JP3672987B2 - Ranging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a distance measuring device of a camera, and in particular, an infrared light is projected toward a distance measuring object, and an integration for obtaining a distance to the distance measuring object from an integrated value of a distance measurement output obtained for each projection. The present invention relates to an active camera ranging device having a type ranging circuit.
[0002]
[Prior art]
A conventional active distance measuring device projects infrared light toward a distance measuring object and receives the reflected light by a light receiving element. At that time, two data are obtained: data by ratio integration obtained from the incident position on the light receiving surface (hereinafter referred to as ratio data) and data obtained by integrating the received light amount itself (hereinafter referred to as light amount data). In this case, the ratio data is generally used when the distance to the distance measuring object is short, and the light amount data is generally used when the distance is long.
[0003]
Normally, ratio data is used to determine the switching between the two data. When the distance to the object to be measured is obtained from the light quantity data, the distance is often obtained simply by the magnitude of the light quantity data.
[0004]
In the active rangefinder, when the luminance of the rangefinder object is high, the S / N ratio deteriorates due to an increase in the background photocurrent. There is a method of correcting the amount of deviation of the ratio data from the theoretical line due to the deterioration of the S / N ratio by calculating a correction amount by linear approximation from the ratio data and the photometric data.
[0005]
[Problems to be solved by the invention]
However, in the conventional technique using the ratio data and light amount data described above, if the ratio data is shifted to the near distance side due to some electromagnetic noise or AC background light noise caused by an AC light source, the object to be measured is far away. In spite of the distance, it is not possible to switch to the light quantity data, and the distance to the object to be measured is obtained from the erroneous ratio data in the short distance. Further, when the distance to the distance measurement object is obtained from the light amount data, if the reflectance of the distance measurement object is high, the distance data of the front pin becomes significant.
[0006]
Furthermore, since the active type distance measuring device performs a linear approximation, it requires a multiplication for the calculation of the correction amount, which takes time. Further, even if the same condition is used, the amount of deviation in the ratio data varies among the distance measuring devices, so that adjustment for each device is required to increase the accuracy of correction.
[0007]
Therefore, the present invention switches the ratio / light quantity based on the ratio data and the light quantity data, provides a limiter for distance measurement of the light quantity data, defines a range for correction at high luminance, and depends on the distance measurement object and the external environment. It is an object of the present invention to provide a distance measuring device that can obtain a highly accurate distance measuring output.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention receives a reflected light of the pulsed light beam from the distance measuring object, a light projecting means for repeatedly projecting the pulsed light beam toward the distance measuring object, Light receiving means for outputting a photoelectric conversion signal corresponding to the distance to the distance measuring object, and calculating the distance to the distance measuring object based on the photoelectric conversion signal, and performing the calculation during the repetitive operation of the pulsed light beam By accumulating the results, ratio data based on the incident position of the reflected light of the pulsed light beam from the distance measuring object on the light receiving element in the light receiving means and the pulsed light beam from the distance measuring object are accumulated. When the arithmetic circuit that outputs the two distance data of the light amount data based on the light amount of the reflected light and at least one of the ratio data and the light amount data is data farther than the first predetermined distance, The above light intensity data A selection circuit that selects the second predetermined distance when the light quantity data selected by the selection circuit is data closer to a second predetermined distance closer to the first predetermined distance. Provided is a distance measuring device that uses distance as final distance data.
[0009]
Further, light projecting means for repeatedly projecting a pulsed light beam toward the object to be measured, and the reflected light of the pulsed light beam from the distance measuring object are received, and according to the distance to the distance measuring object. A light receiving means for outputting a photoelectric conversion signal, and calculating a distance to the object to be measured based on the photoelectric conversion signal, and accumulating the calculation results during the repetitive operation of the pulsed light beam, The ratio data based on the incident position on the light receiving element in the light receiving means of the reflected light of the pulsed light beam from the object and the light amount data based on the light amount of the reflected light of the pulsed light beam from the distance measuring object. An arithmetic circuit that outputs two distance data; a selection circuit that selects the ratio data as the distance data when both the ratio data and the light amount data are closer than the first predetermined distance; Dedicated or other A photometric means for measuring the luminance of the distance measuring object that is also used as a function, and the photometric data output from the photometric means is data brighter than a predetermined luminance, and is selected by the selection circuit. When the selected ratio data is data within a predetermined distance range, a distance measuring device is provided that uses a correction distance closer than the first predetermined distance range as final distance data.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a circuit configuration of a distance measuring device as a first embodiment according to the present invention.
