WO2017064787A1

WO2017064787A1 - Optical ranging device, optical ranging method, and image projection apparatus provided therewith

Info

Publication number: WO2017064787A1
Application number: PCT/JP2015/079140
Authority: WO
Inventors: 政信紫垣; 将史山本; 浦田　浩之
Original assignee: 日立マクセル株式会社
Priority date: 2015-10-15
Filing date: 2015-10-15
Publication date: 2017-04-20

Abstract

The purpose of the present invention is to correct a circuit delay time and time resolution variation, which cause a decrease in the measurement accuracy of an optical ranging device, at high speed in a short time. For this purpose, an optical ranging method of an optical ranging device for calculating a distance by a time difference between an emitted light signal and a received light signal is configured to: provide, in the optical ranging device, at least two reference objects the distances and angles of which from a light reception unit for receiving the received light signal are different; measure time differences of the plurality of reference objects by a time measurement unit for measuring a time difference; calculate the circuit delay time of the light reception unit and the measurement resolution of the time measurement unit by performing a predetermined calculation on the plurality of time differences; and calculate a distance to an object to be measured on the basis of the calculation results of the circuit delay time and the measurement resolution.

Description

Optical distance measuring device, optical distance measuring method, and image projection device including the same

The present invention relates to an optical distance measuring device, an optical distance measuring method, and an image projection device including the same, which measure the distance from a measurement object by measuring the round-trip time of light.

As background art in this technical field, there is JP-A-6-289135 (Patent Document 1). In Patent Document 1, when measuring the distance to the measurement object by measuring the round-trip time of the light emitted from the measurement object and receiving the reflected light, a calibration pulse different from the reflected pulse light is used. Methods have been proposed that use it to improve time measurement accuracy.

JP-A-6-289135

In order to accurately measure the distance to the measurement object, it is necessary to measure the round trip time of the light emitted to the object with high accuracy. There are two factors that reduce the measurement accuracy of the optical round-trip time: the circuit delay time of the light receiving circuit, and the change in time resolution (time resolution variation) in the time measurement circuit. In the above-mentioned Patent Document 1, correction of circuit delay time and time resolution variation is performed using a calibration pulse different from the reflected pulse light. However, with this method, the response speed is slow because the reflected pulse light is converted to a low frequency and then the response speed is slow. Furthermore, if the circuit delay time and time resolution variation change in a time shorter than one measurement cycle, There is a problem that changes cannot be followed. Therefore, when the circuit delay time and time resolution change in a short time, it is necessary to perform calibration following the change.

In order to solve the above-described problems, the present invention is an optical distance measuring method of an optical distance measuring device that calculates a distance based on a time difference between an emitted light signal and a received light signal, and an optical distance measuring device includes: At least two reference objects with different distances and angles from the light receiving unit that receives the light reception signal are provided, and the time measurement unit for measuring the time difference measures the time difference with respect to the plurality of reference objects, and the predetermined time difference is determined. The circuit delay time of the light receiving unit and the measurement resolution of the time measuring unit are calculated, and the distance to the measurement object is calculated based on the calculation result of the circuit delay time and the measurement resolution.

According to the present invention, even when the circuit delay time of the light receiving circuit and the time resolution of the time measuring circuit change in a short time, the optical distance measuring device, the optical measuring device capable of measuring the distance to the measurement object with high accuracy. A distance method and an image projection apparatus including the distance method can be provided.

