WO2002048738A1

WO2002048738A1 - Clocking apparatus, clocking method, and range finder

Info

Publication number: WO2002048738A1
Application number: PCT/JP2001/010844
Authority: WO
Inventors: Naoto Inaba
Original assignee: Nikon Corporation
Priority date: 2000-12-15
Filing date: 2001-12-11
Publication date: 2002-06-20
Also published as: JP2002181934A

Abstract

A laser range finder (100) comprising a pulse generating circuit (130) for generating a pulse laser beam repeatedly, a semiconductor laser (112), a photodiode (122) for receiving the laser beam, and a receiving circuit (150). A control circuit (160) measures the light receiving timing based on the count of clock pulses. The laser range finder (100) further comprises a circuit (140) for shifting the irradiation timing of laser beam from the clock pulse at a predetermined interval. Receiving timing of a pulse signal can be measured with a resolution shorter than the generation interval of clock pulse without requiring a high frequency oscillator.

Description

Description Timekeeping device, timekeeping method, and distance measuring device

The present invention relates to a timing device, a timing method, and a distance measuring device, and more particularly, to a timing device that measures the reception timing of a pulse cloud signal. Background art

2. Description of the Related Art Conventionally, there has been known a timing device that measures the reception timing of a pulse signal transmitted at a predetermined timing, for example, based on the transmission timing. As a measuring device using such a timing device, for example, a distance measuring device that irradiates a target with laser light, receives reflected light thereof, and measures the distance to the target has been proposed. In this distance measuring device, the time difference between the emission timing of the laser beam (transmission timing) and the reception timing of the reflected light (reception timing) is obtained from the count value of the clock pulse generated at a constant interval. The distance to the target is calculated based on the calculated time difference (count value) and the speed of the pulsed laser light.

By the way, in the distance device, the measurement accuracy of the time difference is directly connected to the measurement accuracy of the distance. For example, if an oscillator with a clock pulse frequency of 8 MHZ is used, the clock cycle is 12.5 nsec, and the distance measurement resolution corresponding to one clock pulse generation interval takes into account the speed of light. It is about 2 m.

Here, the time difference between the emission timing of the pulsed laser light and the reception timing of the reflected light is obtained as the count value of the clock pulse (sample clock), which improves the accuracy of distance measurement. If there is more It is sufficient to use a clock pulse oscillator with a high frequency. In this case, an IC or the like capable of high-speed signal processing is also required. For example, if an oscillator of about 30 OMHz is used, the resolution of the distance measuring device can be increased to about 50 cm.

However, the higher the frequency, the more expensive the oscillator, and the more likely it is that unwanted electrical radiation will occur, which can lead to malfunctions. Furthermore, ICs that require high-speed processing generate a large amount of heat during operation, and are not suitable for miniaturization of distance measuring devices. Therefore, it has been difficult to increase the resolution of a general-purpose consumer range finder that requires low cost and miniaturization. Disclosure of the invention

The present invention has been made in view of such circumstances, and does not require a high-frequency oscillator or the like, and is capable of measuring the reception timing of a pulse signal with a resolution shorter than a clock pulse generation interval. An object of the present invention is to provide a timing method and a distance measuring device using the same.

To achieve the above object, a timing device according to a first aspect of the present invention includes: a transmitting unit that repeatedly transmits a pulse signal; and A timing unit including a receiving unit for measuring, wherein the transmitting unit transmits the pulse signal while shifting a transmitting timing for the clock pulse at a predetermined interval.

In the present invention, a plurality of count values can be obtained by counting the reception timing based on the clock pulse while shifting the transmission timing of the repeatedly transmitted pulse signal a plurality of times at predetermined intervals. . Since the pulse signal is transmitted while shifting the transmission timing with respect to the clock pulse at predetermined intervals, for example, a pulse that is repeatedly transmitted The signal transmission timing is shifted a plurality of times at predetermined intervals, the received timing is counted based on the clock pulse, and the obtained count values are calculated by statistical processing to obtain the clock pulse. The reception timing can be counted at intervals shorter than the occurrence interval of the reception.

