JP2011191127A - Time measurement device and sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a time measurement device and sensor device, capable of suppressing degradation of the accuracy of measurement of a time to be measured. <P>SOLUTION: In a time measurement circuit 71 of a control circuit 70 which is adopted in a laser radar device 1, the time T to be measured is acquired on the basis of the ratio of a digital value D1 to a digital value D2, and a reference time To. Moreover, time resolution Tr1 on the occasion of ratio calculation is set so as to be equal to a calculation error e1 on the occasion of the ratio calculation, and is set more finely than the time resolution of the delay element (gate delay) of a ring delay pulse generating circuit 81. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a time measuring device and a sensor device that measure time based on a phase difference between two pulse signals having an arbitrary phase relationship.

  Conventionally, a time A / D conversion circuit shown in Patent Document 1 below is known as a technique related to a time measurement device that measures time based on a phase difference between two pulse signals having an arbitrary phase relationship. This time A / D conversion circuit is a circuit that measures the time difference between two pulses using the delay time of a semiconductor delay element (gate delay) as a resolution, and varies the delay time caused by disturbance (temperature / voltage). It is a circuit for correcting. This time A / D conversion circuit realizes the above correction using the ratio of the reference time data measured under the disturbance environment and the measured time data in order to eliminate the influence of the disturbance.

JP-A-5-37378

  By the way, in the configuration as shown in Patent Document 1, although the influence of the disturbance can be suppressed, an error due to the calculation or the like occurs because the calculation is performed to take the ratio between the reference time data and the measurement time data. Examples of the error include a quantization error caused by a fraction that is rounded down when the reference time and measurement time are quantized into a digital signal, and an arithmetic error caused by a fraction that is rounded down when calculating a correction value. . When the error generated in this way increases, the error included in the measurement time increases, so that not only the measurement accuracy of the measurement time decreases, but also the measurement accuracy such as the distance using the measurement time also decreases. There is a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a time measurement device and a sensor device that can suppress a decrease in measurement accuracy of measurement time.

  In order to achieve the above object, in the time measuring device according to claim 1, the first pulse signal is input and the first pulse signal is passed through the plurality of delay elements, and the first pulse signal is passed through the first pulse signal. A second pulse signal delayed by an arbitrary time with respect to one pulse signal is input, and the passing positions of the plurality of delay elements of the first pulse signal at the input timing of the second pulse signal are specified. A first pulse phase difference encoding means for encoding the arbitrary time as a first pulse phase difference based on the number of delay elements through which the first pulse signal has passed; A pulse signal is input, and the first pulse signal is passed through a plurality of delay elements having the same configuration as the first pulse phase difference encoding means, and only for a reference time with respect to the first pulse signal. The extended second pulse signal is input, and the passage time of the plurality of delay elements of the first pulse signal at the input timing of the second pulse signal is specified, whereby the reference time is set to the first time. Second pulse phase difference encoding means for encoding as a second pulse phase difference based on the number of delay elements through which the pulse signal passes, and the arbitrary time as the first pulse phase difference and the first pulse phase difference. Calculating means based on the ratio of the pulse phase difference of 2 and the reference time, and the calculating means sets the reference time according to the resolution when calculating the ratio. Features.

  According to a second aspect of the present invention, in the time measuring device according to the first aspect, the calculating means calculates the time resolution at the time of the ratio calculation from the time of the delay element derived from the second pulse phase difference and the reference time. It is characterized by being set finer than the resolution.

  The sensor device according to claim 3 includes the time measuring device according to claim 1, and detects the reflected light that is irradiated with the laser beam and reflected by the detection object. The sensor device detects the position of the detected object according to the time difference from the irradiation timing to the detection timing, and the time difference is obtained by sending the first pulse signal to the time measuring device according to the irradiation timing. In addition to the input, the second pulse signal is input to the time measuring device in accordance with the detection timing, and is measured based on the arbitrary time obtained by the computing means.

  According to the first aspect of the present invention, by obtaining an arbitrary time based on the ratio of the first pulse phase difference and the second pulse phase difference and the reference time, the delay time varies due to the delay element due to the disturbance. Even if it occurs, both pulse phase differences change in the same way, so that it is possible to suppress a decrease in measurement accuracy of the arbitrary time, that is, measurement time.

