200825609 九、發明說明： 【發明所屬之技術領域】 、本發明是關於一種投影機，尤其是一種具鋸齒型平面 .反射鏡之投影機。 .5【先前技術】 在重建並呈現影像之技術領域中，目前常見的顯示器 不外乎陰極射線官（CRT)顯示器、液晶顯示器、電漿 φ 顯示器等um顯示器、以及非固定尺寸之投影顯示 器。40时以下的家用尺寸，無疑地以液晶顯示器與電浆 10顯示器等平面顯示器在市場價格與接受度方面較具優 勢。另方面，若需要將影像資料放大至例如5〇吋以上之 較大區域時，-方面，固定尺寸平面顯示裝置之面板製造 難度大增，產品良率迅速下降，因此投產與製造成本大幅 提昇，預估此種工廠之造價約逹十億美元，並非一般企業 5所此輕易逹成，亚且，製造完成後之運輸成本與運輸過程 •之損壞率亦不可忽視。相反地’投影顯示器僅需改變螢幕 與機相之大小’無論電路板或光機本身尺寸均未明顯增 大’因此在大尺寸的顯示領域，仍以投影顯示器為主。 投影機依照其光機與顯示幕之相關位置，可被區分為 光機與觀賞者在顯示幕同側之前投式投影機，與光機藏在 顯示幕後方機箱的背投式投影機。對於背投式投影機，除 晝面亮度與解析度要高，另-個常被觀察的重點往往是機 箱所佔尺寸要盡可能微型化。亦即，當顯示幕 增大時，要在有限的最小厚声内，#6 取〗序度内，將先束正確投射於顯示 200825609 幕上之相對像素位置，並被精密聚焦呈現。 ^如圖1美國第6896375號發明專利所示，該背投式投 影機1具有一機箱（圖未示）、容置於機箱中之光機u、透 • 兄、12反射鏡組13、及顯示幕14。其中該顯示幕14 5具有如目2所示之一内外同心之多層菲埋耳透鏡听·i lens)結構包括内部全反射菲涅耳透鏡區i4i、透射區 142、傳統折射菲涅耳透鏡區143 ;且如圖3所示，該透 _ 鏡組包括一中繼透鏡（relaylens)組群121及一廣角透鏡組 群122,藉由廣角透鏡組群122將來自於光機u並穿過 1〇中繼透鏡組群121的受調制光束發散至一約153度之寬闊 立體角，最後由顯示幕14轉向至約垂直指向機箱前側。 然而，一方面顯示幕14之同心圓多層次溝槽結構精 緻且複雜，製作相當不易，另方面廣角透鏡組群122藉由 多個半徑漸增之凹透鏡，讓行經之光束立體角漸次發散過 15私中，卩现母一透鏡遠離鏡心位置之抛磨誤差遞增、以及受 • 到透鏡半徑增大而放大之誤差影響，在接近邊緣部分易形 成相差而較難正確聚焦。是以，此種大量運用非球面透鏡 之結構，將提高製程的困難度、降低良率、價格因而昂貴， 使該種投影機難以推廣。 20 此外，如圖4及圖5美國第6631994號發明專利所, 示，係利用一可造成正畸變（pincushicm distortion)之反射 鏡23，將入射光束依照入射角度不同而被分別反射；使 得反射鏡23上下端所反射光束間之夾角，比原先入射光 束間之夾角更大’達到約160度角。亦即，反射光束被大 6 200825609 幅分散，從而在一極短距離中，達成大幅放大原先光機 21所投射影像之目的，讓背投影電視之前後距離縮短， 以構成一薄形投影顯示器2。另如圖5，為補償該反射鏡 23造成如圖5(C)所示之影像正畸變，該發明揭露在反射 5 鏡23與光機21間，預先設置一造成如圖5(B)所示桶形畴 變（負畸變，barrel distortion)之透鏡組22，使得由光源20 經數位微鏡組（digital micro-mirror device; DMD)架樣之 光機21所投射出如圖5(A)所示的影像，先受到負畸變， 再由反射鏡正畸變而被正確形成如圖5(D)所示而顯示於 1〇 顯示幕24上。 為便於說明，圖6所示僅為一簡化圖例，其中，光機 31所投射出之所有光束僅以最上端及最下端兩束主光線 15200825609 IX. Description of the Invention: [Technical Field] The present invention relates to a projector, and more particularly to a projector having a sawtooth plane and a mirror. .5 [Prior Art] In the technical field of reconstructing and presenting images, the currently common displays are nothing more than cathode ray official (CRT) displays, liquid crystal displays, um displays such as plasma φ displays, and non-fixed size projection displays. Household sizes below 40 hours are undoubtedly superior in terms of market price and acceptance for flat panel displays such as liquid crystal displays and plasma 10 displays. On the other hand, if it is necessary to enlarge the image data to a large area of, for example, 5 〇吋 or more, the panel manufacturing of the fixed-size flat display device is greatly increased, and the yield of the product is rapidly decreased, so that the production and manufacturing costs are greatly increased. It is estimated that the cost of such a factory is about one billion US dollars, which is not easy for the general enterprise. The transportation cost and transportation process after the completion of the manufacturing process cannot be ignored. Conversely, the projection display only needs to change the size of the screen and the machine phase. The size of the circuit board or the optical machine itself is not significantly increased. Therefore, in the large-sized display field, the projection display is still dominant. According to the position of the light machine and the display screen, the projector can be divided into a projector that is placed on the same side of the display screen as the projector and the projector, and a rear projection projector