CN108180844A - A kind of multiple degrees of freedom precise displacement monitoring system based on double-frequency laser interference principle - Google Patents

Abstract

The invention discloses a multi-degree-of-freedom accurate displacement monitoring system based on the principle of dual-frequency laser interference. It includes a dual-frequency laser, a beam adjuster, a multi-channel dual-frequency laser interferometer and a reflector mirror; the multi-channel dual-frequency laser interferometer is composed of several dual-frequency laser interferometers parallel to each other; the laser generated by the dual-frequency laser Through the beam adjuster, after passing through the multi-channel dual-frequency laser interferometer, the multi-channel interference signals at different spatial positions obtained by the reflector are respectively transmitted to the data acquisition card through the optical fiber, and then the multi-channel interference signals are analyzed by the computer to obtain Motion errors in multiple degrees of freedom in each axis of motion. The beneficial effect of the present invention is that the present invention utilizes dual-frequency laser interference technology to monitor errors in more degrees of freedom while improving monitoring accuracy, providing a good solution for precise monitoring and positioning of motion axes.

Description

A multi-degree-of-freedom accurate displacement monitoring system based on the principle of dual-frequency laser interference

technical field

The invention belongs to the technical field of precision measurement, and in particular relates to a multi-degree-of-freedom precise displacement monitoring system based on the principle of dual-frequency laser interference.

Background technique

Each axis of the traditional three-coordinate measuring machine moves independently, and each axis uses a single-axis laser measurement method to measure the linear positioning accuracy and repeat positioning accuracy. There is no suitable means to obtain the pitch, yaw, and rotation of the motion axis at the same time; The pitch, yaw and rotation of the system will cause Abbe error on the axis of motion orthogonal to it. The Abbe error will amplify and change with different travel ranges. Uncertain Abbe error will bring great unmeasurable and unpredictability to the system accuracy. Therefore, it is impossible to fundamentally improve the spatial positioning and detection accuracy.

For example, ISARA400, an ultra-precision measurement system developed by IBS Precision Engineering in the Netherlands, is an ultra-precision probe-type 3D coordinate measuring instrument with a unique structure, which can realize nanometer-level precise measurement of complex workpieces such as large-aperture free-form surfaces and integrated optical systems. . The structure diagram of ISARA400 is shown in Figure 1. The middle part is glass-ceramic, and the glass-ceramic acts as a moving stage, which moves horizontally in X and Y directions, and moves up and down in Z direction. During the movement of the glass-ceramic stage in the X, Y, and Z three-dimensional spaces, the actual motion features have multiple degrees of freedom, namely, linear displacement accuracy, repeat positioning accuracy, rotation, pitch, and yaw, as shown in Figure 2. If only a single-axis flat mirror interferometer is used for measurement in each direction, only the linear displacement accuracy and repeatability accuracy of X, Y, and Z can be obtained. Pitch, yaw, and rotation need to be guaranteed by mechanical structure design, but no matter how the engineering is realized There is no guarantee that there will be absolutely no pitch, yaw, and rotation problems, and once such problems occur, the single-axis laser interferometry system cannot be measured, thus introducing unmeasurable and uncontrollable error sources into the system, greatly increasing the overall performance. The difficulty of machine design makes the equipment very expensive. The same problem exists with high-end CMMs from other companies, such as Carl Zeiss CMMs.

Contents of the invention

In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a multi-degree-of-freedom accurate displacement monitoring system based on the principle of dual-frequency laser interference that accurately monitors the movement of each axis. The system uses two or even six coaxial dual-frequency laser interferometers, so as to realize the error monitoring of multiple degrees of freedom (2~6 degrees of freedom) during the movement of the motion axis, and improve the measurement accuracy of the equipment.

