TWI395934B - UV light detector - Google Patents

Description

Ultraviolet detector

The present invention relates to a photodetector, and more particularly to an ultraviolet photodetector.

Although today's technology is developed and brings convenience to modern people, the pursuit of technological advancement has also caused damage to the global environment. For example, the ozone layer in the atmosphere has been damaged by some CFCs. Once there is a hole in the ozone layer, some of the ultraviolet light from the sun will directly hit the earth's surface, which will harm the creatures on the earth.

Ultraviolet light is very harmful to the human body. If the human body is exposed to ultraviolet light for a long time, the risk of skin cancer, dermatitis, and eye diseases such as cataracts, retina and macular degeneration will increase. Therefore, ultraviolet light detectors for detecting the presence and intensity of ultraviolet light have gradually gained attention.

The conventional ultraviolet light detector includes a vacuum tube, a cathode and an anode respectively disposed at two ends of the vacuum tube, an electron excitation material coated on the cathode, and an inert gas sealed in the vacuum tube, wherein the vacuum tube is made of quartz glass. When the UV detector operates, a large electric field is applied between the cathode and the anode.

When ultraviolet light is irradiated onto the electron-exciting material on the cathode, a photoelectric effect occurs, and the electron-exciting material generates photoelectrons. Since a large electric field is applied between the cathode and the anode, photoelectrons are attracted by the anode and move toward the anode.

The photoelectrons collide with the inert gas during the movement, dissociating the gas molecules in the inert gas to generate ions and electrons. These ions and electrons collide with the inert gas again, so that a large amount of ions and electrons are generated in the vacuum tube, thereby forming a photocurrent between the cathode and the anode. The intensity of the ultraviolet light can be calculated by measuring the current value of the photocurrent.

However, the conventional ultraviolet light detector is quite bulky, and the vacuum tube is easily broken, so that the conventional ultraviolet light detector is quite inconvenient to carry. Therefore, how to develop a portable ultraviolet detector is a subject worth exploring.

The main object of the present invention is to provide an ultraviolet light detector which has the advantages of small size and portability.

The invention provides an ultraviolet light detector, which comprises a surface acoustic wave oscillator (SAW oscillator), a voltage control oscillator (VCO), a mixer, a phase lock. Phase locked loop (PLL), a type of analog to digital converter, and a processing unit. The surface acoustic wave oscillator can receive an ultraviolet light and output a first frequency signal according to the energy of the ultraviolet light. The voltage controlled oscillator can output a second frequency signal. The mixer can mix the first frequency signal with the second frequency signal to generate a mixed signal. The phase-locked loop converts the mixed signal into a voltage analog signal. An analog-to-digital converter converts a voltage analog signal into a digital signal. The processing unit can calculate an energy value of the ultraviolet light according to the digital signal.

The ultraviolet light detector of the present invention utilizes a surface acoustic wave element to be subjected to ultraviolet light to generate a change in frequency, thereby detecting ultraviolet light, and transmitting the voltage controlled oscillator, the mixer, the phase locked loop, and the analog logarithmic bit. Electronic components such as converters and processing units to process signals. Compared with the prior art, the ultraviolet light detector of the present invention has the advantages of small volume, portability, and difficulty in cracking.

The above described features and advantages of the present invention will be more apparent from the following description.

1 is a block diagram of an ultraviolet light detector according to an embodiment of the present invention. Referring to FIG. 1 , the ultraviolet detector 100 includes a surface acoustic wave oscillator 110 , a voltage controlled oscillator 120 , a mixer 130 , a phase locked loop 140 , a type of comparison digital converter 150 , and a processing unit 160 . The surface acoustic wave oscillator 110 and the voltage controlled oscillator 120 are electrically connected to the mixer 130, and the phase locked loop 140 and the analog-to-digital converter 150 are electrically connected between the mixer 130 and the processing unit 160. .

