Optical zoom & smartphones – the next big thing?

April 23, 2014
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Smartphone cameras are making huge strides these days. Image clarity is on the up, while noise and crosstalk in smaller sensors is gradually being reduced. Despite all these improvements, smartphone cameras are still missing some of the most important features which still give simple point and shoot and compact cameras, let alone higher end DSLRs, an edge. We’re of course talking about optical zoom capabilities and variable focal lengths.

While Samsung’s Galaxy Zoom camera/smartphone offers something for photography enthusiasts, the design doesn’t really lend itself to the increasingly slim form factors that we demand from our smartphones. Conventional autofocus and zoom mechanisms are not appropriate for miniaturized digital cameras due to the bulky size of such mechanisms. If smartphones are to offer consumers ever more compelling photography experiences, we’re in need of a new technological breakthrough.

samsung galaxy s4 zoom aa design lens out

The Galaxy S4 Zoom marks a good starting point, but smartphones really require smaller camera form factors.

Various patents and companies have sprung up offering small form factor optical technologies which could offer improved camera functionality while matching the small design requirements of portable electronics. Breakthroughs making use of new microelectromechanical system and high-precision manufacturing processes could bring optical zoom functionality to new smartphones in the not too distant future.

How such technologies might work

Mems Cam

As you might have expected, Google is one of the companies at the forefront of MEMS-based zoom lens development, the company filed a patent for this technology back in 2012. You may have noticed the term MEMS before when looking at a few new emerging technologies, such as a new production technique for mobile displays. MEMS stands for microelectromechanical system, and can probably best be describe as microscopic mechanical machines.

The technology is already used in some camera modules to help with auto-focus, and a similar design principle applies to the development of MEMS optical zoom modules. Small mechanical actuators, a type of motor, are used to adjust the focal point of a lens. Here’s where we need a little science. The Google patent mentions an Alvarez Lens, a lens configuration which consists of two plates with varying powers (thickness) and levels of refraction.

alvarez lens

Alvarez Lenses are just one of the ways that small form factor magnification can be accomplished.

Moving the plates into different positions alters the total output power through the lens, either magnifying or de-magnifying the light that passes through it. While it’s a little complicated, essentially all you need to know is that it’s a method for creating a changing level of magnification/focus without having to change out the lens.

The next step is where MEMS comes in, as the small motors are needed to shift the parts of the lens and adjust the magnification level. To meet the low power and small size requirements of portable electronics, piezoelectric motors fit the bill nicely. The image from the Google patent below helps to demonstrate how this all fits together.

MEMS Alvarez Lens Patent

A design for a MEMS controlled Alvarez Lens optical focus module.

The biggest benefit is obviously that small mobile devices, such as smartphones, could benefit from optical zoom properties rather than having to rely on digital, resulting in no loss of quality while zooming in. There are certain limitations with this sort of design; there’s only so much magnification that you can achieve with small lenses, and designs will be stuck within a certain zoom range. Lenses also can’t be replaced or change for different modules, but that’s a small price to pay for a small form factor design.

Google’s design isn’t the only way that small form factor optical zoom modules could be built. Designs using flexible mirrors to perform the magnification are also being trialled, where the angle of the mirrors and focus of the lenses can be controlled by tiny motors. Wavelens is even working on a design that uses flexible membranes to dynamically alter the shape and focus of a lens using optical oils and MEMS actuators, which could scale down to less than 0.4mm in height.

MEMS Mirror and Oil designs

Top: example of flexible mirror based magnification. Bottom: design for a flexible oil filled lens controlled by MEMS activators

Focus Modules for OEMs

On the practical side of things, technically most, if not all, of these technologies will work with the wide range of existing OEM mobile image sensors. The efforts that HTC, Samsung, Sony, etc have all put into improving their own image sensors over the past few years won’t be wasted if they want to go down the optical zoom route, as focus and magnification is controlled by the lens module.

M3-F focus module

For example, Newscale Technologies already has its own 3.3 volt M3-F module (picture above) which is compatible with a range of image sensors and lens sizes and can be mounted onto another developers image sensor PCB. It’s also relatively suitable for smartphones, the module is sized at just 20 x 22 x 16 mm, which shouldn’t extrude from the back of a handset too far.

Although no handsets are set to make use of small optical zoom modules in the immediate future, the upcoming Samsung Galaxy K camera appears to be sticking with a more traditional compact camera design, and this is a technology that you can expect to hear more about over the coming years. Smartphone camera technology just keeps on getting better, it looks like it won’t be too long until the lines between smartphones and point and shoot cameras are completely blurred.

Excited?

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