Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
1999-07-19
2001-10-23
Ngô ;, Ngâ ;n V. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S232000, C257S233000
Reexamination Certificate
active
06307243
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a microlens array for use in a solid-state image sensor and in particular to a microlens array having an improved fill factor, and a method for producing the same.
BACKGROUND OF THE INVENTION
Solid-state image sensors, also known as imagers, were developed in the late 1960s and early 1970s primarily for television image acquisition, transmission, and display. An imager absorbs incident radiation of a particular wavelength (such as optical photons, x-rays, or the like) and generates an electrical signal corresponding to the absorbed radiation. There are a number of different types of semiconductor-based imagers, including charge coupled devices (CCDs), photodiode arrays, charge injection devices (CIDs), hybrid focal plan arrays, and CMOS imagers. Current applications of solid-state imagers include cameras, scanners, machine vision systems, vehicle navigation systems, video telephones, computer input devices, surveillance systems, auto focus systems, star trackers, motion detector systems, image stabilization systems and data compression systems for high-definition television.
These imagers typically consist of an array of pixel cells containing photosensors, where each pixel produces a signal corresponding to the intensity of light impinging on that element when an image is focused on the array. These signals may then be used, for example, to display a corresponding image on a monitor or otherwise used to provide information about the optical image. The photosensors are typically phototransistors, photoconductors or photodiodes, where the conductivity of the photosensor or the charge stored in a diffusion corresponds to the intensity of light impinging on the photosensor. The magnitude of the signal produced by each pixel, therefore, is proportional to the amount of light impinging on the photosensor.
It is known in the art to use a microlens array with an imager array, wherein the microlens array comprises a convex microlens for each pixel. The microlenses refract incident radiation from the circuitry region of the pixel to the photosensor region, thereby increasing the amount of light reaching the photosensor and thereby increasing the fill factor of the pixels. Other uses of microlens arrays include intensifying illuminating light on the pixels of a nonluminescent display device such as a liquid crystal display device to increase the brightness of the display, forming an image to be printed in a liquid crystal or light emitting diode printer, and as focusing means for coupling a luminescent device or a receptive device to an optical fiber.
Despite the use of microlens arrays, a large amount of light incident on an imager is not directed onto the photosensor due to the geometry of the microlens array. In particular, light incident on the space between individual lenses (the lens-lens space), and on the edges of the pixel beyond the edges of an individual lens remains uncaptured by the microlens, and never impacts the photosensor. Additionally, the typical practice of forming the microlens array on a separate substrate from the pixel array leads to problems of lens-pixel alignment that results in additional lost light.
There is needed, therefore, a microlens array having an improved fill factor formed on the same substrate as a pixel array. A simple method of fabricating a microlens array having an improved fill factor is also needed.
SUMMARY OF THE INVENTION
The present invention provides a microlens array for use in a solidstate imager having a pixel array, wherein each microlens of the microlens array may correspond to a pixel cell of the imager pixel array. Each microlens consists of two layers: a lower refractive layer, and an upper insulation layer. The refractive layer is formed of transparent material with a suitable refractive index, which may be an optical thermoplastic such as polymethylmethacrylate, polycarbonate, polyolefin, cellulose acetate butyrate, or polystyrene, a polyimide, a thermoset resin such as an epoxy resin, a photosensitive gelatin, or a radiation curable resin such as acrylate, methacrylate, urethane acrylate, epoxy acrylate, or polyester acrylate. The insulation layer is radiation-transparent and assists in capturing light at the edges of the pixel, thereby improving the fill factor of the microlens array. Suitable materials for the insulation layer include silicon insulators such as silicon oxide, silicon nitride, or silicon oxynitride that have been formed by a low temperature process. Also provided are methods for forming the microlens array of the present invention.
Additional advantages and features of the present invention will be apparent from the following detailed description and drawings which illustrate preferred embodiments of the invention.
REFERENCES:
patent: 5118924 (1992-06-01), Mehra et al.
patent: 5298366 (1994-03-01), Iwasaki et al.
patent: 5300263 (1994-04-01), Hoopman et al.
patent: 5384231 (1995-01-01), Johnson et al.
patent: 5420634 (1995-05-01), Matsumoto
patent: 5453876 (1995-09-01), Hamada
patent: 5479049 (1995-12-01), Aoki et al.
patent: 5559336 (1996-09-01), Kosai et al.
patent: 5610390 (1997-03-01), Miyano
patent: 5666175 (1997-09-01), Spitzer et al.
patent: 5693967 (1997-12-01), Park et al.
patent: 5701008 (1997-12-01), Ray et al.
patent: 5796154 (1998-08-01), Sano et al.
patent: 5844289 (1998-12-01), Teranishi et al.
patent: 6040591 (2000-03-01), Otsuka
patent: 6104021 (2000-08-01), Ogawa
patent: 6171883 (2001-01-01), Fan et al.
Dickstein , Shapiro, Morin & Oshinsky, LLP
Micro)n Technology, Inc.
Ngô ; Ngâ ;n V.
LandOfFree
Microlens array with improved fill factor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microlens array with improved fill factor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microlens array with improved fill factor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2567191