Patent Publication Number: US-2019170542-A1

Title: Optical structure for rotation positioning

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan Patent Application Serial Number 106142281, filed on Dec. 1, 2017, the full disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Disclosure 
     This disclosure generally relates to an optical structure for positioning a rotatable device and, more particularly, to a technology of confirming a position using an optical sensor to detect reflected light coming through a through hole formed at a predetermined position on the rotatable device. 
     2. Description of the Related Art 
     Conventionally, in order to position a rotatable device, “opposite type” optical sensing mechanism is adopted in which a light source and an optical sensor are arranged at two opposite sides of the rotatable device. The light source is positioned opposite to the optical sensor, and the rotatable device is formed with an aperture for light going through. When the aperture is rotated to be between the light source and the optical sensor, the light from the light source penetrates the aperture and is sensed by the optical sensor. In this way, a position of the rotatable device is confirmed. 
     However, in this kind of mechanism, because the light source and the optical sensor are arranged at two sides of the rotatable device, the control circuits thereof also have to be laid at two sides of the rotatable device such that the manufacturing complexity and the occupied space are increased. Meanwhile, in the arrangement of the light source, the optical sensor and the rotatable device, the exact positional relationship between the three has to be considered which also increases the manufacturing complexity. 
     SUMMARY 
     The present disclosure provides an optical structure for positioning a rotatable device. It is an object of the present disclosure to arrange an optical sensor and a light source at the same side of the rotatable device. Using the geometric arrangement, the optical sensor is able to receive reflected light generated by the light source only at a predetermined positioning location. To achieve this object, the optical sensor and the light source are arranged very close to the rotatable device, and at least one through hole is formed on the rotatable device. In this way, if the through hole is not aligned with the light source, light generated by the light source is blocked by a plane opposite to the light source and the optical sensor to cause the light to be reflected immediately after being emitted such that the optical sensor is not able to detect the emitted light. 
     When the through hole is aligned with the light source, light emitted by the light source goes through the through hole and is reflected by another object behind the through hole. In this case, as the light propagates through a longer path, reflected light has a larger emission range and is detectable by the optical sensor. It should be noted that the light source and the optical sensor are arranged symmetrical to a reflection point (e.g., the optical sensor being arranged at a main reflection path) or not. When the emitted light impinges on the object, in addition to the symmetrical reflected light (e.g., light on the main reflection path), other scattered light (e.g., light not on the main reflection path) is also generated. Because the scattered light has a wider reflected direction, the optical sensor still detects reflected light even though the optical sensor and the light source are not arranged symmetrically corresponding to the reflection point. 
     The present disclosure provides an optical structure for rotation positioning. The optical structure includes at least one rotatable element, a reflection object, a light source and an optical sensor. Each of the at least one rotatable element has at least one through hole. The reflection object is arranged at one side of the at least one rotatable element. The light source is arranged at the other side of the at least one rotatable element, and configured to emit light toward the at least one rotatable element, wherein when the at least one rotatable element is rotated to a predetermined position, emitted light of the light source goes through the at least one through hole and projects on the reflection object. The optical sensor is arranged at the same side of the at least one rotatable element with the light source, and configured to receive reflected light from the reflection object. 
     The present disclosure further provides an optical structure for rotation positioning. The optical structure includes a rotatable element, a reflection object and a control chip. The rotatable element has at least one through hole. The reflection object is arranged at one side of the rotatable element. The control chip is arranged at the other side of the rotatable element and includes a light source, an optical sensor and a digital signal processor. The light source is configured to emit light toward the rotatable element, wherein when the rotatable element is rotated to a predetermined position, emitted light of the light source goes through the at least one through hole and projects on the reflection object. The optical sensor is configured to convert reflected light from the reflection object to electrical signals. The digital signal processor is configured to position the rotatable element according to the electrical signals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, advantages, and novel features of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
         FIG. 1  is a cross sectional view of an optical structure according to a first embodiment of the present disclosure. 
         FIG. 2  is a second embodiment of the present disclosure which has multiple rotatable elements. 
         FIG. 3  is a third embodiment of the present disclosure, in which multiple through holes are formed at different positions of a rotatable element. 
         FIG. 4  is a cross sectional view of an optical structure according to a fourth embodiment of the present disclosure. 
         FIG. 5  is a cross sectional view of an optical structure according to a fifth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT 
     It should be noted that, wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     Referring to  FIG. 1 , it is a cross sectional view of a first embodiment of the present disclosure. In  FIG. 1 , the rotatable device is shown to have at least one plane, e.g., a rotatable plane  107 . At least one through hole (e.g., one through hole  101  being shown in  FIG. 1 ) is formed on the rotatable plane  107  to allow light emitted by a light source  103  to go through. The emitted light illuminates an object  111  (preferable a reflection object) at the other side of the rotatable plane  107  and reflected light is generated. The optical sensor  105  detects the reflected light and generates electrical signals Se by optical sensing. The electrical signals Se are used to indicate whether the rotatable plane  107  is rotated to a predetermined position. The rotatable plane  107  rotates by a shaft  109 . 
