JP2012098094A - Triangulation type distance detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a triangulation type distance detecting circuit that enables, when distances in a broad range, from long to short, are to be measured by triangulation, the accuracy of distance measurement to be enhanced by decreasing susceptibility to fluctuations in characteristics while securing a dynamic range for improving the S/N ratio in a simple configuration using no particularly precise components.SOLUTION: A circuit comprises an optical position sensor that outputs an N-side signal and an F-side signal corresponding to the incident position of a spot beam (one-dimensional PSD 11), a first amplifier that amplifies either the N-side signal or the F-side signal (amplifier 12), a second amplifier that differentially amplifies the N-side signal and the F-side signal (differential amplifier 20), and a distance calculator that calculates a distance on the basis of the outputs of the first amplifier and the second amplifier (CPU 21).

Description

  The present invention relates to a so-called triangulation distance detection circuit used for an automatic door sensor and the like, and more particularly, to a distance detection circuit for improving distance measurement accuracy.

  In the automatic door sensor based on the distance measurement, a very wide range of distance measurement (closest to 3 m from the sensor) is required, and accuracy of about several centimeters is required for the distance detection accuracy. In addition, a very fast response speed (100 ms or less) is required.

  As a conventional technique suitable for such an automatic door sensor, a technique for detecting a distance by a so-called triangulation method using an optical position sensor such as a PSD, for example, a “distance measuring sensor” described in Patent Document 1 And a “ranging device” described in Patent Document 2 is known. Specifically, for example, there has been the following technique.

(A) Providing signal amplification circuits on each of the short-distance side and the long-distance side FIG. 5 shows distances in which individual amplification circuits are provided for the short-distance side signal (N-side signal) and the long-distance side signal (F-side signal) 2 is a schematic configuration diagram of a main part of a detection circuit 100. FIG.

  As shown in FIG. 5, the distance detection circuit 100 has a light receiving surface (not shown) on which the spot light is incident, and an N-side signal and an F-side signal corresponding to the spot light incident position from both sides of the light receiving surface. Are respectively output, an amplifier 12 that amplifies the N-side signal (hereinafter referred to as “amplifier 12N” when distinction is necessary), and an amplifier 13 that further amplifies the output of this amplifier 12N (hereinafter referred to as “amplifier 12N”). When it is necessary to distinguish, it is referred to as “amplifier 13N”), an amplifier 12 that amplifies the F-side signal (hereinafter referred to as “amplifier 12F” when distinction is necessary), and the output of this amplifier 12F is further amplified. And an amplifier 13 (hereinafter referred to as “amplifier 13F” when distinction is necessary).

  Each output of the amplifier 13N and the amplifier 13F is connected to an A / D input terminal of a CPU (not shown), for example. The CPU can capture the signals input to these A / D input terminals by A / D conversion, and can calculate the distance by performing an operation based on the captured digital values.

(B) Providing a Signal Processing Circuit Using a Logarithmic Amplifier FIG. 6 is a schematic configuration diagram of a main part of a distance detection circuit 200 provided with a signal processing circuit using a logarithmic amplifier (log amplifier).

  As shown in FIG. 6, the distance detection circuit 200 includes a one-dimensional PSD 11 similar to the distance detection circuit, a logarithmic differential amplifier 14 that logarithmically amplifies the N-side signal and the F-side signal, and the N-side signal and F A logarithmic amplifier 15 for logarithmically amplifying the sum signal of the side signals, and a signal processing circuit 16 for processing each output signal from the logarithmic differential amplifier 14 and the logarithmic amplifier 15 are provided.

JP 2005-140773 A JP 58-144707 A

  In the distance measurement using the distance measuring device by the triangulation as described above, the measurement distance is calculated based on the balance between the N side signal and the F side signal. Since it tends to decrease, the measurement distance is difficult to stabilize. In order to stabilize the measurement distance, it is necessary to ensure the S / N ratio.

