Abstract:
A device for linear scanning including a mirror roof structure. The mirror roof structure includes a roof prism with at least two reflecting surfaces or at least two mirror surfaces. The reflecting surfaces of the roof prism or the two mirror surfaces are mutually perpendicular reflecting surfaces intersecting in a line of intersection. A scanning mechanism moves the mirror roof structure in a direction perpendicular to a plane of bilateral symmetry of the mirror roof structure. The line of intersection is included in the plane of bilateral symmetry; and an incident beam entering the mirror roof structure and an exit beam exiting the mirror roof structure are angularly separated by a substantial angle.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a continuation-in-part application of co-pending U.S. patent application Ser. No. 11/444,352 filed Jun. 1, 2006, now allowed. The disclosure of that application is hereby expressly incorporated by reference in its entirety and is hereby expressly made a portion of this application. 
     
    
     FIELD AND BACKGROUND 
       [0002]    The present invention relates to an optical scanning device; more particularly, to a device in which scanning is performed by reciprocating linear or continuous rotary movement of a ray-deflecting element. 
         [0003]    Optical scanning is well-known in which an image produced by an optical system is moved across an image plane typically including a photodetector. Optical scanning has many civilian as well as military uses. Present optical scanners include galvanometer-based devices. In the galvanometer based devices, the scanning movement is produced by a beam-deflecting element such as a flat mirror, which is angularly deflected, oscillating about an axis perpendicular to the optical axis by a galvanometer-type drive (e.g. moving-coil, moving-magnet drive). In these scanners, also known as galvo-based scanners, the oscillating mirror usually constitutes a pupil of the optical scanning system. Consequently there is substantial beam excursion across the system aperture, causing optical aberrations such as coma, distortion and field curvature. Therefore, these optical systems usually are substantially larger than diameters of scanned beams and are complex in order reduce the different optical aberrations. To compensate for these aberrations one or more of the following is required: an additional optical element, such as an F-θ (theta) objective lens or a flattening lens; an axial movement of imaging lens for field curvature compensation and non-linear scanning. An F-theta lens satisfies the condition that the image height equals the product of the focal length of the objective and the scanning angle θ (theta). A flattening lens is usually located close to the scanned plane and corrects field curvature relative to the required flat field. These optical systems typically require several aspherical surfaces (increasing cost) and provide at best no more than average resolution. A second known disadvantage of the galvo-based scanners is the relatively large mass, especially for large beam diameters, and, consequently, large inertia of the oscillating system, which, especially with wide beams, strictly limits the scanning frequency. Owing to the fact that the scanning mirror mass is directly proportional to the cube of aperture, effective scanning can be performed only at small apertures. Therefore, additional optical systems (telescopes for infinite conjugate and lens systems for finite conjugate) are usually utilized for transforming large apertures of incident beams into narrow parallel beams for purposes of angular scanning. 
         [0004]    Rotating reflecting polygons are usually utilized for continuous light beam scanning. The use of polygons has an advantage of high angular scanning velocity. However, as in galvanometer-based scanning, there is the substantial beam excursion across the system aperture, since the rotating mirror usually constitutes a pupil of the optical scanning system. Therefore, these optical systems usually are substantially larger than diameters of scanned beams, even more than galvanometric-based scanning systems, and complicated for purposes of different optical aberrations compensation (e.g. spherical aberration, coma, distortion, field curvature aberration). Additional drawbacks of polygon-based scanning systems are low scanning efficiency and pupil&#39;s wandering, both due to polygon geometry. 
         [0005]    U.S. Pat. No. 6,429,423 discloses a device for optical scanning, including a Porro prism or equivalent intersecting mirrors whereby an incident beam of light undergoes two reflections, and an optical system i.e. an objective capable of forming an image of an object. An optical axis, passing through a Porro prism, is rotated by 180° and exits in the opposite direction offset from its entrance point. The two reflections cause two ninety degree folds of the optical axis so that the incident and exit optical axes are parallel (or collinear) on the same side of the Porro prism. An additional optical element is required to unfold at least one of the incident or exit optical axes. Furthermore in order to separate the entrance and exit beams a relatively long optical path is required inside the Porro prism, hence a Porro prism does not support a large numerical aperture. 
