Polar S720i rainbow screens?

[Weisse Luft]

Yes, I own a Polar S720 and I have noticed this rainbow effect too although it's not bad enough such that it affects the display readout.

It sounds like a bit of a yarn that the manufacturers are spinning. If it is normal, surely it would mention it in the user's manual?

Its completely normal. It only happens in twilight conditions because the light emitted by the sky is slightly polarized, leading to interference patterns much like that of a soap bubble.

LCD's work by cross-polarization to block light reflection through the liquid crystal display. When current is applied to the desired pixel, the liquid crystals are oriented orthogonally to the polarization axis. This blocks the light transmittance. In the S700 series, the backlight reflects off the oriented liquid crystal, illuminating the pixel preferentially.

The interference pattern is a "manufacturing defect" arising from birefrengence (sp?) from the multiple laminations required to make such a display. The "defect" is on the order of a wavelength of visible light, 300-600 nanometers. There is no way to hold the tolerances of the laminations as thermal expansion will cause it to shift.

I admit, its a PITA but it also means I am either starting too early or need to get home.

The cheap and dirty fix is to get an auxillary light to keep it artifically illuminated. There are a few made for this purpose.

 

[hstan]

Its completely normal. It only happens in twilight conditions because the light emitted by the sky is slightly polarized,

-mine happens at noon on a clear sunny day.

LCD's work by cross-polarization to block light reflection through the liquid crystal display. When current is applied to the desired pixel, the liquid crystals are oriented orthogonally to the polarization axis.

-ok. why doesn't this happen with ANY OTHER hr monitors or digital watches or bike computers? I've owned about a dozen other LCD display items, and have NEVER had this problem.

The interference pattern is a "manufacturing defect" arising from birefrengence (sp?) from the multiple laminations required to make such a display. The "defect" is on the order of a wavelength of visible light, 300-600 nanometers. There is no way to hold the tolerances of the laminations as thermal expansion will cause it to shift.

-thank you. This is a defect: probably created by engineers in a lab who thought this molded case would be fine in any kind of sunlight without actually testing it! Unlike Polar in my previous experience (two other polar hrms). I spoke to a Polar rep today who said all the S-series have this 'anomaly'. She refused to admit it is a *defect*.

I like the features and the new transmitter, but the display is really irritating. Especially considering what we paid for these things.

 

[jonsimon]

I have a new Polar S720i, and have been using it on my road bike for a few weeks. The thing works fairly well, although a LOT of interference problems, but that is fairly standard.

My big problem is that it often has this huge rainbow pattern on the LCD screen behind the digits - ie, in the LCD screen itself. On bad days, this can make the screen almost unreadable. Some days it works just fine. The problem only occurs outside - so it somehow or other does depend on or react to light from the sun.

Polar says that this is normal, and is a function of the manufacturing process. I frankly completely disbelieved this - they would not sell a single S720i if that was the case - it is unreadable! And no other LCD screen I have has ever had this effect, so it is not a general LCD problem.

I finally sent the thing back to our local agent here in Australia, and they were truly great. Very professional and super fast. They actually changed the whole LCD screen for me the same day, basically.

But unfortunately, the rainbow effect is still there. It is a totally different pattern this time, but the problem is still there. So I am beginning to think that Polar might be right after all - it is a manufacturing problem.

Does any other S720i user have this problem? I did see a post from another user where he noticed the effect, but as it was only minor, he could tolerate it.

I have used a S710 for a few weeks, and that was perfectly ok - no problems at all.

I get it only when I where polarized sunglasses.