RU205270U1 - Mini-spectrograph for field measurements - Google Patents

Abstract

The utility model relates to the field of measuring technology and concerns a mini-spectrograph. The mini-spectrograph is designed to be connected to a smartphone and contains an entrance slit, a flat reflective line diffraction grating, two spherical mirrors, and a recording element. The optical element of the spectrograph is made in the form of a monoblock made of optically transparent acrylic with a refractive index of 1.50 and a Czerny-Turner configuration. The entrance slit, the entrance mirror and the diffraction grating are located on the surface of the monoblock and provide diffraction in the visible spectrum in the second order. The output spherical mirror collects the diffracted light and focuses it onto the output surface with a recording element. A linear array of photodiodes is used as a recording element. The technical result consists in simplifying the process of manufacturing the device and processing the monolith of the monoblock. 3 ill.

Description

The utility model relates to measuring equipment, namely to small-sized spectral instruments designed for various types of spectral analysis of optical radiation in the field in real time, and can be used in various areas of the national economy.

Known "Mini-spectrometer for a smartphone" (see RF patent No. 184760, G01J 3/18, G02F 1/00, G01T 7/00, publ. 07.11.2018, bull. No. 31), consisting of an opaque body, inside which an optically homogeneous monolithic acrylic body is placed, on one side of which a pass-through plastic diffraction grating is glued, on the other side an output mirror is formed for projecting the spectrum onto a smartphone camera. The smartphone camera records the radiation spectrum, the smartphone processor processes the parameters of the recorded spectrum according to a specially developed program, the result of the spectrum processing is displayed on the smartphone screen.

The main disadvantage of this device is the narrow measurable spectral range, limited by the spectral characteristic of the smartphone camera operating in the visible wavelength range of 400-760 nm.

The closest in technical solution is a spectrograph containing an optically coupled entrance slit, a concave spherical diffraction grating with curvilinear unequally spaced strokes and a recording device with a flat receiving surface, in front of which an optical element is installed, characterized in that the optical element is made in the form of a monoblock of optically transparent material in such a way that the diffraction grating, the recording device and the entrance slit are located on the surface of the monoblock, with the entrance slit located on the plane, and the diffraction grating and the recording device, respectively, on the spherical surfaces of the monoblock with radii of curvature r and R, where r is the radius of curvature concave spherical lattice, a R = (0.8-1.2) r, taken as a prototype (see RF patent No. 2329476, G01J 3/18, 20.07.2008, bull. No. 20).

The main disadvantage of this device is the high cost of purchasing a spherical concave diffraction grating with curvilinear unequally spaced strokes, the complexity of processing a monoblock made of optically transparent material during manufacture.

The task of the utility model is to create a broadband mini-spectrograph for a smartphone.

The technical result is to simplify the manufacture and processing of the monolith of the monoblock of the mini-spectrograph.

This is achieved by the fact that in the proposed device for a mini-spectrograph for a smartphone, made with the ability to connect to a smartphone and containing an optically coupled entrance slit, a flat reflective line diffraction grating, two spherical mirrors and a recording element, the optical element is made in the form of a monoblock of optically transparent acrylic with a refractive index of 1.50 and a Czerny-Turner configuration in such a way that the entrance slit, the entrance mirror of radius R and the diffraction grating are located on the surface of the monoblock and provide diffraction in the visible spectrum in the second order, and the output spherical mirror of radius R collects the diffracted light and focuses it to the output surface with a recording element, and a linear array of photodiodes is used as a recording element.

The utility model is illustrated by drawings.

FIG. 1 shows a general view of a spectrograph in a housing mounted on a smartphone.

FIG. 2 shows a graphical representation of the monolithic body of a mini-spectrograph.

FIG. 3 shows the layout of the spectrograph components located in the case, which is mounted on a smartphone and consists of a fiber-optic cable, a mini-spectrograph, an electronic registration board with a USB interface, an interface cable for connecting to a smartphone and a smartphone.

The mini-spectrograph (Fig. 2) consists of a monolithic body 1, an input surface 2 on which an input slit 3 is glued, an input mirror 4, a glued diffraction grating 5, an output mirror 6, an output surface 7, on which a recording device module is glued - a linear matrix photodiodes 8. The monolithic body 1 of the mini-spectrograph is a monolithic acrylic component made of PMMA optical acrylic. Acrylic has a relatively high refractive index (~ 1.50) and a transmission spectrum up to 350 nm. Acrylic is a relatively tough transparent and optically homogeneous material and can be processed without special precautions.

The device operates as follows (Fig. 3).

Radiation from the source under study is fed through a fiber-optic cable to the entrance slit of the monolithic body of the spectrograph. Further, the light beam, having passed the monolithic body of the spectrograph, falls on the input mirror, after which the reflected collimated beam falls on the diffraction grating. The diffracted light reflected from the grating is collected and focused by the exit mirror onto the exit surface with a recording element. Data from the array of photodiodes is sent via a flexible polyamide cable to an electronic registration board with a USB interface and then, via an interface cable, to a USB connector of a smartphone for further processing.

The monolithic mini-spectrograph with dimensions of 5 × 8.5 × 2.5 cm is a robust, vibration-resistant, inexpensive compact device capable of simultaneous multichannel measurements of wavelengths and bandwidths of sources in the visible light and near-infrared spectrum and has resolution more than sufficient to resolve near infrared wavelengths of 1060 nm in the first order from optical wavelengths 454, 472, 488, 496, 514 and 532 nm in the second order. The mini-spectrograph has sufficient linear space in the exit focal plane so that the wavelengths of interest are distributed approximately two centimeters apart. The inlet and outlet mirrors are coated with aluminum and magnesium fluoride for air shielding. The radius of curvature for both mirrors is R = 10.0 cm.The mini-spectrograph uses a grating with a large number of grooves (GR13-1205 - reflective line diffraction grating, 1200 lines / mm, size: 2.5 cm × 2.5 cm × 6 mm, Thorlabs). The grating is attached with optical glue with a refractive index approximately equal to that of acrylic. Unused surfaces of the acrylic body are coated with a black epoxy adhesive with a refractive index approximately equal to that of the acrylic body.

The proposed monolithic design is distinguished by temperature and vibration indispensability, which makes it possible to use the device in technological lines, field conditions, etc. Increased dust and moisture resistance makes it possible to work in conditions of increased aggressiveness of the environment.

Another advantage of the monolithic scheme is a significant simplification of the design due to the practical absence of mechanical parts of the nodes of the entrance slit, grating and photodetector. As a result, the assembly and alignment of the optical circuit is greatly simplified, in addition, there is no need for a massive base fixing the position of the circuit elements, in view of this, the requirements for the case are significantly weakened. All of the above leads to a significant reduction in the cost of the device in mass production.

Claims (1)

Mini-spectrograph made with the possibility of connecting to a smartphone and containing an optically coupled entrance slit, a flat reflective line diffraction grating, two spherical mirrors and a recording element, characterized in that the optical element is made in the form of a monoblock of optically transparent acrylic with a refractive index of 1.50 and the Czerny-Turner configuration in such a way that the entrance slit, the entrance mirror of radius R and the diffraction grating are located on the surface of the monoblock and provide diffraction in the visible spectrum in the second order, the output spherical mirror of radius R collects the diffracted light and focuses it on the exit surface with a recording element , and a linear array of photodiodes is used as a recording element.

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