偏光エリアカメラ Genie Nano M2450 Polarized

Teledyne DALSA • 880 Rue McCaffrey • St-Laurent, Québec, H4T 2C7 • Canada http://www.teledynedalsa.com/Genie-Nano G3-AN0006 Genie Nano-Polarized Demo Application Note Genie Nano: Polarized Sensors Software Demo For Nano models with P/N: G3-GM14-M2450 Overview The first Genie Nano model with a quad-polarizer filter (M2450-Polarized) uses the Sony Pregius 5.1 MP IMX250MZR monochrome sensor. These types of sensor incorporate a nanowire polarizer filter that allows detection of both the angle and amount of polarized light. Polarized filtering can reduce the effects of reflections and glare from multiple directions and reveal otherwise undetectable features in the target scene. This application note describes the implementation of a polarization demo with several different algorithms for polarization imaging. The Genie Nano Polarized software demo is available for download from the Teledyne DALSA ftp server: ftp://ftp.dalsa.com/Private/p_ProductSupport/Genie/Demo/GigeCameraDemo_Polarized.zip Prerequisites The following table lists the recommended Genie Nano firmware and software for this camera model. Genie Nano Firmware Design Software SDK Standard Sapera LT 8.31 or higher Sapera LT SDK (full version), the image acquisition and control SDK for Teledyne DALSA cameras is available for download from the Teledyne DALSA website: http://teledynedalsa.com/imaging/support/downloads/sdks/ If the required version is not available, contact your Teledyne DALSA representative. Sapera LT includes the CamExpert application, which provides a graphical user interface to access camera features for configuration and setup. Doc #: G3-AN0006-V1 May 30, 2018 Page 1

Polarization Filter Theory of Operation Polarization direction is defined as the electrical field direction. Light, with its electrical field oscillating perpendicular to the nanowire grid, passes through the filter while that in the parallel direction is rejected (reflected/absorbed by the nanowire filter). For polarized light, only the portion of the light vector perpendicular to the angle of the nanowire filter grid passes. Wire-Grid Polarizing Filter Filtered Polarized Light Polarized Light Light Component Perpendicular to Filter For example, with a wire-grid polarizer filter at 90⁰ the maximum transmission is for polarized light at an angle of 0⁰. Nanowire Polarizer Filter Polarizer (Filter) Angle Polarizing Angle of Light (blocks light at this angle) (passes through filter) 0⁰ 90⁰ 45⁰ 135⁰ 135⁰ 45⁰ 90⁰ 0⁰ Doc #: G3-AN0006-V1 May 30, 2018 Page 2

The polarizer filter is placed directly on the sensor’s pixel array, beneath the micro lens array. This design, compared to polarizer filters on top of the micro lens array, reduces the possibility of light at a polarized angle being misdirected into an adjacent pixel (crosstalk) and incorrectly detected at the wrong angle. The Genie Nano’s polarizer filter on the camera sensor is a 2x2 pattern, with each pixel having a nanowire polarizer filter with a different angle (90⁰, 45⁰, 135⁰, 0⁰). Doc #: G3-AN0006-V1 May 30, 2018 Page 3

The image output pattern of the monochrome camera is arranged in 2x2 pixel blocks as follows: X X X X ...1 2 3 4 0oY 135 o 0o 135o 1 Y2 45o 90o 45o 90o That is, the first line output is an alternating sequence of pixels 0⁰ , 135⁰; the following line 45⁰ ,90⁰. Given the proportion of light available through these four filters, any angle of polarized light can be calculated. Any given state of polarization can be composed by two linearly polarized waves in perpendicular directions. The state of polarization is determined by the relative ampltitude and difference in phase between the two component waves. Calculations on the 2x2 filter blocks result in a single pixel for each polarizer filter angle, therefore the resulting image is one fourth the original image resolution. For example, with an original image of 2464x2056, the resulting image is 1232x1028 (original buffer width/2 and orignal buffer height/2) for a single polarizing angle. X Resulting Image (1232x1028) Original Image (2486x2056) Y Doc #: G3-AN0006-V1 May 30, 2018 Page 4

Polarization Demo User Interface The demo user interface can display either raw images for the image intensity sum and each of the 4 polarizer filter angles, or when the Processing Enable checkbox is active, the result of the 4 processing algorithms. Raw Polorization Images Processed Polarization Images For display purposes, the demo applies a scale and offset to the processed images. The range of pixel values (minimum to maximum) determines the scaling factor to apply such that all the 8-bits (0-255) of the display are used. Doc #: G3-AN0006-V1 May 30, 2018 Page 5

The bottom-left area of the window groups demo parameters, such as acquisition control, camera pixel format and displays acquisition related statistics including the current exposure time, processing time, frame rate and the maximum frame rate. In addition, a pseudo-color display can also be enabled. View Settings To open the View dialog, click the View button in the demo application window. The View dialog groups various parameters related to the image display in the demo window. For example, to fit the acquisition image to the display area, click the Fit to Window button. If the acquisition pixel depth is greater than 8-bits, the Range slider can be used to select the bit range to display. Doc #: G3-AN0006-V1 May 30, 2018 Page 6

Pseudo Color Display When enabled, images can be displayed using a pseudo-color mapping. The demo uses a text file containing a lookup table (LUT) of RGB values corresponding to 8-bit grayscale values. Doc #: G3-AN0006-V1 May 30, 2018 Page 7

Raw Polarized Images Raw, unprocessed polarized images can be extracted from the sensor for each of the polarizer filter angles (90⁰, 45⁰, 135⁰, 0⁰) and analyzed. For example, the raw image of a computer LCD monitor, at the polarizer filter angle 45⁰, displays a seemingly black image; since this particular LCD is designed with a polarizer filter at this angle, it is effectively blocked. However, by adjusting the contrast and brightness settings (for display purposes only), image details can be revealed. Raw Polarized Image at 45⁰ Contrast/Brightness Enhanced Image Demo Processing of Polarized Image Data Different algorithms can be applied to the polarized images for image processing. The Sapera LT Polarized Sensor Demo implements the following processing algorithms, where I is the pixel intensity and the numeral represents the angle: • Stokes S1: S1 = 0 - I90 • Stokes S2: S2 = I45 - I135 • Angle of Polarization (AoP):

Degree of Linear Polarization (DoLP) The degree of linear polarization is defined as the ratio of the intensity of the polarized part to the total intensity. That is, it is a measure of the what percentage of the total average lightwave signal is polarized, and can be related directly to mateial properties. Angle of Polarization (AoP) Angle of Polarization is the angle of the major axis of the polarization ellipse. This can be related directly to material properties. Sample Images The following images of a computer LCD monitor show the effects of the various processing algorithms. Raw Image Intensity Summation Degree of Linear Polarization Angle of Polarization Stokes S1 Stokes S2 Doc #: G3-AN0006-V1 May 30, 2018 Page 9