Category: Tutorial

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10 key things you need to know when selecting a machine vision lens

Improper selection of the correct quality and type of machine vision lens can make your camera selection useless!

In many cases, we see customers attempting to choose a low quality lens for a camera that really needs quality optics to resolve the pixel sizes. Conversely, we also see customers trying to over specify a lens, where you simply need a lens that’s “good enough”


1st Vision has a white paper to help in the lens selection and provide valuable knowledge on various topics to make the best decisions. 

In this comprehensive white paper, you’ll learn the following

  1. Background basics on lenses and what they really do!
  2. The science in some basic formulas to calculate MAG, focal length and angular FOV
  3. What are extension rings used for?
  4. How are lenses rated?  MTF explained
  5. The myth behind “Megapixel” lens ratings
  6. How many pixels do I really need?
  7. What is the ” f# ” of a lens
  8. What does the “lens format” mean?
  9. Comparison of lens types from security to Factory Automation (FA)
  10. How to get some practical advice!

Download the White Paper

1st Vision has many other resources in our educational blogs.  Please find related links to lenses below.  

We are happy to discuss your imaging application in details – Just contact us!

Links:

Advantages of Telescentric lenses in machine vision


Macro lenses vs Extension tubes – What provides the best results?


Image Basics – Calculating lens focal length


Demystifying lens performance specifications
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What are the attributes to consider when selecting a camera and its performance?

We first need to start with some of the basic attributes of the camera such resolution, frame rate, color vs monochrome and interface.  From there, depending on the application, we may look at more advanced attributes such as dynamic range, sensitivity, dark noise and signal to noise ratios.


The basic attributes are easy to understand, but the advanced attributes can be confusing and the data is not easily accessible.  The more advanced information can be found on EMVA 1288 reports from the camera manufacturers when available.  This is a standard which helps provide an apples to apples comparison on key camera sensor attributes.

Allied Vision has done a great job to help understand the attributes by defining the terms and putting them in a graphical format as seen below.  

The following is a graphic to help understand the
terminology along with the definitions  (Courtesy of Allied Vision!)



Definitions are as follows: 

  • Absolute Sensitivity Threshold:  The smallest detectable amount of light.  Expressed in number of electrons.  The point where signal equals temporal dark noise.  This is important to understanding low light performance!
  • Photon Shot Noise:  Signal noise equal to the square root of the incoming photons.  Due to the randomly distributed particle nature of light.
  • Temporal Dark Noise:  Noise when no light is hitting the sensor, also known as read noise.  Due to electric dark current, quantization noise, and other noise sources depending on the specific construction of the sensor and the camera electronics.  
  • Saturation Capacity:  The maximum number of electrons each pixel can hold before reaching non-linear response. 
  • Dynamic Range:  Ratio of maximum signal (saturation capacity) to the minimum signal (temporal dark noise)
  • Signal to Noise at Saturation:  Ratio of the maximum signal (saturation capacity) to noise (photon shot noise).  At saturation, temporal dark noise is insignificant compared to photon shot noise and can be ignored.  

The EMVA 1288 information is available for most cameras upon request.  Contact us to discuss and obtain this information.   

Need help on some of the basics in your camera selection?  We have many helpful blog ports ranging from Calculating camera resolutions to understanding interfaces.  

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White Paper – Learn about High Dynamic Range (HDR) Imaging techniques for Machine Vision

What is High Dynamic Range (HDR) Imaging for machine vision?

First we need to understand what is dynamic range in an image! 

Dynamic range is a term used to describe the difference between the brightest part of a scene and the darkest part of a scene at a given moment in time – essentially the amount of contrast within a single image.  

The four images above provide an example of a high dynamic range scene.  Note how there are details in each exposure that may not be visible in a different exposure (Note that we can see the buildings in the lower right image vs the upper left image). None of the exposures can capture the entire scene without under-saturing (turning dark) or over-saturating (turning white)

In many imaging applications it becomes difficult to discern the dark and bright areas due to lack of dynamic range within the camera.  In turn, cameras using HDR methods must be utilized in order to obtain a high dynamic range image.  

