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What is the focal length of a direct reading spectrometer?
Release time: 2019-09-10 10:52:25 Click: 1398
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 the light when the parallel light is incident. Optical systems with short focal lengths have a better ability to collect light than optical systems with long focal lengths. Simply put, the focal length is the distance from the focal point to the center point of the mirror. Only the focal length f <image distance <2f in the camera can be used for imaging.
Focal length in general
Focal length is an important concept in photography. In simple terms, 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 right focal length for different subjects. The shorter the focal length (the smaller the number), the wider the range that can be accommodated in the shooting frame; the longer the focal length (the larger the number), the narrower the range that can be contained in the photographing frame, a bit like a telescope. Turn on your phone to take a picture, check the detailed information, and you can see the specific focal length when the picture was taken. Have you paid attention to the focal length before?
Focal length is the ability to concentrate light in an optical system
Focal length, also known as focal length, is a measure of the concentration or divergence of light in an optical system, and refers to the distance from the center of the lens to the focal point of light convergence. 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 lens, CCD or CMOS in the camera . Optical systems with short focal lengths have a better ability to collect light than optical systems with long focal lengths.
）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。 A convex lens can be used for imaging. Generally, when a convex lens is used as a camera lens, the clearest image formed by it generally does not fall exactly on the focal point, or the distance between the clearest image and the optical center ( image distance ) is generally Not equal to focal length, but slightly larger than focal length. 但实际上总是大于焦距) 。 The specific distance is related to the distance between the illuminated object and the lens (object distance). The larger the object distance, the smaller the image distance ( but it is always greater than the focal distance ) .
Concave lenses are also called negative spherical lenses. The middle of the lens is thin, the edges are thick, and they are concave, so they are also called concave lenses. Concave lenses have a diverging 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 ? I have to mention here the composition of the optical system of a direct reading spectrometer .
First, the excitation system
The excitation system is an extremely important component of the direct-reading spectrometer. Its role is to provide the sample with the energy required for excitation and make the sample emit light for subsequent detection. The light emitted after the excitation of each element has characteristic spectral lines, and the intensity of these spectral lines has a functional relationship with the content in the sample.
Samples generally contain multiple elements, and different elements emit different light. But these lights are all mixed together, and the next step is to break down the composite light into monochromatic light.
The excitation system may contain an incident slit: the object point of the spectrometer imaging system is formed under the irradiation of incident light. Collimation element: Makes the light from the slit into parallel light. The collimating element may be an independent lens, a mirror, or a direct integration on a dispersive element, such as a concave grating in a concave grating spectrometer.
Second, the spectroscopic system
The spectroscopic system is the core of the spectrometer. A Paschen-Lunger device is commonly used in direct-reading spectrometers, and its role is to disperse composite light of different wavelengths into monochromatic light. These monochromatic lights are associated with specific elements (such as the flame reaction of sodium), and the light intensity can be directly detected.
The spectroscopic system contains a dispersive element: gratings are usually used to disperse the optical signal into multiple beams in space according to wavelength. Focusing element: Focuses the dispersed beam to form a series of incident slit images 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 the constant analysis of non-ferrous metal alloy materials (non-metal measurement such as C, S, P, N is not suitable), while PMT is mainly excellent in the testing of ferrous metals (non-metal element analysis is more reliable), and has a 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 on the focal plane and used to measure the light intensity of each wavelength image point. The detector array may be a CCD array or another kind of light detector array.
Direct Reading Spectrometer Focal Length
Summary of 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 systems related to focal length , the focusing and splitting of the light appear, and the lens in the direct reading spectrometer is related to the focal length. 光线就强 。 The smaller the focal length of the convex lens is, the stronger the light gathering ability is , because the focus is closer to the lens center , the light is stronger . Different types of lenses include concave and convex lenses, as well as plano lenses, which focus the excited light.
The above is the relationship between the direct reading spectrometer lens and focal length. The direct reading spectrometer parameter focal length is related to its lens.