See how easily you can design your own microlens arrays and tapered structures using all-glass gray scale mask technology by reading CMI Product Information No. 01-88 "All-Glass Gray Scale Mask Technology"

CMI has e-beam writers in-house, available write grids are 25nm (i.e. 25 nanometer), 50nm, and 100nm. For good throughput and still very high gray scale resolution, HEBS-glass gray scale masks are typically written with a pixel size of 100nm (i.e. 0.1 micron). Within a 5"x5" pattern area, each of the gray pixels may have an optical density value or a transmittance value selected from more than 500 gray levels. The number of grayscale levels in a HEBS-glass mask is only limited by the accuracy and reproducibility of the clock rates of a vector scan e-beam writer. In the data file for writing an all-glass gray scale mask, each gray level is a layer. For example, a mask written with 100 layers of GDS data file is used to fabricate a 3D microstructure having 100 gray scale height levels.

HEBS-glass plates offer true gray scale photomasks with the highest gray scale resolution possible! CMI Product Information No. 04-100 decribes how All-glass gray scale photomasks offer the highest gray scale resolution when compared to alternative gray scale photomask techniques like halftone masks and photographic emulsion masks.

All-glass gray scale photomasks include HEBS-glass and LDW-glass masks. The all-glass gray scale photomasks which have no coating of any kind, do not have any abrupt change in refractive index in the mask patterns such as those exist in chrome line edges in the conventional chrome masks. As a matter of fact, the boundaries between clear and dark (e.g. chrome) halftone dots cause unwanted scattering or diffraction. Without the undesirable scattering or diffraction, a true gray scale optical density pattern in an all-glass mask is faithfully and reproducibly converted into a corresponding gray scale height pattern in photoresist through an otherwise conventional optical lithographic process, when the conventional binary mask is replaced by an all-glass gray scale mask.

Numerous all-glass gray scale masks (see exemplary masks) were made for a variety of applications.

Among many fabrication techniques that were used to produce microoptical elements, all-glass gray scale mask technology remains the most flexible, versitile, and accurate method. With an all-glass gray scale mask, the fabrication of microoptical elements uses conventional IC fabrication tools. Any existing model of contact aligners, projection printers, and reduction steppers designed for IC fabrication can be used in the gray scale photolithography using an all-glass photomask.

All-glass gray scale photomasks enable economic mass fabrication of 3D microstructures in photoresist, in fused silica, in silicon, and in visible, near infrared and infrared transmitting substrates. Moreover, even for the fabrication of just one mold surface for embossing and compression molding of plastic optical elements, photolithography using an all-glass gray scale photomask is preferred over e-beam or laser beam direct write on photoresist, for both quality and economic advantanges, see CMI Product Information No. 01-88.

Ultimate Quality CGHs - Computer generated holograms (CGHs) with many phase levels are produced from All-Glass Gray Scale Photomasks in one photolithographic step. A gray pixel in a random phase plate may be 0.1 micron, or much larger pixel sizes for economic reason.

Leading Edge Microlens Fabrication - All-glass masks enable users to create traditional as well as new designs of microlens arrays: e.g. 100% fill factor with square or hexagonal aperture, aspheric or spheric lenses, each lenslet in an array can be unique, e.g. Microlenses Designed with Varied Degree of Compound Tilt.

The micro-optical elements produced with an all-glass photomask are proven particularly effective to improve efficiency of imaging, collimation, beam splitting and funneling light into an active area in each pixel of an array, including, for example, a refractive microlens array with 100% fill factor for focusing light onto the optically active part in each detector cell of a CCD or a CMOS Imager, similarly, a refractive microlens array with 100% fill factor to funnel light through the transmissive region of each TFT transistor which turns each pixel in an LCD display on and off giving brighter images, a refractive microlens array for Shack-Hartman wavefront sensor, prealigned arrays of microlenses to collimate light from fibers or from laser diode sources, and much more.

Companies using all-glass photomasks include Panasonic Communications Co. Ltd., Panasonic Boston Laboratoty, ITRI of Taiwan, Advanced Medical Optics, Wavefront Sciences Inc., Rockwell Sciece Center, Seiko Epson, Canon, Nikon, NASA, Sandia National Laboratories, Ricoh, Sony, NTT Communications, Dong Jin Semichem Co. Ltd., Raytheon Company, Teledyne Scientific & Imagining, LLC, De La Rue Group of U.K., Olympus, Samsung, Samsung America, Inc., Alps, Epson, SII of Japan, Yamatake, Asahi, Samsung Electronics, Co., Ltd., Smithsoniam Observatory, Jet Propulsion Laboratories, among many others.

Incorporating grayscale optical elements, better quality consumer products are produced at lower cost. One such example, Panasonic Communications Co. Ltd. introduced in 2007 a 9.5mm height Ultra Slim Multi Drive incorporating a gray scale diffractive optic, as described in proceedings from ISDM-ODS 2008 Hawaii conference. With a non exclusive license from Canyon Materials, Inc. to use LDW-glass blanks to make a grayscale mask and to make a gray scale diffractive optic using the LDW glass gray scale photomask, Panasonic Communications Co. Ltd. (PCC) was the first to successfully mass-produce a 9.5mm height Ultra Slim Super Multi Drive incorporating the grayscale diffractive optic. The technology improved the signal quality by increasing diffraction efficiency of the diffractive optic and brought significant reduction of cost per drive as a result. The greatest technical improvement of the PCC drive is the use of gray scale optics to improve the diffraction efficiency to 85% from 32% of the older version of the PCC drive that used a conventional binary hologram. Gray scale photolithography using LDW-glass gray scale mask enabled mass-production in quality; the RMS shape error being less than 10mm, see fig. 4 of the paper, which can be downloaded here. LDW-glass mask was written using a laser writer similar to LW405 LaserWriter of Microtech.

A cost effective combination of LDW glass together with a laser writer, e.g. LW405 LaserWriter of Microtech, enables customers to produce quickly and with high quality their own gray scale photomasks in house. You may establish a nano-machine shop for the fabrication micro-optical elements by acquiring a laser writer to write your own LDW-glass gray scale photomasks.

Additional Utility of LDW glass - LDW glass may be used for micromachining of micro-optics in a LDW-glass plate using laser direct write followed by an etching step in HF solution to convert gray scale optical density levels in a LDW-glass plate into gray scale height levels in the LDW-glass plate.