One of the interesting areas of optical-electronic instrument engineering is the design of coherent optical spectrum analyzers, the principle of operation of which is based on performing the Fourier transformation by a lens. When choosing components for designing the optical system of a coherent spectrum analyzer, it is important to find a compromise between the accuracy of measurements and the cost of the device. In some cases, for example, for research at universities, it is advisable to use inexpensive blocks from household appliances and computer peripherals to create laboratory models of spectrum analyzers. In the article, inexpensive designs of optical spectrum analyzers are proposed, which ensure the acquisition of spatial-frequency spectra of images in real time. One of the variants of such structures is a nozzle for a digital camera.