  On the other hand, when the amount of received light is large and the center of gravity is on the F side, the signal is likely to be saturated because the F side signal is larger than the N side signal. If the signal is saturated, an accurate measurement distance cannot be obtained. Therefore, it is necessary to avoid saturation by adjusting the amplifier gain or the like. However, when the amplifier gain is reduced, the amount of received light is reduced, which leads to a phenomenon that it is difficult to ensure distance accuracy.

  In the configuration as in (A) described above, it is desirable that the signal amplification circuit characteristics of the N-side signal and the F-side signal are the same, and saturation can be avoided by adjusting the amplifier gain. It is difficult to make the characteristics of the amplifier circuits the same, and depending on the gain adjustment state, the linearity of the distance measuring device cannot be maintained, or the distance accuracy may vary depending on temperature characteristics and the like. If the signal amplifying circuits on both sides are configured with high-precision parts, accurate distance measurement is possible, but it becomes extremely expensive.

  In addition, it is desirable to simultaneously capture the signal (A / D) to the CPU so as not to break the balance of the N-side signal and the F-side signal. However, it is difficult to capture the signal simultaneously with a general-purpose CPU.

  If signals cannot be captured simultaneously, the following solutions can be considered.

  (A1) A sample hold circuit or the like is added separately, and the N-side signal and the F-side signal are held and sequentially taken.

  (A2) By performing the light projection operation twice, separate processing is performed on the N-side signal and the F-side signal, for example, “N-side signal is processed for the first time / F-side signal is processed for the second time”.

  However, in the case of (A1), it is necessary to add the cost of the sample and hold circuit and the control signal for sample and hold.

In the case of (A2), no cost or control signal is added, and it is possible to eliminate the difference in circuit characteristics by using the same circuit for the processing circuit on the N side / F side. However, a deviation occurs in the signal acquisition timing of the N-side signal and the F-side signal due to the two light projections. The influence of the time shift on the measurement distance is large, and in some cases, the measurement result may be completely different from the actual measurement, and it is difficult to ensure the distance accuracy. (For example, when a situation that changes every moment occurs due to movement of an object or the like, if the position of the detection target is different between N-side signal acquisition and F-side signal acquisition, accurate distance measurement cannot be performed.)
In addition, since it takes two cycles to perform one-distance measurement, it takes twice as long to determine detection, resulting in poor response performance.

  On the other hand, the configuration as described above (B) has advantages such as being able to secure a very wide dynamic range, processing data converted into the center of gravity by hardware, and shortening the calculation time.

  However, there are problems such as variations in parts and circuits and the influence of environmental temperature, so that it is difficult to ensure the stability and accuracy of the measurement distance and it is not suitable for actual use.

  In view of such problems of the prior art, the object of the present invention is to use a simple configuration without using high-precision parts, particularly when measuring a wide range from a long distance to a short distance by triangulation. It is an object of the present invention to provide a triangulation distance detection circuit that can improve the distance measurement accuracy while ensuring a dynamic range for increasing the S / N ratio and being hardly affected by characteristic variations.

  In order to achieve the above object, the distance measuring circuit of the triangulation system of the present invention includes an optical position sensor that outputs a first signal and a second signal corresponding to an incident position of a spot light, and the first signal or the A first amplifier that amplifies one of the second signals, a second amplifier that differentially amplifies the first signal and the second signal, and a distance based on outputs of the first amplifier and the second amplifier And a distance calculation unit for calculating.

  In the distance measuring circuit of the triangulation system according to the present invention, the optical position sensor has a light receiving surface on which the spot light is incident, and in the triangulation according to the incident position of the spot light from both sides of the light receiving surface. The first signal corresponding to the short distance side and the second signal corresponding to the long distance side are respectively output, and the first amplifier has an input terminal to which the signal to be amplified is input. Amplifying either the first signal or the second signal that is input, and the second amplifier has an inverting input terminal and a non-inverting input terminal to which signals to be differentially amplified are respectively input. The first signal input to one of the first and the second signal input to the other may be differentially amplified.