         [0006]    There is thus a need for, and it would be highly advantageous, to have an optical scanner which overcomes the disadvantages of prior art optical scanners and specifically an optical scanner in which the optical path is small allowing high numerical aperture with small optical elements and without additional optical elements required to separate the incident and exit beams. 
         [0007]    The term “pre-objective” scanning system as used herein refers to an optical system in which a scanning element is placed before the focusing objective lens e.g. F-theta scan lens A flat focal plane is preferably obtained at the focus position of the objective lens. The pre-objective scanning system is advantageous in terms of scanning speed, while both scanning field size and spot size are limited heavily by the lens design. 
         [0008]    The term “post-objective” scanning system as used herein refers to an optical system in which a scanning element is placed after the focusing lens. The post-objective optical scanner employs a focusing lens typically having a simple design; however the point of focus, in general, is on a curved surface. Accordingly, the curvature of image must be corrected when the post-objective optical scanner is employed. 
         [0009]    The term “telecentric” or “telecentricity” as used herein is a property of certain multi-element lens designs in which the chief rays for all points across the object or image are collimated. For example, telecentricity occurs when the chief rays are parallel to the optical axis, in object and/or image space. Another way of describing telecentricity is to state that the entrance pupil and/or exit pupil of the system is located at infinity. 
         [0010]    The term “numerical aperture” referring to a lens or an optical system as used herein is n·sin θ, where n is index of refraction of the medium and θ is the half-angle of the maximum cone of light that can enter or exit the lens. In general, θ is the angle of the real marginal ray in the system. The term “high numerical aperture” as used herein refers to a numerical aperture greater than 0.4 or greater than 0.5. 
         [0011]    The term “roof prism” as used herein refers to a prism with two reflecting faces, the two reflecting faces mutually perpendicular or intersecting at ninety degrees, wherein the incident beam to the roof prism and the exit beam from the roof prism are not parallel or, if parallel, the entrance beam and exit beam are on different sides of the roof prism or the incident beam to the roof prism and the exit beam from the roof prism are angularly separated by a substantial angle. A Porro prism used in U.S. Pat. No. 6,429,423 is not a “roof prism” as used herein, because the incident and exit beams to a Porro prism are parallel (rotated by 180 degrees) and are on the same side of the Porro prism. 
         [0012]    The term “mirror roof structure” as used herein refers to either a “roof prism” or to two reflecting mirror faces disposed at a ninety degree angle, so that a light ray incident on one of the mirrors undergoes reflection from both mirrors and the incident ray and the exit ray are angularly separated by a substantial angle. 
         [0013]    The term “angularly separated” is used herein refers to entrance and exit beams to a prism or other optical system. An entrance beam and an exit beam are “angularly separated” when the incident beam and the exit beam are not parallel or if parallel the entrance beam and exit beam are on different sides of the roof prism. The term “parallel” as used herein includes “anti-parallel” or 180 degree rotation. Angularly separated by a “substantial angle” refers to an exit beam angularly separated from the exit beam by ±30 to ±90 degrees. The term “dimension” of a roof prism as used herein is substantially equal to the length of the physical path within the roof prism. Although there are no incident and exit surfaces in “mirror roof structure”, the “dimension” of a mirror roof structure including two mirror faces disposed at ninety degrees is similar to the physical path (not optical path) of light through its equivalent “roof prism”. “Roof prisms” and mirror roof structures with the same “dimension” have different equivalent optical paths owing to the different indices of refraction. 
         [0014]    The term “plane of symmetry” or “plane of bilateral symmetry” as used herein referring to a mirror roof structure or roof prism is a plane of bilateral symmetry including the line of intersection of the two reflecting faces forming the “roof” of the prism or the mirror surfaces of mirror roof structure. The “plane of symmetry” is equivalent to or coplanar with the plane formed by the incident and exiting optical axes. 
         [0015]    The term “multi-dimensional scanning” as used herein includes linear scanning in more than one dimension, particularly linear scanning over area and volume. The term “lateral” as in “lateral direction” of scanning as used herein refers to scanning in a plane (such as in x and y Cartesian directions) and the term “longitudinal” as in “longitudinal” direction refers to scanning (such as in the z Cartesian direction) perpendicular to the plane of lateral scanning. 