     In a non-limiting embodiment, at least one of the rotatable plane  107  and the object  111  is a gear, and the shaft  109  is a gear shaft. The shaft  109  is driven by a motor to rotate at least one of the rotatable plane  107  and the object  111  at a predetermined rotating speed. 
     In this embodiment, a diameter of the through hole  101  is not a limitation of the present disclosure. As long as the light can go through, even a tiny hole is adaptable to the present disclosure. In order to cause the optical sensor  105  not to detect reflected light when the thorough hole  101  is not aligned with the light source  103 , a space between the rotatable plane  107  and the light source  103  should be very small, preferably smaller than 0.2 mm to block the propagation of light therebetween. In this way, if the through hole  101  does not pass the above space of the light source  103 , the reflected light is not detected by the optical sensor  105 . 
     It should be mentioned that said through hole  101  being aligned with the light source  103  (i.e. rotating to a predetermined position) is not limited to that the through hole  101  is right above the light source  103 . According to an emission direction of the light source  103 , the through hole  101  is arranged to deviate toward the optical sensor  105 . More specifically, in the present disclosure, when the rotatable plane  107  is rotated to the predetermined position, the at least one through hole is right above the light source  103 , or between upper space of the light source  103  and the optical sensor  105 . 
     For example,  FIG. 1  shows that the optical sensor  105  is arranged outside an edge of the rotatable plane  107 , and thus the optical sensor  105  does not receive reflected light (referred to the light after being reflected by the object  111 ) from the object  111  via the at least one through hole  101 . In an embodiment having a larger through hole that exposes a part of the light source  103  and a part of the optical sensor  105 , the optical sensor  105  is arranged under the rotatable plane  107 . The positional relationship between the light source  103 , the optical sensor  105  and the object  111  is arranged flexibly as long as the optical sensor  105  detects light reflected by the object  111 . 
       FIG. 2  is a second embodiment of the present disclosure, and a difference thereof from the first embodiment is that multiple rotatable planes  207   a ,  207   b  and  207   c  are shown in  FIG. 2 , and at least on through hole is formed on each rotatable plane ( FIG. 2  showing one through hole on each rotatable plane). In this embodiment, light emitted by the light source  203  penetrates the through holes  201   a ,  201   b  and  201   c  when these through holes are aligned to allow the optical sensor  205  to detect the reflected light. That is, the rotatable planes  207   a ,  207   b  and  207   c  are all rotated to a predetermined position and the positioning is accomplished. In this embodiment, as long as the multiple through holes have an overlapped area, the light source can go through, and this is one benefit of the optical detection. As the through hole for the light penetration does not have the volume limitation, high accuracy is not extremely required in manufacturing these through holes. 
     Furthermore, the rotatable plane  207   a  is the first plane to limit the propagation of emitted light, and thus the rotatable plane  207   a  should be arranged very close to the light source  203  as mentioned in the first embodiment. 
     In a non-limiting embodiment, the rotatable planes  207   a ,  207   b  and  207   c  have different sizes, radiuses and/or rotating speeds. Every a predetermined time interval, the through holes  201   a ,  201   b  and  201   c  overlap once to allow the light emitted by the light source  203  to go through every through hole  201   a ,  201   b  and  201   c  to be reflected by the above object. 
     In a non-limiting embodiment, the optical sensor  205  has a sensing array. When the light emitted by the light source  203  goes through the through hole  201   a  but is unable to pass the through hole  201   b  and is reflected by the rotatable plane  207   b  (e.g., a lower surface thereof), a light spot is formed at a first location of the sensing array. When the light emitted by the light source  203  goes through the through holes  201   a  and  201   b  but is unable to pass the through hole  201   c  and is reflected by the rotatable plane  207   c  (e.g., a lower surface thereof), a light spot is formed at a second location (different from the first location) of the sensing array. When the light emitted by the light source  203  goes through the through holes  201   a ,  201   b  and  201   c  and is reflected by the above object, a light spot is formed at a third location (different from the first and second locations) of the sensing array. Accordingly, a processing unit (e.g., a digital signal processor) identifies positions of the rotatable planes  207   a ,  207   b  and  207   c  according to a location of the light spot in the image frame outputted by the sensing array. 