It is a conceptual diagram which shows the distance measurement principle of the optical ranging apparatus used as the premise of Example 1. FIG. FIG. 3 is a timing chart for explaining the distance measurement principle of the optical distance measuring device which is a premise of the first embodiment. 1 is a block diagram illustrating a configuration example of an optical distance measuring device that is a premise of Embodiment 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external view of a video projection device including an optical distance measuring device that is a premise of a first embodiment. 1 is a block diagram illustrating a configuration example of an image projection device including an optical distance measuring device that is a premise of Embodiment 1. FIG. It is a figure explaining the application example using the optical ranging device on the image | video projection apparatus used as the premise of Example 1. FIG. It is a figure which shows the relative relationship of the angle control signal in the optical ranging device used as the premise of Example 1, a start pulse, a light reception signal, and a gate pulse. It is a block diagram which shows the example of an internal structure of the threshold value determination part in the optical ranging apparatus used as the premise of Example 1. FIG. It is a figure which shows the relative relationship of the start pulse in the optical ranging device used as the premise of Example 1, a light reception signal, and a stop pulse. FIG. 3 is a block diagram illustrating functional blocks of a time measuring unit in the optical distance measuring device that is a premise of the first embodiment. It is a block diagram which shows the structural example of the optical ranging apparatus in Example 1. FIG. It is a figure explaining the application example which uses the optical ranging device on the image | video projection apparatus in Example 1. FIG. 3 is a flowchart illustrating an operation example of the optical distance measuring device according to the first embodiment. It is the installation example which installed the optical ranging device in the entrance / exit upper part as an application example of the optical ranging device in Example 2. FIG. It is the installation example which installed the optical ranging device in the vehicle gate upper part as an application example of the optical ranging device in Example 2. FIG. It is the installation example which installed the optical ranging apparatus in the belt conveyor vicinity as an application example of the optical ranging apparatus in Example 2. FIG. As an application example of the optical distance measuring apparatus according to the second embodiment, the optical distance measuring apparatus is installed in multiple stages to perform three-dimensional measurement.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the principle of distance measurement of the optical distance measuring device, which is a premise of the present embodiment, will be described with reference to FIGS. 1A and 1B. The distance measuring principle of the present optical distance measuring device is a so-called Time-Of-Flight (hereinafter referred to as TOF) method in which the distance is calculated based on the time difference between the outgoing light signal and the received light signal. In FIG. 1A, the light source unit 1 emits light for distance measurement to the measurement object 3. The light receiving unit 2 receives reflected light of the light emitted to the measurement object 3. The measurement object 3 exists at a position away from the light source unit 1 and the light receiving unit 2 by L [m]. Here, assuming that the speed of light is c = 3.0 × 10 ⁸ [m / s], and the time difference from when the light source unit 1 starts emitting light to when the light receiving unit 2 receives reflected light is t [s]. The relationship of the formula (1) is established between the distance L [m] and the time difference t [s].
L [m] = c [m / s] × t [s] / 2 (1)
Therefore, hereinafter, the optical distance measuring device described in the present embodiment uses the time difference t [s] corresponding to the round-trip time of light as the timing of the light emitted from the light source unit 1 and the reflected light at the light receiving unit 2 as shown in FIG. 1B. It measures from the time difference with the timing which received light, and calculates the distance with a target object from Formula (1).

FIG. 2 is a block diagram showing the configuration of the optical distance measuring device which is the premise of the present embodiment. The optical distance measuring device 10 is connected to an external device 12 via a communication unit 11. The optical distance measuring device 10 converts distance information and angle information of the measurement object into position information, and transmits the position information to the external device 12 via the communication unit.

The optical distance measuring device 10 includes a light source unit 1, a light receiving unit 2, a time measuring unit 4, an emission angle control unit 5, a control unit 6, an emitted light modulation unit 7, a received light pulse generation unit 8, a time averaging processing unit 9, and communication. Unit 11 and threshold value determination unit 21, and the emission angle of the emitted light 31 can be controlled by the emission angle control unit 5.

The control unit 6 outputs a start pulse 41 that is a pulsed electric signal to the time measuring unit 4 and the outgoing light modulation unit 7. The emitted light modulation unit 7 modulates the emitted light 31 of the light source unit 1 in synchronization with the start pulse 41. The light source unit 1 is electrically connected to the outgoing light modulation unit 7 and emits light that is pulse-modulated according to the output signal of the outgoing light modulation unit 7 synchronized with the start pulse 41. The emission angle control unit 5 is composed of a rotating mirror or the like, and emits emission light 31 to the measurement object 3 at a predetermined angle based on a control signal from the control unit 6.

The light receiving unit 2 receives the reflected light 32 from the measurement object 3 and outputs the received light waveform. The light reception pulse generation unit 8 compares the light reception signal output from the light reception unit 2 with a reference voltage, and outputs the pulse as a stop pulse 42.

The time measuring unit 4 receives a start pulse 41 and a stop pulse 42. The time measuring unit 4 measures the rise time difference between the start pulse 41 and the stop pulse 42 and transmits the time difference measurement result to the time averaging processing unit 9. The time averaging processing unit 9 buffers a time difference measurement result for a predetermined number of times and transmits the averaged result to the control unit 6.

The control unit 6 calculates the position information of the measurement object from the angle control signal 51 output to the emission angle control unit 5 and the time difference measurement result received from the time averaging processing unit 9. The control unit 6 transmits the position information of the measurement object 3 to the external device 12 via the communication unit 11. The communication unit 11 may be wirelessly connected to a smartphone, a tablet, or the like in addition to a wired connection with the external device 12 via USB or the like. For wireless communication, not only WiFi (registered trademark) but also a wireless system such as Bluetooth (registered trademark) may be used. At that time, the communication unit 11 includes an IC having the function. The operation may be performed by connecting to an external recording medium such as a USB memory or an SD card with a built-in wireless function.

Next, a case where the external device 12 is, for example, a video projection device will be described with reference to FIG. FIG. 3 is an external view of the image projection apparatus 12A which is a premise of the present embodiment. In FIG. 3, the image projection device 12 </ b> A will be described as including the optical distance measuring device 10. The horizontal direction of the video screen is the x direction, the vertical direction of the video screen is the y direction, and the vertical direction of the video screen is the z direction. The image projection device 12A is installed on an installation surface (desk) 33. The image light generated inside the image projection device 12A is magnified by the projection lens 34, then reflected by the reflection mirror 35, and reflected on the installation surface 33 by the image screen 36. Is projected. The focus of the projected image is adjusted by the focus ring 37. The reflection mirror 35 is configured to be foldable, and is stored so that the reflection surface faces the image projection device 12A when the image projection device 12A is not used.