In the present invention, the measurement and control system of each motion axis is set as a multi-channel (2-6 channels) parallel dual-frequency laser interferometer. The interferometer has superior light return function and is suitable for long-distance measurement. It can measure the displacement positioning accuracy, straightness, pitch, yaw and rotation of the one-dimensional motion axis at one time, and the measured pitch angle or torsion angle can be combined with the orthogonal axis. The linear position of the system can be calculated to obtain the Abbe error, so that the actual real position information of the measurement space point can be obtained through the software algorithm, and the purpose of improving the measurement accuracy of the system is achieved. Taking the X-axis as an example, through a specific reflector design, six displacement signals can be obtained in one measurement, and then the straightness of the X-axis along the Y and Z directions, the positioning error and the torsion Rx along the X-axis can be obtained through conversion. And around the pitch (Ry) and yaw (Rz) in the Y and Z directions, so as to realize the monitoring of the full degree of freedom (six degrees of freedom) in the X direction.

The technical solution of the present invention is specifically introduced as follows.

A multi-degree-of-freedom accurate displacement monitoring system based on the principle of dual-frequency laser interference, which includes a dual-frequency laser, a beam adjuster, a multi-channel dual-frequency laser interferometer, and a reflective corner mirror; the multi-channel dual-frequency laser interferometer consists of mutual Composed of several parallel dual-frequency laser interferometers; the laser generated by the dual-frequency laser passes through the beam adjuster and the multi-channel dual-frequency laser interferometer in turn, and then passes through the reflector mirror to obtain multi-channel interference signals at different spatial positions; the multi-channel interference signals They are respectively transmitted to the data acquisition card through the optical fiber, and then the multi-channel interference signal is analyzed by the computer to obtain the motion error of the multi-degree-of-freedom in each motion axis; the motion error generated by each motion axis during work can be regarded as multiple The coupling error of the degree of freedom error and the accurate measurement of the error of each degree of freedom are the key to accurate displacement monitoring.

In the present invention, the multi-channel dual-frequency laser interferometer is composed of 2 to 6 dual-frequency laser interferometers parallel to each other.

In the present invention, there are one or several reflective corner mirrors.

Compared with the displacement monitoring system of the traditional three-coordinate machine, the present invention has the following advantages:

1. The design of the equipment structure is simplified, no precise X/Y/Z motion and control mechanism is required, and multiple motion errors of the motion axis can be measured at the same time; 2. Through the six-channel dual-frequency laser interferometer, the motion error of the motion axis with full degrees of freedom can be realized monitoring;

2. The present invention can realize measurement accuracy monitoring and measurement error compensation of a measurement system based on a movement axis (such as a coordinate measuring machine) by accurately monitoring the error of each movement axis;

3. Cost optimization, no need to use large-volume glass-ceramics, silicon carbide materials, and Invar frames, and the vibration isolation performance can be appropriately reduced;

4. The technical solution can be extended and generalized, that is, in addition to this application, it can also realize the overcoming and industrialization of the real-time error compensation problem of the three-coordinate measuring machine;

To sum up, the present invention utilizes dual-frequency laser interferometry technology to monitor errors in more degrees of freedom while improving monitoring accuracy, providing a good solution for precise monitoring and positioning of motion axes.

Description of drawings

Figure 1 is a schematic diagram of the structure of the ISARA400 three-coordinate machine.

Figure 2 is a schematic diagram of six degrees of freedom error.

Fig. 3 is a schematic diagram of the three-way detection system in the embodiment.

Fig. 4 is a schematic diagram of the optical paths of the six-channel detection system in the embodiment.

Fig. 5 is an improvement scheme of the existing three-coordinate machine by using a six-way interferometer instead of a single-way interferometer in the embodiment.

Detailed ways

The technical solutions of the present invention will be described in detail below in conjunction with the drawings and embodiments.

The multi-degree-of-freedom precise satellite displacement system based on the dual-frequency laser interference principle of the present invention can realize the monitoring of the multi-degree-of-freedom (2-6 degrees of freedom) of the motion axis. In the examples, specific implementations of typical 3-DOF and 6-DOF monitoring are given.

