Laser Position Sensor

Joe Grand of Grand Idea Studio has released the code and complete design files for his open source Laser Position Sensor (LPS) project. The project is based on the Freescale MC9S08JM8CLC and several Linear Technology LT1491ACS op amps. (Despite the references to Parallax in the LPS project documentation, this device is an open source project that is not commercially produced.)

Joe states:

The Laser Position Sensor (LPS) module is an optical sensor that measures and provides the two-dimensional coordinates of visible red laser light (630-694nm) shined onto its surface. The LPS has a resolution of 0.0001″, an accuracy of 0.001″, and a measurement range of +/-0.2″ (+/-5mm). Applications include positioning and alignment, long-range beam-break/security trip wires, remote device control, data communications, and high-speed photography.

To give some idea of what goes into the design of a project of similar complexity, Joe has chronicled his efforts in designing a separate device, the Laser Range Finder, in this project development diary on the Parallax forum.

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  1. As soon as I saw the Linear Technology parts, my immediate reaction was: “This is going to be expensive.” Sure enough, the BoM adds up to $36 before shipping, and that’s without the $72 sensor. I suppose if you can afford the $72 sensor then spending $6 or $7 each for three op-amp chips is no big deal.

  2. Interesting. I hold a patent on “Method and apparatus for inspecting a workpiece” 6,118,540 which is based on a laser and imager.

  3. I have three patents and I dont know how many disclosures. All three were assigned to Texas Instruments and then to STI. I think one of them belongs to Rudolph Technologies right now. I am trying to find out who holds the others now. The fact that they are in your name does not mean much. When I was at Texas Instruments they gave you a bonus and royalties. When TI sold “us” to Micron and then Micron laid us off, I lost track of all of that.

  4. Hi guys-

    There seems to be some confusion. The project development diary you link here ( is for my Laser Range Finder – a completely different project than the Laser Position Sensor discussed in this post that was released last year. Both are open source, but the LRF is still in-progress (using a CMOS camera and laser diode for optical triangulation) and will be sold by Parallax if I can get it to a point I’m happy with.

    @MichaelZ: Congratulations on the patent. However, using an off-the-shelf optical position sensor for its intended case of measuring 2D position, as I’m doing in the LPS, is not unique and/or novel and certainly wouldn’t violate any patent on its own. We decided to not sell the product because it was too expensive (~$25 for the Hamamatsu sensor in quantity) and we felt it was not really suited for hobbyist applications. A brief discussion about the project can be found here:

    Take care,


    1. @Joe: No worries on my part. I agree that your design doesnt violate the patent but the issue is how it is used. If it was used to measure the surface of an object it might be in violation. My original intent was to measure coplanarity of the balls on BGA packages.

      In any case, the patent was assigned to Texas Instruments who sold it to Singapore Technologies who then sold it to Rudolph Technologies. I have no financial or business “interest” in it.

      I do have one patent that I am trying to get back but I dont know who it is assigned to right now.

    2. Hey Joe !

      I wanted to ask you some question about your LPS ! What about the linearity ? was it considered when designing the PCB ?



  5. I like your project Joe, and don’t worry, you are violating nothing.
    It isn’t a system for inspection of a work piece. Furthermore it contains none of the four things it should all have to be in violation.
    1 a camera: A CCD is not a camera as it does not have a lens.
    2 a ring light
    3 a linear positioner
    4 a laser

    How did you calculate the beam position of the laser spot? The normal way would be to fit a Gaussian function on it.

    I want to measure the position of 6 laserbeams for an inteferometer. I was thinking to use a normal camera without lens and a large enough sensor.

    1. hmmm a whole bunch of clever laser people quibbling about not a lot of money; how about this………..

      Make me a scanning laser, class1, with a range of say 250m using a 3M 3000x tape target (or further with a prism). Fan the beam so its around 18 degrees (thus allowing for movement of the object its going to fixed to and still see the target) add some auto stabalisation if you can (not the be all and end all but would be nice) and of course as its scanning include an encoder .

      This way I get a simple range and bearing to a target from a moving object; Oh I want a data string output but any old thing will do as Matlab works wonders.

      Now do that and I will pay you $10,000 for a manufactured product or a nice licence fee per unit which I will make myself.

  6. I am trying to build something like this on my own, then i will use this to measure the natural frequency of a structure (bridges, buildings etc). A two dimensional plot and a MATLAB program plus the above sensor. I am starting with scratch. Lets see what happens.

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