JP2006153814A - Distance measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active distance measuring apparatus for improving the maintenance of distance measurement performance and extending the lifetime of the apparatus. <P>SOLUTION: The distance measuring apparatus comprises: a light projection section 6 for projecting luminous flux to an object; a light reception section 7 for receiving luminous flux that is reflected from the object and returns and outputting detection signals I1, I2; an operation section 8 for measuring distance to the object, based on the detection signals I1, I2; and a control section 9 for controlling the operation of the light projection section 6 and the light reception section 7. The light projection section 6 includes a light-emitting element 1 for radiating luminous flux according to a drive current Iled and a drive circuit 10 for supplying the drive current Iled to the light-emitting element 1. The control section 9 controls the drive circuit 10 of the light projection section 6, sweeps the drive current Iled from a low level to a high level, and projects light, and then monitors the quantity of received light at the light reception section 7 and stops sweeping the drive current Iled when a level suitable for measuring distance is reached for measuring distance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a light projecting unit that projects a light beam onto an object, a light receiving unit that receives a light beam reflected and returned from the object and outputs a detection signal, and the object based on the detection signal. The present invention relates to an optical active distance measuring device including a calculation unit that performs distance measurement and a control unit that controls operations of a light projecting unit and a light receiving unit.

  Optical distance measuring devices are used for various purposes such as automatic focusing of cameras and interpersonal sensors of ticket vending machines. In particular, an active distance measuring device that projects distance measuring light such as infrared rays onto an object and uses the reflected signal light to determine the distance of the object is widely applied to autofocus of compact cameras, etc. .

  Such an active distance measuring device is basically configured as shown in FIG. In the figure, reference numeral 1 is a light emitting element composed of an infrared light emitting diode (IRLED) or the like, and 2 is a light projecting lens for condensing and projecting this light on an object 3. Then, the reflected signal light from the object 3 is received by the light receiving element 4 including the light receiving lens 4 and the light position detecting element (PSD) separated from the light projecting lens 2 by the base line length D, and the light receiving position x is received. If it calculates | requires, the distance Z to a target object will be calculated | required by the relationship of Z = D * f / x using the focal distance f and the base line length D of the light-receiving lens 4. FIG.

  This method uses a difference in geometric position between the light projecting lens 2 and the light receiving lens 4 and follows the principle of triangulation. The light receiving element 5 made of PSD or the like generates a photocurrent at the light incident position. However, since the conductive portion up to the both end electrodes has a resistance component, the two photocurrent signals I1, I2 are changed according to the light incident position. I2 is output. Thus, the light receiving position x is obtained by calculating the ratio between the two photocurrent signals I1 and I2. For example, x = I1 / (I1 + I2).

Such an active distance measuring device is described in, for example, Patent Documents 1 to 3 below.
Japanese Patent Laid-Open No. 01-199109 JP 08-136247 A Japanese Utility Model Publication No. 05-043110

  For example, an infrared light emitting diode (IRLED) is frequently used as the light emitting element of the active distance measuring device. The infrared light emitting diode emits light in accordance with the drive current, and generates light necessary for active distance measurement. The accuracy of active ranging is determined by the signal-to-noise ratio (S / N ratio). In order to increase the S / N ratio and perform stable ranging, it is better that the emission intensity of the IRLED is higher. As the emission intensity increases, the amount of light reflected from the object increases, and accurate ranging can be performed without being affected by optical noise such as ambient light or electrical noise. Therefore, from the viewpoint of improving the distance measurement performance, it is preferable to obtain a sufficient light emission intensity by setting the drive current higher. On the other hand, current-driven light-emitting elements such as infrared light-emitting diodes have a property that their lifetime is determined according to the amount of light emission. As the cumulative amount of light emission increases, the luminance decreases and the lifetime decreases. Therefore, from the viewpoint of durability of the distance measuring device, it is preferable to suppress the drive current supplied to the light emitting element as much as possible. As described above, the active distance measuring device is a problem to be solved because the improvement of the distance measuring performance and the life extension of the device are not compatible.

