Polygon mirror scanner

Abstract

Disclosed is a polygon mirror scanner capable of maintaining a constant rotation speed of a polygon mirror and accurately detecting an origin point of the polygon mirror with a simple configuration. The disclosed polygon mirror scanner includes: a polygon mirror rotated by a rotation shaft and including a plurality of reflective surfaces; a driving motor for rotating the polygon mirror around the rotation shaft; an encoder for measuring a real-time rotation period of the polygon mirror; and a motor control unit which controls the driving motor so that with reference to a result value obtained by comparing a preconfigured reference rotation period with the real-time rotation period, the real-time rotation period matches the reference rotation period.

Description

Polygon Mirror Scanner

[0001] The present invention relates to a polygon mirror scanner capable of maintaining a constant rotation speed of a polygon mirror and accurately detecting the origin of the polygon mirror with a simple configuration.

[0002]

[0003] Recently, as vehicles become more intelligent, research on autonomous vehicles and advanced driver assistance systems (ADAS) is actively being conducted.

[0004] Figure 1 is a drawing showing an example of the detection range of various sensors applied to a vehicle.

[0005] To implement autonomous vehicles or vehicle driver assistance systems, various sensors are essential. These sensors include radar, polygonal LIDAR, cameras, and ultrasonic sensors, as illustrated in Figure 1.

[0006] In particular, in the case of LiDAR, although the object identification accuracy is somewhat low, due to the advantage of being able to obtain accurate distance information, it is installed and used in the front and rear of most autonomous vehicles. There is a TOF (time of flight) method for measuring distance of LiDAR, which calculates the distance by multiplying the time taken for the round trip between the LiDAR transmitter and the object by the speed of light. The TOF method is classified into mechanical and non-mechanical types depending on the method of controlling the direction of travel of the light irradiated from the transmitter to the object.

[0007] Among mechanical methods, there is a method that uses the rotational power of a motor to rotate the components of the light transmitting unit to secure a wide field of view, and there are several methods for rotating the components of the light transmitting unit, such as a method of rotating a reflective mirror, an oscillating mirror method, and a scanning method using a photorefractive element.

[0008]

[0009] For polygon mirror scanners using mechanical motors, it's crucial to maintain a constant rotation speed (i.e., the rotation speed of the polygon mirror). Even a slight deviation in rotation speed can lead to significant errors in long-distance detection. Furthermore, for polygon mirror scanners, it's crucial to accurately determine the position of the reflective surface forming the polygon mirror.

[0010] Accordingly, this specification proposes a polygon mirror scanner that can maintain a constant rotation speed of a polygon mirror and accurately detect the origin of the polygon mirror with a simple configuration.

[0011]

[0012] The purpose of the present invention is to provide a polygon mirror scanner that can maintain a constant rotation speed of a polygon mirror and accurately detect the origin of the polygon mirror with a simple structure.

[0013]

[0014] A polygon mirror scanner according to an embodiment of the present invention,

[0015] A polygon mirror that rotates around a rotation axis and includes a plurality of reflective surfaces; a driving motor that rotates the polygon mirror around the rotation axis; an encoder that measures a real-time rotation cycle of the polygon mirror; and a motor control unit that controls the driving motor so that the real-time rotation cycle becomes the reference rotation cycle by referring to a result value obtained by comparing the real-time rotation cycle with a preset reference rotation cycle.

[0016] In a polygon mirror scanner according to an embodiment of the present invention, the motor control unit may include a rotation period calculation module that calculates the real-time rotation period by adding the pulse width of a high signal and the pulse width of a low signal transmitted from the encoder during one rotation of the polygon mirror, a rotation period comparison module that calculates a difference value by comparing the real-time rotation period with the reference rotation period, and a control signal generation module that generates a driving motor control signal corresponding to the difference value calculated by the rotation period comparison module by referring to a look-up table.

[0017] In a polygon mirror scanner according to an embodiment of the present invention, the look-up table classifies the difference between the real-time rotation period and the reference rotation period into specific ranges, and a driving motor control signal in the category to which the difference value belongs is indexed and preset.

[0018] In a polygon mirror scanner according to an embodiment of the present invention, the control signal generation module can generate the driving motor control signal for each rotation of the polygon mirror.

[0019] In a polygon mirror scanner according to an embodiment of the present invention, the encoder includes a disk having a plurality of slits formed therein, and the disk includes an origin slit formed by closing any one of the plurality of slits.