  Further, regarding the relationship between the time resolution at the time of the ratio calculation and the reference time, if the time resolution is made fine in order to reduce the calculation error at the time of the ratio calculation, the time corresponding to one bit of the time measurement data is reduced. The maximum measurement time that can be handled by the calculation of the degree is also reduced. That is, in order to make the time resolution fine, it is necessary to shorten the reference time. On the other hand, in order to reduce the quantization error when quantizing the first pulse phase difference and the second pulse phase difference into a digital signal, it is necessary to lengthen the reference time. Therefore, by setting the reference time so that the total error of the calculation error, quantization error, etc. becomes small according to the time resolution at the time of the ratio calculation, the decrease in measurement accuracy of the measurement time is surely suppressed. can do.

  In the invention of claim 2, since the time resolution at the time of the ratio calculation is set finer than the time resolution of the delay element derived from the second pulse phase difference and the reference time by the calculation means, the calculation at the time of the ratio calculation is performed. Since the error is reliably reduced, it is possible to reliably suppress a decrease in measurement accuracy of the measurement time.

  According to a third aspect of the present invention, the time measuring device according to the first or second aspect is provided, and the time difference for detecting the position of the detected object is determined as the first pulse signal according to the irradiation timing of the laser beam. By inputting the second pulse signal to the time measurement device in accordance with the detection timing of the laser beam as well as being input to the measurement device, the measurement is performed based on an arbitrary time obtained by the calculation means. Thereby, it is possible to realize a sensor device that has enjoyed the functions and effects of the invention of claim 1 such that a decrease in measurement accuracy of the measurement time can be suppressed.

It is sectional drawing which illustrates schematically the laser radar apparatus by which the time measuring circuit which concerns on this embodiment is employ | adopted. FIG. 2 is a block diagram schematically illustrating a circuit configuration of a time measurement circuit in FIG. 1. It is a timing chart which illustrates the 1st and 2nd pulse phase difference. It is a block diagram which illustrates the circuit structure of a pulse phase difference encoding circuit. It is a map which shows the relationship between measurement time (measurement distance) and measurement error. It is a graph which shows the relationship between a reference time and a measurement error. It is a flowchart which illustrates the flow of the time measurement process implemented in a time measurement circuit.

  Hereinafter, an embodiment in which a sensor device employing a time measuring device of the present invention is applied to a laser radar device will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically illustrating a laser radar device 1 in which a time measurement circuit 71 according to the present embodiment is employed. FIG. 2 is a block diagram schematically illustrating the circuit configuration of the time measuring circuit 71 in FIG. FIG. 3 is a timing chart illustrating the first and second pulse phase differences D1 and D2. FIG. 4 is a block diagram illustrating the circuit configuration of the pulse phase difference encoding circuits 72 and 73.

  As shown in FIG. 1, the laser radar device 1 includes a laser diode 10, a photodiode 20 that receives reflected light L3 from a detection object, and a control circuit 70 that controls the laser diode 10 and the photodiode 20. It is configured as a device that detects the distance and direction to a detection object. The laser radar device 1 may correspond to an example of a “sensor device” described in the claims.

  The laser diode 10 emits pulsed laser light (laser light L0) by being supplied with a pulse current from a laser drive circuit (not shown) under the control of the control circuit 70 in accordance with a light emission signal from the control circuit 70.

  The photodiode 20 has a configuration in which when the laser light L0 is irradiated from the laser diode 10, the reflected light L3 reflected by the detection object is detected by the laser light L0, converted into a light reception signal, and output to the control circuit 70. There is no. In addition, about the reflected light from a detection object, the thing of a predetermined area | region is taken in, and in the example of FIG. 1, the reflected light of the area | region between two lines shown with the code | symbol L3 is taken in. .

  A lens 60 and a mirror 30 are provided on the optical axis of the laser beam L0. The lens 60 is configured as a collimating lens, and converts the laser light L0 from the laser diode 10 into parallel light.