         [0016]    The terms “incident” and “entrance” are used herein interchangeably when referring to a beam entering an optical system. 
       BRIEF SUMMARY 
       [0017]    According to the present invention there is provided a device for linear scanning including a mirror roof structure. The mirror roof structure includes a roof prism with at least two reflecting surfaces or at least two mirror surfaces. The reflecting surfaces of the roof prism or the two mirror surfaces are mutually perpendicular reflecting surfaces intersecting in a line of intersection. A scanning mechanism moves the mirror roof structure in a direction perpendicular to a plane of bilateral symmetry of the mirror roof structure. The line of intersection is included in the plane of bilateral symmetry; and an incident beam entering the mirror roof structure and an exit beam exiting the mirror roof structure are angularly separated by a substantial angle. Preferably, the scanning mechanism generates periodic motion or rotational motion of the mirror roof structure with a radius of motion greater than a dimension of the mirror roof structure. The mirror roof structure is preferably one of multiple mirror roof structures mounted on a disk and the scanning mechanism rotates the disk about the center of the disk. The radius of the disk is much greater than a dimension of the mirror roof structure. Preferably, the roof prism is an Amici roof prism or one of Abbe Type A, Abbe Type B, Leman, Penta, Schmidt, Frankford Arsenal prisms, Delta, Pechan, and Abbe-Koenig. Preferably, a second mirror roof structure is oriented perpendicularly to the mirror roof structure and the plane of bilateral symmetry of the second mirror roof structure is perpendicular to the plane of bilateral symmetry of the first mirror roof structure. A second scanning mechanism moves the second mirror roof structure in a direction perpendicular to the plane of bilateral symmetry of the second mirror roof structure, and motion of the first mirror roof structure and the motion of the second mirror roof structure are perpendicular. An objective lens preferably of high numerical aperture images a source, and the mirror roof structure is located between the objective lens and an image. Preferably, a relay lens relays the image to a second image and the objective lens or the relay lens is telecentric. Preferably, an intermediate image is located between first and second roof prisms. Preferably, the numerical aperture is greater than 0.3 and the mirror roof structure has a dimension of less than ten millimeters. Preferably, the objective lens is part of an optical system which includes a z-scan mechanism which is used to modify focusing depth of the optical system. Preferably, the z-scan mechanism moves at least one lens of the optical system along an incident optical axis. Preferably, a transparent optical medium is depth scanned in the z direction by using the z-scan mechanism. When the transparent optical medium causes significant spherical aberration the optical system is optimized to cancel the spherical aberration for the entire range of transparent optical medium depth. 
         [0018]    According to the present invention there is provided a method for linear scanning. A roof mirror structure is provided and located between an object and an image plane. The mirror roof structure includes either a roof prism including two reflective surfaces or at least two mirror surfaces. The reflective surfaces or mirror surfaces are mutually perpendicular and intersecting in a line of intersection. The mirror roof structure is scanned in a lateral direction substantially perpendicular to a plane of bilateral symmetry of the mirror roof structure. The plane of bilateral symmetry includes the line of intersection. The scanning causes a point in the image plane to move substantially in the lateral direction. 
         [0019]    A second mirror roof structure oriented perpendicularly to said mirror roof structure is optionally provided and oriented so the plane of bilateral symmetry of the second mirror roof structure is substantially perpendicular to the plane of bilateral symmetry of the (first) mirror roof structure. The second mirror roof structure is scanned in a direction substantially perpendicular to the second plane of bilateral symmetry of the second mirror roof structure. Motion of the (first) mirror roof structure and motion of the second mirror roof structure are substantially perpendicular. 
