JPS5845687B2 - Movement distance and speed measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a light source for generating a luminous flux, a first diffraction grating for separating the luminous flux into at least two mutually separated partial luminous fluxes, and at least one further grating for recombining the diffracted partial luminous fluxes. a diffraction element, one last optical diffraction grating which redirects the separate partial beams in the same direction so that the partial beams can interfere with each other, and a beam in the direction that intersects the light source in the relative opposite direction of said grating or element. Device for measuring linear or angular distances and linear or angular velocities, comprising photoelectric means for weighing the different phase positions of at least one of the light beams modulated by interference during movement be.

Journal of Scientific Instruments (J, of 5cie, In5tr, ) 36
(May 1959), pages 227-230, an interferometer is known in which diffraction gratings are used which are arranged successively in three optical directions for the separation and recombination of parallel light beams.

A test object is placed in one of the separated beams.

The spacing of the gratings and the grating constants are selected such that the rays separated by the first grating are collected at one point in the last grating and interfered.

Applied Optics (App 1. Optic
e) Volume 6, No. 11 (November 1967) 1861-18
On page 65, an injection device (Auflichteinrichtung) for measuring linear displacement consisting of two gratings is described.
) are listed.

The first grating in the beam direction serves to separate the beams and to recombine the separated beams after reflection at the second grating.

Both lattice constants are such that one lattice constant is an integer multiple of the lattice constant of the other lattice, and the spacing is chosen such that the rays separated by the spacing coincide again at one point and interfere with each other. There is.

The same measuring device also uses optical technology (0pt
ical Technology) Volume 38, No. 10 (
(October 1971), pages 588-590.

Here, however, three successive diffraction processes take place on three reflection gratings.

The mutually interfering light beams are refracted into different orders of diffraction, resulting in the modulation of the light waves in waveforms 180° out of phase with each other, which can then be converted into electrical push-pull signals by a photoelectric receiver system. The electrical push-pull signal serves to suppress the unmodulated DC component of the photoelectric signal by differential formation.

However, when light waves are synthesized, in order for the vector indicating the synthesized amplitude to rotate like a rotating magnetic field in electricity, a signal with a phase shift of at least 900 or an odd multiple of 90' is required, but this signal is missing. There is.

The relative movement direction of the diffraction grating can be detected from the rotation direction of the vector indicating the composite amplitude resulting from the synthesis of light waves.

Therefore, the present invention provides a method for measurements of the aforementioned type, which can generate all the necessary out-of-phase signals and which allows simple signal quantification in order to form a rotating vector field in which a vector of composite amplitudes corresponding to a rotating magnetic field rotates. The challenge is to create a device.

This problem has been solved according to the invention by the features of the characteristic part of claim 1.

According to an advanced form of the invention, separation can also be achieved when the faces of at least two gratings are at an angle to each other.

A particular advantage of the device of the invention lies in the success in simultaneously obtaining all the signals necessary to define the rotating vector field from a single grating area.

The details of the present invention will be explained with reference to embodiments shown in the figures.

As shown in the first section and FIG.
+1, i-th diffraction light 1-. is redirected by the second grating 12 and concentrated so as to interfere again with the third grating, in which case said third grating 13 is directed from the point of concentration to the optical axis if the lattice constants of all gratings are the same. is shifted by a distance of Δl along.

The optical paths interfering behind the third grating 13 have a spacing S,
At the focal plane 14 of the optical system 15, interference fringes with the same tendency occur.

When placing the photoelectric receiving system (Fig. 1a) on the focal plane 14,
Phase-shifted signals can be obtained from the individual light receiving surfaces a and b of the light receiving system.

Interference fringes i appear separately at c and d, thus producing rotating vector field signals.

The separation of the beam guides creates local intensity modulation of the source image at the back focal plane.

FIG. 3 shows a configuration similar in principle; in this embodiment, the gratings 11, 12, and 13 have the same mutual spacing, whereas the grating constants d1□ and d13 or d12 are different from each other. , such that the desired beam separation into the spacing S is achieved at the third grating.

In addition to the phase-shifted signals, it is also possible to measure the ray flow due to other diffraction orders at various distances from the optical axis at the focal plane 14, which is the light-receiving surface. As shown in the figure.

FIG. 4 shows an embodiment using reflected light.

In this case, each different spacing between the gratings is achieved by tilting the plane of the grating 12 to the plane of the grating 11 by an angle ε.

It should be noted that the desired separation of the light beams by the amount S can also be obtained by methods different from those described here.

For example, there is a method in which an optical wedge is placed between parallel gratings, and the light rays refracted by one grating into different orders of diffraction are passed through the optical wedge, reflected by another grating, and then passed through the optical wedge again to become parallel lines with a spacing of S. There is a method of using two radiation type gratings having slits formed at equal intervals, and causing light transmitted through one grating to be reflected by the other grating.

Examples of the present invention are as follows.

(1) Lattice 11.12°1 with mutually different lattice constants
3. Device according to claim 1, characterized in that: 3 is provided.

(2) A device according to the claims or the preceding paragraph, characterized in that the spacing between the gratings 11, 12, 13 is different from each other.

(3) A device according to claim 1, wherein the faces of at least two gratings 11,12 form an angle.

[Brief Description of the Drawings] Figures 1 and 2 are diagrams of transmitted light type devices with different grating spacings, Figure 1a is a diagram showing an embodiment of a photoelectric receiver, and Figure 3 is a diagram showing gratings with different lattice constants. Diagram of a transmitted light type device having,
FIG. 4 is a diagram of a reflected beam device with mutually tilted gratings. 11...First diffraction grating, 12...Diffraction element, 13...Last diffraction grating.

Claims (1)

[Claims] 1. A light source for generating a luminous flux, a first diffraction grating that divides the luminous flux into at least two mutually separating partial luminous fluxes, at least one other diffraction element that recollects the diffracted partial luminous fluxes, and separate parts. one last diffraction grating which deflects the light beams in the same direction, thus allowing the partial light beams to interfere with each other, and upon movement of said grating or element in a direction that intersects the light beams in relatively opposite directions; and a photoelectric means for measuring the changing phase position of at least one of the light beams modulated by interference, and one of the diffraction grating and the tilted diffraction element is fixed to the part to be measured, and a linear or In a device for measuring angular motion distance and linear velocity or angular velocity, at least one of the spacing and the grating constant of the diffraction gratings or diffraction elements that are parallel to each other and movable relative to each other is such that the light ray (l+1. 1□) is selected such that it appears in at least two side-by-side points in the last grating 11:13.