  SUMMARY OF THE INVENTION In view of the above-described problems of the prior art, an object of the present invention is to provide an active distance measuring device capable of achieving both improvement in distance measuring performance and extending the life of a light emitting element. In order to achieve this purpose, the following measures were taken. That is, the present invention includes a light projecting unit that projects a light beam onto an object, a light receiving unit that receives a light beam reflected and returned from the object and outputs a detection signal, and a detection signal based on the detection signal. A distance measuring device comprising a calculation unit for measuring a distance to an object and a control unit for controlling operations of the light projecting unit and the light receiving unit, wherein the light projecting unit emits a light beam according to a drive current. And a driving circuit that supplies a driving current to the light emitting element, and the control unit controls the driving circuit of the light projecting unit to sweep the driving current from a low level to a high level. In addition to performing light, the amount of light received by the light receiving unit is monitored, and when a level suitable for distance measurement is reached, sweeping of the drive current is stopped to perform distance measurement.

  Preferably, the sweep of the drive current is started from a predetermined low level above the zero level to a high level. The controller performs distance measurement while maintaining the level of the drive current for a predetermined time when the amount of light received by the light receiver reaches a level suitable for distance measurement. The control unit sweeps the drive current exponentially from a low level to a high level. The arithmetic unit performs distance measurement based on the principle of triangulation using a detection signal indicating the light receiving position of the light beam output from the light receiving unit.

  According to the present invention, the active distance measuring device performs light projection while controlling the light projecting unit to sweep the drive current from a low level to a high level, and monitors the amount of light received by the light receiving unit and is suitable for distance measurement. When the level is reached, the drive current sweep is stopped and distance measurement is executed. In the present invention, when the amount of received light reaches a level suitable for distance measurement, the drive current is fixed and the amount of emitted light is suppressed. By saving unnecessary light emission, the life of the light emitting element can be extended. In addition, the current consumption can be saved by suppressing the drive current. On the other hand, the amount of received light is controlled so as to be at a level suitable for distance measurement according to the state of the object for distance measurement. Thereby, there is no possibility that the distance measurement performance is impaired. As described above, it is possible to obtain an active distance measuring device that achieves both long life of the light emitting element and maintenance of distance measuring performance. A two-stage method is also conceivable in which preliminary distance measurement is performed in advance to set a drive current corresponding to the object, and this distance measurement is performed using the set drive current. However, if the preliminary projection and the main projection are performed separately, there is an inconvenience that the total time required for the distance measurement becomes long. On the other hand, in the present invention, the driving current corresponding to the object is set and the distance is measured by one light projection. Thereby, the distance measurement time can be shortened.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, in order to clarify the background of the present invention, a constant voltage driving type active distance measuring device will be described as a reference example with reference to FIG. As shown in the figure, the distance measuring device includes a light projecting unit 6, a light receiving unit 7, a calculation circuit 8 that forms a calculation unit, and a sequencer 9 that forms a control unit. The light projecting unit 6 projects a light beam onto the object. The light receiving unit 7 receives the light beam reflected and returned from the object and outputs detection signals I1 and I2. The arithmetic circuit 8 measures the distance to the object based on the detection signals I1 and I2. Specifically, distance measurement data is obtained by performing a ratio calculation of the detection signals I1 and I2. The distance measurement data is once sample-held by the sample hold circuit 12, and then output to an external device via the amplifier A3. The sequencer 9 controls the operations of the light projecting unit 6 and the light receiving unit 7.

  The light projecting unit 6 includes a light emitting element 1 that emits a light beam in response to a driving current Iled, and a driving circuit 10 that supplies the driving current Iled to the light emitting element 1. For example, an infrared light emitting diode can be used as the light emitting element 1. The drive circuit 10 includes a load resistor Rled connected to the cathode of the two-terminal light emitting element 1 and a drive transistor Tr. The base of the drive transistor Tr is connected to the sequencer 9, the collector is connected to one end of the load resistor Rled, and the emitter is grounded. The drive circuit 10 further includes a constant voltage circuit composed of an amplifier A and a transistor Tr1. One input terminal of the two-terminal amplifier A (op-amp) is connected to the sequencer 9 and is supplied with a constant voltage Vled. The other input terminal of the amplifier A is connected to the anode of the two-terminal light emitting device 1. The output terminal of the amplifier A is connected to the base of the transistor Tr1. The emitter of the transistor Tr1 is connected to the power supply Vcc, and the collector is connected to the anode of the light emitting element 1.

