuracy can be mitigated. However, it is extremely difficult to completely eliminate such adverse effects, and development of a method and an apparatus that can further improve the measurement accuracy has become a major issue.

In view of such circumstances, the present invention completely cancels the influence of the variation in the light intensity distribution of the light flux emitted from the measured point to perform highly accurate distance measurement. An object of the present invention is to provide a distance measuring method and device capable of performing the distance measurement.

[0008]

According to the present invention, a light beam received from a point to be measured on the optical axis is applied to a four-division light receiving element through at least an objective lens and a cylindrical lens, and based on the output of this light receiving element, In an astigmatic distance measuring method for measuring the distance of a measurement point, the beam bundle is passed through an objective lens and then split into two directions by a beam splitter, and one of the split beam bundles is passed through a cylindrical lens to produce a first beam. And the other light flux is made incident on the second four-divided light receiving element without passing through the cylindrical lens, and the sensing outputs A1, A2, A2 of the first four-divided light receiving element at this time.
A3, A4 and their sensing outputs A1, A2, A3, A
The value S = (A1 + A3) / (B1 + B3)-(A2 + A4) / (B2 + B4) given by the sensing outputs B1, B2, B3, B4 of the second 4-division light receiving element corresponding to 4 is calculated. The distance of the measured point is calculated based on this value S.

Further, the present invention is an apparatus for realizing the above method, which comprises a light source for irradiating a measured point with a light beam, an objective lens for passing a ray bundle reflected at the measured point, and this objective lens. A beam splitter that splits a bundle of passing light rays into two directions, and a first four-divided light receiving element and a second four-divided light receiving element that are provided at positions where the respective light bundles split by the beam splitter are incident, respectively. , A cylindrical lens provided between the first four-division light receiving element and the beam splitter, and sensing outputs A1, A2 of the first four-division light receiving element.
A3, A4 and their sensing outputs A1, A2, A3, A4
Output B of the second four-division light receiving element corresponding to
1, B2, B3, B4, and the distance calculation means for calculating the distance S of the measured point based on the value S.

[0010]

According to the above construction, one of the light beams split in two directions by the beam splitter is incident on the first 4-division light receiving element through the cylindrical lens, and the other light beam is transmitted through the cylindrical lens. Since the light is incident on the second four-division light receiving element without passing through it, if the light intensity distribution of the light beam has variations, the intensity is extremely high (or low) only on a specific surface of the first four-division light receiving element. When a light ray is incident, the light ray having high intensity (or low intensity) is similarly incident on the light receiving surface of the second four-division light receiving element corresponding to this light receiving surface. Therefore, as will be described later in detail in the section of Examples, when the optical axes of the respective parts are sufficiently aligned and the images incident on the four-divided photodetectors have sufficient symmetry, The sensing output A1, of the first four-division light receiving element
Ellipse major axis (or ellipse minor axis) of A2, A3, A4
Of the output values corresponding to (A1 + A3) and the output values corresponding to the minor axis of the ellipse (or the major axis of the ellipse) (A2
+ A4) divided by the sum (B1 + B3), (B2 + B4) of the sensing outputs of the second four-division light receiving element corresponding to each of them, the difference is obtained, that is, the value S = (A1 + A3) / By calculating (B1 + B3)-(A2 + A4) / (B2 + B4), the distance of the measured point can be calculated with high accuracy based on this value S.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method of the present invention will be described with reference to FIG.

First, as shown in the drawing, a light beam bundle 10 emitted from a measured point P located on the optical axis 1 is passed through an objective lens 12, and a beam splitter 14 moves in two directions (rightward and downward in the illustrated example). To divide. One of the divided light beam bundles 16 is passed through a cylindrical lens 18 to generate astigmatism, and then is made incident on each light receiving surface of the first four-divided light receiving element 20A. As a result, on the light receiving surface of the first 4-division light receiving element 20A, an elliptical or circular image as shown by the diagonal lines in the figure is formed according to the position of the measured point P, and each light receiving surface is individually provided. The sensing outputs A1, A2, A3, A4 are obtained. On the other hand, the other divided ray bundle 22 is made incident on each light receiving surface of the second four-division light receiving element 20B without passing through the cylindrical lens. This makes this second
On the light receiving surface of the four-divided light receiving element 20B, a circular image as shown by the diagonal lines in the figure is formed regardless of the position of the measured point P, and the outputs A1, A2, A
Sensing outputs B1, B2, B3, B4 corresponding to 3, A4 are obtained.