[0011]
The distance measuring device projects a light projecting element 1 that projects a light pulse serving as a light projecting unit, and a distance measuring object (not shown) from the light projecting element 1 via a light projecting lens 2, and the distance measuring object. And a light receiving element 4 for receiving the reflected light of the light pulse from the light receiving lens 3. The distance measuring device includes a distance measuring circuit 5 for detecting and calculating a photocurrent received by the light receiving element 4, a CPU 6 for sending a control signal to each circuit portion shown in the figure, and a distance measuring object. It comprises a photometric circuit 7 that measures luminance and performs A / D conversion.
[0012]
The distance measuring circuit 5 includes a constant voltage circuit 8 that supplies a constant voltage for driving the distance detecting circuit 5, a photocurrent detection detection 9 a that removes background light from the photocurrent output from the light receiving element 4, and performs photocurrent detection. 9b, a distance calculation circuit 10 for obtaining object distance information from the detected photocurrent, a count unit 11a for integrating the outputs of the distance calculation circuit 10 and A / D converting, and an output of the photocurrent itself. And a counting unit 11b for A / D conversion.
[0013]
Next, details of the distance measuring circuit 5 will be described.
Photocurrent detection circuits 9a and 9b for removing photocurrent due to background light are composed of operational amplifiers OP1 and OP2, transistors Tr1 and Tr2, capacitors C1 and C2, and switches SW1 and SW2.
[0014]
The switches SW1 and SW2 are controlled to be switched by an on / off signal from a terminal T3 of the CPU 6. That is, when no light is projected, an on signal is output from the CPU 6 to the terminal T3, and the switches SW1 and SW2 are turned on. As a result, the operational amplifiers OP1 and OP2 are in an active state, and negative feedback is performed by the operational amplifiers OP1 and OP2 so that all the photocurrent caused by the background light flows to the transistors Tr1 and Tr2.
[0015]
At this time, charges corresponding to background light are stored in the capacitors C1 and C2. Immediately before the projection, an off signal is output from the terminal T3 of the CPU 6, and the switches SW1 and SW2 are turned off. As a result, the operational amplifiers OP1 and OP2 are brought into a non-active state, and the amount of current discharged from the transistors Tr1 and Tr2 is determined by the charges held in the capacitors C1 and C2.
[0016]
The light projecting unit includes a light projecting element 1 and a transistor Tr11 that controls the light projecting element 1 to be turned on / off. The base of the transistor Tr11 is connected to the terminal T1 of the CPU 6 through a resistor. By outputting the pulse waveform signal shown in FIG. 2 from the CPU 6, the transistor Tr 11 is controlled to be turned on and off, and light is projected from the light projecting element 1 through the light projecting lens 2 to the distance measuring object.
[0017]
Reflected light from the object to be measured is incident on the light receiving element 4 through the light receiving lens 3, and is output from the light receiving element 4 to the distance measuring circuit 5 as a photocurrent.
The photocurrent is input to photocurrent detection circuits 9a and 9b configured by a background removal unit and a photocurrent detection unit in the distance measuring circuit 5. At this time, the light receiving element 4 as well as the signal photocurrent I _N, the photocurrent I _N + I _S1 containing the background light current I _S1 is output. That is, at the time of light projection, when photocurrents I _N + I _S1 and I _F + I _S2 are input from the light receiving element 4, the background photocurrents I _S1 and I _S2 are discharged from the transistors Tr1 and Tr2, respectively, and the object to be measured Only the signal photocurrents I _N and I _F reflected from are detected. The signal photocurrents I _N and I _F are input to the collectors of the transistors Tr3 and Tr6, respectively.