         [0020]    According to the present invention there is provided an item scanned and/or a scan report, according the methods disclosed herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein like reference numbers are used to refer to like elements in all the drawings unless otherwise indicated: 
           [0022]      FIG. 1  illustrates in front view a preferred exemplary embodiment  10  of a linear scanner according to the present invention, including an optical system forming an image, and an Amici prism scanning element; 
           [0023]      FIG. 1   a  illustrates the path direction of the light rays reflected by the Amici prism; 
           [0024]      FIG. 2  illustrates embodiment  10  in side view. Linear scanner scans through the optical system, by moving Amici roof prism in a direction perpendicular to the optical axis. Two positions of the prism are shown; 
           [0025]      FIG. 3  illustrates a mechanical mechanism for implementing scanner motion in embodiment  10  of the present invention using two flexible members; 
           [0026]      FIG. 4  illustrates shifting of the Amici prism during scanning according to  FIG. 3 ; 
           [0027]      FIG. 5  presents another embodiment  50  of the present invention with a scanning element and relay lens. The relay lens performs additional imaging of the scanned intermediate image plane; 
           [0028]      FIG. 6  presents side view on embodiment  50  with one scanning element and telecentric relay lens between lateral scanning element and relay lens. The pupil of telecentric relay lens is positioned at the back focal plane of the relay lens; 
           [0029]      FIG. 7  presents a front view of another embodiment  70  with two scanning elements and relay lens; 
           [0030]      FIG. 8  presents a side view embodiment  70  with two scanning elements and a relay lens. The pupil of telecentric relay lens is positioned at the back focal plane of the relay lens; 
           [0031]      FIG. 9  presents another embodiment  130  with multiple continuously rotating Amici prisms. 
           [0032]      FIG. 10  presents upper view of multiple rotating Amici prisms according to embodiment  130 ; 
           [0033]      FIG. 11  presents another embodiment of the present invention with multiple scanning Amici prisms and relay lens. The lens performs additional imaging of the scanned intermediate image plane; 
           [0034]      FIG. 12  presents another exemplary embodiment with reciprocal scanning Amici prism, with variable depth of the focused beam inside transparent media; 
           [0035]      FIG. 13  presents additional patent embodiment with multiple scanning Amici prisms, with variable depth of the focused beam inside transparent media; 
           [0036]      FIG. 14  illustrates in front view an embodiment  11  of a linear scanner according to the present invention, including an optical system forming an image, and two scanning elements each including two mutually perpendicular reflecting surfaces forming a mirror roof structure; 
           [0037]      FIG. 15  illustrates the mirror roof structure of  FIG. 14 , in an isometric view showing light rays reflected by the two reflecting surfaces of the mirror roof structure; and 
           [0038]      FIG. 16  illustrates embodiment  11  in side view; and 
           [0039]      FIG. 16  illustrates a method according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]    Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures. 
         [0041]    It should be noted that although the drawings herein explicitly illustrate imaging of a light source as an object onto one or more image planes, that the present invention includes embodiments with the direction of the optical rays reversed. Such equivalence results in generating new pre-objective and post-objective embodiments of the present invention. It should further be noted that although the drawings herein as well as the description herein explicitly illustrate and describe embodiments of the present invention using a roof prism. One skilled in the art of optical design would be able to replace the roof prism with a mirror roof structure of two mirrors disposed at ninety degrees. Optical design using the mirror surfaces is substantially equivalent to an optical design using the roof prism and may be achieved by replacing the roof surfaces of the roof prism by metallic mirrors and setting the index of refraction of the optical material of the roof prism at 1.00. 
         [0042]    Before explaining embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of design and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
         [0043]    By way of introduction, principal intentions of the present invention are to: 
         [0000]    (1) provide in pre-objective linear scanning systems, scanning of the rays from the object in diverging rays is performed by a mirror roof structure (e.g. Amici prism or two mirror surfaces disposed at ninety degrees, perpendicular to the optical axis direction, in close vicinity to the object or to the element for producing light;
 
(2) provide in post-objective linear scanning systems, scanning of the scene image in converging rays is performed by a mirror roof structure (e.g. Amici type prism or two mirror surfaces disposed at ninety degrees), perpendicular to the optical axis direction, in close vicinity to the image plane or to the light-detecting element for detecting the incident beam of light;
 
(3) provide, in reciprocating beam-deflecting element, a telecentric objective system. Pre-objective linear scanning performs telecentric ray-tracing in the pre-objective space, and post-objective linear scanning systems perform telecentric ray-tracing in the post-objective space;
 
(4) provide, in a continuously rotating beam-deflecting element, a substantially telecentric objective system. Pre-objective linear scanning performs telecentric ray-tracing in the pre-objective space, post-objective linear scanning systems performs telecentric ray-tracing in the post-objective space.
