An Australian study has shown that adding a thin supercapacitor to the LED flash in camera phones can provide sufficient light energy for high-resolution pictures in low light conditions without compromising slimline design.
Sydney-based CAP-XX compared camera-phone flash solutions for their ability to provide the light energy that camera phones of 2-megapixels or more need to take digital still-camera quality pictures in low light. Ten to fifteen lux seconds (lux sec) of light energy is said to be ideal for high-resolution pictures.
High-current LEDs need up to 400 per cent more power than a phone battery can provide to achieve full light intensity. CAP-XX claims its BriteFlash LED flash power architecture delivers the pulse power of more than 1A needed to drive high-current LEDs. The phone battery is only needed to recharge the supercapacitor for two seconds between flashes.
The study compared camera phones with xenon flash tubes driven by electrolytic storage capacitors against a supercapacitor-powered four-LED array at a current of 1A each. The supercapacitor delivers 15 watts of pulse power to the LEDs, compared to a battery which can only deliver 1 – 2 watts
The tests showed that from two metres away, the BriteFlash array was the only case that achieved a light energy above the recommended 10 lux sec for high-resolution pictures. A standard battery-powered LED flash delivered light energy of only 0.43 lux sec.
Supercapacitors are also slimmer that the xenon solution, use a lower voltage and take only two seconds to recharge between flashes. They can also offload peak power demands from the battery to improve talk time, battery life and audio quality.
Xenon, which delivers very high peak light power over a very short flash exposure time, is superior for taking action shots for those who attempt such shots in low-light conditions. However, CAP-XX claims blurring caused by hand-shaking in the BriteFlash approach over its longer exposure time can be corrected with image-processing software.
According to CAP-XX, mobile phones with flashes boosted by supercapacitors are expected to arrive on the market in late 2007 or early 2008.
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