Abstract:
A high efficiency projector apparatus comprising an illumination lens set including a first illumination lens and a second illumination lens, and the image is imaged conjugatedly on the image projection lens set, when light traveling distance between the first illumination lens of focal distance f1 and the second illumination lens of focal distance f2 is “d”, light source module produces first multiple virtual light sources on output side of light beam homogenization means, first multiple virtual light sources are located within f1 producing virtual image of second multiple virtual light sources on same side as the first multiple virtual light sources, the second multiple virtual light sources are distanced from the second illumination lens by value of D, the D value has value according to (f2&lt;D&lt;2f2), such that the second multiple virtual light sources are substantially conjugatedly imaged on the image projection lens set.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This utility application claims priority to Taiwan Application Serial 099103873, filed Feb. 9, 2010, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a projector apparatus, and in particular, to the light path design of pico projector apparatus. 
     2. Description of the Prior Art 
     In recent years, the projection apparatuses usually used by the corporate market are gradually getting into the household market or personal market. For applications of personal portable products, the volume size of projection apparatus and the efficiency of optical engine therein are important issues, and, more particularly, the specific angle of incidence required by the reflection-type image generator built in the projector apparatus needs to be considered to tradeoff between the volume size and the optical engine efficiency. 
     In order to reduce the size, the pico projector apparatus usually implements design of an LED light source module along with single light path. However, one of the drawbacks is insufficiency of brightness. To enhance the brightness, implementing two (or more) light source modules together with the dichroic combiner forming a single light path could not effectively reduce the volume of apparatus. For instance, the light combination techniques used by U.S. patent application No. US 2006/0279710 A1, US 2006/0164600 A1 or issued U.S. Pat. No. 6,644,814 B2 would result in a larger size of pico projector apparatus. Accordingly, it is desired to provide a pico projector apparatus which satisfy both requirements of smaller size and higher efficiency of optical engine. 
     To optimize the optical engine efficiency and volume size of pico projector apparatus at the same time, usually the following factors must be balanced: 1. Minimum of light paths, 2. Conjugate imaging of optical design, 3. Minimum folded size of light path. 
     SUMMARY OF THE INVENTION 
     A main objective of invention is to provide a projection apparatus or an optical module having an expected size of volume and an expected efficiency of optical engine. 
     The other objective of invention is to provide a pico projector apparatus or an optical module realizing the conjugate imaging. 
     Still another objective of invention is to provide a pico projector apparatus or an optical module having two LED light paths. 
     To reach the above objectives, in one embodiment of invention, a retro total reflecting type telecentric optical configuration is provided. 
     Specifically, the retro total reflecting type telecentric optical configuration includes a prism set, wherein the prism set includes a first prism. The first prism includes a main light inputting plane and a main light outputting plane, an intersecting angle between the main light inputting plane and a vertical reference plane being a first angle, an intersecting angle between the main light outputting plane and the vertical reference plane being a second angle. The first angle is about 28(±3) degrees and the second angle is about 32(±3) degrees, in order to meet the requirement as to the light incidence angle of reflection-type image generator. In addition, the height (thickness) (i.e., in Y direction) difference between the prism set and reflection-type image generator is reduced as well. 
     To achieve the above objectives, the projector apparatus of the embodiment of invention for projecting an image to a surface, comprising a light source module, a dichroic combiner, a light beam homogenization means, an illumination lens set, a reflection-type image generator, a prism set, and an image projection lens set. The light source module has a first light source, a second light source, a first light source modulation lens, a second light source modulation lens. The first light source becomes a first modulated light after going through the first light source modulation lens, and the second light source becomes a second modulated light after passing through the second light source modulation lens. The dichroic combiner combines the first modulated light and the second modulated light for generating a single first light path which defines a first direction. The light beam homogenization means functions to render the first light path uniformized. The illumination lens set functions to guide the uniformized first light path to a second light path. The reflection-type image generator forms the image and the prism set guides the second light path to the reflection-type image generator. A third light path having the image is formed after the reflection-type image generator reflects the second light path and the third light path is reflected by the prism set to form a fourth light path. The image projection lens set, located on the fourth light path, projects the image onto the surface. The light path formed by the second light source defining a second direction which is substantially perpendicular to the first direction. With respect to the second direction, the second light source is disposed between the first light source and the image projection lens set. Wherein, according to a predetermined imaging relationship, the light distributed on the light beam homogenization means is imaged conjugatedly on the image projection lens by the illumination lens. 
