JP3418903B2 - Optical scanning device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device which scans a light beam in a fan shape to recognize the presence / absence of an object in a detection range and recognize its shape.

[0002]

2. Description of the Related Art As a conventional optical scanning device of this type, there is, for example, the one shown in FIG.

This optical scanning device is equipped with a sensor head 1 installed above a gantry (not shown) installed on a road before the toll booth. The sensor head 1 is a light beam. Of the light beam emitted from the light projecting means 2, the light scanning means 4 for scanning the light beam from the light projecting means 2 in a fan shape across the road R, and the light beam emitted while being scanned by the light scanning means 4. And a light receiving means 6 for receiving the reflected light.

The light projecting means 2 is a semiconductor laser or L
It is composed of a single light emitting element 8 such as an ED, and a light projecting lens 10 which collects the light from the light emitting element 8 and outputs it as parallel light beams as possible.

Further, the light scanning means 4 is a polygon mirror (rotating polygon mirror) 12 for reflecting the light beam from the light projecting means 2.
And a motor 14 that drives the polygon mirror 12 to rotate at a constant speed.

Further, the light receiving means 6 receives a light receiving lens 16 for collecting reflected light from a road surface R of a road or a moving object C such as an automobile, and the light collected by the light receiving lens 16 for receiving an electric signal. And a light receiving element 18 such as a PD (photodiode) for converting into

At a position close to the polygon mirror 12 of the sensor head 1, a light receiving element such as a PD (hereinafter referred to as an SOS light receiving element) for detecting a reference position for starting scanning of the light beam by the optical scanning means 4. 20) is arranged.

In the optical scanning device having the above structure, the light emitting element 8 of the light projecting means 2 emits pulsed light at a predetermined cycle. The reason why the light emitting element 8 is made to emit light in pulses is to eliminate the influence of sunlight and the like. The period of pulsed light emission is, of course, set to, for example, 50 μsec so as to be longer than the time required for the light beam to make one round trip between the optical scanning device and the road surface of the road R.

The light from the light emitting element 8 is converted into a parallel light beam by the light projecting lens 10, which is reflected by the polygon mirror 12 and emitted toward the road surface R. In that case, since the polygon mirror 12 is constantly rotated by the motor 14 at a constant speed, the light beam reflected by the polygon mirror 12 is sequentially fan-shaped scanned within one plane while crossing the road surface R at a substantially right angle. To be done.

In scanning the light beam by the polygon mirror 12, as shown in FIG. 15, when the light beam reaches one of the extreme end positions of the scanning range, the light beam is S.
Since the OS light receiving element 24 is irradiated with the SO light at this time
The output of the S light receiving element 24 is taken out as a scanning start detection signal (hereinafter referred to as an SOS signal) which is a reference for scanning start.

When an object C such as an automobile exists on the road surface R, the light beam emitted while being sequentially scanned from the sensor head 1 is reflected by the object C on the way to the road surface R. Therefore, the time required for light reception by the light receiving element 18 is shorter than that when the object C does not exist. Therefore, the presence or absence and the shape of the object C are measured by measuring the time required for projecting and receiving light by a signal processing circuit (not shown).

Further, a concrete method for measuring the shape and the like of the object C will be described with reference to FIGS. 16 and 17.

Now, the pulse emission interval of the light emitting element 8 of the light projecting means 2 is w, the total scanning angle of one scanning of the light beam is α, the total number of pulses included in this scanning angle α is N, the SOS light receiving element 24.
From the time when the SOS signal is output from T _L0 , SOS
When the scanning angle formed by the light beam with respect to the road surface R at the time when the nth pulse emission is performed after the signal is obtained is
This scanning angle θ is given by the following equation.

Θ = (α / N) · {n− (T _L0 / w)} Moreover, when the reflection position of the light beam by the polygon mirror 12 of the sensor head 1 is the origin o, from the origin o to the road surface R distance L ₀ of are known, also, when an object q of the virtual point shaped and that there the height y from the road surface R, the perpendicular (indicated by a chain line in FIG. 16) to a position apart a distance x , The distance L from the origin o to the object q can be known from the time required for light projection and reception when the light beam is reflected by this object q.
The positions x and y of q can be obtained as follows using the value of the scanning angle θ obtained by the above equation.

X = L · sin θ y = L ₀ −L · cos θ Therefore, the position x, y of the object q on which the light beam is reflected can be specified from the equation, and therefore the shape of the object C such as a vehicle is measured. can do.

