JPH1163973A - Range finding module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized range finding module capable of confirming existenace of an object to be measured in the shortest range wherein distance detection is difficult. SOLUTION: This range finding module is provided with a PSD(position sensitive photodetector) 1 and light emitting elements 2, 3. Projection light from the light emitting element 2 is adjusted to be a spot light of small diameter by a light projection lens 5 arranged in front of the light emitting element 2, and cast on an object to be measured. On the other side, the projection light of the light emitting element 3 is cast, as a diffusion light of wide angle, on a region adjacent to the module. Reflected lights of the projection light from the object to be measured are made to enter the PSD 1 via a light receiving lens 4 and an interference filter 6. Concerning a distant object to be measured, distance is measured by trigometrical survey system using the light emitting element 2. Concerning an object to be measured within a short distance, exsistance of the object can be detected by a reflection light amount detecting system using the light emitting element 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light-based distance measuring module using a semiconductor position detector.

[0002]

2. Description of the Related Art A semiconductor position detector (Position Sensitive)
Photodetector (PSD) is a sensor that detects a light receiving position of incident spot light using a photodiode.
FIG. 6 shows its basic structure.

[0003] The PSD 401 is an n ⁺ type semiconductor substrate 4.
An n-type semiconductor layer 403 and a p-type semiconductor layer 402 are provided on the substrate 04, and electrodes 405 and 406 are provided on the p-type semiconductor layer 402 at a predetermined distance C. n-type semiconductor layer 4
03, a predetermined bias voltage is applied via an n ⁺ type semiconductor substrate 404. The light h is positioned at a predetermined distance x away from one electrode 406 on the light receiving surface of the p-type semiconductor layer 402.
When ν is incident, the light current generated is branched by the current from the electrodes 405 and 406 I _A, it is taken out as I _B.
The ratio of the extracted photocurrent is approximately the reciprocal of the distance between the light incident position and each of the electrodes 405 and 406. Further, the sum of the currents I _A, I _B is proportional to the amount of incident light hv. Therefore, the light incident position can be calculated from the ratio of each current.

[0004] The PSD is widely used in a distance measuring sensor that detects the distance to an object by light using the position detection characteristics. Fig. 7 shows the basic principle of such a distance measuring sensor.
This will be described with reference to FIG.

The light projected from the light emitting element 41a reaches the surface of the measured object 45 via the light projecting lens 43 and is reflected, and a part of the reflected light is transmitted through the light receiving lens 44 to the PS.
The light enters the light receiving position SP of the light receiving surface 42a of D42. At this time, the distance between the light receiving lens 44 and the light receiving surface 42a is f, and the distance between the light receiving lens 44 and the light projecting lens 43 along the optical axis (base line length).
It is B, and the distance from the optical axis center of the light receiving lens 44 of the light receiving position SP and x _1, the distance L between the object 45 surface light-receiving lens 44 is expressed by the following equation. L = Bf / x _1, as described above, the electrodes 42b of PSD42, the output I _A from 42c, than I _B, it is possible to determine the incident position SP of the light, the object to be measured 45 by this based on Can be obtained.

[0006] However, this type of apparatus has a limitation in performing short-distance measurements. As apparent from FIG. 7, the distance of the object to be measured 45 and PSD42 are close, that is, when L is short, x ₁ is increased, the L is a distance L _C or less, it reflected light region of the light receiving surface 42a So it cannot be detected. This L _C is represented by the following equation. L _C = Bf / (C−x ₀ ) where x ₀ is the optical axis center of the light receiving lens 44 and the PSD 4
2 is the distance from the light emitting element 41a side electrode 42c.

As a result, when the object to be measured is at a close distance, a current output cannot be obtained, so that an erroneous determination may be made that the object does not exist or exists at infinity.

As a technique for enabling a short distance measurement, there are techniques disclosed in Japanese Patent Application Laid-Open No. 62-235518 and Japanese Patent Publication No. 7-38048.

[0009] The former is, as shown in FIG.
_On the opposite side of the light emitting element of PSD1 that detects a normal area farther than _C , a PS that detects an adjacent area closer than L _C described above.
D2 are arranged side by side.

