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What is the focal length of a direct reading spectrometer?
Release time: 2019-09-10 10:52:25 Click: 1624
Focal length is a measure of the concentration or divergence of light in an optical system. It refers to the distance from the optical center of the lens to the focal point of light concentration when parallel light is incident. An optical system with a short focal length has a better ability to collect light than an optical system with a long focal length. Simply put, the focal length is the distance between the focal point and the center point of the mask. Only the focal length f <image distance <2f in the camera can be imaged.
Focal length in general
Focal length is an important concept in photography. Simply put, the focal length is the distance from the center of the lens to the plane of the photoreceptor. It is especially important to choose the appropriate focal length for the different objects. The shorter the focal length (the smaller the number), the wider the range that can be accommodated in the shooting screen; the longer the focal length (the larger the number), the narrower the range that the shooting screen can accommodate, somewhat like a telescope. Turn on the phone to take a photo, check the detailed information, you can see the specific focal length of this photo when shooting. Have you paid attention to the focal length issue before?
Focal length is the light gathering ability in the optical system
Focal length, also known as focal length, is a measure of the concentration or divergence of light in an optical system. It refers to the distance from the center of the lens to the focal point of light collection. 或CMOS等成像平面的距离。 It is also the distance from the optical center of the lens to the imaging plane of the film, CCD or CMOS in the camera . An optical system with a short focal length has a better ability to collect light than an optical system with a long focal length.
）能成像，一般用凸透镜做照相机的镜头时，它成的最清晰的像一般不会正好落在焦点上，或者说，最清晰的像到光心的距离(像距)一般不等于焦距，而是略大于焦距。 Convex lens ( convex lens ) can be used for imaging. Generally, when a convex lens is used as the lens of a camera, the clearest image it forms generally does not fall on the focus, or the distance from the clearest image to the optical center Not equal to the focal length, but slightly larger than the focal length. 但实际上总是大于焦距) 。 The specific distance is related to the distance between the object to be photographed and the lens (object distance). The larger the object distance, the smaller the image distance ( but in fact it is always greater than the focal length ) .
A concave lens is also called a negative spherical lens. The lens has a thin center, thick edges, and a concave shape, so it is also called a concave lens. Concave lenses have a divergent effect on light. Myopia glasses are concave lenses.
焦距是什么呢?为什么有这样一个参数,说道这里不得不提到直读光谱仪光学系统的构成, In a direct-reading spectrometer , what is the focal length ? Why is there such a parameter that it is necessary to mention the composition of the optical system of the direct-reading spectrometer ,
1. Excitation system
The excitation system is an extremely important part of the direct-reading spectrometer. Its function is to provide the energy required for excitation to the sample and make the sample glow for subsequent detection. The light emitted by each element after excitation has characteristic spectral lines, and the intensity of these spectral lines has a functional relationship with the content in the sample.
The sample generally contains multiple elements, and different elements will emit different light. But these lights are all mixed together, and the next step is to decompose these composite lights into monochromatic light.
The excitation system may contain an entrance slit: the object point of the spectrometer imaging system is formed under the illumination of the incident light. Collimating element: Make the light from the slit into parallel light. The collimating element may be an independent lens, mirror, or directly integrated on the dispersive element, such as a concave grating in a concave grating spectrometer.
2. Spectroscopy system
The spectroscopic system is the core of the spectroscopic instrument. In the direct-reading spectrometer, the Paschen-Runge device is commonly used, and its function is to disperse the composite light of different wavelengths into monochromatic light. These monochromatic lights have specific connections with specific elements (such as the flame reaction of sodium), and the light intensity can be directly detected.
The spectroscopic system contains dispersive elements: Usually gratings are used to make the optical signal spatially dispersed into multiple beams according to wavelength. Focusing element: Focuses the dispersed beam to form a series of images of the entrance slit on the focal plane, where each image point corresponds to a specific wavelength.
Third, the detection system
The core component of the detection system is the detector. Common detectors are PMT (photomultiplier tube) and CCD (inductive coupling device). CCD is mainly for constant analysis of non-ferrous metal alloy materials (C, S, P, N and other non-metallic measurements are not suitable), while PMT is mainly excellent in ferrous metal testing (non-metallic element analysis is more reliable), for higher purity The non-ferrous metal test is also the first choice for its trace impurity content.
The detection system contains a detector array: placed in the focal plane and used to measure the light intensity of each wavelength image point. The detector array may be a CCD array or other types of photodetector arrays.
Focal length of direct reading spectrometer
Summary of the focal length of direct reading spectrometer
出现的聚光和分光,直读光谱仪中的透镜与焦距有关。 In the above system related to focal length , the focusing and splitting appearing, the lens in the direct reading spectrometer are related to the focal length. 光线就强 。 The smaller the focal length of the convex lens, the stronger the light-gathering ability , because the focus is closer to the center of the lens , and the light is stronger . Lenses of different models and brands include concave and convex lenses, and flat mirrors to focus the excited light.
The above is the relationship between the lens of the direct reading spectrometer and the focal length. The focal length of the parameter of the direct reading spectrometer is related to its lens.