Innovative design of optical system - compensation for image plane drift of short-wave monochromatic light

When designing and calculating an optical system based on a narrowband filter, each monochromatic light of a specific wavelength must be calculated. Design calculations show that after a monochromatic light of a specific wavelength passes through an optical system, the Gaussian image plane will drift. Because from 630 nm (red light) to 405 nm (violet light) and 340 nm (ultraviolet light), as the wavelength becomes shorter, its conjugate distance also gradually becomes shorter. In order to be compatible with the image plane of the entire wide spectrum region, an image plane with an intermediate wavelength has to be selected to make the detector photosensitive surface coincide with it. This is the basic pattern currently used by vending machines. In-depth research shows that because the signals of violet and ultraviolet light are very weak, they are usually amplified by electronic circuits. Obviously, the "noise" is also amplified. This is a last resort. To improve the intensity of violet and ultraviolet signals, the traditional method is to use materials with high transmittance. The author's practice shows that relying solely on traditional methods is not enough. Through exploration, we innovatively "take a two-pronged approach". While working hard on materials, we also added image plane drift compensation measures to achieve good results.

We use the optical transfer function to evaluate the strength of the monochromatic light transmission signal of the biochemical analyzer, because the size of the optical transfer function is closely related to the strength of light energy transmission. Figure 2 shows the MTF values ​​of 6 kinds of monochromatic light, such as 630 nm, 545 nm, 510 nm, 492 nm, 405 nm and 340 nm, based on the Gaussian image plane of 578 nm monochromatic light. Obviously, other colors can meet the design requirements, while the MTF values ​​of 405 nm and 340 nm are 0 when they are less than or equal to 10lp/mm, indicating that the signals of these two monochromatic lights are very weak after transmission in the optical system. For this reason, we innovatively glued a plano-convex lens on the filter, which significantly improved the MTF340… Figure 3 is the optical structure parameter table and its MTF value after adding image plane compensation measures. By detecting the detector photocurrent, it was found that after adding image plane compensation measures, the monochromatic light signal was greatly enhanced, which confirmed the effectiveness of this measure.

MTF value. By detecting the detector photocurrent, it was found that after adding image plane compensation measures, the monochromatic light signal was greatly enhanced, confirming the effectiveness of this measure.