FIG. 4 is a block diagram showing the configuration of the image projection unit 43 of the image projection device 12A and the built-in optical distance measuring device 10 which are the premise of this embodiment. Here, in order to describe communication between the optical distance measuring device 10 and the image projection unit 43 in the image projection device 12A, the optical distance measuring device 10 is not described except for the communication unit 11.
The video projection unit 43 includes a video control unit 44, a video projection light source 45, a light control unit 46, a projection lens 47, and a reflection mirror 48.

The video control unit 44 outputs a control signal to the video projection light source 45 and the light control unit 46 in accordance with the video signal supplied from the external device 49. The image projection light source 45 is a halogen lamp, LED (Light Emitting Diode), laser, or the like, and adjusts the amount of light according to a control signal input from the image control unit 44. When the image projection light source 45 includes three colors of R (Red), G (Green), and B (Blue), the light amount may be controlled independently according to the image signal. The light control unit 46 has optical system components such as a mirror, a lens, a prism, and an imager (for example, a display device such as a liquid crystal panel), and is supplied from an external device 49 using the light emitted from the image projection light source 45. An optical image based on the processed image signal is generated.

The projection lens 47 enlarges the output image of the light control unit 46. The reflection mirror 48 reflects the light emitted from the projection lens 47 and projects the video screen 36 on the installation surface 33. The reflection mirror 48 uses an aspherical mirror, and when projecting an image screen of the same size, the projection distance can be shortened compared to a general image projection apparatus. In the present embodiment, the video projection unit 43 using the reflection mirror 48 has been described as an example, but other configurations may be used as long as video projection can be realized.

The external device 49 is a general information processing device such as a PC (Personal Computer) connected to the video projection device 12A and a mobile terminal device such as a smartphone, and supplies a video signal to the video projection device 12A. . The external device 49 is not limited to a PC and a portable terminal device, and may be a device that supplies a video signal to the video projection device 12A, such as a card-like storage medium inserted into a card interface provided in the video projection device 12A. That's fine.

Next, communication between the optical distance measuring device 10 and the image projection unit 43 will be described. The optical distance measuring device 10 transmits the detected position information of the measurement object 3 from the communication unit 11 to the video control unit 44. The video control unit 44 operates the external device and the video projection unit 43 in response to the input position information. For example, page switching, enlargement / reduction, movement, character input, etc. are performed in the operation of the external device, and power ON / OFF switching, light amount adjustment, color adjustment, enlargement / reduction, movement, etc. are performed in the operation of the image projection unit 43. . The output of the position information may be performed by communication such as UART (Universal Asynchronous Receiver Receiver Transmitter), SPI (Serial Peripheral Interface), I2C (Inter-Integrated Circuit). Here, an example in which the image projection device 12A incorporates the optical distance measuring device 10 has been shown, but in the case of a separate body, communication may be performed using a wired USB or the like, or may be performed wirelessly. In the case of wireless, WiFi may be used as described above, or Bluetooth may be used. If the data output by the communication unit 11 is output by HID (Human Interface Device), the image projection device 12A virtually recognizes the optical distance measuring device 10 as a keyboard or a mouse. There is an advantage that it is not necessary to provide processing software.

Next, an application example using an optical distance measuring device on an image projection device will be described. FIG. 5 is a diagram illustrating an example in which a person performs an operation with a finger on the video screen 36. FIG. 5 shows an example in which the outgoing light of the light source unit 1 is scanned on the screen using the outgoing angle control unit 5 shown in FIG. The optical distance measuring device 10 detects the reflected light 32 from the finger 50 by the light receiving unit 2. The position information of the finger 50 is detected from the scan angle in the emission angle control unit 5 when the reflected light 32 is detected and the distance calculated by the control unit 6. The optical distance measuring device 10 can detect not only the position information of the finger 50 but also a predetermined operation by detecting a time transition of the position of the finger 50. For example, it is possible to detect operations similar to those of a smartphone and a tablet, such as tap, flick, swipe, pinch-in, and pinch-out. In order to perform a predetermined operation when the finger 50 touches the video screen 36, it is preferable to perform scanning with a height as low as possible so that the emitted light 31 is positioned close to the installation surface 33. For example, in FIG. 3, it is desirable that the vertical distance y between the emitted light 31 and the installation surface 33 is 20 mm or less.

Here, an angle measurement method, a time measurement method, a conventional problem, and a solution to the measurement object 3 in the optical distance measuring device 10 will be described.

