Contactless profiling method

• US 4,949,024 A
• Filed: 08/01/1989
• Issued: 08/14/1990
• Est. Priority Date: 12/10/1987
• Status: Expired due to Fees

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Matsuura, Hitoshi
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ip, Paul
• Application Number:
  US07/392,921
• Time in Patent Office: 378 Days
• Field of Search: 318/567, 318/570-578, 318/640, 318/568.15, 318/594, 356/370, 356/371, 356/372, 356/375, 356/376, 356/377, 356/369, 356/380, 356/386, 356/387, 364/474.03, 364/474.08, 364/513, 364/191, 364/193
• US Class Current: 318/567
• CPC Class Codes: B23Q 35/128 Sensing by using optical means
• CPC Class Codes: G05B 2219/37425 Distance, range
• CPC Class Codes: G05B 2219/37554 Two camera, or tiltable camera to detect different surfaces of the object

Abstract

A method for contactless profiling is performed while tilting an optic axis of a distance measuring probe (PB), which is capable of measuring a distance optically, by an angle θ from the vertical axis. When a point (P₁) at which distance measurement is impossible is reached and measurement of distance the thus becomes impossible, the movement of the distance measuring probe (PB) is halted and the distance measuring probe is rotated to tilt the optical axis thereof from the vertical axis by the angle θ in the opposite direction, after which contactless profiling is resumed. Thereafter, when the points (P₂, P₃) at which distance measurement is impossible are reached, the distance measuring probe (PB) is made to perform the same operations so that contactless profiling may continue.

Claims

1. A contactless profiling method for tracing a model surface using an optical distance measuring probe capable of contactlessly measuring a distance L to the model surface, said method comprising the steps of:

(a) performing contactless profiling while tilting an optical axis of the optical distance measuring probe by an angle θ

in a first direction from a vertical axis;

(b) stopping movement of the optical distance measuring probe if measurement of the distance becomes impossible; and

(c) tilting the optical axis of the optical distance measuring probe from the vertical axis by the angle θ

in a second direction after said stopping in step (b); and

(d) resuming contactless profiling after said tilting in step (c).

2. A contactless profiling method according to claim 1, wherein the optical distance measuring probe outputs a distance measurement signal, and

wherein said method further comprises the steps of:

(e) indicating distance measurement is possible, when a light quantity detected by the optical distance measuring probe is greater than a predetermined value, with the distance measurement signal; and

(f) determining whether the distance measurement is possible/impossible based on the distance measurement signal.

3. A contactless profiling method according to claim 1, wherein said method further comprises the step (e) calculating coordinates X_p, Z_p of a measurement point on the model surface when the optical axis of the optical distance measuring probe is titled from the vertical axis by the angle θ

in a direction of travel or by the angle -θ

in a direction opposite the direction of travel in accordance with the following equations;

space="preserve" listing-type="equation">X.sub.p =X.sub.A ±

L·

sin θ

space="preserve" listing-type="equation">X.sub.p =Z.sub.A ±

L·

cos θ

using coordinates X_A, Z_A of a present position of the optical distance measuring probe.

4. A contactless profiling method according to claim 3, wherein step (c) comprises the substep of updating the present position of the optical distance measuring probe after said tilting.

5. A contactless profiling method according to claim 4, wherein said updating of the present position is based on the following formula X_A =X_A 2·

L·

sin θ

.

6. A contactless profiling method according to claim 4, wherein said updating of the present position is based on the following formula X_A =X_A -2·

L·

sin θ

.

7. A contactless profiling method according to claim 1, wherein said method further comprises the step of profile machining a workpiece in accordance with the distance measured.

8. A method for contactlessly tracing a model surface using an optical distance measuring probe, the optical distance measuring probe has a vertical axis and an optical axis, said method comprising the steps of:

(a) tilting the optical distance measuring probe from the vertical axis by a predetermined angle;

(b) determining whether a distance from the optical distance measuring probe to the model surface can be measured by the optical distance measuring probe having a present tilt;

(c) tilting the optical distance measuring probe from the vertical axis by the predetermined angle in a direction opposite to the present tilt when said determining in step (b) determines the distance cannot be measured; and

(d) measuring the distance from the optical distance measuring probe to the model surface.

9. A method according to claim 8, wherein said method further comprises the step of repeating steps (b)-(d) until the model surface has been completely traced.

10. A method according to claim 8, wherein said method further comprises the steps:

(e) computing a surface point of the model surface based on the distance measured in step (d); and

(f) processing the surface point to correct for the present tilt in the optical distance measuring probe.

11. A method according to claim 10, wherein said method is performed by a tracer control apparatus having a processor and a memory unit, and

wherein said method further comprises the step of storing the surface point in the memory unit for machining of a workpiece at a later time.

12. A method according to claim 10,

wherein step (e) includes the steps of:

(e1) computing first and second axis position data of the optical distance position measuring probe; and

(e2) computing first and second surface point coordinates of the surface point, and

wherein step (f) includes the steps of;

(f1) correcting the first surface point coordinate by adding, when the optical axis is tilted in a direction opposite to a traveling direction of the optical distance measuring probe, or subtracting, when the optical axis is tilted in the traveling direction, a first quantity from the first axis position data; and

(f2) correcting the second surface point coordinate by adding, when the optical axis is tilted in a direction opposite to a traveling direction of the optical distance measuring probe, or subtracting, when the optical axis is tilted in the traveling direction, a second quantity from the second axis position data.

13. A method according to claim 12, wherein the first quantity is determined by multiplying the distance by sin of the predetermined angle, and the second quantity is determined by multiplying the distance by cos of the predetermined angle.

14. A method as recited in claim 8, wherein said method further comprises the step of profile machining a workpiece in accordance with the distance measured in step (d).

15. A method according to claim 8, wherein the optical distance measuring probe includes a light-emitting element and a light-receiving element, and

wherein said determining in step (b) comprises the steps:

(b1) emitting light from the light-emitting element onto the model surface;

(b2) receiving a quantity of reflected light from the model surface at the light-receiving element; and

(b3) comparing the quantity of reflected light with a predetermined quantity.

16. A method according to claim 8, wherein the optical distance measuring probe includes has a present position, and

wherein step (c) comprises the step of updating the present position of the optical distance measuring probe after said tilting.

17. A system for contactlessly tracing a model surface, comprising:

distance measuring means, having optical axis with a present tilt about a vertical axis by a predetermined angle, for determining whether a distance to the model surface can be measured, and for measuring the distance to the model surface;

rotation drive means for tilting said distance measuring means about the vertical axis by the predetermined angle in a direction opposite to the present tilt when said distance measuring means determines the distance cannot be measured at the present tilt; and

control means for controlling the tilting by said rotation drive means when said distance measuring means determines the distance cannot be measured at the present tilt.

18. A system according to claim 17, wherein said control means comprises:

means for computing a surface point of the model surface based on the distance measured by said distance measuring means;

means for processing the surface point to correct for the present tilt of said measuring means; and

means for updating the present position of said distance measuring means after the tilting by said rotation drive means.