KR101219367B1 - Psd sensor and mehod of controlling psd sensor - Google Patents

Psd sensor and mehod of controlling psd sensor Download PDF

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KR101219367B1
KR101219367B1 KR1020100123931A KR20100123931A KR101219367B1 KR 101219367 B1 KR101219367 B1 KR 101219367B1 KR 1020100123931 A KR1020100123931 A KR 1020100123931A KR 20100123931 A KR20100123931 A KR 20100123931A KR 101219367 B1 KR101219367 B1 KR 101219367B1
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current
signal
light
laser light
light source
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KR20120062974A (en
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박기환
강성구
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광주과학기술원
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Abstract

In the conventional PSD sensor using the optical triangular method as shown in FIG. 1, when a weak light is incident on the PSD sensor as the color, state, and distance of the measurement surface of the target object become farther, the incident intensity changes. There was a problem that the sensor performance of the PSD is deteriorated, such as high nonlinearity and low resolution.
The present invention provides a method of feedback-controlling a PSD sensor so that the incident light amount (light amount signal) incident on the PSD can be kept constant, and a PSD sensor to which such a method is applied.

Description

PSD sensor and its control method {PSD SENSOR AND MEHOD OF CONTROLLING PSD SENSOR}

The present invention relates to a PSD sensor and a control method thereof, and more particularly, when a weak light is incident as the color and state of a measurement surface of a target object and a measurement distance are far from each other, the intensity of incident light changes and thus the non-linearity is increased. Method of controlling the PSD sensor to maintain the constant amount of incident light (light signal) incident on the PSD by solving the problem of the conventional PSD sensor, such as high performance and low resolution, such as sensor performance is deteriorated The present invention relates to a PSD sensor to which a control method is applied.

1 is a schematic diagram illustrating the basic principle of the optical triangulation method. As shown in Fig. 1, in the optical triangular method, when laser light projected on a target object is diffusely reflected on the surface of the target object, a part of the reflected light is condensed with a light receiving lens to form an image on the optical element. When the position of the target object is changed, the angle at which the diffused reflected light is focused is changed to move the image forming position on the optical device. The displacement amount of the target object is measured by detecting a digital value or an analog current value corresponding to this position.

 CCD devices and PSD (Position Sensitive Detector) devices are the most used optical devices for the position sensor using the optical triangular method. The CCD element is composed of a fine array of MOS diodes so that the amount of charge accumulated according to the amount of light for each pixel can be measured as a digital value. Even when the amount of light is weak, the output is output by the amount of charge accumulated for each pixel for the corresponding amount of light, so it is less sensitive to ambient noise and a signal processing is performed according to the distribution of received light through averaging. This does not fall significantly. However, there are disadvantages in that the complexity of the peripheral signal processing is high, the configuration cost is high, and the digital output resolution and measurement speed limit may be limited.

On the other hand, the PSD device is a kind of photodiode having a P-I-N junction on the silicon surface to detect the position of the incident light spot using the lateral photovoltaic effect. Unlike CCD devices, it provides an analog type current output according to the light receiving position, which has the advantage of high position resolution and fast response speed. However, when weak light enters the color, state, and distance of the measurement surface of the target object, the intensity of incident light changes, resulting in deterioration of sensor performance such as high nonlinearity and low resolution. there was.

The present invention was devised to overcome the disadvantage of the PSD device vulnerable to the change in the incident light amount, if the incident light amount is weak by using a voltage value corresponding to the intensity of the incident light amount (Laser diode: It is an object of the present invention to provide a control method that increases the current output of LD) and lowers the light output to a steady state when the amount of incident light is strong.

The present invention has been made to solve the above problems, the PSD sensor according to the first embodiment of the present invention, a laser light source for generating a laser light; A light receiving lens for collecting the laser light diffused and reflected from a surface of a target object; A PSD element for forming light collected by the light receiving lens; A first current voltage converter and a second current voltage converter configured to convert first and second currents output from both ends of the PSD element into first and second voltages, respectively; A calculator configured to calculate a light quantity signal and a distance signal based on the first voltage and the second voltage; And a controller configured to control the laser light source by using a result of comparing the reference light amount signal with the light amount signal.

The first current voltage converter and the second current voltage converter may further include an amplifier configured to amplify the first current and the second current while converting the first current and the second current into the first voltage and the second voltage, respectively.

In addition, the light quantity signal is preferably as shown in the following equation (1).

Figure 112010080370238-pat00001

I (intensity) is the light quantity signal, K 1 is the proportional constant of the first current voltage converter, K 2 is the proportional constant of the second current voltage converter, X 1 is the first current, X 2 is the second current.

