Kinect V1结构光激光散斑原理及样式



  对 intel realsense F200 和 Kinect V1的coding pattern原理进行调研，知二者都使用light coding的方式，该方法与传统的coded structure light不同：传统编码结构光（空间编码，时间编码）最终使用的是三角测量的原理计算深度信息；light coding通过投射具有高度伪随机性的激光散斑，会随着不同距离变换不同的图案，对三维空间直接标记，通过观察物体表面的散斑图案就可以判断其深度。

  参考PrimeSense light coding技术，知其特点如下：

1. （Components）Optical apparatus, including first and second diffractive optical elements(DOEs) arranged in series to diffract an input beam of radiation. The first DOE is configured to apply to the input beam a pattern with a specified divergence angle, while the second DOE is configured to split the input beam into a matrix of output beams with a specified fan-out angle. The divergence and fan-out angles are chosen so as to project the radiation onto a region in space in multiple adjacent instances of the pattern.

2. （Size）The first DOE applies, such as an uncorrelated pattern to input beam; the second DOE project pattern onto surface over a wide angular range. In Kinect V1, it creates 15 beams, in a 3x5 fan-out, the second DOE also can be 3x3, 5x5, 7x7 or other fan-out patterns.

3. （Properties）The phase mask of second DOE comprises a periodic pattern of repeating cells. The dimensions of the cells in the pattern control the fan-out angle between tiles, which correspond to different diffraction orders of the periodic pattern. For the case of 3x3 tiling, the dominant spatial frequencies of the phase mask of the second DOE are typically roughly twice those of first DOE along both the X and Y axes in order to give the desired relation between the specified fan-out and divergence angles.

4. （Power）The shape of the phase mask within each cell of second DOE controls the power distribution among the different output beams. It can be designed to give either uniform light intensity distribution among tiles or a predefined non-uniform intensity distribution.

下面给出Kinect V1在不同距离产生的激光散斑图案：

0.5m

1.0m

1.5m

2.0m

2.5m