Temperature drift suppression amplification circuit and confocal microscope

Abstract

The utility model relates to a kind of temperature drift suppression amplification circuit and confocal microscope, temperature drift suppression amplification circuit includes: TIA conversion unit, its input end connects the current output end of photoelectric conversion device;Filter following unit, the output end of TIA conversion unit is connected;For amplifying voltage signal and receiving bias compensation, the inverting input end of the first amplification unit is connected the output end of filter following unit, the noninverting input end connects temperature compensation bias unit;The temperature compensation bias unit includes voltage dividing resistor circuit and thermistor in series in the voltage dividing resistor circuit;RCRC active filter, the output end of the first amplification unit is connected.The utility model, reduce the influence of amplifier output with temperature, offset the natural shift of amplifier output voltage with temperature rise, reach the purpose of temperature drift suppression.

Description

Technical Field

[0001] This utility model relates to the field of signal amplification circuit technology, and in particular to a temperature drift suppression amplification circuit and a confocal microscope. Background Technology

[0002] Laser confocal microscopy is a high-precision instrument with extremely high resolution and strong tomographic capability, and it is one of the most widely used tools in the fields of physiology and medicine. It utilizes the principle of conjugate imaging and employs precise pinhole spatial filtering technology to achieve high signal-to-noise ratio imaging of a specified focal plane, greatly filtering out the influence of stray light from the out-of-focus plane.

[0003] For laser confocal microscopy, the stability of the signal amplification circuit directly affects the image output quality. In existing technologies, such as Chinese utility model patent CN119924770A, a weak light signal data acquisition system for a laser confocal eyelid microscope is disclosed. Due to the temperature drift characteristics of circuit components (such as resistors and chips), the amplifier's output voltage shifts when the external temperature changes, leading to instability in the voltage signal at the AD acquisition port. Specifically, this manifests as: differences in background noise between when the device is first turned on and after a period of operation; significant fluctuations in the signal-to-noise ratio of the image at different ambient temperatures (such as 0℃ and 30℃), and even problems such as missing effective signals or increased background noise, severely affecting the image quality output by the client.

[0004] Existing technologies have significant limitations in addressing temperature drift issues: traditional circuits change the DC bias of the output by adjusting the zero-point offset voltage (Vos), but this relies on manual adjustment using a mechanical potentiometer, requires disassembly, and cannot adapt to dynamic temperature changes. Utility Model Content

[0005] The purpose of this invention is to provide a temperature drift suppression amplifier circuit and a confocal microscope, which reduces the influence of temperature on amplifier output and counteracts the natural shift of amplifier output voltage as temperature rises, thereby achieving the purpose of temperature drift suppression.

[0006] To achieve the above-mentioned objectives, this utility model provides a temperature drift suppression amplifier circuit, comprising:

[0007] The TIA conversion unit has its input terminal connected to the current output terminal of the photoelectric conversion device;

[0008] A filter follower unit is connected to the output of the TIA conversion unit;

[0009] A first-stage amplification unit for amplifying voltage signals and receiving bias compensation, wherein the inverting input of the first-stage amplification unit is connected to the output of the filter follower unit, and the non-inverting input is connected to the temperature compensation bias unit.

[0010] The temperature compensation bias unit includes a voltage divider resistor circuit and a thermistor connected in series in the voltage divider resistor circuit.

[0011] The RCRC active filter is connected to the output of the first-stage amplifier unit.

[0012] According to one technical solution of this utility model, the thermistor is a PTC thermistor with a resistance temperature coefficient of 100-500ppm / ℃. As the temperature rises, the resistance increases and the bias node voltage decreases.

[0013] According to one technical solution of this utility model, the thermistor is an NTC thermistor with a resistance temperature coefficient of -200 to -600ppm / ℃. As the temperature rises, the resistance decreases and the bias node voltage decreases.

[0014] According to one technical solution of this utility model, the voltage divider resistor circuit includes at least:

[0015] The first voltage divider branch includes a first resistor and a second resistor that are connected in sequence.

