JP2005024523A - Range finder and projector having range finder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a range finder which can measure distance with high accuracy using a simple configuration, utilizing a single light source and a single light receiving device. <P>SOLUTION: The range finder comprises a light source drive signal generator 11 which can change frequency; a light source 12; a light-receiving element 13; a process operation circuit which calculates the distance to an object, corresponding to a round trip period from an acquired overlap status by acquiring the overlap status by a gap corresponding to the round-trip period with a periodic width of a projected light and the periodic width of a received reflected light. The process operation circuit comprises a current voltage transducer 14; an OR circuit 15 which inputs a driving signal from the light source drive signal generator 11 and a voltage signal from the current voltage transducer 14 and outputs a logical sum; a low-pass filter circuit 16 smoothing in time the logical sum output from the OR circuit 15; an A/D converter 17 which digitizes the output; an arithmetic circuit 18 which calculates the distance between the light source 12 and the object from an amplitude of the logical sum that is smoothed in time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a distance measuring device and a projector having the distance measuring device.

Conventionally, as a distance measuring device, a surface of a measurement object is irradiated with a plurality of light whose amount of light emission is modulated with a predetermined frequency, and the reflected light is detected by a detection element capable of detecting only light in a certain direction. An optical shape sensor that acquires distance information from phase information obtained therefrom is disclosed (for example, see Patent Document 1). In addition, a distance measuring device is disclosed that measures the distance to the distance measuring object based on the time associated with the light projection toward the distance measuring object and the reception of the reflected light (see, for example, Patent Document 2). Further, a distance measuring device is disclosed that transmits ultrasonic waves to a detection object, receives a reflected wave thereof, and calculates a distance to the object based on the number of clocks from transmission to reception signal (see, for example, Patent Document 3). ).
JP 2003-42733 A Japanese Patent Laid-Open No. 11-325823 Japanese Patent Laid-Open No. 11-44759

  However, the optical shape sensor of Patent Document 1 requires a plurality of light sources, and the distance measuring device of Patent Document 2 requires signal processing means such as a light reception time setting for avoiding the influence of disturbance light. The device requires a complicated mechanism such as an ultrasonic transmission device.

  A distance measuring device of the present invention includes a light source drive signal generator that generates a drive signal for driving a light source at a predetermined frequency, a light source that emits light according to the drive signal and projects a projection light beam on an object, and a proximity to the light source. To obtain an overlap state due to a deviation corresponding to a round trip time between the periodic width of the projected light beam and the periodic width of the received reflected light beam, and reciprocating from the acquired overlap state. A processing operation circuit for calculating a distance to an object corresponding to time, a logic circuit such as an OR circuit or an AND circuit for obtaining an overlapping state, and a low-pass filter circuit for smoothing In order to obtain the overlap between the reflected light and the projected light, the amplitude control circuit and the smoothing Or a combination of pass filter circuit. In this case, by controlling the frequency of the driving pulse of the light source driving signal generator corresponding to the expected distance from the object, it is possible to acquire the distance of the object with high accuracy.

  The projector using the distance measuring device of the present invention uses this distance measuring device for adjusting the focus of the projection lens of the projection device.

  The present invention is a distance measuring device with a simple configuration using a single light source and a single light receiving device, and by changing the frequency of the light source driving signal, the distance from the object can be accurately determined corresponding to the distance. There is an effect that it can be measured.

  The purpose of providing a distance measuring device that can measure distances with high accuracy with a simple configuration using a single light source and a single light receiving device is to gate the pulse signal that drives the light source and the pulse signal from the light receiving device. Smooth the binary signal processed by the circuit, or smooth the waveform that controls the amplitude by adding the pulse of the projected ray and the pulse of the reflected ray at the time of projection, and proportional to the amplitude from the smoothed amplitude This was realized by calculating the distance in relation.

  FIG. 1 is a schematic block diagram of a distance measuring apparatus according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram of a distance measuring mechanism when the frequency of the light source in FIG. 1 is 100 MHz. FIG. 4 is an explanatory diagram of a temporal relative relationship between a light projection cycle of a light source and a light reception cycle of a light receiving element in FIG.