The surface acoustic wave oscillator 110 includes a surface acoustic wave element 200, two match networks 112a, 112b and an amplifier 114, wherein the surface acoustic wave element 200 includes a pair of electrodes 210a, 210b. The matching circuits 112a, 112b are electrically connected to the electrodes 210a, 210b, respectively, and the amplifier 114 is electrically connected to the matching circuits 112a, 112b, wherein the amplifier 114 is a Low Noise Amplifier (LNA). The surface acoustic wave oscillator 110 can stably output a frequency signal through the matching circuits 112a, 112b and the amplifier 114.

The ultraviolet light detector 100 of the present invention detects the ultraviolet light U by utilizing the principle that the surface acoustic wave frequency is changed by the intensity of the ultraviolet light. In detail, when the ultraviolet light U is irradiated to the surface acoustic wave element 200, the surface acoustic wave element 200 receives the ultraviolet light U, and the frequency signal output by the surface acoustic wave oscillator 110 is affected by the energy of the ultraviolet light U. change.

For example, the higher the energy of the ultraviolet light U, the greater the frequency variation of the frequency signal. Therefore, the surface acoustic wave oscillator 110 changes the frequency of the frequency signal according to the energy of the ultraviolet light U, and then outputs the first frequency signal, wherein the frequency of the first frequency signal is between 102 MHz and 113 MHz, for example, the frequency of the first frequency signal. Can be 107MHz.

2 is a top plan view of the surface acoustic wave element of FIG. 1. Please refer to Figure 1 and Figure 2. The surface acoustic wave element 200 further includes a piezoelectric substrate 220, and the electrodes 210a, 210b are disposed on the piezoelectric substrate 220, wherein the electrodes 210a, 210b do not overlap each other. In the present embodiment, the shapes of the electrodes 210a, 210b are substantially identical to each other, and the areas of the two are substantially equal to each other. In addition, the electrodes 210a and 210b are all finger electrodes, and the electrodes 210a and 210b are made of metal.

The piezoelectric substrate 220 includes a substrate 222 and a piezoelectric film 224 disposed on the substrate 222. The material of the piezoelectric film 224 is, for example, zinc oxide (ZnO) or other piezoelectric material capable of absorbing ultraviolet light U, and the material of the substrate 222 may be LiNdO ₃ . When the electrode 210a is supplied with an alternating current, the piezoelectric film 224 located in the vicinity of the electrode 210a oscillates to generate a surface acoustic wave. When the surface acoustic wave is transmitted to the electrode 210b, the piezoelectric film 224 located in the vicinity of the electrode 210b also oscillates, and the surface acoustic wave oscillator 110 outputs a frequency signal.

Since the piezoelectric film 224 is made of zinc oxide, the piezoelectric film 224 can absorb ultraviolet light U having a wavelength of 390 nm or less. When the piezoelectric film 224 absorbs the ultraviolet light U, the piezoelectric film 224 is excited by the ultraviolet light U to generate an electron hole pair, resulting in an increase in the conductivity of the piezoelectric film 224 and a change in the wave velocity of the surface acoustic wave. Thus, the frequency of the frequency signal also changes, and the surface acoustic wave oscillator 110 can output the first frequency signal.

Referring again to FIG. 1, the voltage controlled oscillator 120 can output a second frequency signal and can adjust the frequency of the second frequency signal, wherein the frequency of the second frequency signal is between 102 MHz and 113 MHz. In the present embodiment, both the surface acoustic wave oscillator 110 and the voltage controlled oscillator 120 may adopt an oscillation circuit in the form of a Cobbe, and the transistors used in the circuit architecture may be a transistor of the type BFR505.

The mixer 130 receives the first frequency signal and the second frequency signal, and can mix the first frequency signal with the second frequency signal to generate a mixed signal, wherein the frequency of the mixed signal is between 1HZ and 10MHZ. between. Specifically, when the first frequency signal is mixed with the second frequency signal, the mixer 130 subtracts the frequency of both the first frequency signal and the second frequency signal. Therefore, the frequency of the mixed signal can be equal to the difference between the frequencies of the first frequency signal and the second frequency signal.