Further, a timing device according to a second invention is a transmitting unit that repeatedly transmits a pulse signal, and a receiving unit that receives the pulse signal and measures reception timing of the pulse signal based on a count value of a clock pulse. Wherein the receiving unit shifts the reception timing at predetermined intervals.

According to the present invention, since the reception timing is shifted at a predetermined interval, for example, the shifted reception timing of the repeatedly transmitted pulse signal is counted based on the clock pulse, and the obtained plurality is obtained. By calculating the count value in the statistical processing, the reception timing can be counted at intervals shorter than the clock pulse generation interval.

Further, the timing device according to a third invention is the timing device according to the first invention or the second invention, wherein the predetermined interval is a fixed interval shorter than a clock pulse period, and the maximum width of the shift is The value is one cycle or more of the clock pulse.

According to the present invention, the pulse signal is shifted at a constant interval shorter than the clock pulse cycle, and the maximum value is one cycle or more of the clock pulse. Therefore, the reception timing is obtained a plurality of times and statistically processed. In this case, appropriate sampling is possible.

Further, the timing device according to a fourth invention is the timing device according to the third invention, further comprising the receiving unit, wherein the reception unit obtains the count value obtained each time the transmission timing or the reception timing is shifted. The reception timing is counted according to the frequency distribution. Further, the timing device according to a fifth invention is the timing device according to the fourth invention, wherein the reception unit further includes a plurality of count values obtained by shifting the pulse signal a plurality of times. (l) to T (m), and when the frequency of occurrence of each count value is N (l) to N (m), the reception timing t of the pulse signal is

t = [N (l) xT (l) + N (2) xT (2) ten ... + N (m) xT (m)]

/ [N (l) + N (2) ten… N (m)]

(However, m and N are integers)

Is determined based on

According to the fourth and fifth inventions, the reception unit counts the reception timing according to the frequency distribution of the count value of the pulse pulse obtained every time the transmission timing is shifted. Therefore, simple statistical processing becomes possible.

A timing device according to a sixth invention is the timing device according to any one of the first invention to the fifth invention, wherein the transmitting unit transmits a pulsed laser light as the pulse signal. A light source unit that irradiates the object with light, the receiving unit includes a light receiving unit that receives the pulsed laser light reflected from the object, and the receiving unit receives timing of the pulsed laser light. Is measured.

According to the present invention, since the time difference between the emission timing and the reception timing of the pulsed laser light can be counted with high accuracy, the time measurement until the transmitted laser light is reflected by the target object and received is performed. The resolution is improved, and the timing accuracy is also improved.

The timekeeping method according to a seventh aspect of the present invention includes: a step of repeatedly transmitting a pulse signal; a step of receiving the pulse signal; and a step of measuring a reception timing of the pulse signal based on a count value of a clock pulse. The transmission timing or reception timing for the clock pulse is shifted at predetermined intervals. And transmitting the pulse signal.

In the present invention, the transmission timing or the reception timing of the repeatedly transmitted pulse signal is shifted a plurality of times at a predetermined interval, and the reception timing is timed based on the clock pulse to obtain a plurality of times. You can get the count value. For example, a pulse signal is transmitted while shifting the transmission timing for a clock pulse at a predetermined interval.For example, the transmission timing of a repeatedly transmitted pulse signal is shifted a plurality of times at a predetermined interval. By counting the reception timing based on the clock pulse, and calculating the obtained count values by statistical processing, the reception timing can be counted at intervals shorter than the clock pulse generation interval. it can.

Further, a distance measuring apparatus according to an eighth aspect of the present invention is a distance measuring apparatus according to the sixth aspect of the present invention, comprising: a timing device configured to measure the reception timing and the light speed of the pulsed laser light to reach the target object. According to the present invention, the time difference between the emission timing of the pulsed laser light and the reception timing can be counted with high accuracy, so that the distance to the target object can be calculated. The resolution of the distance is improved, and the distance measurement accuracy is also improved. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a laser distance measuring apparatus to which the present invention is applied.

