Multispectral imaging has been used for numerous applications in e.g., environmental monitoring, aerospace, defense, and biomedicine. Here, we present a diffractive optical network-based multispectral imaging system trained using deep learning to create a virtual spectral filter array at the output image field-of-view. This diffractive multispectral imager performs spatially-coherent imaging over a large spectrum, and at the same time, routes a pre-determined set of spectral channels onto an array of pixels at the output plane, converting a monochrome focal-plane array or image sensor into a multispectral imaging device without any spectral filters or image recovery algorithms. Furthermore, the spectral responsivity of this diffractive multispectral imager is not sensitive to input polarization states. Through numerical simulations, we present different diffractive network designs that achieve snapshot multispectral imaging with 4, 9 and 16 unique spectral bands within the visible spectrum, based on passive spatially-structured diffractive surfaces, with a compact design that axially spans ~72λ_m, where λ_m is the mean wavelength of the spectral band of interest. Moreover, we experimentally demonstrate a diffractive multispectral imager based on a 3D-printed diffractive network that creates at its output image plane a spatially repeating virtual spectral filter array with 2 × 2 = 4 unique bands at terahertz spectrum. Due to their compact form factor and computation-free, power-efficient and polarization-insensitive forward operation, diffractive multispectral imagers can be transformative for various imaging and sensing applications and be used at different parts of the electromagnetic spectrum where high-density and wide-area multispectral pixel arrays are not widely available.

多光谱成像已用于环境监测、航空航天、国防和生物医学等领域的众多应用。在这里，我们提出了一种基于衍射光学网络的多光谱成像系统，该系统使用深度学习进行训练，以在输出图像视场中创建虚拟光谱滤波器阵列。这种衍射多光谱成像仪在大光谱上执行空间相干成像，同时将一组预先确定的光谱通道路由到输出平面的像素阵列，将单色焦平面阵列或图像传感器转换为没有任何光谱过滤器或图像恢复算法的多光谱成像设备。此外，这种衍射多光谱成像仪的光谱响应度对输入偏振态不敏感。通过数值模拟，λ _m，其中λ _m是感兴趣的光谱带的平均波长。此外，我们通过实验展示了一种基于 3D 打印衍射网络的衍射多光谱成像仪，该成像仪在其输出图像平面上创建了一个空间重复的虚拟光谱滤波器阵列，在太赫兹光谱中具有 2 × 2 = 4 个独特波段。由于其紧凑的外形尺寸和免计算、高能效和偏振不敏感的前向操作，衍射多光谱成像仪可以为各种成像和传感应用带来变革，并用于高密度和宽光的电磁波谱的不同部分。区域多光谱像素阵列并未广泛使用。