Abstract:
A laser projector includes a laser source module for generating an input light beam, a deflection component that deflects the input light beam to mutually orthogonal first and second scanning directions to form a scanning light beam, a first prism and a second prism both used for allowing the scanning light beam to pass therethrough for performing two-dimensional scanning on an imaging surface and formation of an image. By adjustment of the angle between the first prism and the second prism, various conditions are satisfied to achieve image distortion correction and image lift.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a laser projector, especially to a laser projector in which a first prism and a second prism are disposed on a scanning light path between a deflection component (microelectromechanical systems (MEMS) two-dimensional scanning mirror) and an imaging surface. An angle between the two prisms satisfies specific conditions. Thereby an image scanned and projected on the imaging surface achieves image distortion correction and image lift. 
         [0002]    In a two-dimensional scanning projector with a single light spot, an incident light beam is off-axially delivered to a MEMS mirror for scanning and formation of an emitted light beam. Thus there are problems of image distortion and image lift. The image lift means the projected image needs to be moved upward. When the projector is placed on a desk or on a floor and in use, the lower half of the projected image is displayed on the desk or on the floor. The projected image is unable to be displayed on the whole imaging surface (such as screen) and this is inconvenient for users. 
         [0003]    While a light spot is used together with a two-dimensional deflection component for scanning and projection, distortion on the imaging surface caused reduced quality of the image. The image distortion is caused by non-linearity between the scanning angle of deflection member and the distance to the imaging surface scanned, or oblique projection for image lift. In prior arts including U.S. Pat. No. 7,839,552(CN100468123C), U.S. Pat. No. 7,957,047, U.S. Pat. No. 7,38,5745, U.S. Pat. No. 7,256,917, U.S. Pat. No. 6,859,329, US2011/0141441, etc, a plurality of aspheric components or optical components with aspheric reflecting surfaces at fixed positions are used for correction of image distortion. However, aspheric components are difficult both in manufacturing and examination. Thus the cost is quite high. Moreover, the components should be assembled carefully in order to maintain respective positions of the components. The errors in the positions affect correction effect of the image distortion and change the size of the laser spot along the distance. Thus the assembly is quite difficult. As to U.S. Pat. No. 7,839,552(CN100468123C), the optical components used (such as aspheric components or aspheric reflecting surfaces) are only for image distortion correction. Yet the present invention provides a laser projector in which a first prism and a second prism arranged in turn at a light path from a MEMS mirror to an imaging surface, and an angle between the two prisms satisfies specific conditions. Thus the scanned and projected image on the imaging surface are corrected and lifted up. 
         [0004]    Refer to U.S. Pat. No. 7,878,658, a prism with multiple surfaces is used to guide light paths and correct image distortion. The prism includes an incident surfaces, an exit surface and internal surface for reflecting light beam. A light beam is incident into the prism through a first incident surface, reflected multiple times in the prism, and emitted out from the first surface at a designed angle. Then the light beam is incident into a deflection component, reflected and scanned and then entered the prism again through a second incident surface (original first exit surface). Next the light beam is emitted out from a second exit surface to form an image on an imaging surface. The second incident surface and the second exit surface are arranged in a non-parallel manner and such design is used for correction of image distortion. Moreover, the light path is guided by respective total reflecting inclined surfaces. However, the shape of the prism is quite complicated. The complicated processing of the prism results in high cost. Furthermore, the prism used is only for correction of image distortion and not related to image lift while the present invention includes a first prism and a second prism arranged in turn at a light path from a MEMS mirror to an imaging surface. An angle between the two prisms satisfies specific conditions so as to achieve both correction and lift-up of the image scanned and projected on the imaging surface. 
