JPH04268412A - Position-change measuring apparatus and method of use thereof - Google Patents

Abstract

PURPOSE: To obtain a one-dimensional and multi-dimensional high resolution measuring instrument for accurately measuring positional change with its optical constituent and electronic constituent not affected by the influence of assembling positional regulation. CONSTITUTION: A mesh structure 14 is disposed perpendicularly to the optical axis 20 of a focusing objective lens 18 at an interval of the focal distance (f) of the lens 18. The mirror surface of a plane mirror 19 is directed perpendicularly to the axis 20 of the lens 18. A carrying plate 13 is set capable of displacing at the position relative to the axis 20 of the lens 18 and perpendicularly to the structure. Or, the plate 13 is fixed at its position, and the mirror 19 is set tiltably to the axis 20 of the lens 12 around the axis parallel to the direction of the structure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric measurement device for measuring small relative position changes and a method of using the same.

0002

2. Description of the Related Art A positional change is defined as a unidirectional displacement according to one coordinate or multiple coordinates.
erschiebungen) and a tilting movement about one or two axes. A photoelectric measuring device that measures displacement in increments is a step detector (S
Chrittgeber). Measuring devices that measure tilt angles are known as self-sighting telescopes.

The basic construction of an incremental step detector for measuring position is described, for example, in G. Schroeder's textbook, Technical Optics, Vol. 6 (1987), pages 171 and 172. A light source illuminates the grating scale via a condenser. The grating scale is coupled to a scanning pin and the displacement of the scanning pin is measured. A stationary scanning plate is arranged behind the grating scale in the irradiation direction. This scanning plate has a reference grating pitch. A displacement of the grating scale modulates the light flux behind the reference grating. This modulation is detected with a photoelectric receiver.

[0004] In order to detect the direction and obtain the push-pull signal, the reference grating is divided into four gratings with division periods that are out of phase with each other. Each reference grid is associated with a photoelectric receiver. The grating scale and the scanning plate must be oriented parallel to each other with as close a spacing as possible. The grid division directions must be oriented separately from each other. This allows for the structure, assembly, and
The requirement for position adjustment is satisfied.

Furthermore, it is known from German Patent No. 1 217 637 to image subareas of a scale grating onto other subareas of the same scale grating. In this case, the image of the first partial area moves in the opposite direction towards the scale grating. With this device, some alignment work can be avoided, but it is not possible to generate out-of-phase signals in the scanning area. By using a cross grating instead of a line grating, a step detector of this type can also be configured for two-dimensional position measurements.

A self-collimating telescope with a geometrically divided optical path for imaging a measurement mark onto a reference mark in the telescope's eyepiece has also been described in G. Ibid. Schroed
It is described on page 140 of the er textbook. The illuminated measurement mark is located in the focal plane of the telescope objective and is imaged to infinity by this objective. After the image of the measurement mark is reflected by a plane mirror, instead of visually observing the displacement of the image of the measurement mark with respect to the reference mark that occurs in the plane of the reference mark, e.g.
It is known from the publication No. 247 that the reference mark is constructed as a light-receiving line sensor and the position of the image of the measurement mark is determined photoelectrically. Measurement accuracy is determined by the quantity and size of these sensor elements.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide one-dimensional and multi-dimensional high-resolution measuring devices for measuring positional changes with high precision, the optical and electronic components of which are assembled and It is an object of the present invention to provide a measuring device that is not affected by position adjustment.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a photoelectric measuring device for measuring small relative position changes, which includes an illumination device for illumination and at least one one-dimensional mesh structure. a transparent carrier plate for locating a scanning grating attached to the mesh structure so as to be located in the same plane as the mesh structure, the carrier plate comprising: a photoelectric receiver attached to the scanning grating; The mesh structure has a carrier plate connected to the carrier plate, an imaging objective disposed behind the carrier plate, and a plane mirror disposed behind the imaging objective;
arranged perpendicularly to the optical axis of the imaging objective at intervals of the focal length of the imaging objective, the mirror surface of the plane mirror is oriented perpendicularly to the optical axis of the imaging objective, and the carrier plate The carrier plate can be displaced in position relative to the optical axis of the imaging objective and perpendicular to the direction of the mesh structure, or the carrier plate can be fixed in position and the plane mirror can be moved in the direction of the mesh structure. It is characterized in that it can be tilted around parallel axes with respect to the optical axis of the imaging objective.

