JP5191107B2 - Ranging device - Google Patents

Description

  The present invention relates to a distance measuring device, and more particularly to a distance measuring device that measures a distance from a target using light.

Ranging devices that measure the distance to a target are used in many industrial products, for example, when a camera is used to measure the distance to a subject. An apparatus for measuring such a distance is disclosed in Patent Documents 1 to 3.
JP 2002-341030 A Japanese Patent Laid-Open No. 5-288858 JP-A-5-100026

  In any of the above-mentioned patent documents, the circuit for acquiring the light emission timing and the circuit for acquiring the light reception timing are different circuits. Measurement accuracy decreases due to changes in characteristics. In addition, measurement accuracy may be reduced due to the influence of external light.

  As described above, the conventional technique has a problem that the measurement accuracy is lowered and a high-accuracy distance from the target may not be obtained.

  In view of the above problems, an object of the present invention is to provide a distance measuring device that can obtain a distance from a target with high accuracy.

In order to achieve the above object, the first invention is a light receiving means for receiving light and outputting a signal of a level corresponding to the intensity of the light, and a first light emitting means for directly emitting light to the light receiving means. Based on the signal output from the light receiving means, the second light emitting means for emitting light to the target and the timing at which the light receiving means has received so that the light receiving means can receive the reflected light from the target. And control means for controlling start and stop of light emission of the first light emitting means and the second light emitting means,
The control means acquires the first timing at which the light receiving means has received light by causing the first light emitting means to emit light, stops light emission of the first light emitting means, and then the first light emission. Reflection by causing the second light emitting means to emit light by outputting a light emission signal for causing the second light emitting means to emit light after a lapse of a predetermined time from the output of the light emission signal to the first light emitting means for starting the light emission of the means. The second timing when the light receiving means receives light is acquired, and the second timing is acquired from the acquisition of the first timing based on the first timing, the second timing, and the predetermined time. The distance to the target is calculated by the difference obtained by subtracting the predetermined time from the time until .

Here, in the first invention, the light receiving means receives light, outputs a signal of a level corresponding to the intensity of the light, the first light emitting means directly emits light to the light receiving means, and the second The light emitting means emits light to the target so that the light receiving means can receive the reflected light from the target, and the control means determines the timing at which the light receiving means has received light based on the signal output by the light receiving means. And the start and stop of the light emission of the first light emitting means and the second light emitting means are controlled. The control means acquires the first timing when the light receiving means receives light by causing the first light emitting means to emit light for a predetermined time, stops light emission of the first light emitting means, and A light emission signal for causing the second light emitting means to emit light is output after a predetermined time has elapsed since the output of the light emission signal to the first light emitting means for starting the light emission of the first light emitting means, and the second light emitting means is caused to emit light. The second timing at which the light receiving means receives the reflected light is obtained, and the second timing is acquired from the acquisition of the first timing based on the first timing, the second timing, and the predetermined time . since the difference obtained by subtracting the predetermined time from the time of up to acquisition timing to calculate the distance to the target, to provide a distance measuring apparatus which can highly accurately obtain the distance between the target That.

In the first invention, an amplification means for amplifying a signal output from the light receiving means in a state where a change edge of the signal is inclined, a level of the signal output from the amplification means, and a predetermined threshold value are obtained. A comparison means for outputting a signal when the level of the signal output from the amplification means exceeds the predetermined threshold, and the control means is configured to output the signal according to the signal output from the comparison means. The first timing and the second timing are acquired.

Here, by predetermining a threshold of Jo Tokoro as not subject level to noise, it is possible to provide a distance measuring apparatus which is not affected by noise.

According to a first aspect of the present invention, there is provided an amplifying means for amplifying the signal output from the light receiving means with the change edge of the signal inclined, and the first light emitting means emits the level of the amplified signal. Level holding means for holding before subtracting, subtracting means for subtracting the level held by the level holding means from the level of the amplified signal, and outputting a signal of the level obtained thereby, and the subtracting means And a comparison means for comparing the level of the signal output from the signal with a predetermined threshold and outputting a signal when the level of the signal output from the subtraction means exceeds the predetermined threshold. The means acquires the first timing and the second timing based on the signal output from the comparison means.

Here, by maintaining the level of amplified signals before said first light emitting means emits light, it is possible to hold the level of the ambient light signal is not affected by the external light signal ranging An apparatus can be provided.