         [0005]    Refer to U.S. Pat. No. 8,107,147 (W02010/111216, CN102365573A) and US2010/0060863 (WO2010/030467, CN102150070A), both use mirrors for reducing image distortion. In U.S. Pat. No. 8,107,147, two scan mirrors are used for two dimensional scanning to generate a two dimensional image. A fold mirror for reflection is positioned on an output optic or combined with a scanning mirror to be formed on a common substrate. The output optic may be utilized to reduce or increase an amount of distortion in an image, please refer to  FIG. 7  to  FIG. 9  and description related to the output optic  710 . Although the output optic  710  in some embodiment is a wedge optic that alters the output image, the output optic  710  can still be utilized to reduce or eliminate distortion an image generated, without the function of image lift. As to US2010/0060863, at least one wedge optic is disposed after the MEMS scanner. Refer to U.S. Pat. No. 8,107,147 (WO2010/111216, CN102365573A) and US2010/0060863 (WO2010/030467, CN102150070A), both use mirrors for reducing image distortion. In U.S. Pat. No. 8,107,147, two scan mirrors are used for two dimensional scanning to generate a two dimensional image. A fold mirror for reflection is positioned on an output optic or combined with a scanning mirror to be formed on a common substrate. The output optic may be utilized to reduce or increase an amount of distortion in an image, please refer to  FIG. 7  to  FIG. 9  and description related to the output optic  710 . Although the output optic  710  in some embodiment is a wedge optic that alters the output image, the output optic  710  can still be utilized to reduce or eliminate distortion an image generated, without the function of image lift. As to US2010/0060863, at least one wedge optic is disposed after the MEMS scanner. Although two or more wedge optics are used in combination (refer to  FIG. 2  and wedge optics  210 ,  218 ), they are utilized to correct and/or adjust chromatic aberration. The technique revealed in US2010/0060863 is unable to correct image distortion and lift the image at the same time. As to the present invention, two prisms are disposed in turn on a light path from a MEMS mirror to an imaging surface and an angle between the two prisms satisfies specific conditions. Thus both correction of image distortion and image lift are provided. 
         [0006]    Refer to U.S. Pat. No. 8,159,735 (WO2010/021331, CN102132191B), a deflection apparatus is arranged to incline obliquely to perform an oblique projection onto a screen. The light beam is deflected by the deflection apparatus to be scanned and projected onto the screen obliquely. Thus the image can be displayed over the entire screen even the projector is placed on the desk or on the floor. However, the distortion of the image (such as trapezoidal distortion) is reduced or eliminated without provision of a projection optical system. No prism is disposed between the deflection component/apparatus (such as MEMS mirror) and the imaging surface (such as screen). The correction of the image distortion is by certain conditions of the direction of the incident light beam into the deflection apparatus. For example, as described in claim  1  and claim  2 , a normal line of the reflection member of the deflection apparatus in the screen-center display state is tilted toward the negative direction side in the second scanning direction with respect to a normal line of the projection surface. A conditional expression “0.25&lt;θmems/θin&lt;0.75”in claim  3  is fulfilled. θmems is an angle formed by the normal line of the reflection member of the deflection apparatus in the screen-center display state and a normal line of the projection surface in the second scanning direction while θin is an incidence angle in the second scanning direction when a principal ray from the laser light source is incident on the reflection member of the deflection apparatus in the screen-center display state. Thus the technique revealed in the U.S. Pat. No. 8,159,735 requires no projection optical system while reducing distortion. In contrast, the present invention includes two prisms disposed between the deflection component/apparatus (such as MEMS mirror) and the imaging surface (such as screen) and the angle between the two prisms satisfies specific conditions for correction of image distortion and image lift. Thus the technique and features revealed in U.S. Pat. No. 8,159,735 are different from those of the present invention. 
         [0007]    As to the disadvantages of the prior arts mentioned above, please refer to the following table. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 disadvantages 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 no 
                 limited 
               