In the latter, as shown in FIG. 9, two types of light-emitting elements, a long-distance light-emitting element LED1 and a short-distance light-emitting element LED2, are arranged at different positions in the base line length direction, and each is selected. In this way, the near-distance measurement can be performed by correcting the output of the PSD according to each of them.

[0011]

However, in the former device, the PS installation space and cost are low.
Since the length of the light receiving area of D is limited, it is difficult to sufficiently measure the short distance side. In addition, there has been a problem that the output of the PSD is saturated due to the intensity of the reflected spot light from the object to be measured at a short distance being too strong, so that accurate distance measurement cannot be performed. If the output of the LED is reduced to overcome this, the distance measurement on the far side cannot be performed sufficiently.

Further, in any of the apparatuses, only the distance limit on the short distance side is reduced, and when the object to be measured is within a range from the closest distance within about 20 cm to the zero distance, the distance cannot be measured, and the distance cannot be measured. The existence of the measurement object itself could not be confirmed.

In view of the above problems, the present invention makes it possible to confirm the presence or absence of an object to be measured at a very short distance where distance detection is difficult.
It is an object to provide a small distance measuring module.

[0014]

A distance measuring module according to the present invention is a distance measuring module for projecting light onto an object to be measured and measuring a distance from the object to be measured. A first light-emitting element that irradiates a small-diameter spotlight toward the light source; (2) a second light-emitting element that irradiates light over a wide angle range in a proximity area; and (3) a light of the first light-emitting element. A light-emitting lens disposed on the road, and (4) a light-receiving surface disposed perpendicular to the optical axis of the first light-emitting element, which receives reflected light of the light emitted from each light-emitting element from the surface of the object to be measured. A semiconductor position detecting element that generates an electric signal according to the amount of light and outputs an electric signal corresponding to the incident position of the incident light on the light receiving surface; A light-receiving lens disposed between the objects, for condensing reflected light of the measured object on a light-receiving surface of the semiconductor position detecting element; 6) The light emitting operation of the first and second light emitting elements is switched and controlled, and at the time of light emission of the first light emitting element, based on an output electric signal corresponding to the incident position of the incident light on the light receiving surface of the semiconductor position detecting element. The distance to the measured object is calculated by the triangulation method,
When the light-emitting element emits light, an arithmetic circuit that detects the presence or absence of the object to be measured within a predetermined distance by a reflected light amount detection method based on an output electric signal corresponding to the amount of light received on the light-receiving surface of the semiconductor position detection element. It is characterized by having.

According to this, the light projected from the first light emitting element is applied to the object to be measured via the light projecting lens, and the reflected light is incident on the light receiving surface of the semiconductor position detecting element via the light receiving lens. Is done. Since the light projected from the first light emitting element is a small diameter spot light, the light incident on the semiconductor position detecting element is also a spot light. Therefore, the semiconductor position detecting element outputs an electric signal indicating the light receiving position. As described above, the reflected light enters the corresponding light receiving surface position of the semiconductor position detecting element according to the position of the measured object. Therefore, the reflected light receiving position of the light receiving surface of the semiconductor position detecting element is obtained from this electric signal, and based on this,
The distance to the measured object can be calculated by the triangulation method.

The object to be measured is irradiated with light at a wide angle from the second light emitting element. For this reason, when the measured object is at a short distance, a part of the reflected light from the measured object enters the semiconductor position detector via the light receiving lens. In this case, it is difficult to use an electric signal corresponding to the light receiving position because reflected light is incident on a wide range of the light receiving surface of the semiconductor position detector, but an electric signal corresponding to the amount of light incident on the light receiving surface is generated. . On the other hand, when the object to be measured does not exist, or when the object to be measured is at a long distance, there is no reflected light from the second light emitting element or the amount of reflected light reaching the semiconductor position detector is weak. Therefore, the electric signal corresponding to the amount of incident light is weak. Therefore, the presence or absence of the object to be measured in a close range can be determined based on the strength of the electric signal, that is, by detecting the amount of light reflected on the surface of the object to be measured.

Further, the arithmetic circuit may control the first and second light emitting elements to be alternately pulsed at predetermined intervals.

According to this, the arithmetic processing by the arithmetic circuit is easy.