In view of the above, the voltage controlled oscillator 120 is used as a local oscillator (LO), and the second frequency signal is used as a reference frequency signal. Therefore, the frequency of the mixed signal can represent the frequency signal output by the surface acoustic wave oscillator 110 and the amount of fluctuation of the frequency. Specifically, when the surface acoustic wave oscillator 110 is irradiated with the ultraviolet light U, the frequency of the frequency signal can be transmitted through the frequency of the mixed signal.

The voltage controlled oscillator 120 can adjust the frequency range of the second frequency signal to ±5 MHz, so that the frequency of the second frequency signal is close to the first frequency signal, for example, when the frequency of the first frequency signal is about 107 MHz, the second frequency The frequency of the signal can be adjusted to 108 MHz to approximate the frequency of the first frequency signal. This can reduce the frequency of the mixed signal, which is conducive to the subsequent work.

The phase-locked loop 140 can perform frequency-to-voltage conversion on the signal and directly output a voltage analog signal. The model of the phase-locked loop 140 is, for example, the LM565. After the mixer 130 outputs the mixed signal, the phase locked loop 140 receives the mixed signal and converts the mixed signal into a voltage analog signal. Thereafter, the phase locked loop 140 outputs the voltage analog signal to the digital to analog converter 150.

The ultraviolet light detector 100 can further include a low frequency amplifier 170. The low frequency amplifier 170 is electrically connected between the mixer 130 and the phase locked loop 140 and directly receives the mixing signal from the mixer 130. The low frequency amplifier 170 can amplify low frequency components in the mixed signal to relatively reduce high frequency components. For example, the mixer 130 can reduce the frequency of the mixed signal to a level of 200 kHz to 1 MHz.

After the mixed signal is converted into the voltage analog signal, the analog-to-digital converter 150 receives the voltage analog signal and converts the voltage analog signal into a digital signal, wherein the analog-to-digital converter 150 is, for example, an ADC0804. After the digital signal is generated, the analog-to-digital converter 150 outputs the digital signal to the processing unit 160, and the processing unit 160 can calculate the energy value of the ultraviolet light U based on the digital signal, which is, for example, power.

In the above, the processing unit 160 can be a single chip, which is, for example, a programmable system-on-chip. The processing unit 160 stores a program for calculating the energy value of the ultraviolet light U, and the program can be edited by using a programming language (for example, C language) to correct the energy value of the ultraviolet light U to make the calculation result more accurate.

In addition, the ultraviolet light detector 100 may further include a differential amplifier 180. The differential amplifier 180 is electrically connected between the phase locked loop 140 and the analog-to-digital converter 150, wherein the differential amplifier 180 can be of the type μA741. Before the voltage analog signal conversion, the differential amplifier 180 can receive and amplify the voltage analog signal, and input the amplified voltage analog signal to the analog to digital converter 150.

The ultraviolet light detector 100 may further include a display unit 190, wherein the display unit 190 is electrically connected to the processing unit 160 and can display the energy value of the ultraviolet light U, such as the power of the ultraviolet light U. In detail, after the processing unit 160 calculates the energy value of the ultraviolet light U, the processing unit 160 instructs the display unit 190 to display the energy value of the ultraviolet light U according to the electrical signal. In addition, the display unit 190 can be a display such as a television screen or a computer screen.

In summary, the ultraviolet light detector of the present invention utilizes the principle of surface acoustic waves to detect ultraviolet light. Therefore, the present invention can not only detect the presence of ultraviolet light, but also accurately determine the energy value (for example, power) of the ultraviolet light by the frequency of the mixed signal.

Secondly, the ultraviolet light detector of the present invention processes signals through electronic components such as a mixer, a phase-locked loop, an analog-to-digital converter, and a processing unit, and the electronic components can be integrated into one circuit board. Therefore, compared with the conventional ultraviolet light detector, the ultraviolet light detector of the present invention has the advantages of small volume, portability, and difficulty in cracking.

