An analog-to-digital conversion circuit for CCD signal acquisition

Abstract

The present invention discloses an analog-to-digital conversion circuit for CCD signal acquisition, which includes a single-ended to differential operational amplifier circuit, an analog-to-digital converter, a reference power supply circuit, and a reverse drive circuit. Among them, the CCD analog signal amplification circuit and the analog-to-digital converter are placed on the same circuit board, and the distance between the two is minimized to reduce the possibility of being interfered. A high-speed analog-to-digital converter is adopted, and both the digital control quantity and the conversion result are terminated in a differential manner. The single-ended to differential operational amplifier circuit is used to convert the output signal of the CCD detector from single-ended to differential mode. The reference power supply circuit is used to provide a reference reference voltage for the analog-to-digital converter, and the analog electrical signal output by the CCD is converted into a digital quantity with a precision of 16 bits, which can match the change frequency of the analog electrical signal output by the linear array CCD detector.

Description

Technical Field

[0001] The present invention relates to the technical field of spectral analysis, and particularly relates to an analog-to-digital conversion circuit for CCD signal acquisition, which is used for spectral analysis instrument equipment. Background Art

[0002] The direct-reading spectrometer for full spectrum is a general equipment for detecting the chemical components of metal materials. Its working principle is that the excitation source generates high voltage, and discharges the test sample through the electrode under the protection of inert gas to generate plasma spectrum. The front optical path transmits the characteristic light to the optical system and the optical system performs spectral splitting. The acquisition system acquires data signals, and the software processes the data to obtain the required results.

[0003] The spectral signals of the direct-reading spectrometer are usually collected by using a photomultiplier tube (PMT) or a charge-coupled device (CCD, CMOS). The acquisition method of the photomultiplier tube can only match one photomultiplier tube for one element, and it is impossible to achieve full-spectrum acquisition due to the limitation of the space of the optical system. To meet the needs of users for samples with different matrices, most spectrometer manufacturers have launched CCD and CMOS optical signal acquisition devices, which convert the collected image analog signals into digital signals, and obtain the required analysis results through software processing, realizing full-spectrum signal acquisition and meeting the needs of different users. Summary of the Invention

[0004] In view of this, the present invention provides a CCD signal analog-to-digital conversion circuit that can match the change frequency of the analog electrical signal output by the linear array CCD detector, and has strong anti-interference ability and high precision.

[0005] The analog-to-digital conversion circuit for CCD signal acquisition provided by the present disclosure includes:

[0006] An amplification circuit for amplifying the analog signal output by the CCD detector;

[0007] An analog-to-digital conversion device connected to the output end of the amplification circuit for performing analog-to-digital conversion on the output analog signal;

[0008] A reference power supply circuit for providing a reference reference voltage for the analog-to-digital conversion device;

[0009] A reverse drive circuit for driving and controlling the exposure of the detector;

[0010] The analog-to-digital conversion device and the reverse drive circuit interact with the outside through digital ports, including outputting the result of analog-to-digital conversion and receiving control signals;

[0011] Wherein:

[0012] Between the detector signal output pin and the input end of the amplifier circuit, and between the output end of the amplifier circuit and the input end of the analog-to-digital conversion device, short-distance circuit hard connections are adopted, and the amplifier circuit and the analog-to-digital conversion device are placed on the same circuit board.

[0013] Furthermore, an analog-to-digital conversion device with a high sampling rate and both input and output signals in low-voltage differential mode is adopted;

[0014] The amplifier circuit adopts a high-speed single-ended to differential operational amplifier circuit, which is used to convert the output signal of the CCD detector from single-ended to differential mode to adapt to the differential input end of the high-speed analog-to-digital conversion device.

[0015] Furthermore, the sampling rate adopted by the analog-to-digital conversion device is at most 5 MHz.

[0016] Furthermore, the reference power supply circuit uses an external reference power supply to provide a reference voltage reference for the analog-to-digital conversion device, and after signal and reference voltage matching, an analog-to-digital conversion accuracy of 16 bits is achieved.

[0017] Furthermore, in the reverse drive circuit, the CCD drive signal is reversed by a digital inverter and introduced into the control end of the CCD detector through circuit board traces and straight plug-ins to provide a control path for driving the exposure process of the CCD detector.

[0018] Furthermore, the circuit further includes:

[0019] An additional analog input port for transmitting the analog signal output by the detector through a coaxial cable;

[0020] And / or an additional CCD drive signal port for transmitting a digital drive signal to the reverse drive circuit.

[0021] Compared with the prior art, the beneficial effects of the present disclosure are:

[0022] ① In view of the characteristic that the output signal of the CCD detector is a low-voltage analog signal, the CCD analog signal amplifier circuit and the analog-to-digital conversion device are placed on the same circuit board, and the distance between the two is minimized as much as possible, realizing the minimization of the wiring distance of small analog signals, and effectively reducing the probability of the CCD output signal being interfered and attenuated in a device with an electric spark as the light source;

[0023] ② The digital quantities input and output on the circuit board are transmitted in differential mode, effectively improving the ability to suppress common-mode interference during the transmission of electrical signals;

[0024] ③ The reference power supply circuit is used to provide a reference reference voltage for the analog-to-digital converter, and the analog electrical signal output by the CCD is converted into a digital quantity with an accuracy of 16 bits;

[0025] ④ The circuit that retains the coaxial cable soft connection between the analog signal and the analog-to-digital converter and the separate drive adapter terminals can be matched with the data processing circuit that has its own analog-to-digital converter for use. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the circuit structure according to an exemplary embodiment of the present disclosure. Detailed Embodiments

[0027] The present invention will be described in detail below with reference to the accompanying drawings and by way of examples.