In addition, the distance signal is represented by the following equation (2).

Figure 112010080370238-pat00002

D (distance) is a distance signal, K 1 is a proportional constant of the first current voltage converter, K 2 is a proportional constant of the second current voltage converter, X 1 is a first current, and X 2 is a second current.

The control unit preferably controls the light quantity signal to be constant.

The controller may be configured to input a value obtained by subtracting the light amount signal from the reference light amount signal to the laser light source.

The apparatus may further include a modulator for modulating the output of the controller and applying the modulated output to the laser light source.

Here, the modulator may use a pulse amplitude modulation (PAM) or amplitude modulation (AM) scheme.

On the other hand, the control method of the PSD sensor according to the second embodiment of the present invention, the laser light source for generating a laser light; A light receiving lens for collecting the laser light diffused and reflected from a surface of a target object; And a PSD element for forming light condensed by the light receiving lens. The method of controlling a PSD sensor comprising: converting a first current output from one end of the PSD element into a first voltage; ; A second current voltage conversion step of converting a second current coming from the other end of the PSD element into a second voltage; A calculation step of calculating a light quantity signal and a distance signal based on the first voltage and the second voltage; And a control step of controlling the laser light source by using a result of comparing the reference light quantity signal with the light quantity signal.

The first current voltage converting step and the second current voltage converting step may include a first amplifying step and a second amplifying step of amplifying the first current and the second current while converting the first current and the second current into the first voltage and the second voltage, respectively. It may be made to include more.

In addition, the light quantity signal is preferably the same as the equation (1).

In addition, the distance signal is as shown in Equation (2).

The control unit preferably controls the light quantity signal to be constant.

The controller may be configured to input a value obtained by subtracting the light amount signal from the reference light amount signal to the laser light source.

The apparatus may further include a modulator for modulating the output of the controller and applying the modulated output to the laser light source.

In addition, the modulation unit may use a pulse amplitude modulation (PAM) or amplitude modulation (AM) scheme.

According to the present invention, there is provided a method of controlling a PSD sensor to maintain a constant amount of incident light (light quantity signal) incident on a PSD, and a PSD sensor to which the same method is applied, thereby providing a color and a state of a measurement surface of a conventional object. In addition, when weak light is incident as the measurement distance increases, the problem of deterioration of the sensor performance of the PSD, such as a high nonlinearity and a low resolution due to an incident light intensity, is changed. In other words, in the PSD sensor using the optical triangulation method, it is possible to maintain displacement measurement performance regardless of the color and measurement distance of the surface of the target object.

1 is a schematic diagram showing a basic concept of position measurement using an optical triangulation method.
2 is a schematic diagram illustrating a concept of the PSD device 300 and the first and second current voltage converters 400 and 410.
3 is a system configuration diagram for controlling the light intensity of the laser light source based on the light amount signal I by the calculation unit of the PSD sensor.
4 is a view showing a voltage change of the PSD sensor according to the displacement of the measurement surface of the target object and the color change of the measurement surface of the target object in the conventional PSD sensor.
5 is a view showing the voltage change of the PSD sensor according to the displacement of the measurement surface of the target object and the color change of the measurement surface of the target object in the PSD sensor according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in this specification and claims should not be construed in a common or dictionary sense, and the inventors will be required to properly define the concepts of terms in order to best describe their invention. Based on the principle that it can, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, at the time of the present application, It should be understood that there may be water and variations.

FIG. 1 is a schematic diagram illustrating a basic concept of position measurement using an optical triangular method, and FIG. 2 is a schematic diagram illustrating a concept of a PSD device 300 and first and second current voltage converters 400 and 410. 3 is a system configuration diagram of controlling the light intensity of the laser light source based on the light amount signal I by the calculation unit of the PSD sensor, and FIG. 4 is a displacement of the measurement surface of the target object and the measurement of the target object in the conventional PSD sensor. 5 is a diagram illustrating a voltage change of a PSD sensor according to a color change of a plane, and FIG. 5 illustrates a voltage change of a PSD sensor according to a displacement of a measurement surface of an object and a color change of a measurement surface of an object in the PSD sensor according to the present invention. The figure shown. Hereinafter, a description will be given with reference to FIGS. 1 to 5.