This white paper provides a technical background explaining HDR imaging.   You will learn about various methods used to achieve HDR images including  sequential image fusion, multi-slope pixel integration and dual-sensor image fusion.  Industrial cameras from JAI are identified that support these various methods.  
 
By utilizing the best HDR methods and camera solutions, a HDR image can be achieved and provide detail in the bright and dark areas of an image.  (HDR image below) 
 
“StLouisArchMultiExpEV-4.72” by Kevin McCoy – Own work.  Licenced under CC BY-SA 3.0 via Commons 
://commons.wikimedia.org
 

1stVision has a staff of engineers all with +25 years of experience in the industrial imaging market.  Contact us to help answer your questions and provide a complete solution including cameras, lenses, lighting and cables.  

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White Paper – Key benefits in using LED lighting controllers for machine vision applications

A successful, cost-effective application of a Machine Vision system is often dependent on the interplay of many individual elements, including machine vision lighting.  As much as an Light Emitting Diode (LED) appears to be a basic electronic component, driving it in a fashion suitable for machine vision applications is non-trivial.

LED’s have become the staple in industrial imaging applications in which consistent illumination is key.  In order to achieve constant illumination and synchronization with cameras, controllers from Gardasoft should be utilized.  

Download the full white paper 
here NOW 

  



Why use a LED Lighting Controller?

LED Light Controllers are an essential element of any vision system which needs to optimize illumination intensity and precision trigger sequencing between vision cameras and lights. The following are the main areas where you will benefit from the use of an LED light controller:

Pulse (or strobe) control
Where you need to synchronize the ON time of your light with the camera and target product (controllers are available for nano-second timing resolution)

Overdriving
Where you require increased intensity from your LED light for a short, defined, period of time (with up to 10x over driving capability)

Continuous current power supply (constant light)
Where you require a highly stable constant current supply for constant on LED lighting

Control of multi-lighting schemes
For systems with multiple lighting configurations which require intensity control and high speed synchronization (from single or multiple triggers)

Remote configuration changes
For systems where it is advantageous to have remote setting of lighting system parameters – eg: to facilitate efficient set-up during system commissioning


LED Technology Overview

LEDs are current driven devices.  While LED Lights are specified as either 12V or 24V lights, the actual LEDs are semiconductor devices whose light output is a direct result of the current through the device, not the voltage. 

All LED device manufacturers specify that current control is advised for efficient use.  Typically, LED datasheets will indicate that very small changes in LED voltage results in large changes in the LED current; and large changes in LED current results in large changes in light output intensity. 

As seen in the diagram to the right, small changes in forward voltage (Vf),greatly change current ( If )

Gardasoft LED controllers regulate the current, not the voltage, so that light output is stable, tightly controlled and highly repeatable. 

Controlling the current allows for precise control of the LED light output, with an additional   benefit to users looking to overdrive their lights to increase light output.


There are many advantages of accurate pulsing and over driving LED’s.  However it is also extremely important to ensure LEDs are over driven safely to ensure long life and not catastrophic failure.   

In this white paper, the following topics are covered:

  • An overview of LED technology
  • How to pulse and overdrive LEDs safely using Gardasoft’s patented “SafeSense” technology
  • Three trigger modes from constant, pulses and switched for various applications.
  • How “SafeSense” technology determines the optimum current for consistent LED drive. 
  • Advanced and custom controller functions.  Example – allowing multiple pulses at different intensity levels over various LED channels.  




1st Vision has over 100 years of combined experience in industrial imaging and has a resident lighting expert on hand. 

Contact us for pricing on all Gardasoft controllers and suggestions on your vision and lighting application.  


Ph:  978-474-0044
info@1stvision.com
www.1stvision.com  

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