According to a second aspect of the present invention, the light emitting means, the light guiding means for guiding the light emitted by the light emitting means, and the light emitting means after receiving the secondary light that is the light guided by the light guiding means. Light receiving means for receiving reflected light, which is light reflected by the target, and outputting a timing acquisition signal indicating the received timing as a signal of a level corresponding to the intensity of the received light; and Control means for acquiring timing at which the sub light and the reflected light are received by the light receiving means based on a signal output from the light receiving means, and controlling start and stop of light emission of the light emitting means; Amplifying means for amplifying the signal output by the means in a state where the change edge of the signal is inclined, and the level held by the level holding means from the level of the signal based on the signal output by the amplifying means. The subtracting means for subtracting the signal and outputting the signal of the level obtained thereby, the level of the signal output by the subtracting means and a predetermined threshold value are compared, and the level of the signal output by the subtracting means is the predetermined level Comparing means for outputting a signal when the threshold value is exceeded, a secondary light shielding means for shielding the incident of the secondary light to the light receiving means, and a reflected light for shielding the light including the reflected light to the light receiving means A light shielding means, and the control means causes the light emitting means to start the first light emission in a state where the light is shielded by the reflected light light shielding means, and the comparison means outputs a signal from the first light emission. When the output is detected, the light emission of the light emitting means is stopped, so that a delay time from the start of the first light emission until the comparison means stops outputting the signal by the first light emission. Measure and The second light emission is started by the light-emitting means while being blocked by the auxiliary light-shielding means, and the light-emitting means stops emitting light when it is detected that the comparison means has output a signal from the second light emission. By measuring the reflection time, the reflection time, which is the time from when the second light emission is started to when the comparison unit stops outputting the signal by the second light emission, is measured. Based on this, the distance to the target is calculated.

Here, determine the circuit delay in those the distance measuring apparatus, it is possible so to calculate the distance using the circuit delay, it calculates a more accurate distance.

According to a second aspect of the present invention, there is provided level holding means for holding the level of a signal obtained by amplification of the external light signal output by the light receiving means by receiving the external light, and the level of the amplified signal. Subtracting means for subtracting the level held by the level holding means and outputting a signal of the level obtained thereby, and the comparing means is a signal based on the signal output by the subtracting means. Are compared with a predetermined threshold value, and a signal is output when the level of the signal output from the subtracting means exceeds the predetermined threshold value.

Here, it is possible to hold the level of amplifier has an outer optical signal, it is possible to provide a distance measuring apparatus which is not affected by the external light signal.

Further, the control means in the second invention, from the operation of starting the first light emission to the light emitting means in a state where it is shielded by the reflected light shielding means executed when measuring the delay time, When the comparison means detects that the first light emission signal has been output, a series of operations up to the operation of stopping the light emission of the light emission means are repeatedly performed, thereby measuring a plurality of the delay times, The average value of the delay times is used as the delay time used when calculating the distance to the target.

Here, it obtains a plurality of delay time, since calculating the distance an average value of the plurality of delay time as a circuit delay, it is possible to calculate a more accurate distance.

Further, the control means in the second invention, from the operation of starting the second light emission to the light emitting means in a state where it is shielded by the sub-light shielding means executed when measuring the reflection time, When the comparison unit detects that the second light emission signal is output, a series of operations until the light emission unit stops light emission is repeatedly performed, thereby measuring a plurality of the reflection times. The average value of the reflection times is used as the reflection time used when calculating the distance to the target.

Here, by repeatedly operating the second light emission, the distance to the target can be accurately calculated, and the distance can be sequentially calculated for the moving target. Furthermore, this configuration makes it possible to continuously measure the distance in the shortest time in the distance measuring device.

Note that the change edge of the first and second inventions, if the signal supplied to the amplifying means of positive polarity refers to the rising edge, falling edge when the signal inputted to the amplifying means is negative Means an edge.

  According to the present invention, there is an effect that it is possible to provide a distance measuring device that can obtain a distance from a target with high accuracy.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, three embodiments will be described. In the three embodiments, a case where infrared light is applied as the light of the present invention will be described.
[First Embodiment]
FIG. 1 is a diagram illustrating a configuration of a distance measuring apparatus according to the first embodiment. As shown in the figure, the distance measuring device includes a control unit 10, a light emitting circuit 12, a main infrared light emitting element 14, a light emitting optical system 16, a light receiving optical system 18, a sub infrared light emitting element 20, an image pickup element 22, and an amplification. A circuit 24, a comparator 26, and a time measurement circuit 28 are included.

