JP2757638B2 - Inter-vehicle distance detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting a pulsed light signal, receiving a reflected pulsed light signal from an illuminated obstacle, and measuring a time required for the reciprocation to reach the obstacle. The present invention relates to an inter-vehicle distance detecting device used for a vehicle or the like for detecting a distance or the like.

[0002]

2. Description of the Related Art FIG.
1 shows a configuration of a conventional inter-vehicle distance detecting device shown in Japanese Patent Application Laid-Open Publication No. HEI 9-209, in which 1 is a pulse generator for generating a transmission pulse signal, 2 is a light emitting element (laser diode or the like), a driving circuit thereof, and a lens system. A light transmitter for transmitting a pulse light signal to the light source 3 is composed of a light receiving element (such as a photodiode) and a lens system, receives a reflected pulse light signal from an illuminated front obstacle, and performs photoelectric conversion for reception. The light receiver 4 for outputting a pulse signal is a broadband amplifier having a bandwidth determined by the pulse width of the pulse light signal.

[0005] 5 is a sweeper 6, a sample pulse generator 7,
A sampling processor which comprises a sample-and-hold unit 8 and a low-frequency amplifier 9 and sequentially samples and holds a signal level at a point corresponding to a distance of 0 m of the received pulse signal as a high-frequency signal and converts the signal level into a low-frequency signal; Reference numeral 10 denotes a signal comprising a level determiner 11, a counter 12, a reference clock 13, and a microcomputer 14, and a signal for detecting a distance to an obstacle or the like by performing a level determination for each signal level converted into a low frequency signal by the sampling processor 5. It is a processor.

Next, the operation of the above configuration will be described.
The pulse generator 1 generates a transmission pulse signal, and the light transmitter 2 converts the transmission pulse signal into a pulse light signal and transmits the light forward. The light receiver 3 receives a reflected pulse light signal having a delay time corresponding to a round trip time to a preceding obstacle irradiated with the pulse light signal, photoelectrically converts this, and outputs a reception pulse signal. The broadband amplifier 4 amplifies the received pulse signal. On the other hand, the sweeper 6 generates a sample timing signal and a sample start signal.
A sample start signal is generated when a signal level at a point corresponding to a distance of m is sampled and held.

The sweeper 6 generates a sample timing signal so that the delay time from generation of the transmission pulse signal from the pulse generator 1 to generation of the sample timing signal gradually increases linearly. In this delay time, a sweep is performed periodically (every low frequency ranging cycle) from a time corresponding to a distance of 0 m to a time corresponding to the maximum detection distance (for example, a range of about 667 ns for a distance of 100 m). Works. Also, the sample pulse generator 7
Receives a sample timing signal, generates and outputs a sample pulse signal.

The sample and hold unit 8 samples and holds the signal level of one point of the received pulse signal amplified by the wideband amplifier 4 based on the delay time of the sample pulse signal and converts the signal level into a low frequency signal. The low frequency amplifier 9 has a narrow band and high gain, and amplifies the signal level converted into the low frequency signal. The level determiner 11 compares the low-frequency signal amplified by the low-frequency amplifier 9 with a predetermined level to determine whether or not the signal is a reflected pulse light signal from a preceding obstacle, and outputs a detection signal. The counter 12 counts the reference clock signal from the reference clock 13, starts counting based on the sample start signal, and ends counting based on the detection signal from the level determiner 11. The microcomputer 14 has a counter 1
The distance and the like are measured based on the result of 2.

Next, as a detailed description of the operation of the sweeper 6, a configuration diagram and a signal waveform diagram of the sampling processor 5 of the conventional inter-vehicle distance detecting device disclosed in Japanese Patent Application Laid-Open No. 51-40092 will be described. 11 and FIG. The sweeper 6 includes a frequency divider 16, a low-speed sawtooth generator 17, a high-speed sawtooth generator 18, and a high-speed comparator 19.

Next, the operation of the configuration shown in FIG. 11 will be described with reference to FIG. First, the input transmission pulse signal a is supplied to the frequency divider 16 to generate a distance measurement cycle signal b having a period T ₀ which is N times the period t ₀ of the transmission pulse signal a and synchronized with the transmission pulse signal a. The ranging cycle signal b is applied to a low-speed sawtooth wave generator 17 to generate a low-speed sawtooth signal c, and the transmission pulse signal a is applied to a high-speed sawtooth wave generator 18 to generate a high-speed sawtooth signal d. .

