在利用散射成像法测量激光强度分布中,CCD像面与散射屏平面存在较大角度时,光斑形状和强度分布都会产生严重畸变,给强度分布测量带来较大影响。分析了畸变产生的原因,给出了畸变坐标和理想坐标的数学模型,提出一种结合CCD像素合并的网格法来校正这种畸变。“网格法”利用自制标准网格成像,通过识别网格像边界来确定标准网格和畸变网格的对应关系,利用此对应关系在输出图像时恢复光斑;利用均匀光源成像来校正系统光强分布畸变。结果表明,该方法能够较好地校正光斑的形状畸变;能够实时恢复光斑的真实光强分布,单元强度畸变恢复误差小于1%。该校正方法在激光强度分布散射成像测量中非常实用。

The tilt between CCD and diffusion screen will result in the spot geometry and intensity distortion,which will worsen the measurement result of spot distribution. The reason for distortion is analyzed,and the position relation between distorted grids and ideal grids is established by polynomial model. A grid method of rectifying distortion based on uniting pixels is presented. The distorted image of the self-designed and fabricated “standard grid target board” corresponds the standard grid through distinguishing from the borders of the grids. The corresponding relation can help to recover the spot geometry. It can rectify intensity distortion through the image of uniform light. Experiments prove that the means can not only calibrate the spot geometry but also rectify intensity distortion. The calibrating precision is within 1%. The method is very practical in measuring laser intensity distribution.