  Here, the first signal may be input to the input terminal of the first amplifier. Alternatively, the second signal may be input to the input terminal of the first amplifier. Examples of the optical position sensor include, but are not limited to, a one-dimensional PSD.

  According to the distance detection circuit of the triangulation system having such a configuration, the influence of characteristic variation is ensured while ensuring a dynamic range for increasing the S / N ratio with a simple configuration without using particularly high-precision components. Therefore, the distance measurement accuracy can be improved.

  According to the distance detection circuit of the triangulation system of the present invention, the dynamic range for increasing the S / N ratio can be secured with a simple configuration without using particularly high-precision parts, and also affected by characteristic variations. Since it can be made difficult, the distance measurement accuracy can be improved.

1 is an overview configuration diagram of a distance detection circuit 10 according to a first embodiment of the present invention. In the distance detection circuit of the triangulation system, the distance to the object to be measured, the N side signal (short distance side) output from the PSD according to the spot light incident position, the F side signal (far distance side), and these It is a graph which shows the relationship with a differential signal. It is a graph which compares what comprised (A) mentioned above as a prior art with a high precision component, and the distance detection circuit 10 of 1st Embodiment by the gravity center position calculated | required by each. FIG. 7 is an overview configuration diagram of a distance detection circuit 10A according to a modification of the first embodiment of the present invention. It is a schematic block diagram of the principal part of the distance detection circuit 100 which provided the separate amplifier circuit for each of the short distance side signal (N side signal) and the long distance side signal (F side signal). It is a schematic block diagram of the principal part of the distance detection circuit 200 provided with the signal processing circuit using a logarithmic amplifier (log amplifier).

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
FIG. 1 is an overview configuration diagram of a distance detection circuit 10 according to the first embodiment of the present invention.

As shown in FIG. 1, the distance detection circuit 10
It has a light receiving surface (not shown) on which the spot light is incident, and an N side signal SN (short distance side) and an F side signal SF (far distance side) corresponding to the spot light incident position from both sides of the light receiving surface, respectively. One-dimensional PSD 11 to be output;
An amplifier 12 having an input terminal to which a signal to be amplified is input and an N-side signal SN is input to the input terminal (hereinafter referred to as “amplifier 12N” when distinction is necessary);
An amplifier 13 for further amplifying the output of the amplifier 12N (hereinafter referred to as “amplifier 13N” when distinction is necessary);
There are an inverting input terminal and a non-inverting input terminal to which signals to be differentially amplified are input, respectively, and an N-side signal SN is input to one of these (inverted input terminal in FIG. 1) and the other (non-inverted in FIG. 1). A differential amplifier 20 in which an F-side signal SF is input to an inverting input terminal);
An amplifier 13 for further amplifying the output of the differential amplifier 20 (hereinafter referred to as “amplifier 13D” when distinction is necessary);
It has at least two A / D input terminals, and A / D converts each signal from the amplifier 13N and the amplifier 13D respectively input thereto, and calculates a distance based on the A / D conversion values. CPU21 which performs a calculation is provided.

  Here, the amplifier gains of the amplifier 12N and the differential amplifier 20 may be equal. The amplifier gains of the amplifier 13N and the amplifier 13D may be the same, and may be determined so that necessary accuracy can be sufficiently obtained by the A / D conversion by the CPU 21. The amplifier 13N and the amplifier 13D are not indispensable because they can be omitted if the output signal levels from the amplifier 12N and the differential amplifier 20 are sufficiently high.

  FIG. 2 shows a distance detection circuit of a triangulation distance measurement system, an N-side signal (short-distance side) and an F-side signal (far-distance side) output from the PSD according to the spot light incident position. And the relationship between these differential signals. In this graph, each signal is a 10-bit A / D conversion value (0 to 1,023).

