CN201499208U

CN201499208U - Image scanning module with five reflectors

Info

Publication number: CN201499208U
Application number: CN2009201560166U
Authority: CN
Inventors: 赖艾莲; 林清源; 徐三伟
Original assignee: E Pin Optical Industry Co Ltd
Current assignee: E Pin Optical Industry Co Ltd
Priority date: 2009-05-15
Filing date: 2009-05-15
Publication date: 2010-06-02
Anticipated expiration: 2019-05-15

Abstract

The utility model discloses an image scanning module with five reflectors, which comprises at least one light source, the five reflectors, an imaging lens group, an image senor and a rack. At least two reflectors can reflect the image of a document to be scanned at least more than twice and meet a specific optical condition. Due to the arrangement of angles of the five reflectors, when adjusting the length of a total optical path according to requirement, such as adjusting the scanning size of the document, only the distances of the five reflectors need to be adjusted, without adjusting the angles of the five reflectors. Furthermore, the image scanning module not only can increase the length of the optical path and improve the depth of field in a limited space, but also has assembly convenience, thereby being suitable for the image scanning modules with various different lengths of the optical paths.

Description

Image scanning module with five reflectors

Technical Field

The present invention relates to an image scanning module with five reflectors for multiple reflection of scanning beams, and more particularly to an image scanning module with five reflectors for use in a flatbed scanner (flatbed scanner) or a multi-function machine (multi-function printer) and other related devices.

Background

Scanners, particularly image scanners, have become important computer-related products in recent years, and image scanners can capture images of documents, text pages, photographs, films, even flat articles, and the like. The image capturing method is to project light onto the document to reflect the document into image beam, then to reflect the image beam by multiple reflectors to change its optical path, and finally to focus the image on the image sensor by the image capturing lens set for image sensing. Because the documents are mostly composed of characters, images or characters and images and have areas with different light and shade, the reflected image beams have different intensities according to different irradiation positions. After the image beam is focused on a CCD image sensor (CCD, Charge-Coupled Device) or a CMOS image sensor (CMOS), the photosensitive element converts the focused image beam into a corresponding photo-electric signal, and then the scanning software reads in data to form a digital image. The scanned image may be stored in a magnetic device (e.g., a hard disk) or an optical device (e.g., an optical disk). The standardized and common Image storage methods include a Tagged Image File Format (TIFF), an Encapsulated PostScript (EPS), a Bitmap Image File Format (BMP), a Graphics Interchange Format (GIF), and a computer Graphics Interchange Format (PCX). Commercially available scanners, such as Flat-bed scanners, are used to scan photographs or printed matter, etc. The scanner is provided with a glass light-transmitting plate for placing a file to be scanned, and the image scanning module moves through the track and converts the image of the file into digital data in a row mode, which is the most commonly used scanner. Scanners made by similar principles, such as multi-function printers (multifunction-function printers) and other related devices, scan by relative movement of a document and an image scanning module.

