Micro bolometer thermal sensing device and thermal sensing method thereof

Microthermal radiometer thermal sensing device and thermal sensing method

MICRO BOLOMETER THERMAL SENSING DEVICE AND THERMAL SENSING METHOD THEREOF

The present invention relates to a thermal sensing device, and in particular to a microbolometer thermal sensing device and a thermal sensing method thereof.

Micro-Bolometer thermal sensing circuit has an array composed of multiple Micro-Bolometer pixels, which can be used to measure radiant energy and convert it into a temperature sensor for electrical signal output , but the response will decrease due to, for example, the transmittance of the infrared filter (IR Pass Filter), so the measured signal needs to be amplified to improve the resolution. Due to manufacturing process factors, the pixels of the microbolometer often have different electrical characteristics, such as different resistance values. Therefore, the sensing results provided by some pixels of the microbolometer may be amplified by the amplifier circuit. The amplified signal generated may exceed The dynamic range of subsequent digital-to-analog conversion signals makes it impossible to obtain accurate temperature sensing results, resulting in a decrease in the quality of temperature sensing.

The invention provides a heat sensing device of a microthermal radiometer and a thermal sensing method thereof, which can greatly improve the sensing quality of the microthermal radiometer.

The microthermal radiometer heat sensing device of the present invention includes a heat sensing circuit, an amplifier circuit and a reference voltage generating circuit. The thermal sensing circuit provides the sensing voltage. The positive input terminal of the amplifier circuit is coupled to the heat sensing circuit. The reference voltage generating circuit is coupled to the negative input terminal of the amplifier circuit and provides a reference voltage corresponding to the sensing voltage so that the output voltage of the amplifier circuit falls within a preset range.

In an embodiment of the present invention, the above-mentioned thermal sensing circuit includes a bias circuit, a first resistor and a thermal sensing unit. The bias circuit provides a bias voltage or bias current. The first resistor is coupled between the bias circuit and the positive input terminal of the amplifier circuit. The thermal sensing unit is coupled to the negative input terminal of the amplifier circuit and provides sensing voltage.

In an embodiment of the present invention, the above-mentioned reference voltage generating circuit includes a second resistor and a variable resistor. One end of the second resistor is coupled to the bias circuit. The variable resistor is coupled between the other end of the second resistor and the ground. The common contact point of the second resistor and the variable resistor is coupled to the negative input terminal of the amplifier circuit. The resistance value of the variable resistor is adjusted corresponding to the sensing voltage, and Make the output voltage of the amplifier circuit fall within the preset range.

In one embodiment of the present invention, the above-mentioned bias circuit is a variable current source that provides a variable bias current corresponding to the sensing voltage, so that the output voltage of the amplifier circuit falls within a preset range.

In an embodiment of the present invention, the above-mentioned amplifier circuit adjusts the gain value of the amplifier circuit corresponding to at least one of the sensing voltage and the reference voltage, so that the output voltage of the amplifier circuit falls within a preset range.

In an embodiment of the present invention, the above-mentioned amplifier circuit is a programmable gain amplifier circuit.

In an embodiment of the present invention, the above-mentioned thermal sensing unit is a microbolometer pixel.

The invention also provides a thermal sensing method of a microthermal radiometer thermal sensing device, which includes the following steps. A bias voltage or bias current is provided to the thermal sensing unit of the microbolometer thermal sensing device. An amplifier circuit is provided, a positive input terminal of the amplifier circuit receiving the sensing voltage from the thermal sensing unit. A reference voltage is provided to the negative input terminal of the amplifier circuit corresponding to the sensing voltage, so that the output voltage of the amplifier circuit falls within a preset range.

In one embodiment of the present invention, the thermal sensing method of the microbolometer thermal sensing device includes adjusting the bias current corresponding to the sensing voltage so that the output voltage of the amplifier circuit falls within a preset range.

In an embodiment of the present invention, the thermal sensing method of the microbolometer thermal sensing device includes adjusting the gain value of the amplifier circuit corresponding to at least one of the sensing voltage and the reference voltage so that the output voltage of the amplifier circuit falls within the preset range.

In an embodiment of the present invention, the above-mentioned amplifier circuit is a programmable gain amplifier circuit.

In an embodiment of the present invention, the above-mentioned thermal sensing unit is a microbolometer pixel.