The four-divided light receiving elements 20A, 20
As B, for example, a four-divided photodiode or the like, which has four light receiving surfaces and which individually converts the amount of light received by each light receiving surface into an electric signal, is applicable. Further, in FIG. 1, a drawing is shown in which the respective light-receiving surfaces are tilted rearward as they are, further behind the respective four-divided light-receiving elements 20A, 20B.

In the above measurement operation, it is assumed that the light beam 10
It is assumed that a very strong (or weak) light beam (hereinafter, referred to as a peculiar light beam) 24 is mixed in a part of the above, and this peculiar light beam 24 is applied to a portion 26A that affects the sensing output A1 of the four-division light receiving element 20A. If it arrives, at the same time, the peculiar light ray 24 is always split into the beam splitter 14 and then reaches the portion 26B that affects the sensing output B1 of the second 4-split light-receiving element 20B. Therefore, no matter which light-receiving surface of the first 4-division light-receiving element 20A the unique light beam 24 is incident on, the optical axes of the components are sufficiently aligned, and the first 4-division light-receiving element 20A If sufficient symmetry is recognized in the projected image, the sum (A1 + A3) of the outputs corresponding to the ellipse major axis (or minor axis) among the output values A1 to A4 of the four-division light receiving element 20A of 1 , And the sum of outputs corresponding to the ellipse minor axis (or major axis) (A
2 + A4) is divided by the sum (B1 + B3) and (B2 + B4) of the outputs corresponding to the respective outputs, the variation in the light intensity distribution can be completely canceled out. Therefore, according to the following formula and formula, For example, the distance L from the objective lens 12 to the measured point P can be accurately calculated regardless of the variation in the light intensity distribution. L = F (S) ≈Lo + kS ... S = (A1 + A3) / (B1 + B3)-(A2 + A4) / (B2 + B4) ... In the equation, Lo is the reference distance, that is, the first 4
It is the distance from the objective lens 12 to the measured point P when the image projected on the divided light receiving element 20A is circular, and k is a proportional constant.

Next, it will be theoretically proved that the influence of the variation in the light intensity of the light bundle 10 is canceled by the calculation of the above equation.

First, the sensing outputs B1, B2, B3, B4 of the second four-division light receiving element 20B are proportional to the cross-sectional light intensity distribution and the light receiving area of the light receiving line bundle 10 from the measured point P, respectively. Since the light-receiving image is circular, it can be considered that the light-receiving areas of the respective light-receiving surfaces are all equal, and therefore the outputs B1 to B4 are proportional to only the sectional light intensity distribution. Therefore, the light intensities of the light receiving line bundles on the respective light receiving surfaces are set to b ₁ , b ₂ ,
If b ₃ and b ₄ and the proportional constant are k _B , then the respective outputs B1 to B4
The B1 = k _B b _1; can be expressed B4 = k _B b ₄ ... _{and; b 3 B3 = k B;} B2 = k B b 2.

