KR900008877B1 - Position detective device - Google Patents

Abstract

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Description

Position detection device

1 is a block diagram of a position detection apparatus in one embodiment of the present invention.

FIG. 2 is a detailed view of the slit portion of FIG. 1 in the first embodiment. FIG.

3 is a positional relationship diagram of Fraunhofer diffraction.

4 is a light intensity distribution diagram of a Fraunhofer diffraction image combining a regular array of identical openings and a spherical end opening.

5 is a relationship between S / F and maximum amplitude.

6 is a relationship between the minimum amplitude due to the change of a / d ₁ and L.

FIG. 7 is a detailed view of the slit portion of FIG. 1 in the second embodiment. FIG.

8 is a block diagram of a conventional photoelectric encoder.

9 is a relationship between the spacing and the amplitude of the slits of two equal lattice constants.

* Explanation of symbols for main parts of the drawings

11: laser diode 12: collimator lens

13: (moving) slit plate 14: (fixed) slit plate

15: photodetector (photodetector)

The present invention relates to a position detection device in a positioning device. BACKGROUND OF THE INVENTION Positioning devices that detect the rotation angle of a mechanical device with a position detection device and perform positioning of the mechanical device are well known. Photoelectric encoders are widely used as such position detection devices. An example of the conventional photoelectric encoder mentioned above is demonstrated, referring drawings below.

8 shows a conventional photoelectric encoder. In Fig. 8, reference numeral 1 denotes a light source, reference numeral 2 denotes a collimator lens, reference numeral 3 denotes a rotating disk, reference numeral 4 denotes a fixed mask, reference numeral 5 denotes a light receiving element, and reference numeral 6 denotes a waveform shaping circuit.

The operation of the photoelectric encoder configured as described above will be described below. The light beam radiated from the light source 1 becomes parallel light in the collimator lens 2, and is photoelectrically converted by the light receiving element 5 which has passed through the slit on the rotating disk 3 and the slit on the fixed mask 4 to form a waveform. The signal is output from the circuit 6. When the rotating disk 3 rotates in accordance with the rotation of the member, the slit on the rotating disk 3 and the slit on the fixed mask 4 coincide with each other and repeat the mismatch, thereby outputting a square wave signal from the waveform shaping circuit 6. The rotational position of the member is detected by detecting this signal.

As a light source of this kind of photoelectric encoder, a filament bulb and a light emitting diode have conventionally been used.

Scanning into such slits formed regularly and periodically on such a rotating disk must be maintained at a single specific distance between the rotating disk and the fixed mask.

When parallel light is transmitted through the slit of the rotating disk, a diffraction image is generated in the slit of the rotating disk by the interference of light diffracted by the slit of the rotating disk to a specific plane behind the slit plane of the rotating disk, and the diffraction image is the same lattice constant. Can be injected by the fixed slit of.

(n=0, 1 ,2…)를 가진다. 따라서 최적의 전기적주사신호는 회전디스크의 슬릿평면으로부터 고정마스크의 슬릿평면의 거리 n·

의 경우에 생기며, 오차가 ±0.1

되어야 한다[Machine Shop Magazine, 1962년 4월 208페이지].These planes are the distance n · from the slit plane of the rotating disk in the case of lattice constant P _M of the slit of the rotating disk and the wavelength λ of the light.

(n = 0, 1, 2 ...). Therefore, the optimal electric scanning signal is the distance n of the slit plane of the fixed mask from the slit plane of the rotating disk.

Occurs in the case of an error of ± 0.1

[Machine Shop Magazine, April 1962, page 208].

In Fig. 9, the amplitude of light modulation resulting from the relative motion between two equal lattice constant slits is shown with respect to the opposing distance a.