hidden in the chassis behind the display screen. For rear projection projectors, in addition to the high brightness and resolution of the kneading surface, another often observed focus is often on the size of the chassis to be as miniaturized as possible. That is, when the display screen is enlarged, within the finite minimum thick sound, within the #6 取〗, the first beam is correctly projected onto the relative pixel position on the screen of the display 200825609, and is accurately focused. As shown in FIG. 1 of the US Pat. No. 6,896,375, the rear projection projector 1 has a casing (not shown), a light machine u housed in the casing, a transparent brother, a 12 mirror group 13, and Display screen 14. The display screen 14 5 has a multi-layered inner and outer concentric lens, including an internal total reflection Fresnel lens area i4i, a transmissive area 142, and a conventional refractive Fresnel lens area. 143; and as shown in FIG. 3, the lens group includes a relay lens group 121 and a wide-angle lens group 122, and the wide-angle lens group 122 will be from the optical machine u and pass through The modulated beam of the relay lens group 121 is diverged to a wide solid angle of about 153 degrees, and finally turned by the display screen 14 to be directed approximately perpendicularly to the front side of the chassis. However, on the one hand, the multi-level groove structure of the concentric circle of the display screen 14 is exquisite and complicated, and the fabrication is quite difficult. On the other hand, the wide-angle lens group 122 has a plurality of concave lenses with increasing radius, so that the beam solid angle of the passing beam gradually diverges 15 In private, the throwing error of the mother-lens lens away from the center of the lens is increased, and the error caused by the enlargement of the lens radius is easy to form a phase difference near the edge and it is difficult to focus correctly. Therefore, such a large-scale use of an aspherical lens structure will increase the difficulty of the process, lower the yield, and the price is expensive, making it difficult to promote such a projector. In addition, as shown in FIG. 4 and FIG. 5, the invention patent of US Pat. No. 663,1994 shows that the incident light beam is separately reflected according to the incident angle by using a mirror 23 which can cause a pincushicm distortion; The angle between the reflected beams at the upper and lower ends of the mirror 23 is larger than the angle between the original incident beams and reaches an angle of about 160 degrees. That is to say, the reflected beam is dispersed by the large 6 200825609 image, thereby achieving the purpose of greatly enlarging the image projected by the original optical machine 21 in a short distance, so that the back projection television is shortened before and after to form a thin projection display 2 . As shown in FIG. 5, in order to compensate the mirror 23, the image is orthodontic as shown in FIG. 5(C), and the invention is disclosed between the reflection mirror 23 and the optical machine 21, and a preset is caused as shown in FIG. 5(B). The lens group 22 of the barrel distortion is shown to be projected by the light source 20 through a digital micro-mirror device (DMD)-like optical machine 21 as shown in FIG. 5 (A). The image shown is negatively distorted first, and then correctly deformed by the mirror to be correctly formed as shown in Fig. 5(D) and displayed on the 1 〇 display screen 24. For convenience of explanation, FIG. 6 is only a simplified illustration in which all the light beams projected by the optical machine 31 are only the uppermost and lowermost two main rays 15
