Light feedback type formaldehyde detection device

Abstract

The utility model discloses an optical feedback type formaldehyde detection device which comprises a semiconductor laser, an absorption cell is mounted at the output end of the semiconductor laser, and a piezoelectric ceramic crystal is mounted on one side of the absorption cell; a photodiode and a laser diode are arranged in the semiconductor laser, and the output end of the laser diode is connected to the input end of the photodiode through an optical signal; the output end of the photodiode is provided with a Fourier transform module; the input end of the laser diode is provided with a driving module; a formaldehyde sampling pump is arranged at the input end of the absorption tank; the input end of the piezoelectric ceramic crystal is provided with a control module. The device adopts the length change of piezoelectric ceramics to modulate the light wave phase, forms carrier waves absorbed by formaldehyde gas, and has the advantage of reducing the detection difficulty; the laser device adopted by the device is a single longitudinal mode semiconductor laser device, laser wavelength can be finely adjusted according to a formaldehyde gas absorption wave band, and the device has the advantage of high sensitivity.

Description

Technical Field

[0001] The utility model relates to the technical field of formaldehyde detection equipment, in particular to a light feedback type formaldehyde detection device. Background Art

[0002] In order to ensure the safety of the living environment, it is particularly important to detect the formaldehyde content in indoor air. At present, there are many methods for determining formaldehyde, mainly spectrophotometry, chromatography, electrochemical analysis and instrument detection. However, electrochemical analysis often has problems such as interference and instability, so it is rarely used. Spectrophotometry and chromatography are relatively cumbersome, and the equipment is relatively large, which is difficult to meet the current needs of rapid detection. Therefore, a light feedback formaldehyde detection device is proposed. Utility Model Content

[0003] The main purpose of the utility model is to provide a light feedback formaldehyde detection device to solve the above technical problems.

[0004] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a light feedback formaldehyde detection device, comprising a semiconductor laser, an absorption cell is installed at the output end of the semiconductor laser, and a piezoelectric ceramic crystal is installed on one side of the absorption cell; the semiconductor laser has a built-in photodiode and a laser diode, and the output end of the laser diode is connected to the input end of the photodiode through an optical signal; a Fourier transform module is provided at the output end of the photodiode; a driving module is provided at the input end of the laser diode; a formaldehyde sampling pump is provided at the input end of the absorption cell; and a control module is provided at the input end of the piezoelectric ceramic crystal.

[0005] On the basis of the above scheme and as a preferred scheme of the above scheme: the output end of the laser diode is connected to the input end of the photodiode through an optical signal, and the photodiode is used for photoelectric conversion of the laser self-mixing signal.

[0006] On the basis of the above scheme and as a preferred scheme of the above scheme: the laser wavelength of the laser diode is in the absorption band of formaldehyde, and the absorption cell is in high transmittance at the laser wavelength of the laser diode.

[0007] On the basis of the above scheme and as a preferred scheme of the above scheme: the output end of the laser diode is aligned with the absorption cell; the axis of the absorption cell is coaxial with the laser emitted by the laser diode and perpendicular to the reflection surface of the piezoelectric ceramic crystal.

[0008] On the basis of the above solution and as a preferred solution of the above solution: the control module generates an AC voltage signal to change the length of the piezoelectric ceramic crystal.

[0009] On the basis of the above solution and as a preferred solution of the above solution: the driving module is used to generate an injection current of the laser diode and change the output laser wavelength.

[0010] The beneficial effects of the utility model are as follows:

[0011] 1. This device uses the length change of piezoelectric ceramics to modulate the phase of light waves to form a carrier absorbed by formaldehyde gas, which has the advantage of reducing the difficulty of detection.

[0012] 2. The laser used in this device is a single longitudinal mode semiconductor laser, which can fine-tune the laser wavelength according to the absorption band of formaldehyde gas and has the advantage of high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is an overall schematic diagram of the utility model. DETAILED DESCRIPTION

[0014] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments. However, the specific implementation methods and embodiments described below are for illustrative purposes only and are not intended to limit the present invention.