               
                   
                   
                 low 
                   
                 reduced 
                   
                 complicated 
                 image 
                 effect 
               
               
                   
                   
                 component 
                 high 
                 assembly 
                 large 
                 drive 
                 lift 
                 on 
               
               
                 prior arts 
                 difficulty in component 
                 tolerance 
                 cost 
                 tolerance 
                 volume 
                 control 
                 control 
                 distortion 
               
               
                   
               
               
                 U.S. Pat. No. 7,256,917 
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                 U.S. Pat. No. 7,385,745 
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                 U.S. Pat. No. 7,839,552 
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                 U.S. Pat. No. 7,878,658 
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                 U.S. Pat. No. 7,957,047 
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                 U.S. Pat. No. 8,107,147 
                   
                   
                   
                   
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                 U.S. Pat. No. 8,159,735 
                   
                   
                   
                   
                   
                   
                   
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                 U.S. Pat. No. 6,859,329 
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                 US 
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                 2004/0141221 
               
               
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                 2009/0251668 
               
               
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                 2010/0060863 
               
               
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                 2010/0253991 
               
               
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                 2011/0141441 
               
               
                   
               
             
          
         
       
     
       SUMMARY OF THE INVENTION 
       [0008]    Therefore it is a primary object of the present invention to provide a laser projector that solves not only technical problems mentioned above, but also achieves image distortion correction and image lift. The laser projector includes a laser source module, a deflection component, a first prism, and a second prism. The laser source module is used for generating an input light beam that is fed to a reflecting mirror of the deflection component (such as MEMS two-dimensional scanning mirror). The deflection component (MEMS two-dimensional scanning mirror) deflects the input light beam from the laser source toward a first scanning direction (fast axis) and a second scanning direction (slow axis). The first scanning direction and the second scanning direction are mutually orthogonal to each other. The first prism allows a scanning light beam from the deflection component (MEMS two-dimensional scanning mirror) passed through an incident surface of the first prism and the first prism to be out from an exit surface of the first prism while the second prism allows the scanning light beam emitted from the exit surface of the first prism passed through an incident surface of the second prism and the second prism to be emitted out from an exit surface of the second prism. Then an image is formed by two-dimensional scanning of the scanning light beam on an imaging surface. The projector achieves image distortion correction and image lift by setting the angle between the first prism and the second prism to satisfy specific conditions. 
         [0009]    In order to achieve the above object, a laser projector of the present invention includes a laser source, a deflection component, a first prism, and a second prism. The laser source generates an input light beam for scanning and the input light beam is fed to a reflecting mirror of the deflection component (MEMS two-dimensional scanning mirror). The deflection component (MEMS two-dimensional scanning mirror) deflects the input light beam from the laser source to a first scanning direction and a second scanning direction, both are orthogonal to each other. The scanning speed in the first scanning direction is higher than that of the second scanning direction. The first prism consists of an incident surface and an exit surface. The incident surface and the exit surface are disposed in a non-parallel manner. The scanning light beam from the deflection component (MEMS two-dimensional scanning mirror) is passed through the incident surface of the first prism and the first prism to be emitted out from the exit surface of the first prism. The second prism consists of an incident surface and an exit surface. The incident surface and the exit surface are arranged in a non-parallel manner. The scanning light beam from the exit surface of the first prism is passed through the incident surface of the second prism and the second prism to be emitted out from the exit surface of the second prism. Then the scanning light beam performs two-dimensional scanning on an imaging surface to form an image on the imaging surface. The extended direction of an angle between the exit surface and the incident surface of the first prism, and the extended direction of an angle between the exit surface and the incident surface of the second prism are opposite to each other. The exit surface of the first prism, the incident surface of the first prism, the exit surface of the second prism and the incident surface of the second prism are arranged in a non-parallel manner. The laser projector satisfies the following equations (1) and (2). 
         [0000]      0.1&lt;θmems/θin&lt;0.4   (1)
 
         [0000]      θsh&gt;θsc&gt;θs1&gt;0° or θsh&lt;θsc&lt;θs1&lt;0°  (2)
 
         [0000]    wherein θmems is the angle between the surface normal of the mirror and the surface normal of the imaging surface formed in the second scanning direction when the deflection component (MEMS two-dimensional scanning mirror) is at the initial state;
   θin is an incident angle of the input light beam in the second scanning direction when the input light beam from the light source is incident into the mirror and the deflection component (MEMS two-dimensional scanning mirror) is at the initial state;   θsh is the angle between the scanning light beam and the surface normal of the imaging surface in the second scanning direction with the larger absolute value under the condition that the deflection angle θs2 of the deflection component (MEMS two-dimensional scanning mirror) in the second scanning direction is maximum;   θsc is the angle between the scanning light beam and the surface normal of the imaging surface in the second scanning direction when the deflection component (MEMS two-dimensional scanning mirror) is at the initial state (the deflection angle θs2 is zero);   θs1 is the angle between the scanning light beam and the surface normal of the imaging surface in the second scanning direction with the smaller absolute value under the condition that the deflection angle θs2 of the deflection component (MEMS two-dimensional scanning mirror) in the second scanning direction is maximum.   
 
         [0014]    The input light beam is fed to the deflection component (MEMS two-dimensional scanning mirror) by different light paths. The light path is determined according to the position of the laser source in relative to the first and the second prisms in the laser projector. The present invention includes, but not limited to three light paths. When the laser source is arranged at the first position, the input light beam is directly fed to the MEMS two-dimensional scanning mirror to form the scanning light beam. The input light beam is first passed through the first prism and then fed to the MEMS two-dimensional scanning mirror) when the laser source is arranged at the second position. At last, the input light beam is passed through the second prism, the first prism in turn, and then fed to the MEMS two-dimensional scanning mirror when the laser source is arranged at the third position. 
         [0015]    The laser projector further satisfies following equations. 
         [0000]      20°&lt;θp1&lt;37°;
 
         [0000]      7°&lt;θp2&lt;24°;
 
         [0000]      θs1&lt;16°;
 
         [0000]      θs2&lt;9°;
 
         [0000]    wherein θp1 is an angle between the exit surface and the incident surface of the first prism; θp2 is an angle between the exit surface and the incident surface of the second prism; θs1 is an deflection angle of the MEMS two-dimensional scanning mirror) in the first scanning direction; θs2 is a deflection angle of the MEMS two-dimensional scanning mirror in the second scanning direction. 
         [0016]    The laser projector further satisfies the following equations. 
         [0000]      0.1&lt;θmems/θin&lt;0.4;
 
         [0000]      20°&lt;θp1&lt;37°;
 
         [0000]      7°&lt;θp2&lt;24°;
 
         [0000]      θs1&lt;16°;
 
         [0000]      θs2&lt;9°;
 