  The control unit 10 instructs the light emitting circuit 12 to start and stop light emission by each light emitting element, detects whether the comparator 26 outputs a signal, controls the time measuring circuit 28, and performs measurement. It has a role to control the entire distance device. The light emitting circuit 12 outputs a drive signal for driving the main infrared light emitting element 14 and the sub infrared light emitting element 20 in accordance with an instruction from the control unit 10. Specifically, the light emitting circuit 12 outputs a main infrared light emitting signal as a drive signal to the main infrared light emitting element 14 and outputs a sub infrared light emitting signal to the sub infrared light emitting element 20 to cause each light emitting element to emit light. . The main infrared light emitting element 14 emits infrared light with respect to the target according to the drive signal from the light emitting circuit 12. The light emitting optical system 16 has a role of transmitting the infrared light emitted from the main infrared light emitting element 14 and condensing it with respect to the target. The sub infrared light emitting element 20 causes infrared light to directly enter the light receiving surface of the image sensor 22 in accordance with a sub infrared light emission signal from the light emitting circuit 12, and the sub infrared light emitting element 20 emits light. Infrared light is expressed as sub-light in the following description.

  The light receiving optical system 18 forms an image on the light receiving surface of the image sensor 22 of reflected light, which is light reflected by the target from the infrared light emitted from the main infrared light emitting element 14. The imaging element 22 has sensitivity in the wavelength range of infrared light, receives reflected light, secondary light, external light other than reflected light and secondary light, and is a signal having a level corresponding to the intensity of the received light. In addition, a timing acquisition signal indicating the timing of light reception is output, and various photoelectric conversion elements such as a CMOS image sensor and a CCD area sensor can be used as the image sensor 22. The timing acquisition signal includes an image sensor arrival sub-infrared light emission signal output by receiving the sub-light, an image sensor arrival main infrared light emission signal output by receiving the main infrared light, and an external There is an external light signal output by receiving light.

  The amplifier circuit 24 amplifies the timing acquisition signal output from the image sensor 22 with the change edge of the timing acquisition signal inclined, and outputs the amplified signal as an amplification circuit output signal. In the following description, all the cases of positive polarity are described, so that the change edge is a rising edge.

  The comparator 26 compares the level of the amplifier circuit output signal with a predetermined measurement level a, and when the level of the amplifier circuit output signal exceeds the measurement level, a signal of a predetermined high (H) level. (Hereinafter referred to as H signal) is output as a comparator output signal. The measurement level a is for removing noise from the amplification circuit output signal. Therefore, the level is determined in advance as a level not affected by the noise. The time measuring circuit 28 measures time for measuring the distance.

  Next, processing executed when the distance to the target is measured with the distance measuring apparatus configured as described above will be described with reference to the time chart of FIG. The time chart shown in the figure shows the levels of the sub-infrared light emission signal, main infrared light emission signal, image sensor arrival main infrared light emission signal, amplifier circuit output signal, and comparator output signal.

  First, the control unit 10 controls the light emitting circuit 12 so that the sub-infrared light emission signal is at a high level for a predetermined period. Accordingly, the main infrared light emitting element 14 emits light for a period corresponding to the predetermined period. Further, the control unit 10 controls the light emission circuit 12 so that the main infrared light emission signal is set to a high level for a predetermined period after the time t1 has elapsed since the sub infrared light emission signal was output.

  When sub-light is emitted by the sub-infrared light emission signal, the sub-light is directly received by the image sensor 22, and the image sensor-arrival sub-infrared light emission signal is output from the image sensor 22. Then, the signal is amplified by the amplifier circuit 24, and the output signal of the amplifier circuit with the rising edge inclined as shown in the figure is output. When the amplifier circuit output signal exceeds the measurement level a, the comparator 26 outputs an H signal as the comparator output signal. This signal is output until the output signal of the amplifier circuit becomes the measurement level a or lower.

  Similarly, when main infrared light is emitted, reflected light is received by the image sensor 22 and an image sensor arrival main infrared light emission signal is output from the image sensor 22. Then, the signal is amplified by the amplifier circuit 24, and an amplifier circuit output signal in which the rising edge is inclined as shown in the figure is output. When the amplification circuit output signal exceeds the measurement level a, the comparator 26 outputs the H signal as the comparator output signal as before. This signal is output until the output signal of the amplifier circuit becomes the measurement level a or lower.

  In the time chart described above, the time from when the sub-light is emitted until the image sensor 22 outputs the main infrared light emission signal reaching the image sensor is t2, and the main infrared light is emitted and then the image sensor is emitted. Let t3 be the time until 22 outputs the image sensor arrival main infrared light emission signal.

