As a owner of a handful of different radar detectors considered high-end, I'd say that you've just discovered one of the common catches to laser detection on even the best laser detectors. Basically is boils down to an impossible situation of trying to balance out sensitivity (ability to detect) and specificity (ability to ignore false alerts). This is the laser equivalent to radar's false alerts.
The sun, being a giant ball of radiation, emits almost every frequency of electromagnetic radiation ranging from radio to microwave, through infrared, into visible light, and on through UV and X-ray/Gamma ray. Some of these (particularly in the X-ray/Gamma ray range) don't really travel that far, but the longer the wavelength, the farther it will travel. So basically you have this giant bright light shining every EM spectrum frequency down on earth, including the frequency of LIDAR guns.
To combat this, laser detector manufacturers (like Escort and Valentine) do a few things. First, they put a piece of colored glass or plastic in front of the laser detector in an attempt to filter out any unwanted frequencies. Of course, this method isn't perfect as there's not really a way to make glass or plastic filter out everything but a particular desired frequency (imagine a pair of sunglasses that could filter out everything but the red-green-blue light frequencies of a stop-light and allow those through at full brightness). So they also have light detecting sensors in the boxes that have a somewhat restricted range of sensitivities. This, too, is imperfect but permits a greater degree of selectivity. Finally, and most simply, they set the boxes up so that they work best mounted perfectly parallel with the ground/pavement. The boxes are designed in such a way that it only permits a narrow angle of light to get in from the front because they place the sensor relatively further back in the box from the plastic filter on the front. We do the same thing with our own eyes when we flip down the sun visors when the sun is low in the sky. It restricts our vertical vision and blocks out the sun.
Just like the sun visor analogy, though, eventually the sun will get low enough in the sky that the visor doesn't extend down far enough to block it out, and if it did, it would block out the view of the road ahead as well (think sunset/sunrise). In the same way, a laser sensor can be blinded by the infrared wavelengths of light hitting it from a sun that is very close to the horizon and trigger a false alert. Since the sun is emitting light at the same frequencies as LIDAR guns, it can trigger a false alert.
If you increase laser sensitivity, you increase the risk of the sun itself setting it off (if low in the sky). If you decrease sensitivity, you risk not picking up "stray" LIDAR signals (which is almost impossible).
I've had this happen with every radar detector I've owned that had laser detection capabilities. Some worse than others. I haven't owned enough variety yet to determine a real pattern as to expensive vs. bargain laser detectors on this issue. I do know from personal experience that the Valentine 1 is very sensitive to this, but it also has the highest-rated laser sensitivity. I wonder if cheap detectors are less likely to false-alert.
On a related note, there are also a few brands of vehicles whose taillights will set off laser detectors with some regularity. Particularly GMC Envoy/Chevy Trailblazer taillights. Supposedly this is due to the red plastic housing used in combination with the particular bulb used. It seems that the red plastic on those taillights doesn't filter out the infrared frequency that is in LIDAR laser light. The Valentine 1 website even comments on this. I've had those taillights set of my Escort Passport 9500i and my Bel RX65Pro as well, though with less regularity.
|
|
Reply With Quote
can laser alert be turned off in all modes except highway?
Originally Posted by upstatedoc
Bookmarks