이며, 격자정수 P_M을 미소하게 하면 먼지등의 침입에 의한 슬릿의 오손 및 파손이 있었다.However, in the above structure, since the filament bulb and the light emitting diode as the light source have a large light emitting area, it is difficult to obtain a perfect parallel luminous flux, and because the parallelism of the luminous flux is poor, and the wavelength band of the light emission is wide, the diffraction image of the slit of the rotating disk is wide. On this fixed mask, it becomes blurred, so that the distance L between the rotating disk and the fixed mask cannot be increased.

When the lattice constant P _{M was made} to be small, the slits were damaged and damaged due to the intrusion of dust or the like.

에서는 광변조의 진폭은, 대략 0으로 저하하게 되어 L의 변화에 따라 정형파형상 신호도 크게 변화하게 되어, 고안정의 위치검출을 행하기 위하여는 L의 변화를 작게 억제할 필요가 있었다.In addition, the transmission part of the light of the slit with respect to the lattice constant is generally 1/2 or less and often takes a value of 0.45 to 0.5, and L = (n-1 / 2).

In this case, the amplitude of the light modulation is reduced to approximately 0, and the square wave signal also changes greatly with the change of L. In order to detect the position of the high crystal, it is necessary to suppress the change of L small.

In the conventional photoelectric encoder, in order to solve the above problems, the flatness of the rotating disk is improved and the precision of the rotating disk bearing is reduced, thereby suppressing the change of L, thereby miniaturizing and increasing the resolution.

In order to keep the change of L small, it was difficult to use for general industrial use because it was configured as a precision measuring instrument by strictly limiting the use temperature condition and the load condition for the rotating disk bearing.

In addition, a light beam having a relatively high degree of parallelism is obtained by a filament bulb having a high amount of light and a long focal collimator lens, which suppresses the effect of blurring the slit diffraction image, increases the change in L, and achieves high resolution. The filament bulb to obtain the light amount is difficult to use for general industry because the illumination system is enlarged by using a long focal lens to obtain a light beam having a weak vibration, short life and high parallelism.

In the above-described conventional example, due to the constraints of the configuration of the mechanism, it has been difficult to miniaturize and high resolution for general industrial use.

The present invention is to provide a small size and high resolution position detection device that can be used as a general industrial in view of the above problems.

d₁/2L로 하고, 광원쪽의 슬릿판상의 슬릿의 폭 a이 a

d₁/2의 주기적 슬릿에 의해 생기는 프라운호퍼 회절상의 명암줄무늬를 광검출기로 검출한다고 하는 구성을 구비한 것이다.In a first aspect of the present invention for solving the above problems, in the photoelectric position detection device, a laser light source is used as a light source, and the relationship between the size S of the light emission source of the laser light source and the focal length F of the collimator lens is S. FIG. / F

d ₁ / a 2L, and the width a of the slit plate of the light source side a slit

The light streaks on the Fraunhofer diffraction formed by the slit of d _1/2 are provided with a photodetector.

d₂/L로 하고, 광원쪽의 슬릿판상의 슬릿폭 a을 a

d₂/2L로 하고, 광원쪽의 슬릿판상의 주기적 슬릿과 광검출기쪽의 슬릿판상의 주기적 슬릿간의 거리를, 상기 광원쪽의 주기적 슬릿의 프라운호퍼 회절상의 0차의 주극대(主極大)와 1차의 주극대의 간격은 상기 주기적 슬릿의 슬릿간격의 정수배이고, 또한 상기 프라운호퍼 회절상의 주극대의 폭은 상기 광검출기쪽의 주기적 슬릿의 슬릿간격의 1/2이하로 하고, 상기 광원쪽의 주기적 슬릿의 슬릿간격의 정수분의 1의 슬릿간격으로 설정된 상기 광검출기쪽의 주기적 슬릿을 개재해서, 상기 프라운호퍼 회절상의 명암줄무늬를 광검출기로 검출한다고 하는 구성을 구비한 것이다.In the second aspect of the present invention, a laser light source is used as the light source, and the relationship between the size S of the light emitting source of the laser light source and the focal length F of the collimator lens is S / F.