  This time t3 is the time from when infrared light is emitted, reflected by the target, and returned, so when the time t3 is obtained, the distance from the target is obtained. As shown in the figure, there is a relationship of t1 + t3 = t2, and the time t1 is known because it is a predetermined time, and the time t2 is also known because it is obtained by actual measurement. Therefore, when the speed of the infrared light is c, the distance L from the target can be obtained by calculating c × (t3) / 2. This distance L is calculated by the control unit 10, but t 1 for obtaining the distance L is held in advance by the control unit 10, and the time t 2 and the time t 3 are obtained from the time measurement circuit 28 and the comparator 26. It can be obtained based on the output signal.

As shown in the time chart described above, in this embodiment, the infrared light is emitted twice by the same main infrared light emitting element 14 and the light emitting circuit 12 for measuring the time, and the infrared light is emitted. Regarding light reception, the same image pickup device 22, amplification circuit 24, comparator 26, and time measurement circuit 28 perform signal processing, so that there is no variation in the electrical characteristics of these components, and the influence of temperature variation, temporal variation, etc. Therefore, it is possible to provide a distance measuring device that can obtain a distance from the target with high accuracy.
[Second Embodiment]
Next, a second embodiment will be described. In the following description, description of the already described reference numerals is omitted. Further, the same signal as the signal used in the first embodiment is the same signal as the signal in the first embodiment.

  FIG. 3 is a diagram illustrating a configuration of the distance measuring apparatus according to the second embodiment. As shown in the figure, in addition to the configuration of the first embodiment, the distance measuring device includes a hold circuit 30 and a subtraction amplifier (op-amp) between the amplifier circuit 24 and the comparator 26. The device 32 is connected in series.

  The hold circuit 30 holds the level of the external light signal obtained by amplifying the signal output when the image sensor 22 receives the infrared light in the external light, and the control unit 10 notifies the hold timing. The Since this timing is notified from the control unit 10 immediately before the sub-light is emitted, it is possible to sample the level of the external light signal (hereinafter referred to as the external light level). The held level signal is output as a hold circuit output signal.

  The hold circuit 30 is connected to the inverting input terminal of the subtractor 32. When the state is not the hold state, the hold circuit 30 outputs the amplification circuit output signal output from the amplification circuit 24 as it is to the subtracter 32 as the hold circuit output signal. A low-pass filter may be used in place of the hold circuit 30.

  The subtracter 32 has the output terminal of the amplifier circuit 24 connected to the non-inverting input terminal, and subtracts the level of the hold circuit output signal output from the hold circuit 30 from the level of the amplifier circuit output signal output from the amplifier circuit 24. The subtracted result level signal is output as a subtracter output signal. The comparator 26 compares the signal level with the measurement level a.

  Next, processing executed when the distance to the target is measured with the distance measuring apparatus configured as described above will be described with reference to the time chart of FIG. The time chart shown in the figure includes a sub-infrared light emission signal, a main infrared light emission signal, an image sensor arrival main infrared light emission signal, an amplifier circuit output signal, a hold timing signal, a hold circuit output signal, a subtractor output signal, and The level of the comparator output signal is shown. The hold timing signal is a signal output from the control unit 10 to the hold circuit 30.

  First, the control unit 10 outputs a hold timing signal to the hold circuit 30. Thereby, the hold circuit 30 outputs an external light level signal. Next, the control unit 10 controls the light emitting circuit 12 so that the sub-infrared light emission signal is at a high level for a predetermined period. Accordingly, the main infrared light emitting element 14 emits light for a period corresponding to the predetermined period. Further, the control unit 10 controls the light emission circuit 12 so that the main infrared light emission signal is set to a high level for a predetermined period after the time t1 has elapsed since the sub infrared light emission signal was output.

  When the sub-light is emitted, the sub-light is directly received by the image sensor 22, and an image sensor-arrival sub-infrared light emission signal is output from the image sensor 22. The signal is amplified by the amplifier circuit 24. As shown in the figure, the output signal of the amplifier circuit with the rising edge inclined is output. In the case of the second embodiment, the amplification circuit output signal is a signal having a level obtained by adding the level of the signal obtained by receiving the auxiliary light to the external light level.

  The amplifier circuit output signal and the hold circuit output signal are input to the subtractor 32. The subtractor 32 subtracts the level of the hold circuit output signal from the level of the amplifier circuit output signal, and obtains a signal having a level obtained thereby. Output as subtractor output signal.

  When the level of the subtractor output signal exceeds the measurement level a, the comparator 26 outputs an H signal as a comparator output signal. This signal is output until the subtractor output signal becomes the measurement level a or less.