[0016] The second voltage divider branch includes a third resistor and a fourth resistor connected in sequence;

[0017] The first voltage divider branch and the second voltage divider branch are connected in series through a variable resistor and the thermistor. The variable resistor is connected in series with two fixed ends, and the sliding end of the variable resistor is connected to the bias node.

[0018] The first intermediate node is the connection point between the first resistor and the second resistor;

[0019] The second intermediate node is the connection point between the third resistor and the fourth resistor;

[0020] Both the first intermediate node and the second intermediate node are equipped with grounded voltage stabilizing components.

[0021] According to one technical solution of this utility model, the temperature drift suppression amplifier circuit further includes:

[0022] A digital potentiometer is connected in series in the reference voltage input path of the temperature compensation bias unit, and the control terminal of the digital potentiometer is configured with a communication interface.

[0023] According to one technical solution of this utility model, the filter follower unit includes a voltage follower composed of an operational amplifier and an RC low-pass filter.

[0024] According to one technical solution of this utility model, the temperature drift suppression amplifier circuit further includes:

[0025] A secondary amplification unit is connected to the output terminal of the primary amplification unit, and the output terminal of the secondary amplification unit is connected to the RCRC active filter.

[0026] According to one technical solution of this utility model, the temperature drift suppression amplification circuit is directly connected to the host computer; or

[0027] The temperature drift suppression amplifier circuit is electrically connected to the host computer through the MCU control module.

[0028] According to one technical solution of this utility model, the RCRC active filter includes two adjustable resistors, two adjustable capacitors and an amplifier.

[0029] According to one aspect of the present invention, a confocal microscope is provided, comprising a PMT and a temperature drift suppression amplification circuit as described in any of the above technical solutions.

[0030] Compared with the prior art, this utility model has the following advantages:

[0031] According to one aspect of this utility model, by introducing a temperature compensation bias unit, an amplification unit, and a multi-stage filtering circuit into a traditional amplifier circuit structure, effective suppression of circuit temperature drift during photoelectric signal amplification is achieved, significantly improving the stability and consistency of the amplified output, reducing the impact of ambient temperature changes on measurement accuracy, thereby ensuring the accuracy of signal detection and the long-term reliable operation of the system.

[0032] According to one technical solution of this utility model, the temperature drift suppression amplifier circuit is directly connected to the host computer, or communicates with the host computer through the MCU control module, realizing the real-time transmission of signal and parameter adjustment information. Combined with a digital potentiometer with a communication interface, remote and precise programmable adjustment of the bias voltage is realized on the software side. With the temperature drift compensation on the hardware side, the problems of low adjustment accuracy, inconvenient operation, and difficulty in matching compensation curves online of traditional manual potentiometers are solved. Attached Figure Description

[0033] Figure 1 This diagram illustrates the composition of a confocal microscope according to one embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a temperature compensation bias unit according to one embodiment of the present invention.

[0035] Figure 3 This diagram illustrates the connection between a host computer and an MCU according to one embodiment of the present invention.

[0036] Figure 4This diagram schematically illustrates a temperature drift suppression amplifier circuit according to one embodiment of the present invention.

[0037] Figure 5 The diagram illustrates four imaging effects of a confocal microscope. Detailed Implementation

[0038] To more clearly illustrate the embodiments of this utility model or the technical solutions in the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0039] In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" express orientations or positional relationships based on the orientations or positional relationships shown in the relevant drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on the present invention.

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the embodiments of the present invention are not limited to the following embodiments.

[0041] like Figure 1 As shown, this is a confocal microscope in the prior art, which includes four core modules: host computer, MCU, amplifier, and PMT (photomultiplier tube). The PMT is the weak signal acquisition end, which receives the "nW level light energy" of the confocal microscope and other equipment, converts it into a weak current signal, and outputs it to the signal input end of the amplifier. The amplifier receives the weak current signal output by the PMT, adjusts the amplification factor through the amplification control link, and finally outputs the voltage signal Vout.

[0042] The microcontroller unit (MCU) connects the amplifier to the host computer via a hardware interface (such as SPI, I2C, or GPIO).