Alternatively, there is further provided a monitor element for detecting the amount of light emitted from the light-emitting element corresponding to the vicinity of the first and / or second light-emitting element, and the arithmetic circuit is provided only when the output from the monitor element is higher than a predetermined value. The calculation of the distance to the measured object or the detection of the existence of the measured object may be performed.

According to this, when one or both of the first and second light emitting elements do not light or the light quantity is significantly deteriorated, the output from the corresponding monitor element decreases. In these cases, even if the measured object is present, the projected light on the measured object is not sufficient,
Although highly accurate measurement cannot be performed, according to the present invention, in such a case, erroneous measurement can be avoided by determining that the light emitting element is malfunctioning.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. To simplify the description, the same reference numerals have been used, where possible, to designate identical elements that are common to the figures. Note that the dimensions in the drawings do not always match the actual dimensions.

FIGS. 1A and 1B are schematic views of a first embodiment of the present invention. FIG. 1A is a front view, and FIGS.
FIG. 3 is a cross-sectional view taken along a line A and a line BB.

The apparatus according to the present embodiment includes a light receiving element 1 composed of a PSD capable of detecting a light receiving position, a first light emitting element 2 for projecting a spotlight on an object to be measured, and a diffused light for projecting an object to be measured. The second light emitting element 3 is provided. The light receiving element 1 and the first light emitting element 2 are accommodated in holders 7 and 8, respectively, and these holders 7 and 8 are fixed to the upper case 9A at a predetermined distance. Here, the first light emitting element 2
A light projecting lens 5 for narrowing the spot diameter of the projected light is fixed to a holder 8 on the front surface of the lens. On the other hand, an interference filter 6 for cutting disturbance light and a light receiving lens 4 for focusing reflected light from an object to be measured on the light receiving surface of the light receiving element 1 are arranged on the front surface of the light receiving element 1 and holders. 7 is fixed. At this time, it is necessary to make adjustment so that the optical axes of the light receiving lens 4 and the light projecting lens 5 become parallel, and the front surfaces of the light receiving element 1 and the first light emitting element 2 become perpendicular to these optical axes.

On the surface of the upper case 1 opposite to the lenses 4 and 5, an assembly board 10 on which electronic circuits electrically connected to the light receiving elements 1 and the light emitting elements 2 and 3 are mounted. I have. The assembly board 10 includes, for example, a signal processing IC.
11 for controlling the light receiving element 1 and the light emitting elements 2 and 3 and for calculating output signals. The lower case 9B is fixed to the upper case 9A by bonding or the like so as to sandwich the assembly board 10, thereby forming the case 9 and hermetically sealing internal components. Cable 1 penetrating this lower case 9B
According to 2, the output signal extracted from the electronic circuit of the assembly board 10 is transmitted to an external processing device (not shown) via the connector 13 attached to the other end of the cable 12.

Here, it is necessary that the first light emitting element 2 projects a small-diameter spot light on the object to be measured, and the second light emitting element 3 projects a diffused light having a wide angle (for example, ± 40 °). However, each element does not have to be a different kind, and an LED for irradiating diffused light is used in common, and the first light emitting element 2
In the case of using as the light source, the position and the focal length of the light projecting lens 5 may be adjusted, and the light emitted from the light projecting lens 5 may be adjusted to the spot light.

Next, the operation principle of this embodiment will be described with reference to FIG.

Each of the light emitting elements 2 and 3 has an L for projecting light.
EDs 2A and 3A and monitor light receiving elements 2B and 3B for monitoring the lighting state of the EDs 2A and 3A are provided. These LEDs
2A and 3A are controlled so that only one of them is turned on.