  When the main infrared light is emitted, the reflected light is received by the image sensor 22, and an image sensor arrival main infrared light emission signal is output from the image sensor 22. Then, the signal is amplified by the amplifier circuit 24, and an amplifier circuit output signal in which the rising edge is inclined as shown in the figure is output.

The amplifier circuit output signal and the hold circuit output signal are input to the subtractor 32. The subtractor 32 subtracts the level of the hold circuit output signal from the level of the amplifier circuit output signal, and obtains a signal having a level obtained thereby. Output as subtractor output signal When the subtractor output signal exceeds the measurement level a, the comparator 26 outputs an H signal as a comparator output signal. This signal is output until the subtractor output signal becomes the measurement level a or less.

  In the time chart described above, the time from when the sub-light is emitted until the image sensor 22 outputs the main infrared light emission signal reaching the image sensor is t2, and the main infrared light is emitted and then the image sensor is emitted. Let t3 be the time until 22 outputs the image sensor arrival main infrared light emission signal.

  This time t3 is the time from when infrared light is emitted, reflected by the target, and returned, so when the time t3 is obtained, the distance from the target is obtained. As shown in the figure, there is a relationship of t1 + t3 = t2, and the time t1 is known because it is a predetermined time, and the time t2 is also obtained by actual measurement. Therefore, when the speed of the infrared light is c, the distance L from the target can be obtained by calculating c × (t3) / 2. The distance L is calculated by the control unit 10, but t1 for obtaining the distance L is held in advance by the control unit 10, and t2 and t3 are signals from the time measuring circuit 28 and the comparator 26. Can be obtained.

As shown in the time chart described above, in this embodiment, the infrared light is emitted twice by the same main infrared light emitting element 14 and the light emitting circuit 12 for measuring the time, and the infrared light is emitted. Regarding light reception, since signal processing is performed by the same image pickup device 22, amplifier circuit 24, comparator 26, time measurement circuit 28, hold circuit 30, and subtractor 32, there is no variation in the characteristics of these components, and temperature fluctuation, In addition, it is possible to provide a distance measuring device that can obtain a highly accurate distance from the target because it is not affected by fluctuations with time or the like.
[Third Embodiment]
Next, a third embodiment will be described. In the following description, description of the already described reference numerals is omitted. Further, the same signal as the signal used in the first and second embodiments is the same signal as the signal in the first and second embodiments.

  FIG. 5 is a diagram illustrating a configuration of a distance measuring apparatus according to the third embodiment. As shown in the figure, the distance measuring device does not use the sub infrared light emitting element 20 in the second embodiment, but uses the light emitted from the infrared light emitting element 40 and passing through the light guide tube 34 as the sub light. It is a configuration to use. Furthermore, in the third embodiment, a configuration including a sub-light-shielding plate 36 that shields sub-light to the image sensor 22, a main light-shield plate 38 that shields light including reflected light to the image sensor 22, and a period measurement circuit 42. It has become. The period measuring circuit 42 is connected in series between the comparator 26 and the control unit 10.

  As the light guide tube 34, for example, a mirror, a half mirror, a prism, or an optical fiber can be used. The main light shielding plate 38 and the sub light shielding plate 36 may use mechanical shutters. The period measurement circuit 42 is a circuit for obtaining Ts, which will be described later. In this circuit, the period may be obtained by counting pulses, or the period is calculated from the frequency in synchronization with the transmitter in the PLL circuit. It may be calculated.

  Next, processing executed by the distance measuring apparatus configured as described above will be described with reference to time charts of FIGS. There are two processes executed in the above configuration, one is a process for obtaining the delay time shown in FIG. 6, and the other is a process for obtaining the distance from the target shown in FIG.

  First, processing for obtaining the delay time will be described using the time chart of FIG. The time chart shown in the figure shows the levels of the infrared light emission signal, the image sensor output signal, the subtractor output signal, and the comparator output signal. Among these, the infrared light emission signal is a signal for the light emitting circuit 12 to drive the infrared light emitting element 40. The image sensor output signal is a signal output when the image sensor 22 receives the secondary light or the reflected light.

  In FIG. 6, light emission by the infrared light emission signal is secondary light that passes through the light guide tube 34, and the processing shown in FIG. 6 is performed in a state where light including reflected light is blocked, that is, the main light blocking plate 38 This process is executed in the closed state.

  First, the control unit 10 controls the light emitting circuit 12 so that the infrared light emission signal is at a high level for a predetermined time.

