Shimonomura Kazuhiro, Kameda Seiji, Iwata Atsushi, Yagi Tetsuya
Department of Robotics, Ritsumeikan University, Kusatsu, Shiga, Japan.
IEEE Trans Neural Netw. 2011 Sep;22(9):1482-93. doi: 10.1109/TNN.2011.2161591. Epub 2011 Jul 29.
A silicon retina is an intelligent vision sensor that can execute real-time image preprocessing by using a parallel analog circuit that mimics the structure of the neuronal circuits in the vertebrate retina. For enhancing the sensor's robustness to changes in illumination in a practical environment, we have designed and fabricated a silicon retina on the basis of a computational model of brightness constancy. The chip has a wide-dynamic-range and shows a constant response against changes in the illumination intensity. The photosensor in the present chip approximates logarithmic illumination-to-voltage transfer characteristics as a result of the application of a time-modulated reset voltage technique. Two types of image processing, namely, Laplacian-Gaussian-like spatial filtering and computing the frame difference, are carried out by using resistive networks and sample/hold circuits in the chip. As a result of these processings, the chip exhibits brightness constancy over a wide range of illumination. The chip is fabricated by using the 0.25- μm complementary metal-oxide semiconductor image sensor technology. The number of pixels is 64 × 64, and the power consumption is 32 mW at the frame rate of 30 fps. We show that our chip not only has a wide-dynamic-range but also shows a constant response to the changes in illumination.
硅视网膜是一种智能视觉传感器，它可以通过使用模仿脊椎动物视网膜神经元电路结构的并行模拟电路来执行实时图像预处理。为了提高传感器在实际环境中对光照变化的鲁棒性，我们基于亮度恒常性的计算模型设计并制造了一种硅视网膜。该芯片具有宽动态范围，并且对光照强度的变化表现出恒定的响应。由于应用了时间调制复位电压技术，当前芯片中的光电传感器近似于对数光照到电压的转换特性。通过使用芯片中的电阻网络和采样/保持电路，进行了两种类型的图像处理，即类似拉普拉斯 - 高斯的空间滤波和计算帧差。经过这些处理，该芯片在很宽的光照范围内都表现出亮度恒常性。该芯片采用0.25微米互补金属氧化物半导体图像传感器技术制造。像素数为64×64，在30帧/秒的帧率下功耗为32毫瓦。我们表明，我们的芯片不仅具有宽动态范围，而且对光照变化表现出恒定的响应。