(Embodiment 1)

PSD sensor according to the first embodiment of the present invention, the laser light source 100 for generating a laser light; A light receiving lens 200 for condensing the laser light diffused and reflected on a measurement surface (surface) of an object; A PSD element (300) for forming light collected by the light receiving lens (200); A first current voltage converter 400 and a second current voltage converter 410 converting the first current and the second current from both ends of the PSD element 300 into first and second voltages, respectively; A calculator (not shown) for calculating a light quantity signal (I) and a distance signal (D) based on the first voltage and the second voltage; And a controller 500 that controls the laser light source 100 by using a result of comparing the reference light amount signal R and the light amount signal I.

Here, the first current voltage converter 400 and the second current voltage converter 410 further comprise an amplifier for amplifying while converting the first current and the second current into a first voltage and a second voltage, respectively. Can be.

Here, it is preferable that the light quantity signal I is as shown in Equation 1 below.

[Equation 1]

Figure 112010080370238-pat00003

I (intensity) is the light quantity signal, K 1 is the proportional constant of the first current voltage converter, K 2 is the proportional constant of the second current voltage converter, X 1 is the first current, X 2 is the second current, K 1 X 1 is a first voltage and K 2 X 2 is a second voltage.

In addition, the distance signal (D) is represented by the following equation (2).

&Quot; (2) "

Figure 112010080370238-pat00004

D (distance) is a distance signal, K 1 is a proportional constant of the first current voltage converter, K 2 is a proportional constant of the second current voltage converter, X 1 is a first current, X 2 is a second current, and K 1 X 1 is a first voltage and K 2 X 2 is a second voltage.

The meaning of the equation of the distance signal will be described. In order to know the position d of the measurement light, the distances d1 and d2 to one end or the other end of the PSD element may be known. Here, the current values X1 and X2 outputted to the one end and the other end of the PSD element by the measurement light are inversely proportional to the resistance from the position of the measurement light to one end and the other end of the PSD element, that is, inversely proportional to d1 and d2. That is, when the current values X1 and X2 outputted to one end and the other end of the PSD element by the measurement light are known, the position of the measurement light can be known.

Here, K 1 X 1 + K 2 X 2 is a value proportional to the amount of light and uses a division operation to obtain a normalization effect. When the amount of light is usually constant, the material of the PSD element is uniform, and the condition that the first current voltage converter and the second current voltage converter are identically satisfied is satisfied, K1 and K2 are constant. In this case, since the common term between the denominator and the numerator is divided to become normalization, the distance can be expressed linearly as shown in the following equation.

&Quot; (3) "

Figure 112010080370238-pat00005

However, the amount of received light varies depending on the change in the amount of received light due to the change of the position of the target object, or the reflection conditions such as the color or roughness of the measurement surface. If the material of the PSD element is not uniform, the displacement becomes not linear because K1 ≠ K2. do.

In the present invention, in order to solve such a problem, if the actual measured light intensity signal I is inputted as a feedback signal of the light intensity controller, the controller applies a voltage to the laser diode driver so as to obtain a desired light intensity signal, which is always a constant light intensity signal. To keep (I).

The output signal of the controller 500 is modulated by the modulation signal of the modulator (not shown) and input to the laser light source 100 to feedback control the light intensity of the laser light source so that the light amount signal I is constant. . That is, when the amount of light formed in the PSD element 300 is small, the light intensity of the laser light source is controlled to increase. When the amount of light formed in the PSD element 300 is large, the light intensity of the laser light source is controlled.

As an example of such feedback control, a value obtained by subtracting the light quantity signal I from the reference light quantity signal R may be input to the laser light source 100. As long as the object of the present invention can be achieved, it is not limited to PI control.

The modulator may use PAM (Pulse Amplitude Modulation) or AM (Amplitude Modulation), but the present invention is not limited thereto and may be variously modified, changed, or modified to achieve the object of the present invention.

4 and 5, the stability of the PSD sensor according to the color change and the displacement change of the object in the PSD sensor according to the present invention, rather than the stability of the PSD sensor according to the color change and displacement change of the object in the conventional PSD sensor. You can see this improvement.

(Second Embodiment)

On the other hand, the control method of the PSD sensor according to the second embodiment of the present invention, the laser light source for generating a laser light; A light receiving lens for collecting the laser light diffused and reflected from a surface of a target object; And a PSD element for forming light condensed by the light receiving lens. The method of controlling a PSD sensor comprising: converting a first current output from one end of the PSD element into a first voltage; ; A second current voltage conversion step of converting a second current coming from the other end of the PSD element into a second voltage; A calculation step of calculating a light quantity signal and a distance signal based on the first voltage and the second voltage; And a control step of controlling the laser light source by using a result of comparing the reference light quantity signal with the light quantity signal. Since the remaining parts are already described in the first embodiment, description thereof will be omitted.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

