December 22, 2008

Camera autofocus

Back in the day, when they first started trying to develop auto-focus cameras, one of the clever things they tried was using ultrasound. They mounted an ultrasound transducer on the camera, and when the user clicked the button, it fired a sound pulse at the direct center of the field of view, and then measured the bounce time to figure out the range.

There's a really huge flaw in this concept, which rendered it completely useless. Can any of you figure out what it is? (It isn't "flat angled target bounces the sound off to the side." That one's a problem, too, but it's not the one I'm thinking of.)

Posted by: Steven Den Beste in Engineer's Disease at 09:58 PM | Comments (6) | Add Comment
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1 Taking a picture through a glass window doesn't work to well with that system.

Posted by: at December 22, 2008 10:11 PM (Dmikg)

2 That's the one, whoever you are. Um, Pixy? How did he/she/it do that?

Posted by: Steven Den Beste at December 22, 2008 10:18 PM (+rSRq)

3 Wow, that was a really fast answer. *impressed*

Posted by: gaiaswill at December 22, 2008 11:01 PM (gctoU)

4 Ghosts in the blog!  Ghosts in the blog!

Has to be a registered user, I think.  I'll take a look

Posted by: Pixy Misa at December 22, 2008 11:16 PM (PiXy!)

5 I'm a long time lurker who finally registered last week, so I could occasionally join in the fun

Posted by: at December 23, 2008 05:55 AM (Dmikg)

6 They tried again with infrared (and just plain "red"), with the same problem. This continued into the digital era, until they had enough CPU power to analyze the image in real time. SLRs still have dedicated sensors, but the point-and-shoots are getting really good at analyzing pixels. Face-detection works quite well on my pocket Canon.


Posted by: J Greely at December 23, 2008 07:36 AM (2XtN5)

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