Lensless single-shot dual-wavelength digital holography is resolution limited by the pixel-size of the camera and often has an insufficient depth range. We present a novel dual-wavelength holographic configuration with expanding wavefront illumination that breaks the pixel-limited resolution barrier and achieves diffraction-limited spatial resolution. By implementing expanding wavefront illumination with dual-wavelength digital holography based on a wavelength-tunable laser, we achieve a high-resolution centimeter-scale depth range. A quantitative precision analysis demonstrates that single-shot acquisition reaches the shot-noise-limited depth detection. The proposed holographic scheme provides a robust 3D optical inspection solution for high-throughput, micro-scale resolution industrial inline metrology.

We demonstrate lensless single-shot dual-wavelength digital holography for high-speed 3D imaging in industrial inspection. Single-shot measurement is realized by combining off-axis digital holography and spatial frequency multiplexing of the two wavelengths on the detector. The system has 9.1 µm lateral resolution and a 50 µm unambiguous depth range. We determine the theoretical accuracy of off-axis dual-wavelength phase reconstruction for the case of shot-noise-limited detection. Experimental results show good agreement with the proposed model. The system is applied to industrial metrology of calibrated test samples and chip manufacturing.