FIG. 2 is a block diagram showing the internal configuration of the laser distance measuring device.

FIG. 3 is a circuit diagram showing a configuration of the shift circuit.

FIG. 4 is a timing chart for explaining shift values of light emission timing (transmission timing) by the shift circuit.

Fig. 5 is a timing chart showing how light reception timing (reception timing) is measured when determining the distance to the target. FIG. 6 is a timing chart showing how the light reception timing is measured when the distance to the target is 500 m.

FIG. 7 is a timing chart showing how the light reception timing is measured when the distance to the target is 502 m.

FIG. 8 is a timing chart showing how the light reception timing is measured when the distance to the object is 501 m.

FIG. 9 is a flowchart showing the distance measuring program.

FIG. 10 is a timing chart showing a state of measurement when obtaining the distance to the target object while shifting the reception timing. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 9. FIG. 1 is a perspective view of a laser distance measuring apparatus 100 to which the present invention is applied, and FIG. 2 is a block diagram showing an internal configuration thereof.

As shown in FIG. 1, the laser distance measuring apparatus 100 is provided with a power and distance measurement start button 101 and a mode change button 102 on its upper surface. Further, a laser irradiation window 103 and a laser receiving window 104 are provided on the front surface thereof, and a finder window (not shown) is provided on the rear surface thereof.

Inside the laser distance measuring device 100, a collimating lens 111 is arranged on the side of the laser irradiation window 103, and a condenser lens 121 is arranged on the side of the laser receiving window 104.

As shown in FIG. 2, a semiconductor laser (light emitting element) 112, a pulse generating circuit 130, a shift circuit 130, and a collimating lens 111 are provided inside the laser range finder 100 as shown in FIG. Circuit 140 is arranged. A photodiode (light receiving element) 122 and a receiving circuit 150 are arranged on the side of the condenser lens 121. The control circuit 160 delays the light emission start signal output from the above-described pulse generation circuit 130 by a predetermined shift value using the shift circuit 140, and outputs the signal from the semiconductor laser 112. Laser light is emitted at a predetermined timing (light emission timing).

On the other hand, the control circuit 160 detects the reception timing (reception timing) of the laser beam reflected by the object 1 based on the signal from the reception circuit 150.

The control circuit '160 detects the time difference (t in Fig. 2 (b)) between the light emission timing (transmission timing) and the light reception timing (reception timing) by counting the clock pulse (see Fig. 5). .

Then, the control circuit 160 calculates a distance L from the laser distance measuring apparatus 100 to the object 1 based on the counted time difference and the speed of the laser beam (as a distance calculation unit). function). The control circuit 160 displays this calculation result on the liquid crystal display 170 in the finder.

By the way, the detection of the time difference t is performed by repeatedly generating a pulsed laser beam, and is repeated each time each laser beam is generated. Then, the time difference t obtained a plurality of times is statistically processed to obtain one value (time difference). In this embodiment, when the pulsed laser light is repeatedly emitted a plurality of times, the emission timing (transmission timing) is determined by a predetermined shift value S with respect to a clock pulse for counting the emission timing. Only to shift it. In this embodiment, the transmitting section is constituted by the collimating lens 111, the semiconductor laser 112, the pulse generating circuit 130, the shift circuit 140, and the control circuit 160. The light source section is composed of the collimating lens 111 and the semiconductor laser 112. The receiving unit is composed of a condenser lens 121, a photodiode 122, a receiving circuit 150, and a control circuit 160, of which a condenser lens 121 and a photodiode 122 are formed. Constitutes a light receiving section.

In the laser distance measuring apparatus 100, the emission timing of the laser light is shifted by the shift value S by the operation of the shift circuit 140.

The light emission timing is shifted a plurality of times, but the difference ΔS between the shift values S is shorter than the clock pulse period Tx. The maximum value Sx of the shift value S is equal to or longer than the clock pulse period Tx (see FIG. 5).