     Other than the first embodiment, the second embodiment of invention is a projector apparatus for projecting an image onto a surface, comprising: a light source module, a dichroic combiner, a light beam homogenization means, an illumination lens set, a reflection-type image generator, a prism set, and an image projection lens set. The light source module includes a first light source, a second light source, a first light source modulation lens, and a second light source modulation lens. The first light source irradiates the first light source modulation lens and outputs the first modulated light, the second light source irradiates the second light source modulation lens and output the second modulated light. The dichroic combiner generates a single first light path by combining the first modulated light and the second modulated light, and the first light path defines a longitudinal direction. The light beam homogenization means, inputting the first light path, performing uniformized effect over the first light path. The illumination lens set, inputting the uniformized first light path, redirects the uniformized first light path to a second light path, and an included angle is formed between the first light path and the second light path. The illumination lens set includes a first illumination lens, a direction guider and a second illumination lens. The direction guider functions to redirect the first light path to the second light path, and the focal distance of the first illumination lens is f 1 , the focal distance of the second illumination lens is f 2 . The reflection-type image generator forms the image and the prism set, inputting the second light path, projects the second light path to the reflection-type image generator. The reflection-type image generator generates a third light path having the image after reflecting the second light path. The third light path, after being reflected by the prism set, forms a fourth light path. The image projection lens set, located on the fourth light path, projects the image onto the surface. The light path emitted by the second light source defining a transverse direction which is substantially perpendicular to the first light path, and, with respect to the transverse direction, the second light source is located between the first light source and the image projection lens set. The illumination lens set, based on an imaging formula, renders the light distributed on the light beam homogenization means conjugatedly imaged on the image projection lens set. The effective focal distance of the first illumination lens and the second illumination lens is d, and the light source module generates a first multiple virtual light sources on an output side of the light beam homogenization means. The imaging relationship is: the first multiple virtual light sources are located within focal distance f 1  of the first illumination lens producing an virtual image of a second multiple virtual light sources on the same side as the first multiple virtual light sources, and the second multiple virtual light sources are distanced from the second illumination lens by value of D, wherein the D value has a value according to (f 2 &lt;D&lt;2f 2 ) such that the second multiple virtual light sources are substantially conjugatedly image on the image projection lens set. 
     According to one embodiment, the reflection-type image generator is a digital micromirror device having a plurality of micromirror units. Each of the micromirror units, responsive to a controlling signal, flips to different state with respect to an axis. 
     The above summary of the embodiments does not intend to cover all possible variations or alterations or every aspects of the present invention. 
     Under the core inventive spirit recited above, more specific embodiments can be contrived. 
    
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
       Each illustrated embodiment of the present invention will be fully understood with reference to the following description in details and the attached drawings. 
         FIG. 1  discloses a projector apparatus according to the first embodiment of the invention. 
         FIG. 2   a  discloses the first prism of  FIG. 1  in perspective view. 
         FIG. 2   b  discloses the right-side view of the first prism of  FIG. 2   a.    
         FIG. 2   c  discloses the top-side view of the first prism of  FIG. 2   a.    
         FIG. 3  shows that the lenslet on the first plane of the light beam homogenizer  120  is imaged on the image generator  160 . 
         FIG. 4  shows the first multiple virtual light sources at the output side of the light beam homogenizer  120  according to the invention. 
         FIG. 5  shows the third multiple virtual light sources formed at the input pupil of the projection lens set  170 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following exemplary embodiments of the present invention will be further described with reference to the attached drawings. While the present invention has been described with reference to exemplary embodiments, it is understood that various changes and modifications may be made and the invention is not limited to the disclosed exemplary embodiments that are use to enable persons skilled in the art to practice the present invention. 
     In the first embodiment of the present invention, it provides a projector apparatus for projecting an image onto a surface for people to view the content or information within the image. The projector apparatus may be a stand alone projector or an optical module integrated in a portable apparatus, such as a cellular phone, to become a portable multi-functional apparatus, such as a cellular phone with the function of pico projection. 
     In the following recitations, the so-called ┌light path┘ means the path on which the light (with or without image) traveling through and the light per se. The light per se might not include any information, or, due to some image processing operation, e.g. by the reflection-type image generator, the light might include the information to be projected and displayed. For easy understanding and readability for the figures in this specification, only the main light beam line on the light path is shown and other non-main light beam lines are not shown for brevity. 
     In the following recitations, the so-called ┌conjugate imaging┘ means the output pupil plane of an upstream (previous) optical lens is substantially imaged on the input pupil plane of a downstream (subsequent) optical lens. 
