Cosine response is an important characteristic of an optical detector for irradiance measurements. The non-ideal cosine response of a detector may lead to errors in irradiance measurements. In this paper, a theoretical simulation of irradiance generated due to isotropic point light sources is carried out for different illumination conditions. Simulation results show that the errors in irradiance measurements due to the cosine error of detectors become significantly high at the edges and corners of the floor when a light source is placed at the center of the roof. Further, it is observed that the errors are more in the enclosures having a height smaller than the floor dimensions. Even calibrated detectors measure erratic values of irradiance for a wider angle of incidence. Therefore, cosine errors in irradiance measurements are of great importance especially during the current scenarios of the COVID-19 pandemic, for ensuring the correct dose of Ultraviolet Germicidal Irradiation (UVGI).

余弦响应是用于辐照度测量的光学检测器的一个重要特性。检测器的非理想余弦响应可能会导致辐照度测量误差。在本文中，对不同照明条件下各向同性点光源产生的辐照度进行了理论模拟。仿真结果表明，当光源放置在屋顶中心时，由于探测器余弦误差导致的辐照度测量误差在地板的边缘和角落处变得非常高。此外，据观察，高度小于地板尺寸的机柜的误差更大。即使是经过校准的探测器，也可以测量更宽入射角的辐照度值。所以，