Referring to fig. 1, fig. 2 and fig. 3, schematic diagrams of various prior art image scanning module structures and optical path arrangements are shown, respectively. The image scanning module 91 includes a transparent plate 12, a frame 13, an image sensor 14, a lens assembly 15, a light source 16 and a reflector 917. The light source 16 emits light to illuminate the document 2 to be scanned, and the light is reflected to form an image beam, which changes its direction and path through the reflective mirror 917 disposed at different positions and angles, and then enters the image capturing lens assembly 15 and the image sensor 14. With the demands of users and the progress of related manufacturing technologies, the image scanning module 91 is increasingly thin and small, and the volume and the internal component installation space of the image scanning module 91 are smaller and smaller. In the limited space of the image scanning module 91, for the image capturing lens assembly 15 and the image sensor 14 with the same resolution, the multi-surface mirror is disposed to make the scanning light reflected for multiple times and then incident to the image scanning module to lengthen the optical distance (optical distance), thereby increasing the depth of field (depth of field). Although this method can obtain a better image for scanning an uneven document 2, such as a document with wrinkles, the image beam reflected by the document may generate stray light (overlapped light beam), which may enter the image capturing lens assembly 15 after repeated reflection, and may overlap with the original image to form a ghost image (ghost image). The prior art discloses different solutions, such as US patents US5,815,329, US6,170,651, US6,421,158, US6,227,449, US2008/0007810, US 2008/0170268; japanese patents JP6006524, JP2005-328187, JP 2004-274299; british patent GB 2317293; taiwan patent TW476494, etc. As shown in FIG. 1, 4 mirrors 917 are used, each mirror 917 reflecting an image beam once; as shown in FIG. 2, 3 mirrors 917 are used, of which 2 mirrors 917 reflect the image beam twice. As shown in FIG. 3, 5 mirrors 917 are used to reflect the image beam twice, 1 mirror 917 is used to have a non-reflective material in between to avoid the reflection of stray light; or limiting the mirror surface angle of the first mirror, as in US2008/0084625, etc.; the purpose of this angle limitation is to avoid stray light rays entering the long and wide mirror.

In the prior art, when the total optical length (TTL) of the image capturing lens group is changed for different Effective Focal Lengths (EFLs), or when the image scanning module is applied to scanners of different manufacturers, or the scanning size of the scanner is changed, the scanner such as a4/A3 must rearrange the distance and angle of each mirror. However, in a limited space, in addition to adjusting the angle and position of each mirror to be focused by the image capturing lens assembly, the angle and position of each mirror should be adjusted to reduce the ghost phenomenon in the limited space. In order to be widely applied to the above different conditions, in the prior art, the scanning module must rearrange the angle and position of the mirror, and even change the optical path of the mirror. This adjustment would result in the frame having to be re-molded, which increases the manufacturing cost. In addition, during assembly, the reflection angles of a large number of reflectors are adjusted to meet the light path and eliminate ghost images, so that the assembly cost is difficult to reduce, and the use is limited and inconvenient. Therefore, there is a need to develop an image scanning module with simple and minimum mirror adjustment for use in scanners of different manufacturers, scanners of A4/A3 size, or image capturing lens groups with different effective focal lengths, total optical length (TTL), etc.

SUMMERY OF THE UTILITY MODEL

The present invention is directed to solve the above problems, and an object of the present invention is to provide an image scanning module with five reflectors having multiple reflection effects to increase the depth of field and solve the problem of applicability of the prior art.

In order to achieve the object, the utility model provides an image scanning module of five speculum multiple reflections mainly will treat the image of the file of scanning through five speculums reflection change its direction and route, increase the optical path to through arranging of five speculum angles, avoid stray light to get into and get for instance the optical lens group, with the reduction ghost phenomenon. The utility model provides an image scanning module of five speculum contains at least one light source, five speculums, gets for instance lens group, image sensor and frame. The light source irradiates a file to be scanned to generate an image light beam Li incident on the image scanning module; the five reflectors are used for reflecting the image light beam Li to form an image light beam Lo incident on the image capturing lens group; the image capturing lens assembly is used for focusing the incident image light beam Lo on the image sensor; the frame is used for accommodating the light source, the five reflectors, the image capturing lens group and the image sensor; the image light beam Li, the five reflectors and the image light beam Lo form a light path, and on the light path, at least two reflectors of the five reflectors perform multiple reflection more than two times; and optical conditions are satisfied:

wherein p is the total number of reflections along the optical path, α_iIs the angle between the normal (normal line) of the reflection surface of the ith reflector of the optical path and the + Z axis.

Therefore, the utility model provides an image scanning module of five speculum, it can have one or more following advantage:

(1) the image light beam is reflected by the five reflectors, and at least two reflectors are in multiple reflection, so that the optical path length can be increased, and stray light generated by multiple reflection of the reflectors can be reduced or eliminated by arranging the reflectors in positions and angles, so that the ghost phenomenon is reduced.