First, a method for measuring the angle of the measuring object 3 will be described. FIG. 6 is a diagram showing the relative relationship of the angle control signal 51, the start pulse 41, the light reception signal 211, and the gate pulse 212 shown in FIG. is there. The light intensity of the emitted light 31 is modulated ON / OFF in synchronization with the start pulse 41 by the emitted light modulator 7. At this time, the light reception signal 211 obtained by the light receiving unit 2 when the finger 50 is irradiated with the emitted light 31 has a predetermined finite magnitude with respect to the emission angle of the emitted light 31. As shown in the figure, the envelope becomes a time response that decreases after the amplitude increases to maintain a constant value. At this time, the threshold determination unit 21 monitors the amplitude of the light reception signal 211 in FIG. 6, and when the voltage amplitude continues to exceed the predetermined threshold V _TH for a time longer than two periods of the start pulse 41, the gate in FIG. Output a pulse. And the control part 6 recognizes that there exists the measuring object 3 in the period when the gate pulse which the threshold value determination part 21 outputs is High. The control unit 6 accumulates the emission angle command value in the temporary storage area such as a memory while the gate pulse output from the threshold determination unit 21 becomes High, calculates the average value thereof, and obtains the angle information of the finger 50. .

Next, the internal configuration and operation of the threshold determination unit 21 will be described. FIG. 7 is a block diagram showing an internal configuration of the threshold determination unit 21 in FIG. The threshold determination unit 21 includes a voltage comparison unit 71, a continuous number counting unit 72, and a gate pulse generation unit 73. Voltage comparator 71 sends a pulse which becomes Low when it becomes High, less than the threshold value _{V TH} when the voltage amplitude of the received light signal 211 that is input is equal to or greater than the threshold value _{V TH} to the continuous counting section 72. The continuous number counting unit 72 counts the number of pulses that have continuously arrived from the voltage comparison unit 71, and generates a control signal that sets the output of the gate pulse generation unit to High when the count value becomes 2 or more. To the unit 73. The continuous number counting unit 72 is a control signal for setting the output of the gate pulse generating unit to Low when the number of pulses does not change even after a time of 2T or more has elapsed with reference to the repetition period T of the start pulse 41. Is transmitted to the gate pulse generator 73, and the count value is reset. The gate pulse generator 73 outputs a High or Low gate pulse 212 based on the control signal received from the continuous number counter.

Next, a method for measuring the time of the measuring object 3 in the optical distance measuring device 10 will be described. FIG. 8 shows the relative relationship of the start pulse 41, the light reception signal 211, and the stop pulse 42 in FIG. 2. Here, the portion where the gate pulse shown in FIG. 6 is in a high state for explanation of the time measurement operation. It is the figure which expanded and showed only. The stop pulse 42 is obtained by pulsing the light reception signal 211 using 0V as a reference voltage. The time measuring unit 4 measures the time difference _TL between the start pulse 41 and the stop pulse 42, and the control unit 6 converts the time difference _TL into distance information by the equation (1).

Next, conventional problems will be described. As conventional problems, circuit delay time and variation in time resolution, which are factors that reduce the measurement accuracy of the optical round-trip time, will be described.

When the measurement object 3 and was placed in the position of 50 cm, the time difference T _D is expected in the start pulse 41 and the stop pulse 42,
T _D = 0.5 m × 2 / (3.0 × 10 ⁸ m / s) = 3.3 nsec (2)
It becomes. However, in actuality, there is a delay time from when the light receiving unit 2 receives the reflected light 32 until the light reception waveform is output, and a delay time until the light reception pulse generating unit 8 outputs the stop pulse 42. When _TL shown in FIG. 3 is actually measured, a value of about 53 nsec is obtained. Therefore, if the circuit delay time generated in the optical distance measuring device 10 is T _C , the remaining about 50 nsec excluding the expected time difference T _D = 3.3 nsec from T _L = 53 nsec corresponds to the circuit delay time T _C. To do. Further, the relationship of the expression (3) is established between the time difference T _L between the start pulse 41 and the stop pulse 42, the expected time difference T _D, and the circuit delay time T _C.
T _L = T _D + T _C (3)
Note that the repetition period T of the start pulse 41 needs to be a time that is at least twice the time difference _TL . For example, the repetition period T may be set to 500 nsec. Here the circuit delay time T _C, the variation individual differences with the electronic circuit, and further since the changes its value depending on the ambient temperature of the operating environment and causes a decrease of the distance measurement accuracy of the optical distance measuring device 10. Therefore, it is necessary to correct the circuit delay time T _C in a manner described below.

Next, the temporal resolution variation, which is the second factor that reduces the measurement accuracy of the optical round trip time in the optical distance measuring device 10, will be described.

FIG. 9 is a diagram showing functional blocks when a TDC (Time Digital Conversion) method, which is a time measurement method using a delay element, is used as a premise of the present embodiment. The time difference _TL between the start pulse 41 and the stop pulse 42 is measured as a count value by the time measuring unit 4 configured by the circuit of FIG. First, the circuit operation of FIG. 9 will be described.