[0015] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0016] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0017] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0019] See attached figure Figure 1 In this embodiment, a light feedback formaldehyde detection device includes a semiconductor laser 1, an absorption cell 2 is installed at the output end of the semiconductor laser 1, and a piezoelectric ceramic crystal 3 is installed on one side of the absorption cell 2; the semiconductor laser 1 has a built-in photodiode 10 and a laser diode 11, and the output end of the laser diode 11 is connected to the input end of the photodiode 10 through an optical signal; a Fourier transform module 4 is provided at the output end of the photodiode 10; a driving module 5 is provided at the input end of the laser diode 11; a formaldehyde sampling pump 6 is provided at the input end of the absorption cell 2; and a control module 7 is provided at the input end of the piezoelectric ceramic crystal 3.

[0020] Furthermore, the semiconductor laser 1 in this embodiment is electrically driven; the semiconductor laser 1 has a built-in photodiode 10 and a laser diode 11; the output end of the driving module 5 is connected to the input end of the laser diode 11, and the driving module 5 is used to generate an injection current for the laser diode 11 to change the output laser wavelength; the output end of the laser diode 11 is connected to the input end of the photodiode 10 through an optical signal, and the photodiode 10 is used for photoelectric conversion of the laser self-mixing signal.

[0021] Furthermore, the output end of the photodiode 10 is connected to the input end of the Fourier transform module 4, and the Fourier transform module 4 is used to perform Fourier transform of the laser self-mixing interference signal after photoelectric conversion, thereby generating a spectrum curve; an absorption cell 2 is installed at the output end of the semiconductor laser 1, the output end of the laser diode 11 is aligned with the absorption cell 2, and a piezoelectric ceramic crystal 3 is installed on one side of the absorption cell 2; the input end of the piezoelectric ceramic crystal 3 is connected to the control module 7, and the control module 7 generates an AC voltage signal to realize the length change of the piezoelectric ceramic crystal 3.

[0022] Specifically, the length change of the piezoelectric ceramic crystal 3 causes the phase change of the reflected light wave, forming a carrier signal of the absorbance of the formaldehyde gas.

[0023] Specifically, the output end of the formaldehyde sampling pump 6 is connected to the input end of the absorption cell 2 , the laser wavelength of the laser diode 11 is in the absorption band of formaldehyde, and the absorption cell 2 is in high transmittance at the laser wavelength of the laser diode 11 .

[0024] More specifically, the axis of the absorption cell 2 is coaxial with the laser light emitted by the laser diode 11 and is perpendicular to the reflection surface of the piezoelectric ceramic crystal 3 .

[0025] The working principle of the utility model is as follows: the length change of the piezoelectric ceramic crystal 3 causes the phase of the reflected light to change periodically, and the period is related to the control signal of the piezoelectric ceramic crystal 3, the laser wavelength, and the performance parameters of the laser, forming a Doppler frequency, and generating a laser self-mixing spectrum line through Fourier transform; the laser light wave is absorbed by the formaldehyde gas in the absorption cell 2, causing the change of the laser self-mixing spectrum line, so the concentration of the formaldehyde gas can be obtained by the change of the laser self-mixing spectrum line before and after sampling.

[0026] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A light feedback formaldehyde detection device, Features: The invention comprises a semiconductor laser, wherein an absorption cell is installed at the output end of the semiconductor laser, and a piezoelectric ceramic crystal is installed at one side of the absorption cell; the semiconductor laser has a built-in photodiode and a laser diode, and the output end of the laser diode is connected to the input end of the photodiode through an optical signal; a Fourier transform module is provided at the output end of the photodiode; a driving module is provided at the input end of the laser diode; a formaldehyde sampling pump is provided at the input end of the absorption cell; a control module is provided at the input end of the piezoelectric ceramic crystal; the output end of the laser diode is connected to the input end of the photodiode through an optical signal, and the photodiode is used for photoelectric conversion of laser self-mixing signals; the laser wavelength of the laser diode is in the absorption band of formaldehyde, and the absorption cell is in high transmittance under the laser wavelength of the laser diode; the output end of the laser diode is aligned with the absorption cell; the axis of the absorption cell is coaxial with the laser emitted by the laser diode and is perpendicular to the reflection surface of the piezoelectric ceramic crystal; the control module generates an AC voltage signal to change the length of the piezoelectric ceramic crystal; and the driving module is used to generate an injection current of the laser diode and change the output laser wavelength.

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