[0016]

By the way, the light projecting means 2
Mounting error of the light emitting element 8 and the light projecting lens 10 that constitute
The position where the light beam is applied to the SOS light receiving element 24 deviates from the normal position due to an optical misalignment in the arrangement of the light projecting means 2 and the polygon mirror 12, and therefore the SOS.
The signal output timing may also deviate from the preset desired time by ΔT as shown by the broken line in FIG. 17 (a).

However, in the prior art, the above time T _L0
Is preliminarily set in the manufacturing stage of the device, and the scanning angle θ is determined by an equation assuming that the light beam becomes vertical to the road surface R when this time T _L0 has elapsed after the SOS signal was obtained. ing.

Therefore, when the output timing of the SOS signal is shifted by the time ΔT as described above, the light beam becomes
Although the light beam is actually deviated from the vertical position with respect to the road surface R by Δθ corresponding to this ΔT, the light beam is considered to be perpendicular to the road surface R and the scanning angle θ is obtained. An error of Δθ occurs, and as a result,
, The positions x and y of the object q obtained by the equation also generate an error, and the accurate position cannot be measured.

Further, when the sensor head 1 is installed, or after the sensor head 1 is installed, the sensor head 1 itself changes from a position perpendicular to the road surface R by Δθ.
Even in the case of tilting by an amount, conventionally, when a predetermined time T _L0 has elapsed after the SOS signal was obtained, it is considered that the light beam becomes perpendicular to the road surface, and the scanning angle θ is determined by an equation. Therefore, similarly, the positions x and y of the object q obtained by the equation also generate an error, and the accurate position cannot be measured.

The present invention has been made in order to solve the above problems, and an object thereof is to always obtain an accurate scanning angle and further improve the measurement accuracy of the shape of an object or the like. To do.

[0021]

In order to solve the above problems, the present invention provides a light projecting means for emitting a light beam, and a light scanning means for scanning the light beam from the light projecting means in a fan shape.
The sensor head is provided with a light receiving means for receiving the reflected light of the light beam scanned by the light scanning means, and a scan start detecting means for detecting a reference position for starting the light beam scanning by the light scanning means. The optical scanning device employs the following configuration.

That is, in the invention according to claim 1,
A differentiating means is provided at a position facing the sensor head so that a part of the light beam along the optical scanning direction is different from the other part in the amount of reflected light or the light projecting / receiving time, while the differentiating means is provided. Correction means for correcting the scanning angle of the light beam based on the light reception signal obtained by receiving the reflected light from the light receiving means and the scanning start detection signal from the scanning start detection means.

According to a second aspect of the invention, in the structure of the first aspect, a scanning angle correction guide is provided, and the differentiating means is provided in the scanning angle correction guide. The reflection coefficient is different from that of

According to a third aspect of the invention, in the structure of the first aspect, a scanning angle correction guide is provided, and the differentiating means is provided in the scanning angle correction guide. The shape and the time required for light projection and light reception are different from each other.

In the invention according to claim 4, in the structure according to any one of claims 1 to 3, the position of the differentiating means is the position of the pendulum vertically lowered from the installation position of the sensor head. Is set to match.

According to a fifth aspect of the invention, in the structure according to the first aspect, the optical scanning means is a polygon mirror, and the scanning start detecting means is a polygon mirror for the light beam emitted from the light projecting means. A light-emitting element that constantly emits light toward the polygon mirror and a light-receiving element that receives the reflected light from the polygon mirror of the light-emitting element are provided at a position apart from the irradiation position of.

According to a sixth aspect of the present invention, in the structure of the first aspect, the optical scanning means is a polygon mirror, and the scanning start detecting means is a rotary encoder.

In the invention according to claim 7, in the structure according to claim 1, the optical scanning means is a galvano mirror, and the scanning start detection means is based on a drive signal for driving the galvano mirror. The reference position of the scanning start of is detected.

In the invention according to claim 8, in the structure according to claim 1, the optical scanning means is a galvano mirror, and the scanning start detection means is a scan obtained for controlling the scanning position of the galvano mirror. The reference position for starting scanning of the light beam is detected based on the position feedback signal.

[0030]

FIG. 1 is a perspective view showing a state in which a sensor head and a scanning angle correction guide of an optical scanning device according to an embodiment of the present invention are installed on a road, and the conventional example shown in FIG. The same reference numerals are given to the parts corresponding to.