35、36作為代表，且將反射鏡33之反射暫時忽略，而將 顯示幕鏡射虛擬搬移至反射鏡33後方之位置34。在此， 將被投射至顯示幕最下方之主光線稱為第一光束，其行進 路線較接近光軸， ·將被投射至顯示幕最上方之主光線稱為 第二光束，其行進路線關與綠夾—較大傾斜角度。 ^备以透鏡組32作為區分，可以發現透鏡組32上游· 弟-光束35、第二光束36、與光機31之投射面大致呈: 一較小之第一三角形。相對地，在透鏡組32下游，第， 光束35，、第二光束36，、及顯示幕34亦構成-較大之: —二角形。基於透鏡組32之光程補償效果，第二三心 p不幕34可以虛線位置34’標示。由此，可以發現第. 與補償後之第二三角形為相似形，亦即，依照 20 200825609 型’由光機31投射面射出之影像，將可被大致清晰呈現 於該顯示幕。此結構巧妙地運用與顯示幕呈傾斜方向行進 之發散光束，並以非平面反射鏡33將發散角更增大，確 實有效縮短投影顯示器之厚度。 5 另方面，若以遠心系統之液晶裝置作為空間調制裝置 的光機’因為液晶裝置僅能調制垂直入射極化光之透光 率’至於斜向入射之光束將造成漏光現象，無法被有效阻 • 絕’因此’無法採用斜向之入射或反射光束。如圖7所示， 當此種遠心系統光機41下端投射主光線之第三光束45與 10上端投射主光線之第四光束46彼此平行，即使同樣進入 透鏡組42 ’並被非球面反射鏡43反射至顯示幕44，但因 為第四光束之光程明顯不同於圖6的第二光束，致使透鏡 組42上游無法構成一三角形，更遑論與下游之光束45,、 46、及44’構成之三角、形形成一相似形；致使此種遠心系 15統無法適用於上述架構。亦因此，該結構中所運用之傾斜 • 方向行進之光束，僅能採用例如DLP架構之光機，無法 被推廣至遠心系統之具液晶板光機架構。 尤其，上述正畸變反射鏡受限於其特殊形狀，最接近 顯示幕之鏡心位置與最遠離顯示幕之角落位置，相對於顯 20 幕之垂直距離可差距約十公分，一方面造成投影機本身 f度無法順利進-步縮減，迫使投影顯示器較等離子顯示 时等跳爭商。口之整體厚度超過兩倍；另方面，正畸變之反 射鏡與桶形畴變之透鏡組群在組裝與調校具有相當困難 度’亦因此使其良率不易提升。 8 200825609 【發明内容】 因此，本發明之目的在提供一種具鋸齒型平面反射鏡 之投影機，使得薄形投影機採用遠心系統光機成為可行。 本發明之另一目的在提供一種運用鋸齒型平面反射 5鏡，使結構單純化，組裝簡便的具鋸齒型平面反射鏡之投 影機。 又 本發明之再一目的在提供一種運用鋸齒型平面反射 _ 鏡，使投影機整體厚度大幅縮減的具鋸齒型平面反射鏡之 投影機。 1〇 故本發明之具鋸齒型平面反射鏡之投影機，包含：一 顯不幕，一對應於該顯示幕、具有一基面及相反於該基面 並具複數自一基點發散而沿一軸線對稱的弧形作甩區之 一鋸齒面、且該基面及該鋸齒面之一的表面上塗佈有一反 射層之鋸齒型平面反射鏡，其中除對應該基點之弧形作用 I5區，各弧形作用區分別具有一面向該基點之向斜部、一背 _ 向該基點之背斜部、一向斜部與背斜部相鄰接之近顯示幕 〒、及向斜部/背斜部與相鄰作用區背斜部/向斜部相鄰接 之遠顧示幕帶，各該近顯示幕帶與遠顯示幕帶之高度差係 逖小於該鋸齒面之任一邊長；一與該鋸齒型平面反射鏡組 20夾一角度之一初級反射鏡；及一具遠心系統空間調制裝置 而用以經該初級反射鏡轉向並經該鋸齒型平面反射鏡而 投射一被調制光束至該顯示幕之光機。 由於錯齒型平面反射鏡之厚度甚薄，即近顯示幕帶與 遂顯不幕帶與顯示幕距離差甚小，光束行經後方鋸齒型平 9 200825609 面反射鏡組至顯示幕的光程差因而受到明顯抑制，不易產 生正畸變，從而撇除需以桶形畸變預先補償之需求，使得 整體組裝結構簡化，降低製程難度及製造成本，有效提升 良率；並且由於該反射鏡之厚度甚薄，可以大幅減少投影 5機整體外殼厚度，使產品大幅微型化與精緻化；並可解決 斜向投射時，鏡頭組上游光束主光線彼此平行、而下游之 光束主光線彼此傾斜所造成之相差，使遠心系統光機可被 ❿ 順利運用於此種具有非球面反射鏡組，並被傾斜投射於顯 示幕之投影機。 10【實施方式】 本發明的技術内容、特徵與達成效果，配合以下參考 圖與對應的較佳貫施例詳細說明，將可被清楚顯現。 .本案投影機第一較佳實施例之結構如圖8所示，依序 包含一遠心系統光機51、——透鏡組群52、一初級反射鏡 15 53、一鋸齒型平面反射鏡組54、及一顯示幕55。 _ 其中’長方形的鑛齒型平面反射鏡組54如圖9所示， 係以一拋物面鏡為基礎，定與拋物面540相對的平坦面為 一基面541 ’並以垂直於該基面541的撖物面540對稱軸 線542、及對稱轴線542與基面541交會的基點5420為 20準，以同心圓柱面例如標號543、544所示者切割該拋物 面540，構成如標號545、546、547等之複數弧形面，並 省略每一同心圓柱範圍内，接近基面541之平行區域 545’、546’、547’，使得弧形面 545、546、547 向基面 541 内縮，形成如標號545”、546，，、547，，之弧形作用區。 200825609 而如圖10在各弧形作用區545”、546”、547”遠離基 面541側，則由各作用區545”、546”、547”面向該基點 5420之向斜部5451”、5461”、5471”與背向該基點5420 之背斜部5452”、5462”、5472”共同構成一鋸齒面548。 5 在本例中，一反射層549係被鍍設於鋸齒面548上，並為 保護反射層結構549，在其前方設置一保護層。 由於本例中各向斜部5451”、5461”、5471”與對應背 斜部5452”、5462”、5472”相鄰接之近顯示幕帶5450”、 5460”、5470”實質上位於平行基面541之同一平面上，使 10 得本例中鋸齒型平面反射鏡組54整體大致呈一平面狀。 另方面，近顯示幕帶5450”、5460”、5470”與接近基面541 而遠離顯示幕之遠顯示幕帶5450’、5460’、5470’間之高 度差遠小於反射鏡組54及該鋸齒面548之任一邊長，亦 使得鋸齒型平面反射鏡組54雖具有拋物面鏡之光學性 15 質，但整體厚度得以大幅縮減。 當然，由於實際形成之鋸齒狀的向斜部與背斜部尺寸 均甚小，相鄰同心圓之間距並非必須遞減，亦可因特殊之 反射效果規劃而呈現疏密排列。且因來自光機之被調制光 束受到初級反射鏡53轉向後，鋸齒型平面反射鏡組54是 2〇 以平行於顯示幕55之方向設置，若投影機之機殼大致為 長方體，則顯示幕55與鋸齒型平面反射鏡組54恰可平行 組裝於殼體前後側，組裝相當容易、良率因而提高。更由 於鋸齒型平面反射鏡甚薄，即近顯示幕帶及遠顯示幕帶與 顯示幕距離差甚小，光束行經後方鋸齒型平面反射鏡組至 11 200825609 顯示幕的光程差因而明顯縮減，大幅減輕所產生之正崎 變，從而免除以桶形畸變透鏡預先補償之需求，使得整體 組裝結構簡化，降低製程難度及製造成本。 