The present invention is also characterized in that the photoelectric measuring device described above is used as a position detector in a scanning head of a coordinate measuring device and as an automatic collimating telescope for measuring tilt angles. It is something.

What is important in the invention is that the mesh structure corresponding to the scale grating and the reference structure forming the scanning grating are arranged side by side on the same carrier plate. A photoelectric receiver associated with each scanning grating area is also mounted on this carrier plate. The scale grating and scanning grating structures can be provided simultaneously on the carrier by known vapor deposition techniques or high-precision photolithographic techniques. The mutual orientation of the scale grating and the scanning grating is therefore immovably fixed.

In order to use the measuring device according to the invention as a position detector for a length measuring system, the plane mirror must be held immobile in its position. A relative displacement between the image of the scale grating and the scanning grating can be produced both by moving the carrier plate in its plane and also by moving the imaging objective in its principal plane. Both elements can therefore be selectively coupled to the object in order to measure the displacement of the object.

In order to use the measuring device according to the invention as a self-sighting telescope for measuring tilt angles, the carrier plate and the imaging objective must be held immovably relative to each other. The tilting of the plane mirror creates the relative displacement between the image of the scale grating and the scanning grating that is necessary for the measurement. In this case of use, the plane mirror is therefore coupled to the object whose tilt with respect to the optical axis of the imaging objective is to be measured. As a result, the plane mirror in the length measurement system only affects the measurement area and does not affect the measurement accuracy.

The measuring range of the measuring device according to the invention is limited by the aperture of the imaging objective and the mutual position of the scale grating and the scanning grating on the carrier plate. The measuring range is of the order of centimeters and is sufficient for use as a position detector for the scanning head of a coordinate measuring device.

[0014]

Embodiments Next, embodiments of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the lighting device 10 has a lamp 11 and a capacitor 12. A plane-parallel glass plate is provided as the carrier plate 13. Carrier 13
A one-dimensional network structure 14 is deposited thereon. The direction of the mesh structure 14 is perpendicular to the plane of the drawing and covers approximately two-thirds of the area of the carrier plate 13. Mesh structure 14
A scanning grating 15 is provided so as to border the . The direction of the scanning grating 15 is also perpendicular to the plane of the drawing. The scanning grating 15 is covered by a photoelectric receiver 16 . Photoelectric receiver 16 is connected to counter 17 .

The imaging objective 18 is arranged behind the plane of the mesh structures 14, 15 in the illumination direction at a distance of its focal length f. A plane mirror 19 is provided behind the imaging objective lens 18 . The plane mirror 19 is approximately perpendicular to the optical axis 20 of the imaging objective 18.

An illumination device 10, an imaging objective lens 18,
The plane mirror 19 is provided on a common frame 21. The carrier plate 13 is connected to the pin 22. The pin 22 is supported by a guide 23 so as to be movable perpendicular to the optical axis 20, that is, on the plane of the drawing. The pin 22 may be configured as a scanner or may be connected to an object whose displacement is to be measured.

In FIG. 1, the optical axis 2 of the network structure 14
When a subarea located on 0 is observed, this subarea is imaged via the imaging objective 18 and, after reflection by a plane mirror 19, is imaged again onto the plane of the mesh structure 14. Moreover,
The image is formed point-symmetrically with respect to the intersection of the plane of the network structure 14 and the optical axis 20. When the mesh structure 14 is moved, its image moves twice as fast in the opposite direction.

In this case, the image of the network structure 14 is moved through the scanning grating 15, thereby producing a modulated light beam. The modulated light flux is converted into an electrical signal in a photoelectric receiver 16, and this electrical signal is processed in a counter 17 to provide a display proportional to the displacement. If the scanning grating 15 has four out-of-phase scanning areas, as is known, push-pull signal processing of displacements and direction detection are possible.

The mesh structure 14 may be configured as a cross grid 24, as shown in FIG. 2, for measurements in two coordinate directions x and y. Each coordinate direction is associated with its own scanning grid 25, 26. FIG. 2 shows these scanning gratings 25, 2 with four out-of-phase grating regions.
An enlarged view of 6 is also shown. The surface 27 of the carrier plate 13' which is not covered by the cross grating 24 or by the scanning gratings 25, 26 may be provided with a mirror coating. If surface 27 is provided with a mirror coating, it is advantageous if mesh structure 24 is also reflective on the side facing away from illumination device 10 .