In this optical scanning device, 1 is a sensor head, 2 is light projecting means, 4 is optical scanning means, 6 is light receiving means, and 8 is
Is a light emitting element, 10 is a light projecting lens, 12 is a polygon mirror, 14 is a driving motor, 16 is a light receiving lens, 18 is a light receiving element, and 24 is an SOS light receiving element. These configurations are the same as in the conventional example. Therefore, detailed description is omitted here.

Further, the optical scanning device of this embodiment has a scanning angle correction guide 22 for initial calibration arranged at a position on the road surface R facing the sensor head 1.

In this scanning angle correction guide 22, the central portion 22a along the optical scanning direction of the light beam is the other portion 2 on the left and right thereof.
The central portion 22a thereof has a reflection coefficient different from that of 2b.
Is applied in white and the other portion 22b is applied in black. Therefore, the central portion 22a of the scanning angle correction guide 22 corresponds to the differentiating means in the claims. The central portion 22
For a, a reflector having a large reflection coefficient can be used in addition to the white coating as in this example.

FIG. 2 is a block diagram showing a part of the light emitting / receiving control circuit of the optical scanning device.

In the figure, 30 is an SOS light receiving element 20.
The SOS circuit for detecting the scanning angle θ in the polygon mirror by taking in the detection output from the polygon mirror 12,
Scan drive circuit for controlling the motor 14 for rotating
Reference numeral 4 denotes a light projecting circuit for causing the light emitting element 8 of the light projecting means 6 to perform pulsed light emission at a predetermined cycle w, and 36 denotes a light receiving circuit for amplifying a detection signal from the light receiving element 18 of the light receiving means 10. Reference numeral 38 denotes the detection output of the light receiving circuit 36 and SOS.
A signal processing circuit that measures the shape of an object based on the data of the scanning angle θ obtained by the circuit 30, and 40 is each of the above-mentioned units 3
It is a control circuit for controlling the operations of 0 to 38.

Then, the SOS light receiving element 20 and the SO
The S circuit 30 corresponds to the scanning start detecting means in the claims, and the signal processing circuit 38 and the control circuit 40 correspond to the correcting means in the claims.

When the sensor head 1 is installed on the upper part of a gantry (not shown) installed on the road, as shown in FIG. 3, the scanning angle correction guide 22 is placed on the road surface R,
A pendulum 28 is attached to the tip of the thread 27 hung down from the sensor head 1 to almost reach the guide 22 so that the position of the pendulum 28 and the position of the central portion 22a of the scanning angle correction guide 22 coincide with each other. As a result, the sensor head 1 is mounted vertically to the road surface R, and the vertical direction of scanning of the light beam can be set accurately.

In this state, next, the scanning drive circuit 32 is controlled to rotate the polygon mirror 12 by the motor 14 at a constant speed, while the light emitting circuit 34 pulse-emits the light emitting element 8 at a predetermined cycle w. The beam is emitted toward the road surface R of the road and is scanned in a fan shape.

This light beam is irradiated onto the scanning angle correction guide 22 placed on the road surface R. In this case, since the reflection coefficient of the central portion 22a is large and the reflection coefficient of the other portion 22b is small, The reflected light from the central portion 22a and the reflected light from the other portion 22b are different in the amount of light incident on the light receiving element 18, and therefore the power P of the output signal from the light receiving circuit 36 is also different. That is, in the case of this example, the central portion 22a
The power when receiving the reflected light from the other part is 2
It becomes larger than the power when the reflected light from 2b is received.

Therefore, in the signal processing circuit 38, as shown in FIG.
As shown in (a), if the threshold Pth is set in advance for the power P of the output signal from the light receiving circuit 36,
When the output signal of the light receiving circuit 36 exceeds the level of the threshold value Pth, the light beam at this point irradiates the position of the central portion 22a and is perpendicular to the road surface R.

The signal processing circuit 38, as shown in FIG.
The time (hereinafter referred to as the initial correction time) T _L required from the time when the SOS signal is output from the SOS circuit 30 to the time when the output signal of the light receiving circuit 36 exceeds the level of the threshold value Pth is measured. Then, this initial correction time T _L is stored in a memory or the like (not shown) inside the control circuit 40.

By doing so, the mounting error of the light emitting element 8 or the light projecting lens 10 which constitutes the light projecting means 2, and the light projecting means 2
And the output timing of the SOS signal is deviated from the intended time due to an optical displacement in the arrangement of the polygon mirror 12, or the polygon mirror 2 is attached so as to be slightly inclined with respect to the road surface R. Even in such a case, the initial correction time T _L from the time when the SOS signal is obtained until the light beam becomes vertical to the road surface R can be accurately obtained.