       FIG. 3  is a third embodiment of the present disclosure, and a difference thereof from the first embodiment is that multiple through holes  301   a ,  301   b  and  301   c  arranged with a predetermined relative distance from one another are formed at different positions on a same rotatable plane  307 . The space between the multiple through holes is used to locate different positions of the rotatable plane  307 . For example in this embodiment, the through hole  301   b  is very close to the through hole  301   c . Accordingly, when the rotatable plane  307  is rotating, and if the optical sensor  305  successively receives reflected light having a magnitude larger than a threshold twice (within a predetermined time interval), it means that the rotatable plane  307  is rotated to a position of the through hole  301   b  or  301   c  depending on the rotating direction. However, when the rotatable plane  307  is rotating, and if the optical sensor  305  receives reflected light having a magnitude larger than a threshold once, it means that the rotatable plane  307  is rotated to a position of the through hole  301   a.    
       FIG. 4  is a cross sectional view of a fourth embodiment of the present disclosure, which shows two through holes  401   a  and  401   b  are formed on one rotatable plane  407 . The first through hole  401   a  allows the emitted light of the light source  403  to go through to reach the above object  111 . The second through hole  401   b  allows the reflected light to go through to impinge on the optical sensor  405 . The first through hole  401   a  and the second through hole  401   b  have identical or different sizes and/or shapes without particular limitations as long as when the light source  403  and the optical sensor  405  are aligned with the first and second through holes  401   a  and  401   b  respectively, the emitted light from the light source  403  is reflected by the object  111  and then received by the optical sensor  405 . As mentioned above, the rotatable plane  407  is very close to the light source  403  and the optical sensor  405 . 
       FIG. 5  is a cross sectional view of a fifth embodiment of the present disclosure, which shows that a rotatable plane  507  has a single large through hole  501  to allow the emitted light of the light source  503  and the reflected light from the above object  111  to go through the same through hole  501 . As mentioned above, the rotatable plane  507  is very close to the light source  503  and the optical sensor  505 . 
     As mentioned above, according to the spatial arrangement of the light source  503 , the through hole  501  and the optical sensor  505 , the through hole  501  is located above a part or the whole of the light source  503  and the optical sensor  505 , or located between upper space of the light source  503  and the optical sensor  505  when the rotatable plane  507  is rotated to the predetermined position. 
     In this embodiment, in order to prevent the emitted light of the light source  503  from being directly received by the optical sensor  505 , preferably an opaque light blocking wall  504  is disposed between the light source  503  and the optical sensor  505 . 
     In a non-limiting embodiment, the above light sources  103 - 503  are light emitting diodes or laser diodes that emit light of an identifiable spectrum, e.g., infrared light and/or red light. The optical sensors  105 - 505  are CMOS image sensors, photodiodes or other sensors for sensing light energy. The light sources  103 - 503  and optical sensors  105 - 505  are integrated in a control chip with a digital signal processor  108  (referring to  FIG. 1 ), and the control chip and the object  111  are arranged at different sides of a rotatable plane, wherein the digital signal processor  108  is used to control the light sources  103 - 503  to emit light and control the optical sensors  105 - 505  to detect light, which is converted to electrical signals, corresponding to light emission of the light sources  103 - 503 . 
     In other words, in the present disclosure the reflection object is arranged at one side of at least one rotatable plane (as shown in  FIGS. 1-5 ), and the light source and optical sensor are located at the other side of the at least one rotatable plane. The light source is used to emit light toward the at least one rotatable plane. When the at least one rotatable plane is rotated to a predetermined position, emitted light of the light source goes through at least one through hole to project on the reflection object. The optical sensor is used to receive reflected light from the reflection object. 
     In a non-limiting embodiment, the digital signal processor identifying whether the alignment is fulfilled is to, for example, calculate a magnitude of the electrical signal and compares the calculated amplitude with a threshold. When the amplitude exceeds the threshold, the through hole of the rotatable plane  107 - 507  is identified to be aligned with the light source and/or the optical sensor which is referred as positioning the rotatable plane herein. For example, in  FIGS. 1 and 2 , the digital signal processor  108  compares the amplitude of the electrical signals with a threshold to position the rotatable plane  107 ,  207   a - 207   c . For example in  FIG. 3 , the digital signal processor  108  positions the rotatable plane  307  according to a number of times of the amplitude variation of the electrical signals. As mentioned above, the amplitude is larger than the threshold for once when the rotation position is corresponded to the through hole  301   a , and the amplitude is larger than the threshold for twice within a predetermined time interval when the rotation position is corresponded to the through holes  301   b  and  301   c.    
     In a non-limiting embodiment, the digital signal processor  108  further controls the light source  103 - 503  to turn on and turn off, and controls the optical sensor  105 - 505  to acquire a bright image when the light source is turned on and acquire a dark image when the light source is turned off. Then the digital signal processor  108  calculates a differential image between the bright image and the dark image, and identifies whether the rotatable plane is rotated to the predetermined position according to a comparison result by comparing an amplitude of the differential image with the threshold to further improve the detection accuracy. 