On the other hand, the first four-division light receiving element 20A
Each sensing output A1, A2, A3, A4 in each, the light intensity _{b 1, b 2, b 3} , b 4 and is proportional to the light receiving area, each light receiving area _{a 1, a 2, a 3} , a _4, a proportionality constant is _{k a, A1 = k a a} 1 b 1; A2 = k a a 2 b 2; A3 = k a a 3 b 3; A4 = k a a 4 b 4 ... and be represented You can Here, when the optical axes of the respective parts are sufficiently matched and sufficient symmetry is recognized in the image projected on the first four-division light receiving element 20A, a ₃ = a ₁ ,
It can be set that a ₄ = a ₂ . Substituting this into the above equation gives: A1 = k _A a ₁ b ₁ ; A2 = k _A a ₂ b ₂ ; A3 = k _A a ₁ b ₃ ; A4 = k _A a ₂ b ₄ ... By substituting this equation and the above equation into the above equation, the following equation is obtained. S = (k _A / k _B ) (a ₁ −a ₂ ) ... As is apparent from this equation, the cross-sectional light intensity distribution b ₁ to
b ₄ is canceled out, and S is a function proportional to the difference between the light receiving areas a ₁ and a _2. Therefore, based on this S, the accurate distance L can be obtained by the above equation without being affected by the variation in the cross-sectional light intensity.
Can be calculated.

Further, as shown in FIG. 1, a diaphragm 28 having a circular opening of an appropriate diameter is provided in front of the beam splitter 14.
By disposing the unstable light ray bundle around the light ray bundle 10 to make the light ray bundles 16 and 22 reaching the four-divided light receiving elements 20A and 20B sharper, the measured values can be further stabilized. You can

Further, in FIG. 1, the light beam bundle 16 transmitted through the beam splitter 14 is passed through a cylindrical lens 18 and then made incident on the first four-division light receiving element 20A, and the beam splitter 1
Although the light beam 22 reflected by the beam splitter 4 is directly incident on the second 4-division light receiving element 20B, the light beam transmitted by the beam splitter 14 is directly incident on the 4-division light receiving element. Then, the light beam reflected by the beam splitter 14 may be passed through the cylindrical lens 18 and then incident on a four-division light receiving element different from the above-mentioned four-division light receiving element. In this case, the former four-divided light receiving element is used as the second four-divided light receiving element, and the latter four-divided light receiving element is used as the first four-divided light receiving element to perform the equations and calculations of the equations in the same manner as in the above-described embodiment, thereby accurately It is possible to find the appropriate distance.

Further, between the beam splitter 14 and the cylindrical lens 18 in FIG. 1 or between the cylindrical lens 18 and the four-divided light receiving element 20A, and between the beam splitter 14 and the four-divided light receiving element 20B, etc. By inserting a convex lens or a concave lens (neither of which is shown) having an appropriate focal length into each of the four split light receiving elements 20A and 20B.
It is also possible to set the position of each to a desired position on each optical axis.

Further, the measured point P from the objective lens 12 etc.
If it is desired to obtain the displacement amount (that is, the moving distance) u of the measured point P from the reference position, instead of the absolute distance L, the displacement amount u can be easily calculated by the following equation u = f (s) ≈kS. You can ask.

Next, an example of an apparatus suitable for carrying out the above method is shown in FIG.

This device is provided with a light source 30 composed of a laser light emitter or the like, and in front of it (on the left side in the figure), an aspherical lens 32, a concave lens 34, a pinhole 36, a polarization beam splitter 38, and λ / 4. Wave plate 40 and objective lens 1
2 are arranged in order. The polarization beam splitter 3
A diaphragm 28, a beam splitter 14, and a second four-division light receiving element 20B are sequentially arranged below the beam splitter 8, and a cylindrical lens 18 is provided behind the beam splitter 14 (to the right in the figure).
And the first four-division light receiving element 20A are sequentially arranged, and the above components are incorporated in a frame (not shown). The two 4-divided light receiving elements 20A, 20B are connected to an arithmetic processing unit (distance calculating means) 50, and the sensing outputs A1 to A4, B1 to B4 of the respective light receiving elements 20A, 20B are input to the arithmetic processing unit 50. It is like this.

The arithmetic processing unit 50 includes an arithmetic circuit as shown in FIG. 3 as an example. In the figure, 51 to 5
4 is an adder, 55 and 56 are dividers, 57 is a subtractor, 58
Is the operation output. With this circuit, the arithmetic processing unit 50
Is configured to calculate the value S shown in the above equation and calculate the distance L and the displacement amount u based on the value S.