  The mirror 30 realizes the transmission of the laser light L0 from the laser diode 10 and the reflection of the reflected light L3 from the detection object side. Specifically, it has a reflection surface 31 that is inclined at a predetermined angle with respect to the optical axis of the laser beam L0, and a through path 32 that intersects the reflection surface 31. In this configuration, the optical axis of the laser light L0 and the optical axis of the reflected light L3 are made to coincide with each other, and the mirror 30 is arranged on the common optical axis and allows the laser light L0 to pass through the through path 32. On the other hand, the reflection surface 31 reflects the reflected light L3 toward the photodiode 20.

  As described above, the lens 60 for converting the laser light L0 into parallel light is provided on the optical path of the laser light L0 from the laser diode 10 to the through path 32. The lens 60 is connected to the through path 32. It is preferable to generate parallel light that allows almost all of the light to pass through. Conversely, when paying attention to the through path 32, the through path 32 may be sized to pass almost all of the laser light L 0 that has been converted into parallel light by the lens 60.

  A rotation deflection mechanism 40 is provided on the optical axis of the laser light L0 that passes through the mirror 30. The rotation deflection mechanism 40 is disposed so as to be rotatable about a central axis extending in the optical axis direction of the laser light L0, and the laser beam L0 is emitted by a concave mirror 41 whose focal position is set on the central axis. The light is reflected toward the space and the reflected light L3 is deflected toward the mirror.

  Further, a motor 50 that rotationally drives the rotation deflection mechanism 40 is provided. The motor 50 is configured to rotate the rotatable concave mirror 41 connected to the shaft 42 by rotating the shaft 42. Here, the motor 50 is constituted by a step motor. Various step motors can be used. If a step motor having a small angle for each step is used, precise rotation is possible. Further, driving means other than the step motor may be used as the motor 50. For example, a servo motor or the like may be used, or a pulsed laser beam may be output in synchronism with the timing when the concave mirror 41 faces the direction in which the distance measurement is desired, and a desired direction can be detected. Good. In this embodiment, as shown in FIG. 1, a rotation angle sensor 52 that detects the rotation angle of the shaft 42 of the motor 50, that is, the rotation angle of the concave mirror 41, is provided. An angle signal corresponding to the rotation angle 41 is output to the control circuit 70. As the rotation angle sensor 52, various types such as a rotary encoder that can detect the rotation angle of the shaft 42 can be used, and the type of the motor 50 to be detected is not particularly limited. Applicable to various types.

  In the present embodiment, the laser diode 10, the photodiode 20, the mirror 30, the lens 60, the rotation deflection mechanism 40, the motor 50, the control circuit 70, and the like are housed in the case 3, and dust and shock protection are achieved. Yes. Around the concave mirror 41 in the case 3, a light guide portion 4 is formed so as to allow the laser light L 0 and the reflected light L 3 to pass therethrough so as to surround the concave mirror 41. The light guide 4 is formed in an annular shape centering on the optical axis of the laser light L0 incident on the concave mirror 41, and is formed over approximately 360 °. The window part 5 which consists of a permeable glass plate etc. is arranged, and dust prevention is achieved.

  The window portion 5 is configured to be inclined over the entire circumference with respect to a virtual plane orthogonal to the optical axis of the laser beam L0 entering the concave mirror 41. In other words, the plate surface is inclined with respect to the laser beam L0 from the concave mirror 41 toward the space. Therefore, even if the laser beam L0 traveling from the concave mirror 41 toward the space is reflected by the window portion 5, it is difficult to become noise light.

  The control circuit 70 is composed of, for example, a microcomputer and a memory (ROM, RAM, EEPROM, etc.), and detects the distance and direction to the detection object by controlling the laser diode 10 and the photodiode 20 described above. It has a function of executing a detection process to be performed and a time measurement process to be described later by a predetermined computer program. In particular, the distance to the detection object is calculated by inputting the first pulse signal and the second pulse signal corresponding to the irradiation timing and detection timing of the laser beam to the time measurement circuit 71 of the control circuit 70. The measurement time for doing this will be measured.