  The constant voltage circuit composed of the amplifier A and the transistor Tr1 applies a constant voltage Vled equal to the control voltage Vled supplied from the sequencer 9 to the anode of the light emitting element 1 and drives it at a constant voltage. Specifically, if the voltage drop of the light emitting element 1 is Vf and the voltage drop of the drive transistor Tr is Vtr, the drive current Iled is given by (Vled−Vf−Vtr) / Rled. Actually, when the sequencer 9 applies a control pulse to the base of the drive transistor Tr, the drive transistor Tr becomes conductive, and the drive current Iled flows through the light emitting element 1, and as a result, the luminance L corresponds to the control voltage Vled. The light emitting element 1 emits light. As described above, the conventional active distance measuring device always determines the light emission luminance L with the constant control voltage Vled regardless of the condition of the object.

  The light receiving unit 7 includes a light receiving element 5 made of, for example, PSD and amplifiers A1 and A2 connected to both ends thereof. One amplifier A <b> 1 amplifies the light reception current output from one end of the light receiving element 5 and supplies the detection current I <b> 1 to the arithmetic circuit 8. The other amplifier A2 amplifies the light reception current output from the other electrode of the light receiving element 5 and supplies the detection current I2 to the arithmetic circuit 8 side. A steady current drawing circuit (DCC) is connected between the input and output of each amplifier A1, A2. The steady current extraction circuit DCC is controlled by the sequencer 9 so that a steady current component (DC component) caused by ambient light or the like is extracted from the received light current and only the signal component can be supplied to the arithmetic circuit 8 side.

  The light receiving element 5 on the light receiving unit 7 side outputs detection signals I1 and I2 corresponding to the light receiving position of the light reflected from the object to the arithmetic circuit 8 side. The arithmetic circuit 8 calculates the ratio of the detection signals I1 and I2 to obtain distance measurement data. At this stage, the sequencer 9 controls the opening and closing of the switch SW1, and samples and holds the distance measurement data in the sample and hold circuit 12. The distance measurement data sampled and held is output to the main body of the apparatus via the amplifier A3.

  FIG. 2 is a circuit diagram showing another reference example of the active distance measuring device. The active distance measuring device shown in FIG. 1 employs constant voltage drive, whereas the reference example shown in FIG. 2 employs constant current drive. The light receiving unit 7, the calculation unit 8, the sequencer 9, and the sample hold circuit 12 are the same as those in the reference example of FIG. 1, but the configuration of the light projecting unit 6 is different.

  As shown in the figure, the light projecting unit 6 includes a light emitting element 1 that emits a light beam in accordance with the driving current Iled, and a driving circuit 10 that supplies the driving current Iled to the light emitting element 1. The light emitting element 1 is a two-terminal device such as an infrared LED. The drive circuit 10 includes a 2-input 1-output type amplifier (op-amp) A, a drive transistor Tr, and a load resistor Rled. The collector of the driving transistor Tr is connected to the cathode of the two-terminal light emitting element 1. The anode is connected to the power source Vcc. The emitter of the drive transistor Tr is grounded via the load resistor Rled. The base of the drive transistor Tr is connected to the output terminal of the amplifier A. One input terminal of the amplifier A is connected to the sequencer 9 and receives a control pulse. This control pulse has a voltage Vref and a time width Ton. The other input terminal of the amplifier A is connected to the emitter of the drive transistor Tr. With this configuration, the drive circuit 10 is a constant current source for the light emitting element 1. In response to the control pulse supplied from the sequencer 9, the drive circuit 10 passes a constant current Iled expressed by Iled = Vref / Rled to the light emitting element 1 for a predetermined light emission time Ton. The light emitting element 1 emits light with a luminance corresponding to a constant driving current Iled.

  The distance measuring device according to the reference example shown in FIGS. 1 and 2 uses a two-terminal device such as an infrared LED as a light emitting element. As is well known, the luminance of an LED decreases due to the amount of light emission and the time of light emission, and its lifetime is limited. The lifetime of the LED is significantly affected by various parameters such as light emission current, temperature, light emission time, and repetitive light emission interval, and its durability is limited.

  In a conventional distance measuring device, the life required by the application is first determined. A predetermined light emission current level and light emission time are determined so as to satisfy the required life or durability. Naturally, setting the light emission current level lower and setting the light emission time shorter leads to longer life.

  On the other hand, the active distance measuring device has a higher S / N ratio and higher basic distance measuring performance as the difference in intensity between ambient light (noise) and light emission (signal) increases. Therefore, from the viewpoint of ranging performance, it is preferable that the driving current is set as high as possible to increase the amount of light emission, and it is possible to accurately measure an object at a long distance and low reflectance. As described above, the improvement in durability performance and the improvement in basic ranging performance are in a mutually contradictory relationship. In reality, the amount of light emission is determined by the durability performance required for the product, and ingenuity is devised to improve the accuracy as much as possible. For example, distance measurement is repeated on the same object within an allowable range, and the obtained result is averaged to obtain final distance data.

