提出一种使用功率谱相减的实时联合变换相关器作多目标检测。使用这种方法，输入面有两套联合图像。在第二套联合图像中，参考图像是对比度反转的。使用衍射光栅对这两套联合功率谱作相减处理，这种方法可大大抑制输出面的直流项及不想要的伪相关峰，增强相关峰的强度、锐度和峰噪比，提高抗噪声干扰的能力，从而提高对多目标检测的准确度。给出对具有灰度级的多目标输入景物的计算机模拟结果和光学实验结果。实验结果证实了该系统设计及性能分析的正确性。 A real-time joint transform correlator using power spectral subtraction is proposed for multi-target detection. With this method, there are two sets of joint images on the input surface. In the second set of joint images, the reference image is inverted in contrast. Using the diffraction grating to subtract these two joint power spectra, this method can greatly reduce the DC term of the output surface and unwanted pseudo-correlation peaks, enhance the intensity, sharpness and peak-to-peak noise ratio of the correlation peak and improve the anti-noise Interfere with the ability to improve the accuracy of multi-target detection. The computer simulation results and optical experiment results of multi-objective input scene with gray level are given. The experimental results confirm the correctness of the system design and performance analysis.