When the start pulse 41 is input to the circuit of FIG. 9, the pulse propagates through the loop of the NOT gates 91 connected in an odd number of N stages to enter an oscillation state. Further, a circulation counter unit 92 is connected to the subsequent stage of the Nth NOT gate, and an inner counter unit 93 is connected to each NOT gate 91, and at the timing when the stop pulse 42 arrives at the D-type flip-flop 95, A value obtained by multiplying the circulation counter unit 92 by N by the multiplication unit 94 and the count value of the in-circumference counter unit 93 is output as a count value C. Here, since a predetermined delay time ΔT is accumulated when the signal passes through each NOT gate 91, the input time difference between the two systems of signals can be measured by using the circuit of FIG. Here, when the time difference T _L between the start pulse 41 and the stop pulse 42, ΔT is the time resolution corresponding to the delay time of each NOT gate, and C is the count value output by the time measuring unit 4, an equation ( The relationship 4) holds.
T _L = C × ΔT (4)
For example, when the time difference _TL is 53.3 nsec, the counter value C = 1066 is measured if the time resolution of the time measuring unit 4 is ΔT = 50 psec.

Here, a case is considered where the time resolution ΔT is changed from 50 psec to 49 psec due to individual differences of the time measuring unit 4 and temperature changes. As before, if the time difference _TL is 53.3 nsec, the count value C is
C = 53.3 nsec / 49 psec = 1087 (5)
As measured. When the control unit 6 does not have a mechanism for detecting that the time resolution ΔT has changed, the control unit 6 calculates the optical round-trip time with the measurement object 3 based on this count value.
T _L = 1087 × 50 psec = 54.4 nsec (6)

Considering the case where where the circuit delay time _{T C} is known in advance when is 50nsec, 4.4Nsec control unit 6 except the 50nsec of circuit delay time _{T C} from the time difference _{T L} is the optical round trip time _{T D} Judge. When the control unit 6 calculates the distance using the optical round trip time T _D,
^{L = 4.4nsec × (3.0 × 10} 8 m / s) / 2 = 66cm ... (7)
Thus, a distance 16 cm longer than the actual value is calculated. As described above, the variation in the time resolution ΔT becomes a factor of reducing the distance measurement accuracy of the optical distance measuring device 10. Further time resolution △ T is variation and individual difference of the time measuring unit 4, and further since the changes its value depending on the ambient temperature of the operating environment, it is necessary to correct in conjunction with the circuit delay time T _C by the method described below .

Therefore, in this embodiment, in order to prevent a decrease in distance measurement accuracy due to the above-described variation in circuit delay time T _C and time resolution ΔT, variations in circuit delay time T _C and time resolution ΔT are corrected. I did it. Hereinafter, a specific example of this embodiment will be described.

FIG. 10 is a block diagram showing a configuration example of the optical distance measuring device in the present embodiment. 10, constituent elements having the same functions as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. 10 differs from FIG. 2 in that a first reference object 101 and a second reference object 102 are installed as the optical distance measuring device 20. That is, the first reference object 101 and the second reference object 102 are installed at predetermined positions in the optical distance measuring device 20, and the emitted light 31 emitted from the emission angle control unit 5 is emitted. is, by receiving the reflected light 32 by the light receiving unit 2 corrects the circuit delay time T _C, and time resolution △ T.

FIG. 11 shows an example in which the optical distance measuring device 20 is used on the image projection apparatus in the present embodiment. In FIG. 11, the image projection device 12 </ b> A has a built-in optical distance measuring device 20, and the optical distance measuring device 20 has the first reference object 101 and the second object at an angle outside the use range of the optical distance measuring device 20. The reference object 102 is installed. That is, the distance of the exit angle controller 5 and the light receiving portion 2 △ a first reference object 101 L _1, the angle theta _1, the distance between the second reference object 102 L _2, the angle and theta ₂ The control unit 6 holds the values of L ₁ , θ ₁ , L ₂ , and θ ₂ as known values. In order to facilitate detection, the materials of the first reference object 101 and the second reference object 102 are different from those of the housing of the image projection device 12A, and the reflectance is determined from the surrounding materials. May be high. Due to this reflectance difference, when the reflected light of the first reference object 101 and the second reference object 102 is received, a larger voltage amplitude is obtained in the light reception signal.

The optical distance measuring device 20 performs a measurement operation, and the count value C ₁ is measured with respect to the first reference object 101 at an angle θ ₁ and the count value C ₂ is measured with respect to the second reference object 102 at an angle θ _2. assuming _that, C 1, _{C 2} each following formula (8) can be expressed by equation (9).
C ₁ = T _L1 / ΔT ₁ = (T _D1 + T _C1 ) / ΔT ₁ (8)
C ₂ = T _L2 / ΔT ₂ = (T _D2 + T _C2 ) / ΔT ₂ (9)
Here, T _D1 and T _D2 are optical round trip times corresponding to the distance between the first and second reference objects, respectively, and T _C1 and T _C2 are generated when measuring the optical round trip times of the first and second reference objects, respectively. The circuit delay times ΔT ₁ and ΔT ₂ are the time resolutions when measuring the optical round trip time of the first and second reference objects, respectively.