Next, the low-speed saw-tooth wave signal c and the high-speed saw-tooth wave signal d are supplied to a high-speed comparator 19, and the magnitudes of the two are compared (for example, the high-speed saw-tooth wave signal d is larger than the low-speed saw-tooth wave signal c). by.) to output a pulse when it has, the sample timing signal is obtained delay time from the transmission pulse signal a is gradually increased T ₀ as one cycle. Then, by giving this sample timing signal to the sample pulse generator 7, the pulse width of the transmission pulse signal a is smaller than that of the transmission pulse signal a.
The time t _m from which the delay time t _d corresponds to the maximum detection distance
, And a sample pulse signal e whose change period of the delay time t _d is T ₀ is obtained.

[0010]

The conventional inter-vehicle distance detection apparatus is configured as described above, and uniformly changes the delay time from the transmission of a pulse light signal to the generation of a sample pulse signal. In order to obtain distance information to an obstacle with high accuracy, it is necessary that the linearity and inclination of each of the low-speed and high-speed sawtooth signals are accurate. However, considering the variation in the values of individual elements used in the circuit and temperature changes, it is difficult to realize them easily, and the circuit is complicated (the number of elements is increased, the number of adjustment points is increased, and advanced circuit technology is required). And it becomes expensive.

Further, since the detection judgment is performed by sequentially sampling and holding from the signal level corresponding to the distance of 0 m of the received pulse signal, it takes time to finish viewing the entire measurement range. There is a problem that the maximum detection distance that can be measured during the distance measurement period or its resolution is limited.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the invention of claim 1 is to freely sample and hold a reception pulse signal corresponding to an arbitrary distance to detect and judge a received pulse signal. An object of the present invention is to provide an inter-vehicle distance detecting device which can detect a distance to an object, has a simple circuit configuration for the purpose, and has few adjustment points.

According to the second aspect of the present invention, distances to obstacles in all measurement ranges can be accurately detected with higher resolution without reducing the maximum detection distance. An object is to obtain a small inter-vehicle distance detection device.

Further, according to the invention of claim 3, the distance to the obstacle can be detected with high resolution and with high resolution only within an arbitrary measurement range without reducing the maximum detection distance, and the circuit configuration therefor is simple and the adjustment point is small. It is an object of the present invention to obtain an inter-vehicle distance detection device having a small distance.

[0015]

An inter-vehicle distance detecting apparatus according to a first aspect of the present invention generates a sample pulse signal and sets a delay time from when a pulse light signal is transmitted to when a sample pulse signal is generated. A sample pulse generating means which can be controlled by an arbitrary digital value, a means for sampling and holding a received pulse signal by the sample pulse signal,
There are provided means for comparing the sampled and held signal level with a predetermined level to determine a level, and means for detecting a distance to an obstacle based on the digital value and the result of the level determination at that time.

According to a second aspect of the present invention, there is provided an inter-vehicle distance detecting apparatus which can control a delay time from transmission of a pulse light signal to generation of a sample pulse signal by an arbitrary digital value. Means for sampling and holding the received pulse signal by the sample pulse signal;
Means for comparing the sampled and held signal level with a predetermined level to determine a level, means for sequentially increasing or decreasing the digital value, and means for determining whether or not there is an obstacle based on the digital value and the level determination result at that time. Means is provided for detecting the distance and reducing the amount of addition or subtraction of the digital value near the detected distance to newly detect the distance to the obstacle.

According to a third aspect of the present invention, there is provided an inter-vehicle distance detecting apparatus which can control a delay time from transmission of a pulse light signal to generation of a sample pulse signal by an arbitrary digital value. Means for sampling and holding the received pulse signal by the sample pulse signal;
Means for comparing the sampled and held signal level with a predetermined level to determine the level; and adding and subtracting the digital value from the reference distance equivalent value in order so that the distance is small and the outside of the range is large. There are provided a means for setting a digital value, and a means for detecting a distance to an obstacle based on the digital value and the level determination result at that time.