並如圖11所示，受鋸齒型平面反射鏡組54向斜部與 5背斜部之構型影響，來自初級反射鏡53之入射光束在受 反射後，並非依循與原入射角相等之反射角，朝向顯示幕 55行進，反之，當入射角'度為5〇至69度，反射之角度 φ 則被擴張至6〇至79度，使得影像資料放大效果益形顯 著，反射鏡組54與顯示幕55間之距離從而可以更進一步 10 縮短。 田然，如热於此技術者所能輕易理解，反射層並非必 須設置於鋸齒型平面反射鏡組面向顯示幕側，亦可如圖 12所示，將反射層649設置於鋸齒型平面反射鏡組64背 離顯示幕側，使得來自光機之光束係在鋸齒型平面反射鏡 15組649内往返後，再被投射至顯示幕上。 • 歸納上述，本發明具鋸齒型平面反射鏡組之投影機， 確實能將反射鏡組整體扁平化、降低其所造成之光程差、 並減少因該光程差而導致之畸變，達成簡化整體投影機結 構而降低成本、使組裝更容易而提升產品良率、縮減產品 2〇整體厚度之功效，更使採用遠心結構之光機成為可能，由 本發明揭露之技術確實能達到本案前述目的。惟以上所述 者，僅為本發明之較佳實施例而已，不能僅以此實施例之 揭露限定本發明實施之範圍；凡依本發明申請專利範圍及 說明書内容所作之簡單的等效變化與修飾，仍屬本案涵蓋 12 200825609 之範圍。 【圖式簡單說明】 圖1是美國第6896375號發明專利之結構示意圖。 圖2是圖1之顯示幕結構示意圖。 5 圖3是圖1之光機與鏡頭組結構示意圖，說明廣角透 鏡組群之角度擴散效果。 圖4是美國第6631994號發明專利之結構示意圖。 _ 圖5是圖4各光學元件組對通過影像之形變狀況示意 圖〇 1〇 圖6是圖4結構對應非遠心系統光機之示意圖，說明 該結構適用原理。 圖7是圖4結構對應遠心系統光機之示意圖，說明該 結構何以不適用遠心系統。 圖8是本案投影機第一較佳實施例之結構正視示意 15 圖。 _ 圖9是本案具鋸齒型反射鏡組之側視示意圖，說明其 構成。 圖10是本案具鋸齒型反射鏡組之結構示意圖。 圖11疋本案鋸齒型反射鏡組之反射方式示意圖。 2 0 圖12疋本案具鋸齒型反射鏡組第二較佳實施例側剖 視示意圖。 13 200825609 【主要元件符號說明】 1…背投式投影機 2…投影顯示器 U、2卜3卜4卜51·"光機 5 12、22、32、42、52…透鏡組 13…反射鏡組 14、24、34、34， 、44、44’ 、55···顯示幕 20…光源 23、33、43、53…反射鏡 • 10 35、36、35， 、36， 、45、46、45， 、46，…光束 54、64…鑛齒型平面反射鏡組 ’ 121···中繼透鏡組群 122…廣角透鏡組群 141…内部全反射菲涅耳透鏡區 142…透射區 15 143…傳統折射菲涅耳透鏡區 540…拋物面 541…基面 542…轴線 · 543、544…切割 545、546、547…孤形面 ^ 548…錯齒面 549、649…反射層 W 20 545’ 、546’ 、547’ …平行區域 545” 、546” 、547”…弧形作用區 5 4 2 0…基點 5450’ 、5460’ 、5470’…遠顯示幕帶 5450” 、5460” 、5470”…近顯示幕帶 25 545Γ 、546Γ 、5471” …向斜部 5452” 、5462” 、5472” …背斜部 1435, 36 is representative, and the reflection of the mirror 33 is temporarily ignored, and the display mirror is virtually moved to the position 34 behind the mirror 33. Here, the chief ray to be projected to the bottom of the display screen is referred to as the first light beam, and the traveling path is closer to the optical axis. The chief ray to be projected to the uppermost position of the display screen is referred to as the second light beam, and the traveling route is closed. With green clips - a larger angle of inclination. With the lens group 32 as a distinction, it can be found that the upper surface of the lens group 32, the beam 35, the second beam 36, and the projection surface of the optical machine 31 are substantially: a smaller first triangle. In contrast, downstream of the lens group 32, the first, the light beam 35, the second light beam 36, and the display screen 34 also constitute - larger: - a dihedron. Based on the optical path compensation effect of the lens group 32, the second three-core p-34 can be indicated by a dashed line position 34'. Thus, it can be found that the second triangle is similar to the compensated second triangle, that is, the image projected by the projection surface of the optical machine 31 in accordance with 20 200825609 can be substantially clearly presented on the display screen. This structure subtly uses the divergent beam that travels in an oblique direction with the display screen, and increases the divergence angle by the non-planar mirror 33, effectively reducing the thickness of the projection display. 