Therefore, when compared with the prior art, FIG.
The time T _L0 shown in is a uniquely determined value, but the initial correction time T _L (see FIG. 5) initially set in this embodiment is corrected according to the mounting error of the sensor head 1 or the like. It is a value.

In FIG. 4 (a), the position of the central portion 22a is specified by directly comparing the power P of the output signal of the light receiving circuit 3 with the threshold value Pth. For example, as shown in FIG.
When the peak of the output signal of 6 exceeds the preset threshold Pth, the peak widths u ₁ and u ₂ are measured to obtain the peak widths.
When u ₁ and u ₂ exceed a certain value, the central portion 22
It is also possible to specify the position of a.

When measuring the shape of an object such as a vehicle passing through a road, the above-mentioned initial correction time T _L is used.
The scanning angle θ formed by the light beam with respect to the road surface R is obtained by the following equation.

Θ = (α / N) · {n− (T _L / w)} where w is the pulse emission interval of the light emitting element 8, α is the total scanning angle of one scanning of the light beam, and N is the total scanning. The total number of pulses included in the angle α, n is the number of pulsed light emission after the SOS signal is obtained.

If the initial correction time T _L is accurate in the equation, the scanning angle θ can also be accurately obtained. Therefore, the position of the object on which the light beam is reflected can be calculated by the above equation.
The x and y can be accurately obtained, and the accuracy in measuring the cross-sectional shape of an object can be increased.

Therefore, for example, if this optical scanning device is used as a vehicle measuring device, the vehicle width and vehicle height of a vehicle traveling on a road can be accurately measured, and by using it together with a vehicle speed sensor. It is possible to measure the overall shape and vehicle length of the vehicle.

Other Embodiments The following various modifications can be added to the above embodiment.

(1) As shown in FIG. 6, the scanning angle correction guide 23 allows the sensor heads 1a and 1b to simultaneously adjust the positions of the two sensor heads 1a and 1b.
It is also possible to provide two differentiating means 23a, 23a corresponding to the above.

Further, in the scanning angle correction guides 22 and 23 shown in FIGS. 1 and 6, contrary to the case of these embodiments, the differentiating means 22a and 23a are made black with a small reflection coefficient, and the other means. The portions 22b and 23b may be white with a large reflection coefficient. In that case, if the output signal of the light receiving circuit 36 is compared with the threshold Pth, the threshold Pth
When the light beam falls below the level, the light beam is used as the differentiating means 22.
It can be determined that they are at the positions a and 23a and are perpendicular to the road surface R.

Further, as shown in FIG. 7 (a), the scanning angle correction guide 24 is arranged so that the time required for projecting and receiving light differs.
The central part 24a, which serves as a differentiating means, is connected to the other parts 2
It is also possible to have a shape projecting above 4b.

In this case, as shown in FIG. 7B, the time T required for the light projecting and receiving light until the light emitting element 8 is pulsed by the light projecting circuit 34 and the light receiving signal is output by the light receiving circuit 36 is measured. That is, when the time T required for projecting and receiving the light becomes short, the light beam is at the position of the central portion 24a and the road surface R
It can be judged that it is perpendicular to.

Contrary to the case of FIG. 7A, the central portion 2
The same effect can be obtained by forming 4a into a shape recessed from the other left and right portions 24b.

The scanning angle correction guides 22, 23, 24 may be used not only temporarily for initial setting but also may be permanently installed on the road surface R. Further, as shown in FIG. 8, when the road is an asphalt road, a white line 26 is drawn immediately below the sensor head 1, and a substance that enhances the reflection coefficient is mixed into the white line 26 to differentiate it. It is also possible to

In this way, the scanning angle correction guides 22, 2
When 3, 24 and the white line 26 serving as a differentiating means are permanently provided, it is convenient because the correction can be performed at any time even if the sensor head 1 is slightly tilted due to vibration or the like.

(2) In the above embodiment, a part of the light beam scanned by the polygon mirror 12 while being pulsed by the light emitting element 8 of the light projecting means 2 is received by the SOS light receiving element 20. However, the SOS element 20 may be omitted and the configuration shown in FIG. 9 may be employed.

That is, what is shown in FIG.
A photoreflector 50 including a light emitting element 52 such as a light emitting diode and a light receiving element 54 such as a phototransistor is arranged facing the polygon mirror 12 at a position apart from the irradiation position of the light beam emitted from the polygon mirror 12. ing.

