Category: Tutorial

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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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How does a 3CCD camera improve color accuracy and spatial resolution versus standard Bayer color cameras?

In applications where high color accuracy and spatial resolution are required, there are distinct advantages of 3-CCD digital cameras versus Bayer mosaic color alternatives.  JAI cameras provide 3-CCD camera solutions to provide high color fidelity in various resolutions.





Models available (Click on model for specs)


Model #      Resolution          Interface

AT-140CL   1392 x 1040          Camera link
AT-140GE   1392 x 1040         GigE
AT-200CL    1625 x 1236         Camera link
AT-200GE   1625 x 1236         GigE
CV-M9CL     1039 x 744          Camera link
CV-M9GE     1039 x 744         GigE  

Contact us for a quote on 3-CCD cameras!

All 3-CCD digital cameras use dichroic prism optics to split incoming light into three distinct color channels for precise RGB values with full spatial resolution.

The diagram above shows the incoming light path being diverted to separate image sensors in turn having a RGB value co-site sampled.




Color Fidelity

Bayer mosaic color cameras use a pattern of color filters and an interpolation process to estimate the approximate RGB value of a give pixel. With a 3-CCD camera, a specific R, G and B value is captured for each pixel. This inherently produces higher color precision in the 3-CCD output.

The spectral curves resulting from the hard dichroic prism coating are much steeper than the curves from the soft polymer dyes used in Bayer filters. This enables the 3-CCD cameras to produce exceptional accurate color data without the uncertainty that comes with the overlap regions (Area in grey below in the illustration )



High Dynamic Range
In addition to reducing color precision, the overlap in the color filter response also results in part of each pixel’s well capacity filling with photons resulting from the cross-talk, thus decreasing the available well capacity. Precision responses from the dichroic coating enable each channel to efficiently use the full well capacity of the pixel, allowing the maximum possible dynamic range.

Color Space calibration
JAI’s 3-CCD digital cameras include a sophisticated linear color matrix circuit which enables color
matching between camera data and calibrated printers, monitors and other devices. Built in presets are provided to output the color information in the proper format for the sRGB or Adobe RGB industrial standard color space.  


The end Result
The two images below compare results from a 5-megapixel Bayer color camera (left) with the 2- megapixel JAI AT-200 camera (right). Despite having 2.5X the resolution, the 5 megapixel cameras soft polymer dye color filters and the interpolation process result in significant color contamination, less differentiation between similar colors, and reduced sharpness of the image.  


Additional images for comparison are below to demonstrate the fidelity of a 3-CCD camera vs Bayer cameras


Click on the video below now for a full presentation on detailing how 3-CCD cameras improve color accuracy

Need to discuss how a 3-CCD color camera will benefit your application?  1st Vision’s sales engineers all have 25+ years of experience in industrial imaging and can review this in detail. 

JAI also makes 2-CCD, 3-CMOS and 4-CCD line scan cameras. Click here now for more information (see multi-sensor tab)

Need to understand more about Bayer color cameras?  Download this white paper now
 Please do not hesitate to Contact us!  1st Vision can provide a complete solution including cameras, lenses, lighting and cables.  


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

Follow us on Social Media!

    https://www.facebook.com/pages/1st-Vision/944658058935262?fref=ts