First, the measurement on the long distance side will be described.
The distance measurement on the far side is based on a triangulation method. That is,
As described above, the light emitted from the LED 2 </ b> A is condensed by the light projecting lens 5 into a small-diameter spot light, and is irradiated on the device under test 15. The diameter of the spot light is about 4 cm at a distance of 70 cm from the light projecting lens 5. DUT 15
Is generally irregularly reflected on the surface, and a part of the light passes through the condenser lens 4, passes through the interference filter 6,
The light reaches the light receiving surface 1A of the PSD of the light receiving element 1, generates a photocurrent, and outputs a current corresponding to the position from both electrodes 1B and 1C of the light receiving element 1. At this time, as described above,
Distance f of the light receiving lens 4 receiving surface 1A, the base length B, and the distance from the optical axis center of the light receiving lens 4 in the light receiving position is x _1, the distance L between the object 15 surface light receiving lens 4 is shown again It is represented by the following equation. L = Bf / x ₁ PSD indicates the incident position x ₁ on the light receiving surface as the output I _{A of} both electrodes,
Since it can be determined from the I _B, the measured object 15 based on it
The distance to can be obtained.

[0029] However, in this triangulation, when the measured object 15 'is present in close range, x ₁ is increased, so sticks out from the light-receiving surface 1A of the light receiving element 1, becomes impossible distance detection . the distance limit a position is the position of the object to be measured 15 'of the measurement, in a L _c. in this embodiment, the L _c is about 20 cm.

The relative short distance within the L _c is, LE
D3A and detection by a reflected light amount method using the light receiving element 1 are performed. Here, a case where the measured object 15 ″ is present at a close distance will be described as an example. The LED 3A emits light in a wide angle range (for example, ± 40 °). Is illuminated over a wide area. The reflected light of the projected light from the LED 3A from the measured object 15 ″ is incident on the light receiving lens 4 (in other words, the optical axis of the light receiving lens 4) as compared with the reflected light of the projected light from the LED 2A. Angle), a part of which is incident on the light receiving surface 1A of the light receiving element 1.
At this time, since the light in a relatively wide position of the light receiving surface 1A is incident, the electrodes 1B of the light receiving element 1, the current I _A generated from 1C, but becomes difficult to obtain the uniquely light receiving position from the I _B , the sum I _a + I _B becomes one corresponding to the sum of light amount of light incident on the light receiving surface. The closer the measured object 15 is, the greater the amount of light incident on the light receiving surface 1A if the reflection characteristics are the same, so that the sum of the output currents also increases.

On the other hand, since the LED 3A emits light at a wide angle, when the object to be measured is at a long distance, the amount of the reflected light that enters the light receiving surface 1A via the light receiving lens 4 out of the reflected light. Becomes weak, and the sum of the output currents becomes small. Further, when the object to be measured does not exist within the predetermined distance, the light of the LED 3A is diffused before reaching the object to be measured, so that the reflected light cannot be detected. In these cases, even if not generated, it becomes weak sum I _A + I _B of the output current. Therefore, the reflection characteristic of the measured object to be measured based on, as a threshold value of the current intensity below generated by reflected light when the object to be measured is in the distance L _c, the more current by setting to determine that an object when it detects the presence of the distance L object existence in close proximity within _c it can be determined reliably.

The LED 3A is arranged so that, even when the object to be measured is disposed immediately before the light receiving lens 4, the reflected light of the projection light from the LED 3A by the object to be measured enters the light receiving surface of the light receiving element 1. It is preferable to arrange the light receiving element 1 close to the light receiving element 1. This makes it possible to confirm the presence or absence of an object from the zero distance to a distance L _c of the foregoing, only the triangulation can overcome the problem of missing objects present in close range to occur when used. Further, unlike the conventional example, there is no need to add a PSD in the position detection direction, so that the size of the device itself can be reduced.

Further, since the light emitting elements 2 and 3 are provided with the monitor light receiving elements 2B and 3B, the corresponding LEDs 2A and 3A monitor the lighting state, and detect the distance or detect the presence or absence only when the corresponding LEDs 2A and 3A are lit. If you check, LED
A state in which no light is output from the light receiving element 1 due to turning off the lights of 2A and 3A is not erroneously determined as a state in which the object to be measured does not exist, and the stability of measurement is improved.

Next, a second embodiment will be described with reference to FIG. FIG. 3 is a schematic perspective view of the second embodiment. The basic configuration is the first shown in FIGS.
This is the same as the above embodiment, and the description of the overlapping parts will be omitted. In this embodiment, two LEDs 2A and 2C are arranged on the first light emitting element 2 with the monitor light receiving element 2B interposed therebetween in a direction orthogonal to the arrangement direction of the first light emitting element 2 and the light receiving element 1. . Further, the light receiving element 1 has a PS at a position substantially corresponding to the LEDs 2A and 2C.
D1D and 1E are arranged. With this arrangement, two-channel measurement is possible.

