None of the pre-determined positions for length measurement system tests in the Standard is sensitive to vertical angle encoder eccentricity along Z, because the symmetrical positioning produces error vectors that only translate/rotate the length.
Two-face system tests: This term is not sensitive to two-face system tests.
Length measurement system tests: Because range measurements are either smaller or larger than the true value, all length measurement system tests produce length results that are either smaller or larger than the true value.
Two-face system tests: Two-face system tests are sensitive to odd order harmonic errors while they are not sensitive to even order harmonic errors.
The Standard however does not specify length measurement system tests at any azimuthal angle other than 0[degrees], 90[degrees], 180[degrees] and 270[degrees].
Sensitivity matrix for length measurement system tests (shaded boxes show non-zero sensitivity) (a) X1t X1m X2 X3 X4t X5 X6x HOR 1 m 0 1 0.
Two-face system tests are therefore a critical component in a performance evaluation of laser trackers.
The convolution of the angle errors into a distance error may result in unification of the reporting method with length measurement system tests within the Standard.
For the tracker mechanical configuration we discussed in this paper, there are only a few misalignment parameters that are insensitive to two-face system tests (vertical angle encoder eccentricity along Z, bird bath, and second order scale error).
From the discussion in the previous section and the sensitivity matrix in Table 1, it is clear that certain misalignment parameters are detected by some of the length measurement system tests described in the Standard (three out of four encoder eccentricity parameters, transit tilt, transit offset, and some second order scale error components).
We propose in this section some new length measurement system tests that demonstrate improved sensitivity to some of the geometric misalignment parameters previously undetected.
8) is particularly sensitive to two misalignment parameters generally not sensitive to the length measurement system tests described in the Standard - vertical encoder eccentricity along Z and vertical index offset.