Imaging Basics – Calculating Lens Focal length

In any industrial imaging application, we have the task of selecting several main components to solve the problem at hand.  The first being an industrial camera and second,  a lens to acquire the given image.  In many cases, our working distance of our lens is constrained and may have to mount the camera closer or further from the object plane.  Once set, this defines our working distance (WD) for the lens.  In addition, we have a given field of view (basically the dimension across the image) of the desired object.  


In order to select the correct focal length lens which is denoted in millimeters (i.e 25mm focal length), we need additional information on the camera sensor.  Camera sensors come in various “Image formats”.  The chart below indicates some common formats which relate to the sensor size.  The sensor size can be found on the actual sensor datasheets if not available in a given chart.  


For this exercise, we want to image an object that is 400mm from the front of the lens to the object and desire a field of view of 90mm.  

We have selected a camera with the Sony Pregius CMOS IMX174 sensor.  This uses a 1/1.2″ format which measures 10.67mm x 8mm.  


We have the following known values at this point: 

Field of View (FOV)  =  90mm
Working Distance (WD) = 400mm   
Sensor Size = 10.67mm – We will calculate for a 90mm horizonal FOV, in turn use the horizontal sensor dimension

The basic formula to calculate the lens focal length is as follows: 

FL = (Sensor size * WD) / FOV

Using the values from our application, 

FL = ( 10.67mm * 400mm ) / 90mm 
FL = 47.4mm

Lenses are only available off the shelf in various focal lengths (i.e 25mm, 35mm, 50mm), so this calculate is theoretical and may need an iteration to adjust working distance. Alternatively, if your application can have a slightly smaller or larger FOV, the closest focal length lens to your calculation may be suitable.


1st Vision has made calculating your lens focal length a bit easier!  As in engineering, its good to know the background formulas, but in practicality, like to simplify life with tools

You will find our lens calculator HERE.  Alternatively as select a camera, you will find an icon to the right which will automatically populate the calculator.  Below is a short video showing how to use this resource from the camera pages.  





A few additional considerations when selecting a lens:

  • Lenses have minimum working distances (MOD), so this should be considered when reviewing a lens setup.  MOD’s can be found on the lens page for the given lenses.
  • Lenses need to be paired with the appropriate sensor.  For example, if you have a 1/2″ sensor, you need to ensure you are using a 1/2″ format lens or larger.
  • In selecting a lens, you need to ensure the lens has enough resolution (in lp/mm) to resolve the pixels on your camera.  Be sure to review this data carefully once you ID the desired focal length.  Demystifying lens specifications provides further understanding. 


Related Blogs: 
Demystifying Lens Specifications
Understanding Lens MTF
Calculating Resolution for Machine vision


Contact us to discuss your application and help make a recommendation!  1st Vision can provide a complete solution including lenses, cables and lighting. 

www.1stvision.com  
Ph:  978-474-0044

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Teledyne DALSA Introduces Low-cost, Fast GigE cameras featuring TurboDrive and Sony Pregius sensor

Teledyne DALSA introduces its Genie Nano series of affordable, easy-to-use GigE Vision® cameras. The series combines industry-leading CMOS image sensors, including the Sony Pregius and On Semiconductor’s Python, with a fully optimized camera platform to deliver high frame rates and powerful features in a small, robust body.

The first four models in the Genie Nano series, the M1920, C1920, M1940 and C1940 are built around the Sony® Pregius 2 Megapixel IMX249 and IMX174 CMOS image sensors respectively. Available in monochrome and color with additional resolutions to follow, Genie Nano cameras help ensure high performance and reliability with their unique feature set. Designed for industrial imaging applications with Teledyne DALSA’s patent-pending TurboDrive™ technology, these latest Genies are capable of breakthrough data transfer at 2 or even 3 times the standard GigE Visionrates. The Genie Nano series also takes full advantage of the Sapera™ LT Software Development Kit (SDK) and field proven Trigger-to-Image-Reliability framework for full system-level monitoring, control, and diagnostics from image capture through transfer to host memory.
Key Features: 
  • TurboDrive allows fast frame rates and full image quality
  • Trigger-to-Image-Reliability
  • Small footprint for tight spaces – 44mm x 29mm x 21mm
  • Wide temperature range (-20 to 60c) housing for imaging in harsh environments
  • 2 inputs/2 opto-coupled outputs for easy integration and deployment
  • Light weight – only 46 grams

Video – Introducing Genie Nano:

Full Data Sheets & Manual


Applications
Genie Nano cameras are suitable for a wide range of inspection applications including intelligent traffic systems (ITS), entertainment, medical, food and beverage inspection, and electronics and printed circuit board (PCB) inspection, among many others. 