  In the conventional active distance measuring device shown in FIGS. 1 and 2, the light emission intensity and the light emission time are fixedly set in advance, and distance measurement is performed regardless of the state of the object. However, in the actual distance measurement, the distance of the object changes, and the surface reflectance also changes. For example, if it is assumed that the object is positioned in the front and back in the range of 0.5 to 3 m and the surface reflectance varies between 9 and 72%, the object having the distance of 3 m and the reflectance of 9% is the most received light amount. Less. On the other hand, the amount of light received by an object at a position of 0.5 m and a surface reflectance of 72% is 288 times that of the previous example. This ratio is obtained by light quantity simulation. In other words, the light emission amount required under the best condition may be 1 / 288th of the light emission amount required under the worst condition. For example, when measuring a target with a distance of 3 m and a surface reflectance of 9%, when a driving current of 1 A is required, an object with a surface reflectance of 0.5 m and a reflectance of 72% is about 3.5 mA. The light emission current is good.

  For example, when the driving current is set to 1 A in the active distance measuring device shown in FIG. 2, an object having a distance of 3 m and a surface reflectance of 9% has an appropriate light emission amount, whereas the surface reflectance is 0.5 m. In the case of a 72% target, light emission corresponding to the drive current of 1A-3.5 mA = 996.5 mA becomes unnecessary. Due to this loss, the durability of the active distance measuring device cannot be improved.

  FIG. 3 is a circuit diagram showing a first embodiment of the distance measuring apparatus according to the present invention. For easy understanding, portions corresponding to those of the active distance measuring device according to the reference example shown in FIGS. 1 and 2 are denoted by corresponding reference numerals. As shown in the figure, this active distance measuring device receives a light beam 6 reflected from the object and outputs detection signals I1 and I2 by projecting a light beam to the object. A light receiving unit 7, a calculation circuit (calculation unit) 8 that measures a distance to an object based on the detection signals I 1 and I 2, and a sequencer (control unit) 9 that controls operations of the light projecting unit 6 and the light receiving unit 7. It consists of

  The light projecting unit 6 includes a light emitting element 1 made of an LED or the like and a drive circuit 10. The anode of the two-terminal light emitting element 1 is connected to the power supply Vcc, and the cathode is connected to the drive circuit 10. The drive circuit 10 includes a 2-input 1-output type amplifier (op-amp) A, a drive transistor Tr, and a load resistor Rled. The collector of the drive transistor Tr is connected to the cathode of the light emitting element 1, and the emitter is grounded via the load resistor Rled. The base of the transistor Tr is connected to the output terminal of the amplifier A. A control voltage Vref is applied to one input terminal (hereinafter referred to as an input node in this specification) of the amplifier A, and the other input terminal is connected to the emitter of the transistor Tr. As a result, the drive circuit 10 passes a drive current Iled defined by Iled = Vref / Rled to the light emitting element 1. As a result, the light emitting element 1 emits light with a luminance L corresponding to the control voltage Vref.

  A constant current source i, a load capacitor C, and a switch SW are connected to the input node and are a part of the drive circuit 10. The constant current source i is connected between the power supply Vcc and the input node. The load capacitor C is connected between the input node and the ground line. The switch SW is also connected between the input node and the ground line. The opening / closing of the switch SW is controlled by a control pulse supplied from the sequencer 9.

  The light receiving unit 7 includes a light receiving element 5 and a pair of amplifiers A1 and A2. The light receiving element 5 is composed of, for example, a position detecting element (PSD), and outputs an optical signal corresponding to the light receiving position of the light returned from the object from a pair of electrodes. The amplifiers A1 and A2 amplify optical signals output from both electrodes of the light receiving element 5, and output the amplified signals to the arithmetic circuit 8 side as detection signals I1 and I2. A DCC for extracting a steady component is connected between the input / output terminals of the amplifiers A1 and A2.

  The arithmetic circuit 8 calculates the ratio of the detection signals I1 and I2 output from the light receiving unit 7 to obtain distance measurement data. The distance measurement data is sampled and held by the sample and hold circuit 12 and then output to the apparatus main body via the amplifier A3.