         [0000]    wherein θp1 is an angle between the exit surface and the incident surface of the first prism; θp2 is an angle between the exit surface and the incident surface of the second prism; θs1 is an deflection angle of the MEMS two-dimensional scanning mirror) in the first scanning direction; θs2 is a deflection angle of the MEMS two-dimensional scanning mirror in the second scanning direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a block diagram showing system structure of an embodiment of a laser projector according to the present invention; 
           [0018]      FIG. 2  is a schematic drawing showing a side view along Y-axis (slow-axis scanning direction) of an embodiment (with a laser source disposed on the first position) according to the present invention; 
           [0019]      FIG. 3  is a schematic drawing showing a top view along X-axis (fast-axis scanning direction) of the embodiment in  FIG. 2  according to the present invention; 
           [0020]      FIG. 4  is a schematic drawing showing a side view of the embodiment in  FIG. 2  with related parameters according to the present invention; 
           [0021]      FIG. 5  is a schematic drawing showing a partial side view of an embodiment with related parameters according to the present invention; 
           [0022]      FIG. 6  is a schematic drawing showing a side view another embodiment (a laser source is disposed on a second position) with related parameters according to the present invention; 
           [0023]      FIG. 7  is a schematic drawing showing a side view a further embodiment (a laser source is disposed on a third position) with related parameters according to the present invention; 
           [0024]      FIG. 8  is a schematic drawing showing image distortion on an imaging surface of an embodiment with related parameters according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Refer to  FIG. 1 ,  FIG. 2  and  FIG. 3 , a block diagram, a side view (Y axis-slow axis scanning direction) and a top view (X axis-fast axis scanning direction) showing system structure of a laser projector are disclosed. A laser projector of the present invention includes a laser source (module)  101 , a deflection component (MEMS two-dimensional scanning mirror)  102 , a first prism  103  and a second prism  104 . The deflection component (MEMS two-dimensional scanning mirror)  102 , the first prism  103  and the second prism  104  that form a scanning projection system are features of the present invention. 
         [0026]    The laser source (module)  101  is used to generate an input light beam  201  that is fed to a reflecting mirror of the deflection component (MEMS two-dimensional scanning mirror)  102 . The deflection component (MEMS two-dimensional scanning mirror)  102  deflects the input light beam  201  from the laser source (module)  101  toward a first scanning direction (fast-axis) (as the X-axis shown in  FIG. 3 ) and a second scanning direction (slow-axis) (as the Y-axis shown in  FIG. 2 . The first scanning direction and the second scanning direction are mutually orthogonal to each other. 
         [0027]    A scanning light beam  202  from the deflection component (MEMS two-dimensional scanning mirror)  102  passes through an incident surface  103   a  and the first prism  103  to be out from an exit surface  103   b.    
         [0028]    An emitted scanning light beam  203  from the exit surface  103   b  of the first prism  103  passes through an incident surface  104   a  and the second prism  104  to be emitted from an exit surface  104   b.  Then a scanning light beam  204  from the exit surface  104   b  is used to perform a two-dimensional scanning on an imaging surface  105  and get an image ( 105 ). That means the scanned image falls on the imaging surface  105 . As shown in  FIG. 1 ,  FIG. 2  and  FIG. 3 , the deflection component (MEMS two-dimensional scanning mirror)  102  makes the scanning light beam  204  perform two-dimensional scanning along the first scanning direction (fast axis), as the X axis shown in  FIG. 3  and the second scanning direction (slow axis), as the Y axis shown in  FIG. 2  to form the image ( 105 ). The first scanning direction and the second scanning direction are mutually orthogonal to each other. The scanning axis with a larger scanning angle is the fast axis, as the X axis shown in  FIG. 3  while the scanning axis with a smaller scanning angle is the slow axis, as the Y axis shown in  FIG. 2 . In this embodiment the input light beam  201  from the laser source (module)  101  is incident (delivered) into the deflection component (MEMS two-dimensional scanning mirror)  102  along the slow-axis scanning direction, as shown in  FIG. 2   
         [0029]    Moreover, the laser source  101  in the laser projector can be disposed on the first position (as shown in  FIG. 4 ), the second position (as shown in  FIG. 6 ) and the third position (as shown in  FIG. 7 ), but not limited. Thus the input light beam  201  is fed to the deflection component (MEMS two-dimensional scanning mirror)  102  by three different light paths. 
         [0030]    The first light path: When the laser source  101  is arranged at the first position, the input light beam  201  is directly fed to the deflection component (MEMS two-dimensional scanning mirror)  102 , as shown in  FIG. 2  and  FIG. 4 . The input light beam  201  is moved along the second (slow axis) scanning direction and incident into the reflecting mirror of the deflection component (MEMS two-dimensional scanning mirror)  102  to form the scanning light beam  202 . Then the scanning light beam  202  out of the reflecting mirror is incident into the first prism  103  and the second prism  104  in turn. 
