JPH02105010A - Automatic distance measuring device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic distance measuring device (hereinafter referred to as an automatic distance measuring device) that measures distance using one pulse signal.

2. Description of the Related Art In recent years, simple automatic distance measuring devices have come into use in the field of inexpensive compact cameras.

A conventional automatic distance measuring device will be described below with reference to the block diagram of FIG. This circuit consists of photodiode 3
1 and 41, diodes 32 and 42, operational amplifier 33.4
3 and 55, resistors 51.52°, 53 and 54, and a reference voltage generation circuit 56.

The operation of the automatic distance measuring device configured as described above will be explained below.

First, when light is input to photodiodes 31 and 41,
A current corresponding to the intensity of the light flows through the diodes 32 and 42 and is converted into a voltage. Next, when current flows through the resistors 51 and 52 and the resistors 53 and 54 due to the output voltages of the operational amplifiers 33 and 43, the operational amplifier 55 outputs the difference between the output voltages of the operational amplifiers 33 and 43, and the light input to the photodiodes 31 and 41 is The difference in strength is required.

When the above-described operation is used in the triangulation method shown in FIG. 3, an output voltage corresponding to the distance can be obtained, and distance measurement can be performed.

The principle of the triangulation method shown in FIG. 3 will be explained below.

First, a pulse signal is input to the input terminal 62 of the infrared light emitting diode 61, and the pulsed light is transmitted to the object A66 and object B67.
radiate towards. Next, the pulsed light reflected from the object A66 is received by the photodiode 63, and the pulsed light reflected from the object B67 is received by the photodiode 64.
When photoelectrically converted, the reflected light is transferred to the photodiode 63 according to the distance between the object A66 and the object B67.
and 64 are input with different intensities, so distance data can be obtained by measuring the voltage difference output from photodiodes 63 and 64.

Problems to be Solved by the Invention However, in the conventional configuration, when external light is input to the photodiodes 31 and 41 shown in FIG.
Before entering 1, current is flowing through diodes 32 and 4.
Since the impedance of the pulsed light may change or become too small, it has been difficult to amplify the pulsed light component to a large extent and with high precision.

The present invention solves the above-mentioned conventional problems, and is an automatic method that can obtain high distance fl measurements by amplifying the pulsed light components to make them thicker and more accurate, without being affected by external light. The object of the present invention is to provide a distance measuring device.

Means for Solving the Problems To achieve this object, the automatic distance measuring device of the present invention connects the cathode of a photodiode to a power supply voltage terminal, connects the anode of the photodiode to the anode of the diode, and connects the cathode of the photodiode to a first current. The non-inverting input terminals of the amplifier and the second current amplifier are connected to the collector of the NPN transistor, and the cathode of the diode and the inverting input terminals of the first current amplifier and the second current amplifier are connected to a reference voltage generation circuit. and a first circuit in which the output terminal of the second current amplifier is connected to a capacitor whose one terminal is grounded and the base of the NPN transistor, and the emitter of the NPN transistor is grounded; A second circuit having the same configuration and having a circuit connection in which only the polarity of the input terminal of the first current amplifier is reversed is combined, and each of the first circuit and the second circuit is connected. A switch means commonly connected to the second current amplifier is added, and the output terminal of the first current amplifier of each of the first circuit and the second circuit is commonly connected to the output terminal, and the resistor The other terminal of the resistor is connected to the reference voltage generating circuit.

According to the configuration of the present invention, a combination circuit of a current amplifier, a capacitor, and an NPN transistor allows all of the photocurrent generated by external light to flow into the NPN transistor.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of an automatic distance measuring device according to an embodiment of the present invention. In this circuit configuration, the cathode of the photodiode 1 is connected to the power supply voltage terminal 21, and the anode of the photodiode 1 is connected to the anode of the diode 2, the non-inverting input terminal of the first current amplifier 4, the second current amplifier 3, and the NPN It is connected to the collector of the transistor 6, the cathode of the diode 2 and the inverting input terminals of the first current amplifier 4 and the second current amplifier 3 are connected to the reference voltage generation circuit 22, and the output terminal of the second current amplifier 3 is connected to the reference voltage generation circuit 22. A first circuit A is connected to a capacitor 5 whose one terminal is grounded and the base of an NPN transistor 6, and whose emitter is grounded, a photodiode 11, a diode 12, current amplifiers 13 and 14, a capacitor 15, A second circuit consisting of an NPN transistor 16 and a circuit connection in which only the polarity of the input terminal of the current amplifier 14 is connected in reverse is combined, and a switch terminal 24 is commonly connected to the current amplifiers 3 and 13.
The output terminals of current amplifiers 4 and 14 are commonly connected to an output terminal 25 and also to a resistor 23, and the other terminal of the resistor 23 is connected to a reference voltage generation circuit 22.