  As shown in FIG. 2, the time measuring circuit 71 includes a first pulse phase difference encoding circuit 72, a second pulse phase difference encoding circuit 73, and an arithmetic circuit 74. As illustrated in FIG. 3, the first pulse phase difference encoding circuit 72 receives the first pulse P1a input according to the laser beam irradiation timing and the first pulse P1a input according to the laser beam detection timing. The phase difference from the second pulse P1b is output as a digital value D1 (first pulse phase difference D1) encoded and digitized. Further, as illustrated in FIG. 3, the second pulse phase difference encoding circuit 73 includes a first pulse P2a input after a predetermined time from the input of the second pulse P1b, and the first pulse P2a. Is output as a digital value D2 (second pulse phase difference D2) obtained by encoding and digitizing a phase difference from a second pulse P2b that is input after a reference time To, which will be described later. . The control circuit 70 and the time measuring circuit 71 may correspond to an example of a “time measuring device” recited in the claims.

The first pulse phase difference encoding circuit 72 and the second pulse phase difference encoding circuit 73 have the same circuit configuration, and this circuit configuration is illustrated in FIG. 4 by taking the first pulse phase difference encoding circuit 72 as an example. It explains using.
As shown in FIG. 4, the first pulse phase difference encoding circuit 72 mainly includes a ring delay pulse generation circuit 81 having a plurality of signal delay circuits (hereinafter referred to as gate delays or delay elements), a counter 82, and a pulse. A gate delay through which the first pulse P1a passes from the middle of the ring delay pulse generation circuit 81 when a first pulse P1a is applied to the input terminal 86. A plurality of delay pulses whose delay time is determined by the number of stages (number of stages) are output and input to the pulse selector 83. Note that the gate delay constituting the ring delay pulse generation circuit 81 can correspond to an example of a “delay element” recited in the claims.

  On the other hand, in the pulse selector 83, when another pulse (second pulse) P1b is input from the input terminal 88 later than the first pulse P1a, the ring delay pulse generation circuit at the stage where the first pulse P1a has reached. Only the input from 81 is selected by the pulse selector 83, and a signal corresponding to the selected input is input to the encoder 84. Then, a binary digital signal corresponding to the encoder input is output from the output 89a of the encoder 84.

  Further, the final end 85 of the gate delay of the ring delay pulse generating circuit 81 is connected so as to return to the OR circuit 81a. As a result, the gate delay is connected in a ring shape, and therefore, with a delay time corresponding to the total gate delay. The first pulse P1a repeatedly returns to the left end of the ring delay pulse generating circuit 81, and the counter 82 indicates how many times the first pulse P1a has made a gate delay by the output of the final end 85, and the above-mentioned bit of the output 89a of the encoder 84 Is output from the output 89b, and the time difference between the pulses P1a and P1b is output as a digital value D1 by these outputs 89a and 89b. The ring delay pulse generation circuit 81 is reset by setting the NAND input 87 to 0 (zero).

  That is, in FIG. 3, the second pulse P1b indicating the detection timing of the laser beam is input to the first pulse phase difference encoding circuit 72 after the first pulse P1a indicating the irradiation timing of the laser beam. Then, a plurality of gate delay passage positions of the first pulse P1a at the input timing of the second pulse P1b are specified, and the input time difference is based on the number of gate delays through which the first pulse P1a has passed. And encoded as a first pulse phase difference. In other words, the first pulse phase difference encoding circuit 72 digitally converts the input time difference with the time resolution by the gate delay as described above, and outputs the digital value D1.

  Also in the other second pulse phase difference encoding circuit 73, the first pulse P2a is input at the timing exemplified in FIG. 3, and input after a reference time To described later from the first pulse P2a. The input time difference up to the second pulse P2b is digitally converted by the time resolution by the gate delay and output as a digital value D2. Here, both the pulse phase difference encoding circuits 72 and 73 are formed on the same chip with the same configuration, and the delay time due to the gate delay varies in the same manner due to variations in temperature and power supply voltage. To do. The digital value D1 and the digital value D2 may correspond to an example of “first pulse phase difference” and “second pulse phase difference” recited in the claims.

