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.
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.
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.
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 toContact us! 1st Vision can provide a complete solution including cameras, lenses, lighting and cables.
Sony has continued expanding the Pregius image sensor portfolio providing higher resolutions for many camera applications. These camera sensors have excellent sensitivity, signal to noise ratios and dynamic range. Sony has added the new 5MP, 2/3″ IMX250 image sensors to the portfolio which has proliferated into many industrial camera designs. Sensitivity on this camera sensor has even surpassed the popular Pregius 5.86um pixel formats by 1.1X with a smaller pixel allowing the format to be reduced to a 2/3″ format.
Compared to the 5MP, 2/3″ Sony ICX625 CCD image sensor, the new Pregius IMX250, 5MP image sensor boasts ~ 5X sensitivity improvement and dynamic range of 71 db vs 56 db and incredibly low dark noise. We know this information can be baffling so we we have put the two sensors in the ring to battle out the specifications!
From the specification standpoint, the IMX250 knocks out the ICX625 in a few rounds. The key attributes are battled out below.
Specifications
Round 1 – Saturation Capacity and Dynamic Range Saturation capacity (aka well depth) is the amount of charge in electrons a pixel can hold, whereas dynamic range relates to the signal to noise of the temporal dark noise. Comparing saturation capacity and dynamic range, the IMX250 knocks out the ICX625 in one punch. Although the pixel sizes are the same, the new CMOS pixel wells have a saturation capacity of ~ 10.3K electrons compared to 5.9K for the ICX625. This contributes to increased dynamic range allowing images to not saturate quickly, allowing more dark and bright areas to be viewed. In general, the more electrons in the pixel well along with low noise provides better signal to noise ratios. As shown in the graphic, we ideally want a lot of signal electrons vs the noise electrons.
Round 2 – Temporal Dark noise Temporal dark noise also known as read noise is measured in electrons, in which a lower temporal dark noise provides better images. This noise is produced within the sensor electronics and show up in the pixel well as unwanted noisy electrons. The new IMX250 has incredibly low dark noise with only 2.3 electronics compared to the older IMX625 CCD having approximately 9 electrons. The IMX250 clearly wins this round providing better fidelity! Round 3 – Sensitivity & Quantum Efficiency Sensitivity can be measured looking at the number of photons required to have a signal equal to the noise level. A lower number of electronics are better indicating higher sensitivity. Quantum efficiency measures the percentage of photons converted to electronics at a given wavelength. In comparing the sensitivity thresholds, it takes ~ 4 electrons to gain a signal versus 22 comparing the IMX250 vs ICX625 making it much more sensitive. Reviewing the quantum efficiency at 525nm, further supports this with a higher percentage of photons being converted on the new CMOS sensor with 76% vs 57%. Its a knockout in round 3!
.. And the winner is… the Sony IMX250 CMOS sensor! This comparison shows excellent gains in technology with this 5MP sensor! If you are using the ICX625 sensor, the IMX250 is a drop in replacement allowing you to keep the optics, gain better performance and drop the price of your camera substantially!
Several camera manufacturers have the new Sony Pregius IMX250 5MP sensor in their lineup and more on the horizon. Links to the current cameras as follows listed by interface. As a note, the IMX250 is the faster sensor vs its counterpart, the IMX264. Both of these sensors have essentially the same performance, but speed and price are lower with the IMX264. In many cases, you will see both sensors within a camera product line, but the IMX264 sensor will be at a lower price. Cameras in the current lineup are as follows: USB3 IDS UI-3080CP – IMX250 IDS UI-3280CP – IMX264
This is the second of our sensor battles! See our comparison and learn how the Sony IMX174 (and its counterpart the IMX249) compare against a CMOSIS 2MP sensor!
Please do not hesitate toContact us! 1st Vision can provide a complete solution including cameras, lenses, lighting and cables. We are happy to discuss the differences along with pros and cons of the various sensors and cameras. Ph: 978-474-0044 info@1stvision.com www.1stvision.com Follow us on Social Media!