  The sequencer 9 supplies the above-described control pulse to the light projecting unit 6 side, and includes a pair of external comparators C1 and C2. The detection current I1 is supplied from the light receiving unit 7 side to the positive input terminal of the comparator C1, and a predetermined threshold voltage Vth is supplied from the sequencer 9 side to the other input terminal. The output terminal of the comparator C1 is connected to the sequencer 9. Similarly, a detection current I2 is supplied to the positive input terminal of the comparator C2 from the light receiving unit 7 side, a predetermined threshold voltage Vth is supplied to the negative input terminal from the sequencer 9 side, and an output terminal is connected to the sequencer 9. . In such a configuration, the control unit composed of the sequencer 9 and the pair of comparators C1, C2, etc. controls the drive circuit 10 of the light projecting unit 6 and projects the light while sweeping the drive current Iled from the low level to the high level. The amount of light received by the light receiving unit 7 is monitored, and when the level reaches a level suitable for distance measurement, the sweep of the drive current Iled is stopped to perform distance measurement, and the switch SW1 of the sample hold circuit 12 is controlled. Confirm the distance measurement result.

  FIG. 4 is a timing chart for explaining the operation of the distance measuring apparatus according to the present invention shown in FIG. In the standby period T0, the switch SW is in the on state and the input node is grounded, so Vref is at the zero level. Therefore, since the drive current Iled does not flow, the light emission intensity L is also zero. Further, since the light receiving unit 7 side does not receive any light from the object, there is no output from the comparator C1 or C2. Subsequently, when ranging starts at timing T1, the sequencer 9 outputs a control pulse to turn the switch SW from on to off. As a result, the current supplied from the constant current source i starts to be charged into the load capacitor C, and the potential Vref of the input node rises linearly from the low level to the high level. Accordingly, the drive current represented by Iled = Vref / Rled is swept from the low level to the high level, and as a result, the light emission intensity L gradually increases. In accordance with this, the amount of light received on the light receiving unit 7 side also increases.

  At timing T2, the levels of the detection currents I1 and I2 corresponding to the amount of received light exceed the preset threshold voltage Vth. This threshold voltage Vth is set in advance on the sequencer 9 side so that the amount of received light is in a range suitable for distance measurement. When the levels of the detection signals I1 and I2 exceed Vth, the outputs of the comparators C1 and C2 are inverted from the low level to the high level. In response to this, the sequencer 9 releases the control pulse, and the switch SW is turned on from off. Since the input node is grounded by the switch SW, Vref suddenly falls to zero level. Therefore, the emission intensity L is also zero. Necessary distance data can be obtained by measuring the distance with the light emission intensity L at the timing T2.

  As is clear from the above description, the voltage Vref is swept with time at the light emission start timing T1. For example, the corresponding drive current Iled is swept so as to change from 0 mA to 1.2 A. At the same time, the amount of reflected light returning to the light receiving unit 7 is monitored by the comparators C1 and C2, and when the amount of light received is sufficient as the amount of light for distance measurement, the sweep is stopped and light emission is ended. The amount of received light on the light receiving unit 7 side is determined by monitoring the detection currents I1 and I2 and both are equal to or higher than the threshold voltage Vth. Alternatively, I1 + I2 representing the total light amount of the light receiving element 5 may be monitored with a single comparator. Further, Vth for determining the level for determination may be appropriately corrected according to ambient brightness, temperature, or the like.

  FIG. 5 is a circuit diagram showing a main part of the second embodiment of the active distance measuring device according to the present invention. The main part is a light projecting part. The remaining part is the same as that of the first embodiment shown in FIG. The light projecting unit shown in FIG. 5 is basically similar to the light projecting unit shown in FIG. 3, and corresponding parts are denoted by corresponding reference numerals for easy understanding. The difference is that a bias resistor R is connected between the load capacitor C and the ground line. The voltage across the bias resistor R is set to V1.

  FIG. 6 is a timing chart for explaining the operation of the second embodiment shown in FIG. Ranging starts when timing T1 is reached after waiting period T0. At this time, the switch SW is turned off by the control from the sequencer, charging of the load capacitor C from the constant current source i starts and Vref starts to rise. At this time, sweeping of the control voltage Vref starts from a predetermined low level V1 above the zero level toward the high level. In other words, by adding the bias resistor R, the sweep start voltage is increased by V1 to put on clogs. As a result, the timing T2 at which the levels of the comparators C1 and C2 are inverted is shortened. As is clear from the timing chart of FIG. 4, in the timing chart of FIG. 6, the light emission period T1-T2 is shortened, and the distance measurement time can be shortened accordingly. The initial voltage V1 is preferably set so as to correspond to the minimum light emission luminance necessary for distance measurement.