In the above formulas (8) and (9), the circuit delay time and the time resolution are different for each measurement, but the main factor that the circuit delay time and the time resolution fluctuate is the temperature change of the circuit element. That is, by measuring the count value C ₂ from the measured count value C ₁ in a very short time, the influence of the temperature change is very small, the value of the circuit delay time and time resolution can be regarded as equivalent. For example, when the rotary mirror included in the emission angle control unit 5 is rotationally driven at 10 Hz, one scan cycle is 100 ms, and the optical reciprocation time corresponding to the first and second reference objects and the measurement object during one scan. Can be measured.

If regarded as equal values of circuit delay time T _C, and time resolution △ T, equation (8) and (9) can be simplified as follows.
C ₁ = T _L1 / ΔT = (T _D1 + T _C ) / ΔT (10)
C ₂ = T _L2 / ΔT = (T _D2 + T _C ) / ΔT (11)
Here, subtracting the equation (10) from equation (11), erases the term of circuit delay time T _C, it is possible to calculate the current value of the time resolution △ T.
ΔT = (T _D2 −T _D1 ) / (C ₂ −C ₁ ) (12)

Further, by substituting equation (12) into equation (10) can calculate the current value of the circuit delay time T _C.
T _C = (C ₁ T _D2 -C ₂ T _D1 ) / (C ₂ -C ₁ ) (13)

As described above, if two reference objects having different distances and angles from the emission angle control unit 5 and the light receiving unit 2 are used, the current values of circuit delay time and time resolution can be calculated.

Furthermore, the time count value C and the expression of the measuring object (12), which is calculated by equation (13) △ T, and calculates the distance to the measurement object using the T _C. That is, Equation (12), using the current value of the indicated △ T, T _C in the equation (13), the distance L between the optical distance measuring device 10 measuring object,
L = c × (T _L −T _C ) / 2
= C × {CΔT- (C ₁ T _D2 -C ₂ T _D1 ) / (C ₂ -C ₁ )} / 2 (14)
It can be expressed. Here, T _L = CΔT. Therefore, by using the equation (14), the distance to the measurement object can be obtained with high accuracy even if the circuit delay time or the time resolution changes. Further, in Formula (14), if C ₁ and C ₂ and the count value C of the measurement object are derived using the count values averaged by the time averaging processing unit 9, more accurate measurement is possible. Become. In particular, when the optical distance measuring device 20 of the present embodiment is built in the image projection device 12A, the amount of temperature change in the housing of the image projection device is very large, so that the reduction in measurement accuracy due to temperature change can be suppressed. Play.

In the above description, each of the first reference object 101 and the second reference object 102 is described as having the same distance from the emission angle control unit 5, the distance between the angle and the light receiving unit 2, and the angle. However, if the distance and angle between the emission angle control unit 5 and the light receiving unit 2 are not the same, the distance and angle between the emission angle control unit 5 and each reference object, and the light receiving unit 2 and each reference object. Similarly, the circuit delay time and time resolution can be obtained from the distance and angle.

Next, the operation flow of the optical distance measuring device 20 will be described. FIG. 12 shows a flowchart from the power-on to the power-off in the optical distance measuring device 20 which is a premise of the present embodiment until the power is turned off. In this example, distance measurement is performed as the position information.

In FIG. 12, first, when the optical distance measuring device 20 is turned on (111), the optical distance measuring device 10 performs initial setting of each operation block (112). Thereafter, it is determined whether or not the user performs an input operation by repeatedly changing the position of the finger (113). When the interruption of the input operation of the user is detected, it is determined whether or not a predetermined time has elapsed (115), and if the predetermined time has elapsed, the process of determining whether or not the user is operating is repeated (113).

If it is determined that the user continues the input operation by repeatedly changing the position of the finger, the circuit delay time and the time resolution are corrected using the method described above (116). Then, the optical distance measuring device 20 measures the finger position information (117). Then, it is determined whether a predetermined time has elapsed since the previous circuit delay time / time resolution correction (118). When a predetermined time has elapsed since the previous correction, the process again determines whether the user is operating (113). If the user is operating, the circuit delay time and time resolution correction are repeated (116). If the predetermined time has not elapsed in step 118, the user has not performed an input operation (119). If the power switch is turned off (120), the optical distance measuring device 20 performs a power-off process. To end the operation (121).

If the user performs an input operation in step 119, the process returns to step 117, and the optical distance measuring device 20 measures the finger position information. Note that the period in which the optical distance measuring device 20 corrects the circuit delay time and the time resolution is arbitrary, and the correction may be performed for each measurement, or may be performed for each measurement. .

As described above, this embodiment is an optical distance measuring method for an optical distance measuring device that calculates a distance based on a time difference between an emitted light signal and a received light signal, and the optical distance measuring device receives light received from a light receiving unit that receives the received light signal. A circuit having at least two reference objects having different distances and angles, measuring a time difference with respect to a plurality of reference objects by a time measuring unit for measuring a time difference, and performing a predetermined calculation on the plurality of time differences and having a light receiving unit The delay time and the measurement resolution of the time measurement unit are calculated, and the distance from the measurement object is calculated based on the calculation results of the circuit delay time and the measurement resolution.

