High Precision Depth Acquisition Method Based On Discrete Structured Light

In order to achieve real-time depth measurement with high accuracy,high resolution and high robustness in dynamic scenes,we first propose a structured light depth acquisition method based on two-color discrete coding pattern with image dither.Embedding the DeBruijn sequence represented by two colors in the traditional single-shot cosine pattern to form a two-color phase encoding pattern,this method can realize fast unwrapping of wrapped phase and enlarge the measuring range of depth.Because most projectors have nonlinear problems,the RGB channels of the above two-color phase coding pattern are quantized by using image dither technology,so that the traditional 24-bit image will be converted to 3-bit image,forming a two-color discrete coding pattern,which effectively solves the impact of the non-linear problem of the projector on the measurement results.When measuring in practice,the projected image is blurred by placing the object away from the focal plane of the projector so as to suppress the high frequency component in the template and obtain the ideal cosine image.The results of actual measurement show that this method can effectively measure the depth of complex object surface,and obtain highprecision and high-resolution depth data.The pixel features in the traditional single-shot discrete structured light pattern are vulnerable to decoding errors caused by the texture of the measured object surface.A singleshot discrete grid coding pattern,which is proposed in this paper to effectively solve the above problems,is embedded De-Bruijn sequence represented by short slashes in the uncoded grid pattern,and realizes the unique matching of grid lines by combining the epipolar lines.The pattern has four advantages: First,this pattern uses only two gray values,which is beneficial to reduce the surface texture information of the object to interfere with the feature extraction and improve the robustness of the measurement.Second,the pseudotwo-dimensional De-Bruijin sequence coding method is used to reduce the size of matching window,which is beneficial for measuring the depth data of the hopping surface.Third,using short slashes as features to distinguish encoding features greatly simplifies the steps of feature extraction and makes decoding easier.Last,the coding of grid points has the characteristics of fast positioning.In order to improve the measurement accuracy,the grid lines are extracted from rough to fine,and we use quadratic function and energy optimization function to obtain sub-pixel coordinate positions of lines.According to the experimental results of the Kinect and To F depth cameras,the method of this paper obtains better measurement performance.