Resources
Dalsa Camera page features Genie Nano Product information including the full camera portfolio.


Turbo Drive Technology page provides additional resources such as Technology primers and FAQ’s

UPDATE:  Febraury 29, 2016 – See Dalsa’s new video on “Trigger to Image Reliability” below.  A great feature packed into the Nano cameras.  



Contact us to discuss your application and help make a recommendation!  1st Vision can provide a complete solution including lenses, cables and lighting.  

www.1stvision.com  
Ph:  978-474-0044

We also have Genie Nano’s in stock!

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ISVI provides High Speed + High Resolution 25MP @ 72 fps.. That’s fast!

1st Vision is pleased to announce we are now a distributor for ISVI Corp.

ISVI is one of the leaders in designing and manufacturing advanced high speed, high resolution camera technology combining the highest bandwidth interfaces. 


This combination coupled with the latest image sensors provides an unparalleled combination of image quality and high speed.  




Key Features include: 

  • CoaXpress and Camera Link interfaces 
  • High resolution up to 25 Megapixels
  • High Image Quality (Class 1 Sensors used in IC-X29 model cameras providing less pixel defects!)
  • Precise Tap Balance
  • Flat Field Correction  / Defect pixel correction
  • DIN 1.0/2.3 connectors on select models allow the use of commercially available molded-cover CXP cables. 
  • Various lens mount options (F-Mount, M72, M58, M42, LM Lens Mount )

Featured Products at a glance: 


Model  Resolution Frame
Rate (fps)
Interface Sensor
IC-X12S-CXP 12 MP 181 CoaXpress CMOSIS CMV12000
IC-X25/X25S-CL 25 MP 30 Camera Link OnSemi Vita
IC-X25/X25S-CXP 25 MP 53/72  CoaXpress OnSemi Vita
IC-X29/X29S-CL 29 MP 5 fps Camera Link OnSemi KAI-29050



For full ISVI datasheets , click HERE!  

Silicon Software Frame grabbers are recommended for ISVI CoaxPress cameras and support up to CXP 6.  Additionally Silicon Software provides SmartApplets for loading application-related image processing sequences onto their “V” series frame grabbers.  The processing takes place in real-time and relieves the host for other software related processes.  

For full Silicon Software Datasheets click HERE    

Contact us to discuss your application and help make a recommendation!  1st Vision can provide a complete solution including lenses, cables and lighting.  

www.1stvision.com  
Ph:  978-474-0044

Do not forget to follow us on social media!

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Not all Lenses are created equal! MTF comparisons

In our previous blog, Demystifying lens specs,  we discussed the Modulation Transfer Function, also known as MTF, which gives you the performance of light through a medium.  The MTF helps us understand lens characteristics, however it is extremely hard to compare using manufacturer’s data sheets.  In essence, looking at a 25mm / f1.4 lens from vendor A to vendor B may look similar with basic information, but they are not!  Not all lenses are created equal and in turn need extensive data for comparison. 

The problem with comparing lens MTFs.

The problem is that most lens manufacturers DO NOT supply MTF information, or do not supply complete MTFs. Lens manufacturers with high quality optics, such as Schneider Optics, are one of the few that provide a complete set of MTFs vs. transmission.  (See an example on Pg 2 on this datasheet.)  Many will provide basic information in terms of line pairs/mm (lp/mm) measured in the center of the lens, however this is still not enough for a true comparison.  MTF data will vary with aperture (f3), light intensity and distance from the center to edges.  In turn, if you are not comparing “apples to apples”, you cannot draw a conclusion on which is the better lens.

Can I just measure the MTF myself?

The short answer to this is: Not so easily! First off, the MTF of a computer monitor is probably around 30 lp/mm. All the lenses we are discussing in this blog are at least 2x this, if not 3 or 4x it. So the limiting factor is the monitor, and you will not be able to see any differences. If you have a resolution chart, and some software where you can get the actual pixel data and plot it vs. the test pattern, you can get a better idea. However, a fairly rigid test set up with constant lighting, constant exact FOV and other identical parameters is required. This is a very lengthy process and requires special equipment. True optical testing is the correct way to determine and compare MTF.

Bottom Line:  1st Vision has done extensive testing on many lenses and have true comparisons.  We can help you determine which lens is the best for your application!…. Unless you have some nice optical equipment and some time!

 

Contact us to discuss the application and we can help make a recommendation!  1st Vision has 100’s of lenses in stock for same day delivery!


Our lens webpage also highlights the resolution and distortion BUT again does not tell the whole story!

www.1stvision.com  
Ph:  978-474-0044

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