Next, the operation of this device will be described.

A ray bundle 42 emitted from the light source 30 is converged by an aspherical lens 32, shaped into a ray bundle having a predetermined focal length by a concave lens 34, and then a pinhole 36 forms a sharp circular cross section. Of the light beam 43, the polarization beam splitter 38, the λ / 4 wavelength plate 40, and the objective lens 12
Then, the light is focused on the measured point P on the measured surface 44.
The light reflected at the measured point P becomes a bundle of rays 10 as if it were emitted from the measured point P itself, passes through the objective lens 12 and the λ / 4 wavelength plate 40, and is directed downward by the polarization beam splitter 38. Is reflected. After the unstable component is removed by the diaphragm 28, this beam bundle is beam splitter 1
At 4, it is divided into two directions, downward and backward. One of the divided light beam bundles 16 reaches the first four-divided light receiving element 20A after astigmatism is generated by the cylindrical lens 18, and the other light ray bundle 22 reaches the second four-divided light receiving element 20B as it is. Sensing outputs A1 to A4 and B1 of the respective light receiving elements 20A and 20B
B4 is input to the arithmetic processing device 50, and the signals regarding the values of the distance L and the displacement amount u calculated by the arithmetic processing device 50 are output to a display device (not shown), another arithmetic processing device, or the like.

Although not shown in FIG. 2, in order to reduce the influence of ambient light as much as possible, in the middle of the optical system,
For example, the light sources 3 are provided before and after the objective lens 12 and before and after the diaphragm 28.
It is necessary to insert an interference filter according to the emission wavelength of 0 or to modulate the light source 30 for use.

Further, in order to obtain a stable measurement result over the entire measurement range, the diameter of the measured point P is made as small as possible, and even if the measured point P moves back and forth with respect to the objective lens 12, Since it is desirable that the size of the measurement point P does not change, the light source 30 and the non-light source 30 are arranged so that the light beam bundle 43 passing through the objective lens 12 and reaching the measured point P has a cross-sectional diameter as small as possible and a parallel light beam bundle. Spherical lens 32, concave lens 3
4. It is desirable to appropriately determine the position of the pinhole 36 and the like, the focal length, the diameter and the like.

Further, in the case of forming a parallel light flux 43 having such a minimum cross section, the pinhole 36 shown in FIG.
Instead of using an expensive polarization beam splitter 38,
It is also possible to use an end plate 70 as shown in FIG.
This makes it possible to omit the expensive λ / 4 wave plate 40. The end plate 70 has a small through hole 72 inclined at 45 ° in the center, and therefore, the through hole 72 is formed.
The opening shape is a 45 ° ellipse. By disposing such a mirror 70 at the same position as the polarization beam splitter 38 in a state of being inclined by 45 ° as shown in FIG. 4, the light beam bundle 42 passes through the through hole 72 and the light beam bundle 42 passes. The bundle of rays 10 which has become 43 and is irradiated to the point P to be measured, reflected and returned, that is, the bundle of rays 10 whose cross-sectional area is much larger than the bundle of rays 43, is mostly the through hole. The light is reflected downward in the area other than 72 and is introduced into the beam splitter 14.

When such an end plate 70 is used,
As shown in FIGS. 5A to 5C and FIG. 5D, the first
Image 7 formed on the light receiving surface of the four-division light receiving element 20A
6, 77, 78 and a hollow portion 76 ', 77 in the center of the image 79 formed on the light receiving surface of the second four-divided light receiving element 20B.
′, 78 ′, 79 ′ are formed, but since the shapes of these hollow portions 76 ′ -79 ′ correspond to the shapes of the images 76-79, respectively, if the emission intensity is high to a certain degree, It has little effect on accuracy. However, the polarization beam splitter 3 as shown in the above embodiment
If the 8 and λ / 4 wave plates 40 are used, it is possible to almost completely prevent a part of the reflected light beam bundle 10 from returning to the light source 30, thereby further stabilizing the light emission of the light source 30. It is possible.