Moreover, in the photo reflector 50, the light emitting element 52 is not always pulsed, but is kept in a light emitting state at all times, and each reflecting surface of the polygon mirror 12 is at the scanning start position of the light beam. The light from the light emitting element 52 is set to be incident on the light receiving element 54 only when a specific reference angle is obtained.

As shown in FIG. 10, when the light emitting element 8 of the light projecting means 2 emits pulsed light (see FIG. 10A), FIG.
Since the light beam is incident on the SOS light receiving element 20 having the configuration shown in FIG.
The output timing of the SOS signal obtained by the SOS light receiving element 20 may be shifted by a maximum of the pulse emission interval w (see 10 (b)). Therefore, it is difficult to make the resolution of the initial correction time T _L shown in FIG. 5 smaller than the pulse emission interval w.

On the other hand, if the photo-reflector 50 having the structure shown in FIG. 9 is provided, the reflecting surface of the polygon mirror 12 is set to the scanning start position of the light beam without being affected by the interval w of pulsed light emission. Since the light receiving signal is immediately output from the light receiving element 54 when it reaches a certain specific reference angle (see FIG. 10 (c)), this light receiving signal can be used as the SOS signal, and as a result, Initial correction time T _L
The resolution of can be further improved.

Instead of using the photo reflector 50, a rotary encoder for detecting the rotation amount of the polygon mirror 12 can be used as the scanning start detecting means.

(3) In the above embodiment, the polygon mirror 12 is used as the light scanning means, but the invention is not limited to this, and it is also possible to use a galvano mirror.

In the case of using this galvanometer mirror, instead of providing the SOS light receiving element 20 and the SOS circuit 30 described above, for example, the scanning start detecting means can be configured as shown in FIG.

That is, in the configuration shown in FIG. 11, with respect to the scanning drive circuit 58 for swinging the galvanometer mirror,
Since a sine wave signal of a predetermined frequency is output from the frequency generator 60 as a drive signal (see FIG. 12 (a)), this sine wave signal is input to the peak detection circuit 62 to detect its peak position and A pulse signal is output for each peak (see FIG. 12 (b)). Then, this peak detection circuit 62
Is used as the SOS signal.

With this structure, by providing the peak detection circuit 62, the SOS light receiving element 20 shown in FIG.
The SOS circuit 30 can be omitted.

Further, as shown in FIG. 13, in order to feedback control the scanning position of the galvanometer mirror, if the scanning drive circuit 58 has a function of outputting a feedback signal indicating the scanning position, the feedback signal is fed back. It is also possible to input the signal to the signal processing circuit 64, detect the reference position of the scanning start of the light beam by the feedback signal processing circuit 64, and use the detection output as the SOS signal.

According to this structure, the scanning angle can be detected more accurately than in the case of FIG.

[0069]

According to the present invention, the following effects can be obtained.

(1) In the invention according to the first aspect, since an accurate scanning angle is always obtained, the measurement accuracy of the shape of the object and the like becomes higher than the conventional one.

In this case, if the scanning angle correction guide according to the second or third aspect of the invention is used, the initial setting when the sensor head is installed can be easily performed. In particular, with the configuration according to the fourth aspect of the present invention, since the sensor head and the differentiating means can be accurately aligned with each other, it is possible to minimize the occurrence of error factors when the sensor head is installed.

(2) In the invention according to claim 5 or 6, when a polygon mirror is used, the resolution for obtaining the initial correction time is increased and a more accurate scanning angle can be obtained.

(3) In the invention according to claim 7 or claim 8, when a galvanometer mirror is used, the resolution for obtaining the initial correction time is high and a more accurate scanning angle can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which a sensor head and a scanning angle correction guide of an optical scanning device according to an embodiment of the present invention are installed on a road.

FIG. 2 is a block diagram showing a configuration of a controller portion of the optical scanning device of FIG.

FIG. 3 is an explanatory diagram showing how to adjust the positions of the sensor head and the scanning angle correction guide of the optical scanning device of the present invention.

FIG. 4 is a diagram for explaining a method for detecting the position of the differentiating means by the optical scanning device of FIG.

5 is a timing chart provided for explaining an initial correction time based on an SOS signal of the optical scanning device of FIG. 1 and a light receiving signal obtained by a differentiating unit.

FIG. 6 is a perspective view showing a modified example of the scanning angle correction guide.