The size of the carrier plates 13, 13', the area covered by the mesh structures 14, 24, the scanning gratings 15, 25
. A displacement region is created in which a partial region of the mesh structure 14, 24 is located, which partial region is selected to be imaged onto the associated scanning grating.

FIG. 3 shows the configuration of a measuring device for measuring the displacement of the scanner 28 based on the three coordinate directions of movement x, y, z. In this case, the plane parallel to the plane of the drawing is defined as the x-z plane, and the direction perpendicular to the plane of the drawing is defined as the y direction. This configuration includes the components already explained using FIGS. 1 and 2, and the same components are given the same reference numerals.

An illumination device 10 and an imaging objective lens 18 are fixed to the frame 21. Furthermore, frame 21
A turning mirror 29 and a second illumination device 30 are provided. The turning mirror 29 turns the optical axis 20 of the imaging objective 18 by 90°.

The illumination device 10 is provided with a carrier plate 13' with the cross grating 24 and the scanning gratings 25, 26 shown in FIG. A carrier plate 13 with a scanning grid 15 and a scanning grid 15 is provided. The carrier plate 13 is connected with a pin 22. The pin 22 is supported by the frame 2 via a parallelogram elastic guide 31 so as to be displaceable in the z direction. A scanner 28 is connected to the pin 22.

The carrier plate 13' is positioned and fixed on the base carrier 32. The frame 21 is suspended on the base carrier 32 via parallelogram elastic guides 33, 34 which are displaceable in the x and y directions. In this embodiment, as a variant of the embodiment of FIG. 1, the imaging objective 18 and its optical axis 20 in the x-y plane are displaced on the carrier plate 13' relative to the mesh structure. It is possible. All mesh structures and the surfaces covered by the scanning gratings and lying in the same plane as the carrier plates 13, 13' are reflective on the side facing away from the associated illumination devices 30, 10. . These surfaces are arranged relative to the imaging objective 18 at a spacing of the focal length of the imaging objective 18 and each additionally has the function of a plane mirror 19 in the other measuring system. The mesh structure of the carrier plate 13' is reflected by the reflective side surface of the carrier plate 13;
Reflects on the reflective side of '. Support plate 1 in the z direction
A displacement of 3 does not significantly affect the imaging of the cross grating 24. Likewise, the imaging of the mesh structure 14 is not disturbed by the relative displacement of the carrier plate 13'. In order to make the imaging characteristics of the imaging objective 18 the same on both sides, the imaging objective 18
It is advantageous for the system to consist of two system parts that are optically identical and arranged symmetrically to each other.

Scanners that measure in three dimensions require two measuring systems for x/y and z measurements, separated from each other. Such scanners are usually configured as completely separate systems. The embodiments described above combine two measuring systems, allowing only one
integrated into a single measurement system with two imaging objectives. However, the adjustment of the distance between the imaging objective and the carrier plate can be carried out independently of each other and can be carried out with mechanically efficient parallelogram elastic guides.

FIG. 4 shows a modification of the embodiment shown in FIG. 1, and is for measuring the tilt angle. The illumination device 10, the carrier plate 13 and the imaging objective 18 are arranged in a fixed position relative to each other in a frame 21, which in this embodiment is designed as a housing. The plane mirror 19 is arranged apart from these and is fixed to an object (not shown) at an arbitrary interval along the optical axis 20. Here, it is assumed that the tilt angle ψ of the object with respect to the optical axis 20 is to be measured. The components fixed to the frame 21 form a photoelectrically measuring self-sighting telescope.

As already mentioned, when the plane mirror 19 is tilted, the image of the network structure 14 is displaced through the scanning grating 15. The distance s is directly proportional to the tilting angle ψ and the focal length f of the imaging objective 18 if the tilting angle ψ is small. That is, s=f×2ψ. When f=60 mm and the lattice constant of the mesh structures 14 and 15 is 8 μm, the tilting angle ψ=1
3.75'' corresponds to the signal period.

If a cross grating 24 with scanning gratings 25, 26 as shown in FIG. 2 is used as the mesh structure, it is possible to photoelectrically measure the tilt angle in two mutually orthogonal directions. The measurement range is only limited by the aperture of the imaging objective 18 and the extent of the network structure. It is easily possible to set the measurement range to several degrees in each direction.