     As shown in  FIG. 1 , in the first embodiment of invention, a projector apparatus  100  includes a light source module  110  having a first light source (e.g. LED green light, G), a second light source (e.g. LED red light R and blue light, B), a first light source modulation lens (for example, collimator  115 A,  117 A), a second light source modulation lens (for example, collimator  115 B,  117 B). The first light source is converted to the first modulated light L 00 , after passing through the first light source modulation lens. Similarly, the second light source is converted to the second modulated light L 01 , after passing through the second light source modulation lens. 
     The projector apparatus  100  further includes a dichroic combiner  111 , for combining the first modulated light L 00  and the second modulated light L 01  to form a single first light path L 10 , wherein the single first light path L 10  defines a first direction as indicated in  FIG. 1 . The projector apparatus  100  further includes a light beam homogenization means (or, beam homogenizer)  120  for uniformizing the first light path L 10 . 
     The projector apparatus  100  further includes an illumination lens set  130 , inputting the uniformized first light path L 10 , for redirecting the first light path L 10  to a second light path L 13 . The first light path L 10  and the second light path L 13  intersects with each other at an included angle. 
     The projector apparatus  100  further includes a reflection-type image generator  160  for forming the image thereon and a prism set  140 , inputting the second light path L 13 , for projecting the second light path L 13  to the reflection-type image generator  160 . The reflection-type image generator  160 , after reflecting the second light path L 13 , forms a third light path L 15  having the image therein. The third light path L 15 , having the image, is totally reflected by the prism set  140  to generate a fourth light path L 17  with the image therein. 
     The projector apparatus  100  further includes an image projection lens set  170 , located on the fourth light path L 17 , for projecting the image in the fourth light path L 17  onto the surface. 
     As indicated in  FIG. 1 , to raise the brightness of light source, LED light source of the embodiment employs two-path light configuration. The LED G light constitutes one light path, and LED B light together with the LED R light constitutes another light path. The two light paths then go through the dichroic combiner  111 , which forms single first light path L 10 . 
     The first and second light source modulation lens ( 115 A,  117 A, and  115 B,  117 B) respectively input the light generated by G and (R, B) light source, and output the light path L 00 , L 01 . The first and second light source modulation lens ( 115 A,  117 A, and  115 B,  117 B) also provides a function to homogenize distributions of the angles of illumination. An embodiment of the first and second light source modulation lens includes a prior art collimator. 
     In one embodiment, the light path L 00  corresponding to first light source is substantially parallel to the first light path L 10 , and the light path L 01  corresponding to the second light source is substantially perpendicular to the first light path L 10 . The second light source along with the second light source modulation lens  115 B,  117 B is disposed between the first light source and the image projection lens set  170 , as shown in  FIG. 1 . 
     Under the embodiment shown in  FIG. 1 , the light beam homogenization means  120 , for example, includes a lenslet array which forms a light inputting plane  120 I and a light outputting plane  120 J. The light inputting plane  120 I is imaged on the reflection-type image generator  160 . As understood by persons skilled in this art the lenslet array includes a plurality of lenslets on a common plane, and each lenslet typically has an identical focal distance. 
     Under the embodiment shown in  FIG. 1 , the curvature radius of each lenslet of lenslet array, for example, is about smaller than 2 for better uniformization. After the first light path L 10  leaves the light beam homogenization means  120 , it irradiates onto the illumination lens set  130 , which redirects the first light path L 10  to a second light path L 13 . The first light path L 10  and the second light path L 13  intersects with each other at an included angle. 
     The illumination lens set  130  mainly includes an illumination lens  131 ,  135  and a direction guider  133 . The direction guider  133  functions to direct the first light path L 10  to a second light path L 13 . The direction guider  133  is, for example but not limited to, a reflecting surface. As known to persons skilled in the arts, the principle function of illumination lens  131 ,  135  is to minimize the unevenness of the intensity distribution of the light illumination. One embodiment for the illumination lens  131  or illumination lens  135  can be a conventional condenser lens, which aligns the main light beam line to be parallel to the light axis of the projector apparatus and, therefore, reduces the possible deviation of light. 
     Under the embodiment shown in  FIG. 1 , in one embodiment, the prism set  140  includes a first prism  141  having a main light input plane SB and a main light output plane SD, as shown in  FIGS. 2   a ,  2   b  and  2   c . An included angle between the main light input plane SB and a vertical reference plane SR is a first angle, an included angle between the main light output plane SD and the vertical reference plane SR is a second angle. The first angle is about 28 (±3) degrees, the second angle is about 32 (±3) degrees to meet the requirement for the light incidence angle of reflection-type image generator  160 . In one embodiment, the prism set  140  includes a second prism  143  which is a total internal reflection (TIR) prism. It is noted that the second light path L 13  passes through the first prism  141  first, and then is reflected by the reflection-type image generator  160  for retrieving the information to be projected. Afterwards, the third light path L 15  is formed and then totally reflected by the second prism  143 . Afterwards, the fourth light path L 17  is produced, and therefore the configuration in which the prism set  140  is applied is called as “retro total internal reflection telecentric” optical configuration. 
