We proposed a design for a LASER pico-projector with a low speckle contrast value and high contrast ratio that maintains system efficiency. The method for speckle contrast reduction utilizes two diffusers and a Voice Coil Motor (VCM) oscillator. The two different diffusers for a high contrast ratio and high system efficiency can be divided into two categories. In Category 1, the speckle contrast value can be decreased to 2.80% by using a circular symmetric diffuser. At the same time, the full-on/full-off (FO:FO) contrast ratio can be maintained within 1200:1-1300:1, but the system efficiency decreases 1.50%. In Category 2, the speckle contrast value can be reduced to 6.50% by using an elliptically scattering diffuser. At the same time, the FO:FO contrast ratio can be maintained within 1300:1-1400:1, and the system efficiency decreases by only 1.00%.

We proposed a design for a laser mini-projector with a low speckle contrast value and high contrast ratio that maintains system efficiency. The key design is that two diffusers are located in the two sides of the light tunnel. By vibrating the 30 × 30 diffuser under 100 Hz, the speckle contrast value can be decreased to 2.32% which is invisible to the human eye. Considering the trade-off issue of optical efficiency and speckle noise, the most suitable arrangement with circular diffusers is ‘30 × 30H, 5 × 5. The vibration direction is at the long side of the light tunnel.