Reinventing the Lens

Afocal - An afocal lens system neither converges nor diverges incoming light rays. An afocal zoom system changes the magnification of the subject, increasing or decreasing the size of the object projected onto the focusing lens, which is then responsible for focusing the image on the film or sensor.

Circle of confusion - In optics, a circle of confusion,(also known as disk of confusion, circle of indistinctness, blur circle, etc.), is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. In photography, the circle of confusion diameter limit [CoC]is sometimes defined as the largest blur circle that will still be perceived by the human eye as a point when viewed at a distance of 25 cm (or more, depending on the size of the image). A comfortable viewing distance is one at which the angle of view is approximately 60; at a distance of 25 cm, this corresponds to about 30 cm, approximately the diagonal of an 8 x 10-inch image. At this distance, a person with good vision can usually distinguish 5 lines per millimeter, equivalent to a CoC of 0.2 mm. As the size of the final image increases, so does the viewing distance and the CoC also increases. Using the so-called ""Zeiss formula,"" the circle of confusion is sometimes calculated as d/1730 where d is the diagonal measure of the original image (the camera format). For full-frame 35 mm format (24 x 36 mm, 43 mm diagonal) this comes out to be 0.024 mm. A more widely used CoC is d/1500, or 0.029 mm for full-frame 35 mm format, which corresponds to resolving 5 lines per millimeter on a print of 30 cm diagonal.

CMA [Camera Module Assembler] - A firm, such as Flextronics, that sources compatible components- typically a lens (and actuator, if necessary), an image sensor, and image processing chip or image pipeline - from one or more vendors and assembles them into a finished camera module, ready for installation into a capture device such as a DSC, camcorder, mobile phone, or webcam. The firm may act simply as an assembler of pre-sourced parts or may take an active role in the design process, specifying the characteristics of the components, or even design and produce its own components. Typically the process starts with a sensor for which an appropriate lens is chosen or designed and then the image processor is tuned to optimize the results produced by the first two components.

Depth of field - In optics, particularly film and photography, the depth of field (DOF) is the distance in front of and behind the subject that appears to be in focus. There is only one distance at which a subject is precisely in focus, but focus falls off gradually on either side of that distance, and there is a region in which the blurring is imperceptible. This region is greater behind the point of focus than it is in front, because the angle of the light rays change more rapidly; they approach being parallel with increasing distance.

Focus - In optics, focus, also called the focal point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by aberrations of the imaging optics. In the absence of significant aberrations, the smallest possible blur circle is the Airy disc, which is caused by diffraction from the optical system's aperture. Aberrations tend to get worse as the aperture diameter decreases, while the Airy circle is smallest for large apertures. An image is said to be in focus if light from object points is converged enough to be perceived as a point; conversely, it is out of focus if light is not well converged. The border between these conditions is sometimes defined via the circle of confusion criterion.

Hyperfocal distance - The closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp; that is, the focus distance with the maximum depth of field. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp. The criterion for what level of sharpness is considered acceptable is generally specified through the circle of confusion diameter limit; that is, what is the largest acceptable spot size diameter that an infinitesimal point is allowed to spread out to on the imaging medium(film, digital sensor, etc.).

Hysteresis - A property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state; that is, systems whose states depend on their immediate history. Hysteresis is analogous to backlash in mechanical systems which can give rise to position or force errors.

PID [proportional-integral-derivative] controller - A PID controller is a common feedback loop component in industrial control systems. The controller takes a measured value from a process or other apparatus and compares it with a reference value. The difference (or ""error"" signal) is then used to adjust some input to the process in order to bring the process' measured value back to its desired setpoint. Unlike simpler controllers, the PID can adjust process outputs based on the history and rate of change of the error signal, which gives more accurate and stable control. In a PID loop, correction is calculated from the error in three ways: cancel out the current error directly (Proportional), the amount of time the error has continued uncorrected (Integral), and anticipate the future error from the rate of change of the error over time (Derivative). PID controllers do not require advanced mathematics to design and can be easily adjusted (or ""tuned"") to the desired application, unlike more complicated control algorithms based on optimal control theory.

Polymer - A term used to describe large molecules consisting of repeating structural units, or monomers, connected by covalent chemical bonds. The term is derived from the Greek words: polys meaning many, and meros meaning parts. A key feature that distinguishes polymers from other molecules is the repetition of many identical, similar, or complementary molecular subunits in these chains. These subunits, the monomers, are small molecules of low-to-moderate molecular weight, and are linked to each other during a chemical reaction called polymerization.

Power Density - Refers to the amount of power delivered by an energy source, divided by some measure of the source's size or mass. Tiny, lightweight motors or actuators must have a high power density to accomplish their tasks.

SMIA [Standard Mobile Imaging Architecture]- The SMIA standard is an open standard for use by all companies making, buying or specifying miniature integrated camera modules for use in mobile applications. It is a complete standard and it is proposed that a product will be compliant with all portions of the standard. The main requirement is to be able to connect any SMIA-compliant sensor to any SMIA-compliant host system with matching capabilities and get a working system with acceptable performance.

For this series of reports we sent questionnaires to our contacts at all the major technology providers in the broad category of innovative optics and optomechanics (actuators and motion-control mechanisms). For this report, the questionnaires were sent to four leading developers of innovative motion technology who provide focus and zoom capabilities for camera-phone optics: Artificial Muscle Inc., Nanomotion Ltd. (Johnson Electric), New Scale Technologies, Inc., and Varioptic SA. After the completed questionnaires were returned, we conducted follow-up interviews with all four respondents and then sent the company profiles to the respective contacts for final review.

The information in the company profiles as published here was therefore provided and approved by the companies profiled without modification or editorial comment by Future Image. Our analysis and commentary is contained in the Introductory sections and in the final Conclusions & Outlook section.