[0030]

Effects of the Invention The present invention provides one-dimensional and multi-dimensional high-resolution measurement devices for measuring position changes with high precision, in which optical and electronic components are assembled and are not affected by position adjustment. This provides a measurement device that would otherwise not be available.

[Brief explanation of the drawing]

1 shows a measuring device according to the invention for measuring linear position changes; FIG.

FIG. 2 shows a carrier plate with a scale grating and a scanning grating for two-dimensional measurements;

FIG. 3 is a diagram of a measuring device for measuring position changes in three coordinate axes;

FIG. 4 is a diagram of a measuring device for measuring changes in the tilting angle;

[Explanation of symbols]

10 illumination device 13 carrier plate 14 mesh structure 15 scanning grating 16 photoelectric receiver 18 imaging objective 19
plane mirror

Claims (9)

[Claims] 1. A photoelectric measurement device for measuring small relative position changes, comprising: an illumination device (10) for illumination;
and at least one one-dimensional mesh structure (14);
a transparent carrier plate (13) for arranging this mesh structure (14) and a scanning grating (15) attached to the mesh structure so as to be located in the same plane;
), a carrier plate (13) connected to a photoelectric receiver (16) attached to the carrier plate (13), an imaging objective (18) arranged behind the carrier plate (13), and an imaging objective (18) a plane mirror (19) arranged behind the lens, the mesh structure (14) having a focal length (f) of the imaging objective (18).
are arranged perpendicularly to the optical axis (20) of the imaging objective (18) at intervals of is,
A carrier plate (13) carries an imaging objective (18) in its plane.
) can be displaced in position relative to the optical axis (20) of the carrier plate ( ) and perpendicular to the network direction;
13) is fixed in position, and a plane mirror (19) moves the imaging objective (1) around an axis parallel to the direction of the network structure.
8) A photoelectric measuring device characterized in that it can be tilted with respect to the optical axis (20). 2. A cross grid (2) on the support plate (13').
4) is attached, and the supporting plate (13') or plane mirror (19') is attached.
2. Photoelectric measuring device according to claim 1, characterized in that the photoelectric measuring device ) is movable or tiltable in two directions. 3. The scanning grating (15, 25, 26) has 4
2. Photoelectric measuring device according to claim 1, characterized in that it has two grating areas and a photoelectric receiver associated with these grating areas for generating rotation range signals. 4. The mesh structure (14, 24) is configured to be reflective on the side opposite the illumination device (10, 30) and forms a plane mirror in its entirety;
Each carrier plate (13, 13') is arranged by its reflective surface in front or behind the imaging objective (18) at a distance of its focal length;
18) and the carrier plate (13, 13') is deflected by 90° on one side of the imaging objective (18) via a deflection mirror (29); both carrier plates (13, 13') ')
The optical axis (20) of the imaging objective lens (18) lies within that plane.
4. The photoelectric measuring device according to claim 1, wherein the photoelectric measuring device is displaceable relative to and independent of one another. 5. Photoelectric measuring device according to claim 4, characterized in that the imaging objective (18) consists of two system parts that are optically identical and arranged symmetrically with respect to one another. 6. The imaging objective (18), the deflection mirror (29) and the illumination device (10, 30) are provided in a common frame (21), the frame (21) comprising a parallelogram elastic guide. The basic carrier (32
), and one carrier plate (13') is connected to the base carrier (
6. Photovoltaic device according to claim 4 or 5, characterized in that the further carrier plate (13) is fixed to the frame (21) via a parallelogram elastic guide (31). measuring device. 7. Parallelogram elastic guides (33, 34) fixed to the base carrier (32) are arranged in two sections orthogonal to each other.
characterized in that an orthogonal cross grid (24) is arranged on a carrier plate (13') which is displaceable in two coordinate directions (x, y) and which is also fixed to the base carrier (32). , The photoelectric measuring device according to claim 6. 8. Use of a photoelectric measuring device according to claim 1, characterized in that it is used as a position detector in a scanning head of a coordinate measuring device. 9. A method of using the photoelectric measuring device according to claim 1, wherein the photoelectric measuring device is used as an automatic collimating telescope for measuring tilt angles.