There is a Star Trek-like quality to the equipment in Babs R. Soller’s laboratory. Place your hand on a tiny beam of light, and a machine quickly measures the percentage of red blood cells in your body tissue. It could do the same for pH or oxygen levels, too. But here is the twist: The machine can make these measurements regardless of skin color, thanks to calculations that correct the readings for differences caused by pigmentation. It may seem like a space-age feat to do all this from outside the body without a single pinprick for blood, but that is appropriate — Ms. Soller’s device may someday fly with astronauts.