Camera modules are incorporated in a wide array of devices. Consumer electronics devices such as mobile phones, tablets, and laptops generally include a compact camera module. The majority of such devices are equipped with a lens system composed of plastic lenses in a fixed configuration. Typical camera modules have pixel resolution around 2 megapixels or higher. With such a large number of pixels sharing incident light, the associated lens system must have high light collection efficiency in order to generate a sufficiently bright image. The light collection efficiency may be expressed in terms of the F-number, which is defined as the ratio of the effective focal length (EFFL) of the lens system to the entrance pupil diameter (D), that is, F=EFFL/D. Thus, the F-number is a measure of the portion of light from a scene that is collected and imaged by the lens system. A low F-number is synonymous with a high-collection efficiency. To meet cost constraints and performance demands, many camera modules are composed of three plastic lenses configured to yield a relatively low F-number and acceptable imaging properties. The plastic lenses are mass produced using injection molding technology and assembled, together with an image sensor and electronic circuitry, to form a camera module.
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