Adjustable apodized lens aperture

Abstract

An adjustable apodized lens aperture is described which is constructed using photochromic material. As the excitation energy increases, the aperture constricts so as reduce the amount of light through the aperture. As the excitation energy decreases, the aperture dilates so as increase the amount of light through the aperture.

Description

RELATED APPLICATION DATA [0001] The present application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 60 / 753,242 filed on Dec. 21, 2005 (Attorney Docket No. SAY1P012P), and U.S. Provisional Patent Application No. 60 / 858,909 filed on Nov. 13, 2006 (Attorney Docket No. SAY1P012P2), the entire disclosures of both of which are incorporated herein by reference for all purposes.BACKGROUND OF THE INVENTION [0002] The present invention relates to optical systems and, in particular, to adjustable apertures for camera lenses. [0003] Since the early days of photography, camera manufacturers have given photographers access to critical adjustments in order to get correctly exposed pictures. These adjustments are commonly referred to by photographers as “shutter speed” (adjustable exposure time of the film), “film speed” (choice of film sensitivity), and lens aperture (adjustable diaphragm in the lens). In addition to affecting the film exposure, these adjustme...

AI Technical Summary

Benefits of technology

[0014] According to yet another class of embodiments, an ultraviolet (UV) blocking element is configured to inhibit UV energy from impinging on at least a portion of a front surface of the photochromic material through which the visible light reaches the apodized aperture. According to a subset of these embodiments, the UV blocking element has a transmission characteristic for UV energy which increases along a radius of the apodized aperture. According to another subset of these embodiments, the UV blocking element blocks substantially all UV energy from impinging on the front surface of the photochromic material.

[0015] According to some of the latter subset of these

Problems solved by technology

In digital cameras, the electronic shutter control (adjustable integration time of the image sensor) often replaces the mechanical shutter but does not eliminate the need for the lens aperture adjustment.

Although the correct exposure can be achieved by adjusting the electronic shutter alone, the depth of field cannot be affected by it.

The main reason for not using a lens aperture adjustment is cost.

That is, mechanical irises can be as inexpensive as $1.50, which is very affordable in the design of a $300 digital camera but prohibitively expensive for a $4.50 camera module intended for computer or cellular telephone applications.

The consequence was that they neither produced good quality images at low-light level (objectionable shot noise and readout noise) nor at high-light level (poor depth of field and reduced sharpness due to lens aberrations).

Unfortunately, current cell phone camera modules are optimized for worst-case conditions (low light level imaging) and do not produce images with sufficient sharpness and depth of field, even under good illumination conditions such as outdoor imaging with adequate daylight.

This issue is further aggravated by price pressure and market demand for a larger number of pixels.

This requirement conflicts with the need for a sharper lens (since a wider aperture results in greater lens aberrations) and for an increased depth of field (since a wider aperture results in a reduced depth of field).

Unfortunately, the sharpness restoration algorithms also introduce a significant amount of noise in the image.

It is clear that none of these solutions really eliminate the need for an adjustable lens aperture but there are no suitable technical implementations fulfilling this need.

Current mechanical irises are too expensive, too bulky, too fragile, and too power-hungry to satisfy the expected one-billion cell phone camera module market.

Mechanical irises also have another serious technical drawback: diffraction through their circular aperture significantly degrades the image sharpness for small aperture settings, e.g., high f numbers such as f / 5.6 or higher.

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