Let d ₂ / L and set the slit width a on the slit plate on the light source side to a

The distance between the periodic slit on the slit plate on the light source side and the periodic slit on the slit plate on the photodetector side is d ₂ / 2L, and the zero-order main band on the Fraunhofer diffraction of the periodic slit on the light source side and 1 The interval between the main poles of the difference is an integer multiple of the slit gaps of the periodic slits, and the width of the main poles on the Fraunhofer diffraction is less than 1/2 of the slit gaps of the periodic slits on the photodetector side, and the periodicity on the light source side The photodetector detects light and dark stripes on the Fraunhofer diffraction via a periodic slit on the photodetector side, which is set to a slit interval of an integer number of slit intervals of the slit.

According to the first aspect of the present invention, a high-quality parallel beam is obtained by a laser light source and a collimator lens, and a zero-order main pole having a large Fraunhofer diffraction image of a periodic slit due to coherence of the laser light is obtained. As a result, the sharpness of the contrast stripes increases and the bright portion becomes a sharp beam shape, so that the distance between the slit plate and the photodetector can be increased, making it possible to easily downsize and high resolution.

The action of the second invention of the present invention is to reduce the spacing of the two slit plates while the bright portion becomes a narrow, sharp beam shape while obtaining the zero-order main pole having a large Fraunhofer diffraction image of the periodic slit. Without this, high resolution can be achieved only by reducing the interval of the periodic slits on the slit plate on the photodetector side, and further miniaturization and high resolution can be easily performed.

According to the present invention, there is provided a laser light source (11) and (12) having at least one coherence and parallelism, a first slit means (13) having a periodic slit having a position to which the laser light is irradiated, and the first Second slit means (14) having periodic slits disposed at a distance obtained by transmitting light waves having interfering in-phase differences occurring between optical signals passing through at least two or more periodic slits of the first slit means; Slit means having a photodetector 15 arranged at a distance for detecting the total amount of interference light generated by at least two periodic slits; By arranging the second slit plate having periodic slits at a distance that transmits only the light waves having diffraction and interference phase difference caused by the diffraction and interference, the distance between the first slit plate and the second slit plate is increased. As a technique, an assembly requiring a precision of about 10 to 20 μ was required to be arranged at intervals of 200 μ or more, so that the assembly could be made considerably easier. 회절 Diffraction caused by the periodic slit on the second slit plate and Since the total amount of light in the interference phase is detected by a photodetector, and light is detected using only the particulate properties in the light wave and particle, there is no influence due to the interference of light, which is a problem in the detection using general light, and stable output is achieved. Obtained.

In addition, the present invention forms a second slit means for transmitting only light waves having a phase difference of diffraction interference phase, so that all light waves having the same phase difference from the entire interference image (that is, portions having the same brightness) are transferred to the photodetector. The amount of received light is high, and the S / N of the output signal is good.

EMBODIMENT OF THE INVENTION Hereinafter, 1st Example of this invention is described, referring drawings.

1 is a block diagram of a position detection device in an embodiment of the present invention.

In Fig. 1, reference numeral 11 denotes a laser diode, reference numeral 12 denotes a collimator lens, reference numeral 13 denotes a movable slit plate, reference numeral 14 denotes a fixed slit plate, and reference numeral 15 denotes a photodetector element.

The operation of the optical portion of the position detection device configured as described above will be described below.

First, the light emitted from the light emitting surface of the laser diode 11 becomes a parallel light beam in the collimator lens 12 to irradiate the moving slit plate 13.

As shown in FIG. 2, on the movable slit plate 13, a plurality of slits 16 having an opening width a are arranged side by side at an interval d ₁ , and light is transmitted through the slit 16. Light blocked by other parts and transmitted is irradiated to the fixed slit plate 14.