 
         [0044]    Due to a relatively short equivalent optical path through the mirror roof structure, objectives with high numerical aperture are provided, allowing the creation of a high resolution system. 
         [0045]    It should be noted that while the discussion herein is directed to scanning, using an Amici roof prism, the principles of the present invention may be adapted for use with other roof prisms. Most prisms have reflective surfaces, which could be transformed into a “roof” and used according to the teachings of the present invention. Lateral translation of the “roof” (in a direction perpendicular to a plane of symmetry including the roof intersection) shifts the rays on twice distance, exactly as in using an Amici roof prism. Prisms which may be used with a “roof” in different embodiments of the present invention include (but not limited to: Abbe Type A, Abbe Type B, Leman, Penta, Schmidt, Frankford Arsenal prisms, Delta, Pechan, and Abbe-Koenig. 
         [0046]    Further the mechanism used to periodically move the scanning mirror roof structure may be of any such mechanisms known in the art including mechanical, piezoelectric or electromagnetic mechanisms. 
         [0047]    The present invention in different embodiments is applicable (but not limited) to: three dimensional microscopy, laser beams deflection and positioning in three dimensions, industrial laser material processing, laser TV, medical and biomedical technology including surgery, optical characters recognition, microlithography, optical switching, printing and inspection, “laser show” and entertainment business. Different embodiments of the present invention may be applied to oscillatory “galvo”-type linear scanning or continuous rotating scanning. Similar different embodiments of the present invention may be applied to both pre-objective and post-objective scanning systems. 
         [0048]    Referring now to the drawings,  FIG. 1  illustrates a front view of a linear optical scanner  10 , according to an embodiment of the present invention. Light source  101  emits light rays which are imaged by an imaging lens  103 , through Amici roof prism  105 , as scanning element, to focusing point  107  at image plane  109 . Reference is now made to  FIG. 1   a  of Amici roof prism  105 . Amici roof prism  105  includes a plane of symmetry which includes an intersection  151  between the two roof surfaces. The direction of scanning is perpendicular to the plane of symmetry and parallel to the entrance and exit surfaces of prism  105 . 
         [0049]    Reference is now made to  FIG. 2  which illustrates a side view of optical scanner  10 . Lens  103  is shown. When prism  105  is laterally translated along the direction of scanning a distance d, the optical ray path and direction remains unchanged and all rays are shifted parallel to the direction of translation by distance  2   d . Amici prism is denoted by reference numeral  105  in the original position and by  105 ′ after a lateral translation along the direction of scanning. Consequently, initial image is at position  107  and image position shifted by  2   d  is denoted by  107 ′. Scanning of the image is performed by Amici prism  105 , oscillating in the lateral direction. 
         [0050]    Reference is now made to  FIG. 3  which illustrates a device, according to an embodiment of the present invention.  FIG. 3  illustrates a side view and a view from angle A, labeled “View A”. Point source  101  emits light rays which are imaged by imaging lens  103 , through Amici roof prism  105 , as scanning element, to focusing point  107  at image plane  109 . Amici prism  105  oscillates parallel to the scanning direction by attaching two flexible members  111  which bend in the direction of scanning. Preferably, flexible members  111  have a principal axis parallel to the Amici roof surfaces intersection  151 . Amici prism in initial position of the prism is denoted by reference numeral  105 , while  105 A and  105 B denote two extreme positions of the oscillating Amici prism. Parallel translation is achieved due to equal deformation of flexible members  111 . 
         [0051]    Reference is now made to  FIG. 4  which illustrates in more detail the optical path though prism  105 , shown in cross section, while scanning using the device of  FIG. 3 , according to an embodiment of the present invention. While oscillating, according to the method illustrated in  FIG. 3 , prism  105  performs a slight shift to prism  105 ′, the shift perpendicular to the scanning direction and parallel to the roof intersection  151 . However, as illustrated in  FIG. 4 , the optical path inside Amici prism  105  does not change, due to equal and opposite changes of respective optical paths at entrance to prism  105  and at exit from the prism, i.e. δz=δy. 