Based on the above, the reference voltage generating circuit of the embodiment of the present invention can provide a reference voltage to the negative input terminal of the amplifier circuit corresponding to the sensing voltage generated by the thermal sensing circuit, so as to appropriately adjust the output voltage of the amplifier circuit to a preset range. This prevents the subsequent circuit from being unable to correctly read the output voltage of the amplifier circuit, thereby effectively improving the sensing quality of the microthermal radiometer thermal sensing device.

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a thermal sensing device of a microbolometer according to an embodiment of the present invention. Please refer to FIG. 1 . The microbolometer thermal sensing device 100 includes a thermal sensing circuit 102, an amplifier circuit A1 and a reference voltage generating circuit 104. The positive and negative input terminals of the amplifier circuit A1 are coupled to the thermal sensing circuit 102 and the reference voltage generating circuit 104 respectively. The thermal sensing circuit 102 is a circuit that can convert the physical change of the sensor into a voltage signal that can be measured. The sensor here is an array composed of microbolometer pixels and microbolometer reference pixels. The physical changes of the detector determine the size of the changes in physical quantities based on the energy of external thermal radiation. The physical quantities are sampled and converted through corresponding circuits into voltage signals that can be measured. The thermal sensing circuit 102 can convert the sensed radiant energy into electrical energy to generate a sensing voltage, and transmit the sensing voltage to the positive input end of the amplifier circuit A1. The positive input voltage of the amplifier circuit A1 minus the negative input voltage of the amplifier circuit A1 multiplied by the gain value of the amplifier circuit A1 is the output voltage VO of the amplifier circuit A1. The gain value of the amplifier circuit A1 is determined by the specifications of the amplifier circuit A1. For example, the amplifier circuit A1 may have a fixed gain value, or may be a programmable gain amplifier with a programmable gain value. In addition, in some embodiments, the output terminal of the amplifier circuit A1 may also have a capacitor connected between the output terminal of the amplifier circuit A1 and the ground, but it is not limited to this.

The reference voltage generating circuit 104 can be, for example, a digital-to-analog conversion circuit, which can provide a reference voltage to the negative input end of the amplifier circuit A1 corresponding to the sensing voltage. For example, it can provide a reference voltage that is similar to the voltage value of the sensing voltage according to the sensing voltage. So that the output voltage VO of the amplifier circuit A1 falls within the preset range. The preset range may be the input dynamic range of the subsequent stage circuit, for example, the output voltage VO of the amplifier circuit A1 falls within the input dynamic range of the analog-to-digital conversion circuit 106 . This ensures that the analog-to-digital conversion circuit 106 obtains accurate sensing results, and effectively improves the sensing quality of the microbolometer thermal sensing device 100 . For example, the preset range of the output voltage VO of the amplifier circuit A1 is the input voltage of the subsequent-stage analog-to-digital conversion circuit 106. It is assumed that the dynamic preset range of the input voltage of the subsequent-stage analog-to-digital conversion circuit 106 is 0 to 5 volts. , the gain of the amplifier circuit A1 is 100 times, the output sensing voltage of the thermal sensing circuit 102 is 2 volts, the output reference voltage of the reference voltage generating circuit 104 can be adjusted to 1.975 volts, so the output voltage VO of the amplifier circuit A1 is 2.5 volts , that is, the input voltage of the analog-to-digital conversion circuit 106 of the subsequent stage is 2.5 volts, which falls within the dynamic preset range of the input voltage of the analog-to-digital conversion circuit 106 of the subsequent stage, which is 0~5 volts.

In some embodiments, in addition to adjusting the output voltage VO of the amplifier circuit A1 by providing a reference voltage corresponding to the sensing voltage through the reference voltage generating circuit 104, the output voltage VO of the amplifier circuit A1 can also be adjusted by changing the gain of the amplifier circuit A1. For example, the amplifier circuit A1 may be a programmable gain amplifier circuit, and the amplifier circuit A1 may adjust the gain of the amplifier circuit A1 according to at least one of the sensing voltage provided by the thermal sensing circuit 102 and the reference voltage provided by the reference voltage generating circuit 104 . The gain value makes the output voltage VO of the amplifier circuit A1 fall within the preset range. For example, the preset range of the output voltage VO of the amplifier circuit A1 is the input voltage of the subsequent analog-to-digital conversion circuit 106. It is assumed that the dynamic preset range of the input voltage of the subsequent analog-to-digital conversion circuit 106 is 0 to 5 volts. , the output sensing voltage of the thermal sensing circuit 102 is 2 volts, the output reference voltage of the reference voltage generating circuit 104 is 1.975 volts, and the programmable gain of the adjustable amplifier circuit A1 is set to 100 times, then the output voltage of the amplifier circuit A1 VO is 2.5 volts, that is, the input voltage of the subsequent analog-to-digital conversion circuit 106 is 2.5 volts, which falls within the preset range of the output voltage VO of the amplifier circuit A1.