5 On the other hand, if the liquid crystal device of the telecentric system is used as the optical device of the spatial modulation device, 'the liquid crystal device can only modulate the transmittance of the vertically incident polarized light', and the obliquely incident beam will cause light leakage, which cannot be effectively blocked. • It is absolutely impossible to use an obliquely incident or reflected beam. As shown in FIG. 7, when the third beam 46 of the main beam of the main beam and the fourth beam 46 of the main beam projected at the lower end of the telecentric system illuminator 41 are parallel to each other, even if they enter the lens group 42' and are aspherical mirrors. 43 is reflected to the display screen 44, but since the optical path of the fourth beam is significantly different from the second beam of Fig. 6, the upstream of the lens group 42 cannot form a triangle, let alone the downstream beams 45, 46, and 44' The triangle forms a similar shape; thus the telecentric system cannot be applied to the above structure. Therefore, the beam used for the tilting direction in the structure can only be used with a light machine such as a DLP structure, and cannot be extended to a liquid crystal panel optical system of a telecentric system. In particular, the above-mentioned orthodontic mirror is limited by its special shape, and the position of the mirror center closest to the display screen and the corner position farthest from the display screen can be about 10 cm apart from the vertical distance of the display screen, and the projection is caused on the one hand. The f-degree of the machine itself cannot be smoothly stepped down, forcing the projection display to compete with the plasma display. The overall thickness of the mouth is more than twice; on the other hand, the orthodontic mirror and the barrel-shaped domain lens group are quite difficult to assemble and adjust, which makes the yield difficult to increase. 8 200825609 SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a projector having a sawtooth type planar mirror that makes it possible to use a telecentric system optical machine for a thin projector. Another object of the present invention is to provide a projector having a sawtooth type flat mirror using a sawtooth type planar reflection mirror to simplify the structure. Still another object of the present invention is to provide a projector having a sawtooth type flat mirror using a sawtooth type planar reflection mirror to greatly reduce the overall thickness of the projector. The projector of the present invention has a sawtooth type flat mirror, comprising: a display, a corresponding to the display screen, having a base surface and opposite to the base surface and having a plurality of base points diverging along a The axis-symmetric arc is a serrated surface of the crotch region, and the surface of one of the base surface and the serrated surface is coated with a reflective layer of a sawtooth-type plane mirror, wherein the arc region of the corresponding base point acts on the I5 region, Each of the arc-shaped action regions has a slanting portion facing the base point, an anticline portion facing the base point, a near display curtain adjacent to the oblique portion and the anticline portion, and a slanting portion/anticline The portion is adjacent to the adjacent oblique portion/inclined portion of the adjacent active area, and the height difference between each of the near display screen and the far display screen is smaller than either side of the