[0020] In a polygon mirror scanner according to an embodiment of the present invention, when measuring a real-time rotation period of the polygon mirror, the real-time rotation period can be calculated by adding the high signal pulse width and the low signal pulse width of the slit and the origin slit.

[0021] In a polygon mirror scanner according to an embodiment of the present invention, the motor control unit can compare the reference pulse width time of the origin slit with the real-time pulse width time of the origin slit obtained from the encoder to calculate a difference value, and generate a driving motor control signal corresponding to the calculated difference value by referring to a second look-up table.

[0022]

[0023] In addition, the polygon mirror scanner according to an embodiment of the present invention,

[0024] A polygon mirror that is rotated by a rotation axis and includes a plurality of reflective surfaces; a driving motor that rotates the polygon mirror around the rotation axis; an encoder that includes an origin slit formed by closing any one of a plurality of slits and obtains a real-time pulse width time of the origin slit; a motor control unit that compares a reference pulse width time of the origin slit with a real-time pulse width time of the origin slit to calculate a difference value, and generates a driving motor control signal corresponding to the calculated difference value by referring to a second look-up table.

[0025] In a polygon mirror scanner according to an embodiment of the present invention, the second look-up table classifies the difference between the real-time pulse width time and the reference pulse width time into specific ranges, and the driving motor control signal in the category to which the difference value belongs is indexed and preset.

[0026]

[0027] According to an embodiment of the present invention, the rotation speed of a polygon mirror can be kept constant, and the origin of the polygon mirror can be accurately detected with a simple configuration.

[0028]

[0029] Figure 1 is a drawing showing an example of the detection range of various sensors applied to a vehicle.

[0030] FIG. 2 is a drawing illustrating a polygon mirror scanner according to one embodiment of the present invention.

[0031] Figure 3 is a block diagram showing the configuration of a motor control unit.

[0032] Figure 4 is a diagram illustrating an example of a look-up table.

[0033] FIG. 5 is a perspective view illustrating a polygon mirror scanner according to one embodiment of the present invention.

[0034] Fig. 6 is output data of an encoder acquired by a photo sensor, (a) is output data by a conventional encoder, and (b) is output data by an encoder of the present invention.

[0035] FIG. 7 is a diagram illustrating a computing device according to an embodiment of the present invention.

[0036]

[0037] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0038] The terminology used in the present invention is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In the present invention, it should be understood that the terms "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. Hereinafter, a polygon mirror scanner according to an embodiment of the present invention will be described with reference to the drawings.

[0039]

[0040] FIG. 2 is a drawing illustrating a polygon mirror scanner according to one embodiment of the present invention, FIG. 3 is a block diagram illustrating the configuration of a motor control unit, and FIG. 4 is a drawing illustrating an example of a look-up table.

[0041] Referring to FIG. 2, a polygon mirror scanner (100) according to one embodiment of the present invention includes a polygon mirror (110), a driving motor (120), an encoder (130), and a motor control unit (140).

[0042] The polygon mirror (110) includes a plurality of reflective surfaces, and the plurality of reflective surfaces can reflect a laser (L) incident on the polygon mirror (110). The polygon mirror (110) can rotate around a rotation axis (121), and the plurality of reflective surfaces can be arranged at a predetermined distance from the rotation axis, for example, to surround the rotation axis (121). The centers of the plurality of reflective surfaces can be arranged to have the same shortest distance from the rotation axis (121), but the scope of the present invention is not limited thereto.

[0043] In FIG. 2, the number of reflective surfaces of the polygon mirror (110) is illustrated as 8, but the scope of the present invention is not limited thereto, and a smaller or larger number of reflective surfaces may be provided. For example, the polygon mirror (110) may be provided with a larger number of reflective surfaces in order to scan more points in one rotation as the required scan speed increases. As another example, the more reflective surfaces there are, the larger the size of the polygon mirror (110) may be, or the greater the distortion in the scanned image may be, and therefore, taking this into consideration, the polygon mirror (110) may be provided with an appropriate number of reflective surfaces.

[0044] The polygon mirror (110) can be manufactured using ABS (acrylonitrile butadiene styrene copolymer) resin. Since the polygon mirror (110) can rotate at a high speed (e.g., several thousand rpm), it may be dangerous if the polygon mirror (110) comes into contact with the human body while it is rotating. By using ABS resin, a high-strength, low-density (e.g., 1.07 cm3) plastic series, instead of a metal material, the human body can be protected from the polygon mirror (110) rotating at a high speed.