The present invention can be easily applied to an apparatus for irradiating a point to be measured with a ray from below, regardless of the direction of each ray bundle, in the same manner as in the above embodiment. .

Further, in the present invention, regardless of the type of beam splitter, in addition to the rectangular prism type shown in FIGS.
Various beam splitters that divide the light-receiving line bundle into two directions are applicable.

Further, the distortion of the objective lens 12 and the diaphragm 28
Even when perfect symmetry is not recognized in the image projected on the first four-division light receiving element 20A due to irregularity of the above, etc., the value S ′ shown in the following equation is replaced with the value S ′ shown in the following equation. By using, it is possible to suppress the adverse effect on the measurement result due to the impairment of the symmetry. S '= (A1 / B1 + A3 / B3)-(A2 / B2 + A4 / B4) ...' That is, this value S'represents the sensing outputs A1 to A4 corresponding to the sensing outputs of the second four-division light receiving element 20B. B
By dividing by 1 to B4, the influence of the peculiar ray 24 on the measurement accuracy is canceled out, and each ratio A1 / B1, A2 /
B2, A3 / B3, A4 / B4 are used to represent the degree of dimensional difference between the major axis and the minor axis in the first four-divided light receiving element 20A.

This equation is for the first four-division light receiving element 20.
The influence of the light intensity distribution is completely canceled regardless of the symmetry incident on A, and the proof will be given below. First, the outputs A1 to A of the first four-division light receiving element 20A
The output of the 4 and a second quarter-split light receiving element 20B B1 to B4 is the embodiment similarly to _{B1 = k B b 1; B2} = k B b 2; B3 = k B b 3; B4 = k B b 4 ... _{A1 = k A a 1 b 1} ; A2 = k A a 2 b 2; A3 = k A a 3 b 3; A4 = k A a 4 b 4 ... represented by. Substituting these into the above equation, the following equation is obtained. S ′ = (k _A / k _B ) {(a ₁ + a ₃ ) − (a ₂ + a ₄ )} ... ′ The value S ′ shown here is the same as the value S shown in the above formula, that is, the light intensity distribution. Irrespective of b _{1 to} b ₄ , the light receiving area a ₁ ,
It is a function of only a ₂ , a ₃ , and a ₄ , and is a value determined by the difference between the long axis and the short axis of the image received by the first 4-division light receiving element 20A. Therefore, it is obvious that even if this value S ′ is used, an accurate distance that is not affected by the light intensity distribution can be obtained. Further, in this equation, a ₃ = a ₁ , a ₄ = a ₂
Then, the following equation S ′ = 2 (k _A / k _B ) (a ₁ −a ₂ ) ... Is obtained, but this value S ′ is equivalent to the value S given by the above equation. it is obvious.

In order to carry out the operation of the above equation, for example, an operation circuit as shown in FIG. 6 may be used. In the figure, 61 to 64 are dividers, 65 and 6
6 is an adder, 67 is a subtractor, and 68 is a calculation output.

As is apparent from a comparison between FIG. 6 and FIG. 3, according to the arithmetic method shown in the equation,
It is possible to reduce the number of expensive dividers to two, which is half that of the operation method shown in the equation, and it is possible to reduce the cost accordingly. Also, if any of the sensing outputs B1 to B4 is extremely weak, an extremely unstable output can be obtained by the calculation of the equation where the output value is the denominator as it is. In the calculation method by the above formula,
Since the sum (B1 + B3) of the sensing outputs B1 and B3 and the sum (B2 + B4) of the sensing outputs B2 and B4 are denominators, respectively, even if any one of the sensing outputs B1 to B4 is extremely weak, There is almost no weakness up to the value, so the calculated output value can be made more stable.

However, according to the calculation method shown in the above equation, even if there is an error in the symmetry of the received light image, there is an advantage that it is possible to reduce the influence on the measurement result.