An optical distance measuring device that measures a distance from the measurement object based on a time difference between an outgoing light signal to the measurement object and a light reception signal that receives reflected light from the measurement object. A light source unit that emits light emitted from the light source, a light receiving unit that receives reflected light from the measurement object, an emission angle control unit that controls the emission angle of the emitted light, a time measurement unit that measures a time difference, and a light receiving unit A first reference object having a first predetermined distance and a first predetermined angle; a second reference object having a second predetermined distance and a second predetermined angle; a light source; An angle changing unit and a control unit that controls the time measuring unit, and the first reference object and the second reference object are different from each other in the first predetermined distance and the second predetermined distance. Constitute.

An image projection apparatus comprising an image projection unit and an optical distance measuring device, wherein the image projection unit outputs an image projection light source and an image signal supplied from an external device using light emitted from the image projection light source. A light control unit that generates an optical image based on the image, a video control unit that outputs a control signal to the light source for image projection and the light control unit according to a video signal supplied from an external device, and an output video of the light control unit The optical distance measuring device controls the emission angle of the emitted light, the light source unit that emits the emitted light to the measurement object, the light receiving unit that receives the reflected light from the measurement object, An emission angle control unit that performs measurement, a time measurement unit that measures a time difference between an outgoing light signal to the measurement object and a received light signal that has received reflected light from the measurement object, a first predetermined distance from the light reception unit, and a first A first reference object having a predetermined angle and a second predetermined object And a second reference object having a second predetermined angle and a control unit for controlling the light source unit, the emission angle changing unit, and the time measuring unit, and the first reference object and the second reference object The reference object is configured such that the first predetermined distance is different from the second predetermined distance, and the reference object includes a communication unit that transmits position information of the measurement object detected by the control unit to the video control unit.

Thereby, even when the circuit delay time of the light receiving circuit and the time resolution of the time measuring circuit change in a short time, the optical distance measuring device, the optical distance measuring method, which can measure the distance to the measurement object with high accuracy, And an image projection apparatus provided with the same can be provided.

In this embodiment, an application example of the optical distance measuring apparatus described in the first embodiment will be described with reference to FIGS.

FIG. 13 shows an example in which the optical distance measuring device 20 is installed above the entrance / exit 121. It is possible to count the height of the passer-by 122 and the number of passers-by who have passed through the doorway by scanning the outgoing angle of the outgoing light by the optical distance measuring device 20 and the temporal change in the detected position information.

FIG. 14 shows an example in which the optical distance measuring device 20 is installed above the vehicle gate 131 of the automobile. In this case as well, the height measurement of the passing vehicle 132 and the number of passing vehicles can be counted by scanning the outgoing angle of the outgoing light by the optical distance measuring device 20 and the temporal change in the detected position information.

FIG. 15 shows an example in which the optical distance measuring device 20 is installed on the upper and side surfaces of the gate 141 of the belt conveyor 142 that moves the load. In this case as well, it is possible to measure dimensions such as the height, width, and depth of the cargo 143 conveyed by the belt conveyor, and to count the number of passing cargos 143.

FIG. 16 shows an example in which the optical ranging devices 20 are installed in multiple stages and the unevenness on the surface of the three-dimensional object 151 such as a work of art is measured. In particular, a high-resolution optical distance measuring device is required to store 3D data such as artworks, and the method for improving the distance measuring accuracy described in this embodiment is very effective.

As described above, the optical distance measuring device can be connected not only to the image projection device but also to various external devices and applied to various applications.

Note that if a plurality of optical distance measuring devices are arranged in the vicinity and are used simultaneously, interference may occur in the received light signal. That is, the case where the emitted light of the first optical distance measuring device interferes with the light reception signal of the adjacent optical distance measuring device can be considered. As a solution for this, for example, a method of separating signals spatially and temporally can be considered. That is, the scanning angle of the emission angle control unit may be shifted from each other so that the emitted light of each optical distance measuring device does not overlap, and the received light signal may be processed at each timing by the light receiving unit. Moreover, the method of separating by wavelength may be used. In other words, the wavelength of the emitted light of the first optical distance measuring device is λ1, the wavelength of the emitted light of the second optical distance measuring device is λ2, and it is possible to cope by adding a wavelength separation filter to the light receiving unit. Become. Further, a method of separating by frequency may be used. That is, the laser drive frequency of the light source unit of the first optical distance measuring device is f1, the laser drive frequency of the light source unit of the second optical distance measuring device is f2, and a bandpass filter is added to the light receiving unit. May be.

The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of each embodiment.