In this case, the Fraunhofer diffraction image having the wavelength? Transmitted through the slit 16 is regularly arranged with a plurality of slit openings having the same spherical shape in the slit 16. It is a combination of spherical end openings.

Direction of the slit 16 is parallel to third degrees of the y is the center of the regularly disposed side by side to have a predetermined distance d ₁ in the X-axis. A light source S is parallel to the Y ₁ axis in the plane X ₁ -Y _1, and when the center of a slit in the X ₁ axis, diffraction image P has a central axis and the X ₂ by the thin lines parallel to a Y ₂ axis, and The intensity distribution I (P) of the diffraction image

I (P) = Io (P ) │F (P) │ 2 ... … … … … … … … … … … … … … … … … … … … (One)

It becomes Io (P) is the intensity distribution of the diffraction image at the spherical end opening.

F (P) | ² is a relative intensity distribution of diffraction images when they are sequentially arranged side by side with a spacing of d _{1 on} the X axis from N identical openings and the first opening at the origin,

As is, to the fourth light source it is a monochromatic light source is drawn for a wavelength λ, the I (P) of equation (1) as a function of │F (P) │ ² of the _first d (sinθ ₁ + sinθ ₂₎ ( Reference: Optical Technology Handbook [Asakura Bookstore, Japan]).

In the light source, since the laser diode 11 and the collimator lens 12 are used as parallel beams, Equations (3) and (5) are respectively

The condition that the main pole comes out is

dsin θ ₂ = m λ (m = 0, ± 1, ± 2). … … … … … … … … … … … … … … … … (8)

Becomes

The width of the main pole is 2 / N of the gap of the main pole. As N increases, the main pole becomes thinner and the edge becomes sharper. As shown in Fig. 4, the dotted line connecting the main poles of each order of | F (P) | ² represents the distribution of Io (P) of the spherical end opening.

The Fraunhofer diffraction image of the slit 16 obtained as described above is projected onto the fixed slit plate 14.

As shown in FIG. 2, on the fixed slit plate 14, a plurality of slits 17 having an opening width b are arranged side by side at an interval d ₂ in which d ₂ = d ₁ , and light is slit. Part 17 is transmitted, light is shielded at the other part, and the transmitted light irradiates the photodetector 15.

At this time, when the spacing of the main pole of the Fraunhofer diffraction projected on the fixed slit plate 14 coincides with the spacing d ₂ of the slit 17 arranged side by side on the fixed slit plate, When the maximum peak is in the slit 17, the amplitude of the detection signal output from the photodetecting element 15 is maximized in accordance with the movement of the movable slit plate 13. However, the spacing of the main poles in the diffraction phase of the Fraunhofer is an inequality interval that increases as the order increases on the rigid fixed slit plate. The order is determined. As a factor in determining the practical allowance and the ratio of the distance d ₁ and a aperture width of the slit 16, it is a typical example, d ₁ ≒ 2a. At this time, the intensity of the second or more main poles is about 1/22 or less with respect to the zero-order main pole, ignoring the second or more main poles, and the peaks of the zero and first pole poles are the slits (17). If within the amplitude of the detection signal is sufficient to detect.

The size of the main maximum of the Fraunhofer diffraction image gakcha is determined by the ratio of the distance d ₁ and a aperture width of the slit 16 as shown in FIG. 4. One or more difference to the main maximum of the zero-order main maximum is, the smaller the d ₁ / a becomes smaller, the smaller the d ₁ / a, that is, to bypass the main maximum of the lower-order The larger the a.

Another factor that determines practical tolerance is the size S of the light source. In FIG. 3, the light source S is regarded as a point light source. However, practically, a light source having a size S is optically infinity with a collimator lens having a focal length F. Therefore, the light source may be considered as a set of point light sources, and may be considered to be a point light source distributed in an angular range of S / F at infinity, and the resulting Fraunhofer diffraction image of the slit 16 is approximately S / F. It has an enlargement angle of F.