sawtooth surface; The sawtooth type planar mirror group 20 sandwiches an angle of a primary mirror; and a telecentric system spatial modulation device for steering through the primary mirror and projecting a modulated beam through the sawtooth type planar mirror Display screen light machine. Since the thickness of the wrong-toothed planar mirror is very thin, that is, the difference between the distance between the near-display screen and the display screen and the display screen is very small, and the beam path passes through the rear sawtooth type flat 9 200825609 surface mirror group to the display screen optical path difference Therefore, it is obviously suppressed, and it is not easy to produce orthodontics, thereby eliminating the need for pre-compensation with barrel distortion, which simplifies the overall assembly structure, reduces the process difficulty and manufacturing cost, and effectively improves the yield; and because of the thickness of the mirror Thin, can greatly reduce the thickness of the overall casing of the projection 5 machine, so that the product is greatly miniaturized and refined; and can solve the difference between the main rays of the upstream beam of the lens group and the main rays of the downstream beam when the oblique projection is oblique. Therefore, the telecentric system light machine can be successfully applied to such a projector with an aspherical mirror group and obliquely projected on the display screen. [Embodiment] The technical contents, features, and effects of the present invention will be apparent from the following detailed description of the preferred embodiments. The structure of the first preferred embodiment of the projector of the present invention is as shown in FIG. 8, and includes a telecentric system optical machine 51, a lens group 52, a primary mirror 153, and a sawtooth type planar mirror group 54. And a display screen 55. _ wherein the 'rectangular orthodontic plane mirror group 54 is based on a parabolic mirror, and the flat surface opposite to the paraboloid 540 is a base surface 541' and is perpendicular to the base surface 541. The symmetry axis 542 of the object plane 540 and the base point 5420 where the axis of symmetry 542 intersects the base surface 541 are 20, and the paraboloids 540 are cut by concentric cylindrical faces such as those indicated by reference numerals 543, 544, such as reference numerals 545, 546, 547. Waiting for the plurality of curved faces, and omitting the parallel regions 545', 546', 547' of each of the concentric cylinders, close to the base surface 541, such that the curved faces 545, 546, 547 are retracted toward the base face 541, forming as The arcuate action area of the reference numeral 545", 546, 547, 547, 200825609 and as shown in Fig. 10, in the arc-shaped action areas 545", 546", 547" away from the base surface 541 side, the respective action areas 545", 546", 547", the inclined portion 5451", 5461", 5471" facing the base point 5420, and the anticlines 5452", 5462", 5472" facing away from the base point 5420 together form a serrated surface 548. 