         [0031]    The second light path: Refer to  FIG. 6 , the input light beam  201  is first passed through the first prism  103  and then fed to the deflection component (MEMS two-dimensional scanning mirror)  102  when the laser source  101  is arranged at the second position. The input light beam  201  is incident into the first prism  103  along the second (slow axis) scanning direction, out of the first prism  103  and incident into the reflecting mirror of the deflection component (MEMS two-dimensional scanning mirror)  102  to form the scanning light beam  202  for scanning. Then the scanning light beam  202  out of the reflecting mirror ( 102 ) is incident into the first prism  103  and the second prism  104  in turn. 
         [0032]    The third light path: Refer to  FIG. 7 , the input light beam  201  is passed through the second prism  104 , the first prism  103  in turn, and then fed to the deflection component (MEMS two-dimensional scanning mirror)  102  when the laser source  101  is arranged at the third position. The input light beam  201  is incident into the second prism  104 , the first prism  103  in turn along the second (slow axis) scanning direction, out of the first prism  103  and incident into the reflecting mirror of the deflection component (MEMS two-dimensional scanning mirror)  102  to form the scanning light beam  202  for scanning. Then the scanning light beam  202  out of the reflecting mirror ( 102 ) is incident into the first prism  103  and the second prism  104  in turn. 
         [0033]    As shown in  FIG. 2  and  FIG. 6 , the angle between the first prism  103  and the second prism  104  satisfies the following condition: the extended direction of an angle θp1 formed between the exit surface  103   b  and the incident surface  103   a  of the first prism  103  and the extended direction of an angle θp2 formed between the exit surface  104   b  and the incident surface  104   a  of the second prism  104  are opposite to each other. Moreover, the exit surface  103   b  of the first prism  103 , the incident surface  103   a  of the first prism  103 , the exit surface  104   b  of the second prism  104  and the incident surface  104   a  of the second prism  104  are arranged in a non-parallel manner. 
         [0034]    Furthermore, the parameters related to the present invention are defined first in order to explain technical features (or the components) of the present invention. Refer to  FIG. 4  and  FIG. 5 , a side view and a partial side view of an embodiment of the laser projector (the same as the embodiment in  FIG. 2 ) with related parameters are revealed. The input light beam  201  is fed to the reflecting mirror of the deflection component (MEMS two-dimensional scanning mirror)  102 . An angle formed between the input light beam  201  and a surface normal  301  of the mirror is θin, as shown in  FIG. 5 . The mirror is the reflecting mirror of the deflection component (MEMS two-dimensional scanning mirror)  102 . An angle formed between the surface normal  301  of the mirror and the surface normal of the imaging surface  302  is θmems. The angle between the exit surface  103   b  and the incident surface  103   a  of the first prism  103  is θp1. The angle between the exit surface  104   b  and the incident surface  104   a  of the second prism  104  is θp2 while θs1 is the deflection angle of the deflection component (MEMS two-dimensional scanning mirror)  102  along the first scanning direction and θs2 is the deflection angle of the deflection component (MEMS two-dimensional scanning mirror)  102  along the second scanning direction. 
         [0035]    The positive and the negative of the values of θsh, θsc, θs1 are defined as followings: The positive is defined as the surface normal of the imaging surface  302  is rotated counterclockwise to the light while the negative is defined as clockwise rotation. Whether the rotation is clockwise or counterclockwise is determined by the small rotation angle. 
         [0036]    Refer to  FIG. 8 , the trapezoidal distortion mentioned in the present invention is defined as: ((wt−wb)/w0)×100 (%). The TV distortion includes top side distortion defined as (h1/h0)×100 (%), bottom side distortion defined as (h2/h0)×100 (%), left side distortion defined as (w1/w0)×100 (%) and right side distortion defined as (w2/w0)×100 (%). wt is an actual horizontal width on the top side of the projected image; wb is an actual horizontal width on the bottom side of the projected image; w0 is an actual horizontal width at the center of the projected image; h1 is the vertical distortion on top of the projected image and h2 is the vertical distortion on bottom of the projected image; w1 is the horizontal distortion on left of the projected image and w2 is the horizontal distortion on right of the projected image; and h0 is the actual vertical length at the center of the projected image. 
         [0037]    The techniques of the present invention features on that the laser projector of the present invention satisfies the following equation (1) and equation (2). 
         [0000]      0.1&lt;θmems/θin&lt;0.4   (1)
 
