I like to do project in laser measurement system. My objective is to eliminate or reduce the cosine error, abbe error in Laser measurement system. I have Rhenishaw XL80 system.
Please tell the procedure to eliminate that particular error. And help me to complete my project.
Dear Joshua,
Let me try to help you.
# In order to eliminate or reduce the cosine error, in my opinion, you should have to tilt your laser head (pitch direction only) so that the misalignment angle (theta) is sufficiently small. You can do that by trial and error.
# In order to eliminate or reduce the abbe error, in my opinion, you should have to reduce or remove abbe offset (d). Abbe offset (d) is sufficiently small. In my understanding, there are any 2 (two) methods, i.e. Zero abbe offset configuration and Abbe error compensation. Please see on the attachment file. The disadvantage of Zero Abbe offset configuration is the system size becomes large. For Abbe error compensation, I did not have experience with it. I am still learning about Abbe error compensation. Generally, you need a double pass interferometer. I suggest you read the publication from Dr. Jong-Ahn Kim. I remember that he published a paper in 2012 about angular compensation to remove abbe error. He is an expert in this field.
When You have Renishaw's laser, You should have a switchable head with two thick of beam. For position error detection purpose: Easy procedures: 1. Switch beam to thin size 2. Put on moveable retroreflector a cup with white circle up. 3. Move to close position (start) 4. Center laser with the screws in the middle of the circle (rather by translations not rotations) 5. Move to end position 6. Center laser with the rotation in the middle of the circle (Repeat points 3-5 until You didn't see any differences [in most case several times]) More complicated procedure: 1. Switch beam to thin size and blink receiver (white circle but on the laser) 2. Move retroreflector to start position 3. Center with the translation movements the bean on white circle on the laser 4. Move to end position 5. Center with the rotations of the beam on the white circle on the laser Repeat points (2-5 several times) until You didn't see any difference or very small differences.
Please remember that Abbé cosine error has quite small impact on the measurement results.
If You want to compare two interferometers it's enough to put both on the same way. But beams can crossed.
Have a look at NPL Good Prcatice Guide Number 80. It is a free download from the NPL website www.npl.co.uk
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