Table of Contents

Advertisement

Document Number: 102-PS242-100-01

Version: 110
Issue Date: June 2014

FLIR Camera Adjustments

LWIR Video Camera
FLIR Commercial Systems
70 Castilian Drive
Goleta, CA 93117
Phone: +1.805.964.9797
www.flir.com

Application Note

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the LWIR and is the answer not in the manual?

Questions and answers

Subscribe to Our Youtube Channel

Summary of Contents for FLIR LWIR

  • Page 1: Flir Camera Adjustments

    FLIR Camera Adjustments LWIR Video Camera Application Note FLIR Commercial Systems 70 Castilian Drive Goleta, CA 93117 Phone: +1.805.964.9797 www.flir.com Document Number: 102-PS242-100-01 Version: 110 Issue Date: June 2014...
  • Page 2: Table Of Contents

    FLIR Camera Adjustments Table of Contents FLIR Camera Adjustments ........................... 1 LWIR Video Camera ............................ 1 Application Note ............................1 Document Number: 102-PS242-100-01 ....................... 1 Document ............................4 Revision History ........................... 4 Scope ............................. 4 Automatic AGC Parameters......................5 Introduction to Histograms ......................6 Linear Histogram ..........................
  • Page 3 FLIR Camera Adjustments Figure 19: Illustration of Active Contrast Enhancement (ACE) ..............17 Figure 20: Illustration of Smart Scene Optimization (SSO) ............... 18 Figure 21: Illustration of ROI ........................19 Figure 22: Illustration of the difference between Plateau Equalization, Information-based, and Information-based Equalization algorithms ....................
  • Page 4: Document

    This document applies to the FLIR Quark, Quark 2, Tau, Tau 2 and Neutrino cameras. These cores can be found in most FLIR Commercial Systems products. The FLIR website will have the newest version of this document as well as offer access to many other supplemental resources: http://www.flir.com/cvs/cores/resources/...
  • Page 5: Automatic Agc Parameters

    FLIR Camera Adjustments 2.0 Automatic AGC Parameters The first thing to understand is that the detector data is directly streamed from the sensor as 14-bit values for each pixel in the array. The analog image is displayed using 8-bit values and almost all commercial displays are 8-bit devices.
  • Page 6: Introduction To Histograms

    Generally speaking, FLIR recommends the plateau equalization algorithm, but there are scenarios where each of the other algorithms may be better suited. The FLIR GUI provides auto presets that can be used to tune AGC to the specific scene.
  • Page 7: Linear Histogram

    FLIR Camera Adjustments has a narrow spike whereas the mug has different temperatures in the handle and above the coffee line. For this reason, the data is more spread in the histogram at point 3. Figure 2: Image of scene 2.2 Linear Histogram...
  • Page 8: Plateau Histogram Equalization

    FLIR Camera Adjustments The linear histogram algorithm performs a linear transformation from 14-bit to 8-bit of the form: 8bit = m * 14bit The slope of the transformation is computed automatically based on the ROI histogram: m = 255 / (14bit_(100 – Tail Rejection)% - 14bit_(Tail Rejection)%), where 14bit_(Tail Rejection)% is the 14-bit value corresponding to the user selectable tail rejection percentage point on the cumulative ROI histogram and 14bit_(100 –...
  • Page 9: Figure 5: Plateau: 150, Itt Mean: 127, Max Gain: 8

    FLIR Camera Adjustments redistribute the data to achieve this goal. This prevents wasted levels of grey on regions that have no scene content and can visually be seen in the histograms by noticing that peaks are much smoother and the data is spread much more evenly.
  • Page 10: Figure 6: Image Transform Table For Linear And Plateau Algorithms

    FLIR Camera Adjustments Low Contrast Histogram Equalized Low Contrast conversion Linear 14 to 8 bit Lots of Contrast Figure 6: Image Transform Table for Linear and Plateau algorithms In many applications, there are objects with different temperatures that all need to have contrast. In this case, the plateau value can be increased from the default setting of 150 to 250 or 300, depending on the content of the scene.
  • Page 11: Figure 7: Plateau: 250, Itt: 110, Max Gain: 8

    FLIR Camera Adjustments It is also important to note that changes in levels of grey are more perceptible to a human observer at lower levels of illumination. This is because a change from 5 to 10 counts is 100% and a change from 245 to 250 is about 2%.
  • Page 12: Figure 9: Low Contrast Scene In 14-Bit Space

    FLIR Camera Adjustments Figure 9: Low contrast scene in 14-bit space. The large spike from the wall is the same value as in initial histogram. The following histogram shows the 8-bit data with the default Max Gain setting of 8. Notice that there is a large amount of unused levels of grey on the left and right of the signal.
  • Page 13: Figure 12: Plateau: 250, Itt: 127, Max Gain: 25

    FLIR Camera Adjustments Figure 13: Low contrast scene: high gain Figure 12: Plateau: 250, ITT: 127, Max Gain: 25 Figure 14: Plateau: 250, ITT: 127, Max Gain: 50 Figure 15: Low Contrast Scene: very high gain The plateau equalization algorithm performs a non-linear transformation from 14-bit to 8-bit based on image histogram.
  • Page 14: Figure 16: Illustration Of Plateau Value