FIG. 2 is a schematic diagram of a thermal sensing device of a microbolometer according to another embodiment of the present invention. Furthermore, the implementation of the thermal sensing circuit 102 may be as shown in FIG. 2 , including a bias circuit 202, a resistor R1 and a thermal sensing unit 204. The resistor R1 is coupled between the bias circuit 202 and the thermal sensing unit 204. , the common contact point of the resistor R1 and the thermal sensing unit 204 is coupled to the positive input terminal of the amplifier circuit A1. The bias circuit 202 may be, for example, a bias voltage source or a bias current source, providing a bias voltage or bias current to the thermal sensing unit 204 . In some embodiments, the resistor R1 may be implemented as a variable resistor to adjust the bias current as required. The thermal sensing unit 204 may provide a sensing voltage to the positive input end of the amplifier circuit A1. The thermal sensing unit 204 may be, for example, a microbolometer pixel, but is not limited thereto.

In some embodiments, the bias circuit 202 can also be implemented as a variable current source. The bias circuit 202 can provide a variable bias current corresponding to the sensing voltage generated by the thermal sensing circuit 102 to change the sensing voltage generated by the thermal sensing circuit 102. The sensing voltage makes the sensing voltage close to the reference voltage of the negative input terminal of the amplifier circuit A1, thereby causing the output voltage VO of the amplifier circuit A1 to fall within a preset range.

FIG. 3 is a schematic diagram of a thermal sensing device of a microbolometer according to another embodiment of the present invention. In this embodiment, the reference voltage generating circuit 104 may include a resistor R2 and a variable resistor R3. The resistor R2 and the variable resistor R3 are connected in series between the bias circuit 202 and the ground. The common contact point of the resistor R2 and the variable resistor R3 is Coupled to the negative input terminal of amplifier circuit A1. In some embodiments, the resistor R2 can also be implemented as a variable resistor. In this case, when the resistance values of the resistor R2 and the resistor R1 are different, the resistor R2 can be adjusted to make the resistor R2 closer to the resistor R1. In this embodiment, the resistance R2 can be, for example, close to or equal to the resistance R1 . The resistance value of the variable resistor R3 can be adjusted corresponding to the sensing voltage generated by the thermal sensing circuit 102 . For example, the resistance value of the variable resistor R3 can be made close to Or equal to the resistance value of the thermal sensing unit 204, so that the voltages of the negative input terminal and the positive input terminal of the amplifier circuit A1 are close to each other, so that the output voltage VO of the amplifier circuit A1 falls within the preset range.

For example, assuming that the initial resistance value of the thermal sensing unit 204 is 5K ohms, and the resistor R1 in the thermal sensing circuit 102 is set to 10K ohms according to the specifications of the thermal sensing unit 204, the resistance value of the resistor R2 can be set first. The resistance value of the resistor R1 is the same as 10K ohms, and the resistance value of the variable resistor R3 is adjusted to be the same as the initial resistance value of the thermal sensing unit 204 to 5K ohms. The resistance value relationship between the resistance value of the resistor R2 and the resistance value of the variable resistor R3, and the resistance value relationship between the resistance value of the resistor R1 and the initial resistance value of the thermal sensing unit 204 are the same. That is to say, the bias output voltage of the resistor R1 and the thermal sensing unit 204 is made the same as the bias output voltage of the resistor R2 and the variable resistor R3, so that the voltages of the negative input terminal and the positive input terminal of the amplifier circuit A1 are close to each other. And achieve the goal of circuit parameter setting.

