Welcome to the Winter 2014 edition of 'Lens Innovation' - a periodic eNewsletter from Resolve Optics Ltd. to keep you informed about the latest technology, applications advances and breaking news in the Photonics industry.

If a particular feature interests you do not hesitate to contact us or follow the link for further information. We welcome your feedback.

Mark Pontin (Managing Director)

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Technology Forum

Six Tips to help you specify a lens for your vision application

To realise the full performance of your machine vision camera or sensor it needs to be matched with the appropriate lens. As a supplier of specialist lenses to machine vision suppliers and systems integrators for over 15 years, Resolve Optics has assembled below some basic hints and tips on lens selection. Should you wish to discuss any of the points below in detail do not hesitate to contact us on +44-1494-777100 or email markpontin@resolveoptics.com

Format / sensor size
Care should be taken with specifying the camera format or sensor size. Many camera manufacturers will class the format of the camera as a standard format such as 1/3” or 2/3” but in reality the active area of the sensor can be larger or smaller. The best way to avoid confusion is to supply a data sheet for the camera or sensor.

Focal length / Field Of Vision (FOV)
You can specify the focal length in millimetres if known but again it is better if you state the object size and distance. The focal length can then be determined by the design to suit the sensor format.

Aperture
How much light do you have? Typically we are asked for the lens to be as fast as possible, by fast we mean large aperture. However what should be considered really is what image quality is required. Dropping the aperture stop by even one stop can simplify the design and improve the image quality by reducing the level of aberrations that have to be corrected by the design. Reducing the aperture also allows for the diameter of the lens to be reduced.

Distortion
Distortion is similar to the aperture in that specifying a lens with very low distortion will result in a more complex design and increased cost. It is not uncommon for distortion to be specified as the same as stated by the manufacturer of an off-the-shelf lens that you may have already tried. The problem with this approach is that quite often the level of distortion in the off-the-shelf lens is actually a lot higher than specified. This will lead you to specify a more expensive custom lens.

Resolution
Typically the resolution of the lens will match the resolution of the sensor it is to be used on. However, take care not to over-specify your lens resolution as you will end up paying for unused resolution.

Mechanical constraints / Space envelope
If your application is space prohibited then make sure you specify the space available for the lens. Depending on the space available the optical designer will use a design approach to suit.

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Product Focus

Custom Lenses for Demanding Vision Applications

Resolve Optics Ltd has considerable experience of developing fixed and zoom lenses for vision applications including parts recognition, precise component placement, automated alignment and placement and automated inspection of manufactured components. Drawing upon our highly experienced team of optical designers and engineers, we are able to design and produce custom lenses optimized for large format sensors that offer greater resolution and large aperture lenses that make maximum use of available light. We are also highly experienced at producing specialist machine vision lenses that provide wide fields of view with little or no distortion, optical designs and coatings that are balanced to give best performance at a desired wavelength or waveband and compact lens designs where the target application is space limited.

For further information please visit www.resolveoptics.com/news/news-98.html or contact Resolve Optics on +44-1494-777100 or sales@resolveoptics.com

High performance thermal imaging lens

The Model 307 is a high performance, 40mm focal length, Infrared (IR) lens designed specifically for thermal imaging applications in the 8 – 14 µm waveband. Manufactured from Germanium, Model 307 lenses come with antireflective coatings that ensure high performance (f2) throughout the IR waveband. Operating from zero to 40°C without refocusing, the fixed focus Model 307 uniquely combines top quality, high throughput, compactness and robustness at an affordable price.

For further information please visit www.resolveoptics.com/ir-lens-307-000.html or contact Resolve Optics on +44-1494-777100 or sales@resolveoptics.com

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ViewPoint

If your Application is subject to thermal variation – should you be considering an athermalised lens ?

You may be surprised at how quickly some lens designs lose focus with even a 20°C change in temperature. If your application is prone to temperature fluctuations, it is important to develop an optical system that is insensitive to an environment’s thermal change and the resulting system defocus. Developing such an athermal design, which is dependent on the Coefficient of Thermal Expansion (CTE) of the materials and the change in index with temperature (dn/dT), is especially critical in the infrared. The dn/dT of most IR materials is orders of magnitude higher than those of visible glasses, creating large changes in the refractive index. Additionally, while optical systems are often designed in air, the housing material is also sensitive to thermal change, and should be addressed when considering an athermalized design.

There are two forms of lens athermalisation, Passive and Active. Passive Athermalisation of a lens assembly is used when refocusing is not available (no moving parts). By comparison Active Athermalisation allows the lens to be electronically or manually refocused.

Passive athermalization is beneficial in optical systems that are isolated from direct human contact or have limited access to power. Systems that are deployed in space, for example, cannot afford to use the limited battery or solar power to energize motors necessary for maintaining focus. Additionally, motors have limited lifetimes, add weight to launch payloads, and cannot be easily serviced once deployed in space. Therefore, it is undesirable to use them unless absolutely necessary. Hazardous environments can be encountered when performing tasks such as nuclear power plant inspection and border patrol surveillance where temperatures reach extremes that are unsafe for constant human exposure. If the optical system can be passively athermalized, then the available power can be used for transmitting video information or increasing operational time instead of activating motors to maintain focus. To achieve passive athermalization, different temperature-compensating techniques can be customized for all types of optical systems. Optical systems that can be athermalized can consist of reflecting components (mirrors), refracting components (lenses), or a combination of both.

