Lensless Microscope
From MAKE Magazine
This project first appeared on the pages of MAKE magazine.
Use a webcam’s image chip to create an ultrafine shadow-imaging stage.
- Author: Tom Zimmerman
- Difficulty: Moderate
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Behind the lens of a webcam is an imager chip with thousands of tiny light sensors, each about 1/10 the diameter of a human hair. If you replace the lens with an LED light source, and place tiny objects on the imager chip, shadows will project onto the sensor, creating a lensless microscopic image. You can use the webcam’s regular software to save pictures and video, or stream live images to the internet. Or use the imager chip from a security camera to see a colony of live plankton on TV.
Sections
- Remove the imager board from the webcam.
- Remove the lens.
- Prepare the dark box.
- Prepare the imager.
- Make a spacer.
- Glue the imager into the dark box.
- Prepare the end caps.
- Behold!
- Photos captured by the lensless microscope in various configurations.
Tools
- Drill bit, ¼" approximately, depending on the size of your camera chip’s imaging area
- Hand drill, with 1", ½", and 1" drill bits
- Hobby knife
- Hot glue gun
- Scissors
- Screwdrivers, small, slot and Phillips head
- Soldering iron, with solder
- Square file, small
- Tweezers
- Webcam for output to a computer. Higher resolution and a smaller image chip produce higher magnification. For output to a TV use Monochrome CC D video board camera, such as the PC 302XS from supercircuits.com, $18.
Relevant parts
- PVC end caps (2), 2" black
- PVC pipe, 2"-diameter black, 8" long
- Project enclosure big enough to fit a camera board, RadioShack #270-1809
- Silicone sealant for aquariums. Regular silicone glue from a hardware store contains chemicals that kill organisms.
- Resistor, 1KΩ
- LED, 3mm blue Blue has the shortest wavelength, producing the sharpest image. Experiment with white and other colors.
- Toggle switch, SPST rocker
- Battery, 9V
- Battery snap connector, 9V
- Corrugated cardboard, 3"×3"
- Plastic, 3"×3"×1" thick if needed. See Step 5.
- Masking tape, blue
- Plankton, live available from Reed Mariculture, http://www.reed-mariculture.com
- View:
- Paginated
- Full width
Edit
Step 3
— Prepare the dark box.
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Examine the imager chip. The innermost square is the light-sensitive image die. The raised square just inside the soldered legs is the ceramic case (red outline). Measure out a third square area between these 2 squares, covering most of the fine gold wires that connect to the image die (yellow square). Pick a drill bit with a diameter close to this width. We’ll be referring to this yellow square later.
Use the selected bit to drill a hole centered in the bottom of the project box. Square the hole with the file.
Edit
Step 4
— Prepare the imager.
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You need to cover the chip’s light-sensitive area with tape to protect it from silicone sealant. If the tape is too small, the image will be obscured by sealant.
If the tape is too big, there won’t be enough glass to glue to the dark box. Cut a piece of blue tape the size of the yellow square and center it over the imager chip. As you cut and place the tape, hold it with tweezers so that you don’t get finger oil on it.
Edit
Step 5
— Make a spacer.
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If the imager chip is the tallest component on its circuit board, go to Step 6. But if other components stick up farther from the board’s surface than the imager chip, you need a spacer.
In the center of the 3" x 3" piece of plastic, drill and file a square hole the size of the yellow square.
Drill and file holes to fit over the contours of all tall components, so that the square hole will lie flat over the chip. Place a big wad of aquarium silicone sealant on the entire imager board; more is better. Press the plastic spacer down onto the imager chip, centering the blue tape in the plastic’s square hole. Remove any extruded sealant for a better view. Alignment is critical, so do a careful job. Let the sealant set overnight.
Edit
Step 6
— Glue the imager into the dark box.
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If you made a spacer (Step 5), squeeze a big wad of silicone sealant all over the spacer. Otherwise, squeeze it all over the board and imager chip. More is better.
Place the circuit board in the bottom of the box, pressing it against the square hole and causing sealant to extrude out. Center the blue tape within the square hole, removing any extruded sealant for a better view. Alignment is critical; the entire blue square must be aligned and centered within the box’s square hole. The sealant will create a gasket to prevent water from reaching the circuit board. Let the sealant set overnight.
Find the imager’s glass cover with the point of the hobby knife blade, and drag the blade around the perimeter of the square hole, cutting through the sealant and blue tape. Use tweezers to pull off the sealant and blue tape, revealing a pristine glass surface.
Edit
Step 8
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Drill a 1" hole in the center of the other PVC cap. Solder the LED, battery snap, resistor, and switch in series. If the LED doesn’t light, reverse the battery leads. Press the LED into the 1" hole and hot-glue it and the other components to the top of the cap.
Cut the cardboard into a 2" circle, drill a ½" hole in the center, and cut 10 or so radial lines ¼" inward from the circumference, spaced out approximately evenly, to make tabs that will fold back as you push the disk into the tube. Shove the disk 1" deep and flat into the bottom end of the PVC tube.
The inside of the tube is shiny and could cause reflections that would blur the image, but the hole in the cardboard only lets light coming directly from the LED reach the objects on the imager. This ensures that the shadows cast on the image sensing area are sharp.
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