  As an automatic door sensor, it is desirable that the measurement can be performed with the highest possible accuracy particularly within a distance range of about 1.5 to 3.0 m. Within that distance range, as shown in the graph of FIG. 2, the signal was easily saturated because the F-side signal was larger than the N-side signal. If the amplifier gain is lowered, saturation can be avoided, but if the signal level is lowered thereby, it becomes difficult to ensure distance accuracy. However, such a problem does not occur in the differential signal because the signal does not saturate within the above distance range.

  FIG. 3 is a graph comparing the above-described conventional technology (A) configured with high-precision parts with the distance detection circuit 10 of the first embodiment at the position of the center of gravity obtained by each.

  As shown in the graph of FIG. 3, for example, a distance of 1.5 to 3.0 m, which is particularly important as an automatic door sensor, although the measurement error of the distance detection circuit 10 increases in the range of 0.5 to 1.0 m. Within the range, both are almost the same, and it can be seen that sufficient measurement accuracy is obtained even by the distance detection circuit 10.

  According to the configuration of the first embodiment as described above, the differential amplifier 20 for the N-side signal SN and the F-side signal SF eliminates the need to use the F-side signal SF that increases at the time of long-distance measurement in the subsequent stage. The amplifier gain can be increased to the extent that the N side does not saturate, and the S / N ratio can be improved, ensuring the necessary S / N ratio while avoiding saturation without switching the amplifier gain. It becomes easy to do.

  In addition, since information necessary for the subsequent processing (N-side signal SN-F-side signal SF) can be obtained by hardware, fluctuation factors such as characteristics of the amplifier circuit and component variations can be reduced.

  Regarding the signal capture to the CPU 21, the output of the differential amplifier 20 becomes auxiliary information necessary for obtaining the total amount of received light, and also includes information necessary for the subsequent stage (difference information on the N side and the F side). Therefore, even if compared with the above method (A) in which the N-side and F-side received light signals are used in direct calculation, the influence on the measurement distance due to the acquisition error is small. Therefore, it is possible to allow a slight time shift in signal capture.

  Therefore, if the A / D is performed twice with one projection (capture of the N-side signal SN and the differential-side signal), a response speed delay can be avoided while eliminating the need for an additional circuit. The problem like (A2) can be solved.

  In addition, if one distance information can be obtained by one light projection, a response speed delay can be avoided. However, when two received light signals are captured by a single light projection, the influence of the capture error on the measurement distance is inevitable. However, as described above, the differential signal capturing error has a relatively small influence on the distance. However, the influence on the center of gravity position is not small in all states, and the influence on the center of gravity position increases as the differential signal increases. In particular, the effect is greater when the spot position is closer to the short distance side, but due to the principle of triangulation, the resolution on the short distance side is rough, so there is little effect when the measurement distance is used. .

  Further, there is no need to add components by adopting the first embodiment, and it can be realized at substantially the same cost as the distance detection circuit 100 described above as the background art.

<Modification of First Embodiment>
FIG. 4 is an overview configuration diagram of a distance detection circuit 10A according to a modification of the first embodiment of the present invention. Since the second embodiment is the same as the first embodiment except for the points described below, the same constituent members will be denoted by the same reference numerals, and differences will be mainly described.

  As shown in FIG. 2, in the distance detection circuit 10A, the F-side signal SF is input to the input terminal of the amplifier 12 instead of the N-side signal SN. ").

  The configuration of the modified example of the first embodiment also has the same operational effects as the first embodiment.

<Other embodiments>
The present invention is not limited to a one-dimensional PSD, and can be applied to, for example, a two-dimensional PSD, a two photodiode, and other optical position sensors. Also, other distance measuring devices can be applied to avoid delays in response speed and to reduce the influence of circuit variations.