100 laser light source
200 light receiving lens
300 PSD Elements
400 first current voltage converter
410 second current voltage converter
500 controls
R reference light intensity signal
I light signal
D distance signal

Claims (16)

A laser light source for generating laser light;
A light receiving lens for collecting the laser light diffused and reflected from a surface of a target object;
A PSD element for forming light collected by the light receiving lens;
A first current voltage converter and a second current voltage converter configured to convert first and second currents output from both ends of the PSD element into first and second voltages, respectively;
A calculator configured to calculate a light quantity signal and a distance signal based on the first voltage and the second voltage; And
And a controller configured to control the laser light source by using a result of comparing a reference light amount signal and the light amount signal.
The first current voltage converter and the second current voltage converter further include an amplifier for amplifying while converting the first current and the second current into the first voltage and the second voltage, respectively,
The light quantity signal is equal to the following Equation 1,
[Equation 1]
Figure 112012076386995-pat00006

I (intensity) is the light quantity signal, K 1 is the proportional constant of the first current voltage converter, K 2 is the proportional constant of the second current voltage converter, X 1 is the first current, X 2 is the second current,
The distance signal is equal to the following Equation 2,
&Quot; (2) "
Figure 112012076386995-pat00007

D (distance) is a distance signal, K 1 is a proportional constant of the first current voltage converter, K 2 is a proportional constant of the second current voltage converter, X 1 is a first current, X 2 is a second current,
The control unit inputs a value obtained by subtracting the light quantity signal from the reference light quantity signal as an input to the laser light source,
And a modulator for modulating the output of the controller and applying the modulated output to the laser light source.
The modulator uses PAM (Pulse Amplitude Modulation) or AM (Amplitude Modulation) method,
The output signal of the control unit is modulated by the modulation signal of the modulator and input to the laser light source to control the light intensity feedback of the laser light source so that the light quantity signal is constant, but when the amount of light formed in the PSD element is small, the laser light source And control the light intensity of the light source to be increased, and to control the light intensity signal to be constant by controlling the intensity of the laser light source to be small when the amount of light formed in the PSD element is large. delete delete delete delete delete delete delete A laser light source for generating laser light; A light receiving lens for collecting the laser light diffused and reflected from a surface of a target object; And a PSD element for forming light collected by the light receiving lens.
A first current voltage converting step of converting a first current output to one end of the PSD element into a first voltage;
A second current voltage conversion step of converting a second current coming from the other end of the PSD element into a second voltage;
A calculation step of calculating a light quantity signal and a distance signal based on the first voltage and the second voltage; And
And controlling the laser light source by using a result of comparing the reference light amount signal with the light amount signal.
The first current voltage converting step and the second current voltage converting step further include a first amplifying step and a second amplifying step of amplifying the first current and the second current while converting the first current and the second current into the first voltage and the second voltage, respectively. Including,
The light quantity signal is equal to the following Equation 1,
[Equation 1]
Figure 112012076386995-pat00013

I (intensity) is the light quantity signal, K 1 is the proportional constant of the first current voltage converter, K 2 is the proportional constant of the second current voltage converter, X 1 is the first current, X 2 is the second current,
The distance signal is equal to the following Equation 2,
&Quot; (2) "
Figure 112012076386995-pat00014

D (distance) is a distance signal, K 1 is a proportional constant of the first current voltage converter, K 2 is a proportional constant of the second current voltage converter, X 1 is a first current, X 2 is a second current,
The control unit inputs a value obtained by subtracting the light quantity signal from the reference light quantity signal to the laser light source.
And a modulator for modulating the output of the controller and applying the modulated output to the laser light source.
The modulator uses PAM (Pulse Amplitude Modulation) or AM (Amplitude Modulation) method,
The output signal of the control unit is modulated by the modulation signal of the modulator and input to the laser light source to control the light intensity feedback of the laser light source so that the light quantity signal is constant, but when the amount of light formed in the PSD element is small, the laser light source The control method of the PSD sensor, characterized in that to control the light intensity of the large, and to control the light intensity signal is constant by controlling the intensity of the laser light source to be small when the amount of light formed on the PSD element is large.
delete delete delete delete delete delete delete
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000266515A (en) * 1999-03-18 2000-09-29 Olympus Optical Co Ltd Height measuring instrument
JP2004343880A (en) * 2003-05-15 2004-12-02 Matsushita Electric Ind Co Ltd Motor controller

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000266515A (en) * 1999-03-18 2000-09-29 Olympus Optical Co Ltd Height measuring instrument
JP2004343880A (en) * 2003-05-15 2004-12-02 Matsushita Electric Ind Co Ltd Motor controller

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