[0045] The polygon mirror (110) (e.g., multiple reflective surfaces) may be subjected to chrome plating. Accordingly, good total surface reflection of the laser may occur even in a polygon mirror (110) made of ABS resin rather than metal.

[0046] The polygon mirror (110) may be manufactured to include empty space. To reduce the weight of the polygon mirror (110), it may be manufactured to include as much empty space as possible, except for the plurality of reflective surfaces and the coupling area coupled to the drive motor (120).

[0047] The rotation axis (121) is connected to the drive motor (120). The drive motor (120) rotates the polygon mirror (110) at a constant speed around the rotation axis (121).

[0048] An encoder (130) detects a change in the position of a reflective surface forming a polygon mirror (110) and outputs it as an electrical signal. The encoder (130) is fixedly formed on the polygon mirror (110) and can rotate together with the polygon mirror (110).

[0049] An encoder (130, see FIG. 5) may include a disk (131) having a plurality of slits (131a) formed therein, a light-emitting element (132), and a photo sensor (133). A light-emitting element (132), such as an LED, may be installed on the upper portion of the disk (131), and a photo sensor (133) may be installed on the lower portion of the disk (131). Alternatively, a light-emitting element, such as an LED, may be installed on the lower portion of the disk (131), and a photo sensor (133) may be installed on the upper portion of the disk (131). The photo sensor (133) may obtain a low signal when light passes through the slits (131a), and a high signal when light is blocked by the slits (131a). During one rotation (one cycle) of the polygon mirror (110), the encoder (130) can obtain as many high and low signals as the number of slits (131a) formed on the disk (131). The high and low signals obtained by the encoder (130) are transmitted to the motor control unit (140).

[0050] The motor control unit (140) compares the reference rotation period (T0) of the preset polygon mirror (110) with the real-time rotation period (T1) measured by the encoder (130) and controls the drive motor (120) so that the real-time rotation period (T1) can become the preset reference rotation period (T0).

[0051] Referring to FIG. 3, the motor control unit (140) may include a rotation period calculation module (141), a rotation period comparison module (142), and a control signal generation module (143).

[0052] The rotation period calculation module (141) calculates the real-time rotation period (T1) of the polygon mirror (110) by adding the pulse width of the high signal and the pulse width of the low signal for one rotation transmitted from the encoder (130).

[0053] The rotation period comparison module (142) compares the real-time rotation period (T1) calculated by the rotation period calculation module (141) with the preset reference rotation period (T0) to calculate the difference value.

[0054] The control signal generation module (143) uses a look-up table to generate a drive motor control signal corresponding to the difference value calculated by the rotation cycle comparison module (142). In the look-up table, the difference value between the real-time rotation cycle (T1) and the preset reference rotation cycle (T0) is classified into a specific range, and the drive motor control signal in the category to which the corresponding difference value belongs is indexed and preset.

[0055] An example of such a look-up table is shown in Fig. 4. The look-up table can be prepared statistically by repeated experiments. If the real-time rotation period (T1) is less than the preset reference rotation period (T0), the rotation speed is fast, so the control signal generation module (143) generates a drive motor control signal that gradually reduces the rotation speed of the drive motor (120). If the real-time rotation period (T1) is greater than the preset reference rotation period (T0), the rotation speed is slow, so the control signal generation module (143) generates a drive motor control signal that gradually increases the rotation speed of the drive motor (120). The control signal generation module (143) generates a drive motor control signal that allows the real-time rotation period (T1) to become the preset reference rotation period (T0) for each rotation of the polygon mirror (110).

[0056] In this way, the motor control unit (140) can maintain the rotation speed of the polygon mirror (110) constant.

[0057]

[0058] Meanwhile, a polygon mirror scanner according to an embodiment of the present invention can accurately detect the origin of a polygon mirror (110). This will be described with reference to FIGS. 5 and 6. FIG. 5 is a perspective view illustrating a polygon mirror scanner according to an embodiment of the present invention, and FIG. 6 shows output data of an encoder acquired by a photo sensor, wherein (a) is output data by a conventional encoder and (b) is output data by an encoder of the present invention.

[0059] Referring to FIG. 5, the encoder (130) is for detecting a change in the position of a reflective surface forming a polygon mirror (110) and outputting it as an electrical signal, and is formed to be fixed to the polygon mirror (110) and can rotate together with the polygon mirror (110).