     As shown in  FIGS. 2   a ,  2   b ,  2   c  illustrating the embodiment for the first prism  141 , the light enters through the input plane SB and leaves from the output plane SD. The parameters disclosed and described above for the first prism  141  (and/or the second prism  143 ) are only preferred embodiments. Other equivalent parameters can be employed for satisfying the requirement of the light incidence angle of the reflection-type image generator  160 , and reducing the height (thickness) (i.e., in Y direction) difference between the prism set  140  and reflection-type image generator  160 . 
     Referring back to  FIG. 1 , in one embodiment under configuration of  FIG. 1 , the reflection-type image generator  160  for example can be a digital micromirrors device (DMD). The front side of reflection-type image generator  160  is typically provided with a field lens  150  which functions to increase the viewing angle. 
     Referring back to  FIG. 1  again, the third light path L 15  having the projection information therein is totally reflected by the second prism  143  to form the fourth light path L 17 . The fourth light path L 17  passes through the image projection lens set  170  which projects the information onto a surface. The image projection lens set  170  generally includes multiple lenses of different functions to achieve accurate magnification and projection. 
     In the followings, how to achieve the conjugate imaging by the optical design of this invention is explained with assistance of  FIGS. 3 ,  4  and  5 . 
     It is emphasized here that  FIG. 3  is a figure indicating the effective (equivalent) light path diagram of  FIG. 1 . From left to right, the light beam homogenization means (or, light beam homogenizer)  120 , the illumination lens  131 , the illumination lens  135 , the prism set  140 , the reflection-type image generator  160  are disclosed. It indicates the effective light traveling distance between the illumination lens  131  and the illumination lens  135  is “d”. In addition, in  FIG. 3 , it is also disclosed that the lenslet on input plane  120 I of the light beam homogenization means  120  is such designed that it is imaged on the reflection-type image generator  160 . In order to be imaged conjugately on the image projection lens set  170 , the effective light traveling distance “d” within the illumination lens set  130  must be effectively augmented. To advantageously utilize a space, which is resulted due to effective light traveling distance d, along a direction about perpendicular to light path L 10 , in the shown embodiment, the second light source (R, B) and the second light source modulation lens set ( 115 B,  117 B) are disposed between the first light source (G) and the image projection lens set  170 . 
       FIG. 4  discloses the first multiple virtual light sources at the output side  120 J of light beam homogenization means  120 . As the corresponding light emitted is modulated to become a substantial parallel light via the first and second light source modulation lens sets ( 115 A,  117 A,  115 B,  117 B), two light paths are combined by the dichroic combiner  111  into a first light path L 10 . The light produces a first multiple virtual light sources at the output side  120 J of homogenizer  120 . The first multiple virtual light sources are imaged on the vicinity of input pupil of illumination lens  131  and the first multiple virtual light sources are located within the focal distance (f 1 ) of first illumination lens  131 . This optical relationship produces a virtual image of a second multiple virtual light sources which, with respect to the first illumination lens  131 , are on the same side of the first multiple virtual light sources. In other word, the virtual image of second multiple virtual light sources are distanced from the second lens  135  by amount of D which is larger than “d”. In one embodiment, the imaging formula (relationship) is f 2 &lt;D&lt;2f 2 , wherein f 2  is the focal distance of the second illumination lens  135 , rendering the second multiple virtual light sources be substantially conjugated imaged on the image projection lens set. As a result, the configuration of embodiment of invention forms a third multiple virtual light sources at the vicinity of input pupil of image projection lens set  170 . 
       FIG. 5  shows the third multiple virtual light sources images formed at the input pupil of the image projection lens set  170 . 
     By the above detailed descriptions for the preferred embodiment, it is therefore understood that all objectives of the present invention are realized by those embodiments. In other words, via the retro total reflection telecentric optical configuration, the present invention can provide a smaller size projector apparatus or module which has higher optical engine efficiency. The present invention also realizes the conjugate imaging within the pico projector apparatus or module of the invention. The present invention also realizes two light paths of LED light within the pico projector apparatus or module. 
     While the present invention has been shown and described with reference to the preferred embodiments thereof and in terms of the illustrative drawings, it should not be interpreted as limited thereby. Various possible modifications and alterations could be conceived of by one skilled in the art to the form and the content of any particular embodiment, without departing from the scope and the spirit of the present invention. Such modifications or alternations are also the scope the following claims intend to cover.