Optics for LED is nothing new and optics for channel letter modules (CLM) has advanced at a fairly fast rate. However with all things new, there is always more to the story than meets the eye, the budget and the actual application need.
First let’s talk about the optic or lens or light-enhancing cover. When optics first appeared for CLM in the not-too-distant past a light-enhancing cover was placed over a standard chip. This was akin to taking 1 gallon of “light” and putting it into a 2 gallon container … same light is the same light, kind of like a pound of feathers vs. a pound of lead—they both weigh the same but they take up totally different spaces. In other words, just adding an optic—while it did allow for more light coverage—takes the same “gallon of light” and spreads it over a larger area, thus more coverage but less illumination overall. This low-tech principle is still available today and the burden of what is right for your needs unfortunately is on your shoulders to separate the good guys from the not-so-good guys.
CLM Optic Considerations
The main advantage of considering an optic CLM is first it should lower your BOM (Bill of Materials), and second it should provide more “chip” illumination to compensate for fewer CLM and a wider beam/light spread over a greater area. On the other hand, a high brightness (HB) chip set is needed to make this simple principle work at its fullest, all things equal.
Think of your car’s headlights: typically a mirror type reflector behind the bulb gathers the light and spreads if over a determined area in front of your car. However, when you need more illumination and hit the “high beam” button, the reflector is not changing, there is more power being driven to the filament/bulb. In simple terms, for an optic-enhanced LED to properly work with the mentioned advantages you have two choices; overdrive the LED (typically not a good solution for longevity) or use a premium HB-type chip(s) with higher lumen output. Now we are getting somewhere.
While optic enhanced CLM are now mainstream it is important to compare standard 120-degree beams vs. optics. A very easy and factual example that was on display at a trade show showed two brand names of CLM installed in a single channel letter—an “H.” One side of the letter was illuminated with a double row of standard 120-degree beam CLMs in a 10” stroke, and on the other side of the “H” was a HB 160-degree sign row of optic CLM. The optic CLM needed seven modules, and the double row of standard CLM required 13 modules. So the unit price of the non-optic vs. the optic gave the unit price favor to the non-optic CLM. Yet when the cost of 13 vs. seven modules was factored in, the optic offered a lower overall job cost, less labor to install and less liability after the sale! As you always hear from me—buyer beware!
Additionally, with the advent of optics, newer dual-beam solutions are offering real advantages by directing the light beam in two different directions instead of providing a simple conical beam. This format offers even more BOM savings, especially when used as designed and directed. These dual beam optics are great for narrow stoke letters where you typically have to increase the CLM count due to the narrow space and to eliminate hot spots; however, with the dual beam you can normally get away with two small-footprint CLM per foot where up to five might have been needed with a 120-degree CLM.
Thus optics serve a real purpose when designed, manufactured and engineered correctly. On the other hand, good old 120-degree beam CLM do work fine, so do not fret if you have a large inventory of them left over or if you prefer them. Like all technology, if it serves your needs and purpose then go for it!
Let’s talk about power on several fronts. HB LEDs provide a real advantage. Typically, if the “HB package”—which includes the chip (LED), PCB and electronics wire and housing—is designed properly all should be fine. On the other hand, the easiest way to get increased lumen/brightness output is to increase the mA voltage to the p/n junction. However, if the package is not designed for the increased voltage, the requisite heat gain can cause premature failure. Understand, this failure might be years out, but in this case it will fail sooner rather than later. It begs the question: “How do you want your customers to remember you?”
Watts per CLM are a direct result of the package components, in total. To understand this simply, watts while measured as consumption is directly related to brightness. Thus, a low watts per foot (WPF) will equate to less lumens/brightness per CLM and potentially the overall impact. More and more sign shops seem to be demanding maximum CLM per power supply, even at the expense of brightness. While this seems to be driven to offer the absolute lowest costs and may be aiding by our economy in general, this is not always the best solution.
As an example if the average CLM per average job is 37 feet and it only requires one 60w power supply and does not increase the need for more power in this example, then it seems you would want to go with the best brightness option you could offer.
In my estimation I see far too much emphasis on the absolute lowest material costs and a number of these types of sales will ultimately come back to cost you in the long run. Signage is still driven by impact and brightness and while everyone wants the best price, the best price is not always the best solution and this can come into to play even more when considering optics because of the HB chip factor.
One more consideration in this market is your vendor’s warranty, and while most all LED products today in the sign industry offer a five-year warranty, it is not the cost to warranty the replacement LED that is expensive—it is the service call, and ultimately your company’s reputation, if you are in it for the long haul.
In closing, these comments are very general and provide an overview of optics and related power considerations. It is my belief that we should always offer the best overall solution first and work backwards if the customer demands it, but never cut the prospect short without justification.