[0060] The encoder (130) may include a disk (131) having a plurality of slits (131a) formed thereon, a light emitting element (132), and a photo sensor (133). The photo sensor (133) may obtain a low signal when light passes through the slits (131a), and a high signal when light is blocked by the slits (131a). When the polygon mirror (110) rotates once (per cycle), the encoder (130) may obtain as many high and low signals as the number of slits (131a) formed on the disk (131).

[0061] However, in the conventional encoder, since the widths of the plurality of slits (131a) formed on the disk (131) are the same, the pulse width is the same in the output data of the encoder, as shown in (a) of Fig. 6. Therefore, in the conventional encoder, the origin of the encoder can be designated in the output data of the encoder only when the number of pulses is exactly counted as the number of slits (131a). Therefore, the encoder must additionally have a circuit for counting the number of pulses, which may complicate the board structure.

[0062] To solve this, in the present invention, one of the plurality of slits (131a) formed on the disk (131) is closed to become an origin slit (131b). The origin slit (131b) is called a slit, but in reality, unlike the other slits (131a), no opening is formed. Therefore, as shown in (b) of Fig. 6, the pulse width of the high signal including the origin slit (131b) becomes larger than the pulse widths of the other high signals, so that the encoder (130) can designate the origin of the encoder on the output data of the encoder with only the pulse width size. The encoder (130) can designate the falling edge of the pulse of the high signal of the origin slit (131b) as the origin.

[0063] If the origin of the polygon mirror (110) is designed to match the position corresponding to the position of the origin slit (131b) of the encoder, the origin of the polygon mirror (110) can be accurately detected even with a simple configuration.

[0064] When measuring the real-time rotation period (T1) of the polygon mirror (110) described above, the high signal pulse width and the low signal pulse width of the slit (131a) and the origin slit (131b) are added together to calculate the real-time rotation period (T1) of the polygon mirror (110).

[0065]

[0066] Furthermore, the motor control unit (140) of the present invention can also obtain the pulse width time (t1) of the origin slit (131b) and generate a driving motor control signal.

[0067] The motor control unit (140) can compare the reference pulse width time (t0) of the origin slit (131b) with the real-time pulse width time (t1) of the origin slit (131b) obtained from the encoder (130) to calculate a difference value, and generate a driving motor control signal corresponding to the calculated difference value by referring to the second look-up table. At this time, in the second look-up table, the difference value between the real-time pulse width time (t1) and the preset reference pulse width time (t0) is classified in detail by a certain range, and the driving motor control signal in the category to which the corresponding difference value belongs is indexed and preset.

[0068] The second look-up table can be prepared statistically by repeated experiments. If the real-time pulse width time (t1) is less than the preset reference pulse width time (t0), the rotation speed is fast, and therefore the motor control unit (140) (specifically, the control signal generation module (143)) generates a driving motor control signal that gradually reduces the rotation speed of the driving motor (120). If the real-time pulse width time (t1) is greater than the preset reference pulse width time (t0), the rotation speed is slow, and therefore the motor control unit (140) generates a driving motor control signal that gradually increases the rotation speed of the driving motor (120). The motor control unit (140) generates a driving motor control signal that allows the real-time pulse width time (t1) to become the preset reference pulse width time (t0) for each rotation of the polygon mirror (110).

[0069]

[0070] Furthermore, the motor control unit (140) of the present invention can determine whether an abnormality has occurred in the polygon mirror scanner (100) or the encoder (130) based on a driving motor control signal (first control signal) generated using a real-time rotation cycle (T1) and a driving motor control signal (second control signal) generated using a pulse width time (t1) of the origin slit (131b).

[0071] The motor control unit (140) can determine that the polygon mirror scanner (100) or the encoder (130) is normal if the first control signal and the second control signal match each other. The motor control unit (140) can determine that an abnormality has occurred in the polygon mirror scanner (100) or the encoder (130) if the first control signal and the second control signal do not match each other. In this case, the motor control unit (140) can generate alarm information notifying the occurrence of an abnormality and transmit the alarm information to the user terminal.

[0072]

[0073] Fig. 7 is a diagram illustrating a computing device according to an embodiment of the present invention. The computing device (TN100) of Fig. 7 may be a hardware configuration of the motor control unit (140) described herein.

[0074] In the embodiment of FIG. 7, the computing device (TN100) may include at least one processor (TN110), a transceiver (TN120), and a memory (TN130). In addition, the computing device (TN100) may further include a storage device (TN140), an input interface device (TN150), an output interface device (TN160), and the like. The components included in the computing device (TN100) may be connected by a bus (TN170) to communicate with each other.