  Due to this light emission, the image sensor 22 receives secondary light, and an image sensor output signal is output from the image sensor 22. Then, the signal is amplified by the amplifier circuit 24, and a signal in which the rising edge is inclined is output. The amplified signal is output to the hold circuit 30 and the subtracter 32. The subtracter 32 subtracts the signal of the level obtained by subtracting the level of the signal output from the hold circuit 30 as shown in FIG. Output as an output signal.

  When the level of the subtractor output signal exceeds the measurement level a, the comparator 26 outputs a comparator output signal. This signal is output until the signal output from the subtractor 32 becomes equal to or lower than the measurement level a. When the comparator output signal is output, the control unit 10 detects the comparator output signal and causes the light emitting circuit 12 to stop light emission. At this time, a delay occurs until the infrared light emitting element 40 actually stops light emission after the control unit 10 is instructed to stop light emission. The control unit 10 instructed to stop the light emission instructs the light emitting circuit 12 to emit light again when the comparator 26 no longer outputs the H signal. In this case, a delay occurs until the infrared light emitting element 40 actually emits light.

  Thereafter, the above process is repeated. In this time chart, the time from when the sub-light is emitted until the image sensor 22 outputs the image sensor output signal is defined as t1, and the subtracter output signal is output from the subtractor 32 and the comparator output signal is output. T2 is the time until the output of the comparator is output, and the time from when the control unit 10 notifies the stop of the secondary light emission due to the output of the comparator output until the infrared light emission is actually stopped is t3. And

In this case, the time during which the auxiliary light is emitted is t1 + t2 + t3. In addition, since the control unit 10 delays the time t3 from when the light emission stop is instructed until the light emission actually stops, similarly, the infrared light emitting element 40 actually emits light after the control unit 10 instructs the light emission. Until the time t3. In addition, since the cycle Ts of the output start timing of the infrared light emission signal is equal to the cycle of the output start timing of the comparator output signal, the cycle Ts is as follows, as shown in FIG.
Ts = 2 (t1 + t2 + t3)
This period Ts is a circuit delay time of the distance measuring device, and Ts becomes a delay period of the distance measuring device by repeatedly executing as shown in FIG. A large number of Ts may be sampled, and the average value thereof may be changed to Ts.

  The process of measuring the distance using Ts will be described with reference to the time chart of FIG. The time chart shown in the figure shows levels of a hold timing signal, a hold circuit output signal, an infrared light emission signal, an image sensor output signal, a subtractor output signal, and a comparator output signal.

  The light emitted by the infrared light emission signal is light for receiving light from the light receiving optical system 18, and the process shown in FIG. This process is executed in the closed state.

  First, the control unit 10 outputs a hold timing signal to the hold circuit 30. Thereby, the hold circuit 30 outputs an external light level signal. Next, the control unit 10 controls the light emitting circuit 12 so that the infrared light emission signal is at a high level for a predetermined period. In response to this, the infrared light emitting element 40 emits light for a period corresponding to the predetermined period.

  The reflected light reflected by the target as the infrared light emitting element 40 emits light is received by the image sensor 22 and an image sensor output signal is output from the image sensor 22. At this time, since a time Δt from when the light is emitted until the reflected light arrives is added, the timing at which the output of the image sensor output signal is started is further delayed by Δt from the delay time t1.

  The image sensor output signal is amplified by the amplifier circuit 24 to become an amplifier circuit output signal in which the rising edge is inclined. The amplifier circuit output signal and the hold circuit output signal are input to the subtractor 32, and the subtracter 32 performs amplification. The level of the hold circuit output signal is subtracted from the level of the circuit output signal, and the resulting subtracter output signal is output as shown in FIG. The delay time until the level of the subtractor output signal exceeds the measurement level a is the time t2.

  When the level of the subtractor output signal exceeds the measurement level a, the comparator 26 outputs an H signal. This signal is output until the level of the subtracter output signal becomes the measurement level a or less. At this time, when the comparator output signal is output, the control unit 10 instructs to stop the emission of the secondary light. The delay time from the issue stop instruction to the actual stop of light emission is time t3.

Therefore, the time Tk from when the infrared light emitting element 40 emits light to when it emits next time is as follows.
Tk = Ts + 2Δt
Since the time Tk is obtained by actual measurement, and the time Ts is obtained by the processing described with reference to FIG. 6, the time Δt is determined. Therefore, when the speed of the infrared light is c, the distance L from the target can be obtained by calculating c × Δt / 2. Note that the distance L is calculated by the control unit 10, but Ts is held by the control unit 10 when the processing for obtaining the delay time described in FIG. 6 is executed, and Tk is the period between the time measurement circuit 28 and the period. It can be obtained based on the signal from the measurement circuit 42.

