Lensless microscopy is a well known imaging technique, commonly referred as digital in-line holographic microscopy. In the established holography methods, both the spatial and temporal coherence of light play a crucial role in determining the resolution of reconstructed object. This strongly restricts this imaging method to use light sources of high spatio-temporal coherence. We report lensless microscopy with a spatially extended white LED, a light source of low spatial and very low temporal coherence. The wave-field propagation between two parallel planes can be obtained using a convolution operation, where the convolution kernel depends on the object-sensor distance and the characteristics of the light source. For a light source of unknown characteristics, this kernel is an unknown function. In the proposed reconstruction method, we decompose this unknown convolution kernel of very large size ($128 \times 128$) into a small unknown light-source-specific kernel (size $9 \times 9$) and a large but known light-source-independent kernel (size $128 \times 128$). This drastically reduces the number of unknown parameters to be estimated at the system identification step, which has been performed here by one time imaging of the known microscopic objects. Final unknown object estimation has been performed using the upper-bound constrained deconvolution. Improvement in resolution has been demonstrated with the imaging of red blood cells.

中文翻译：

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具有低时空相干光源的无透镜在线全息显微镜

无透镜显微术是众所周知的成像技术，通常称为数字在线全息显微术。在已建立的全息方法中，光的空间和时间相干性在确定重建物体的分辨率方面起着至关重要的作用。这强烈限制了这种成像方法使用高时空相干性的光源。我们报告了带有空间扩展的白色 LED 的无透镜显微镜，这是一种低空间和极低时间相干性的光源。两个平行平面之间的波场传播可以使用卷积运算获得，其中卷积核取决于物体-传感器的距离和光源的特性。对于特性未知的光源，这个核是一个未知函数。在提出的重建方法中，$128 \times 128$) 到一个小的未知光源特定内核（大小 $9 \times 9$）和一个大但已知的与光源无关的内核（大小 $128 \times 128$）。这大大减少了在系统识别步骤中要估计的未知参数的数量，这里通过对已知微观物体的一次成像来执行。使用上限约束解卷积执行了最终的未知对象估计。已经通过红细胞成像证明了分辨率的提高。