[0028] The present invention provides an analog-to-digital conversion circuit for CCD signal acquisition. The schematic diagram of the exemplary embodiment structure is as Figure 1 shown and includes:

[0029] An amplification circuit for amplifying the analog signal output by the CCD detector;

[0030] An analog-to-digital converter connected to the output end of the amplification circuit for performing analog-to-digital conversion on the output analog signal;

[0031] A reference power supply circuit for providing a reference reference voltage for the analog-to-digital converter;

[0032] A reverse drive circuit for driving and controlling the exposure of the detector;

[0033] Among them, both the analog-to-digital converter and the reverse drive circuit interact with the outside through digital ports, output the results of analog-to-digital conversion, and receive control signals, etc.

[0034] The main features of this circuit are as follows:

[0035] 1. Overall circuit board structure design:

[0036] Currently, the acquisition method adopted by the linear array image detectors (CCD or CMOS) used in existing direct-reading spectrometers is mostly the method of connecting the analog signal end of the detector and the analog-to-digital conversion circuit part by a soft wire, and the distance between the two parts sometimes exceeds 50 cm. However, in fact, since the signal output by the CCD detector is a low-voltage analog signal, it is easily interfered with in equipment using an electric spark as the light source. Therefore, in the present disclosure, both the signal output pins of the CCD detector and the input end of the subsequent circuit, as well as between the amplified analog signal and the analog-to-digital converter, adopt a short-distance hard connection method, and the length of the hard connection path does not exceed 5 cm.

[0037] Thus, the amplification circuit of the CCD analog signal and the analog-to-digital converter can be placed on the same circuit board, and the distance between the two is minimized as much as possible to reduce the possibility of being interfered with and attenuated. One set of CCD analog-to-digital conversion circuits corresponds to one CCD detector.

[0038] 2. Differential conversion of CCD analog signals: To effectively improve the ability to suppress common-mode interference during the transmission of electrical signals, an analog-to-digital converter with both input and output signals in low-voltage differential (LVDS) mode and a high sampling rate (up to 5 MHz) is preferably used to complete the analog-to-digital conversion process of CCD signals.

[0039] Correspondingly, the amplifier circuit is also preferably a high-speed single-ended-to-differential operational amplifier circuit, which converts the single-ended voltage signal output by the CCD into a differential signal to adapt to the differential input terminal of the high-speed analog-to-digital converter.

[0040] 3. Reference power supply circuit: An external reference power supply is preferably used to provide a reference voltage reference for the analog-to-digital converter. A follower circuit is composed of an external precision operational amplifier, and the load capacity of the reference voltage is enhanced through the follower circuit. The analog electrical signal output by the CCD is converted into a digital quantity with 16-bit precision to match the change frequency of the analog electrical signal output by the linear array CCD detector.

[0041] 4. Digital signal interface design: According to the usage requirements of the high-speed analog-to-digital converter, the signals at the control end and the digital quantity output end are in differential mode. Considering the signal characteristics, differential traces are used for the traces from the control pins and digital quantity output pins of the analog-to-digital converter to the input and output terminals of the circuit board.

[0042] 5. Transmission of CCD drive signals: The CCD drive signals are inverted through a digital inverter and introduced to the control end of the CCD detector through the traces on the circuit board, providing a control path for driving the exposure process of the CCD detector.

[0043] 6. Additional functions: As a preferred solution, a coaxial cable input terminal and an independent connector for the CCD drive signal control end are designed on the circuit board, enabling this circuit board to be used in the mode of transmitting analog signals through coaxial cables. It can be matched with a data processing circuit with its own analog-to-digital converter.

[0044] In summary, the above are only the preferred embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An analog-to-digital conversion circuit for CCD signal acquisition, characterized in that, Including: An amplifier circuit for amplifying the analog signal output by the CCD detector; An analog-to-digital conversion device connected to the output end of the amplifier circuit for performing analog-to-digital conversion on the output analog signal thereof; A reference power supply circuit for providing a reference reference voltage for the analog-to-digital conversion device; A reverse drive circuit for driving and controlling the exposure of the detector; The analog-to-digital conversion device and the reverse drive circuit interact with the outside through digital ports, including outputting the result of analog-to-digital conversion and receiving control signals; Wherein: Between the detector signal output pin and the input end of the amplifier circuit, and between the output end of the amplifier circuit and the analog-to-digital conversion device, short-distance circuit hard connections are adopted, and the lengths of the hard connection paths do not exceed 5 cm. The amplifier circuit and the analog-to-digital conversion device are placed on the same circuit board; The reference power supply circuit uses an external reference power supply to provide a reference voltage reference for the analog-to-digital conversion device, and after signal and reference voltage matching, an analog-to-digital conversion accuracy of 16 bits is achieved.

2. The analog-to-digital conversion circuit according to claim 1, characterized in that, An analog-to-digital conversion device with a high sampling rate and both input and output signals in a low-voltage differential mode is adopted; The amplifier circuit adopts a high-speed single-ended to differential operational amplifier circuit for converting the output signal of the CCD detector from single-ended to differential mode.

3. The analog-to-digital conversion circuit according to claim 2, characterized in that, The sampling rate adopted by the analog-to-digital conversion device is at most 5 MHz.

4. The analog-to-digital conversion circuit according to claim 1, characterized in that, In the reverse drive circuit, the CCD drive signal is reversed by a digital inverter and introduced into the control end of the CCD detector through circuit board traces and straight plug-ins to provide a control path for driving the exposure process of the CCD detector.

5. The analog-to-digital conversion circuit according to claim 1, characterized in that, It also includes: An additional analog input port for transmitting the analog signal output by the detector through a coaxial cable; And / or an additional CCD drive signal port for transmitting a digital drive signal to the reverse drive circuit.

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