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How to do a laser range finder?
The range finder is a tool for measuring the length or distance. At the same time, it can be combined with the angle measuring device or module to measure the angle, area and other parameters. The range finder has many forms, usually an elongated cylinder, which is composed of an objective lens, an eyepiece, a display device (which can be built in), a battery, and the like.
At present, a wide range of laser range finder is widely used. Usually, the display adopts an LCD display, but the LCD display has the following problems: (1) The LCD uses a backlight to emit light, and an illumination source needs to be added behind the liquid crystal, the brightness is general, and the transmission function is not provided. On nights when the light is weak or there is no light, the text and pattern on the display cannot be seen clearly; (2) the backlight is added, and the external dimensions of the range finder are increased accordingly, making the range finder large in size and inconvenient to carry. (3) LCD display manufacturing process is complex and costly.
The optical signal receiving of the laser range finder is mainly reflected and received and converted into an electrical signal. The signal is rather weak when the reflected receiving signal is far away, and is also subject to other external interference, so it is very difficult to receive and process the signal. The existing range finder adopts the following technical means: (1) using a high-sensitivity avalanche photodiode; (2) using an integrated transconductance amplifier or a high-frequency triode as a preamplifier; the above technical means, working due to an avalanche photodiode The voltage is relatively high, and the power supply boosting circuit will interfere with other lines, especially the interference of the preamplifier; because the high sensitivity avalanche photodiode, integrated transconductance amplifier and other devices are extremely expensive, the cost is higher; The triode is used as the preamplifier. Because of the poor thermal stability of the triode, the radiation resistance is poor, and the noise figure is large, it will affect the noise-to-noise ratio of the whole circuit, affecting the ranging distance and accuracy.
In summary, how to design a range finder that can effectively solve the existing problems has become one of the problems that those skilled in the art need to solve.
Technical realization elements:
In view of the above deficiencies of the prior art, the present invention provides a range finder.
In order to achieve the above object, the technical solution adopted by the utility model is as follows:
A range finder comprising a housing, an objective lens disposed in the housing, an eyepiece, a laser emitting mirror, a laser receiving mirror, a central processing unit, a display, a laser transmitter, a laser receiver, a signal amplifying circuit, a circuit board, and a power supply; The processor is respectively electrically connected to the display, the laser emitter, the laser receiver, the signal amplifying circuit, the circuit board, the power source, the display is located on the focal plane of the objective lens and the focal plane of the eyepiece, and the objective lens is integrally provided with the laser emitting mirror, and the laser receiver comprises a photo sensing element composed of a PIN photodiode E1 and a resistor R9, the signal amplifying circuit comprising a pre-voltage amplifying circuit, an amplifying unit with a negative feedback and an impedance converting unit, and a capacitor connected to the amplifying unit and the impedance converting unit C6, the pre-voltage amplification circuit comprises a field effect transistor V2, resistors R7, R8 and a capacitor C3, and the amplification unit with negative feedback and the impedance conversion unit comprise transistors V1, Q1, Q2, resistors R3, R4, R6, R10, R11 , R12, R13, R14, capacitor C7, C8, C9, C10, C12, PIN photodiode E1 negative end and resistor R9, FET V2 Connected FET is connected to capacitor C6 and V2.
Further, the display is a transmissive OLED display.
Compared with the prior art, the utility model has the following beneficial effects:
The utility model adopts a low-cost PIN photodiode as a light sensing component, and uses a high-frequency FET as a preamplifier, compared with the existing avalanche photodiode and an integrated transconductance amplifier as photoelectric conversion. And the amplification loop, the overall cost is low. The PIN photodiode is used, the working voltage is significantly reduced, the power consumption of the power supply circuit is reduced, and the radiation interference to the external circuit is reduced. The high frequency field with good temperature stability, strong radiation resistance and small noise figure is adopted. The effect tube is used as preamplifier. Compared with the existing triode as the preamplifier circuit, the temperature stability is better, the noise figure is smaller, so that the noise-to-noise ratio of the whole circuit is increased, and the quality and measurement of the amplified signal are improved. The accuracy of the distance increases the ranging distance. The utility model adopts the method of resisting capacitance separation to perform filtering and decoupling, more effectively eliminates homologous signals and other interferences, and improves small signal quality; and the post-stage amplifying circuit adopts a negative feedback and impedance transformation structure, so that the circuit is more stable.
The utility model adopts the OLED display compared with the conventional LCD display: (1) the OLED does not need a backlight, and can emit light by itself, so the OLED is brighter than the LCD, the contrast is large, and the color effect is good; (2) the OLED has no limitation of the viewing angle range, The viewing angle can generally reach 160 degrees, so that it will not be distorted when viewed from the side; (3) the OLED only needs to be lit to power up, and the voltage is lower, which is more energy-saving; (4) the weight of the OLED is lighter than the LCD. The material needs to be small, the manufacturing process is simple, and the cost in mass production is 20% lower than that of the LCD; (5) The OLED also has the characteristics of being bendable and shockproof.
Figure 1 is a schematic view of the structure of the present invention.
2 is a schematic structural view of a laser receiver and a signal amplifying circuit of the present invention.
Wherein, the corresponding name of the reference numeral is:
1-shell, 2-objective lens, 3-eyepiece, 4-laser mirror, 5-laser receiving mirror, 6-central processing unit, 7-display, 8-laser transmitter, 9-laser receiver, 10-circuit board , 11 - voltage amplification loop, 12 - amplification unit and impedance transformation unit.
The present invention will be further described with reference to the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments.