  The distance measuring device 10 includes a light source drive signal generator 11 that generates a drive signal for driving a light source at a predetermined frequency, a light source 12 such as an LED that emits light according to the drive signal and projects a projection light beam 51 on an object, From a light receiving element 13 such as a phototransistor that receives a reflected light beam 52 from an object and converts it into a current, a current-voltage converter 14 that converts a current generated in the light receiving element 13 into a voltage, and a light source drive signal generator 11 An OR circuit 15 that inputs a drive signal and a voltage signal from the current-voltage converter 14 and outputs a logical sum; a low-pass filter circuit 16 that temporally smoothes the logical sum output from the OR circuit 15; The A / D conversion circuit 17 for digitizing the output of the low-pass filter circuit 16 and the output of the A / D conversion circuit 17 are input to calculate the distance between the light source 12 and the object 50 and to obtain distance information. And an arithmetic circuit 18 and output as 31.

The light beam projected from the light source 12 enters the light receiving element 13 after being delayed by a time that travels a distance twice as long as the distance between the light source 12 and the object 50. The wavelength λ of a light beam with a frequency of 100 MHz is
λ = speed of light / frequency = 3 × 10 ⁸ (m / sec) / 10 ⁸ (/ sec) = 3 (m)
It is. The cycle p of one cycle is
p = 1 / frequency = 1/10 < ⁸ > (/ sec) = 1 * 10 < ^-8 > (sec)
Therefore, the light beam is projected for a period of 5 × 10 ⁻⁷ (sec), which is 1/2 of that.

2 is L (m), the delay d (sec) between the projection timing of the light source and the light receiving timing of the light receiving element 13 is the wavelength λ = 3 ( The period for m) is p = 1 × 10 ⁻⁸ (sec), so
d = 2L (m) × 10 ⁻⁸ (sec) / 3 (m) = (20/3) L × 10 ⁻⁷ (sec)
And
For L = 0 (m), d = 0,
At L = 0.375 (m), d = 2.5 × 10 ⁻⁷ (sec)
At L = 0.75 (m), d = 5 × 10 ⁻⁷ (sec)
It becomes.

  FIG. 3 shows the logical sum X and logical sum of the OR circuit 15 when the output from the light source drive transmitter 11 is input to the input A of the OR circuit 15 and the light reception signal from the current-voltage converter 14 is input to the input B. An output x when X is smoothed temporally by the low-pass filter circuit 16 is schematically shown. From the figure, when the amplitude when the continuous output X is temporally smoothed by the low-pass filter circuit 16 is 4/4, the smoothed amplitude is 2/4 when L = 0, When L = 0.375 (m), it is 3/4, and when L = 0.75 (m), it is 4/4. Between 2/4 and 4/4, the linearity is proportional to L. Has changed. Therefore, the distance L (m) between the light source 12 and the light receiving element 13 and the object 50 can be easily calculated by calculating the amplitude of the output x when smoothed in time by the low-pass filter circuit 16 by the calculation circuit 18. Can do.

  However, when the frequency of the projection light beam 51 from the light source 12 is 100 MHz, a cycle of 0 to 0.75 m is repeated when L is 0.75 m or more, so the range of distance measurement is 0.75 m or less. . What is necessary is just to change the frequency of the projection light beam 51 from the light source 12, when measuring the distance beyond this. For example, if the frequency is 10 MHz, the range of distance measurement is 7.5 m or less. By changing the frequency of the light source drive signal generator 11 corresponding to the measurement distance, the distance can be measured with high accuracy in each range.

  Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a schematic block diagram of a distance measuring apparatus according to the second embodiment of the present invention, and FIG. 5 is a schematic diagram of a distance measuring mechanism when the frequency of the light source in FIG. 4 is 100 MHz. FIG. 6 is an explanatory diagram of the temporal relative relationship between the light projecting cycle of the light source and the light receiving cycle of the light receiving element in FIG.