         [0000]      θsh&gt;θsc &gt;θs1&gt;0° or θsh&lt;θsc&lt;θs1&lt;0°  (2)
 
         [0000]    wherein θmems is the angle between the surface normal of the mirror and the surface normal of the imaging surface formed in the second scanning direction (Y-axis, slow axis) when the deflection component (MEMS two-dimensional scanning mirror)  102  is at the initial state; θin is an incident angle of the input light beam in the second scanning direction when the input light beam from the light source is incident into the mirror and the deflection component (MEMS two-dimensional scanning mirror)  102  is at the initial state; θsh is the angle between the scanning light beam and the surface normal of the imaging surface in the second scanning direction with the larger absolute value under the condition that the deflection angle θs2 of the deflection component (MEMS two-dimensional scanning mirror)  102  in the second scanning direction is maximum. θsc is the angle between the scanning light beam and the surface normal of the imaging surface in the second scanning direction when the deflection component (MEMS two-dimensional scanning mirror)  102  is at the initial state (the deflection angle θs2 is zero). θs1 is the angle between the scanning light beam and the surface normal of the imaging surface in the second scanning direction with the smaller absolute value under the condition that the deflection angle θs2 of the deflection component (MEMS two-dimensional scanning mirror)  102  in the second scanning direction is maximum. 
         [0038]    The first embodiment of the present invention satisfies the following conditions: Trapezoidal distortion&lt;2.0%; TV distortion&lt;2%; θmems/θin: 0.13˜0.25; θp1: 29°˜33°; θp2: 12°˜16°; θs1&lt;14.2°; θs2&lt;8.1°; θsh&gt;θsc&gt;θs1&gt;0° or θsh&lt;θsc&lt;θs1&lt;0°. Thus the present invention can achieve image distortion modulation and image lift. 
         [0039]    The first embodiment of the present invention further satisfies: θmems/θin=0.1889; θp1=30.910°; θp2=13.702°; θs1=14.000°; θs2=8.051°, θsh&gt;θsc&gt;θs1&gt;1.0°; Trapezoidal distortion=1.069%; top side TV distortion=1.751%; bottom side TV distortion=1.223%; left side TV distortion=0.7749/0; right side TV distortion=0.774%. Thus the present invention can achieve image distortion modulation and image lift. 
         [0040]    The component location and ray tracing of the above embodiment are shown in the following table 1 and table 2. 
         [0041]    The second embodiment of the present invention satisfies the following conditions: Trapezoidal distortion&lt;1.5%; TV distortion&lt;1.594%; 0.25&lt;θmems/θin&lt;0.38; 27°&lt;θp1&lt;30°; 12°&lt;θp2&lt;16°; θs1&lt;14.2°; θs2&lt;8.7°; θsh&gt;θsc&gt;θs1&gt;1.0°. Thus the present invention can achieve image distortion modulation and image lift. 
         [0042]    The second embodiment of the present invention further satisfies: θmems/θin=0.3159; θp1=28.490°; θp2=14.017°; θs1=14°; θs2=8.65°; θsh&gt;θsc&gt;θs1&gt;1.0°. Trapezoidal distortion=1.045%; top side TV distortion=1.003%; bottom side TV distortion=1.198%; left side TV distortion=0.721%; right side TV distortion=0.721%. Thus the present invention can achieve image distortion modulation and image lift. 
         [0043]    The component location and ray tracing of the second embodiment are shown in the following table 3 and table 4. 
         [0044]    The third embodiment of the present invention satisfies the following conditions: Trapezoidal distortion&lt;1.5%; TV distortion&lt;1.2% ; 0.22&lt;θmems/θin&lt;0.38; 24°&lt;θp1&lt;28°; 15°&lt;θp2&lt;19°; θs1&lt;10.6°; θs2&lt;6.4°; θsh&gt;θsc&gt;θs1&gt;0.5°. Thus the present invention can achieve image distortion modulation and image distortion correction. 
         [0045]    The third embodiment of the present invention further satisfies: θmems/θin=0.2995; θp1=26.132°; θp2=17.387°; θs1=10.5°; θs2=6.317°; θsh&gt;θsc&gt;θs1&gt;0.5°; Trapezoidal distortion=1.139%; top side TV distortion=0.996%; bottom side TV distortion=1.024%; left side TV distortion=0.594%; right side TV distortion=0.594%. Thus the present invention can achieve image distortion modulation and image lift. 
         [0046]    The component location and ray tracing of the third embodiment are shown in the following table 5 and table 6. 
         [0047]    Compared with conventional techniques, the present invention has following advantages:
   (1) First the production of the components is easier and the cost is reduced. The first prism and the second prism are processed by plane machining. And the optical surface of each prism includes only an incident surface and an exit surface. Thus the production of the prisms is easier and the cost is also down.   (2) The present invention has lower tolerance requirement for assembly. The optical surfaces of the two prisms are flat surfaces so that the component tolerance is increased and the assembly tolerance is reduced. This is beneficial to quality control and mass production of the laser projector.   (3) The laser projector of the present invention achieves image distortion modulation and image lift. This helps increasing of the market share and competitiveness of the laser projector   
 
         [0051]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the is specific details, and representative devices shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 component location of the first embodiment 
               
             
          
           
               
                 Component 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Surface 
                 X-coordinate 
                 Y-coordinate 
                 Z-coordinate 
                 Surface tilt Y 
                 Nd 
                 Vd 
                 Comment 
               
               
                   
               
             
          
           
               
                 0 
                 0.00000000 
                 −1.12221830 
                 3.01121713 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 201 
               
               
                 1 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 MEMS-mirror (102) 
               
               
                 2 
                 0.00000000 
                 3.83001165 
                 5.08532918 
                 8.19982058 
                 1.69680123 
                 56.19982541 
                 Prism-01 (103a) 
               
               
                 3 
                 0.00000000 
                 3.83001165 
                 7.83523177 
                 −22.71034332 
                 0.00000000 
                 0.00000000 
                 Prism-01 (103b) 
               
               
                 4 
                 0.00000000 
                 4.74332635 
                 9.41158763 
                 −13.70158853 
                 1.76182349 
                 26.61320270 
                 Prism-02 (104a) 
               