Both pulse phase difference encoding circuits 72 and 73 send the digital values D1 and D2 to the arithmetic circuit 74. The arithmetic circuit 74 calculates the input time difference T corresponding to the input of the second pulse P1b according to the detection timing of the laser beam from the input of the first pulse P1a according to the irradiation timing of the laser beam to the digital value D1, Based on the ratio of D2 and the reference time To, calculation is performed by the following equation (1).
T = (D1 / D2) × To (1)
The arithmetic circuit 74 corresponds to an example of “calculation means” described in the claims, and the input time difference T (measurement time T described later) is an example of “arbitrary time” described in the claims. Can correspond to

  Thus, even when there is a disturbance such as temperature and voltage fluctuation, the delay time due to the gate delay of both pulse phase difference encoding circuits 72 and 73 varies in the same way. Even if the resolution) varies, the input time difference T in which the influence of disturbance is suppressed is calculated.

  Next, time measurement processing in the time measurement circuit 71 of the control circuit 70 according to the present embodiment will be described with reference to the drawings. FIG. 5 is a map showing the relationship between measurement time (measurement distance) and measurement error. FIG. 6 is a graph showing the relationship between the reference time To and the measurement error e. FIG. 7 is a flowchart illustrating the flow of the time measurement process performed by the time measurement circuit 71.

  As shown in FIG. 5, as a measurement error when measuring a measurement time (measurement distance), a reference clock quantization error caused by a fraction rounded down when a reference clock is quantized into a digital signal, and a reference clock accuracy are used. An error, a measurement time quantization error due to a fraction that is rounded down when the measurement time or reference time is quantized into a digital signal, and a calculation error including an error when calculating a correction coefficient are assumed. Note that the reference clock quantization error, the error due to the reference clock accuracy, and the correction coefficient calculation error increase as the measurement time (measurement distance) increases. The measurement time quantization error and the calculation error basically include the measurement time. It is not affected by (measurement distance) (see FIG. 5). Therefore, in the time measurement process according to the present embodiment, in order to reduce the measurement error, the reference time To and the time resolution Tr1 at the time of calculating the ratio between the digital values D1 and D2 are set by a setting process described later. The basis for this setting will be described with reference to FIG.

Regarding the relationship between the time resolution Tr1 at the time of the ratio calculation and the reference time To, if the time resolution Tr1 is made fine to reduce the calculation error e1 at the time of the ratio calculation, the time corresponding to one bit of the time measurement data is reduced. The maximum measurement time that can be handled by one calculation is also reduced. That is, in order to make the time resolution Tr1 fine, it is necessary to shorten the reference time To. Here, the calculation error e1 at the time of the ratio calculation when the data width of the time measurement data is n bits is calculated by the following equation (2) based on the reference time To.
e1 = To / (2 ⁿ −1) (2)

On the other hand, in order to reduce the quantization error e2 when the first pulse phase difference and the second pulse phase difference are quantized into digital signals, it is necessary to increase the reference time To. Here, the quantization error e2 is calculated by the following equation (3) based on the planned measurement time Ts, the design gate delay time resolution Tr2, and the reference time To.
e2 = (Ts × Tr2) / To (3)

  Therefore, as shown in FIG. 6, the reference time To is obtained so that the measurement error e totaling the calculation error e1 and the quantization error e2 becomes small according to the time resolution Tr1 at the time of the ratio calculation. By outputting the digital value D2 by the second pulse phase difference encoding circuit 73 using this reference time To, the measurement error e can be reduced. Further, in order to reduce the error in calculating the ratio of the digital values D1 and D2, the time resolution Tr1 at the time of calculating the ratio is set more finely than the time resolution of the delay element derived from the digital value D2 and the reference time To. As a result, the reference time To and the time resolution Tr1 for reducing the measurement error e are set, and a decrease in measurement accuracy of the measurement time can be suppressed.

Hereinafter, the time measurement process in the time measurement circuit 71 of the control circuit 70 will be described in detail with reference to the flowchart of FIG.
First, a reference time setting process is performed in step S101 of FIG. 7, and a reference time To that reduces the measurement error e is set based on the above equations (2), (3), and the like. Next, in step S103, the first pulse phase difference acquisition process is performed, and the first pulse phase difference encoding circuit 72 detects the laser beam from the input of the first pulse P1a according to the irradiation timing of the laser beam. A digital value D1 corresponding to the time until the input of the second pulse P1b according to the timing is calculated and acquired. Subsequently, a second pulse phase difference acquisition process is performed in step S105, and input by the second pulse phase difference encoding circuit 73 after the reference time To set in step S101 from the input of the first pulse P2a. The digital value D2 corresponding to the time until the input of the second pulse P2b is calculated and acquired.