5 In this example A reflective layer 549 is plated on the serrated surface 548 for protection of the reflective layer 549, a protective layer is disposed in front of it. Since the oblique portions 5451", 5461", and 5471" in this example are adjacent to the corresponding anticline portions 5542", 5462", 5472", the adjacent display screen 5450", 5460", 5470" are substantially on the same plane of the parallel base surface 541, so that the sawtooth type planar mirror group 54 in this example has a substantially planar shape as a whole. On the other hand, the height difference between the display screens 5450", 5460", 5470" and the near base surface 541 and away from the display screen is far smaller than the mirror group 54 and the sawtooth. The length of either side of the face 548 also makes the sawtooth type planar mirror group 54 have the optical properties of the parabolic mirror, but the overall thickness is greatly reduced. Of course, due to the actually formed zigzag oblique and anticline dimensions They are very small, the distance between adjacent concentric circles does not have to be decremented, and they can be arranged in a dense arrangement due to the special reflection effect planning. Since the modulated beam from the optical machine is turned by the primary mirror 53, the zigzag plane mirror The group 54 is 2〇 arranged in a direction parallel to the display screen 55. If the casing of the projector is substantially rectangular, the display screen 55 and the sawtooth type flat mirror group 54 can be assembled in parallel to the front and rear sides of the casing, and the assembly is relatively easy. The yield is thus improved. Moreover, since the sawtooth type flat mirror is very thin, that is, the distance between the near display screen and the far display screen and the display screen is very small, and the beam passes through the rear sawtooth type flat mirror group to 1 1 200825609 The optical path difference of the display screen is thus significantly reduced, greatly reducing the positive change caused by the correction, thereby eliminating the need for pre-compensation of the barrel distortion lens, which simplifies the overall assembly structure, reduces the process difficulty and manufacturing cost. It is shown that the configuration of the sawtooth type planar mirror group 54 is inclined to the oblique portion and the fifth oblique portion. After the incident light beam from the primary mirror 53 is reflected, it does not follow the reflection angle equal to the original incident angle, and faces the display screen. 55 travels, conversely, when the incident angle 'degree is 5 〇 to 69 degrees, the angle φ of the reflection is expanded to 6 〇 to 79 degrees, so that the image data amplification effect is significant, and between the mirror group 54 and the display screen 55 The distance can be further shortened by 10. Tian Ran, as can be easily understood by those skilled in the art, the reflective layer does not have to be disposed on the side of the sawtooth-type planar mirror facing the display screen, as shown in Fig. 12, the reflective layer can also be The 649 is disposed on the side of the display screen from the sawtooth type planar mirror group 64 such that the light beam from the optical machine is reciprocated within the set 649 of the sawtooth type planar mirrors 15 and then projected onto the display screen. • In summary, the projector of the present invention has a sawtooth type