Furthermore, the present invention utilizes a phase-locked loop to directly convert a mixed signal into a voltage analog signal, so that the first frequency signal does not have to go through a series of complicated and complicated processes of amplification, frequency reduction, and frequency division, and the present invention does not need to A frequency to voltage IC is used. Therefore, the present invention has the advantage of being fast in operation in detecting ultraviolet light.

While the present invention has been described above by way of a preferred embodiment, it is not intended to limit the invention, and the equivalents of the modification and retouching are still in the present invention without departing from the spirit and scope of the invention. Within the scope of patent protection.

100. . . Ultraviolet detector

110. . . Surface acoustic wave oscillator

112a, 112b. . . Matching circuit

114. . . Amplifier

120. . . Voltage controlled oscillator

130. . . Mixer

140. . . Phase-locked loop

150. . . Analog to digital converter

160. . . Processing unit

170. . . Low frequency amplifier

180. . . Differential amplifier

190. . . Display unit

200. . . Surface acoustic wave component

210a, 210b. . . electrode

220. . . Piezoelectric substrate

222. . . Substrate

224. . . Piezoelectric film

U. . . Ultraviolet light

1 is a block diagram of an ultraviolet light detector according to an embodiment of the present invention.

2 is a top plan view of the surface acoustic wave element of FIG. 1.

100. . . Ultraviolet detector

110. . . Surface acoustic wave oscillator

112a, 112b. . . Matching circuit

114. . . Amplifier

120. . . Voltage controlled oscillator

130. . . Mixer

140. . . Phase-locked loop

150. . . Analog to digital converter

160. . . Processing unit

170. . . Low frequency amplifier

180. . . Differential amplifier

190. . . Display unit

200. . . Surface acoustic wave component

210a, 210b. . . electrode

220. . . Piezoelectric substrate

222. . . Substrate

224. . . Piezoelectric film

U. . . Ultraviolet light

Claims (13)

An ultraviolet light detector comprising: a surface acoustic wave oscillator capable of receiving an ultraviolet light and outputting a first frequency signal according to the energy of the ultraviolet light; and a voltage controlled oscillator capable of outputting a second frequency signal; a mixer capable of mixing the first frequency signal with the second frequency signal to generate a mixed signal, the frequency of the mixed signal being between 1 Hz and 10 MHZ; a phase locked loop capable of The mixing signal is converted into a voltage analog signal; a type of comparison digital converter can convert the voltage analog signal into a digital signal; and a processing unit can calculate an energy value of the ultraviolet light according to the digital signal. The ultraviolet light detector of claim 1, wherein the surface acoustic wave oscillator comprises a surface acoustic wave component, and the surface acoustic wave component comprises: a piezoelectric substrate; and a pair of electrodes disposed at the pressure On an electrical substrate, wherein the electrodes do not overlap each other. The ultraviolet light detector of claim 2, wherein the electrodes are substantially identical in shape to each other. The ultraviolet light detector of claim 2, wherein the electrodes have substantially equal areas of each other. The ultraviolet light detector of claim 2, wherein each of the electrodes is a finger electrode. The ultraviolet light detector of claim 2, wherein the piezoelectric substrate comprises a substrate and a piezoelectric film disposed on the substrate. The ultraviolet light detector of claim 6, wherein the piezoelectric film is made of zinc oxide. The ultraviolet light detector of claim 6, wherein the substrate is made of LiNdO ₃ . The ultraviolet light detector of claim 1, wherein the energy value is power. The ultraviolet light detector of claim 1, wherein the mixer transmits the first frequency signal and the second frequency signal when the first frequency signal is mixed with the second frequency signal The frequency of the two is subtracted. The ultraviolet light detector of claim 1, further comprising a low frequency amplifier, wherein the low frequency amplifier is electrically connected between the mixer and the phase locked loop, and can amplify the mixed signal. The ultraviolet light detector of claim 1, further comprising a differential amplifier, wherein the differential amplifier is electrically connected to the phase lock The loop and the digital pair are analog converters and can amplify the voltage analog signal. The ultraviolet light detector of claim 1, further comprising a display unit electrically connected to the processing unit and capable of displaying the energy value.