[0043] Receive the "amplification ratio command" from the host computer and output the amplification ratio control signal to the amplifier;

[0044] The amplifier's operating status is acquired in real time (optional extended functions, such as temperature and voltage feedback), and transmitted back to the host computer.

[0045] The host computer is the core of the confocal microscope system control and algorithm, and it connects the MCU and PMT via a communication bus (such as UART, Ethernet, or USB).

[0046] Send amplification factor control commands (such as "gain ×10" or "gain ×100") to the MCU to indirectly adjust the signal amplification factor of the amplifier;

[0047] Directly output a gain voltage control signal (such as an adjustable negative high voltage from -500V to -1000V) to the PMT to adjust the photoelectric conversion gain of the PMT;

[0048] The voltage signal Vout output by the acquisition amplifier is dynamically adjusted by algorithms (such as overexposure detection and signal-to-noise ratio optimization) to achieve closed-loop optimization of image quality.

[0049] like Figures 2 to 4 As shown, according to one embodiment of the present invention, a temperature drift suppression amplifier circuit of the present invention is connected as follows: Figure 1 The temperature drift suppression amplifier circuit between the amplifier and the PMT shown includes:

[0050] TIA conversion unit 1 has its input connected to the current output of the photoelectric conversion device. TIA conversion unit 1 is a TIA circuit composed of a mixed-signal intermediate frequency receiver U3, with its input connected to the current output of the PMT (the PMT is used to acquire nW-level energy from the confocal front end and convert it into a current signal). TIA conversion unit 1 converts the current signal into a weak voltage signal, with the signal gain typically set to 50KV / A to ensure effective extraction of the nW-level weak energy and provide a stable input for subsequent amplification.

[0051] Among them, the photoelectric conversion device adopts a photomultiplier tube (PMT), whose cathode is grounded, the anode is powered by a high-voltage power supply module, and the current output terminal is led out through a shielded wire and connected to the inverting input terminal of TIA conversion unit 1;

[0052] For example, TIA conversion unit 1 can be ADA8033, OPA657, OPA376, etc.

[0053] Filter follower unit 2 is connected to the output of TIA conversion unit 1. Filter follower unit 2 consists of a voltage follower U9 (which is composed of an operational amplifier) ​​and an RC low-pass filter (such as a 10kΩ resistor and a 12pF capacitor). The input of filter follower unit 2 is connected to the output of TIA conversion unit 1. The voltage follower U9 buffers the signal, preventing subsequent circuits from affecting the load on the TIA unit; the RC low-pass filter performs initial noise reduction on the initial voltage signal.

[0054] A primary amplifier unit 3 is used to amplify voltage signals and receive bias compensation. The inverting input of primary amplifier unit 3 is connected to the output of filter follower unit 2, and the non-inverting input is connected to a temperature compensation bias unit. Primary amplifier unit 3 uses a U4 chip (such as ADA8065, OPA690, etc.). The inverting input is connected to the output of filter follower unit 2 through a 10kΩ resistor (R24), and the non-inverting input is connected to the bias node VOS of the temperature compensation bias unit. The amplification factor of primary amplifier unit 3 is typically set to 10 to 100 times to amplify the filtered signal, while simultaneously receiving bias compensation through the non-inverting input to suppress temperature drift.

[0055] The temperature compensation bias unit includes a voltage divider resistor circuit and a thermistor connected in series in the voltage divider resistor circuit; such as Figure 2 As shown, the temperature compensation bias unit includes a voltage divider resistor circuit (R16, R17, R18, R19, all 10kΩ) and a thermistor.

[0056] RCRC active filter 5 is connected to the output of the first-stage amplifier unit 3.

[0057] In some embodiments of this invention, the thermistor is a PTC thermistor with a resistance temperature coefficient of 100-500ppm / ℃. As the temperature rises, the resistance increases and the bias node voltage decreases.

[0058] As temperature rises, the resistance of the PTC increases linearly with temperature, directly pulling down the bias node voltage.