(2) The optical paths of the five reflectors can be used for scanners with different total optical path lengths, A4/A3 and other different sizes or image capture lens groups with different effective focal lengths by only adjusting the positions of the reflectors. The image beam Lo can be emitted into the image capturing lens assembly along the optical axis of the image capturing lens assembly by only adjusting the relative position of the reflector, thereby increasing the wide applicability.

(3) When the effective focal length and the total optical path length of the image capturing lens assembly are matched, the position of the reflector can be adjusted, so that the size of the frame is minimized, and the requirement of miniaturization is met.

Drawings

FIG. 1 is a diagram illustrating a first exemplary image scanning module of the prior art;

FIG. 2 is a diagram illustrating a second exemplary image scanning module of the prior art;

FIG. 3 is a diagram illustrating a third exemplary image scanning module of the prior art;

fig. 4 is a schematic diagram of a first embodiment of an image scanning module with five mirrors according to the present invention;

FIG. 5 is a schematic view of the mirror angles of an image scanning module according to the present invention with five mirrors;

FIG. 6 is a schematic diagram of an image scanning module with five mirrors according to the present invention for eliminating stray light on the M2 → M3 optical path;

FIG. 7 is a diagram of a second embodiment of an image scanning module with five mirrors according to the present invention;

FIG. 8 is a schematic diagram of a fifth embodiment of an image scanning module according to the present invention; and

fig. 9 is a diagram illustrating an image scanning module according to a fourth embodiment of the present invention.

Description of the main symbols: 1 is an image scanning module (scanning module); 2 is a file (document); 12 is a light-transmitting plate (cover glass); 13 is a frame; 132 is an aperture (aperture); 14 is an image sensor (image sensor); 15 is an image pickup lens group (pickup lens); 16 is a light source (light source); 161 is a first light source (first light source); 162 is a second light source (second light source); 16a is light (light); 16b is light (light); 171 is a mirror M1(M1 reflection mirror); 172 is a mirror M2(M2 reflection mirror); 173 is a mirror M3(M3 reflection mirror); 174 is a mirror M4(M4 reflection mirror); 175 is a mirror M5(M5 reflection mirror); 21 is an image beam (image beam); 31 is the normal of the reflecting surface of the mirror M1; 32 is the normal of the reflecting surface of the mirror M2; 91 is an image scanning module; and 917 a mirror.

Detailed Description

To make the present invention clearer and more detailed, preferred embodiments are shown in conjunction with the following drawings, and the structure and technical features of the present invention are described in detail as follows.

Referring to fig. 4, the image scanning module 1 according to the present invention includes a light source 16, five mirrors (M1, M2, M3, M4, M5)171 to 175, an image capturing lens assembly 15, an image sensor 14 and a frame 13. The light source 16 is one of a cold cathode lamp, an led lamp and a xenon lamp. When the light source 16 emits light, the light passes through the transparent plate 12 and irradiates the document 2 to be scanned. The document 2 to be scanned reflects the light to form a reflected light, and when the reflected light passes through the transparent plate 12, an image beam L incident on the image scanning module 1 is formed_iAn image beam L_iThe first reflection is formed by the incident light on the first reflector (M1)171, the second reflection is formed by the incident light on the second reflector (M2)172, the third reflection is formed by the incident light on the third reflector (M3)173, the third reflection is formed by the incident light on the fourth reflector (M4)174, the fourth reflection is formed by the incident light on the third reflector (M3)173, the fifth reflection is formed by the incident light on the second reflector (M2)172, the sixth reflection is formed by the incident light on the fifth reflector (M5)175, the seventh reflection is formed, and finally the image light beam L incident on the image capturing lens group 15 is formed_oAn optical path thereof is Li (Obj, file to be scanned) → M1 → M2 → M3 → M4 → M3 → M2 → M5 → Lo (Img, image sensor); wherein the second mirror (M2)172 and the third mirrorThe mirror (M3)173 is a multiple reflection, and each reflects twice.

