Industrial Lenses · machine vision

Whats all the buzz about Liquid Tunable Lenses?

The technology is based on the principle of a shape-changing lens.  Consisting of a container filled with optical fluid and then sealed off with an elastic polymer membrane.  When an electromagnetic actuator is used to exert pressure on the container holding the fluid, a deflection of the lens occurs.  The resulting effect is the focal length of the lens is then controlled by the current flowing through the coil of the actuator.  The relationship between the current and the optical power, which in the inverse of focal length, is linear.

Tunable lenses are designed to deflect in a positive direction, which means that the actuator pushes towards the membrane.  In early development, to achieve negative optical power, a plano-concave offset lens was added.  Today’s tunable lenses now have the actuator bonded to the membrane and is able to pull the membrane away from the container with negative currents, which result in a concave lens shape.

The membrane thickness influences the tuning range of the lens, thinner membranes, achieve a larger range of optical power due to the reduced restoring force.  The refractive power of the lens can be changed by using different optical fluids with different indexes of of refraction.

For machine vision applications the benefits of using liquid tunable lenses are:

  • Greater working distance
  • Faster responseFocus Tunable Lenses
  • Reduced lighting requirements
  • Easy to install and use

Optotune, based in Switzerland, recommends using a tunable lens in 3 configurations:

  • Front- Lens, mounted on filter thread of a fixed focus lens you can achieve working distances from infinity to 100mm. This is the most versatile configuration.
  • Back-Lens configuration – the tunable now lens acts as a distance ring when placed between the caemra and a fixed focus lens, providing an easy mechanical solution.  This configuration will provide the best quality for short working distances.
  • High magnification or Telecentric  – here the tunable lens is placed between the tube lens and the zoom lens and is best for high magnification applications.  This configuration works best with infinity corrected lenses and achieves up to 100x magnification.

Excellent applications for a front lens configuration is Bar Code reading, Robotic Vision, package sorting and bottle inspection. Back lens configuration is an excellent choice for C-mount macro imaging applications and works with lenses at a focal length >=35mm.  Other applications for back lens configuration is Electronic inspection, laser processing, contact lens inspection and diamond inspection.  High magnification/telecentric applications benefit from a tunable lens by increasing the Z-range and optimizing  a telecentric lens for large format imaging.  Recommended applications for this use of a tunable lens is in, camera phone lens inspection, IC inspection, LCD & PCB inspection and particle counting in liquids.

This is a high level over view of the technology and where it may best be applied.  For more information on tunable lenses, or to discuss your application please give us a call at 813-984-0125 or email [email protected]  You can also explore tunable lenses on our website at, Optotune lenses at PyramidImaging.com.  Content courtesy of Optotune.

 

 

 

 

 

 

Cameras

5 Reasons You Should Choose a 10 GigE Camera for your Machine Vision Application.

There are many types of Ethernet cameras available for machine vision applications. This is a brief introduction to Ethernet and why 10GigE cameras are attractive. Continue reading “5 Reasons You Should Choose a 10 GigE Camera for your Machine Vision Application.”

Cameras

What is the Best Machine Vision Camera for my Application?

How to select the right camera for your machine vision application?  I would like to present a brief description of the basic procedures that my company, Pyramid Imaging, uses when asked by our customers to determine the best camera for their application.  We’ve been doing this type of work for decades and have developed a simplified but reliable way to narrow down the broad array of possible cameras to a small group of possible candidates.

But, let’s talk about some basics.  We consider a machine vision camera as a camera that will be used to obtain images for an automated process.  We need a camera that has the right number of features that will allow us to control it properly and obtain the images that we require.

First and foremost is to understand the application’s goals.  Are we looking at an Inspection process looking at labels and barcodes, are we requiring Metrology to be done; that is, making accurate measurements on an item?  Maybe we are examining high speed events or do we just need “pretty pictures” for presentation purposes?

Application Goals

Once we truly understand the goal for using a machine vision camera we need to now list all of the application constraints.   We are now looking for the sweet spot in the constraint analysis in which the best camera will satisfy all the requirements.

Application constraints

There are literally thousands of cameras to down select to the one that will be best for your machine vision application.  The broad categories for these cameras include cameras that are:

  • Line Scan – 16K Linear array
  • Area Array – 80 MP and higher
  • High Speed – hundreds of thousands of frames per second
  • Analog (RS-170), FireWire, USB 3, GigE, Camera Link (CL) , Camera Link HS, CoaXpress

These cameras area all about bandwidth and cable length.  Remember that high resolution and high speed cameras need high bandwidth requirements!

You also need to know what lens mount the camera should possess.  These include:

M12, CS, C, F, M42, M75 Lens Mounts.

These are listed in order of increasing aperture. Remember that the bigger the sensor the larger the camera opening needs to be for a lens with a larger aperture.  Also, note that for a line scan camera using a linear array sensor the sensor’s length would be used to determine the largest image circle needed from a lens.  For an area array camera you would use the diagonal length of the imager.

There are also various features that might be required in a camera.  Features such as:

  • Selectable Regions of interest(ROI)
  • FPGAs
  • On camera memory
  • Many others

Here is a type of decision tree that can be considered when trying to select the best machine vision camera:

decision tree for camera

There are many factors to consider when trying to select the appropriate and best machine vision camera for your application.  First and foremost you need to analyze and reanalyze the goals for the machine vision application.  The next vital consideration is to use the best lighting and illumination to highlight the objects of interest.  You want to create as much contrast as possible between what you  want to see and try to make everything else disappear.

So, a quick set of steps for selecting the right camera would be to:

  1. Calculate Resolution- smallest detail in the field of view.
  2. Calculate the object or camera speed- determine best exposure time and frame rate to “freeze” the image.
  3. Encoder or speed sensor ?  If yes prefer line scan !
  4. Distance from computer or display ?  Resolution, Frame rate, Distance dictates data bandwidth , video protocol and cables.
  5. Time to record ?  Dictates amount of RAM and/or RAID storage.
  6. SWAP and other constraints ?  Prioritize
  7. Narrow down and sort camera list on priorities- features, cost, lead time, technical support, viability of manufacturer, etc.

Pyramid Imaging has been providing assistance to customers for decades on selecting the right cameras and other machine vision components.  Go here to see a small example of some of the projects in which we’ve been involved.

Pyramid Imaging  provides this very convenient tool that you can use to  down select cameras based upon certain specifications.  Just go to the camera selector and click on the specifications desired.

We’d be happy to provide you with our free assistance should you like to discuss your application with our experts.  Just Contact Us.