In addition, each of the above-described configurations may be configured such that a part or all of the configuration is configured by hardware, or is realized by executing a program by a processor. Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. In practice, it can be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 1 ... Light source part, 2 ... Light receiving part, 3 ... Measurement object, 4 ... Time measurement part, 5 ... Output angle control part, 6 ... Control part, 7 ... Output light modulation part, 8 ... Light reception pulse generation part, 9 ... Time averaging processing unit, 10, 20 ... optical distance measuring device, 21 ... threshold determination unit, 11 ... communication unit, 12 ... external device, 12A ... video projection device, 31 ... outgoing light, 32 ... reflected light, 33 ... installation Surface 34, projection lens 35, reflecting mirror 36 image screen 37 37 focus ring 41 start pulse 42 stop pulse 43 image projection unit 44 image control unit 45 light source for image projection , 46: Light control unit, 47: Projection lens, 48 ... Reflection mirror, 49 ... External device, 50 ... Finger, 51 ... Angle control signal, 71 ... Voltage comparison unit, 72 ... Continuous number counting unit, 73 ... Gate pulse generation 91, NOT gate, 92 ... lap count , 93 ... Intra-circumference counter part, 94 ... Multiplication part, 95 ... D-type flip-flop, 101 ... First reference object, 102 ... Second reference object part, 121 ... Entrance / exit, 122 ... Passerby, 131 ... Vehicle gate, 132 ... passing vehicle, 141 ... gate, 142 ... belt conveyor, 143 ... cargo, 151 ... three-dimensional model, 211 ... light reception signal, 212 ... gate pulse

Claims

An optical distance measuring device that measures a distance from the measurement object based on a time difference between an output light signal to the measurement object and a light reception signal that receives reflected light from the measurement object,
A light source unit for emitting light to the measurement object;
A light receiving unit for receiving reflected light from the measurement object;
An emission angle control unit for controlling the emission angle of the emitted light;
A time measuring unit for measuring the time difference;
A first reference object having a first predetermined distance and a first predetermined angle from the light receiving unit; and a second reference object having a second predetermined distance and a second predetermined angle;
A control unit for controlling the light source unit, the emission angle changing unit, and the time measuring unit,
The optical distance measuring device, wherein the first reference object and the second reference object are different from each other in the first predetermined distance and the second predetermined distance.
The optical distance measuring device according to claim 1,
The control unit controls the light source unit and the emission angle changing unit to emit light to the first reference object and the second reference object,
The time measurement unit measures a first time difference with respect to the first reference object and a second time difference with respect to the second reference object;
The control unit performs a predetermined calculation on the first time difference and the second time difference to calculate a circuit delay time of the light receiving unit and a measurement resolution of the time measurement unit. Optical distance measuring device.
The optical distance measuring device according to claim 2,
The said control part calculates the distance with the said measurement object based on the calculation result of the said circuit delay time and the said measurement resolution, The optical ranging device characterized by the above-mentioned.
The optical distance measuring device according to claim 3,
The optical distance measuring device is
An outgoing light modulator for pulse-modulating the outgoing light;
A light reception pulse generator for pulsing the light reception signal of the reflected light,
The optical distance measuring device, wherein the time measurement unit measures the time difference based on an outgoing pulse signal output from the outgoing light modulation unit and a received light pulse signal output from the received light pulse generation unit.
The optical distance measuring device according to claim 4,
The optical distance measuring device is
A time averaging processing unit that outputs a plurality of time average values of the time differences output by the time measuring unit;
The said control part calculates the distance with the said measurement object based on the said time average value which the said time averaging process part outputs, The optical ranging apparatus characterized by the above-mentioned.
The optical distance measuring device according to claim 5,
The optical distance measuring device, wherein the control unit calculates the circuit delay time and the measurement resolution based on the time average value output from the time averaging processing unit.
An optical distance measuring method of an optical distance measuring device for calculating a distance by a time difference between an emitted light signal and a received light signal,
The optical distance measuring device includes at least two reference objects having different distances and angles from a light receiving unit that receives the light reception signal,
Measure the time difference with respect to the plurality of reference objects by the time measurement unit that measures the time difference,
A predetermined calculation is performed on the plurality of time differences to calculate a circuit delay time of the light receiving unit and a measurement resolution of the time measuring unit,
An optical distance measuring method comprising: calculating a distance from a measurement object based on the calculation result of the circuit delay time and the measurement resolution.
An image projection device comprising an image projection unit and an optical distance measuring device,
The image projection unit is
A light source for image projection, a light control unit for generating an optical image based on a video signal supplied from an external device using light emitted from the light source for video projection, and the video signal supplied from the external device according to the video signal An image projection light source, an image control unit that outputs a control signal to the light control unit, and a projection lens that expands an output image of the light control unit,
The optical distance measuring device includes a light source unit that emits light emitted to a measurement object, a light receiving unit that receives reflected light from the measurement object, an emission angle control unit that controls an emission angle of the emission light, A time measuring unit for measuring a time difference between an outgoing light signal to the measuring object and a received light signal that receives reflected light from the measuring object; a first predetermined distance and a first predetermined angle from the light receiving unit; Controlling the first reference object forming the second reference object forming the second predetermined distance and the second predetermined angle, the light source unit, the emission angle changing unit, and the time measuring unit. The first reference object and the second reference object are different in the first predetermined distance and the second predetermined distance, and the measurement detected by the control unit. A communication unit that transmits position information of the object to the video control unit; An image projection device characterized by the above.