Three-degree-of-freedom motion monitoring system, as shown in Figure 3, the dual-frequency laser 1 generates laser light that passes through the beam adjuster 2, passes through the three-way dual-frequency laser interferometer 3, and the displacement of the corresponding point on the reflector 4 changes, which can realize the movement axis. Three degrees of freedom error. Specifically, a three-way dual-frequency laser interferometer is used. The dual-frequency laser from the dual-frequency laser passes through the spectroscopic system to form three parallel laser beams; through three parallel dual-frequency laser interferometers, measuring the reflective corner mirror placed on the same plane can measure a plane of the motion axis The motion error of three points; by calculating the motion of three points, the motion error of three degrees of freedom can be separated, including two rotation angle errors and one positioning error.

Fig. 4 is a schematic diagram of the monitoring optical system of the six-channel dual-frequency laser interferometer. The optical path system includes a dual-frequency laser 1, a beam adjuster 2, a six-way special dual-frequency laser interferometer 3, and a reflector 4.

After the laser light emitted by the dual-frequency laser 1 passes through the beam adjuster 2, it is divided into six beams by the beam splitter of the laser inside the six-way dual-frequency laser interferometer. The high-frequency laser interferometer is kept parallel, and passes through the reflector 4 (the reflector is composed of several sub-reflectors distributed in different positions in space, and the special reflector in space can be obtained by measuring the interference signals at different spatial positions. The position changes to separate the error of more degrees of freedom; while the ordinary reflector can only reflect a single position optical signal, and can only obtain the error of one degree of freedom) can obtain six-way interference signals of different spatial positions, and the signals are respectively transmitted to In the data acquisition card, through the further analysis of the six-way signals by the computer, the motion errors of the six degrees of freedom corresponding to each motion axis can be obtained, which are three-way linear motion errors and three-way rotation axis rotation errors.

Fig. 5 is an application example, that is, an improvement scheme for an existing three-coordinate machine by using a six-way interferometer instead of a single-way interferometer. By adding a multi-channel interferometer and a special reflective corner mirror, the spatial attitude change of the corner mirror fixed on the DUT can be measured during the movement, and then the multi-degree-of-freedom motion error can be separated, including three positioning errors and three rotation error. Measurement accuracy is directly determined by the interferometer used in the measurement. For example, the six-way interferometer invented by the X-direction installation can measure the X-axis linear positioning, straightness (two), rotation, pitch and yaw, etc. 6 degrees of freedom errors

Compared with the displacement monitoring system of the traditional three-coordinate machine, the present invention has the following advantages:

1. The equipment structure design is simplified, without precise X/Y/Z motion and control mechanism;

2. Cost optimization, no need to use large-volume glass-ceramics, silicon carbide materials, and Invar frames, and the vibration isolation performance can be appropriately reduced;

3. The technical solution can be extended and generalized, that is, in addition to this application, it can also realize the overcoming and industrialization of the real-time error compensation problem of the three-coordinate measuring machine;

4. It can be extended to error monitoring of other measuring institutions and compensation of measurement errors.

To sum up, the present invention utilizes dual-frequency laser interferometry technology to monitor errors in more degrees of freedom while improving monitoring accuracy, providing a good solution for precise monitoring and positioning of motion axes.

Claims (3)

1. a kind of multiple degrees of freedom precise displacement monitoring system based on double-frequency laser interference principle, which is characterized in that it includes double Frequently

Laser, beam adjuster, multichannel two-frequency laser interferometer and reflection angle mirror；The multichannel two-frequency laser interferometer is by phase Mutually several parallel two-frequency laser interferometers composition；The laser that two-frequency laser generates passes through beam adjuster and multichannel successively Two-frequency laser interferometer, then obtain the multipath interference signal of different spatial through reflecting angle mirror；Multipath interference signal leads to respectively It crosses optical fiber and is transferred to data collecting card, then multipath interference signal is analyzed by computer, obtain in each kinematic axis Multivariant kinematic error.

2. multiple degrees of freedom precise displacement according to claim 1 monitors system, which is characterized in that the multichannel double-frequency laser

Interferometer is made of 2 ~ 6 two-frequency laser interferometers being mutually parallel.

3. multiple degrees of freedom precise displacement detecting system according to claim 1, which is characterized in that the reflection angle mirror has 1

It is a or several.