  Next, in step S107, a setting process of the time resolution Tr1 at the time of the ratio calculation is performed. In this processing, the time resolution Tr1 at the time of the ratio calculation is set to be finer than the time resolution of the delay element derived from the digital value D2 and the reference time To. Specifically, the time resolution Tr1 at the time of the ratio calculation is set to be equal to the calculation error e1 at the time of the ratio calculation calculated by the above equation (2) based on the reference time To set at step S101. The

Subsequently, correction coefficient calculation processing is performed in step S109. In this process, the correction coefficient K for correcting the digital value D1 is calculated by the following equation (4) based on the reference time To, the time resolution Tr1 at the time of ratio calculation, and the digital value D2.
K = To / (Tr1 × D2) (4)
In this equation (4), by using the time resolution Tr1 set in step S107, the calculation error when calculating the correction coefficient K, that is, the calculation error when calculating the ratio can be reduced.

In step S111, a measurement time calculation process is performed. In this process, the measurement time T is calculated by the following equation (5) based on the digital value D1, the correction coefficient K, and the time resolution Tr1 at the time of ratio calculation.
T = D1 × K × Tr1 (5)
Here, it is understood that the above formula (1) is obtained by substituting the formula (4) into the formula (5). That is, this time measurement process suppresses the influence of disturbance and suppresses a decrease in measurement accuracy of the measurement time.

Here, the time measurement process described above will be described using specific numerical values.
First, in the setting process of step S101, for example, assuming that the planned measurement time Ts is 200 ns, the time resolution Tr2 of the gate delay is 100 ps, and the data width of the time measurement data is 16 bits, The reference time To is set to 1200 ns by 2), (3), and the like. Next, for example, the digital value D1 is acquired as 1538 by the first pulse phase difference acquisition process in step S103, and for example, the digital value D2 is set to 9230 by the second pulse phase difference acquisition process in step S105. To be acquired. Subsequently, in the setting process of step S107, the time resolution Tr1 at the time of the ratio calculation is set to 20 ps, for example, so as to be equal to the calculation error e1 at the time of the ratio calculation calculated by the above equation (2). Next, in the correction coefficient calculation process in step S109, the correction coefficient K is calculated as 6.5 according to the above equation (4). In the measurement time calculation process in step S111, the measurement time T is calculated as 199.94 ns according to the above equation (5).

  Here, conventionally, assuming that the digital value D1 is acquired as 1538, the time resolution Tr2 of the designed gate delay is 100 ps, and the time resolution of the actual gate delay is 130 ps, the data acquired in units of 130 ps is obtained. By converting it to be expressed in units of 100 ps, 1538 × 130/100 is obtained from 1999, and by expressing this value in time, the measurement time T ′ is calculated from 1999 × 100 ps to 199.9 ns. . Thereby, since the scheduled measurement time Ts is 200 ns, the measurement time calculated by the time measurement process according to the present embodiment has a calculation error of 0.04 ns (= 199) than the conventional time measurement process. .94-199.9), which is smaller.

  As described above, in the time measurement circuit 71 of the control circuit 70 according to the present embodiment, the measurement time T is determined based on the ratio between the digital value D1 and the digital value D2 and the reference time To, resulting in disturbance. Even when the delay time fluctuates due to the gate delay (delay element), the digital values D1 and D2 change in the same way, so that a decrease in measurement accuracy of the measurement time T can be suppressed. Further, since the reference time To is set so that the measurement error e totaling the calculation error e1 and the quantization error e2 at the time of the ratio calculation becomes small according to the time resolution Tr1 at the time of the ratio calculation, the measurement time T It is possible to reliably suppress a decrease in measurement accuracy.

  Further, in the time measuring circuit 71 of the control circuit 70 according to the present embodiment, the time resolution Tr1 at the time of the ratio calculation is set to be equal to the calculation error e1 at the time of the ratio calculation calculated by the above equation (2). Since the time resolution is set to be finer than the time resolution of the delay element, the calculation error at the time of the ratio calculation is reliably reduced, so that a decrease in measurement accuracy of the measurement time T can be reliably suppressed.

