Carpentras Dino, Laforest Timothé, Künzi Mathieu, Moser Christophe
Opt Express. 2018 Mar 19;26(6):6785-6795. doi: 10.1364/OE.26.006785.
The observation of retinal cellular structures is fundamental to the understanding of eye pathologies. However, except for rods and cones, most of the retinal microstructures are weakly reflective and thus difficult to image with state of the art reflective optical imaging techniques such as optical coherence tomography. Recently, we demonstrated the possibility of obtaining the phase contrast of retinal cells in the eye using oblique illumination of the retina. Indeed, by illuminating the eye with incoherent oblique illumination, we obtain a secondary oblique illumination from the backscattered light which can then be used to obtain phase contrast in an effective transmission-like configuration. In this technique, a weak phase signal is modulated over an intense background. Maximizing this phase contrast is thus crucial for the image quality. Here, we investigate the parameters that affect phase contrast by modelling image formation with the backscattered light. We find that the key parameter for maximizing contrast is the intensity profile of the backscattered light. Specifically, the gradient of the profile is found to be proportional to the phase contrast. We validate the model by comparing simulations with experimental results on ex-vivo retina samples.
视网膜细胞结构的观察对于理解眼部病变至关重要。然而，除了视杆细胞和视锥细胞外，大多数视网膜微观结构的反射较弱，因此难以用诸如光学相干断层扫描等先进的反射光学成像技术进行成像。最近，我们证明了利用视网膜的斜照光获取眼内视网膜细胞相位对比度的可能性。实际上，通过用非相干斜照光照亮眼睛，我们从后向散射光中获得二次斜照光，然后可用于在类似有效透射的配置中获得相位对比度。在该技术中，微弱的相位信号在强烈的背景上被调制。因此，最大化这种相位对比度对于图像质量至关重要。在这里，我们通过对后向散射光的图像形成进行建模来研究影响相位对比度的参数。我们发现最大化对比度的关键参数是后向散射光的强度分布。具体而言，发现该分布的梯度与相位对比度成正比。我们通过将模拟结果与离体视网膜样本的实验结果进行比较来验证该模型。