[0018]

According to the first aspect of the invention, the delay time from the transmission of the pulse light signal to the generation of the sample pulse signal is controlled by an arbitrary digital value. Further, the received pulse signal is sampled and held by the sample pulse signal, a level is determined by comparing the sampled and held signal level with a predetermined level, and a distance to an obstacle is detected based on the digital value and the level determination result.

According to the second aspect of the present invention, the delay time from the transmission of the pulse light signal to the generation of the sample pulse signal is controlled by an arbitrary digital value, and this digital value is sequentially increased or decreased. The received pulse signal is sampled and held by the sample pulse signal, and the level of the sampled and held signal is determined. Further, the distance to the obstacle is detected from the digital value and the level determination result at that time, and the distance to the obstacle is detected again by reducing the amount of addition or subtraction of the digital value near the detected distance.

According to the third aspect of the present invention, the delay time from the transmission of the pulsed optical signal to the generation of the sample signal is controlled by an arbitrary digital value. Outside is greatly added and subtracted. The received pulse signal is sampled and held by the sample pulse signal, and the level of the sampled and held signal is determined. Further, the distance to the obstacle is detected from the digital value and the level determination result at that time.

[0021]

【Example】

Embodiment 1 FIG. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of an inter-vehicle distance detecting apparatus according to a first embodiment, 1 is a pulse generator for generating a transmission pulse signal of 10.24 KHz, and 6 is a sample timing signal generated from a transmission pulse signal inputted as a trigger signal. This is a programmable sweeper that can set the delay time up to any 16-bit digital value. The delay time per 1-bit digital value is a time width equivalent to a distance of 5 cm (about 334 ps).
Is set to 11 is a level determiner that compares the signal level of one point of the received pulse signal sampled and held by the sampling processor 5 with a predetermined level, and outputs a detection signal as an “H” level when the signal level is higher than the predetermined level; Divide the transmission pulse signal by 1024 to 10Hz
Is a frequency divider that generates a distance measurement cycle signal. Other configurations are the same as the conventional one.

Next, the operation of the above configuration will be described.
The light transmitter 2 converts the transmission pulse signal from the pulse generator 1 into a pulse light signal and transmits the light forward. The light receiver 3 receives a reflected pulse light signal having a delay time corresponding to a round trip time of light to a preceding obstacle irradiated with the pulse light signal. The broadband amplifier 4 amplifies the received pulse signal photoelectrically converted by the light receiver 3.

The programmable sweeper 6 delays and generates a sample timing signal from a transmission pulse signal in accordance with a digital value set by the microcomputer 14. The sample pulse generator 7 receives the sample timing signal, generates and outputs a sample pulse signal. The sample hold unit 8 samples and holds the signal level of one point of the received pulse signal amplified by the wideband amplifier 4 based on the delay time of the sample pulse signal, and converts the signal level into a low frequency signal. The low frequency amplifier 9 has a narrow band and high gain, and amplifies the signal level converted into a low frequency signal.

The level determiner 11 compares the low-frequency signal amplified by the low-frequency amplifier 9 with a predetermined level to determine whether or not the signal is a reflected pulse light signal from a preceding obstacle, and outputs a detection signal. I do. The microcomputer 14 starts one ranging cycle in synchronization with the rising of one ranging cycle signal of 10 Hz, updates a digital value every 10.24 KHz, and measures a distance or the like based on the detection signal.

Next, the operation of the microcomputer 14 will be described in detail. The microcomputer 14 uses the first 50 ms of the 10 Hz ranging cycle signal for the ranging period of the maximum detection distance 100 m and the second 50 ms for data processing according to the processing content of one 10 Hz ranging cycle (100 ms) shown in FIG. And operates as a transfer period.
5 in the 10.24 KHz interrupt during the 50 ms ranging period
In order to measure the maximum detection distance 100m using 00 times, the delay time per digital value bit is a time width equivalent to a distance of 5cm with the distance resolution set to 20cm, so the digital value is 4 bits for one interrupt. It operates so that it is set by adding each time.