  Further, the laser radar device 1 according to the present embodiment includes a time measuring circuit 71 of the control circuit 70, and the time difference for detecting the position of the detected object is expressed by the first pulse according to the irradiation timing of the laser beam. A measurement that is calculated by inputting a signal to the time measurement circuit 71 as a first pulse P1a and inputting a second pulse signal as a second pulse P1b to the time measurement circuit 71 in accordance with the detection timing of the laser beam. Based on the time T, the distance to the detected object is measured. As a result, it is possible to realize a laser radar device that enjoys the functions and effects of each invention, such as the ability to suppress a decrease in measurement accuracy of the measurement time T.

In addition, this invention is not limited to the said embodiment, You may actualize as follows.
(1) The time resolution Tr1 at the time of the ratio calculation is not limited to be set equal to the calculation error e1 at the time of the ratio calculation calculated by the above formula (2), but is derived from the digital value D2 and the reference time To. It may be set finer than the time resolution of the delay element. Even in this case, since the calculation error e1 at the time of the ratio calculation is reduced, it is possible to suppress a decrease in measurement accuracy of the measurement time T.

(2) In the time measurement process, the reference time To may be set in step S101, and the time resolution Tr1 setting process in the ratio calculation in step S107 may be omitted. In this case, since the measurement error e is set to be smaller by the reference time To, the effect is limited as compared with the case where the time resolution Tr1 at the time of the ratio calculation in step S107 is appropriately set. It is possible to suppress a decrease in measurement accuracy of the measurement time T as compared with the time measurement process in FIG.

1 ... Laser radar device (sensor device)
DESCRIPTION OF SYMBOLS 10 ... Laser diode 20 ... Photodiode 70 ... Control circuit (time measuring device)
71 ... Time measuring circuit (time measuring device)
72. First pulse phase difference encoding circuit (first pulse phase difference encoding means)
73. Second pulse phase difference encoding circuit (second pulse phase difference encoding means)
74. Arithmetic circuit (calculation means)
D1: Digital value (first pulse phase difference)
D2: Digital value (second pulse phase difference)
K: Correction coefficient P1a: First pulse (first pulse signal)
P1b ... second pulse (second pulse signal)
T ... Measurement time (arbitrary time)
To ... Reference time Tr1 ... Time resolution during ratio calculation

Claims (3)

The first pulse signal is input to pass the first pulse signal through a plurality of delay elements, and the second pulse signal delayed by an arbitrary time is input to the first pulse signal, By specifying the passage positions of the plurality of delay elements of the first pulse signal at the input timing of the second pulse signal, the arbitrary time is set to the number of delay elements through which the first pulse signal has passed. First pulse phase difference encoding means for encoding as a first pulse phase difference based on;
The first pulse signal is input, and the first pulse signal is passed through a plurality of delay elements having the same configuration as the first pulse phase difference encoding means, and the first pulse signal A second pulse signal delayed by a reference time and specifying a passing position of the plurality of delay elements of the first pulse signal at an input timing of the second pulse signal. A second pulse phase difference encoding means for encoding a second pulse phase difference based on the number of delay elements through which the first pulse signal has passed;
Calculating means for calculating the arbitrary time based on the ratio of the first pulse phase difference and the second pulse phase difference and the reference time;
The time calculating device is characterized in that the calculating means sets the reference time according to a resolution when calculating the ratio.   The said calculating means sets the time resolution at the time of the said ratio calculation more finely than the time resolution of the said delay element derived | led-out from the said 2nd pulse phase difference and the said reference time. Time measuring device. A time measuring device according to claim 1 or 2,
A sensor device that detects a position of the detection object according to a time difference from an irradiation timing to a detection timing by irradiating a laser beam and detecting reflected light reflected by the detection object.
The time difference is calculated by inputting the first pulse signal to the time measuring device according to the irradiation timing and inputting the second pulse signal to the time measuring device according to the detection timing. The sensor device is measured based on the arbitrary time obtained by the means.

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