In addition, assuming that the preset range of the output voltage VO of the amplifier circuit A1 is 2 volts to 3 volts, the gain of the amplifier circuit A1 is 100 times, and the output voltage of the bias circuit 202 is 3 volts, then the resistor R1 and the thermal sensing unit 204 The bias output voltage is 1.67 volts; resistor R2 has the same resistance value as resistor R1, 10K ohms. If the resistance value of the variable resistor R3 is adjusted to 4.91K ohms, the bias output voltage of the resistor R2 and the variable resistor R3 is 1.65 volts, and the output voltage VO of the amplifier circuit A1 is 2.01 volts. If the resistance value of variable resistor R3 is adjusted to 4.87K ohms, the bias output voltage of resistor R2 and variable resistor R3 is 1.64 volts, and the output voltage VO of amplifier circuit A1 is 2.91 volts; The bias output voltages of 1.65 volts and 1.64 volts are both close to the bias output voltage of the resistor R1 and the thermal sensing unit 204 of 1.67 volts. If the resistance value of the variable resistor R3 is adjusted to 4.87K ohms to 4.91K ohms, the output voltage VO of the amplifier circuit A1 is in the preset range of 2 volts to 3 volts.

FIG. 4 is a flow chart of a thermal sensing method of a microbolometer thermal sensing device according to an embodiment of the present invention. Please refer to FIG. 4 . It can be seen from the above embodiments that the thermal sensing method of the microbolometer thermal sensing device may include at least the following steps. First, a bias voltage or bias current is provided to the thermal sensing unit of the microbolometer thermal sensing device (step S402), where the thermal sensing unit may be, for example, a microbolometer pixel, but is not limited thereto. Next, an amplifier circuit is provided, the positive input terminal of the amplifier circuit receives the sensing voltage from the thermal sensing unit (step S404). Then, a reference voltage corresponding to the sensing voltage of the thermal sensing unit is provided to the negative input terminal of the amplifier circuit, so that the output voltage of the amplifier circuit falls within a preset range (step S406). For example, the reference voltage can be close to the sensing voltage. , to make the output voltage of the amplifier circuit fall within the preset range. In some embodiments, the gain value of the amplifier circuit can also be adjusted corresponding to at least one of the sensing voltage and the reference voltage, so that the output voltage of the amplifier circuit falls within a preset range, where the amplifier circuit can be, for example, a programmable gain amplifier. circuit. In addition, in other embodiments, the bias current provided to the sensing current can also be adjusted corresponding to the sensing voltage of the thermal sensing unit, thereby adjusting the sensing voltage so that the output voltage of the amplifier circuit falls within a preset range.

FIG. 5 is a flow chart of a thermal sensing method of a microbolometer thermal sensing device according to another embodiment of the present invention. Specifically, after step S406, the output voltage of the amplifier circuit can be measured first through the analog-to-digital conversion circuit (step S502), and then it is determined whether the output voltage of the amplifier circuit falls within the preset range (step S504). If When the output voltage of the amplifier circuit falls within the preset range, the end step is entered. If the output voltage of the amplifier circuit does not fall within the preset range, the reference voltage is adjusted (step S506), and returns to step S406 to provide the adjusted reference voltage to the negative input terminal of the amplifier circuit.

In summary, the reference voltage generating circuit of the embodiment of the present invention can provide a reference voltage to the negative input terminal of the amplifier circuit corresponding to the sensing voltage generated by the thermal sensing circuit, so as to appropriately adjust the output voltage of the amplifier circuit to a preset range. This prevents the subsequent stage circuit from being unable to correctly read the output voltage of the amplifier circuit, thereby effectively improving the sensing quality of the microbolometer thermal sensing device.

<p>100: Microbolometer thermal sensing device 102: Thermal sensing circuit 104: Reference voltage generation circuit 106: Analog-to-digital conversion circuit A1: Amplifier circuit VO: output voltage 202: Bias circuit R1: Resistor 204: Thermal sensing unit R2: Resistor R3: variable resistor S402~S406, S502~S506: Thermal sensing method steps of the microbolometer thermal sensing device </p>

Figure 1 is a schematic diagram of a thermal sensing device of a microbolometer according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a thermal sensing device of a microbolometer according to another embodiment of the present invention. FIG. 3 is a schematic diagram of a thermal sensing device of a microbolometer according to another embodiment of the present invention. Figure 4 is a flow chart of a thermal sensing method of a microbolometer thermal sensing device according to an embodiment of the present invention. FIG. 5 is a flow chart of a thermal sensing method of a microbolometer thermal sensing device according to another embodiment of the present invention.