As shown in FIGS. 1 to 2, a range finder includes a housing 1, an objective lens 2, an eyepiece 3, a laser emitting mirror 4, a laser receiving mirror 5, a central processing unit 6, a display 7, and a laser emitter disposed in the housing. 8. The laser receiver 9, the signal amplifying circuit, the circuit board 10 and the power source; wherein the laser receiver 9 comprises a light sensing element composed of a PIN photodiode E1 and a resistor R9, the signal amplifying circuit comprising a pre-voltage amplifying circuit 11, The amplification unit with negative feedback and the impedance conversion unit 12, and the capacitor C6 connected to the amplification unit and the impedance conversion unit 12 are as follows: the positive terminal of the PIN photodiode E1 is connected to the capacitor C2 and the resistor R2, and the other end of the capacitor C2 is The negative pole of the power supply is connected, the other end of the resistor R2 is connected to the capacitor C1 and the resistor R1, the other end of the resistor R1 is connected to the power source -Vcc, and the other end of the capacitor C1 is connected to the negative pole of the power source; the negative end of the PIN photodiode E1 is connected with the resistor R9 and the field effect transistor V2. Connected; the FET V2 has a pole connected to the grounded capacitor C3 and the resistor R7 of the loop, and the FET V2 has a pole connected to the resistor R8 of the loop and the capacitor C6, and the resistor R 7. The other end of the resistor R8 is connected to the capacitor C5 and the resistor R5; the other end of the capacitor C5 is connected to the capacitor C4 and grounded, and the other end of the resistor R5 and the capacitor C4 is connected to the resistors R3 and R4; the other end of the capacitor C6 is connected to the transistor V1 and the resistor R6. Connection; the components of the amplification unit and the impedance conversion unit 12 are connected as follows: the emitter of the transistor V1 is grounded, the collector is connected to the resistors R4 and R12, and the other end of the resistor R12 is connected to the base of the transistor Q1, and the transistor Q1 is connected. The emitter is connected to the resistor R11, the collector of the transistor Q1 is grounded, the other end of the resistor R3 is connected to the power source Vcc, the resistor R10, the capacitors C7, C8, the other ends of the capacitors C7 and C8 are grounded, and the other end of the resistor R10 is connected with the resistor R11. The terminal, the resistor R13 and the capacitor C9 are connected, the other end of the capacitor C9 is grounded, and the other end of the resistor R13 is connected with the capacitor C10 of the emitter of the transistor Q2 and the ground of the other end, and the base of the transistor Q2 is connected with the resistor R6 and with the transistor Q1. The emitter and the resistor R11 are connected at one end, and the collector of the transistor Q2 is connected to one end of the resistor R14 and the capacitor C12 which is grounded at the other end; the collector of the transistor Q2 is also connected to the amplifying unit and impedance transformation Outside the capacitor C11 is connected to the circuit element 12, the capacitor C11 and C12 is connected to the other end of the capacitor C11 and the contact terminal OUT, OUT terminal is also connected to the central processor.
The display 7 is a transmissive OLED display, and the central processing unit 6 is electrically connected to the display 7, the laser emitter 8, the laser receiver 9, the signal amplifying circuit, the circuit board 10, and the power source, respectively, and the display 7 is located at the focal plane of the objective lens 2 and the eyepiece 3 On the focal plane, the objective lens 2 is integrally provided with the laser emitting mirror 4.
The working principle of the utility model is as follows:
The central processing unit 6 controls the laser emitter 8 to emit a measuring beam, and the measuring beam is transmitted through the laser emitting mirror 4 to the object to be measured, and the reflected beam of the object to be measured is projected onto the laser receiver 9 through the laser receiving mirror 5, and is converted. The electrical signal is amplified by the signal amplifying circuit and sent to the central processing unit 6. The central processor 6 calculates the corresponding value and outputs the data to the transmissive OLED display.
The working principle of the laser receiver 9 and the signal amplifying circuit: the PIN photodiode E1 works on the reverse bias voltage when receiving the laser signal reflected by the target object, and outputs a current signal; the resistor R9 is the same as the PIN photodiode E1. The loop, when the PIN photodiode E1 receives the laser signal reflected by the target object and outputs a current signal, converts the resistor R9 into a voltage signal. The pre-voltage amplifying circuit 11 amplifies the voltage signal connected to the resistor R9 and outputs it by C6. The amplifying unit and the impedance converting unit 12 with negative feedback mainly further amplify the voltage signal outputted by the pre-voltage amplifying circuit 11 and include two-stage amplification and impedance transformation. The transistors V1 and Q1 are composed of a plurality of resistors and capacitors, which are equivalent to a combined amplifier. The resistor R6 is the base bias resistor of the transistor V1 and is also a negative feedback resistor to stabilize the static operating point. At the same time, the transistor Q1 and the resistor R11 are an emitter follower, and the impedance change of the signal is performed, and the output low impedance is matched with the amplification loop composed of the latter transistor Q2 and the resistor R14. After being amplified, it is outputted by the capacitor C11 and outputted for use by the central processing unit 6.
In order to eliminate homologous signals and other interferences, the utility model sets the resistors R5 and R13 and the capacitors C5 and C10 to use the RC filter for filtering, and the resistors R10 and R3 and the capacitors C4 and C9 are separated by the RC filter. The coupling method effectively improves the filtering effect, improves the signal quality, and significantly increases the signal-to-noise ratio of the circuit output. Transmissive OLED displays also make the display better. The utility model has the advantages of low cost, good measuring effect and good popularization and application value.
The above embodiments are only one of the preferred embodiments of the present invention, and should not be used to limit the scope of protection of the present invention. Any alteration or retouching that is made in the design and spirit of the main body of the present invention, The technical problems solved by the invention are still consistent with the present invention and should be included in the scope of protection of the present invention.