Next, the operation of the microcomputer 14 will be described with reference to the flowcharts of FIGS. First,
In step 31, initial processing of the following distance detecting device,
The interruption processing of the 10 Hz one distance measurement cycle signal is permitted, and the addition amount of the digital value is set to 4 bits so as to obtain a distance resolution of 20 cm. In step 32, the synchronization flag, the detection point data, the detection flag, and the digital value are each set to 0 for initialization of one ranging cycle. In step 33, the digital value is output to the programmable sweeper 6, and the delay time is set to 0. Initialize to

In step 34, the process waits until the synchronization flag is set by an interrupt process using a 10-Hz distance measurement cycle signal. In step 35, an interrupt process of 10.24 KHz is permitted. In step 36, the process waits until a distance up to the maximum detection distance of 100 m is measured by an interrupt processing of 10.24 KHz.
Based on the number of interrupts 500 of 0.24 KHz and the added amount of the digital value per interrupt of 4 bits, 2000 bits are determined as a distance equivalent value of the maximum detection distance of 100 m by comparing with the digital value. In step 37, the interrupt processing of 10.24 KHz is prohibited, and in step 38, the detected point data is converted into the distance by the formula (1) and output. Thereafter, the process returns to step 32 to process the next distance measurement cycle. Distance to obstacle (cm) = Detection point data (bit) x 5 (cm / bit) (1)

In step 41 of FIG. 4, the synchronization flag is set to 1 in order to synchronize one ranging cycle every interruption of a 10 Hz one ranging cycle signal. Further, in step 51 of FIG. 5, when the detection flag is 1, it is determined that an obstacle has already been detected in this distance measurement cycle, and the process proceeds to step 54; otherwise, the process proceeds to step 52.

In step 52, when the detection signal is at "H" level, it is determined that the signal level of one point of the received pulse signal sampled and held based on the delay time is a reflected pulse light signal from a preceding obstacle, Proceed to step 53, and if not "H" level, proceed to step 54. In step 53, since it is determined that an obstacle has already been detected, the digital value at that time is stored as detection point data, and the detection flag is set to 1. Step 54
Then, in the next interrupt processing, the set addition amount is added to the digital value in order to measure a distance that is farther from the currently measured distance by the resolution. In step 55, a digital value is output to the programmable sweeper 6, and the delay time is reset.

According to the first embodiment, since the programmable sweeper 6 capable of controlling the delay time with an arbitrary digital value is used, the accuracy of the delay time is increased, and the sampled and held reception pulse signal can be accurately and stably held. The circuit configuration for this can be simplified, and the number of adjustment points is reduced. In addition, obstacle detection can be determined from an arbitrary distance, and the distance to the obstacle can be accurately measured.

Embodiment 2 FIG. Next, the operation of the microcomputer 14 according to the second embodiment will be described. The configuration of the inter-vehicle distance detecting device is the same as that of FIG. The microcomputer 14 sets the first 20 ms of the first 50 ms of the 10 Hz ranging cycle signal as a period for roughly measuring the range of 100 m of the maximum detection distance in accordance with the processing content of one ranging cycle of 10 Hz shown in FIG. The next 10 ms is a period for preventing the roughness of the signal waveform of the sampled and held low-frequency signal, and the remaining 20 ms is 10 m between 5 m before and after the detected distance only when the distance to the obstacle can be detected in the first 20 ms. It operates to re-measure the range in detail again, and
It operates to use 0 ms for data processing and transfer periods.

Then, 1 enters the first 20 ms ranging period.
To measure the maximum detection distance of 100 m using 200 out of 0.24 KHz interrupts, set the distance resolution to 50 m.
Since the delay time per bit of the digital value is a time width equivalent to a distance of 5 cm as cm, the digital value is added to each interrupt by 10 bits and set. Similarly, in order to re-measure the range of 10 m in detail in the remaining 20 ms, the resolution of the distance is set to 5 cm, and the digital value is added one bit at a time to one interrupt and set.

Next, the operation of the microcomputer 14 will be described with reference to the flowchart of FIG. First, in step 71, the initial processing of the inter-vehicle distance detection device and the 10 Hz
Of the distance measurement cycle signal is permitted.
In step 72, each of the synchronization flag, the detection point data, the detection flag, and the digital value is set to 0 for initialization of one ranging cycle. In step 73, a digital value is output to the programmable sweeper 6 to initialize the delay time to 0. In step 74, the process waits until the synchronization flag is set by an interrupt process using a 10 Hz distance measurement cycle signal.

