OpenAR 2.0

Introducing OpenAR 2.0, an augmented reality headset.

Open-source AR for education and hobbyists

OpenAR 2.0 is an open-source augmented reality (AR) headset designed to be affordable, easy to build, and highly customizable. Most of the structural components are 3D printed, making the device accessible to hobbyists, students, and educators with access to a 3D printer and PLA filament. OpenAR 2.0 is suitable for

  • students learning optics or electronics,
  • teachers looking for laboratory demonstrations,
  • makers interested in wearable technology,
  • companies looking to reduce costs, and
  • anyone curious about how AR displays work.

How is it different from other AR headsets? Commercial AR headsets use sophisticated waveguides and custom optics. OpenAR 2.0 instead demonstrates the underlying principles using inexpensive off-the-shelf components, making the optical system easy to understand and reproduce.

Off-the-shelf? The total cost of the project is typically between 35–60 €, depending on component prices and suppliers. The price includes all the electronics, optical components, filament, and accessories. Most of the cost comes from the electronic components.

Open source! All design files, firmware, and documentation are freely available. The project is intended as a starting point rather than a finished product to encourage you to modify the hardware and software and to adapt the design to your own needs.

The optical and electronic components of OpenAR 2.0. Although the device may appear complex, its optical design is based on a simple arrangement of readily available components.

OpenAR 2.0 is designed to accommodate a variety of commonly available components. For example, if you use a different display, you can adapt the corresponding 3D printed mounting part to fit it. The provided firmware is also compatible with multiple STM32 development boards with only minor modifications.

The documentation linked at the bottom of this page explains the operating principles of the optical system, lists the required components, and provides detailed step-by-step assembly instructions. It also includes the original Fusion 360 (.f3d) design files together with STEP files and print-ready .STL and .3MF files for all 3D printed parts.

After building this device, you’ll understand how augmented reality works—from optics and image formation to embedded electronics and 3D-printed mechanical design—and you’ll end up with a platform you can modify and experiment with.

How it works

The optical system consists of a display, a lens, a mirror, and two partially reflective glass plates mounted in a 3D printed frame. The image is generated by a small LCD display and guided toward the user’s eyes with the optical components.

Top-down view of the optical path from the display to the user’s eyes. The light from a single pixel propagates as a diverging cone and is collimated by the lens, which it passes twice due to the mirror. The parallel beams are reflected toward the eyes with the glass plates. The eye closer to the lens sees a brighter image.

The reference design uses the following optical components:

  • 1.3-inch 240 × 240 LCD display.
  • Two partially reflective glass plates cut from a thin sheet of clear glass.
  • +3.5 diopter lens taken from a pair of reading glasses.
  • Small mirror cut from a rectangular makeup mirror.

These inexpensive, readily available components form the complete optical system.

The electronics are built around an STM32 Blue Pill development board, which is programmed using an ST-LINK/V2 programmer. Although the Blue Pill includes an onboard 3.3 V voltage regulator, it is not suitable for battery-powered operation in this design because it requires a larger input-to-output voltage difference than is available as the LiPo battery discharges. Instead, the circuit uses an external low-dropout (LDO) voltage regulator together with the required capacitors. The complete circuit diagram and additional design details are available in the OpenAR 2.0 documentation.

The headset is powered by a rechargeable 3.7 V, 1500 mAh lithium-polymer (LiPo) battery with an integrated protection circuit module (PCM). A Micro-USB charging module is used to recharge the battery.

Apart from the electronic and optical components, nearly all remaining parts are 3D printed and assembled using standard M2 and M3 fasteners. (The reference design also uses a small compression spring, which can be salvaged from a retractable ballpoint pen.)

Components

The OpenAR 2.0 headset was built using the components listed below. Note—they are only examples; many of them can easily be replaced. The following links will take you to retailers where you can purchase the parts or look for similar products. Prices vary depending on the supplier. However, the headset can typically be built for around 40 €.

Make it your own

OpenAR 2.0 is intended as a starting point rather than a finished product. You can replace the display, modify the 3D-printed parts, experiment with the optics or adapt the electronics. Let your imagination guide you and explore what you could create with augmented reality!

Downloads

The OpenAR 2.0 documentation provides detailed assembly instructions and step-by-step instructions for programming the STM32 Blue Pill and running the demo on the display. The original CAD models and print files, and the demonstration firmware are also freely available.

Click the following links to download the files.

Licenses

3D models: OpenAR © 2025 by University of Eastern Finland is licensed under CC BY-NC 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc/4.0/

Demo program: Copyright 2025 University of Eastern Finland. Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at https://www.apache.org/licenses/LICENSE-2.0. Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.