Lens array and method of making same

Abstract

Systems and methods are provided for a lens or microlens array or non-spherical lens with or without an integrated sensor unit. A dielectric between a substrate and a lens material has curved recesses, which are filled in by the lens material. Light enters the lens material layer and is focused by the curved recess portions.

Description

BACKGROUND [0001] 1. Field of the Invention [0002] The present invention relates generally to microlens arrays and optical lenses, and more particularly to methods for manufacturing microlens arrays or non-spherical lenses. [0003] 2. Related Art [0004] Microlens arrays provide optical versatility in a miniature package for imaging applications. Traditionally, a microlens is defined as a lens with a diameter less than one millimeter; however, a lens having a diameter as large as five millimeters or more has sometimes also been considered a microlens. [0005] There are many conventional methods for manufacturing microlens arrays, such as using reflow or diffusion. FIGS. 1A-1C show a typical sequence of steps for making a microlens array by depositing material, patterning, and reflowing. In FIG. 1A, a photosensitive layer 10, such as a photosensitive resin, is formed on a planarization layer 12 over a silicon substrate (not shown). The material of the photosensitive layer is used to for...

AI Technical Summary

Benefits of technology

"The present invention provides improved microlens arrays and processes of forming them. The microlens array is formed on a sensor array, resulting in an integrated microlens / sensor device. The process involves depositing a dielectric layer over the sensor array, patterning a photosensitive dielectric layer, and then removing selected portions of the patterning layer to expose areas of the dielectric layer overlying the individual sensors where microlenses are to be formed. An inorganic lens material is then deposited over the dielectric layer to form an integrated array of microlenses and sensors. The microlens array has advantages such as being easier and less expensive to fabricate, having flexible lens shapes, and improving sensor sensitivity and color quality. The resulting microlens array can be used for various applications such as small display screens for cameras or digital cameras to large display screens for projection screens or billboards. The invention allows for high throughput with consistent characteristics between each array."

Problems solved by technology

This color distortion increases with time due to oxidation of the resin.

Another disadvantage is that the resolution with which the photosensitive resin can be patterned is limited by the thickness of the resin layer.

The thicker the resin layer, the farther apart the microlenses in the array, which reduces the light collection efficiency of the array.

Consequently, it is difficult to obtain the highest possible collection efficiency with microlens arrays fabricated in this manner.

Yet another disadvantage results from the fact that as the curvature radius of the microlens becomes small, the incident light is focused on a point near the microlens.

Moreover, because a microlens formed in a rectangular shape has a significant difference between its curvature radius in the width and the length directions, it is difficult to focus incident light on the corresponding photodiode without error, and a part of the light is focused on the planarization layer or color filter layer between the photodiode and the microlens, causing loss of light and deterioration of sensitivity and resolution.

One disadvantage to forming microlens arrays using diffusion is that control of the thickness along the optical axis is limited.

Several processing steps are needed to form the separate microlens layer 32, filter layer 40, and sensor layer 42, which increase cost and time.

The layers also increase the separation between the microlenses and the sensors, which can increase crosstalk between pixels, due in part to light impinging on adjacent sensors instead of the desired sensor.

However, the fabrication of non-spherical lenses is complicated and can only be done through skilled manual operation by highly trained professionals.

This can be time consuming and costly.

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