[0038]

As described above, according to the present invention, the light flux received from the measured point is passed through the objective lens and then split into two directions by the beam splitter, and one light flux is passed through the cylindrical lens to receive the first four-divided light. The other light flux is made incident on the second four-division light receiving element without passing through the cylindrical lens, and the sensor outputs corresponding to the sensing outputs A1 to A4 of the first four-division light receiving element and these sensing outputs, respectively. The distance of the measured point is calculated based on the value S = (A1 + A3) / (B1 + B3)-(A2 + A4) / (B2 + B4) given by the sensing outputs B1 to B4 of the second 4-division light receiving element. Therefore, even if there is a variation in the light intensity distribution of the light flux received from the point to be measured, the effect can be completely offset, and this has the effect of enabling highly accurate distance measurement.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical system for explaining an embodiment of a method of the present invention.

FIG. 2 is a configuration diagram showing an example of a distance measuring device for realizing the above method.

FIG. 3 is a diagram showing a circuit required for calculation in the above method.

FIG. 4 is a cross-sectional front view of an end plate that can be used as a substitute for the deflecting beam splitter in the distance measuring device.

5 (a), (b) and (c) are front views showing an image formed on the light receiving surface of the first four-division light receiving element when the above-mentioned end plate is used, and (d) is a case where the above-mentioned end plate is used. It is a front view which shows the image formed in the light-receiving surface of a 2nd 4-part dividing light receiving element.

FIG. 6 is a diagram showing a circuit required for calculation in another method.

FIG. 7 is a configuration diagram of an optical system for explaining the principle of the astigmatism method.

8A, 8B, and 8C are diagrams showing images formed on a light receiving surface of a four-division light receiving element due to astigmatism.

[Explanation of symbols]

 10 Ray bundle received from measured point 12 Objective lens 14 Beam splitter 18 Cylindrical lens 20A First four-division light receiving element 20B Second four-division light receiving element 30 Light source 50 Arithmetic processing device (distance computing means) A1 to A4 First Sensing output of 4-division light receiving element B1 to B4 Sensing output of second 4-division light receiving element P Point to be measured

Claims (2)

[Claims] 1. A non-measurement device for irradiating a four-division light receiving element with a light beam received from a point to be measured on an optical axis through at least an objective lens and a cylindrical lens and measuring the distance of the point to be measured based on the output of the light receiving element. In the point aberration type distance measuring method, the light beam bundle is passed through an objective lens and then split into two directions by a beam splitter, and one of the split light beam bundles is passed through a cylindrical lens and made incident on the first four-division light receiving element. At the same time, the other ray bundle is made incident on the second 4-division light-receiving element without passing through the cylindrical lens, and the sensing outputs A1, A2, A3, A4 of the first 4-division light-receiving element at this time and their detection The second corresponding to the outputs A1, A2, A3, A4, respectively
The value S = (A1 + A3) / (B1 + B3)-(A2 + A4) / (B2 + B4) given by the sensing outputs B1, B2, B3, B4 of the four-division light receiving element of is calculated, and based on this value S A distance measuring method, characterized in that the distance between the points to be measured is calculated. 2. A light source for irradiating a measured point with a light beam, and an objective lens for passing a bundle of light rays reflected at the measured point.
A beam splitter that splits a light beam that has passed through this objective lens into two directions, and a first beam splitter that is provided at a position where each light beam split by this beam splitter is incident.
The divided light receiving element and the second four-divided light receiving element, the cylindrical lens provided between the first four-divided light receiving element and the beam splitter, and the sensing output A1 of the first four-divided light receiving element.
A2, A3, A4 and their sensing outputs A1, A2, A
The value S = (A1 + A3) / (B1 + B3)-(A2 + A4) / (B2 + B4) given by the sensing outputs B1, B2, B3, B4 of the second 4-division light receiving element corresponding to 3 and A4, respectively, A distance measuring device comprising: a distance calculating unit that calculates and calculates the distance of the measured point based on the value S.