    FLIR Camera Adjustments Plateau value. When plateau value is set high, the algorithm approaches the behavior of classic histogram equalization – gray shades are distributed proportionally to the cumulative histogram, and more gray shades will be devoted to large areas of similar temperature in a given scene. On the other hand, when plateau value is set low, the algorithm behaves more like a linear AGC algorithm –...
  • Page 15: Figure 17: Illustration Of Maximum Gain In A Bland Image

    FLIR Camera Adjustments Maximum Gain. For scenes with high dynamic range (that is, wide 14-bit histogram), the maximum gain parameter has little effect. For a very bland scene, on the other hand, it can significantly affect the contrast of the resulting image. Figure 17 provides an example.
  • Page 16: Figure 18: Illustration Of Itt Midpoint

    FLIR Camera Adjustments ITT Midpoint. The ITT Midpoint can be used to shift the 8-bit histogram darker or brighter. The nominal value is 128. A lower value causes a darker image, as shown in Figure 18. A darker image can help improve the perceived contrast, but it is important to note that more of the displayed image may be railed (8bit value = 0 or 255) by moving the midpoint away from 128.
  • Page 17: Figure 19: Illustration Of Active Contrast Enhancement (Ace)

    0 do the opposite by decreasing contrast for hotter scene content and leaving more of the gray-scale shades to represent the colder scene content. Figure 19 illustrates the effects of ACE. FLIR recommends a conservative setting of 3 for generic use-case scenarios.
  • Page 18: Figure 20: Illustration Of Smart Scene Optimization (Sso)

    14-bit histogram prior to AGC. This feature is useful for excluding outliers and the most extreme portions of the scene that may be of less interest. FLIR recommends tail rejection settings less than 1% to avoid the exclusion of important scene content.
  • Page 19: Figure 21: Illustration Of Roi

    FLIR Camera Adjustments For Tau 2.0, separate ROI are automatically applied for un-zoom, 2X, 4X, and 8X zoom. Coordinates for the ROI are as follows:  Top / Bottom: 0 = center of the display, negative values are above center, positive values are below center, units are in pixels ...
  • Page 20: Information-Based And Information-Based Equalization

    FLIR Camera Adjustments AGC Filter. The AGC filter is an IIR filter used to adjust how quickly the AGC algorithm reacts to a change in scene or parameter value. The filter is of the form n' = n *  + n'-1 * (256-)/256...
  • Page 21: Legacy Agc Modes

    FLIR Camera Adjustments (a) Plateau Equalization (b) Information-based (c) Information-based Equalization Figure 22: Illustration of the difference between Plateau Equalization, Information-based, and Information-based Equalization algorithms Information Threshold. The information threshold parameter defines the difference between neighboring pixels used to determine whether the local area contains “information” or not. Lower thresholds result in...
  • Page 22: Digital Data Enhancement (Dde)

    FLIR Camera Adjustments Manual The “manual” algorithm performs a linear transformation from 14-bit to 8-bit, with slope based solely on a specified contrast value and offset based solely on a specified brightness value as shown below: m = specified contrast / 64 b = 127 –...
  • Page 23: Figure 24: Illustration Of Noise Suppression With Dde

    (b) DDE index = 70 Figure 25: Illustration of Detail Enhancement with DDE Note: The recommended DDE mode is “dynamic”. “Manual” is provided for customers of previous FLIR cores that have familiarly with the manual DDE mode. Rev110 June 2014...
  • Page 24: Lut Palettes And Polarity

    FLIR Camera Adjustments  Manual mode: The following three parameters are user-specified: o DDE Gain: ranges from 0 to 65535 for Tau 2.7 and later releases and represents the magnitude of high-frequency boost  For gain = 0, DDE is disabled ...
  • Page 25: Figure 28: Look-Up Table Options (Without Isotherms)

    FLIR Camera Adjustments The Tau2 and Quark cameras contained the normal imaging LUTs which contain 256 colors or greyscale and map that to the 8-bit AGC data from the cameras. The imaging palettes are shown below. The palettes only affect the analog and BT.656 outputs of the Quark 1, Tau 2.3 and earlier releases. The Quark 2 and Tau 2.4 releases and later have an option for color in the CMOS and LVDS 8-bit data.
  • Page 26: Figure 20: Isotherm Lut Scale Example

    FLIR Camera Adjustments WhiteHotIso Figure 29: Isotherm LUT Scale Example Rev110 June 2014 Page 26 of 28 102-PS242-100-01...
  • Page 27: Ffc Warning Indicator

    FLIR Camera Adjustments Cold WhiteHotIso Cold BlackHotIso Cold FusionIso Cold RainbowIso Cold GlowboIso Cold Cold Cold SepiaIso IronbowWhiteHotIso IronbowBlackHotIso Cold Cold Cold IceFireIso Cold RainbowHCIso MidRangeWHIso MidRangeBHIso Cold RedHotIso Cold GreenHotIso Figure 30: Look-Up Table Options (with Isotherms) 4.0 FFC Warning Indicator The camera displays an on-screen symbol called the Flat Field Imminent Symbol prior to performing an automatic FFC operation.
  • Page 28: Figure 29: Ffc Warning

    2 seconds (60 frames) prior to the FFC operation. The duration of the FFC Imminent Symbol can be set in the FLIR Camera Controller GUI using the FFC Warn Time setting in the Analog Video Tab. Setting the Warn Time to less than 15 frames turns off the warning. When using analytics, this warning might induce false alarms and it is recommended to either disable this feature or create a region to ignore this area.

Table of Contents