The operation of an embodiment of the automatic distance measuring device 1 of the present invention configured as described above will be described below. First, the four current amplifiers 3.4.13. While photodiodes 1 and 14 are in operation, external light is received by photodiodes 1 and 11. In this state, current amplifiers 3 and 13 and NPN transistors 6 and 16
Since feedback is applied to diode 2
The anodes of 1 and 12 are fixed at the reference voltage, and the photocurrent generated in photodiodes 1 and 11 due to external light is all NP.
flows through N transistors 6 and 16. Next, the operation of the current amplifiers 3 and 13 is stopped by a signal input to the switch terminal 24. Even in this state, capacitors 5 and 15
Since all the current generated by external light flows through the NPN transistors 6 and 16, the potentials of the anodes of the diodes 2 and 12 are kept at a constant reference voltage. Next, when a light emission pulse is input to photodiodes 1 and 11, the photocurrents of photodiodes 1 and 11 increase, and the increased amount flows to diodes 2 and 12, so that a voltage is generated in diodes 2 and 12, respectively. Current amplifiers 4 and 14 output currents proportional to the currents generated in diodes 2 and 12, respectively. However, current amplifier 4
Since the input terminals and 14 have opposite polarities, the current flowing through the resistor 23 is the difference between the output currents of the current amplifiers 4 and 14. Therefore, by checking the voltage at the output terminal 25, the ratio of the intensity of the light emission pulses input to the photodiodes 1 and 11 can be determined from the following formula, and the voltage at the output terminal 25 is not affected by external light. Therefore, accuracy is required (the intensity ratio of the light emission pulses mentioned above is determined).

The intensity of the light emission pulse input to photodiode 1' is L.
R, the intensity of the light emission pulse input to photodiode 11 is LL, the sensitivity of photodiodes 1 and 11 is 81, the voltage generated in diode 2 is VRN, the voltage generated in diode 12 is vL, the mutual conductance of current amplifiers 4 and 14 is gm , the output current of current amplifier 4 is IR, current amplifier 1 is
Let the output current of 4 be It, and the resistance value of resistor 23 be R1, and the output voltage be VOUT.
Is q IsRg m k T
danL ” e n LL where k is the Boltzmann constant, T is the absolute temperature, q is the elementary charge, and Is is the saturation current of the diodes 2 and 12.

From this vauT, the distance can be determined using the same triangulation principle as described in FIG. Therefore, accuracy is improved without being affected by external light (
Can measure distance.

As described above, according to this embodiment, it is possible to realize a highly accurate and inexpensive automatic distance measuring device that is not affected by external light in a short time because it is a circuit that is easy to integrate into an IC and only requires one light emission pulse. .

Effects of the Invention According to the present invention, by using a combination of a current amplifier, a capacitor, and an NPN transistor, all of the photocurrent generated by external light can flow into the NPN transistor, thereby making it possible to measure distances without being affected by external light. Furthermore, by performing logarithmic exchange using diodes, it is possible to realize an excellent automatic distance measuring device that can obtain the effect of having a wide dynamic range.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an automatic ranging device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional automatic ranging device, and FIG. 3 is a diagram of the principle of triangulation method. 1.11...Photodiode, 2,12...
...Diode, 3,13.4.14...
Current amplifier, 5.15...Capacitor, 6,1
6...NPN transistor, 21...
Power supply voltage terminal, 22...Reference voltage generation circuit, 2
3...Resistor, 24...Switch terminal,
25...Output terminal. Name of agent: Patent attorney Shigetaka Awano and one other person, 41-
・-Fushidai ^-do 2, L2-m-9'i;"-Y 3, hand, 13.1 book-1-41 Jibai Asif. 5.15---Condeshifu 24-11 Zuirazu Hx, 1 25--One output #p hand total・-FF rotations completed---Y2 times &

Claims (1)

[Claims] Connect the cathode of the photodiode to the power supply voltage terminal,
Connecting the anode of the photodiode to the anode of the diode, the non-inverting input terminals of the first current amplifier and the second current amplifier, and the collector of the NPN transistor,
The cathode of the diode, the inverting input terminals of the first current amplifier and the second current amplifier are connected to a reference voltage generation circuit, and the output terminal of the second current amplifier is connected to a capacitor with one terminal grounded. A first circuit connected to the base of the NPN transistor and having the emitter of the NPN transistor grounded has the same configuration as the first circuit, and only the polarity of the input terminal of the first current amplifier is reversed. a second circuit of the connected circuit connections, adding switch means commonly connected to the second current amplifier of each of the first circuit and the second circuit; and the output terminals of the first current amplifiers of the second circuits are commonly connected to the output terminal, and also connected to a resistor, and the other terminal of the resistor is connected to the reference voltage generation circuit. Features automatic distance measuring device.