Accordingly, the present invention provides an image scanning module with five reflectors for multiple reflection, as shown in fig. 4, comprising at least one light source, five reflectors, an image capturing lens assembly, an image sensor and a frame; on the X-Z plane, half of the total distance between the reflectors and the total optical path length (TTL) satisfy the following conditions:

wherein, TTL is total optical path length TTL ═ D_i+D₁+D₂+D₃+D₄+D₅+D₆+D_O、D_reflIs the sum of the distances between the mirrors along the optical path, as shown in FIG. 4, i.e. D_refl＝D₁+D₂+D₃+D₄+D₅+D₆(ii) a The angle relation among all the reflectors satisfies that:

wherein alpha is_iThe included angle (deg.) between the normal (normal line) of the reflection surface of the ith reflector and the + Z axis of the optical path is shown in figure 5, p is the sum of the reflection times along the optical path, and is shown as 7 in figure 4,

the positional relationship between the mirrors is the coordinate (M) of the reflection point of the previous mirror_iX，M_iZ) The angle of the reflector and the angle of the incident light on the reflector are determined as follows:

M_(i+1)X＝M_iX-D_isin(180±(2α_i+β_i))

；(4)

M_(i+1)Z＝M_iZ-D_iCos(180±(2α_i+β_i))

wherein (M)_iX，M_iZ) Is the ith(X, Z) coordinate, beta, of a reflection point of a mirror_iThe angle (deg.) between the image beam incident on the ith mirror and the + Z axis is shown in FIG. 5.

Under the unchangeable condition of total optical path length, for effectively reducing the frame volume, the utility model discloses a speculum adopts multiple reflection, and wherein speculum (M2)172 reflects image light beam secondary, speculum (M3)173 reflects image light beam secondary, if in prior art, same speculum can produce serious stray light and form ghost phenomenon after the multiple reflection, must reduce stray light through setting up or adjusting suitable speculum width, angle in order to try to manage. However, the image scanning module of five reflectors provided by the present invention adopts a relatively long distance between the light path M2 → M3 and M3 → M2 of the multiple-reflection reflector surface, and adopts a relatively short distance between the reflection points of the multiple-reflection reflector surface, so as to effectively reduce the stray light.

In fig. 6, after the light source 16 emits light, the light passes through the transparent plate 12 and irradiates the document 2 to be scanned, and the reflected light generated by the light irradiating the document 2 to be scanned passes through the transparent plate 12 to form an image beam L incident on the image scanning module 1_i. In addition, the image beam L transmitted through the on-frame stop 132_i' which is a stray light, reflected for the first time by the first mirror (M1)171, and the image light beam L_iThe reflected light rays are reflected by the second reflector (M2)172 and the third reflector (M3)173 at different angles, and then the reflected light rays are eliminated by exceeding the reflection range of the fourth reflector (M4)174 due to the reflection angles. When the stray light L_iThe stray light factor FOL (stray light beam) is eliminated by the angle of the incident light on each mirror surface and the angle of the mirror surface, which are related to the diameter d of the stop, the angle of the mirror surface and the width of the mirror surface. On the M3 reflector 173, a stray light elimination factor fol (factor of overlapped light beam) can be obtained if the formula (5) is satisfied:

wherein λ is₃At the minimum width of the M3 mirror 173, it can be expressed in reflection point coordinates, i.e., in the X-Z plane, (M)_3X，M_3Z)、(M_5X，M_5Z) The coordinates of the reflection point of the secondary reflection for the image beam to generate reflection on M3; FOL is to eliminate the stray light factor (factor of overlapped light beam), d is the diameter of the diaphragm.