Active athermalisation in its simplest form can be manual adjustment of a lens element or group for refocusing . For more complex optics , such as multi-field-of-view , a procedure can be specified for manual (or motorised) adjustment of several lens elements to maintain focus over a range of magnifications and temperatures. Where automatic active athermalisation is required, a method can be employed that uses a combination of electronics and mechanics . One or more temperature sensors located along the body of the optic feed their signals into an algorithm that calculates the required movement of a compensating lens and then initiates the motion. For simplicity, the compensating lens may be that which already provides close-distance focusing , thus requiring only an increase in the range of movement for athermalization . The location of sensors is especially important for infrared optics and should be dependent on the thermal sensitivity variations within the optical system.

To discuss development of an athermalised lens design to suit your application please contact Resolve Optics on +44-1494-777107 or email markpontin@resolveoptics.com

Case Study 1

Space Ready Zoom Lenses

A key aim of the Satellite Servicing Capabilities Office (SSCO) at the NASA Goddard Space Flight Center in Greenbelt, MD, USA has been to investigate human and robotic satellite servicing while developing the technologies necessary to bring in-orbit spacecraft inspection, repair, refueling, component replacement and assembly capabilities to space. Space borne applications present a challenging environment, subject to radiation, where camera lens servicing or replacement is highly undesirable. NASA sought a proven supplier of high performance, radiation tolerant zoom lenses and selected Resolve Optics because of its expertise in the area and willingness to work with them on adapting our 3x and 6x non- browning zoom lens designs to be 'space ready'.

All optical elements within Resolve Optics supplied non browning lens designs are made using cerium oxide doped glass or synthetic silica enabling them to withstand radiation doses of up to 100,000,000 rads and temperatures up to 55°C without discoloration or degradation of performance. These non-browning lenses provide high image resolution and minimum geometric distortion from 400 to 750nm.

For further information on non browning lenses please visit www.resolveoptics.com/non_browning_lenses.htm or contact Resolve Optics on telephone +44-1494-777100 or sales@resolveoptics.com.

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Case Study 2

Deep Sea Observation Camera Lenses

The ultra compact Resolve Optics Z-10 high definition zoom lens is being used by Kongsberg Maritime (Kongsberg, Norway) as a key component of autonomous camera systems being deployed to monitor methane seep and hydrothermal vent sites deep in the Pacific Ocean. All components in the autonomous camera systems, including the connectors, are made of titanium so the unit can be deployed at a depth of up to 3000 meters for up to a year without maintenance. Integrating the Z10 lens into their design has enabled Kongsberg to keep their CAMDS system as small as possible whilst still providing top quality images.

For further information on Z10 HD lenses please visit www.resolveoptics.com/zoom-lens-330-000.html or contact Resolve Optics on telephone +44-1494-777100 or sales@resolveoptics.com.

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Information Guidelines

In this occasional 'How To' feature, the technical team at Resolve Optics provide you with useful instructions, hints and tips to assist you in your daily work. In issue 5 of Lens Innovation we focus upon 'Setting-up a tracking zoom lens on your camera'.

A tracking zoom lens is designed so that once it has been set-up on your camera correctly it will maintain focus throughout the zoom range. To set-up the zoom lens on a camera there are a few simple steps you must follow to achieve this:

1. Mount the lens on the camera and then zoom to the narrow end of the zoom travel (Narrow FOV largest magnification). Focus the image using the lens focus.

2. Zoom to the wide end of the zoom travel (widest FOV smallest magnification) and focus the image using the back register setting provided on the lens.

3. Repeat step 1 & 2 until you can zoom from wide to narrow and back again without losing focus. Your zoom lens is now set to track.

If you refocus the lens at any point it will no longer track but by simple zooming to the narrow again and refocusing the lens will again track. Once you have set the back register on the lens for the camera you will not need to touch this adjustment again. If you take the lens off the camera and fit the lens to a new camera you may need to carry out the full set-up procedure again.

Happy zooming

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Global Optics News

We have trawled the internet to bring to you some topical breaking news items relating to the photonics / imaging industry that we hope you will find of interest. Happy reading !

North American machine vision market posts record 'first half' 2014.

Sales of MV components and systems in North America increased 11% to $1.04bn in six months to June, though growth is expected to flatten in second half.

For further information please visit http://optics.org/news/5/9/8

Global photonics market valued at more than $150billion.

The global photonics market is worth at least $150bn, according to analysis by SPIE, the international society for optics and photonics.

For further information please visit http://optics.org/news/5/9/24

European machine vision sales show strong growth.

The European machine vision (MV) industry is in "an excellent condition", according to the German VDMA’s latest market survey. Published earlier in July.
It states that the MV sector's turnover grew more strongly than initially expected - by almost 10% in 2013 and for 2014 the VDMA expects a further growth spurt of 12%.

For further information please visit http://optics.org/news/5/7/25

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HOT OFF THE PRESS

Resolve Optics invest in a new
exhibition stand display

Resolve Optics has invested in a new modular exhibition stand system that provides the flexibility to exhibit at both small and major events whilst maintaining branding and core messages. The design concept behind the new stand has been to simplify messages such that visitors can more quickly and easily understand how Resolve Optics can assist them in creating and supplying a specialist lens optimised to their application. The new stand will be on first display at VISION 2014 in Stuttgart.

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  VISION 2014... book the dates

Resolve Optics has announced that it will be exhibiting at VISION 2014 in Stuttgart, Germany (4-6th November 2014). Whether you are looking for an optimised custom lens or off-the-shelf optics for your sensor, camera or instrument system we invite you to come and talk with our experienced team of specialists on Stand I 22 / Halle 1.
For further information please click here.