OWL 640 Mini VIS-SWIR camera

I have received my new OWL 640 Mini Vis-SWIR camera with its IR KOWA 1″ 25mm/F1.4 optic. The camera is optimized for the 0.6 to 1.7 micron waveband and was selected because of this SWIR waveband extending into the visible. On the image below, the quantum efficiency (rate of electron conversion per photon received) of the InGaAs (Indium Gallium Arsenide) camera sensor is displayed and spans from the visible spectrum up to the mid-SWIR (where thermal effects due to the heating up of the electronics start to kick in).

Ninox-640-Vis-SWIR-QE-Curve-1024x781

The camera is small and could possibly be used in the airborne hyperspectral imaging tests that we will do later in this project. The sensor resolution is 640 x 512 (VGA) and the pixel dimension is 15 microns.

raptor photonics

The Camera Link connection directly interfaces into an PCI-e board in the PC. I will not be using the camera with this setup because I want run it either from a laptop or from a Raspberry pi 4. As a result, I will be using a CAMPORT Euresys CL2USB3 (see image below) to control it from the USB3 port.

8114_CamPortCL2USB3_2

The control interface will be developed in Python, and the camera functions such as exposure time, camera gain, binning etc… will be accessed via the serial port of the camera.

Here is a first Infra-red picture of me.

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On the IR picture below, I am holding a glass of water (hum… yes it is) in front of my eyes. Due to the water absorption, at a wavelength band centered on 1450nm, the glass appears to be opaque!

We are used to imaging in the visible where the glass and the water are totally transparent. The spectrograph, which has been described in the previous post, will look at imaging and quantifying the water absorption in the vicinity of this absorption band to be able to extract the moisture content.

me4

Cheers!

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Collaboration with Newcastle University – training day on 2 Headwall hyperspectral sensors at Nafferton Farm

On the 27th and 28th of June, I was at Newcastle University’s Nafferton Farm in Northumberland where 2 Headwall hyperspectral sensors (VNIR and SWIR) were installed and tested for the first time.

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The 2 sensors are a :

  • Micro-Hyperspec VNIR e-serie (1600 pixels in the spatial dimension)  and a
  • Micro-Hyperspec SWIR 384 equipped with a Stirling cooled MCT (384 pixels in the spatial dimension).

They will be soon used to measure the development and phenotype of potatoes. Their large spectral bands and versatility will allow Newcastle to use them on a wide range of experimental activities, either in a laboratory or airborne.

 

Dr Ankush Prashar, the Newcastle University scientific lead, is keen on applying this technology to analyse 300 species of potatoes which are currently cultivated both organically or conventionally at the farm.

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These amazing sensors will be a great tool for comparison of optical performances with the Durham’s prototype currently being built at the UK Remote Sensing Technology Centre in NetPark.

The team is composed of Chris Holder from Durham University – specialised in deep learning (from left to right), Dr Ankush Prashar from Newcastle University – Lecturer in Crop Science, myself, Isaac Gilbert from Analytik Ltd, Francesco Beccari from Headwall, Pigeon from Newcastle University – future PhD student working on the project, and Dr Hiran Vegad from Analytik Ltd.

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This is the start of a productive collaboration between Newcastle and Durham! Please keep following the blog for updates!

Machining and Assembly

We now have completed the machining of a prototype in aluminium. The primary & tertiary mirrors have been diamond turned as one single surface on a Moore Nanotech 250 machine, and the M2 freeform grating has been ruled on the 4 axis Nanotech 350 FG.

The resulting grating looks very nice :

M2 convex grating

When looking at the reflected light, the image through the grating appears multiple, corresponding to the different diffraction order.

The 10 micron period of the grating’s line have a nice triangular profile, to maximize the throughput into the first diffraction order :

blazed grating

The 3 mirrors have been assembled on the breadboard, with the gold coated prismatic folding mirror and the adjustable slit. This slit will allow to adjust and optimize the spectral resolution while maximizing the system’s throughput.

MAIT system 2

MAIT system

The system has then been tested with a white light from an halogen bulb. Looking at the different orders, we note a pretty good match of the spectral lines position and order of appearance with the predicted ones computed on Zemax.

first spectrum

The next stage will be to image the first spectrum on the InGaAs sensor of the Raptor Photonics OWL 640 Mini VIS-SWIR !