In step 75, the digital value addition amount is set to 10 bits so as to obtain a distance resolution of 50 cm, and interrupt processing at 10.24 KHz is permitted. In step 76, the processing waits until the maximum detection distance of 100 m is measured by the interrupt processing of 10.24 KHz.
From the number of interruptions of 10.24 KHz in the distance measurement period of 200 and the added amount of the digital value per interruption of 10 bits, 2000 bits are determined by comparing with the digital value as the distance equivalent value of the maximum detection distance of 100 m.

In step 77, the interrupt processing of 10.24 KHz is prohibited, and in step 78, the pulse light signal is not transmitted for 10 ms in order to suppress the roughness of the reception pulse signal waveform which is the sampled and held low frequency signal. And wait only for sample hold

In step 79, when the detection flag is 0, it is determined that no obstacle has been detected during the first 20 ms distance measurement period, and the routine proceeds to step 86. If the detection flag is not 0, the routine proceeds to step 80. In step 80, a value obtained by subtracting 100 bits corresponding to the distance of 5m from the detected point data is set as a digital value and the detection flag is set to 0 in order to re-measure the distance in detail from 5m before the previously detected distance. . In step 81, a digital value is output to the programmable sweeper 6, and the delay time is returned to 5 m before. Step 82
In this example, the addition amount of the digital value is set to 1 bit in order to obtain a distance resolution of 5 cm, and an interrupt processing of 10.24 KHz is permitted.

In step 83, the distance range of 10 m is set to 10.
It waits for measurement by 24KHz interrupt processing. This is a 20ms distance measurement period. From the number of interrupts of 10.24KHz 200 and the addition amount of digital value per interrupt 1bit, 200bit is equivalent to 10m distance value. Is determined by comparing with a digital value. In step 84, 1
The interrupt processing of 0.24 KHz is prohibited, and in step 85, the detection point data is converted into a distance by the formula (1) and output. Thereafter, the flow returns to step 72 to process the next distance measurement cycle. In step 86, since there is no obstacle, distance measurement is not performed, but a wait of 20 ms is made to adjust the data transfer timing. The interrupt processing at 10 Hz and 10.24 KHz is the same as in the first embodiment.

According to the second embodiment, since the programmable sweeper 6 whose delay time can be controlled by an arbitrary digital value is used, the accuracy of the delay time is improved, and the sampling and holding of the received pulse signal is performed accurately and stably. Can be.
Further, the circuit configuration for this is simple, and the number of adjustment points is reduced.
Furthermore, after roughly measuring the distance to the obstacle at a low resolution, when an obstacle is detected, the vicinity of the detected distance is measured at a high resolution, so the entire detection range can be measured without reducing the maximum detection distance. The distance to the obstacle can be accurately detected with high resolution.

Embodiment 3 FIG. Next, the operation of the microcomputer 14 according to the third embodiment will be described. The configuration of the inter-vehicle distance detecting device is the same as that of FIG. Microcomputer 14
Operates so as to use the first 50 ms of the 10 Hz ranging cycle signal in the ranging period of the maximum detection distance 100 m according to the processing content of one 10 Hz ranging cycle shown in FIG. Operate to use during the period.

The third embodiment is an example in which the resolution up to the first 20 m of the 100 m measurement range is set to 10 cm, and the resolution after that may be lower. Therefore, up to the first 200 interrupts of 10.24 KHz that enter the 50 ms distance measurement period, add two bits of digital value to each interrupt so that the delay time is changed every time width equivalent to a distance of 10 cm. The remaining distance 80 m after 20 m is set to 267.
It operates so that the distance resolution is set to 30 cm by using one interrupt and the digital value is added to each interrupt by 6 bits.

Next, a description will be given with reference to the flowchart of FIG. First, in step 91, the initial processing of the inter-vehicle distance detection device and the interruption processing of a 10 Hz one distance measurement cycle signal are permitted. In step 92, each of the synchronization flag, the detection point data, the detection flag, and the digital value is set to 0 in order to initialize one ranging cycle.
Then, a digital value is output to the programmable sweeper 6, and the delay time is initialized to zero.