[0059] As the temperature rises, the resistance of the PTC thermistor increases linearly with the temperature. The change in the resistance of the PTC thermistor can offset the temperature drift caused by the natural rise in amplifier output voltage due to "temperature rise". This achieves "hardware-level real-time temperature drift compensation", which can cope with the interference of slowly changing temperature without complicated intervention and improve the stability of the circuit over a wide temperature range.

[0060] In some embodiments of this utility model, the thermistor is an NTC thermistor with a resistance temperature coefficient of -200 to -600ppm / ℃. As the temperature rises, the resistance decreases, and the bias node voltage decreases.

[0061] Similarly, when the thermistor is an NTC thermistor, the resistance of the NTC thermistor decreases linearly with the temperature as the temperature rises. The bias node voltage can be indirectly adjusted by circuit design (such as changing the NTC connection method) to reduce the bias node voltage.

[0062] For example, a TMP6131DECR thermistor can be used for PTC thermistors, and an NCP18XH103F03RB thermistor can be used for NTC thermistors.

[0063] In some embodiments of this utility model, the voltage divider resistor circuit includes at least:

[0064] The first voltage divider branch includes a first resistor R16 and a second resistor R17 connected in sequence.

[0065] The second voltage divider branch includes a third resistor R18 and a fourth resistor R19 connected in sequence.

[0066] The first voltage divider branch and the second voltage divider branch are connected in series through a variable resistor R20 and a thermistor. The variable resistor R20 is connected in series with two fixed terminals, and the sliding terminal of the variable resistor R20 is connected to the bias node VOS.

[0067] The first intermediate node is the connection point between the first resistor and the second resistor;

[0068] The second intermediate node is the connection point between the third resistor and the fourth resistor;

[0069] Both the first and second intermediate nodes are equipped with grounded voltage stabilizing components.

[0070] The symmetrical configuration of the dual voltage divider branches (including the first voltage divider branch with first resistor R16 and second resistor R17, and the second voltage divider branch with third resistor R18 and fourth resistor R19), combined with the grounded voltage regulator components at the first and second intermediate nodes, constructs a dual-reference voltage regulator architecture. This effectively isolates the interference of input voltage fluctuations on bias adjustment, providing a stable voltage reference for the bias node VOS. Simultaneously, the variable resistor R20 is connected to the bias node VOS with its sliding terminal, forming a voltage divider adjustment link with the series-connected thermistor. The resistance fluctuation of the thermistor with temperature changes is mapped to the bias node voltage through the voltage divider network. Combined with the reference stabilization effect of the voltage regulator components, this improves the accuracy of temperature drift compensation. Furthermore, the combination design of the dual voltage divider branches and the variable resistor broadens the adjustment range of the bias voltage, adapting to the bias requirements of different amplification units. Ultimately, through hardware-level reference stabilization, linear adjustment, and range expansion, effective suppression of temperature drift in the amplification circuit is achieved, improving the stability of the signal amplification reference.

[0071] Furthermore, the first resistor R16, the second resistor R17, the third resistor R18, and the fourth resistor R19 are all protective resistors. By adding protective resistors to the grounding line of the thermistor, the impact of abnormal current on the thermistor is limited. Through the current-limiting effect of the protective resistors (resistance value 1-10kΩ), the maximum grounding current is controlled within the safe range of the thermistor, which helps to prevent ESD events from damaging the thermistor, improves the reliability of the circuit in the industrial environment, and ensures the service life of the product.

[0072] In some embodiments of this utility model, such as Figure 3 As shown, the temperature drift suppression amplifier circuit also includes:

[0073] Digital potentiometer 6 is connected in series in the reference voltage input path of the temperature compensation bias unit, and the control terminal of digital potentiometer 6 is configured with a communication interface.