Here, when lenses having the same focal length f value are used for the light receiving lens 4 and the light projecting lens 6,
The distance between the LEDs 2A and 2C and the distance between the PSDs 1D and 1E need to be the same. When the f-number of each lens is different, the distance between the LEDs 2A and 2C is adjusted according to the f-number,
It is necessary to adjust the intervals between the PSDs 1D and 1E. As a result, the reflected light of the light projected from the LED 2A from the object to be measured enters the PSD 1D, and the reflected light of the light projected from the LED 2C from the object to be measured enters the PSD 1E.

The light receiving element 1, the light emitting elements 2 and 3 are connected to a signal processing IC 11 (see FIG. 1). Of these, two output electrodes are provided for each of the PSDs 1D and 1E, and both electrodes on the corresponding sides are connected in parallel. As a result, highly accurate and stable measurement can be performed as compared with the one-channel measurement of the first embodiment.

Next, the configuration and operation of the signal processing IC 11 will be described with reference to FIGS. FIG. 4 shows this IC 11
FIG. 5 is a diagram showing the operation timing of this device.

First, the timing generation circuit 21 generates drive pulse signals LED1 to 3 for controlling light emission of the three LEDs 2A, 2C and 3A by dividing the frequency of the pulse clock signal CLK supplied from the outside. In the present embodiment, as shown in FIG. 5, the pulse signals of the LEDs 1, 2, and 3 are switched and output every 16 CLK signal pulses. Further, the timing generation circuit 21 outputs a S / H_A signal for sample and hold control before the pulse of each LED signal rises, and similarly, the S / H_B for sample and hold control before the end of the pulse signal of each LED signal. Pulse output signal,
A VALID signal indicating the end of the sample hold is output a predetermined time after the end of each LED signal. In addition, LED
The pulse signal corresponding to 1 is output to the outside as a SYNC signal.

In response to the drive pulse signals LED1 to LED3, the drive circuit 22 causes the LEDs 2A, 2C and 3A to pulse light in a time-division manner. The light emitted from each LED is reflected by the device under test 15 and each PS
Light is incident on D1D and 1E to generate a photocurrent. The photocurrent generated by each PSD is divided and output from the two electrodes. Since the respective PSDs are connected in parallel, the combined current of the output currents of the corresponding electrodes is sent to the subsequent circuit. . These combined photocurrents are pulse currents containing noise due to disturbance light.

The noise-containing pulse current is converted into a voltage signal by current-voltage converters 23 and 24 after a noise component due to disturbance light (not shown) is removed by using DC feedback or capacitive coupling. And the addition circuit 2
5, and are transferred to the subtraction circuit 26, respectively.

The addition output signal and the subtraction output signal thus obtained are sent to the subsequent sample and hold circuits 27 to 30. Circuit 2 of each sample and hold circuit
7 and 29, the signal level immediately before LED emission based on the sample / hold control signal S / H_A sent from the LED timing circuit 21,
LED based on sample / hold control signal S / H_B
Each signal level at the time of light emission is held.

When the VALID signal is turned on, the signal level sampled and held in this manner is reduced to the next stage of the subtraction circuit 3.
1,32 to be sent, by the difference in signal level between the time of the LED and the LED light emission immediately before is taken, and the addition signal noise is eliminated outputted sigma _out (corresponding to I _A + I _B), the subtraction signal output delta _out (corresponding to I _a -I _B) is obtained. Distance detection can be performed based on this signal.

On the other hand, the outputs of the monitor elements 2B and 3B are
After being converted into a voltage signal by the current-voltage converter 33, the signal is sampled and held by the sample and hold circuit 34, and then output as a signal LED _mon of a constant value. The Vref signal is a reference signal when the LED is not lit. If the difference between the two is equal to or less than the predetermined level, it can be considered that the LED is not lit. Therefore, by generating an error output, malfunction can be prevented.

