How 3D Printing Is Used to Create a Lens-Free AI Camera

A conventional camera bends light with glass and lets the sensor record an image. A lens-free design does the opposite. A thin patterned mask sits a few millimeters above the sensor, and each sensor pixel records a coded shadow. Software then reconstructs the scene from that pattern. No focus ring, no lens barrel, no alignment of multiple glass elements.

That sounds like less mechanical work. In practice it moves the precision problem to a different place. The mask pattern sets the angular resolution. A 50 μm hole is not fine enough for useful reconstruction; you want feature sizes in the 5–20 μm range with clean edges. The gap between mask and sensor must be uniform across the whole array, because a 20 μm tilt error changes the shadow geometry from one side of the sensor to the other.

So the housing is not a cosmetic shell. It is the optical bench. Every surface that touches the mask, the spacer, or the sensor PCB sets the final image quality. This is where 3D printing is used to create the first prototypes, and where CNC machining takes over for the parts that hold tolerance.

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  Mask feature size5–20 μm openings; below that, diffraction and print resolution both hurt.
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  Mask-to-sensor gapTypically 0.5–5 mm, held uniform to a few micrometers across the array.
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  PlanarityMask and sensor planes flat enough that the coded shadow stays predictable.
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  Stray lightMatte internal walls; a glossy printed surface bounces light onto the sensor.

The first job for additive manufacturing is geometry you cannot mill cheaply. A lens-free camera often needs an internal baffle stack, curved light traps, and a cable channel that runs beside the sensor. Printed in one piece, those features cost nothing extra. Machined from a single block, they need long reach tooling and multiple setups.

The second job is fit checks. A printed body lets you test whether the PCB, the connector, and the mask frame actually stack the way the CAD says. You find out in a day instead of after a mold is cut. For enclosure iterations at 5 to 20 units, resin printing at 0.05 mm layer height is usually enough to catch interference.

The third job is low-stress brackets and covers. A printed sensor shroud or a printed back plate carries no load and holds no optical alignment. Print it, paint the inside matte black, and move on. Keep printed parts away from the two surfaces that matter: the mask seat and the sensor seat.

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  Good printed partsBaffles, light traps, cable routing, outer shell, non-critical brackets.
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  Parts to reconsiderMask holder, spacer ring, sensor seat, any surface in the optical path.
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  Typical processSLA or DLP resin for detail; SLS nylon for tougher enclosures.

Print resolution is the first limit. A resin printer with a 50 μm pixel and a 25 μm layer cannot hold a 10 μm aperture edge cleanly. The opening closes up, or the edge frays. Even a high-end projection printer loses the sharpness you need for coded aperture reconstruction.

Flatness is the second limit. Resin shrinks as it cures, and thin plates warp. A mask holder printed flat may be 30–50 μm out of plane after post-cure. That error goes straight into the optical gap. Machined aluminium or stainless holds flatness in the single-digit micrometer range, and we can lap the seating face if the design calls for it.

Temperature and moisture are the third limit. A printed resin spacer changes thickness with humidity and creep under spring load. Over a 40 °C swing, the gap moves and the reconstruction model drifts. Metals do not do that. For a camera that ships and gets used outdoors, this is the deciding factor. We machine the mask holder, the spacer ring, and the sensor seat from aluminium or stainless, then anodize or blacken them to cut internal reflections.

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  Tolerance±0.005 mm on critical seats, verified with CMM reports.
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  FinishRa 0.8–1.6 μm on mating faces; matte black to reduce stray light.
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  Materials6061-T6 and 7075 aluminium, 304 or 316L stainless, depending on mass and stiffness.

Start with the full stack in CAD: sensor board, spacer, mask, baffle, shell. Print the shell and baffles in resin. Machine the spacer ring, the mask holder, and any seat that touches the sensor. Measure the spacer on a CMM before assembly, because that number goes into the reconstruction model.

Assemble in a dark room. Check for light leaks with the sensor gain turned up and the aperture covered. Light leaks show up as a gradient in the raw frames and ruin the coded pattern. Paint or anodize every internal surface; a bare machined face reflects enough to matter.

Once the geometry is stable, run the reconstruction and look at resolution, not at how the photo looks. If resolution is poor, the usual causes are mask feature size, gap uniformity, or a tilted sensor. Adjust one variable at a time. When the design freezes, the shell can move to injection molding or die casting, while the mask holder and spacer stay on the CNC line.

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  Print firstShell, baffles, cable routing, fit-check parts.
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  Machine firstMask holder, spacer, sensor seat, any alignment feature.
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  InspectCMM on the spacer and mask seat; flatness and parallelism recorded.