  In the first embodiment, the drive signal from the light source drive signal generator 11 and the light-receiving signal of the light-receiving element 13 subjected to current-voltage conversion are input to the OR circuit 15 and output, and the logical sum X is temporally smoothed to The distance between the light source 12 and the object 50 is calculated from the amplitude x. In the second embodiment, the driving signal A from the light source driving signal generator 11 and the light receiving signal B of the light receiving element 13 which has been converted from current to voltage are AND circuits. The logical product X inputted and outputted to 25 is smoothed temporally, and the distance between the light source 12 and the object 50 is calculated from the amplitude x. Since other elements and operations are the same as those in the first embodiment, the same reference numerals and names are used for the same elements, and common parts are omitted.

  FIG. 6 shows the logical product X and logical product of the AND circuit 15 when the output from the light source drive transmitter 11 is input to the input A of the AND circuit 25 and the light reception signal from the current-voltage converter 14 is input to the input B. An output x when X is smoothed temporally by the low-pass filter circuit 16 is schematically shown. From the figure, when the amplitude when the continuous output X is temporally smoothed by the low-pass filter circuit 16 is 4/4, the smoothed amplitude is 2/4 when L = 0, L = 0.375 (m) = 1/4, L = 0.75 (m) = 0, and linearly varies between 2/4 and 0 in inverse proportion to L . Therefore, the distance L (m) between the light source 12 and the light receiving element 13 and the object 50 can be easily calculated by calculating the amplitude of the output x when smoothed in time by the low-pass filter circuit 16 by the calculation circuit 18. Can do.

  Also in this case, when the frequency of the projected light beam 51 from the light source 12 is 100 MHz, the cycle of 0 to 0.75 m is repeated when L is 0.75 m or more, and the range of distance measurement is 0.75 m or less. It becomes. What is necessary is just to change the frequency of the projection light beam 51 from the light source 12, when measuring the distance beyond this. For example, if the frequency is 50 MHz, the range of distance measurement is 1.5 m or less. By changing the frequency of the light source drive signal generator 11 corresponding to the measurement distance, the distance can be measured with high accuracy in each range.

  Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a schematic block diagram of a distance measuring apparatus according to the third embodiment of the present invention, and FIG. 8 is a schematic diagram of a distance measuring mechanism when the frequency of the light source in FIG. 7 is 100 MHz. FIG. 9 is an explanatory diagram of the temporal relative relationship between the light projecting cycle of the light source and the light receiving cycle of the light receiving element in FIG.

  In the first embodiment, the OR of the drive signal from the light source drive signal generator 11 and the light-receiving signal of the light-receiving element 13 subjected to current-voltage conversion is input to the OR circuit 15 and output, and the amplitude is smoothed. The distance between the light source 12 and the object 50 is calculated from the input signal, and in the second embodiment, the drive signal from the light source drive signal generator 11 and the light-receiving signal of the light-receiving element 13 that has undergone current-voltage conversion are input to the AND circuit 25. The output logical product is temporally smoothed and the distance between the light source 12 and the object 50 is calculated from the amplitude. In the third embodiment, a part of the projected light beam 51 of the light source 12 is passed through the optical fiber 53. The light is input to the light receiving element 13 together with the reflected light 52, and the amplitude of the generated output is controlled by the amplitude control circuit 35 so as to become a constant amplitude, and the controlled output is smoothed over time to calculate the distance. Since other elements and operations are the same as those in the first embodiment, the same reference numerals and names are used for the same elements, and common parts are omitted.

  A part of the projection light beam 51 from the light source 12 is directly input as the input A through the optical fiber 53 together with the input B of the reflected light beam 52 to the image receiving device 13 in FIG. And the sum C of the reflected rays. Therefore, although the amplitude is approximately doubled at the position where the two light beams overlap, what is required here is the period during which both the light beams are input, so that the amplitude control circuit 35 outputs both large and small amplitudes as an output D having a constant amplitude. Then, it is smoothed in time by the low-pass filter circuit 16 and becomes an output x.

