Confocal Measurement
The principle
The confocal point sensor uses a point light
source and detector pinhole to discriminate depth.
The laser beam emitted from the point light source is focused on a specimen
through an objective lens that moves rapidly up and down. The maximum light
intensity occurs when the specimen lies within the focal plane of the objective.
As the objective moves closer to or farther from the specimen, however, the
reflected light reaching the pinhole is defocused and does not pass through
it. As a result, the quantity of light received by a detector behind the pinhole
decreases rapidly. A detection signal is only generated when the maximum of
light goes through the pinhole.
A precise height measurement of the illuminated point is achieved by continuously
scanning along the z-axis.
 |
| Measurement principle of the confocal point sensor |
The advantages
The confocal measurement principle ensures high
reliability even on steep edges and robustness against optical artifacts. This
enables the LT8010 sensor to measure complex surface structures as well as structures
with high aspect ratio as they occur in MEMS.
The LaserScan LT8010 can be used for various measuring
tasks from fast and precise measurement of large surfaces to only single profiles.
The AutoScan allows for automation of those measuring
tasks.
Specifications
| Sensor |
Camera |
| Spot size [µm] |
2 |
Integrated off-axis camera |
| Vertical resolution [µm] |
0,1 |
Magnification |
200x |
| Measurement frequency [Hz] |
1400 |
|
| Stand off [mm] |
5 |
Laser |
Class II |
| Linearity [%] |
±0.5 |
Wavelength [nm] |
670 |
