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Image sensors technology publications

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Spectral Response of Silicon Sensors
White paper describing the physical properties of silicon and how silicon can see. Large emphasis is made on spectral response first and second order effects.
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From CCDinosaurs to the APS century
Invited Keynote at the 2016 Caeleste workshop in Brussels (part of SPIE Photonics Europe) - about the history of imaging from CCD to CMOS APS devices and a window on the future
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Why you can't use a white (broad spectrum) light source for your spectral measurements
We are sometimes asked to perform fine spectral measurements of the performance of image sensors or cameras, something that our standard EMVA1288 equipment can't do because of its LED based design.

Most labs will use a wide spectrum, usually white, light source and a monochromator to provide the spectral response curves. This approach can lead to incorrect or not precise results. We will explain why and present our approach.
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Defect pixels
Defect pixels are not just dead pixels, there is a variety of behaviors that are considered defects. This paper explains which defects can be encountered.
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Response Curve Programming of HDR Image Sensors based on Discretized Information Transfer and Scene Information
Most of the snapshot HDR (High Dynamic Range) image sensors have a non-linear, programmable, response curve that requires multiple register settings. The
complexity of the settings is such that most algorithms reduce the number of parameters to only two or three and calculate a smooth response curve that approaches a log response. The information available in the final image depends on the compression rate of the response curve and the quantization step of the device. In this early stage proposal, we make use of scene information and discrete information transfer to calculate the response curve shape that maximizes the information in the final image. The image may look different to a human but contains more useful information for machine vision processing. One important field of use of such sensors with programmable dynamic range is automotive on-board machine vision and more specifically autonomous vehicles.
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EMVA1288 publications

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Using the EMVA1288 standard to select an image sensor or camera
Using the EMVA1288 standard to select an image sensor or camera (Paper presented at SPIE Electronic Imaging 2010, see first page of the document for an abstract)
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Implementing and using the EMVA1288 standard
We have measured cameras of various kinds on our test equipment. The test system design and all the measurement sets require to go in the details of the standard and also show us how good it can be but also how difficult it can be.

The purpose of this paper is to give feedback on the standard, based on our experience of implementers and users. We will see that some measurements are easily reproducible and can easily be implemented while others require more research on hardware, software and procedures and also that the results can sometimes have very little meaning. Our conclusion will be that the EMVA1288 standard is good and well suited for the measurement and characterization of image sensors and cameras for image processing applications but that it is hard for a newcomer to understand the produced data and properly use a test equipment.

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Why using variable exposure time in EMVA1288 measurements
Why using variable exposure time instead of variable light intensity in EMVA1288 measurements
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Why using average instead of variance in EMVA1288 dark current measurement
The EMVA1288 standard proposes two methods for dark current measurement. The first method uses the average variation of dark images when exposure time is increased, while the other uses the variation of the variance of the dark images. Why can they give different results?
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How to ensure that your EMVA1288 equipment is compliant
EMVA1288 is currently self-certifying. How can you do this?
Certification procedures will change in version 3.2 and 3.3 of the standard, what do you have to expect?
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Camera design publications

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How to extend the operating temperature of FPGAs
Our high temperature camera for oil and gas wells inspection requires to operate at very high temperatures above the specified operating junction temperature of the FPGAs and with limited cooling possibilities. This article published in the Xilinx XCell journal explains how we have achieved this.
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Camera architectures
During our preliminary project meetings with customers, we are usually asked about the general architecture of a camera, so let's explain this in a short blog post.
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Doppler effect based hyperspectral imaging
There are multiple solutions for hyperspectral imaging, all of them include either grating or filters and therefore lose spatial resolution (2D patterns) or time resolution (1D patterns or line scan or push broom). In this paper, we present a method for hyperspectral imaging that does not require either gratings or multiple filters and that maintains the full 2D resolution of the sensor and arbitrary small wavelength resolution is possible. However, the camera may become heavy.
This paper has been published on April 1st 2017.
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Why Today's Industrial Cameras Require Modern and Complex Electronics
Industrial cameras are getting more complex than ever due to the advances in electronics performance, increased sensor speed and an increase in resolution requirements for higher performance or emerging applications. The time when a camera was simply an image sensor with its output bits packed on a CameraLink bus is now long behind. Today's cameras exhibit high speed computer interfaces and complex on-board real time processing that require state-of-the-art electronic design for board level, FPGA, processor and memory as well as thermal and mechanical know-how.
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Why do you need a specialized partner to develop a custom camera
Many companies have electronic development capabilities and because today's CMOS image sensors are fully digital and easy to use, many of them attempt to develop their own cameras. Even if it is indeed a lot easier today to develop a camera based on a CMOS device than it used to be during the CCD era, there are plenty of pitfalls that explain why cameras are still developed by specialized companies.
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Press releases

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Vision Award 2014 press release
Press release in Industrial Machine Vision Europe (IMVE) about the short listing of Aphesa for the 2014 Vision Award
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Other publications

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Why technical training is important
Why is is so important to technically train your personnel?
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About us

Aphesa develops custom cameras and custom electronics including FPGA code and embedded software. We also provide EMVA1288 test equipment and test services as well as consulting and training in machine vision and imaging technologies. Aphesa works in several markets including industrial, medical, oil&gas and security.