In step 94, the process waits until the synchronization flag is set by an interrupt process using a 10 Hz distance measurement cycle signal. In step 95, the digital value addition amount is set to 2 bits in order to obtain a distance resolution of 10 cm. Enable 24KHz interrupt processing. In step 96, the process waits until the distance range of 20m is measured by the interrupt processing of 10.24 KHz. This is equivalent to the number of interrupts 200 of 10.24 KHz and the addition amount of the digital value per one interrupt during the 20 ms distance measurement period. From 2 bits, 400
Bit is determined as a distance equivalent value of 20 m by comparing with a digital value.

In step 97, the interrupt processing of 10.24 KHz is prohibited. In step 98, when the detection flag is 1, it is determined that an obstacle has been detected during the first 20 m of the distance measurement period, and the process proceeds to step 102. If is not 1, go to step 99. In step 99, the addition amount of the digital value is set to 6 bits in order to obtain a resolution of 30 cm at a distance (80 m) after 20 m, and an interrupt processing of 10.24 KHz is permitted.

In step 100, the process waits until a distance range of 80 m is measured. This is based on the number of interrupts 267 of 10.24 KHz and the addition amount of digital value per interrupt of 6 bits, which is 1602 bits, during the 80 m distance measurement period. 8
It is determined by comparing with a digital value as a distance equivalent value of 0 m. In step 101, the interrupt processing of 10.24 KHz is prohibited, and in step 102, the detected point data is converted into a distance by the formula (1) and output. Thereafter, the flow advances to step 92 to process the next distance measurement cycle. In addition, 10
Interrupt processing of Hz and 10.24KHz is the first embodiment.
Is the same as

According to the third embodiment, since the programmable sweeper 6 whose delay time can be controlled by an arbitrary digital value is used, the accuracy of the delay time is improved, and the sampling of the received pulse signal can be performed accurately and stably. it can. Further, the circuit configuration for this is simple and the number of adjustment points is reduced. Furthermore, since the distance resolution is increased only in an arbitrary measurement range and is reduced outside the range to detect the distance, the distance to an obstacle in an arbitrary measurement range can be accurately detected with a high resolution without reducing the maximum detection distance. Can be detected.

In each of the above embodiments, a description is given of a case where a transmission pulse signal of 10.24 KHz, a distance measurement cycle signal of 10 Hz, a distance measurement period of 50 ms, a data processing and transfer period of 50 ms, and a maximum detection distance of 100 m. However, of course, it is not limited to this. In addition, the reception pulse signal 0
A case has been described in which the detection and determination is performed by sequentially sampling and holding from the signal level of the point corresponding to the distance of m, or the digital value is set so that the addition amount of the digital value is fixed and the digital value is sequentially and uniformly increased. , 0m or 10
The measurement may be started from the signal level of a point corresponding to an arbitrary distance such as m, the amount of addition of the digital value may be changed arbitrarily, and the setting may be performed in any order. You may. Further, the digital value may be set not by the addition amount but by the subtraction amount.

[0047]

As described above, according to the first aspect of the present invention,
The sample pulse signal is emitted after the pulse light signal is transmitted.
The delay time before generation can be controlled by an arbitrary digital value, and this digital value can be freely set to a value equivalent to an arbitrary distance, so that the circuit configuration is simplified and the number of adjustment points is reduced. In addition, the distance to the obstacle can be accurately detected, and the distance to the obstacle at an arbitrary distance can be quickly measured or the arbitrary distance range can not be measured.

According to the second aspect of the present invention, the delay time can be controlled by an arbitrary digital value, and the distance to the obstacle is roughly measured at a low resolution by increasing the amount of addition / subtraction of the digital value. Then, when an obstacle is detected, the vicinity of the previously detected distance is measured with high resolution by reducing the amount of addition and subtraction of the digital value, so that the circuit configuration can be simplified and the number of adjustment points can be reduced. ,
It is possible to accurately detect distances to obstacles in all measurement ranges with higher resolution without reducing the maximum detection distance.

According to the third aspect of the present invention, the delay time can be controlled by an arbitrary digital value, and the resolution can be increased by reducing the amount of addition and subtraction of the digital value in an arbitrary measurement range. Since the outside is measured in reverse, the circuit configuration is simple, the number of adjustment points can be reduced, and only the distance to an obstacle in an arbitrary measurement range can be detected with high resolution with high resolution without reducing the maximum detection distance be able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a device of the present invention.