[0018]
These transistors Tr3, Tr4, Tr5 and Tr6, Tr7, Tr8 are each constitute a current mirror circuit, each of the collector current is equal to the signal light current I _N and I _F. In the transistor Tr5, the collector current flows to the diode D1, thereby converting the signal photocurrent into a compressed voltage.
[0019]
The same applies to the second photocurrent I _r obtained from the other anode of the light receiving element 4. That is, the background light current I _S2 and discharged from the transistor Tr2, the current mirror circuit formed of only the signal light current I _F transistors Tr6, Tr7, Tr8, and converts the compressed voltage flowing to the diode D2. The compressed voltage obtained in this way is supplied to the bases of the transistors Tr9 and Tr10 of the distance calculation circuit 10 via a buffer.
[0020]
The transistors Tr9 and Tr10 constitute a logarithmic expansion circuit together with the constant current source I ₀ , the integrating capacitor C3, and the switch SW3 controlled by the terminal T4 of the CPU 6.
[0021]
When light is not projected, the switch SW5 controlled by the terminal T7 of the CPU 6 is turned on to set the potential of the integrating capacitor C3 to the reference potential, and the switch SW5 is turned off by the terminal T7 immediately before the light is projected. At the time of light projection, the switch SW3 is turned on by the terminal T4 of the CPU, and the voltage input to the bases of the transistors Tr9 and Tr10 is calculated for each light projection, and the integration capacitor C3 is charged by this current.
[0022]
Similarly, when no light is projected, the switch SW7 controlled by the terminal T8 of the CPU 6 is turned on to set the potential of the integrating capacitor C4 to the reference potential, and the switch SW7 is turned off by the terminal T8 immediately before the light is projected. During projection, is inputted to the distance measuring circuit 5 for each projection, the current I _N + I _F by integration capacitor C4 appearing at the collector of the transistor Tr4, Tr7 is charged.
[0023]
When a predetermined number of light projections are completed, the terminal T5 is switched from “H (high level)” to “L (low level)”, the switch SW4 is turned on, and the capacitor C3 is discharged. At the same time, a counter built in the CPU 6 operates and continues counting until the output of the operational amplifier OP3 monitored at the terminal T9 of the CPU 6 becomes “L” (ratio integration). The output of the operational amplifier OP3 changes from “H” to “L” when the terminal voltage of the capacitor C3 becomes higher than the reference voltage Vref. When the counting of the capacitor C3 is completed, the terminal T6 of the CPU 6 is changed from "H" to "L" and the switch SW6 is turned on to discharge the capacitor C4.
[0024]
At the same time, a counter built in the CPU 6 works and continues counting until the output of the operational amplifier OP4 monitored at the terminal T10 of the CPU 6 becomes “L” (light quantity integration).
[0025]
In this way, an output corresponding to the position of the distance measurement target can be obtained as the count value of the counter in the CPU 6.
Next, the operation of the first embodiment will be described with reference to the flowchart shown in FIG.
[0026]
First, photometry is performed prior to distance measurement, and the luminance BVM of the object to be measured is measured. Then, light is projected by the light projecting element 1, and ratio integration and light amount integration are performed while A / D conversion is performed, and two distance measurement data, that is, ratio data and light amount data are obtained as count values. Subsequently, the count values of the ratio data and the light amount data are converted to 1 / L data, 1 / L _H , 1 / It converted to L _P (step S1 to S4).
[0027]
Here, the count value, which is distance measurement data, is converted to 1 / (distance) instead of distance because the focus position of the photographic lens and 1 / (distance) are almost proportional, and the output of triangulation is also a principle. This is because the calculation is simpler if 1 / (distance) is treated as distance data because it is proportional to 1 / (distance) rather than distance.
[0028]
When the 1 / L data is obtained, first, it is determined whether the ratio data 1 / L _H or the light amount data 1 / L _P is used as the distance data 1 / L, and at least one of the ratio data and the light amount data is determined. When the distance is longer than the predetermined distance (8.7 m), the light quantity data 1 / L _P is used, and in other cases, the ratio data 1 / L _H is used as the distance data 1 / L (steps S5 and S6).