  As shown in the time chart described above, in this embodiment, the infrared light is emitted twice by the same main infrared light emitting element 14 and the light emitting circuit 12 for measuring the time, and the infrared light is emitted. Regarding light reception, since signal processing is performed by the same image pickup device 22, amplifier circuit 24, comparator 26, time measurement circuit 28, hold circuit 30, and subtractor 32, there is no variation in the characteristics of these components, and temperature fluctuation, In addition, since the circuit delay time is taken into consideration without being affected by fluctuations with time, etc., a distance measuring device capable of obtaining a highly accurate distance from the target can be provided.

  According to the three embodiments described above, the light receiving means (imaging element 22) that receives light and outputs a signal having a level corresponding to the intensity of the light, and the first light that directly emits light to the light receiving means. A light emitting means (main infrared light emitting element 14), a second light emitting means (sub-infrared light emitting element 20) for emitting light to the target so that the light receiving means can receive reflected light from the target; Control means (control unit) that acquires the timing at which the light receiving means receives light based on the signal output by the light receiving means and controls the start and stop of light emission of the first light emitting means and the second light emitting means. 10), and the control means obtains the first timing received by the light receiving means by causing the first light emitting means to emit light for a predetermined time, and stops the light emission of the first light emitting means. And then emitting the second light emitting means. To obtain a second timing at which the light receiving means has received the reflected light by which to calculate the distance to the target based on the first timing, the second timing and the predetermined time.

  In addition, amplifying means (amplifying circuit 24) for amplifying the signal output from the light receiving means (imaging element 22) with the change edge of the signal inclined, a level of the signal output from the amplifying means, and a predetermined level And comparing means (comparator 26) for outputting a signal when the level of the signal output from the amplifying means exceeds the predetermined threshold, and the control means The first timing and the second timing are obtained from the signal output from the comparison means.

  An amplification means (amplifying circuit 24) for amplifying a signal output from the light receiving means (imaging element 22) in a state where a change edge of the signal is inclined; and a level of the amplified signal is set to the first level. A level holding means (hold circuit 30) that holds before the light emitting means emits light, and a level held by the level holding means is subtracted from a level of the amplified signal, and a signal of a level obtained thereby is obtained. The subtracting means (subtractor 32) for output and the level of the signal output from the subtracting means are compared with a predetermined threshold, and the signal is output when the level of the signal output from the subtracting means exceeds the predetermined threshold. And a comparison unit (comparator 26) for outputting the first timing and the second timing based on a signal output from the comparison unit.

  Further, the light emitting means (infrared light emitting element 40), the light guiding means (light guide tube 34) for guiding the light emitted by the light emitting means, and the auxiliary light which is the light guided by the light guiding means. After receiving the light, the reflected light, which is the light reflected by the target from the light emitted from the light emitting means, is received, and the timing acquisition signal indicating the received timing is used as a signal of a level corresponding to the intensity of the received light. The light receiving means (imaging element 22) to output, the timing at which the sub light and the reflected light are received by the light receiving means are acquired based on the signal output by the light receiving means, and the light emission of the light emitting means is started. And a control means (control unit 10) for controlling the stop, an amplifying means (amplifying circuit 24) for amplifying a signal output from the light receiving means in a state where a change edge of the signal is inclined, and an output from the amplifying means. Signal A comparison means (comparator 26) for comparing the level of the signal based on the predetermined threshold value and outputting a signal when the level of the signal output from the subtraction means exceeds the predetermined threshold value; Sub-light shielding means (sub-light shielding plate 36) for shielding the incident of the secondary light, and reflected light shielding means (main light shielding plate 38) for shielding the light including the reflected light to the light receiving means. When the control means detects that the light emitting means starts the first light emission while being blocked by the reflected light shielding means, and the comparison means outputs a signal by the first light emission, By stopping the light emission of the light emitting means, a delay time, which is a time from when the first light emission is started to when the comparison means stops outputting the signal by the first light emission, is measured, and the sub-light Shaded by light shielding means Then, the second light emission is started by causing the light emission means to start the second light emission, and when the comparison means detects that the signal from the second light emission is output, the light emission means stops the light emission. The reflection time, which is the time from the start until the comparison unit stops outputting the signal by the second light emission, is measured, and the distance to the target is calculated based on the delay time and the reflection time. .