               
                 5 
                 0.00000000 
                 4.74332635 
                 11.00820493 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 Prism-02 (104b) 
               
               
                 6 
                 0.00000000 
                 0.00000000 
                 513.55820493 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 Image plane (105) 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 ray tracing of the first embodiment 
               
             
          
           
               
                 Raytrace 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Surface 
                 X-coordinate 
                 Y-coordinate 
                 Z-coordinate 
                 X-cosine 
                 Y-cosine 
                 Z-cosine 
                 Incident Angle 
                 Comment 
               
               
                   
               
             
          
           
               
                 0 
                 0.000000 
                 −1.122218 
                 3.011217 
                 0.000000 
                 −0.349216 
                 0.937042 
                 20.439383 
                 201 
               
               
                 1 
                 0.000000 
                 0.000000 
                 0.000000 
                 0.000000 
                 0.499360 
                 0.866395 
                 25.198514 
                 MEMS-mirror (102) 
               
               
                 2 
                 0.000000 
                 2.849577 
                 4.944050 
                 0.000000 
                 0.226334 
                 0.974050 
                 38.157466 
                 Prism-01 (103a) 
               
               
                 3 
                 0.000000 
                 3.548737 
                 7.952951 
                 0.000000 
                 0.107434 
                 0.994212 
                 9.629019 
                 Prism-01 (103b) 
               
               
                 4 
                 0.000000 
                 3.732975 
                 9.657914 
                 0.000000 
                 0.164430 
                 0.986389 
                 7.534149 
                 Prism-02 (104a) 
               
               
                 5 
                 0.000000 
                 3.958067 
                 11.008205 
                 0.000000 
                 0.291778 
                 0.956486 
                 9.464118 
                 Prism-02 (104b) 
               
               
                 6 
                 0.000000 
                 157.261741 
                 513.558205 
                 0.000000 
                 0.291778 
                 0.956486 
                 16.964410 
                 Image plane (105) 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 component location of the second embodiment 
               
             
          
           
               
                 Component 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Surface 
                 X-coordinate 
                 Y-coordinate 
                 Z-coordinate 
                 Surface tilt Y 
                 Nd 
                 Vd 
                 Comment 
               
               
                   
               
             
          
           
               
                 0 
                 0.00000000 
                 −2.98323345 
                 7.43798016 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 201a 
               
               
                 1 
                 0.00000000 
                 1.32774778 
                 5.15646746 
                 −14.24461058 
                 1.72916425 
                 54.66903147 
                 Prism-01 (103b) 
               
               
                 2 
                 0.00000000 
                 1.32774778 
                 2.51276083 
                 14.24550669 
                 0.00000000 
                 0.00000000 
                 Prism-01 (103a) 
               
               
                 3 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 MEMS-mirror (102) 
               
               
                 4 
                 0.00000000 
                 1.32774778 
                 2.51276083 
                 14.24550669 
                 1.72916425 
                 54.66903147 
                 Prism-01 (103a) 
               
               
                 5 
                 0.00000000 
                 1.32774778 
                 5.15646746 
                 −14.24461058 
                 0.00000000 
                 0.00000000 
                 Prism-01 (103b) 
               
               
                 6 
                 0.00000000 
                 2.81548297 
                 9.50819879 
                 −7.97965078 
                 1.88300431 
                 40.81091485 
                 Prism-02 (104a) 
               
               
                 7 
                 0.00000000 
                 2.81548297 
                 11.15174726 
                 6.03703961 
                 0.00000000 
                 0.00000000 
                 Prism-02 (104b) 
               
               
                 8 
                 0.00000000 
                 0.00000000 
                 514.15174726 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 Image plane (105) 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 ray tracing of the second embodiment 
               
             
          
           
               
                 Raytrace 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Surface 
                 X-coordinate 
                 Y-coordinate 
                 Z-coordinate 
                 X-cosine 
                 Y-cosine 
                 Z-cosine 
                 Incident Angle 
                 Comment 
               
               
                   
               
             
          
           
               
                 0 
                 0.00000000 
                 −2.98323345 
                 7.43798016 
                 0.00000000 
                 −0.67861401 
                 0.73449508 
                 42.73543189 
                 201a 
               
               
                 1 
                 0.00000000 
                 −1.55037212 
                 5.88712862 
                 0.00000000 
                 −0.25298664 
                 0.96746977 
                 56.98004247 
                 Prism-01 (103b) 
               
               
                 2 
                 0.00000000 
                 −0.54375147 
                 2.03761680 
                 0.00000000 
                 −0.25805723 
                 0.96612963 
                 0.40881006 
                 Prism-01 (103a) 
               
               
                 3 
                 0.00000000 
                 0.00052129 
                 −0.00006312 
                 0.00000000 
                 0.48119254 
                 0.87661493 
                 21.85906715 
                 MEMS-mirror 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                 (102) 
               
               
                 4 
                 0.00000000 
                 1.38830279 
                 2.52813479 
                 0.00000000 
                 0.15478913 
                 0.98794753 
                 43.00882465 
                 Prism-01 (103a) 
               