[0074] By connecting a digital potentiometer 6 in series in the reference voltage input path and configuring SPI / I... 2 The C-type communication interface enables precise adjustment of the bias voltage via external digital signals; replacing the traditional mechanical potentiometer with a digital potentiometer 6 avoids parameter drift caused by mechanical wear; and utilizing external digital signals from the software for assisted control enables hardware and software linkage to adjust temperature drift balance. Before scanning, AD data is collected for threshold scanning, thereby adjusting the digital potentiometer 6 to change the VOS value, thus correcting the temperature drift. This achieves the goal of dynamic temperature drift calibration without disassembly during equipment operation, solving the pain point of traditional potentiometers requiring repeated manual adjustments, shortening factory calibration time, and allowing temperature drift correction to be achieved without disassembly when similar problems occur at the client end.

[0075] Among them, digital potentiometer 6 is a low-temperature drift, high-precision digital potentiometer 6.

[0076] Figure 3 In the middle, the host computer is electrically connected to the MCU, and then connected to a digital potentiometer 6 (made by...). Figure 3 Composed of U21 (TPL0501-100DCNR), it is connected to an amplification unit (composed of...) via digital potentiometer 6. Figure 3 The U22 component (AD8655) is connected to the temperature compensation bias unit. At this time, more precise temperature drift suppression can be achieved by using software, realizing the linkage adjustment of temperature drift balance between hardware and software, which has the advantage of higher precision.

[0077] The resistance adjustment of digital potentiometer 6 is independently controlled by the control signal sent by the external controller through the communication interface, and the resistance adjustment of digital potentiometer 6 is independent of the automatic temperature compensation of the thermistor.

[0078] In some embodiments of this utility model, the temperature drift suppression amplification circuit further includes:

[0079] Secondary amplifier unit 4 is connected to the output of primary amplifier unit 3, and the output of secondary amplifier unit 4 is connected to RCRC active filter 5.

[0080] By adding a secondary amplification unit 4 before the RCRC active filter 5, a secondary gain enhancement is achieved on the output of the primary amplification unit, thereby improving the circuit's ability to amplify extremely weak signals and ensuring signal measurability. Typically, when the primary amplification unit 3 cannot meet the amplification requirements, a secondary amplification unit 4 is needed. For example, if the amplification factor of the primary amplification unit 3 is 30, the secondary amplification unit 4 can be set to 2 times to achieve 60x amplification.

[0081] Furthermore, the secondary amplification unit 4 can also be equipped with an RC filter and then connected to an RCRC active filter 5.

[0082] In some embodiments of this utility model, the temperature drift suppression amplifier circuit is directly connected to the host computer; or

[0083] The temperature drift suppression amplifier circuit is electrically connected to the host computer through the MCU control module.

[0084] The circuit is physically connected directly to the Ethernet interface of the host computer or the UART interface of the MCU, constructing a hardware communication path, ensuring the anti-interference transmission of control signals, and achieving the technical effect of remote real-time adjustment of 6 parameters of the digital potentiometer, so that the client can complete temperature drift calibration without disassembling the device.

[0085] For example, the MCU can be an STM32F103.

[0086] In some embodiments of this utility model, the RCRC active filter 5 includes two adjustable resistors, two adjustable capacitors, and an amplifier.

[0087] Specifically, the RCRC source filter includes a first adjustable resistor R25, a second adjustable resistor R26, a first adjustable capacitor C75, and a second adjustable capacitor C76.

[0088] Wherein, the first end of the first adjustable resistor R25 is connected to the output end of the first-stage amplification unit 3 or the second-stage amplification unit 4, and the second end of the first adjustable resistor R25 is connected to the first end of the first adjustable capacitor C75 and the first end of the second adjustable resistor R26.

[0089] The second terminal of the second adjustable resistor R26 is connected to the first terminal of the second adjustable capacitor C76, and also functions as an amplifier. Figure 4 The input of U12 (ADA8510) is connected; the second terminal of the second adjustable capacitor C76 is grounded; the sharpness and smoothness of the image can be adjusted by adjusting the resistance and capacitance values ​​of the first adjustable resistor R25, the second adjustable resistor R26, the first adjustable capacitor C75, and the second adjustable capacitor C76.

[0090] According to one aspect of this utility model, a confocal microscope is proposed, including a photomultiplier tube (PMT) and a temperature drift suppression amplification circuit as described in any of the above technical solutions. This confocal microscope typically also includes a host computer, an MCU, an amplifier, etc., wherein the PMT refers to a photomultiplier tube.