Here, the shift circuit 140 includes an analog switch 141, a comparator 142, a capacitor 143, and the like, as shown in FIG. Then, a signal (light emission start signal) from the pulse generation circuit 130 is input to the analog switch 141, and the current Ic flows from the constant current source when the analog switch 141 is turned on by this signal. . A setting voltage Vc for setting shift value S is applied to the other terminal of comparator 142.

FIG. 4 is a timing chart when the light emission timing is delayed by the shift circuit 140.

As shown in this figure, when the analog switch 141 is turned on by the light emission start signal as shown in FIG. Voltage V1 gradually increases as shown in FIG. 4 (b). Then, when V1 exceeds the threshold Vc, the output of the comparator 142 goes high. The time td until the high-level output is generated is the shift value S. Here, the shift value S (time t d) is expressed as follows.

td = CxVc / Ic (C is the capacitance of the capacitor) · '· (1) As described above, the light emission timing (transmission) of the semiconductor laser 112 according to the shift value set voltage Vc by the shift circuit 140 Timing is delayed for a predetermined time td (S). Fig. 5 shows the light emission timing when the light emission timing is changed with different shift values S (SI, S2 to Sx) with respect to the closing pulse, and the target 1 An example of the relationship between the timing of receiving the reflected laser light and the clock pulse is shown. Here, S x = SlO.

When the frequency of occurrence of the count value of the clock pulse obtained at this time (each clock pulse is represented by elapsed time Tl to Tm) is N (l) to N (m), the laser light The reception timing t is obtained by the following equation. t = [N 1 X T 1 + N2X T2 tens ... + NmX T m] / [N 1 + N 2 + ... N m] ... (2)

(However, m and N are integers)

Here, as shown in FIG. 5, it is assumed that the light emission timing (transmission timing) is shifted 10 times within a period Sx slightly longer than the clock pulse period Tx.

The number of pulses at which the reflected light is detected (light receiving timing) depends on the distance L from the laser distance measuring device 100 to the target 1.

Now, the frequency of the oscillator (not shown) of the pulse generator circuit 130 is 80 MHz (period 12.5 nsnsc), the resolution of the laser range finder 100 is 2 m, and the laser range finder Consider the case where the distance L from 100 to the target 1 is 50 Om (Figs. 5 and 6).

At this time, the emission timing of the semiconductor laser 112 is shifted 10 times within the period Sx. It is also assumed that shift values S (SI, S2-Sx) are shifted from each other by a fixed time (difference ΔS).

In this case, suppose that N—the 1st clock pulse (Tn-1) is used once, the 1 + 1st clock pulse (Τη) is used 8 times, and the N + 1st clock pulse (Τn + 1) is used once. If counting is performed (Fig. 6 (a)), the histogram obtained at this time will be as shown in Fig. 6 (b). This measurement result By applying the result to the above equation (2), the reception timing is calculated, and the distance L 1 from the laser range finder 100 to the target 1 (here, 500 m) is calculated. Is calculated.

If the distance L from the laser range finder 100 to the target 1 is shifted from the above distance L 1 (500 m) by exactly one resolution (2 m) (distance L 2 = 5 0 2 m), the reception timing of the laser beam generated 10 times in 10 shifts is as shown in Fig. 7 (a), and the timing is once for the clock pulse (Tn). It is counted eight times by the clock pulse (Tn + 1) and once by the clock pulse (Τη + 2). The histogram obtained at this time is shown in Fig. 7 (b). When this measurement result is applied to the above equation (2), the distance L 1 (here, 502 m) from the laser range finder 100 to the target 1 is calculated through the calculation of the reception timing. Is done.

Thus, if the distance L to the target 1 is an integer multiple of the resolution (for example, 2 m) (for example, 500 m, 502 m-) s histogram, one clock pulse The shape of the histogram is almost the same even though it is shifted. On the other hand, when the distance L from the laser range finder 100 to the object 1 is between the above-mentioned distances L 1 and L 2 (for example, L 3 = 501 m), the shapes are different. A histogram (Fig. 8 (b)) is obtained.