Apart from the above factors, a change in the spacing between the movable slit plate 13 and the fixed slit plate 14 may occur in the configuration of the apparatus, and thus a change in the spacing of the main pole on the Fraunhofer diffraction is caused. It happens. At this time, if the average spacing of the 0th primary pole and the primary primary pole coincides with the interval d ₂ of the slit 17, the change of the gap between the movable slit plate 13 and the fixed slit plate 14 is maximized. It becomes to be acceptable. The distance L between the movable slit plate 13 and the fixed slit plate 14 in which the interval between the zero primary pole and the primary primary pole coincides with the interval d of the slit 17 is expressed by the formula (8). In

m = 1… … … … … … … … … … … … … … … … … … … … … … … … … … … (9)

from

Becomes In addition, when the distance between the main pole and the primary pole in the Fraunhofer diffraction is Md ₁ (M is a positive integer), the width of the main pole is

In the range where the width W of the main pole determined by N and M does not exceed 1/2 of the interval of the slit 17, ie

In the condition of, the amplitude of the detection signal is sufficient to detect

Becomes

Moreover, the practical width W of the main pole also relates to the size S of the light source and the focal length F of the collimator lens.

Where N is large enough, and the width W of the main pole does not exceed half of the slit 17, i.e.

In the condition of, the amplitude of the detection signal is sufficient to detect.

5 shows the change of the maximum amplitude due to the change of S / F.

Next, the amplitude change of the detection signal due to the change of the distance L between the movable slit plate 13 and the fixed slit plate 14 occurs when the main maximum interval of each difference does not coincide with an integer multiple of the slit interval, The magnitude of the amplitude change of the detection signal depends on the magnitude of the primary maximum or higher.

6 shows the magnitude and spacing of the main pole of each difference according to the values of a / d ₁ from equations (1), (2) and (4), and shows the minimum amplitude of the detected signal when The result of the float as a ratio to the size of the main electrode is large. If the minimum amplitude is large, the difference with the maximum amplitude is small, and the amplitude change due to the change of L is small.

As described above, according to this embodiment, the laser diode and the collimator lens are used as the light source, and the Fraunhofer diffraction image generated by the slit regularly arranged on the movable slit plate is projected onto the fixed slit plate to detect the main pole, High contrast stripes can be detected, making it possible to easily downsizing and high resolution. In addition, by setting the slit width of the periodic slit on the moving slit plate to be 1/2 or more of the slit interval, the ratio of the size of the primary pole to the primary pole of the 0th primary pole can be reduced, and the movable slit By obtaining a stable detection signal against a change in the gap between the plate and the fixed slit plate, miniaturization and high resolution can be easily performed.

In addition, the ratio of the focal length of the collimator lens constituted with the laser light source and the size of the light emitting source of the laser diode is 1/2 of the distance between the moving slit plate and the fixed slit plate and the slit interval of the periodic slit on the moving slit plate. By making it smaller than the ratio, the blur of the Fraunhofer diffraction image can be made small, and high contrast sharpness can be obtained, making it easy to downsize and high resolution.

In addition, the projection of the movable slit plate and the fixed slit plate is performed without damaging the amplitude of the light and dark streaks in the Fraunhofer diffraction by projecting the gap between the zero and primary maximal poles closer to an integer multiple of the slit interval. The gap can be increased, and the slit plate life can be shortened by the dirt and damage of the slit plate due to the intrusion of dust and the like between the moving slit plate and the fixed slit plate. I can do it.

In addition, the gap between the movable slit plate and the fixed slit plate can be easily determined by handling only the gap between the primary and the primary pole bands of order 0, with practically sufficient precision. Could.

In addition, since the interval between the 0th primary pole and the primary primary pole is projected on the fixed slit plate so that the slit interval coincides with an integer multiple, the detection signal change due to the change of the gap between the movable slit plate and the fixed slit plate can be allowed to the maximum. In this configuration, the influence of the gap accuracy between the movable slit plate and the fixed slit plate due to the configuration of the mechanism can be made light, and the miniaturization and high resolution can be easily performed.