flat mirror group, which can flatten the entire mirror group, reduce the optical path difference caused by it, and reduce the distortion caused by the optical path difference, thereby simplifying The overall projector structure reduces the cost, makes the assembly easier, improves the product yield, reduces the overall thickness of the product, and makes the optical machine using the telecentric structure possible. The technology disclosed by the present invention can achieve the foregoing objectives. The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited by the disclosure of the embodiments; the simple equivalent changes made by the scope of the invention and the contents of the description of the present invention are Modifications are still covered by this case in the 12 200825609. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the structure of the invention patent No. 6,896,375. 2 is a schematic view showing the structure of the display screen of FIG. 1. 5 Figure 3 is a schematic view showing the structure of the optical machine and the lens unit of Figure 1, illustrating the angular diffusion effect of the wide-angle lens group. Fig. 4 is a schematic view showing the structure of the invention patent No. 6631994. _ Fig. 5 is a schematic diagram of the deformation of the optical component group of Fig. 4 through the image. Fig. 6 is a schematic view of the structure of Fig. 4 corresponding to the non-telecentric system optomechanism, illustrating the principle of application of the structure. Figure 7 is a schematic view of the structure of Figure 4 corresponding to a telecentric system optomechanical machine, illustrating why the structure does not apply to telecentric systems. Figure 8 is a front elevational view of the first preferred embodiment of the projector of the present invention. Figure 9 is a side elevational view of the sawtooth type mirror assembly of the present invention, illustrating its construction. Figure 10 is a schematic view showing the structure of the sawtooth type mirror group of the present case. Fig. 11 is a schematic view showing the reflection mode of the sawtooth type mirror group of the present invention. 2 0 is a side cross-sectional view showing a second preferred embodiment of the sawtooth type mirror set of the present invention. 13 200825609 [Description of main component symbols] 1... Rear projection projector 2... Projection display U, 2 Bu 3 Bu 4 Bu 51·"Optical machine 5 12, 22, 32, 42, 52... Lens group 13...Mirror Groups 14, 24, 34, 34, 44, 44', 55... Display screens 20... Light sources 23, 33, 43, 53... Mirrors • 10 35, 36, 35, 36, 45, 46, 45, 46, ... beam 54, 64... orthodontic plane mirror group '121···relay lens group 122...wide-angle lens group 141...internal total reflection Fresnel lens area 142...transmission area 15 143 ...conventional refracting Fresnel lens area 540...paraboloid 541...base surface 542...axis · 543, 544...cut 545, 546, 547... solitary surface ^ 548... wrong tooth surface 549, 649... reflection layer W 20 545' , 546', 547' ... parallel area 545", 546", 547"... arc action area 5 4 2 0... base point 5450', 5460', 5470'... far display screen 5450", 5460", 5470"... Near display screen 25 545Γ, 546Γ, 5471" ... oblique portion 5542", 5462", 5472" ... anticline 14