  FIG. 9 schematically shows the periods of inputs A and B and outputs C, D, and x. As shown in the figure, when the amplitude when the continuous output D is temporally smoothed by the low-pass filter circuit 16 is set to 4/4, 2/4 in the case of L = 0 as in the first embodiment, L = 0.375 (m) 3/4, L = 0.75 (m) 4/4, linearly proportional to L between 2/4 and 4/4. It has changed. Therefore, the distance L (m) between the light source 12 and the light receiving element 13 and the object 50 can be easily calculated by calculating the amplitude of the output x when smoothed in time by the low-pass filter circuit 16 by the calculation circuit 18. Can do. The logical sum obtained by the OR circuit 15 in the first embodiment is optically obtained in the second embodiment.

  Here again, when the frequency of the projection light beam 51 from the light source 12 is 100 MHz, the cycle of 0 to 0.75 m is repeated when L is 0.75 m or more, and the range of distance measurement is 0.75 m or less. Become. What is necessary is just to change the frequency of the projection light beam 51 from the light source 12, when measuring the distance beyond this. For example, if the frequency is 5 MHz, the range of distance measurement is 15 m or less. By changing the frequency of the light source drive signal generator 11 corresponding to the measurement distance, the distance can be measured with high accuracy in each range.

  Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a schematic block diagram of a projector using the distance measuring apparatus according to the fourth embodiment of the present invention.

  Here, the projector is described as a liquid crystal projector having a liquid crystal display unit as an image display unit. However, the present invention is not limited to this, and a DLP (digital light processor) system having a DMD (digital light processor) display unit in the image display unit is not limited thereto. It may be a projector or a three-pipe type.

  The liquid crystal projector 1 includes a projection device 20 having a projection lens 21, a liquid crystal display unit 22, and a focus adjustment unit 23, an image control unit 24 that controls an image of the liquid crystal display unit 22, a projection surface distance measuring device 30, CPU60 which controls operation | movement. The projection surface distance measuring device 30 is the distance measuring device 10 described in the first embodiment, and a light source driving signal generator 11 that generates a driving signal for driving a light source at a predetermined frequency, and light emission according to the driving signal. A light source 12 such as an LED that projects a projection light beam onto the object, a light receiving element 13 such as a phototransistor that receives a reflected light beam from the object and converts it into a current, and converts a current generated by the light receiving element 13 into a voltage. Current-to-voltage converter 14, OR circuit 15 for inputting a drive signal from light source drive signal generator 11 and a voltage signal from the current-voltage converter and outputting a logical sum, and logical sum output from OR circuit 15 The low-pass filter circuit 16 for smoothing the output of the light source, the A / D conversion circuit 17 for digitizing the output of the low-pass filter circuit 16, and the output of the A / D conversion circuit 17 are input. And an arithmetic circuit 18 for calculating the distance between the object and. The image control unit 24 controls the focus adjustment unit 23 based on the distance information calculated by the arithmetic circuit 18 to adjust the focus of the projection lens 21. Here, the projection surface distance measuring device 30 is the distance measuring device 10 described in the first embodiment, but may be the distance measuring device 10 described in the second or third embodiment.

  The present invention can be applied as a simple and highly accurate automatic distance measuring device for automatic focus adjustment in an imaging apparatus, an image projection apparatus, or the like that requires a focus adjustment for changing the distance to an object.