  FIG. 7 is a circuit diagram showing a light projecting unit as a main part of the third embodiment of the distance measuring apparatus according to the present invention. Basically, it is similar to the second embodiment shown in FIG. 5, and corresponding reference numerals are assigned to corresponding parts. The difference is that a series connection of a switch SW2 and a constant current source i2 is inserted in parallel with the load capacitance C. As shown, one end of the switch SW2 is connected to one end of the load capacitor C, and the other end is connected to one end of the constant current source i2. The other end of the constant current source i2 is grounded. As with the switch SW, the switch SW2 is controlled to open and close by a sequencer.

  FIG. 8 is a timing chart for explaining the operation of the third embodiment shown in FIG. At the timing T1 from the waiting period T0, the switch SW is switched from on to off, and the potential Vref of the input node starts to rise from V1. As a result, at the time T2 when the amount of received light reaches a level suitable for distance measurement, the outputs of the comparators C1 and C2 are inverted. In response to this, the switch SW2 is switched from OFF to ON. As a result, the potential of the input node Vref is maintained constant according to the ratio of the constant current i flowing into the input node and the constant current i2 flowing out from the input node. Thereafter, at timing T3, the switch SW2 is turned off and the switch SW is turned on. Since the input node is grounded via the switch SW, Vref returns to the zero level. As is clear from the above description, the light emission intensity L is maintained for a predetermined period from the timing T2 to the timing T3 after the light emission luminance L reaches a level suitable for distance measurement at the timing T2. Stable distance data can be obtained by performing distance measurement in this period T2-T3. As described above, the third embodiment stably performs distance measurement while maintaining the level of the drive current for a predetermined time when the amount of light received by the light receiving unit reaches a level suitable for distance measurement.

  FIG. 9 is a circuit diagram showing the main part of the fourth embodiment of the distance measuring apparatus according to the present invention. As shown in the figure, a resistor R is connected between the input node and the power supply Vcc, while a capacitor C is connected between the input node and the ground line. A switch SW is connected in parallel with the capacitor C. The on / off of the switch SW is controlled by a sequencer.

  FIG. 10 is a timing chart for explaining the operation of the fourth embodiment shown in FIG. As shown in the figure, the switch SW is switched from on to off at the timing T1 when ranging starts from the waiting period T0. As a result, the capacitor is charged from the power supply line Vcc toward the ground line at a speed determined by the time constant RC, and the potential Vref of the input node increases. The rising curve at this time is determined by the time constant RC and becomes exponential. Along with this, the emission luminance also increases exponentially from the low level to the high level. At time T2 when the amount of received light reaches a level suitable for distance measurement, the outputs of the comparators C1 and C2 are inverted, the switch SW is turned on, and Vref is reset to zero. By sweeping the drive current exponentially in this way, the time to reach the high level from the low level can be shortened compared to the case where the drive current is swept linearly as in the first embodiment. It leads to shortening of time.

  FIG. 11 is a schematic perspective view showing an example of a camera incorporating the distance measuring device according to the present invention. The camera 25 includes a lens barrel 27 on the front surface of the body 26. An active distance measuring device 0 including a light projecting unit 6 and a light receiving unit 7 is attached to the body 26. The light projecting unit 6 projects a light beam onto an object located in the optical axis direction. The light receiving unit 7 receives a light beam reflected and returned from the object, and outputs a detection signal corresponding to the light receiving position. The distance measuring device 0 determines the distance to the object based on the detection signal output from the light receiving unit 7, and performs distance measurement based on the principle of triangulation, for example.