FIG. 2 is a processing content diagram of one ranging cycle of the microcomputer according to the first embodiment of the present invention;

FIG. 3 is a flowchart showing a main routine processing operation of the microcomputer according to the first embodiment of the present invention;

FIG. 4 shows a 10 Hz microcomputer of the apparatus of the present invention.
9 is a flowchart illustrating an interrupt processing operation.

FIG. 5 shows a microcomputer 10.2 of the apparatus of the present invention.
It is a flowchart which shows a 4KHz interrupt processing operation.

FIG. 6 is a processing diagram of a distance measurement cycle of a microcomputer according to a second embodiment of the present invention.

FIG. 7 is a flowchart showing a main routine processing operation of the microcomputer according to the second embodiment of the present invention.

FIG. 8 is a processing content diagram of one ranging cycle of a microcomputer according to Embodiment 3 of the present invention.

FIG. 9 is a flowchart showing a main routine processing operation of a microcomputer according to a third embodiment of the present invention;

FIG. 10 is a configuration diagram of a conventional device.

FIG. 11 is a configuration diagram of a conventional sampling processor.

FIG. 12 is a signal waveform diagram of a conventional sampling processor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pulse generator 2 light transmitter 3 light receiver 5 sampling processor 6 programmable sweeper 7 sample pulse generator 8 sample and hold device 10 signal processor 11 level judgment device 15 frequency divider

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yuichi Wakiwaki 8-1-1, Tsukaguchi-Honmachi, Amagasaki-shi, Hyogo Mitsubishi Electric Corporation Industrial System Research Laboratories (56) References JP-A-57-141575 (JP, A) JP 60-30902 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01S 7/48-7/51 G01S 17/00-17/95 G01B 11/00- 11/04

Claims (3)

(57) [Claims] A means for transmitting a pulsed light signal; a means for receiving a reflected pulsed light signal from an obstacle irradiated with the pulsed light signal;
A sample pulse signal generating means for generating a sample pulse signal, and controlling a delay time from the transmission of the pulse light signal to the generation of the sample pulse signal by an arbitrary digital value, and a reception pulse signal by the sample pulse signal. Means for performing sample and hold, means for performing a level determination by comparing the sampled and held signal level with a predetermined level, and means for detecting a distance to an obstacle based on the digital value and the result of the level determination at that time. An inter-vehicle distance detecting means provided. Means for transmitting a pulsed light signal, means for receiving a reflected pulsed light signal from an obstacle irradiated with the pulsed light signal, photoelectrically converting the reflected light signal, and outputting a received pulse signal;
A sample pulse signal generating means for generating a sample pulse signal, and controlling a delay time from the transmission of the pulse light signal to the generation of the sample pulse signal by an arbitrary digital value, and a reception pulse signal by the sample pulse signal. Means for sampling and holding, means for comparing the sampled and held signal level with a predetermined level to determine the level, and adding and subtracting the digital value from the reference distance equivalent value so as to increase and decrease sequentially. A means for setting a digital value, and a distance to an obstacle is detected based on the digital value and the level determination result at that time.Around the detected distance, the amount of addition and subtraction of the digital value is reduced to reach the obstacle again. An inter-vehicle distance detecting device comprising means for detecting the distance of the vehicle. 3. A means for transmitting a pulsed light signal, a means for receiving a reflected pulsed light signal from an obstacle irradiated with the pulsed light signal, photoelectrically converting the reflected pulsed light signal, and outputting a received pulse signal;
A sample pulse signal generating means for generating a sample pulse signal, and controlling a delay time from the transmission of the pulse light signal to the generation of the sample pulse signal by an arbitrary digital value, and a reception pulse signal by the sample pulse signal. Means for sampling and holding, means for comparing the sampled and held signal level with a predetermined level to determine a level, and a reference distance equivalent value for increasing or decreasing the amount of addition or subtraction of the digital value in an arbitrary distance range and increasing outside the range. And a means for setting a digital value so as to increase and decrease sequentially by adding and subtracting from the distance, and a means for detecting a distance to an obstacle based on the digital value and a level determination result at that time. Distance detection device