Friday, August 12, 2016

AutoSens Interview on ISO 26262 Standard

AutoSens conference to be held in Brussels, Belgium on Sept. 20-22, 2016 is about to sold-out with roughly twice as many people registered as the original target.

The conference site publishes an interview on the new ISO 26262 standard with ON Semi's Michael Brading, Technology Strategist, and Kenneth Boorom, Functional Safety Manager at the company’s facility in Corvallis, Oregon. Few quotes:

More and more image sensors are going into vehicles, covering applications from backup-cameras to pedestrian detection and lane keeping. Combining that mix of signals into an integrated single system is a challenge.

One example of a failure mode that we have identified is concerned with the readout mechanism. CMOS sensors are essentially designed around a CMOS memory architecture. The data flows off the chip one row at a time and that means that these can be susceptible to duplication – at first glance, the visual output might seem OK, but the net effect is that an error on multiple rows might obscure an object in the field of view."

View from in-car camera, without any visible defects
in signal.
In this illustration, a row address aliasing fault can lead
to a failure in which the full scene is replaced by
a subset of the scene replicated several times.

"The safety design process, common in industry and also established within ISO 26262, helps us find the problems that otherwise might not be detectable: A defect invisible to the human eye could upset the behavior of an algorithm. And critically, a defect in the behavior of an algorithm could impact the resulting data.

This image down not exhibit unexpected noise artefacts.
The same street scene showing faint bands of noise
caused by ‘bit-flip’ a symptom of a signal timing error.

"Image sensor safety mechanisms that ON Semiconductor provides in support of the ISO 26262 design process can detect some random hardware failures which can result in image quality degradation, such as that shown here, where a ‘bit flip’ in the design signal timing, produces noise in the second image."

1 comment:

  1. My comments:

    - bit flipping is a problem if you deserialize the HiSpi / Mipi signals. FPGA timing for example is critical, you have jitter and damping. And with higher temperature you have timing violations. We see on very hot cameras these effects. To prevent, you have a CRC and an extra clock or sync channel. Also embedded data.

    - The image with a faulty vertical address coding in the sensor will not be possible. Why? Typically with the automotive AR0134/AR0135 sensors and 99% of all the others, you have a destructive readout. You can't readout the same image areas twice. That would be a nice feature, because then you can average identical images by multiple readout and drop the noise by math.


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