The output signal obtained as described above may be processed as it is, or may be converted into a digital signal and processed. Further, the output of each cycle may be directly processed or the arithmetic processing may be performed based on the outputs of a plurality of cycles.

[0045]

As described above, according to the present invention,
In a distance measuring module that detects the position of an object to be measured by a triangulation method using a semiconductor position detector, the presence or absence of an object within a close distance, which cannot be detected by the triangulation method, is detected by a reflected light amount detection method. Therefore, it is possible to prevent a malfunction in which it is determined that the object does not exist when the object is within a close distance. Further, since the same semiconductor position detector is used for the sensors of the triangulation method and the reflected light amount detection method, the size of the apparatus can be reduced.

Furthermore, by alternately pulsing the long-distance light emitting element and the short-distance light emitting element in a pulsed manner, complicated arithmetic processing becomes unnecessary and reliable measurement becomes possible.

Further, by further providing a monitor element for detecting the light emission amount of the light emitting element, when the light emitting element is not turned on, it is impossible to measure with the conventional apparatus, but the object is at infinity or the object. There was a risk of malfunction as a result of the detection of non-existence, but the present device can detect a malfunction of the light emitting element in such a case.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a measurement principle of the embodiment according to FIG. 1;

FIG. 3 is a schematic perspective view of a second embodiment of the present invention.

FIG. 4 is a block diagram of a signal processing IC according to the embodiment of FIG. 3;

FIG. 5 is an operation timing chart of the signal processing IC according to FIG. 4;

FIG. 6 is a diagram showing a basic configuration of a semiconductor position detector.

FIG. 7 is a diagram illustrating the operation principle of a distance measuring sensor using a semiconductor position detector.

FIG. 8 is a diagram illustrating an example of a distance measuring sensor using a conventional semiconductor position detector.

FIG. 9 is a diagram showing another example of a distance measuring sensor using a conventional semiconductor position detector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor position detector, 2, 3 ... Light emitting element, 4 ... Light receiving lens, 5 ... Projection lens, 6 ... Interference filter, 7, 8 ...
Holder, 9 case, 10 assembly board, 11 signal processing IC, 12 cable, 13 connector, 15 object to be measured.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiko Tomita 1126 Nomachi, Hamamatsu City, Shizuoka Prefecture 1 Hamamatsu Photonics Co., Ltd.

Claims (3)

[Claims] 1. A distance measuring module for projecting light onto an object to be measured and measuring a distance from the object to be measured, comprising: a first light emitting element for irradiating a small-diameter spotlight toward a surface of the object to be measured; A second light emitting element that irradiates light over a wide angle range of the proximity region; a light projecting lens arranged on an optical path of the first light emitting element; and a light emitting element perpendicular to an optical axis of the first light emitting element. Having a light receiving surface disposed thereon, receiving the reflected light of the irradiation light of each of the light emitting elements from the surface of the object to be measured, and generating an electric signal corresponding to the amount of light, on the light receiving surface of the incident light. A semiconductor position detecting element that outputs an electric signal in accordance with the incident position, and is disposed between the semiconductor position detecting element and the measured object;
A light receiving lens for condensing reflected light of the object to be measured on a light receiving surface of the semiconductor position detecting element, and switching control of light emitting operations of the first and second light emitting elements, and at the time of light emission of the first light emitting element Based on an output electric signal corresponding to an incident position of incident light on a light receiving surface of the semiconductor position detecting element, a distance to an object to be measured is calculated by a triangulation method, and when the second light emitting element emits light, An arithmetic circuit for detecting the presence or absence of an object to be measured within a predetermined distance by a reflected light amount detection method based on an output electric signal corresponding to a light amount received on a light receiving surface of the semiconductor position detecting element. 2. The distance measuring module according to claim 1, wherein the arithmetic circuit controls the first and second light emitting elements to be alternately pulsed at predetermined intervals. 3. A monitor element for detecting a light emission amount of a light emitting element corresponding to the vicinity of the first and / or second light emitting element, wherein the arithmetic circuit outputs an output from the monitor element of a predetermined value or more. The distance measuring module according to claim 1, wherein the distance calculation to the measured object or the presence or absence of the measured object is performed only in the case.