         [0052]    Reference is now made to  FIGS. 5 and 6  which illustrate another embodiment of the present invention.  FIGS. 5 and 6 , show respectively a front view and a side view of a scanning system  50 . Point source  101  emits light rays which are imaged by imaging lens  103 , through Amici roof prism  105 , as scanning element. An optical relay lens  113  is shown in both views. In the side view illustrated in  FIG. 6 , optical relay lens  113  reimages an intermediate image  119  of the point source into a final image  119 ′. Consequently, all points on the scanned line, represented by central point of image  119  and one of extreme points  121 , are re-imaged into the line, represented by points  119 ′ and  121 ′. Relay lens  113  is telecentric because Amici prism  105  during the scanning performs a parallel shift of rays. The exit pupil  115  of lens  113  is positioned at the back focal point of lens  113  and therefore the entrance pupil of lens  113  is located at infinity. 
         [0053]    Reference is now made to  FIG. 7  in which an additional embodiment  70 , according to the present invention, is illustrated. Point source  101  emits light rays which are imaged by imaging lens  103 , through two Amici roof prism  105  and  106 , as scanning elements. Reference is now also made to  FIG. 8 , which presents respectively front and side orthogonal views of an optical scanning system with two Amici roof prisms  105  and  106  in perpendicular directions. Scanning in horizontal direction is performed, as in previous embodiment  50 , by Amici prism  105  and scanning in vertical direction is performed by additional Amici prism  106 , thereby allowing scanning in both lateral directions (XY scan). In  FIG. 7 , Amici prism  106  is denoted by reference numeral  106  in the original position and by  106 ′ after a lateral translation along the direction of scanning. In  FIG. 8 , Amici prism  105  is denoted by reference numeral  105  in the original position and by  105 ′ after a lateral translation along the direction of scanning. Since both scanning prisms  105  and  106  perform a parallel shift of rays, as in previous embodiment  50 , optical relay lens  125  is telecentric with exit pupil located at the back focal plane of lens  125 . 
         [0054]    Reference is now made to  FIG. 9  which illustrates another embodiment  130  of the present invention. Point source  101  emits light rays which are imaged by imaging lens  103 , through Amici roof prism  105 , as scanning element. Two Amici prisms  105 , are shown in  FIG. 9 , rotating about rotation axis  123  in a plane parallel to roof reflecting surface intersection  151 . The rotation is similar to the oscillation, according to embodiment  10  of  FIG. 1 , and image  109  of point source  101  undergoes nearly a straight line trajectory. Shape of this trajectory can be varied by change of rotation axis position  123  relative to the rest of the projection optical system. Comparing embodiment  130  to state of the art mirror “polygon” mirrors, a much higher optical resolution of image  109  can be achieved owing to much higher numerical aperture of the beam than is practically achievable using polygon scanners.  FIG. 10  presents circular arrangement of multiple Amici prisms in position  105 , and another position  105 ″ on a rotating mechanical bearing disk  137  rotating about axis  123  as in embodiment  130 . High rotating speed of such a disc with a large number of scanning Amici prisms, allows creating of enormous number of pixels, much more than can be supplied for instant by state of art polygon “mirrors. 
         [0055]    Reference is now made to  FIG. 11  which illustrates an additional embodiment of the present invention. Point source  101  emits light rays which are imaged by imaging lens  103 , through Amici roof prism  105 , as scanning element. As presented in  FIG. 11 , a rotating scanning optical system is shown with Amici prisms  105  rotating about axis  123  similar to embodiment  130 . An additional optical relay lens  134 , performs re-imaging of intermediate image at  109  into final image  109 ′. As is mentioned above, trajectory of intermediate image  109  could deviate from a straight line. Optical relay  134  performs compensation of intermediate image trajectory deviation from straight line, therefore trajectory of final line will be located on plane  136 . 