Also, by projecting the n-th order maximal band from the 0th order maximal band into the slit on the fixed slit plate, it is possible to convert the amplitude of the light and dark stripes on the Fraunhofer diffraction to the amplitude of the detected signal as much as possible. By obtaining an amplitude detection signal, miniaturization and high resolution can be easily performed.

In this embodiment, the movable slit plate is arranged on the light source side, but the fixed slit plate may be arranged on the light source side.

In addition, in this embodiment, although the fixed slit plate is disposed, the same effect can be obtained even when only the optical detection element having the slit function of the fixed slit plate is used.

In this embodiment, although a laser diode and a collimator lens are used as the light source, any laser light source capable of obtaining parallel light beams may be used.

Next, a second embodiment of the present invention will be described with reference to the drawings. In the position detection device configured as in FIG. 1, the Fraunhofer diffraction image of the slit 16 is projected onto the fixed slit plate 14 in the same manner as in the first embodiment. As shown in the seventh degree, he was a slit (17) of the formed on the fixed slit plate 14, an opening width b, d ₂ is arranged a number side by side with an interval d ₂ is set to 1, the integer minutes of d _1, Light is transmitted in the slit 17 and shielded in other parts, and the transmitted light irradiates the photodetector 15.

At this time, the interval between the main poles of the Fraunhofer diffraction projected on the fixed slit plate 14 is equal to an integral multiple of the interval d ₂ of the slits 17 arranged on the fixed slit, and the width W of the main poles is when in the range of not more than 1/2 of the distance d ₂ of the slit 17, the amplitude of the detection signal outputted from the optical detection chulsoja 15 according to the movement of the movable slit plate 13 becomes maximum.

Here, when the distance between the primary pole pole and the primary pole pole of the Fraunhofer diffraction phase 0 is M ₁ D ₁ (M ₁ is a positive integer), the width W of the pole pole is

When the distance d ₂ of the slit 17 on the fixed slit plate 14 is d ₁ / M ₂ (M ₂ is a positive integer),

In other words,

Within the conditions of, it is considered that the amplitude of the detection signal is sufficient, and when M ₁ = 1 as an example,

The amplitude of the detection signal is reduced even if the interval d ₂ of the slit 17 on the fixed slit plate 14 is reduced to 4 / N of the interval d ₁ of the slit 16 on the movable slit plate 13. Is sufficiently present, and the improvement such as N / 4 times decomposition can be achieved as compared with the case where d ₁ = d ₂ .

In addition, the space | interval L of the said moving slit board 13 and the said fixed slit board 14 at this time is represented by (8) Formula,

m = 1… … … … … … … … … … … … … … … … … … … … … … … … … … (21)

from,

Will be

Therefore, within the condition of equation (19),

Becomes

The resolution can be improved without narrowing the distance between the movable slit plate 13 and the fixed slit plate 14.

As described above, according to the present embodiment, a laser diode and a collimator lens are used as a light source, and the interval between the 0th and the 1st main poles of the Fraunhofer diffraction generated by the periodic slits on the moving slit plate is the periodic slits. The fixed slit plate is provided at a position that is an integer multiple of the interval of the slit plate, and the interval of the periodic slit on the fixed slit plate is one-integer of the interval of the periodic slit on the movable slit plate, and the Fraunhofer produced by the periodic slit on the movable slit plate By setting the width of the diffraction peak at least twice as large as the width of the diffraction phase, high resolution can be achieved without compromising the amplitude of the contrast stripes on the Fraunhofer diffraction image, and miniaturization can be achieved without reducing the distance between the moving slit plate and the fixed slit plate due to the high resolution. And high resolution can be performed easily.

In addition, in this embodiment, although the moving slit is arrange | positioned at the light source side, you may arrange | position a fixed slit plate at the light source side.

