Optics: measuring and testing – Position or displacement
Reexamination Certificate
2001-03-26
2003-05-06
Lee, Michael G. (Department: 2876)
Optics: measuring and testing
Position or displacement
C356S400000, C356S150000, C356S153000, C356S510000, C356S508000
Reexamination Certificate
active
06559955
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a straightness measuring apparatus for a rectilinearly moving body. A rectilinearly moving body such as a pulse stage, a rectilinear motion stage and a rectilinear motion stage is used for feeding a machine tool and for various shape measuring apparatus and the like. Precision of works and measurements is largely dependent upon the degree of linearity of the rectilinearly moving body. A method and apparatus for measuring linearity at a high precision is therefore essential for precision inspection and calibration.
2. Description of the Related Art
A rectilinear motion stage is presently used in various fields such as mechanical industries. A measuring apparatus for inspecting or calibrating a rectilinear motion precision at all times is essential. A method of measuring a motion error of a rectilinear stage is already stipulated in JIS, and a measuring apparatus is also already sold. Generally, errors of rectilinear motion and rotation angle are a translation position error and a rotation angle error. The former parallel two-surface mirrors being mounted on the rectilinearly moving body;
a light source for generating a laser beam;
semi-transparent mirrors for splitting the laser beam into two laser beams;
optical path changing reflection mirrors for changing a direction of each laser beam; and
position sensors for detecting positions of the laser beam reflected from said horizontal, parallel two-surface mirror and said vertical, parallel two-surface mirror,
wherein a direction of said horizontal, parallel two-surface mirror is set so that directions of each normal to a bottom surface of each reflection surface take respectively:
[Expression 3]
m
H1
=(−1/(2), 0, 1/(2)),
m
H2
=(1/(2), 0, 1/(2)) or
m
H1
=(1/(2), 0, −1/(2))
m′
H2
(−1/(2), 0, 1/(2))
a direction of said vertical parallel two-surface mirror is set so that directions of each normal to a bottom surface of each reflection surface take respectively:
[Expression 4]
m
V1
=(0, 1/(2), −1/(2)),
m
V2
=(0, −1/(2), 1/(2)) or
m′
V1
=(0, 1/(2), 1/(2)),
m′
V2
=(0, −1/(2), −1/(2))
and said light source, said semi-transparent mirrors, said optical path changing reflection mirrors, said corner cube reflection mirrors and said position sensors has three types of error components, including one type of error components of position determination in a rectilinear direction and two types of error components in the plane vertical to the rectilinear direction (horizontal and vertical directions). The latter has three types of error components including pitching, yawing and rolling.
PROBLEM TO BE SOLVED BY THE INVENTION
With a general method of measuring a rotation angle error of a rectilinear moving body, two error components of pitching and yawing are measured at the same time with an auto-collimator, and rolling is measured with an electronic level. Apparatus using this method is also sold. However, since the principle of an auto-collimator is utilized, although two types of pitching and yawing error components can be measured at the same time, techniques of measuring three types of rotation errors are not still developed.
The present invention proposes a novel method and apparatus for measuring a translation position error of a rectilinear moving body such as a rectilinear table, in addition to rotation angle errors of pitching, yawing and rolling with one method, by utilizing linearity of a laser beam.
The invention has been made in consideration of the above-described circumstances and aims to provide an apparatus for measuring three components of a rotation angle error including pitching, yawing and rolling of a rectilinear moving body such as a rectilinear table in a non-contact manner and at the same time, by utilizing linearity of a laser beam.
BRIEF SUMMARY OF THE INVENTION
In order to achieve the above object, a straightness measuring apparatus for a rectilinearly moving body of this invention comprises: a horizontal, parallel two-surface mirror positioned in a horizontal plane and including two reflection mirrors whose reflection surfaces face each other and are spaced by a distance (2)d; a vertical, parallel two-surface mirror positioned in a vertical plane and including two reflection mirrors whose reflection surfaces face each other and are spaced by a distance (2)d; a light source for generating a laser beam; semi-transparent mirrors for splitting the laser beam into two laser beams; optical path changing reflection mirrors for changing a direction of each laser beam; and position sensors for detecting positions of the laser beam reflected from the horizontal, parallel two-surface mirror and the vertical, parallel two-surface mirror, wherein a direction of the horizontal, parallel two-surface mirror is set so that directions of each normal to a bottom surface of each reflection surface take respectively:
[Expression 5]
m
H1
=(−1/(2), 0, 1/(2)),
m
H2
=(1/(2), 0, 1/(2)) or
m
H1
(1/(2), 0, −1/(2)),
m′
H2
=(−1/(2), 0, 1/(2))
a direction of the vertical parallel two-surface mirror is set so that directions of each normal to a bottom surface of each reflection surface take respectively:
[Expression 6]
mm
V1
=(0, 1/(2), −1/(2)),
m
V2
=(0, −1/(2), 1/(2)) or
m′
V1
(0, −1/(2), 1/(2)),
m′
V2
(0, −1/(2), −1/(2))
and the light source, the semi-transparent mirrors, the optical path changing reflection mirrors and the position sensors are fixed to positions outside of the rectilinearly moving body.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the invention will be described in detail with reference to the accompanying drawings.
Referring to
FIGS. 1 and 2
, reference numeral
1
represents a straightness measuring apparatus
1
. The straightness measuring apparatus
1
has a rectilinear moving body
2
whose straightness is to be measured according to the invention. The rectilinear moving body
2
is, for example, a pulse stage or a rectilinear motion table.
In a rectangular coordinate system, a propagation direction of the rectilinearly moving body
2
is a z-axis, a horizontal direction is an x-axis and a vertical direction is a y-axis. Two parallel two-surface mirrors each having reflection surfaces facing each other, i.e., a horizontal, parallel two-surface mirror
3
and a vertical, parallel two-surface mirror, are mounted on the rectilinearly moving body
2
. The horizontal, parallel two-surface mirror
3
is constituted of two reflection mirrors M
H1
and M
H2
whose reflection surfaces are faced each other and spaced by a distance (2)d. The vertical, parallel two-surface mirror
4
is constituted of two reflection mirrors M
V1
and M
V2
whose reflection surfaces are faced each other and spaced by a distance (2)d. Positioned outside of the rectilinearly moving body
2
are: a light source
5
for generating a laser beam; semi-transparent mirrors BS
1
and BS
2
for splitting a laser beam from the light source
5
into two beams; optical path changing reflection mirrors M
1
, M
2
, M
3
and M
4
for changing the direction of each beam; two pairs of position sensors PS
2
and PS
3
for detecting horizontal and vertical positions of each beam reflected from the parallel two-surface mirrors
3
and
4
; and position sensors PS
1
for detecting the position of a reflection beam from corner cube mirrors CCM. A personal computer (not shown) is also installed for controllably driving the rectilinearly moving body
2
and analyzing position sensor outputs.
It is assumed that while the rectilinearly moving body
2
moves straight, rotation errors of a pitching angle &xgr;, yawing angle &eegr; and a rolling angle &zgr; are generated. The rotation errors are obtained from the following expression 7, by representing position errors in the horizontal and
Director-General of National Institute of Advanced Industrial Sc
Farber Martin A.
Le Uyen-Chau N.
Lee Michael G.
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