That is, as shown in FIG. 8 (a), if the distance L3 from the laser ranging device 100 to the object 1 is 501 m, the resolution of the laser ranging device 100 is 2 m. Therefore, the count value is a value (Tn or Tn + 1) representing either 500 m or 502 m.

Here, since the light emission timing is shifted 10 times and the laser light is irradiated, the period indicating the light reception timing is equivalent to a clock panel (Tn) corresponding to 500 m, and equivalent to 500 m. It is counted by the clock pulse (Tn + 1). In the example of FIG. 8, since the distance L is the distance L 3 (501 m) exactly in the middle between LI (500 m) and L 2 (502), the laser light irradiated after being shifted ten times The light reception timing is counted five times by the clock pulse Tn and five times by the clock pulse Τη + 1 (histogram in Fig. 8 (b)).

By applying the count value thus obtained to the above equation (2), the value of L3 (501 m) can be obtained through the calculation of the reception timing.

When the distance L3 from the laser range finder 100 to the target 1 is 501 m, since the distance between L1 (500 m) and L2 (502 m) is exactly in the middle, the frequency of occurrence is shown in FIG. As shown in (b), it is divided into 5 times, but if it is closer to any of the distances L 1 (500 m) and L 2 (502 m), the clock pulse Tn and the clock pulse Τη + 1 The number of counts (distribution of the frequency of occurrence) is uneven.

Also in this case, by substituting the obtained count value into the above equation (2), the distance at the point between LI (500 m) and L 2 (502 m) can be calculated by the conventional resolution (2 m). A finer resolution can be obtained.

In the above example, the case where the difference of the shift value S is constant (AS) has been described as an example. However, if the shift value is known in advance, it differs from the equation (2). By using a calculation formula corresponding to a shift value having a changing difference, the distance L can be obtained precisely by calculation. To increase the accuracy of the distance measurement by the laser distance measuring device 100, the number of shifts may be increased and the shift value difference AS may be shortened.

As described above, by shifting the emission timing (transmission timing) of the semiconductor laser 112 to obtain the reception timing with high accuracy, the distance measurement accuracy of the laser distance measuring apparatus 100 is improved. At this time, if the light emission timing is obtained with high accuracy by the same method, the accuracy of distance measurement is further improved. In determining the light emission timing, the light emission of the semiconductor laser 112 is directly detected by the sensor 199 (indicated by a broken line in FIG. 2), and the light emission timing is detected from the time when the light emission timing is actually detected. Starting the counting can increase the measurement accuracy.

FIG. 9 is a flowchart showing a distance measurement program executed by a CPU (not shown) in the control circuit 160 to perform the above-described distance measurement.

When the power and measurement start button 101 provided on the laser range finder 100 is pressed and the power is turned on, first, the counting of clock pulses is started in step S1, and the semiconductor is then started in step S2. The light emission processing of the laser 112 is performed. Here, the light emission timing is shifted by the above-mentioned constant shift value by the shift circuit 140.

In the next step S3, it is determined whether or not the photodiodes 122 detect the laser beam reflected by the object 1. While the determination result is "No", the count of the clock pulse is continued. When the determination result changes to "Yes", the count value of the clock pulse at this time is captured in step S4.

In the next step S5, the histogram is updated using the count value acquired this time, and in the following step S6, it is determined whether or not n (for example, 10) detections have been performed. Is determined.

As long as the determination result of step S6 is "No", steps S1 to S5 described above are repeatedly executed. Then, when the result of the determination in step S6 changes to "Yes", the process proceeds to step S7, and based on the histogram obtained up to this point, the distance from the laser ranging device 100 to the target 1 is increased. The distance L is calculated.