     In the above embodiments, to specify the light of the light source, a filter is formed on the optical sensor or in the through hole such that only the light of a specific wavelength is detectable thereby improving the sensing efficiency. 
     The present disclosure is adaptable to set time of a watch (e.g., a satellite watch or GPS watch). When the watch receives a correct time signal (e.g., the watch having a communication interface for communicating with a station), hour and minute hands of the watch are moved to correct positions by using the present disclosure to accomplish the time setting. In addition, the present disclosure is further adaptable to an instrument panel using a spinning indicator or setting a gear to an original position, e.g., the panel for indicating flow rate and used electricity or the conveyor system for conveying goods by rotating gears. 
     Referring to  FIG. 1  again, for example when the watch, which includes the optical structure in  FIGS. 1-5 , receives the correct time signal, the shaft  109  is controlled by a motor (not shown) to rotate the rotatable plane  107  to cause the through hole  101  to be aligned with the light source  103 , i.e., controlling the rotatable plane  107  to be rotated to a calibration position according to the correct time signal. In some conditions, the rotatable plane  107  is not rotated to a correct calibration positon (i.e. the predetermined position) due to some problems when the watch receives the correct time signal. In this case, the digital signal processor  107  is further used to identify whether the amplitude of the electrical signal exceeds the threshold when the rotatable plane  107  is rotated to the calibration position in order to identify whether the calibration position is identical to the predetermined position or not. 
     When the amplitude of the electrical signal does not exceed the threshold, the control chip continuously rotates the rotatable plane  107  and counts a time interval to a next time that the through hole  101  is aligned with the light source  103  (e.g., using a counter to count a time interval before the amplitude of the electrical signal exceeding the threshold next time) so as to obtain a deviation angle of the rotatable plane  107 . The deviation angle is stored in a memory (also in the control chip) as a calibration amount. In this way, when the watch receives the correct time signal again, the motor rotates the rotatable plane  107  to the calibration position plus or minus the calibration amount to cause the through hole  101  of the rotatable plane  107  to be correctly aligned with the light source  103 . The process of storing the calibration amount is implemented by software and/or hardware codes in a calibration mode, which is entered by pressing a button or via a selection menu by a user. 
     In a non-limiting embodiment, a surface of the rotatable plane  107  facing the light source  103  and the optical component  105  is covered with light absorbing material such that when the through hole  101  is not aligned with the light source  103 , the reflection is reduced to lower the noise. 
     In a non-limiting embodiment, a surface of the object  111  facing the light source  103  and the optical sensor  105  is covered with light reflective material (especially for reflecting the emitted light of the light source  103 ) to improve the reflection efficiency. 
     In a non-limiting embodiment, a light reflecting structure (e.g., a mirror) for directing reflected light to a specific direction (e.g., a direction to the optical sensor  105 ) is arranged on a surface of the object  111  facing the light source  103  and the optical sensor  105  so as to arrange the relative position of the light source  103  and the optical sensor  105  according to different requirements. 
     In a non-limiting embodiment, positions of the light source  103  and the optical sensor  105  in  FIG. 1  are exchanged such that the optical sensor  105  receives reflected light from the object  111  only when the through hole  101  is aligned with the optical sensor  105 . In this embodiment, the light source  103  emits light continuously, and preferably an upper surface of the rotatable plane  107  is covered with light absorbing material such that when the through hole  101  is not aligned with the optical sensor  105 , the light emitted by the light source  103  is absorbed to reduce the interference. 
     In a non-limiting embodiment, the optical structure in  FIG. 1  includes multiple light sources each being associated with a through hole, and each through hole has a corresponding optical sensor. The digital signal processor identifies the rotation position (or rotation angle) according to the sensing results of different optical sensors. 
     It should be mentioned that every non-limiting embodiment illustrated above using  FIG. 1  as an example is also adaptable to  FIGS. 2-5 . 
     In addition, although the rotatable plane mentioned above is described by a plane, the present disclosure is not limited thereto. The rotatable plane is a suitable rotatable element (e.g., a gear), a part surface of which is a flat surface formed with other structures protruding or recessing from the flat surface as long as the structures do not influence the rotation thereof. 
     As mentioned above, the conventional positioning optical structure has a problem of high manufacturing complexity. Accordingly, the present further provides an optical structure for rotation positioning (e.g.,  FIGS. 1-5 ) in which a control chip, which includes a light source and an optical sensor, is arranged at a single side of the rotatable element so as to reduce the manufacturing complexity and the occupied space. 
     Although the disclosure has been explained in relation to its preferred embodiment, it is not used to limit the disclosure. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the disclosure as hereinafter claimed.