[0029]
When the light quantity data 1 / L _P is selected as the distance data 1 / L, it is determined whether or not the light quantity data 1 / L _P is closer than a predetermined distance (6.5 m). = a 1 / 6.5m, and otherwise the distance data 1 / L = light quantity data 1 / L _P (step S9 to S11).
[0030]
When the data 1 / L _H as the distance data 1 / L is selected, then, photometric data BVM on the basis of a judgment of the luminance of the range-finding object, photometric data BVM predetermined luminance (BV6) When it is darker, distance data 1 / L = ratio data 1 / L _H is set, otherwise, high brightness correction is performed to determine distance data 1 / L (steps S7 and S8).
[0031]
In the high luminance correction, first, it is determined whether or not the ratio data 1 / L _H is closer than a predetermined distance (4.4 m). and L _H, in the case far responsible for determining whether the data in the ratio data 1 / L _H first predetermined distance range (4.4~5m), the first predetermined distance as long as it is within the range The correction distance (4.4 m) of the range is the distance data 1 / L, and if it is out of the range, whether the ratio data 1 / L _H is data within the second predetermined distance range (5-5.8 m) If it is within the range, the correction distance (4.8 m) of the second predetermined distance range is set as the distance data 1 / L.
[0032]
When the ratio data 1 / L _H is data at a far distance, the farthest correction distance (5.8 m) is set as the distance data 1 / L (steps S12 to S17).
By determining the distance to the final distance measurement object through the operations and judgments as described above, the long-distance distance measurement performance and the light amount distance measurement accuracy are improved, and the accuracy of the distance measurement object is high even when the brightness of the distance measurement object is high. Good ranging output can be obtained.
[0033]
In the first embodiment, the photometry is performed immediately before the projection of the distance measurement, but it is not always necessary to perform the photometry at this timing, and it is only necessary that the photometry data is obtained before performing the processing in step S5 and subsequent steps. In addition, a photometric sensor or photometric circuit for performing photometry may be used only for distance measurement or may be used for exposure of a camera as long as it can measure the luminance of a distance measurement object.
[0034]
Further, in the first embodiment, at high luminance, rounding is performed to three predetermined distances according to the value of the ratio data 1 / L _H. However, this need not necessarily be three predetermined distances. It goes without saying that the number of combinations of the predetermined distance range and the predetermined distance for rounding data within the range can be increased or decreased according to the conditions under which the distance measuring device of the invention is used.
[0035]
Next, a distance measuring apparatus according to the second embodiment will be described with reference to a flowchart shown in FIG. In the second embodiment, the ratio data 1 / L _H and the light amount data 1 / L _P are also switched on the long distance side of the high luminance correction region of the first embodiment. Here, steps S1 to S11 are the same as those in the first embodiment described above, and thus detailed description thereof is omitted.
[0036]
First, in step S7, when the luminance of the distance measuring object is brighter than the predetermined luminance (BV6), high luminance correction is performed.
In this high luminance correction, in steps S12 to S14, S19, and S20, as in the first embodiment, it is determined whether or not the ratio data 1 / L _H is closer than a predetermined distance (4.4 m). data in the correction is a distance data 1 / L = ratio data 1 / L _H without, if far ratio data 1 / L _H first predetermined distance range (4.4~5m) if It is determined whether or not there is. If this determination is within the range, the correction distance (4.4 m) of the first predetermined distance range is the distance data 1 / L, and if it is out of the range, the ratio data 1 / L _H is the second predetermined distance. It is determined whether or not the data is within the range (5 to 5.8 m). If the data is within the range, the correction distance (4.8 m) of the second predetermined distance range is set as the distance data 1 / L.
[0037]
When the ratio data 1 / L _H is further than the second predetermined distance range, the ratio data 1 / L _H and the light quantity data 1 / L _P are switched to obtain the light quantity data 1 / L _P. When the distance is shorter than the predetermined distance (5 m), the predetermined distance (5 m) is set as distance data 1 / L. When the distance is far, distance data 1 / L = light quantity data 1 / L _P (steps S15 to S18).