Incidentally, in this embodiment, although the fixed slit plate is provided, the same effect can be obtained even when only the photodetecting device having the slit function of the fixed slit plate is used.

In this embodiment, the light source laser diode and the collimator lens are used, but it goes without saying that any laser light source capable of obtaining parallel light beams may be used.

As described above, according to the first aspect of the present invention, a high quality parallel beam is obtained by a laser light source and a collimator lens, and a zero-order main band having a large Fraunhofer diffraction image of periodic slits due to coherence of the laser light is obtained. In contrast, the sharpness of the contrast stripes increases, the bright part becomes a sharp beam shape, and the two slit plates are arranged at a distance that allows the gap between the main poles to match the slit gap, thereby providing two slits due to the configuration of the mechanism. It is possible to minimize the influence of the spacing accuracy of the plate, to lengthen the life of the two slit plates, and to achieve the effect of easily miniaturization and high resolution.

Further, according to the second invention of the present invention, a large zero-order main pole in the Fraunhofer diffraction of the periodic slit is obtained, and the bright part becomes a sharp beam shape having a width tangent, and the interval between the main poles and the slit gap. Two slit plates are provided at a distance to match, and the slit interval of the periodic slit on the slit plate on the photodetector side is an integral number of the slit interval of the periodic slit on the slit plate on the light source side, and the width of the main pole is By setting it to more than twice, the high resolution can be achieved simply by reducing the slit interval of the periodic slits on the slit plate toward the photodetector without reducing the spacing of the two slit plates, making it easier to downsize and high resolution. It is possible to realize an excellent position detection device that can achieve the effect.

Claims (20)

A light source using a laser light source, two slit plates having periodic slits, and a photodetector for detecting a change in the amount of light due to the movement of the slit plate. The photoelectric position detector which detects the output signal of a photodetector and calculate | requires the displacement amount of the said slit board, WHEREIN: The light and dark stripes of the Fraunhofer diffraction which generate | occur | produce by the periodic slit on the said slit board of the light source side the said slit board of the photodetector side And a photodetector via the periodic slit. The slit width a of the periodic slit on the slit plate toward the light source side is a

the position detecting device, characterized in that d _1/2. A light source using a laser light source consisting of a light source of size S and a collimator lens of focal length F, one slit plate with periodic slits, and at least one photodetector for detecting a change in the amount of light due to the movement of the slit plate And a photoelectric position detector which installs the slit plate between the light source and the photodetector and detects the light streaks in the Fraunhofer diffraction generated by the periodic slits on the slit plate with the photodetector to obtain the displacement of the slit plate. In S, if the distance between the periodic slit of the slit interval d _{1 on} the slit plate and the Fraunhofer diffraction image to be detected is set to L, S / F

d / ₁ / 2L position detection device characterized in that. 4. A position detecting apparatus according to claim 3, wherein a laser diode is used as a light emitting source. The distance between the periodic slit on the slit plate and the Fraunhofer diffraction image to be detected, wherein the distance between the zero-order and the first-order main poles on the Fraunhofer diffraction is ± b / at an integer multiple of the slit interval of the periodic slit. A position detecting device, characterized in that within the range of 2. The distance between the periodic slits on the slit plate and the Fraunhofer diffraction image to be detected is determined by the distance between the zero-order main and the primary pole bands of the Fraunhofer diffraction image being an integer multiple of the slit interval of the periodic slits on the slit plate. A position detecting device, which is characterized in that it coincides. 4. The distance between the periodic slits on the slit plate and the Fraunhofer diffraction image to be detected is equal to the distance between the zero-order main and n-th order main poles on the Fraunhofer diffraction image. A position detecting device, characterized in that it is in the range of 1b to n times ± b / 2. The slit width a of the periodic slit on the slit plate is:

the position detecting device, characterized in that d _1/2. A light source using a laser light source consisting of a light source of size S and a collimator lens of focal length F, two slit plates with periodic slits, and a photodetector for detecting a change in the amount of light due to the movement of the slit plates. And the two slit plates provided between the photodetector and the light and dark stripes on the Fraunhofer diffraction generated by the periodic slits on the slit plate on the light source side via the periodic slits on the slit plate on the photodetector side. In the photoelectric position detector for detecting the displacement of the slit plate by detecting with a photodetector, the slit interval d ₁ of the periodic slit on the slit plate on the light source side and the slit interval d ₂ of the periodic slit on the slit plate on the photodetector side are d ₁ = d ₂ , and the width of the main electrode in the Fraunhofer diffraction is 1/2 of the slit interval d ₂ of the periodic slit on the slit plate on the photodetector side. When the distance between the periodic slit on the slit plate on the light source side and the periodic slit on the slit plate on the photodetector side is set to L, S / F

d / ₁ / 2L position detection device characterized in that. 10. A position detecting apparatus according to claim 9, wherein a laser diode is used as a light emitting source. 10. The distance between the periodic slits on the slit plate on the light source side and the periodic slits on the slit plate on the photodetector. A position detection device characterized in that it is within this range of ± b / 2 at an integral multiple of the slit interval of the periodic slit on the plate. 12. The distance between the periodic slits on the slit plate on the light source side and the periodic slits on the slit plate on the photodetector. A position detection device, characterized in that it coincides with an integer multiple of the slit interval of the judge's periodic slit. 10. The distance between the periodic slit on the slit plate on the light source side and the periodic slit on the slit plate on the photodetector side. A position detection device, characterized in that it is in the range of ± b / 2 of n times to the slit interval of the periodic slit on the slit plate. The width a of the slit of the periodic slit on the slit plate toward the light source side is a

the position detecting device, characterized in that d _1/2. A light source using a laser light source consisting of a light source of size S and a collimator lens of focal length F, two slit plates with periodic slits, and a photodetector for detecting a change in the amount of light due to the movement of the slit plates. And the two slit plates provided between the photodetector and the light and dark stripes on the Fraunhofer diffraction generated by the periodic slits on the slit plate on the light source side via the periodic slits on the slit plate on the photodetector side. In the photoelectric position detector for detecting the displacement of the slit plate by detecting with a photodetector, the slit interval d ₁ of the periodic slit on the slit plate on the light source side and the slit interval d ₂ of the periodic slit on the slit plate on the photodetector side d _1> d _2, and d ₂ is set to 1, and also the constant minute of d _1, the slit plate of the width of the main maximum of said Fraunhofer diffraction image side photodetector If the distance of the periodic slits of the slit gap d ₂ periodically slit and the light detector side of the slit plate of the periodic slits of the slit plate of the light source side, which is less than or equal to 1/2 L to S / F

d / ₁ / 2L position detection device characterized in that. A position detecting apparatus according to claim 15, wherein a laser diode is used as a light emitting source. 16. The distance between the periodic slits on the slit plate on the light source side and the periodic slits on the slit plate on the photodetector. A position detection device, characterized in that it is within this range of ± b / 2 at an integral multiple of the slit interval of the periodic slit on the plate. 18. The distance between the periodic slits on the slit plate on the light source side and the periodic slits on the slit plate on the photodetector. A position detection device, characterized in that it coincides with an integer multiple of the slit interval of the periodic slit on the plate. 16. The distance between the periodic slits on the slit plate on the light source side and the periodic slits on the slit plate on the photodetector side, wherein the interval between the 0th order pole and the 1st to nth order pole poles on the Fraunhofer diffraction is the light source side. A position detection device, characterized in that it is in the range of ± b / 2 of n times to the slit interval of the periodic slit on the slit plate. The slit width a of the periodic slit on the slit plate toward the light source side is a

the position detecting device, characterized in that d _1/2.

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