Scanning Optical Head with Nontilted Reference Beam: Assuring Nanoradian Accuracy for a New Generation Surface Profiler in the Large-Slope Testing Range

Table 2

Comparison of three scan modes.

Scan mode	Working distance (mm)	BLM (mm)/at test angle (mrad)	Test angle (mrad)	Extra optics	Comment
Scan OH+ nontilted REF (new NSP)	Sample: 50	Sample: ±0.5 mm/±5			Larger test angle +; high accuracy
	(fixed)	±1 mm/±10	±10	N/A
	Ref: 100–1100	Ref: 0 mm
Scan OH+ tilted REF (LTP II)	Sample: 50	Sample: ±0.5 mm/±5			Suitable for plane and; near-plane mirror tests
	(fixed)	±1 mm/±10	±5	N/A
	Ref: 100–1100	Ref: ±11 mm/±5
		±22 mm/±10
Scan pentaprism LTP (NOM)	Sample: 100–1100	Sample: ±11 mm/±5	±5	Pentaprism	Suitable for plane and; near-plane mirror test
		±22 mm/±10