Matrix LED in classrooms?

This article is written in response to Dr Shelley James - The Light Lady . you can find her original post here.

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Go read that first.

I hear you about changing things up a little for lighting in our schools and let’s just think about this Matrix LED for a moment. None of this is meant to put the idea down, just some thoughts to add to the discussion.

Matrix LED is indeed a fascinating application of the latest technology. It could be applied to put light exactly where you need it, and using colour selectable LED you could mix up any colour or appearance of light that you wanted from several sources. Score one for a new classroom concept.

Next let’s look at price. Car manufacturers sell millions of cars a year and so far, have only just started using this tech. Even so a replacement matrix headlight for a mid-tier brand is over ￡1000. Assuming we could get a reputable manufacturer interested, how many schools would we have to change to get the cost within budget of the average UK school? I’m not being negative here, it’s a real question. Perhaps @Zumtobel or @Signify could take a look?

Now too controls. I’m guessing we need some sort of planned layout to the class, to know where to put which lighting effect. The warm corner could indeed then have warm light, the relaxed corner could have dim light with starlight effect across it. Maybe this is the world of projector-based effects rather than matrix LED, they are similar. This ignores a couple oof problems we need to get around.

Firstly, there is the view. In SEND schools you may want the child to spend time in one space rather than another, say to read rather than relax. Human nature being what it is, if you can see something you’d rather experience, you are more than likely going to go use that space. Our endorphin response is going to reward us and we’re going to go there again. IN practical teaching spaces it may be better to have separate rooms so you can control access to specific need, student, or time.

Secondly there is reflection. Big rooms have lots of diffuse reflective surfaces. This means that whilst sitting in the dim and warm corner may dose you with less light and more red/less blue, there is the fact that the eye may well be looking out towards the focus zone and seeing brighter, bluer light reflected directly into the eye. A simple solution here is to zone the room with furniture as well as light. That raises the question, if you are going to zone the room, then why not light it with different performing and aesthetic luminaires too?

Let us assume for a moment that we have a standard classroom now lit with matrix LED. We could imagine a small number of powerful light sources, spaced over the ceiling to allow light to be placed in all zones. Or we could imagine a larger number of lower output fittings doing the same. In either case we need to project light from an LED source through a lens/matrix solution into a point in the room. That means that at most points in the room you could sit and look towards a light source that is lighting you, whether above you or off in the distance.

Research suggests that our experience of glare with LED is not well related to our current glare metrics. CIE 232?(International Committee on Illumination, 2019) suggested we underestimate glare based on a few factors (pattern, non-uniformity, luminance, photometry, and colour). A small number of large sources would impact pattern, luminance, non-uniformity, but might allow use to be closer to the point source photometry we use. We will leave colour as the system is supposed t allow us to control the spectrum we output as a positive decision. A larger number of smaller matric LED also impacts pattern, non-uniformity, lowers luminance relative to a small number of large sources and sits as several point sources for photometry.

The issue here is the pattern, non-uniformity, and photometry. LED glare increases with the spacing of LED, the pattern, and the luminance of the source. By using effectively point sources of luminance we might be making a significant glare problem for SEND students and others. The photometry is one the whole industry needs to get over in our way of measuring luminaires. It’s great for software modelling, but it neither it nor the software predicts what we experience. The eye can detect individual LED a few millimetres apart as separate light sources. Current photometry does not allow for this. If you imagine the eye as a multi-million-pixel camera with most of those pixels concentrated in the centre of the sensor, then you can relate why the eye might suffer glare from a multi-LED matrix light source where the luminous intensity is changing constantly.

However, matrix LED could help us around this. Using face tracking technology, you could measure where the students’ eyes are and restrict all light sources from lighting their eye. This at first glance seems a good move. We light the class, but never light directly into the eye. Now I can see that being a groundbreaking solution. There are a few concerns though. To do this for one person is viable, but a room of over ten people becomes a little problematic. Could we only blank out light for the eye or are we in fact restricting light to and area of the class where a face is detected. By doing so we impact the light available. Do we infill that light from a different angle? I guess given some top tech people we could work out how to do that. What about the reflected glare in gloss surfaces, can we predict and restrict that too? I doubt that. We still must get over the face tracking though. Possible, though problematic in some countries. If we could keep the face tracking in the camera and not transmit and recognisable facial features, then we might have a chance here too.

It is an interesting idea, certainly groundbreaking. There’s a few PhD’s needed to get us started.