               
                 5 
                 0.00000000 
                 1.78203395 
                 5.04113896 
                 0.00000000 
                 0.08632463 
                 0.99626706 
                 5.34004400 
                 Prism-01 (103b) 
               
               
                 6 
                 0.00000000 
                 2.17685304 
                 9.59772108 
                 0.00000000 
                 0.11113110 
                 0.99380576 
                 3.02745031 
                 Prism-02 (104a) 
               
               
                 7 
                 0.00000000 
                 2.34506684 
                 11.10199705 
                 0.00000000 
                 0.30863939 
                 0.95117913 
                 12.41756220 
                 Prism-02 (104b) 
               
               
                 8 
                 0.00000000 
                 165.57506349 
                 514.15174726 
                 0.00000000 
                 0.30863939 
                 0.95117913 
                 17.97725264 
                 Image plane (105) 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 component location of the third embodiment 
               
             
          
           
               
                 Component 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Surface 
                 X-coordinate 
                 Y-coordinate 
                 Z-coordinate 
                 Surface tilt Y 
                 Nd 
                 Vd 
                 Comment 
               
               
                   
               
             
          
           
               
                 0 
                 0.00000000 
                 −2.00000000 
                 5.09620929 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 201a 
               
               
                 1 
                 0.00000000 
                 0.56723606 
                 3.62141825 
                 −6.98387251 
                 1.88300431 
                 40.81091485 
                 Prism-01 (103b) 
               
               
                 2 
                 0.00000000 
                 0.56723606 
                 2.00290573 
                 19.14801635 
                 0.00000000 
                 0.00000000 
                 Prism-01 (103a) 
               
               
                 3 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 MEMS-mirror (102) 
               
               
                 4 
                 0.00000000 
                 0.56723606 
                 2.00290573 
                 19.14801635 
                 1.88300431 
                 40.81091485 
                 Prism-01 (103a) 
               
               
                 5 
                 0.00000000 
                 0.56723606 
                 3.62141825 
                 −6.98387251 
                 0.00000000 
                 0.00000000 
                 Prism-01 (103b) 
               
               
                 6 
                 0.00000000 
                 0.80000000 
                 6.64387071 
                 0.00000000 
                 1.88300431 
                 40.81091485 
                 Prism-02 (104a) 
               
               
                 7 
                 0.00000000 
                 0.80000000 
                 7.89868774 
                 17.38732901 
                 0.00000000 
                 0.00000000 
                 Prism-02 (104b) 
               
               
                 8 
                 0.00000000 
                 0.00000000 
                 510.89868774 
                 0.00000000 
                 0.00000000 
                 0.00000000 
                 Image plane (105) 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 ray tracing of the third embodiment 
               
             
          
           
               
                 Raytrace 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Surface 
                 X-coordinate 
                 Y-coordinate 
                 Z-coordinate 
                 X-cosine 
                 Y-cosine 
                 Z-cosine 
                 Incident Angle 
                 Comment 
               
               
                   
               
             
          
           
               
                 0 
                 0.00000000 
                 −2.00000000 
                 5.09620929 
                 0.00000000 
                 −0.63237386 
                 0.77466334 
                 39.22547995 
                 201a 
               
               
                 1 
                 0.00000000 
                 −0.94757600 
                 3.80698098 
                 0.00000000 
                 −0.26620068 
                 0.96391763 
                 46.20935245 
                 Prism-01 (103b) 
               
               
                 2 
                 0.00000000 
                 −0.36040161 
                 1.68081152 
                 0.00000000 
                 −0.20986519 
                 0.97773033 
                 3.70970685 
                 Prism-01 (103a) 
               
               
                 3 
                 0.00000000 
                 0.00038410 
                 −0.00003482 
                 0.00000000 
                 0.38225452 
                 0.92405708 
                 17.29392733 
                 MEMS-mirror 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                 (102) 
               
               
                 4 
                 0.00000000 
                 0.87283459 
                 2.10901561 
                 0.00000000 
                 0.02439515 
                 0.99970239 
                 41.62141905 
                 Prism-01 (103a) 
               
               
                 5 
                 0.00000000 
                 0.90872008 
                 3.57958685 
                 0.00000000 
                 −0.06334460 
                 0.99799171 
                 5.58599462 
                 Prism-01 (103b) 
               
               
                 6 
                 0.00000000 
                 0.71422363 
                 6.64387071 
                 0.00000000 
                 −0.03347045 
                 0.99943971 
                 3.63181000 
                 Prism-02 (104a) 
               
               
                 7 
                 0.00000000 
                 0.67352708 
                 7.85908424 
                 0.00000000 
                 0.22375521 
                 0.97464537 
                 15.46925503 
                 Prism-02 (104b) 
               
               
                 8 
                 0.00000000 
                 116.15935840 
                 510.89868774 
                 0.00000000 
                 0.22375521 
                 0.97464537 
                 12.92969075 
                 Image plane (105)