It is a typical block block diagram of the distance measuring device of 1st Example of this invention. It is a schematic diagram of a distance measurement mechanism when the frequency of the light source of FIG. It is explanatory drawing of the time relative relationship between the light projection cycle of the light source in FIG. 2, and the light reception cycle of a light receiving element, the content of a process, and a result. It is a typical block block diagram of the distance measuring device of the 2nd Example of this invention. It is a schematic diagram of a distance measurement mechanism when the frequency of the light source of FIG. It is explanatory drawing of the time relative relationship of the light projection cycle of a light source in FIG. 5, and the light reception cycle of a light receiving element, the content of a process, and a result. It is a typical block block diagram of the distance measuring device of the 3rd Example of this invention. It is a schematic diagram of a distance measurement mechanism when the frequency of the light source of FIG. 7 is 100 MHz. It is explanatory drawing of the time relative relationship between the light projection cycle of a light source in FIG. 8, and the light reception cycle of a light receiving element, the content of a process, and a result. It is a typical block block diagram of the projector using the distance measuring device of the 4th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal projector 10 Distance measuring device 11 Light source drive signal generator 12 Light source 13 Light receiving element 14 Current voltage converter 15 OR circuit 16 Low-pass filter circuit 17 A / D conversion circuit 18 Arithmetic circuit 20 Projection device 21 Projection lens 22 Liquid crystal display part 23 Focus adjustment unit 24 Image control unit 25 AND circuit 30 Projection surface distance measuring device 31 Distance information 35 Amplitude control circuit 50 Object 51 Projected light beam 52 Reflected light beam

Claims (8)

  A light source drive signal generator that generates a drive signal for driving a light source at a predetermined frequency, a light source that emits light according to the drive signal and projects a projection light beam on the object, and an object that is disposed in proximity to the light source The overlapping state due to the shift corresponding to the round trip time between the light receiving element that receives the reflected light from the light source and the periodic width of the projected light and the periodic width of the reflected light received is acquired, and the round trip time is handled from the acquired overlapping state. A distance measuring device comprising: a processing operation circuit that calculates a distance to an object to be processed.   The processing arithmetic circuit inputs a current-voltage converter that converts a current generated in the light receiving element into a voltage, a drive signal from the light source drive signal generator, and a voltage signal from the current-voltage converter, and inputs a logic An OR circuit that outputs a sum, a low-pass filter circuit that temporally smoothes the logical sum output from the OR circuit, an A / D conversion circuit that digitizes the output of the low-pass filter circuit, and the A / D The distance measuring device according to claim 1, further comprising: an arithmetic circuit that calculates a distance between the light source and the object from an amplitude of a logical sum smoothed in time by inputting an output of the conversion circuit.   The processing arithmetic circuit inputs a current-voltage converter that converts a current generated in the light receiving element into a voltage, a drive signal from the light source drive signal generator, and a voltage signal from the current-voltage converter, and inputs a logic An AND circuit that outputs a product, a low-pass filter circuit that temporally smoothes a logical product output from the AND circuit, an A / D conversion circuit that digitizes the output of the low-pass filter circuit, and the A / D The distance measuring apparatus according to claim 1, further comprising: an arithmetic circuit that calculates a distance between the light source and the object from an amplitude of a logical product that is input with an output of the conversion circuit and smoothed in time.   In addition to the reflected light beam, a part of the projected light beam from the light source is directly incident on the light receiving element, and the processing operation circuit includes a current-voltage converter that converts a current generated in the light receiving element into a voltage, and An amplitude control circuit that adjusts and outputs the amplitude of the output of the current-voltage converter to a constant amplitude, a low-pass filter circuit that temporally smoothes the output from the amplitude control circuit, and the output of the low-pass filter circuit is digital An A / D conversion circuit for converting the output from the A / D conversion circuit, and an arithmetic circuit for calculating a distance between the light source and the object from an amplitude smoothed in time by inputting the output of the A / D conversion circuit. The distance measuring apparatus according to 1.   The distance according to any one of claims 1 to 4, wherein the light source drive signal generator can change a frequency to be generated in accordance with a predicted distance between the light source and the object. Measuring device. In a projector including a projection device having a projection lens, a liquid crystal display unit, and a focus adjustment unit, an image control unit that controls an image of the liquid crystal display unit, a projection surface distance measurement device, and a CPU that controls the overall operation ,
The projector having a distance measuring device, wherein the projection surface distance measuring device is the distance measuring device according to any one of claims 1 to 5.   The projector having a distance measuring device according to claim 6, wherein the projector is a liquid crystal projector. The projector having a distance measuring device according to claim 6, wherein the projector is a DMD projector.

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