Design and fabrication of a hybrid diffractive optical device for multiple-line generation over a wide angle

A new hybrid optical device that is capable of splitting a monochromatic la ser beam into an arbitrary number of lines over a wide angle is presented. It consists of a binary surface-relief computer-generated phase hologram an d a continuous parabolic surface-relief grating. In this device the phase h ologram serves to generate three small, parallel lines while the continuous parabolic surface-relief phase grating acts as an array of diverging parab olic lenses to widen these Lines. The binary surface-relief was generated i nto one side of a quartz substrate through a plasma-etching process, and th e parabolic profile was generated into a thick photoresist deposited on the other side of the quartz substrate. Calculations showed that a diverging p arabolic lens with a f-number of 0.5 would deliver the desired optical patt ern of multiple beams distributed over 90 degrees. A surface-relief depth o f 6.0 mum was calculated with consideration of the phase distributions of s uch lens. The parabolic profiles were fabricated in a 10-mum-thick photores ist, by use of a contact exposure through a mask with a space pattern of re petitive 4- and 6-mum Lines. He-Ne laser light was passed through a device that generated three parallel lines over a 90 degrees angle. The resulting diffraction patterns were characterized, and a satisfying result was obtain ed. The resulting multiple-line pattern can be used in robot vision and oth er applications. (C) 2001 Optical Society of America OCIS code: 050.1970.