  Also, the level holding means (hold circuit 30) that holds the level of the signal amplified by the amplifying means for the external light signal output when the light receiving means (imaging device 22) receives the external light is amplified. Subtracting means (subtractor 32) for subtracting the level held by the level holding means from the level of the received signal and outputting a signal of the level obtained thereby, the comparing means comprising: The level of the signal based on the signal output from the subtracting means is compared with a predetermined threshold, and a signal is output when the level of the signal output from the subtracting means exceeds the predetermined threshold.

  Further, the control means (control unit 10) is configured to block the light emitting means (infrared light emitting element) while being shielded by the reflected light shielding means (main light shielding plate 38) that is executed when the delay time is measured. 40) a series of operations from an operation of starting the first light emission to an operation of stopping the light emission of the light emitting means when it is detected that the comparison means (comparator 26) outputs a signal by the first light emission. Are repeatedly executed, and a plurality of the delay times are measured, and an average value of the plurality of the delay times is set as a delay time used when calculating the distance to the target.

Further, the control means (control unit 10) is configured to block the light emitting means (infrared light emitting element) while being shielded by the secondary light shielding means (secondary light shielding plate 36) executed when the reflection time is measured. 40) a series of operations from the operation of starting the second light emission to the operation of causing the light emitting device to stop the light emission when detecting that the comparison means (comparator 26) outputs a signal by the second light emission. By repeatedly executing the above, the plurality of reflection times are measured, and the average value of the plurality of reflection times is set as the reflection time used when calculating the distance to the target. The image sensor may be a line sensor in which a plurality of image sensors are arranged in a line, or a two-dimensional array area sensor.

It is a block diagram which shows the structure of the ranging device which concerns on 1st Embodiment. It is a time chart which shows the flow of the ranging process in 1st Embodiment. It is a block diagram which shows the structure of the ranging device which concerns on 2nd Embodiment. It is a time chart which shows the flow of the ranging process in 2nd Embodiment. It is a block diagram which shows the structure of the ranging apparatus which concerns on 3rd Embodiment. It is a time chart which shows the flow of the process which calculates | requires delay time. It is a time chart which shows the flow of the ranging process in 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control part 12 Light emission circuit 14 Main infrared light emitting element 16 Light emitting optical system 18 Light receiving optical system 20 Sub infrared light emitting element 22 Imaging element 24 Amplifying circuit 26 Comparator 28 Time measurement circuit 30 Hold circuit 32 Subtractor 34 Light guide tube 36 Sub light shielding plate 38 Main light shielding plate 40 Infrared light emitting element 42 Period measurement circuit

Claims (3)

A light receiving means for receiving light and outputting a signal of a level corresponding to the intensity of the light;
First light emitting means for emitting light directly to the light receiving means;
A second light emitting means for emitting light to the target so that the light receiving means can receive reflected light from the target;
Control means for obtaining the timing at which the light receiving means has received light based on a signal output by the light receiving means, and controlling the start and stop of light emission of the first light emitting means and the second light emitting means;
Have
The control means includes
The first timing when the light receiving means receives light is obtained by causing the first light emitting means to emit light, the light emission of the first light emitting means is stopped, and the light emission of the first light emitting means is started. The light receiving means receives the reflected light generated by outputting the light emitting signal for causing the second light emitting means to emit light after a predetermined time has elapsed from the output of the light emitting signal to the first light emitting means. Is obtained from the time from the acquisition of the first timing to the acquisition of the second timing based on the first timing, the second timing and the predetermined time. A distance measuring device that calculates a distance from the target based on a difference obtained by subtracting a predetermined time . Amplifying means for amplifying the signal output from the light receiving means with the change edge of the signal inclined;
Comparing means for comparing the level of the signal output from the amplifying means with a predetermined threshold and outputting a signal when the level of the signal output from the amplifying means exceeds the predetermined threshold;
Further comprising
The control means is configured to output the first timing and the second timing according to a signal output from the comparison means.
The distance measuring device according to claim 1, wherein the timing is acquired. Amplifying means for amplifying the signal output from the light receiving means with the change edge of the signal inclined;
Level holding means for holding the level of the amplified signal before the first light emitting means emits light;
Subtracting means for subtracting the level held by the level holding means from the level of the amplified signal and outputting a signal of the level obtained thereby;
Comparing means for comparing the level of the signal output by the subtracting means with a predetermined threshold, and outputting a signal when the level of the signal output by the subtracting means exceeds the predetermined threshold;
Further comprising
The control means is configured to output the first timing and the second timing according to a signal output from the comparison means.
The distance measuring device according to claim 1, wherein the timing is acquired.

Images