  It should be noted that the present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and should not be interpreted limitedly. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

10 distance detection circuit 10A distance detection circuit 11 one-dimensional PSD
12 amplifier 13 amplifier 14 logarithmic differential amplifier 15 logarithmic amplifier 16 signal processing circuit 20 differential amplifier 21 CPU
100 distance detection circuit 200 distance detection circuit

In the case of (A2), no cost or control signal is added, and it is possible to eliminate the difference in circuit characteristics by using the same circuit for the processing circuit on the N side / F side. However, a deviation occurs in the signal acquisition timing of the N-side signal and the F-side signal due to the two light projections. The influence of the time shift on the measurement distance is large, and in some cases, the measurement result may be completely different from the actual measurement, and it is difficult to ensure the distance accuracy. (For example, when a situation that changes every moment occurs due to movement of an object or the like, if the position of the detection target is different between when the N-side signal is acquired and when the F-side signal is acquired, accurate distance measurement cannot be performed) .
In addition, since it takes two cycles to perform one-distance measurement, it takes twice as long to determine detection, resulting in poor response performance.

In order to achieve the above object, the distance detection circuit of the triangulation system used for the human body or object detector in the automatic opening / closing apparatus of the present invention outputs the first signal and the second signal corresponding to the incident position of the spot light. An optical position sensor, a first amplifier that amplifies either the first signal or the second signal, a second amplifier that differentially amplifies the first signal and the second signal, and the first And a distance calculating unit that calculates a distance based on outputs of the amplifier and the second amplifier.

Here, the first signal may be input to the input terminal of the first amplifier. Alternatively, the second signal may be input to the input terminal of the first amplifier. Examples of the optical position sensor include, but are not limited to, a one-dimensional PSD. Examples of the detector include, but are not limited to, an automatic door sensor.

As shown in FIG. 1, the distance detection circuit 10 has a light receiving surface which spot light is incident (not shown), N-side signal SN (near corresponding from both sides of the light receiving surface in a spot light incidence position 1 dimensional and PSD11 the length side) and the F-side signal SF (far side) are output, having an input terminal to which a signal to be amplified is input, N side signal SN is inputted to the input terminal an amplifier 12 (hereinafter referred to as "amplifier 12N" when distinction is required), an amplifier 13 which further amplifies the output of this amplifier 12N (hereinafter referred to as "amplifier 13N" when distinction is necessary in) having an inverting input terminal and non-inverting input terminal signal differential amplifier are input, these one other with N-side signal SN to the (inverting input terminal in Fig. 1) is inputted (in FIG. 1 non F side signal to inverting input terminal) A differential amplifier 20 which F is input, an amplifier 13 for outputting a further amplification of this differential amplifier 20 (hereinafter referred to as "amplifier 13D" when distinction is necessary), even without least two systems A A CPU 21 having a / D input terminal and A / D converting each signal from the amplifier 13N and the amplifier 13D respectively input thereto, and calculating a distance based on the A / D conversion value; It has.

Claims (5)

A distance detection circuit using a triangulation method,
An optical position sensor that outputs a first signal and a second signal according to the incident position of the spot light;
A first amplifier for amplifying either the first signal or the second signal;
A second amplifier for differentially amplifying the first signal and the second signal;
A distance detection circuit comprising: a distance calculation unit that calculates a distance based on outputs of the first amplifier and the second amplifier. The distance detection circuit according to claim 1,
The optical position sensor has a light receiving surface on which spot light is incident, and the first signal and the long distance corresponding to the short distance side in the triangulation according to the incident position of the spot light from both sides of the light receiving surface Output the second signals corresponding to the sides,
The first amplifier has an input terminal to which a signal to be amplified is input, amplifies either the first signal or the second signal input to the input terminal,
The second amplifier has an inverting input terminal and a non-inverting input terminal to which signals to be differentially amplified are input, respectively, and the first signal input to one of them and the second signal input to the other A distance detection circuit characterized by differential amplification. The distance detection circuit according to claim 2,
The distance detection circuit, wherein the first signal is input to the input terminal of the first amplifier. The distance detection circuit according to claim 2,
The distance detection circuit, wherein the second signal is input to the input terminal of the first amplifier. In the distance detection circuit according to any one of claims 1 to 4,
The distance detection circuit, wherein the optical position sensor is a one-dimensional PSD or a two-photodiode.

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