Profile measurement using standing wave trapping

Various products have been miniaturized in recent years. And, the measurement technology for surface profile of micro components is highly demanded. Then, we proposed a new measurement technique for surface profile using the standing wave trapping. The high-accuracy scale and the high-sensitive sensor are required in the profile measurement. In our measurement system, the optical trapping particle is used as the sensor. The standing wave pattern is used as the measurement scale, which has wavelength-determined intensity pitch of interference field (λ/2). Therefore, this measurement technique is expected to perform the high-accuracy measurement. It was experimentally found that the vertical measurement range is about 250 μm. The uncertainty of the sensor is ±λ/100. Thus, this technique is capable of measuring large objects in height. When measuring the continuous surface, the sensor particle is scanned in the horizontal direction above the measured surface. The trapped sensor particle in the standing wave field axially moves to follow the measured surface topography. The particle jumps when the surface profile exceeds the pitch of the standing wave pattern. Therefore, the surface profile can be calculated based on the measurement of the particle motional variation. As pre-measurement, the dependency of the scale pitch on measured surface angles was investigated. A microlens was measured with the angle dependency correction. This shows the improvement of the measurement accuracy.