         [0056]    An additional embodiment  80  of the present invention is illustrated in  FIG. 12 , of three-dimensional scanning in a transparent medium  147 . Three lenses  141 ,  143  and  145  are used for re-imaging light emitted from illuminating source  101  through Amici roof prism  105 , as scanning element. Lens  143  (shown in two position  143  an  143 ′) is movable along the optical axis, creating a change in depth of focusing plane  149  or z-scan inside the transparent media. The optical system is optimized for compensation of spherical aberration caused by medium  147 , at every depth of the focused beam  149  inside the transparent media  147 , by pre-calculating of spherical aberration of the optical system at every corresponding axial position of lens  143 . Lens  143  axial movement causes change of the focused beam position and scanning in depth is achieved as well as lateral scanning. Spherical aberration of the transparent medium  147  is strongly dependent on the depth of the focusing beam. Entire optical system spherical aberration is equal in magnitude, but opposite in sign, to the spherical aberration caused by penetrating of the beam into optical medium  147  and thus for the whole depth range. So, spherical aberration is balanced or canceled and the scanning in depth is not deteriorated appreciably by medium  147  spherical aberration. 
         [0000]    Two discrete positions of lens  143  and  143 ′ are shown in  FIG. 12  with corresponding positions of the focused beam  149  and  149 ′ and scanned layers  152  and  152 ′. 
         [0057]    Possible application of embodiment  80  are reading and writing of information in three dimensions. In embodiments of the present invention when F-number is low (or numerical aperture is high) of the scanning optical system, then the depth of focus inside transparent medium  147  is incredibly short. For example, if the optical system has F-number of 1, equivalent depth of focus for air (for λ/4 wave front deformation) is +/−2.44λ, meaning for visible light depth of focus is about ±1.2 micron. So, layers of information could be written in depth intervals of few microns. The information could be written by means modulation of amplitude, phase, spectrum, etc. 
         [0058]      FIG. 13  illustrates a new embodiment  90  which combines multiple continuously rotating Amici prisms  105  (embodiment  130 ) with scanning in depth, combined with embodiment  80  scanning in a three dimensional transparent medium  147 . As in embodiment  80 , three lenses  141 ,  143  and  145  are used for re-imaging light emitted from illuminating source  101  through Amici roof prism  105 , as scanning element. Lens  143  (shown in two position  143  an  143 ′) is movable along the optical axis, creating a change in depth of focusing plane  149  or z-scan inside the transparent media. Two discrete positions of lens  143  and  143 ′ are shown in  FIG. 13  with corresponding positions of the focused beam  149  and  149 ′ and scanned layers  152  and  152 ′. 
         [0059]      FIG. 14  illustrates a front view of a linear optical scanner  11 , according to an embodiment of the present invention. Light source  101  emits light rays which are imaged by an imaging lens  103 , through mirror structure  705 , as scanning element, to focusing point  107  at image plane  109 . Reference is now also made to  FIG. 15  of mirror structure  705 . Mirror structure  705  includes a plane of symmetry which includes an intersection  151  between the two mirror surfaces. The direction of scanning is perpendicular to the plane of symmetry. The mirror surfaces are produced using any production methods known in the art, such as but limited to vapor deposition of a metal, e.g. silver on a glass or metallic surface previously polished to optical surface quality. 
         [0060]      FIG. 16  illustrates embodiment  11  of the present invention from a side view. When mirror structure  705  is laterally translated along the direction of scanning at distance d, the optical ray path and direction remains unchanged and all rays are shifted parallel to the direction of translation by distance  2   d . Mirror structure is denoted by reference numeral  705  in the original position and by  705 ′ after a lateral translation along the direction of scanning. Consequently, initial image is at position  107  and image position shifted by  2   d  is denoted by  107 ′. Scanning of the image is performed mirror structure  705 , oscillating in the lateral direction. It is noteworthy that the use of a roof prism, e.g. Amici roof prism  105 , or mirror structure  705  for performing lateral scanning and the minimal optical path within the roof prism enable use of high numerical aperture objective lens  145  (low F-number). The use of low F-number optics in turn enable depth scanning of transparent media  147  and volume scanning when combined with one of the embodiments of the present invention for lateral scanning. 
         [0061]      FIG. 17  illustrates a method according to an embodiment of the present invention. First and second roof structures  105 , 705  are typically provided (step  21 ) with respective planes of symmetry of roof structures oriented perpendicularly to each other. The first roof structure is scanned (step  23 ) perpendicular to its plane of symmetry. Similarly, the second roof structure is scanned (step  25 ) perpendicular to its plane of symmetry so that two orthogonal scan directions are achieved. 
         [0062]    With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. 
         [0063]    Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. 
         [0064]    While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made.