[0075] The processor (TN110) can execute program commands stored in at least one of the memory (TN130) and the storage device (TN140). The processor (TN110) may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which methods according to embodiments of the present invention are performed. The processor (TN110) may be configured to implement procedures, functions, methods, etc. described in relation to embodiments of the present invention. The processor (TN110) may control each component of the computing device (TN100).

[0076] The memory (TN130) and the storage device (TN140) can each store various information related to the operation of the processor (TN110). The memory (TN130) and the storage device (TN140) can each be configured with at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory (TN130) can be configured with at least one of a read-only memory (ROM) and a random access memory (RAM).

[0077] The transceiver (TN120) can transmit or receive wired or wireless signals. The transceiver (TN120) can be connected to a network to perform communication.

[0078]

[0079] Meanwhile, the present invention can also be implemented as a computer program. The present invention can be implemented as a computer program stored on a computer-readable recording medium, combined with hardware.

[0080] Methods according to embodiments of the present invention may be implemented in the form of readable programs via various computer means and recorded on a computer-readable recording medium. Here, the recording medium may include program commands, data files, data structures, etc., singly or in combination.

[0081] The program commands recorded on the recording medium may be specially designed and configured for the present invention or may be known and available to those skilled in the art of computer software.

[0082] For example, recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CDROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specifically configured to store and execute program instructions such as ROMs, RAMs, and flash memories.

[0083] Examples of program instructions may include machine language, such as that produced by a compiler, as well as high-level languages ​​that can be executed by a computer using an interpreter, etc.

[0084] Such hardware devices may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

[0085]

[0086] Above, one embodiment of the present invention has been described, but a person having ordinary skill in the art will be able to modify and change the present invention in various ways by adding, changing, deleting or adding components, etc., within the scope that does not depart from the spirit of the present invention described in the claims, and this will also be considered to be included within the scope of the rights of the present invention.

Claims

1. A polygon mirror that rotates around a rotation axis and includes multiple reflective surfaces; A driving motor that rotates the polygon mirror around the rotation axis; An encoder for measuring the real-time rotation period of the above polygon mirror; A motor control unit that controls the driving motor so that the real-time rotation cycle can become the reference rotation cycle by referring to a result value obtained by comparing a preset reference rotation cycle with the real-time rotation cycle; A polygon mirror scanner, including:

2. In claim 1, the motor control unit, A rotation period calculation module that calculates the real-time rotation period by adding the pulse width of the high signal and the pulse width of the low signal transmitted from the encoder during one rotation of the polygon mirror, A rotation cycle comparison module that compares the real-time rotation cycle and the reference rotation cycle to calculate a difference value, A control signal generation module that generates a drive motor control signal corresponding to the difference value calculated from the rotation cycle comparison module by referring to the look-up table. A polygon mirror scanner, including:

3. In claim 2, A polygon mirror scanner in which the above look-up table classifies the difference between the real-time rotation cycle and the reference rotation cycle into specific ranges, and the driving motor control signal in the category to which the difference value belongs is indexed and preset.

4. In claim 3, The above control signal generation module is a polygon mirror scanner that generates the driving motor control signal for each rotation of the polygon mirror.

5. In claim 1, The above encoder includes a disk having a plurality of slits formed therein, A polygon mirror scanner, wherein the disk includes an origin slit formed by closing one of the plurality of slits.

6. In claim 5, A polygon mirror scanner that calculates the real-time rotation period by adding the high signal pulse width and the low signal pulse width of the slit and the origin slit when measuring the real-time rotation period of the polygon mirror.

7. In claim 5, A polygon mirror scanner in which the motor control unit compares the reference pulse width time of the origin slit with the real-time pulse width time of the origin slit obtained from the encoder to calculate a difference value, and generates a driving motor control signal corresponding to the calculated difference value by referring to a second look-up table.

8. A polygon mirror that rotates around a rotation axis and includes multiple reflective surfaces; A driving motor that rotates the polygon mirror around the rotation axis; An encoder comprising an origin slit formed by closing one of a plurality of slits, and obtaining a real-time pulse width time of the origin slit; A motor control unit that compares the reference pulse width time of the origin slit with the real-time pulse width time of the origin slit to calculate a difference value, and generates a driving motor control signal corresponding to the calculated difference value by referring to a second look-up table; A polygon mirror scanner, including:

9. In claim 8, A polygon mirror scanner in which the second look-up table classifies the difference between the real-time pulse width time and the reference pulse width time into specific ranges, and the driving motor control signal in the category to which the difference value belongs is indexed and preset.

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