What an iPhone Lidar Can Show About the Speed of Light

The distance the ball traveled to the wall and back is calculated using the time of flight for the ball. You get the distance from my hand to the wall if you divide it by 2.

The BallDAR method makes it easy to measure the time and throw a ball. lidar uses light instead of a ball and is essentially the same idea. The "li" part of lidar.

It's possible to make a lidar with a flashlight or a laser. Start a stopwatch if you aim your laser at something. The light hits the wall and then reflects back. The stopwatch should be stopped as soon as you see the laser spot. The distance can be calculated using the speed of light.

It's a practical issue that light travels fast. The speed is 10 meters per second. It takes over 670 million miles per hour. If you measure a distance of 10 meters, the flight time would be close to zero.

If you want lidar to work, you need a fast stopwatch. Galileo tried to figure out the speed of light with this experiment. Even though he did not have a nice stopwatch or lasers, he still tried. He was unable to actually get a measurement.

The majority of lidar uses a single laser with a detector. A computer can measure the time it takes to get a signal back from the device. It's easy to calculate the distance the light traveled.

Only one distance is measured. These 3D lidar surface images show the shapes of objects, but it isn't enough. More data is needed in order to get that.

You can get a distance and bearing if you know where the laser is pointing. You can use a spinning mirror to point the laser in a different direction. You can accumulate a lot of points if you keep doing this. After you have collected lots of them, the points will come together to make a picture of the object you are looking at.

It's too bulky to fit in your phone and using a laser plus a spinning mirror isn't just expensive. How does lidar work on an Apple device? It seems to me that it is magic. I don't know if it's true, but the iPhone uses a grid of dots from the phone to measure distance instead of using a single beam of light. The beams of light are caused by an array of lasers. It's possible to put lidar in a phone because of the number of lasers on one chip.