Minimal Document Mirror

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Introduction: Minimal Document Mirror

About: Account to share rapid-prototyped scientific devices used in the Harris Lab at Brown Engineering. Our hope is that our posts will serve as accessible launching points for your future applications and designs.…

This device is intended to be a low-cost alternative for sharing handwritten work during video calls. Unlike many existing designs for 3D printed document cameras which use 2" mirrors, this one uses a 1" mirror which makes it more convenient to use while still managing to get an entire 8.5"x11" sheet of paper in frame. It is a universal design which should work with most laptops; the clip is compliant and can bend to match the shape of the laptop lid. In addition, the angle and vertical position of the mirror is adjustable with a thumb screw in order to optimize the mirror position for whatever laptop it's used on. We've included two versions of the mirror holder part of the device to accommodate the different mirrors that may be available - some have adhesive backing while others require mechanical fastening.

Supplies

  1. PLA for 3D printing. Each complete document mirror uses approximately 5 grams of filament.
  2. 1" mirror tiles from Amazon, $12 for 120 of them. Any 1" tiles should work as long as they are around 1-2mm thick.
  3. M3 thumb screws from Amazon, $9 for 30 of them.
  4. M3 nuts from Amazon, $7 for 100 of them.

Each document mirror uses one of each of the mirrors, thumb screws, and nuts, resulting in a cost per device of $0.60, assuming a 1kg roll of PLA costs $25.

Step 1: 3D Printing

First select the appropriate STL file for your usage. The "slide" versions of the files should be used if you have mirrors without adhesive backing (e.g. those linked in the supplies), in the 1-2mm thickness range. The "adhesive" versions of the files should be used if you have adhesive backed mirror tiles. We've also included STL files with 40 document mirrors tiled for mass production.

Printing Parameters:

  • Locate the parts on the printing plate as shown. They should be printed in PLA without supports. We haven't tested other types of filament but the clip relies on the elasticity of the material so others might not work.
  • The extrusion width should be 0.5mm since most features of the part are 1mm in width and are intended to be constructed in 2 passes of the extruder.
  • Infill should be 100%. Most features are thin anyway but this will ensure the proper strength at the fastening location between the parts.
  • Layer height isn't critical - we've tried 0.2mm and 0.3mm and they both worked fine.

Finally, once you have generated the tool-paths for the 3D printer, check to make sure that the corner of the clip marked in red will come out as sharp as possible. When in use, this catches on the lip of the laptop lid so it needs to be sharp in order for the clip to hold securely.

Step 2: Attaching the Mirror

If you have mirror tiles with adhesive backing, simply stick the mirror to the face of the mirror holder as shown in the first image. If using the slide variant of the design, slide the mirror into the slot in the mirror holder as shown in the second image.

Step 3: Assembly

First press the M3 nut into the hexagonal pocket in the mirror holder part. Then, using the thumb screw, fasten the clip and the mirror holder together as shown in the diagram.

Step 4: Using the Document Mirror

First clip the document camera to the lid of your laptop, with the cutout in the clip centered over the webcam. Then, turn on the webcam, loosen the thumb screw, and adjust the mirror so that you can see your entire document. The mirror can be adjusted in both its vertical position as well as its angle. The angle of the computer lid - how open or closed it is - can provide a third point of adjustment to fine tune the frame of view. Once the document mirror is adjusted for your particular laptop, tighten the thumb screw. The document camera can now be removed and clipped on again as needed without having to go through the adjustment process.

Mirroring the Video Feed with Zoom:

Zoom seems to be the preeminent video calling software these days but, as of this writing, it doesn't actually have a way to mirror the video feed. It does have an option which mirrors the video feed that you see, but this doesn't change what others on the call see so your writing will still be reversed for them. We've gotten around this by using the free virtual webcam software ManyCam which acts as a middleman between the webcam and Zoom - you can mirror the video within ManyCam and use ManyCam as the video feed for Zoom in order for others on the call to see your writing the right way around. There are probably other options out there but this could be a good place to start if you encounter this problem.

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    7 Comments

    0
    neatphysics
    neatphysics

    7 months ago

    I love this idea and have shown it to my principal (I am a teacher). I also love the ManyCam software that we recommended since I use multiple cameras to teach science.

    I have seen where a commercial product sold on Amazon had comments where the image shared with the mirror device was so small as to be unusable. I wondered how yours produced the great image that you shared.

    Your computer has what appears to be a large screen, which moves the mirror farther away from the keyboard, which makes a wider view.

    My students mostly have Chromebooks and small-ish notebook computers so the mirror is naturally closer to the keyboard, and would have a smaller field of view.

    Since the camera is in a fixed position/distance-from-keyboard there is no way to raise the mirror and still utilize the webcam.

    Do you think there is a way to use two mirrors to widen the field of view? That would probably remove the need for using an add-on program to reverse the image.

    0
    ElectroFrank
    ElectroFrank

    Reply 7 months ago

    1) If the clip arm were extended, moving the mirror further out away from the camera, the total effective distance (lens to subject) would be increased, giving a wider field of view, but the mirror would then need to be a bit larger.

    (Obviously a science teacher can easily calculate this from the laws of optics !)

    2) An auxiliary plug-in USB camera could obviously be mounted in any convenient position, on or beside the computer, and there is probably some software that could incorporate the image as required.

    3) The cheap little stick-on telephoto and wide angle lenses sold for use use on mobile phones might be useful for something like this. Perhaps someone can develop that idea ?

    0
    harrislab
    harrislab

    Reply 7 months ago

    Thanks for the feedback! The laptop shown is a 13" macbook. We've tried on other laptops as well, with similar success. You are correct that there is a fixed working distance in the design. Two mirrors could make for a nice v2! This design was focused on being minimal yet still adjustable to accommodate different laptops.

    0
    szabonandi.
    szabonandi.

    7 months ago

    Brilliant idea! Congrats!

    0
    markgoatwork
    markgoatwork

    7 months ago

    Clever solution. Splendid! :)

    0
    jessyratfink
    jessyratfink

    7 months ago

    Nicely documented! Thanks very much for sharing, your version looks great :)