The long trace profilometer (LTP) from Ocean Optics
(shown above) measures the slope and curvature of mirror surfaces
along one dimension using a zero-path difference interferometer. A
solid state red laser source is used to probe the mirror under test.
The CLS LTP can measure optical surfaces up to 1.5 meters in length,
covering the range of spatial samplings from 2 - 1500 mm and spatial
frequencies of 0.00033 - 0.25 cycles/mm.
Surfaces of virtually any shape can be measured in
situ, as long as the surface slope change is within the ± 5
milliradian acceptance angle of the LTP optical system, with a
sensitivity of 0.1 mrad and 0.5 nm in
height. Dr. Peter Takacs and staff developed the LTP at Brookhaven
National Laboratory (BNL). BNL still holds a US patent on this
instrument.
The instrument is mounted on a vibration isolation
table to minimize the effects from external vibrations and enclosed
in a plastic curtain while measurements are taken (not shown in
photograph) in order to reduce air turbulence effects on the optical
head. The bearing has recently been upgraded from a crossed-roller
bearing to a more precise linear air bearing.
Above is shown the height profile of a "reference"
spherical mirror, taken with the LTP. From the center of the mirror,
the edges are raised approximately 20 onmousedown="change_color('s13','sub_menu_over')"
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The long trace profilometer (LTP) from Ocean Optics
(shown above) measures the slope and curvature of mirror surfaces
along one dimension using a zero-path difference interferometer. A
solid state red laser source is used to probe the mirror under test.
The CLS LTP can measure optical surfaces up to 1.5 meters in length,
covering the range of spatial samplings from 2 - 1500 mm and spatial
frequencies of 0.00033 - 0.25 cycles/mm.
Surfaces of virtually any shape can be measured in
situ, as long as the surface slope change is within the ± 5
milliradian acceptance angle of the LTP optical system, with a
sensitivity of 0.1 mrad and 0.5 nm in
height. Dr. Peter Takacs and staff developed the LTP at Brookhaven
National Laboratory (BNL). BNL still holds a US patent on this
instrument.
The instrument is mounted on a vibration isolation
table to minimize the effects from external vibrations and enclosed
in a plastic curtain while measurements are taken (not shown in
photograph) in order to reduce air turbulence effects on the optical
head. The bearing has recently been upgraded from a crossed-roller
bearing to a more precise linear air bearing.
Above is shown the height profile of a "reference"
spherical mirror, taken with the LTP. From the center of the mirror,
the edges are raised approximately 20 onmousedown="change_color('s13','sub_menu_over')"
onmouseover="change_color('s13','sub_menu_over')"
onmouseout="change_color('s13','sub_menu')"
href="Template/photo_gallery/photo_gallery.htm">
The long trace profilometer (LTP) from Ocean Optics
(shown above) measures the slope and curvature of mirror surfaces
along one dimension using a zero-path difference interferometer. A
solid state red laser source is used to probe the mirror under test.
The CLS LTP can measure optical surfaces up to 1.5 meters in length,
covering the range of spatial samplings from 2 - 1500 mm and spatial
frequencies of 0.00033 - 0.25 cycles/mm.
Surfaces of virtually any shape can be measured in
situ, as long as the surface slope change is within the ± 5
milliradian acceptance angle of the LTP optical system, with a
sensitivity of 0.1 mrad and 0.5 nm in
height. Dr. Peter Takacs and staff developed the LTP at Brookhaven
National Laboratory (BNL). BNL still holds a US patent on this
instrument.
The instrument is mounted on a vibration isolation
table to minimize the effects from external vibrations and enclosed
in a plastic curtain while measurements are taken (not shown in
photograph) in order to reduce air turbulence effects on the optical
head. The bearing has recently been upgraded from a crossed-roller
bearing to a more precise linear air bearing.
Above is shown the height profile of a "reference"
spherical mirror, taken with the LTP. From the center of the mirror,
the edges are raised approximately 20 mm.
Highlighted in blue, to the left of the height profile curve, is
shown the calculated radius of curvature of this mirror - in this
case 9.8354 meters. Although steep radii of curvatures like this can
be measured using the LTP, in general the LTP is used to measure the
opposite extreme for synchrotron mirrors (where the radius of
curvature is several kilometers).
Although this screen capture shows the height profile, the
instrument can also display the so-called "slope error" - i.e. the
difference in slope between the surface and the desired figure (e.g.
cylinder, sphere).
