Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
  • G02B3/0006—Arrays
  • G02B3/0012—Arrays characterised by the manufacturing method
  • G02B3/0031—Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
  • G02B3/0006—Arrays
  • G02B3/0037—Arrays characterized by the distribution or form of lenses
  • G02B3/0043—Inhomogeneous or irregular arrays, e.g. varying shape, size, height
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
  • G02B3/0006—Arrays
  • G02B3/0037—Arrays characterized by the distribution or form of lenses
  • G02B3/0056—Arrays characterized by the distribution or form of lenses arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14601—Structural or functional details thereof
  • H01L27/14625—Optical elements or arrangements associated with the device
  • H01L27/14627—Microlenses

Definitions

• the present invention relates to arrays of microlenses having high focusing efficiencies. It also relates to methods for fabricating such arrays.
• the invention is applicable to the efficient focusing of laser light into optical fibers, light diffusion, and controlled scattering of coherent or incoherent light for projection and transmissive displays, among other applications.
• the "fill factor" of a microlens array is the ratio of the sum of the areas within the unit cells occupied by microlenses to the sum of the areas of the unit cells.
• the "focusing efficiency" of a microlens array is the sum of the measured light intensities at the focal points of the microlenses divided by the sum of the light intensities impinging on the unit cells of the array for an array illuminated along its optical axis by a collimated, substantially spatially incoherent light source, e.g., a collimated white light source. As will be recognized by those skilled in the art, this is a "Strehl-type" definition of focusing efficiency.
• microlenses utilize the entire surface for focusing. In this way, essentially all incident light can be controlled by the array.
• the array is said to possess a 100% fill factor.
• Close packing of microlenses implies a fill factor equal to 100%, which means that the internal boundaries between neighboring microlenses are in close contact.
• a simple example of close packing is a hexagonal array. Other arrangements, such as square arrays, can also be close packed. It is typical to find in both the scientific and patent literature arrays of microlenses that have fill factors below 100%.
• a high focusing efficiency for an array of microlenses depends on two factors: (1) a high fill factor, and (2) accurate reproduction of the desired lens profiles. Both factors are necessary and neither factor alone is sufficient.
• a high fill factor can be achieved by a process that alters all parts of a resist film, but if the alterations do not correspond to the desired lens profiles, the focusing efficiency of the array will still suffer since the parts of the resist film that have the inaccurate profiles will not focus incident light properly.
• accurate reproduction of a desired lens profile with the individual microlenses spaced far apart also results in low foc ising efficiency, in this case as a result of light passing through the spaces between microlenses.
• the invention is practiced by using a substrate typically made of glass to support a first medium to generate an initial master (initial mold), which is later used to accurately replicate the desired microlens array in a cost-effective fashion. More particularly, a photosensitive positive resist film is deposited on the substrate to an appropriate thickness consistent with the desired thickness for the final microlens array.
• the positive resist is preferably of the low- contrast kind such that, when exposed to light, a smoothly varying surface- relief profile can be produced.
• the concave surface- relief structure can be used to prepare an intermediate master
• FIG. 4A and FIG. 4B show the effect of convolution in the fabrication of convex structures.
• FIG. 5A and FIG. 5B illustrate the interaction of a hard fabrication tool in relation to a convex and concave array, respectively.
• FIG. 6 illustrates a technique for estimating the focusing efficiency of the microlens units of an array fabricated in convex form.
• each microlens in the array needs to be produced in the positive photoresist in concave form. Only in this way is it possible to reduce significantly the rounding effect observed when microlenses are fabricated in convex form. This is so because the fabrication process itself introduces features into a surface- relief profile that are undesirable.
• Eq. (1) represents the mathematical function describing the desired surface relief
• g represents the mathematical form of the writing laser beam
• S represents the fabricated surface area
• (x,y) denotes a point on the surface of the photosensitive film
• F represents the final surface shape.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Optical Elements Other Than Lenses (AREA)
• Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
• Viewfinders (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=22830476

Family Applications (1)

Country Status (7)

Cited By (1)

Families Citing this family (3)

Family Cites Families (23)

• 2001
  • 2001-07-30 AU AU2001283514A patent/AU2001283514A1/en not_active Abandoned
  • 2001-07-30 KR KR1020027004154A patent/KR100878966B1/ko active IP Right Grant
  • 2001-07-30 EP EP01962321A patent/EP1218777A4/de not_active Withdrawn
  • 2001-07-30 CN CNB018022359A patent/CN1200304C/zh not_active Expired - Lifetime
  • 2001-07-30 JP JP2002515480A patent/JP2004505307A/ja active Pending
  • 2001-07-30 WO PCT/US2001/041475 patent/WO2002010805A1/en active Application Filing
  • 2001-07-31 TW TW093126107A patent/TWI241415B/zh not_active IP Right Cessation
  • 2001-07-31 TW TW090118831A patent/TWI238266B/zh not_active IP Right Cessation

Non-Patent Citations (2)

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