Instead of shifting the transmission timing, for example, as shown in FIG. 10, the reception timing is shifted by a delay circuit that is substantially the same as the shift circuit 140. Alternatively, a signal for counting may be generated (S1 to Sx in FIG. 10). In other words, the actual light receiving pulse is obtained at the timing indicated by light receiving pulse # 1, but at the next light receiving time (indicated by light receiving pulse # 2), this light receiving pulse is obtained. Is delayed by S2 and sent to the next connected processing circuit. Similarly, at the timing indicated by the received light pulse #n, the received light pulse is delayed by Sn and sent to the processing circuit connected next. The terms "shifting the reception timing" and "shifting the reception timing" referred to in the claims and the disclosure of the invention mean that the actually obtained reception timing is delayed. Let it be processed.

Even in such a case, various means as described in the example in which the transmission timing is shifted can be modified and used, and the same effect can be obtained. It will be obvious to those skilled in the art.

Also, in the above-described embodiment, an example has been described in which the laser ranging device 100 counts the light receiving timing of the semiconductor laser 112, but other light emitting elements (eg, LEDs) are used. The present invention is also applicable to the measuring instrument used.

In the above description, the example in which the pulse signal is transmitted while shifting the transmission timing for the clock pulse has been described. Instead, the transmission timing of the clock pulse for the pulse signal is shifted. In this case, the concepts are completely equivalent and fall within the scope of the present invention.

Furthermore, in the above description, the case where the laser beam is measured once for one shift value has been described for the sake of simplicity. Even if the shift value is changed to the maximum shift value while measuring multiple laser beams for one shift value, the reception timing is measured while changing the shift value to the maximum shift value. The cycle may be repeated several times, and by processing this The reliability of the measured values can be improved.

As described above, the present invention is not limited to the scope of the above description, but covers the entire scope of the technical idea of the present invention. Industrial applicability

The timekeeping device and the timekeeping method of the present invention can be used to measure time with high accuracy using an inexpensive configuration. The distance measuring device of the present invention can be used for measuring distance with high accuracy by an inexpensive configuration.

Claims

The scope of the claims

1. A timing device comprising: a transmitting unit that repeatedly transmits a pulse signal; and a receiving unit that receives the pulse signal and measures a reception timing of the pulse signal based on a count value of a clock pulse. A timing unit that transmits the pulse signal while shifting the transmission timing for the pulse at predetermined intervals.

2. A timing device comprising: a transmitting unit that repeatedly transmits a pulse signal; and a receiving unit that receives the pulse signal and measures a reception timing of the pulse signal based on a count value of a clock pulse. A timing unit that shifts reception timing at predetermined intervals.

3. The method according to claim 1, wherein the predetermined interval is a constant interval shorter than a clock pulse cycle, and a maximum value of the shift width is one cycle or more of the clock pulse. 2. The timing device according to 1.

4. The receiving unit counts the reception timing according to a frequency distribution of the count value obtained each time the transmission timing or the reception timing is shifted. The timing device according to paragraph 3,

5. The receiving unit sets the plurality of count values obtained when the pulse signal is shifted a plurality of times to T (l) to T (m), and sets the frequency of occurrence of each count value to N (l ) To N (m), the reception timing t of the pulse signal is t = [N (1) XT (l) + N (2) x T (2) 10 + N (m) x T (m)]

Z [N (1) + N (2) 10… N (m)]

(However, m and N are integers)

The timing device ₍ Claim 4) according to claim 4,

6. The transmitting section includes a light source section that transmits a pulsed laser beam as the pulse signal, and irradiates the object with an object. A light receiving unit that receives the pulsed laser light reflected from an object, wherein the receiving unit measures a reception timing of the pulsed laser light. The timing device according to any one of the five items.

7. A procedure for repeatedly transmitting a pulse signal, a procedure for receiving the pulse signal and measuring a reception timing of the pulse signal based on a count value of a clock pulse, and a procedure for determining a transmission timing or a reception timing for the clock pulse Transmitting the pulse signal while shifting the pulse signal at intervals.

8. The timing device according to claim 6, further comprising: a distance calculating unit that calculates a distance to the object based on the measured reception timing and the light speed of the pulsed laser light. A distance measuring device characterized by the above-mentioned.