Lens Polishing with I-Scan

Measure pressure distribution for magnetorheological finishing of precision optical surfaces.

Pressure Mapping for Magnetorheological Finishing of Precision Optical Surfaces

Conventional polishing typically involves abrasives and backing materials that result in minute cracks in the glass surface that translate into impairment of theoretical optical performance. Magnetorheological (MR) fluids are micrometer sized magnetic particles suspended in a carrier fluid, and “stiffened” by a magnetic field. There is no backing material.

Sensor model 5051, shown in the inset of Figure 1, measures the forces normal to a stationary part due to hydrodynamic flow. Figure 2 shows a top view and oblique view of the “D” shaped removal “spot,” representative of material removal without part rotation. Figure 3 shows a two dimensional pressure map provided by the I-Scan^® System. The 5051 sensor and I-Scan pressure mapping system facilitates experimentation with different magnetic fields, wheel rotation rates, and other geometric variations to optimize the polishing process.


Figure 1 shows a MR fluid discharge nozzle on the left, and rotation of the wheel takes it to the right. A strong magnetic field “stiffens” the flow so it polishes the optical surface as desired.	Figure 2.

Magnetorheological finishing (MRF) of precision optical surfaces offers the promise of improved surface characteristics compared to conventional polishing. Careful control of several factors including impact pressure distribution is crucial to achieving this potential. Properties of MRF in the polishing zone are difficult to study because the fluid is opaque, and the complex interactions of particles in the magnetic field are difficult to see or model with other techniques.

Figure 3:

Lens Polishing Pressure Measurement Software

Typical Pressure Sensors used for Lens Polishing

Sensor Model 5051

Sensing Area Total

Width Height Sensels Sensel Density

2.20 in. 2.20 in. 1,936 400.0 in.²

55.9 mm 55.9 mm 1,936 62.0 cm²
Sensor Model 5076

Sensing Area Total

Width Height Sensels Sensel Density

3.30 in. 3.30 in. 1,936 177.8 in.²

83.8 mm 83.8 mm 1,936 27.6 cm²
Sensor Model 5101

Sensing Area Total

Width Height Sensels Sensel Density

4.40 in. 4.40 in. 1,936 100.0 in.²

111.8 mm 111.8 mm 1,936 15.5 cm²

View all of Tekscan’s Pressure Sensors

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Sensing Area				Total
Width		Height		Sensels	Sensel Density
2.20	in.	2.20	in.	1,936	400.0	in.²
55.9	mm	55.9	mm	1,936	62.0	cm²

Lens Polishing with I-Scan

Pressure Mapping for Magnetorheological Finishing of Precision Optical Surfaces

Typical Pressure Sensors used for Lens Polishing

I-Scan® System

High Temperature Pressure Sensors Now Available!

I-Scan^® System