Electronics — June
By Tim Clark
|In the world of sunlight-viewable LCDs, wits deliver the nits.|
How bright are they? Crozier tells me that only about 1/20th of the light generated by the CCFTs actually makes it to the LCD's surface. That means you need to start with about 20,000 nits in order for the screen to emit 1,000. Crozier doesn't say exactly how many nits he starts with to get 1,600 out of the BriteChart, but he does say that looking at a BriteChart's array of CCFTs without the LCD layers is like staring into the sun.
He also let fall the intriguing fact that BriteChart monitors have the same number of CCFTs as those in the 1,000-nit monitors Computer Dynamics was manufacturing before the joint development of the Laser Plot screens. Engineers achieve the additional 600 nits as a result of manipulating the light within the screen's layers by adding certain films and filters. Crozier would only describe the way these layers affect light in the most general terms: focusing, reshaping, redirecting, guiding. In addition he says that by enabling more light to make it through the LCD, these steps contribute to better off-angle image quality.
Just as enhancing sunlight readability is aimed specifically at the marine market, so are the steps taken to manage the heat generated by added light. Laser Plot's screen is designed to be flush-mounted in a console replete with an array of heat-generating electronics. To keep the unit from getting too hot (at which point liquid crystals can become, disastrously, just liquid), a salt- and water-resistant fan pulls in ambient air through a channel in the back of the unit, passes it directly behind the backlight assembly, and then pushes it through exhaust vents on the sides. Fully submersible--and therefore fully enclosed--units such as those sold by OceanPC and SeaView disperse heat differently. SeaView, for instance, incorporates an injection-molded heat sink at the back of its display. OceanPC uses a combination of heat sinks and internal fans.
Although I knew that heat is an issue with LCDs, I was surprised to learn from Crozier that if you start up CCFTs at too cold a temperature, you accelerate the buildup of deposits on their electrodes, eventually increasing resistance and allowing less current to flow through the tubes. He says that routinely starting the backlights at temperatures colder than 60∞F can reduce their lives (the hours it takes for the light they emit to decay to half-brightness) by thousands of hours. To address this, Computer Dynamics affixed heating strips to the backlight assembly and added a thermostat that keeps the CCFTs off and kicks the heaters on until the unit reaches about 61∞F. Such a feature should be reassuring to northern boaters who can't quite end the season when autumn rolls around.
Laser Plot also took into account boaters who don't like to quit when the sun goes down. Even with brightness being the rage, Laser Plot, having consulted end users, put a lot of effort into dimming capability. Its monitors can be turned down to a mere third of a nit--without flicker and without significant loss of resolution, according to Crozier, so skippers on nighttime watches won't have to toss a towel over the monitor to see what's beyond the bow.
Literally, developers of super-bright LCDs are making visible progress in a demanding technology that offers real benefits to the average boater. When you imagine the environmental challenges most manufacturers of marine equipment face, you picture leaden skies and tossed seas. But these folks have to battle every extreme: fair weather and foul, light and darkness, heat and cold. And like proverbial postmen, they seem to be delivering no matter what.
Digital View (408) 782-7773. Fax: (408) 778-6103. www.seaviewdisplays.com.
This article originally appeared in the May 2003 issue of Power & Motoryacht magazine.