[0038]
As described above, light intensity data that is not affected by the brightness of the object to be measured in principle is used at a long distance at high brightness, and the reflectance of the object to be measured is high. In such a case, a limiter that provides data for a predetermined distance is provided, so that a highly accurate distance measurement output can be obtained even when a distance measurement object is present at a long distance under high brightness.
[0039]
【The invention's effect】
As described in detail above, according to the present invention, switching between the ratio data and the light quantity data is performed by the ratio data and the light quantity data, and the light quantity data is the object of distance measurement. A limiter is provided to round the data when it is extremely close to the actual distance, and correction for rounding the data in a predetermined distance range to a predetermined distance is performed for distance measurement under high brightness. It is possible to provide a distance measuring device that can obtain a distance measuring output with high accuracy regardless of a distance measuring object or an external environment.
[Brief description of the drawings]
FIG. 1 is a diagram showing a circuit configuration of a distance measuring device as a first embodiment according to the present invention.
FIG. 2 is a flowchart for explaining the operation of the distance measuring apparatus according to the first embodiment;
FIG. 3 is a flowchart for explaining an operation of a distance measuring apparatus according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Projection element, 2 ... Projection lens, 3 ... Light reception lens, 4 ... 5 ... Distance measuring circuit, 6 ... CPU, 7 ... Photometry circuit, 8 ... Constant voltage circuit, 9a, 9b ... Photocurrent detection detection, 10: Distance calculation circuit, 11a, 11b: Count unit.

Claims (4)

A light projecting means for repeatedly projecting a pulsed light beam toward the object to be measured;
A light receiving means for receiving reflected light of the pulsed luminous flux from the distance measuring object and outputting a photoelectric conversion signal corresponding to the distance to the distance measuring object;
Based on the photoelectric conversion signal, the distance to the distance measuring object is calculated, and during the repetitive operation of the pulsed light beam, the calculation result is accumulated to reflect the pulsed light beam reflected from the distance measuring object. An arithmetic circuit that outputs two distance data of ratio data based on an incident position on a light receiving element in the light receiving means and light amount data based on the amount of reflected light of the pulsed light beam from the object to be measured;
A selection circuit that selects the light amount data as the distance data when at least one of the ratio data and the light amount data is data farther than a first predetermined distance;
Comprising
When the light quantity data selected by the selection circuit is data closer to the second predetermined distance than the first predetermined distance, the second predetermined distance is used as final distance data. Ranging device characterized by. A light projecting means for repeatedly projecting a pulsed light beam toward the object to be measured;
A light receiving means for receiving reflected light of the pulsed luminous flux from the distance measuring object and outputting a photoelectric conversion signal corresponding to the distance to the distance measuring object;
Based on the photoelectric conversion signal, the distance to the distance measuring object is calculated, and during the repetitive operation of the pulsed light beam, the calculation result is accumulated to reflect the pulsed light beam reflected from the distance measuring object. An arithmetic circuit that outputs two distance data of ratio data based on an incident position on a light receiving element in the light receiving means and light amount data based on the amount of reflected light of the pulsed light beam from the object to be measured;
A selection circuit that selects the ratio data as the distance data when both the ratio data and the light amount data are data closer than a first predetermined distance;
A photometric means for measuring the brightness of the object for distance measurement, which is dedicated for distance measurement or combined with other functions;
Comprising
When the photometry data output from the photometry means is data brighter than a predetermined luminance, and the ratio data selected by the selection circuit is data within a predetermined distance range, the first data A distance measuring apparatus characterized in that a corrected distance closer than a predetermined distance is used as final distance data. A distant data than the farthest distance of the upper Kisho constant distance range the ratio data, and when the light quantity data is data closer than a predetermined distance set in advance ultimately the predetermined distance The distance measuring device according to claim 2, wherein the distance data is set to be accurate distance data. A distant data than the farthest distance of the upper Kisho constant distance range the ratio data, and when the light quantity data is distant data than a predetermined distance set in advance ultimately the light quantity data The distance measuring device according to claim 2, wherein the distance data is set to be accurate distance data.

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