FIG. 7 is a view showing a modified example of the scanning angle correction guide and a relationship between the light emitting and receiving time based on the modification.

FIG. 8 is a perspective view of a case where the differentiating means of the present invention is permanently installed on a road.

FIG. 9 is a front view showing a state in which a photo reflector is arranged on a polygon mirror.

FIG. 10 shows a case where an SOS signal is obtained by an SOS light receiving element,
10 is a timing chart provided for explaining a case where an SOS signal is obtained using the photo reflector of FIG. 9.

FIG. 11 is a block diagram showing a configuration of an SOS signal generating means when a galvano mirror is used as the optical scanning means.

12 is a timing chart provided for explaining the operation of FIG.

FIG. 13 is a block diagram showing a modification of the configuration of FIG.

FIG. 14 is a perspective view showing a state in which a sensor head portion of a conventional optical scanning device is installed on a road.

FIG. 15 is a front view of the sensor head of FIG.

FIG. 16 is an explanatory diagram in the case of detecting the position of an object by scanning a light beam in a fan shape.

FIG. 17 is a timing chart showing the relationship between the SOS signal and the light emission pulse in the conventional case.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sensor head, 2 ... Light projecting means, 4 ... Optical scanning means, 6
... light receiving means, 8 ... light emitting element, 10 ... light projecting lens, 12 ...
Polygon mirror, 16 ... Light receiving lens, 18 ... Light receiving element,
20 ... SOS light receiving element, 22, 23, 24 ... Scanning angle correction guide, 22a, 23a, 24a, 26 ... Differentiating means, 2
8 ... Pendulum, 30 ... SOS circuit, 32 ... Scan drive circuit,
34 ... Projecting circuit, 36 ... Photo receiving circuit, 38 ... Signal processing circuit, 40 ... Control circuit, 50 ... Photo reflector, 52 ...
Light emitting element, 54 ... Light receiving element, 62 ... Peak detection circuit, 6
4 ... Feedback signal processing circuit.

Claims (8)

(57) [Claims] 1. A light projecting means for emitting a light beam, and a light scanning means for scanning the light beam from the light projecting means in a fan shape.
The sensor head is provided with a light receiving means for receiving the reflected light of the light beam scanned by the light scanning means, and a scan start detecting means for detecting a reference position for starting the light beam scanning by the light scanning means. In the optical scanning device, a differentiating means is provided at a position facing the sensor head so that a part of the light beam along the optical scanning direction is different in reflected light amount or light emitting / receiving time compared to other parts. On the other hand, a correction for correcting the scanning angle of the light beam based on a light receiving signal obtained by receiving the reflected light from the differentiating means by the light receiving means and a scan start detection signal from the scan start detecting means. An optical scanning device comprising means. 2. The optical scanning device according to claim 1, further comprising a scan angle correction guide, wherein the differentiating means is provided in the scan angle correcting guide, and the differentiating means is different from other portions in reflection coefficient. An optical scanning device, characterized in that 3. The optical scanning device according to claim 1, further comprising a scanning angle correction guide, wherein the differentiating means is provided in the scanning angle correction guide, and the differentiating means is arranged to project and receive other portions. An optical scanning device, wherein the optical scanning device is configured to have different shapes in different time required. 4. The optical scanning device according to claim 1, wherein the position of the differentiating means matches the position of a pendulum vertically lowered from the installation position of the sensor head. An optical scanning device characterized by being set. 5. The optical scanning device according to claim 1, wherein the optical scanning means is a polygon mirror, and the scanning start detecting means is separated from an irradiation position of the light beam emitted from the light projecting means onto the polygon mirror. An optical scanning device comprising: a light emitting element that constantly emits light toward a polygon mirror and a light receiving element that receives the reflected light from the polygon mirror of the light emitting element. 6. The optical scanning device according to claim 1, wherein the optical scanning means is a polygon mirror, and the scanning start detecting means is a rotary encoder. 7. The optical scanning device according to claim 1, wherein the optical scanning means is a galvano mirror, and the scanning start detecting means is a reference for starting scanning of the light beam based on a drive signal for driving the galvano mirror. An optical scanning device for detecting a position. 8. The optical scanning device according to claim 1, wherein the optical scanning means is a galvano mirror, and the scanning start detection means uses a scanning position feedback signal obtained for controlling the scanning position of the galvano mirror. An optical scanning device characterized by detecting a reference position for starting scanning of a light beam based on the above.