  FIG. 12 is a schematic diagram showing another application example of the distance measuring device according to the present invention, which is used as a human detection sensor. As shown in the figure, a urinal 31 provided on the wall surface 32 is connected to a water supply pipe 33 for supplying washing water to the urinal 31 and a water distribution pipe 34 for discharging sewage. An electromagnetic valve 35 is disposed in the middle of the water supply pipe 33. The electromagnetic valve 35 has a coil (not shown) and a valve body provided in the coil, and is closed when the coil is not excited (normal state) to shut off the water supply pipe 33 and open with the excitation of the coil. Thus, on / off control is performed so that the water supply pipe 33 is opened. Then, the washing water is supplied to the urinal 31 through the water supply pipe 33 by the opening operation of the electromagnetic valve 35. The distance measuring device 0 according to the present invention is disposed above the urinal 31 so that the presence or absence of the user of the urinal 31 is detected. The control circuit 37 is a microcomputer having a CPU, ROM, RAM, and the like, and is embedded in the wall surface 32 above the urinal 31. A distance measuring device 0 and an electromagnetic valve 35 are connected to the control circuit 37, and the control circuit 37 inputs a detection result of the distance measuring device 0 and outputs a drive signal to the electromagnetic valve 35 based on the detection result. To do. That is, control is performed so that the washing water flows when the user leaves after entering the predetermined distance range.

  FIG. 13 is a schematic diagram showing another application example of the distance measuring apparatus according to the present invention. FIG. 13 is a perspective view showing an external configuration of an ATM that is one embodiment of an automatic transaction apparatus. This ATM is installed so that at least the front surface is exposed to the outdoors, etc., and the apparatus main body includes a bill deposit / withdrawal port 41 that can be opened and closed by a shutter, a CRT 42 as a display device for dialog with a user, A key input unit 43, a card mounting unit 44 on which a user authentication card is mounted, a distance measuring device 0 as a personal sensor disposed on the front surface of the apparatus main body, and the like are provided. Is installed. The distance measuring device 0 includes a light projecting unit 6 and a light receiving unit 7. The ATM is placed in a standby state or a power saving state when there is no user. Even in this case, the distance measuring device 0 is in an operating state. When the distance measuring device 0 detects the approach of the user, the ATM returns from the standby state to the operating state.

It is a circuit diagram which shows the reference example of a distance measuring device. It is a circuit diagram which shows the other reference example of a distance measuring device. 1 is a circuit diagram showing a first embodiment of a distance measuring device according to the present invention. It is a timing chart used for operation | movement description of 1st embodiment. It is a circuit diagram which shows the principal part of 2nd embodiment of the distance measuring device concerning this invention. It is a timing chart used for operation | movement description of 2nd embodiment. It is a circuit diagram which shows the principal part of 3rd embodiment of the distance measuring device concerning this invention. It is a timing chart used for operation | movement description of 3rd embodiment. It is a circuit diagram which shows the principal part of 4th embodiment of the distance measuring device concerning this invention. It is a timing chart used for operation | movement description of 4th embodiment. It is a perspective view which shows the application example of the distance measuring device concerning this invention. It is a typical sectional view showing other application examples similarly. It is a typical perspective view which similarly shows another application example. It is a schematic diagram which shows the principle of the conventional ranging apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 0 ... Distance measuring device ... 1 Light emitting element, 5 ... Light receiving element, 6 ... Light emitting part, 7 ... Light receiving part, 8 ... Arithmetic circuit, 9 ... Sequencer, 10 ... Drive circuit, 12 ... Sample hold circuit

Claims (5)

A light projecting unit that projects a light beam onto the object, a light receiving unit that receives the light beam reflected and returned from the object and outputs a detection signal, and a measurement to the object based on the detection signal. A distance measuring device comprising a calculation unit that performs distance and a control unit that controls operations of the light projecting unit and the light receiving unit,
The light projecting unit includes a light emitting element that emits a light beam according to a driving current, and a driving circuit that supplies a driving current to the light emitting element,
The control unit controls the driving circuit of the light projecting unit to perform light projection while sweeping the drive current from a low level to a high level, and monitors the amount of light received by the light receiving unit and is suitable for distance measurement. A distance measuring device characterized in that when the level is reached, the sweep of the drive current is stopped and distance measurement is performed.   2. The distance measuring apparatus according to claim 1, wherein the control unit starts sweeping the drive current from a predetermined low level above a zero level toward a high level.   2. The distance measurement according to claim 1, wherein the controller performs distance measurement while maintaining the level of the drive current for a predetermined time when the amount of light received by the light receiver reaches a level suitable for distance measurement. Distance device.   The range finder according to claim 1, wherein the controller sweeps the drive current exponentially from a low level to a high level.   2. The distance measuring device according to claim 1, wherein the calculation unit performs distance measurement based on a triangulation principle based on a detection signal indicating a light receiving position of a light beam output from the light receiving unit.

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