[0091] like Figure 5 As shown, Figure 5 The diagram includes four renderings (a), (b), (c), and (d). Without using the temperature drift suppression amplifier circuit of this invention, under the same external environmental conditions, the following will occur: Figure 5 (a) Overexposure, Figure 5 (b) Threshold too low or Figure 5 (c) In cases where the threshold is too high, and the temperature drift suppression amplifier circuit of this application is used, under the same external environmental conditions, the following will occur: Figure 5 A clear image in (d).

[0092] The above description is merely an example of a specific solution of this utility model. For any equipment and structures not described in detail, it should be understood that they are implemented using common equipment and methods already available in the field.

[0093] The above description is merely one solution of this utility model and is not intended to limit it. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A temperature drift suppression amplifier circuit, characterized in that, include: TIA conversion unit (1), whose input terminal is connected to the current output terminal of photoelectric conversion device; The filter follower unit (2) is connected to the output terminal of the TIA conversion unit (1); A first-stage amplification unit (3) is used to amplify voltage signals and receive bias compensation. The inverting input terminal of the first-stage amplification unit (3) is connected to the output terminal of the filter follower unit (2), and the non-inverting input terminal is connected to the temperature compensation bias unit. The temperature compensation bias unit includes a voltage divider resistor circuit and a thermistor connected in series in the voltage divider resistor circuit. The RCRC active filter (5) is connected to the output of the first-stage amplifier unit (3).

2. The temperature drift suppression amplifier circuit according to claim 1, characterized in that, The thermistor is a PTC thermistor with a resistance temperature coefficient of 100-500ppm / ℃. As the temperature rises, the resistance increases and the bias node voltage decreases.

3. The temperature drift suppression amplifier circuit according to claim 1, characterized in that, The thermistor is an NTC thermistor with a resistance temperature coefficient of -200 to -600 ppm / ℃. As the temperature rises, the resistance decreases, and the bias node voltage decreases.

4. The temperature drift suppression amplifier circuit according to claim 1, characterized in that, The voltage divider resistor circuit includes at least: The first voltage divider branch includes a first resistor and a second resistor that are connected in sequence. The second voltage divider branch includes a third resistor and a fourth resistor connected in sequence; The first voltage divider branch and the second voltage divider branch are connected in series through a variable resistor and the thermistor. The variable resistor is connected in series with two fixed ends, and the sliding end of the variable resistor is connected to the bias node. The first intermediate node is the connection point between the first resistor and the second resistor; The second intermediate node is the connection point between the third resistor and the fourth resistor; Both the first intermediate node and the second intermediate node are equipped with grounded voltage stabilizing components.

5. The temperature drift suppression amplifier circuit according to claim 4, characterized in that, Also includes: A digital potentiometer (6) is connected in series in the reference voltage input path of the temperature compensation bias unit, and the control terminal of the digital potentiometer (6) is configured with a communication interface.

6. The temperature drift suppression amplifier circuit according to claim 1, characterized in that, The filter follower unit (2) includes a voltage follower composed of an operational amplifier and an RC low-pass filter.

7. The temperature drift suppression amplifier circuit according to claim 1, characterized in that, Also includes: The secondary amplification unit (4) is connected to the output terminal of the primary amplification unit (3), and the output terminal of the secondary amplification unit (4) is connected to the RCRC active filter (5).

8. The temperature drift suppression amplifier circuit according to claim 1, characterized in that, The temperature drift suppression amplifier circuit is directly connected to the host computer; or The temperature drift suppression amplifier circuit is electrically connected to the host computer through the MCU control module.

9. The temperature drift suppression amplifier circuit according to claim 1, characterized in that, The RCRC active filter (5) includes two adjustable resistors, two adjustable capacitors and an amplifier.

10. A confocal microscope, comprising a host computer, an MCU, and a PMT, characterized in that, Also includes: The temperature drift suppression amplifier circuit as described in any one of claims 1 to 9.

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