The image scanning module with five reflectors provided by the utility model changes the direction and the path of the image of the document to be scanned by reflecting the image by the five reflectors, and can increase the optical path; by enabling the distance between the reflectors and the total optical path length (TTL) to satisfy the formula (1) and enabling the total sum of the included angles between the normal of the reflecting surface of each reflector and the + Z axis to satisfy the formula (2), when the total optical path length is changed, only the distance between the reflectors needs to be adjusted; the M3 mirror 173 satisfies formula (5) by arranging the angles and distances of the five mirrors to prevent stray light from entering the image capturing lens assembly, thereby reducing ghost image.

< first embodiment > A4 size image scanning module

Fig. 4 shows an embodiment of an image scanning module 1 using five mirrors according to the present invention, which includes a ccfl light source 16, five mirrors M1(171), M2(172), M3(173), M4(174), and M5(175), an image capturing lens assembly 15, an image sensor 14, and a frame 13; is used in an a4 size image scanning module.

When the light source 16 emits light, the light passes through the watch glass 12 to irradiate the document 2(Obj) to be scanned, and then the image light beam L incident on the image scanning module 1 is generated_i(ii) a Image light beam L_iReflected by the mirror M1, irradiated on the mirror M2, reflected by the mirror M2, irradiated on the mirror M3, reflected by the mirror M3, irradiated on the mirror M4, reflected by the mirror M4, irradiated on the mirror M3, reflected by the mirror M3, irradiated on the mirror M2, reflected by the mirror M2, irradiated on the mirror M5, and reflected by the mirror M5, thereby obtaining an image beam L_oFocused by the image capturing lens assembly 15 to form an image (Img) on the image sensor 14; the frame 13 is used for accommodating various components in the image scanning module 1. Its optical path length is li (obj) → M1 → M2 → M3 → M4 → M3 → M2 → M5 → lo (img). Included angle alpha between normal line of Mi reflecting surface of each reflector and + Z axis_iThe coordinates (M) of this point of the secondary reflection of the mirror Mi on the X-Z plane_iX，M_iZ) As shown in table one:

optical parameter table of the first embodiment

In this embodiment, the total number of times p of total reflection is 7, the total distance between the mirrors and the total optical path length satisfy formula (1), the total angle of the mirrors along the optical path satisfies formula (2), multiple reflections occur at M2 and M3, the diameter of the stop 132 on the frame 13 is 5mm, and the M3 mirror 173 satisfies formula (5), so that stray light can be effectively eliminated and ghost phenomenon can be prevented:

TTL＝D_i+D₁+D₂+D₃+D₄+D₅+D₆+D_O＝355.22mm

\frac{D_{refl}}{2 (TTL - D_{refl})} = 0.7901

FOL＝0.0307

< second embodiment > a3 size image scanning module

Fig. 7 shows an embodiment of an image scanning module 1 using five mirrors according to the present invention, which includes two ccfl

light sources

16a, 16b, five mirrors M1(171), M2(172), M3(173), M4(174), and M5(175), an image capturing lens assembly 15, an image sensor 14, and a frame 13. In this embodiment, the total optical length (TTL) of the image scanning module with A3 size is greater than that of the image scanning module with a4 size, and the total optical length of the image scanning module with a4 size can be adjusted to the image scanning module with A3 size by adjusting the distance between the mirrors without changing the angle between the mirrors.

The optical path of this embodiment is the same as that of the first embodiment, and is li (obj) → M1 → M2 → M3 → M4 → M3 → M2 → M5 → lo (img), and the angle α between the normal of the reflection surface of each mirror Mi and the + Z axis is α_iThe coordinates (M) of this point of the secondary reflection of the mirror Mi on the X-Z plane_iX，M_iZ) As shown in table two:

TABLE II optical parameter table of the second embodiment

In this embodiment, the total number of times p of total reflection is 7, the total sum of the distances between the reflectors and the total optical path length (TTL) satisfy formula (1), the total sum of the angles of the reflectors along the optical path satisfies formula (2), multiple reflections occur at M2 and M3, the diameter of the stop 132 on the chassis 13 is 5mm, and the M3 reflector 173 satisfies formula (5), so that stray light can be effectively eliminated and ghost phenomenon can be prevented:

TTL＝D_i+D₁+D₂+D₃+D₄+D₅+D₆+D_O＝492.98mm

\frac{D_{refl}}{2 (TTL - D_{refl})} = 0.9101

FOL＝0.0783

compared with the first embodiment, the embodiment only adjusts the distance between the reflectors without adjusting the angles of the reflectors, and can adjust the TTL of the first embodiment from 355.22mm to 492.98mm, thereby increasing the wide applicability.

< third embodiment > a4 size image scanning module

Fig. 8 shows an embodiment of an image scanning module 1 using five mirrors according to the present invention, which includes a ccfl light source 16, five mirrors M1(171), M2(172), M3(173), M4(174), and M5(175), an image capturing lens assembly 15, an image sensor 14, and a frame 13; is used in an a4 size image scanning module.

When the light source 16 emits light, the light passes through the watch glass 12 to irradiate the document 2(Obj) to be scanned, and then the image light beam L incident on the image scanning module 1 is generated_i(ii) a The optical path is the same as that of the first and second embodiments, and is li (obj) → M1 → M2 → M3 → M4 → M3 → M2 → M5 → lo (img). Included angle alpha between normal line of Mi reflecting surface of each reflector and + Z axis_iThe coordinates (M) of this point of the secondary reflection of the mirror Mi on the X-Z plane_iX，M_iZ) As shown in table three:

third embodiment of the optical parameter table

TTL＝D_i+D₁+D₂+D₃+D₄+D₅+D₆+D_O＝355.22mm

\frac{D_{refl}}{2 (TTL - D_{refl})} = 0.9281

FOL＝0.2275

< fourth embodiment > a3 size image scanning module

Fig. 8 shows an embodiment of an image scanning module 1 using five mirrors according to the present invention, which includes a ccfl light source 16, five mirrors M1(171), M2(172), M3(173), M4(174), and M5(175), an image capturing lens assembly 15, an image sensor 14, and a frame 13; in this embodiment, the image scanning module of the third embodiment is used in an image scanning module of A3 size, where TTL is 492.98mm, and the total optical path length of the image scanning module of a4 size can be adjusted to the image scanning module of A3 size by adjusting the distance between the mirrors without changing the angle between the mirrors.

The optical path of this embodiment is the same as that of the third embodiment, and is li (obj) → M1 → M2 → M3 → M4 → M3 → M2 → M5 → lo (img), and the angle α between the normal of the reflection surface of each mirror Mi and the + Z axis is α_iThe coordinates (M) of this point of the secondary reflection of the mirror Mi on the X-Z plane_iX，M_iZ) As shown in table four:

TABLE IV, OPTICAL PARAMETER TABLE OF THE FOUR EXAMPLE

TTL＝D_i+D₁+D₂+D₃+D₄+D₅+D₆+D_O＝492.98mm

\frac{D_{refl}}{2 (TTL - D_{refl})} = 0.5751

FOL＝0.0475

compared with the third embodiment, the embodiment only adjusts the distance between the mirrors without adjusting the angles of the mirrors, and can adjust the TTL of the first embodiment from 355.22mm to 492.98mm, thereby increasing the wide applicability.

< fifth embodiment > small-sized image scanning module of a3 size

Fig. 9 shows an embodiment of an image scanning module 1 using five mirrors according to the present invention, which is the same as the fourth embodiment, and includes a ccfl light source 16, five mirrors M1(171), M2(172), M3(173), M4(174), and M5(175), an image capturing lens assembly 15, an image sensor 14, and a frame 13; in the present embodiment, TTL is 492.98mm, and the image scanning module of the fourth embodiment is used to adjust the distance between the mirrors, so that the volume of the image scanning module of the a3 size can be reduced without changing the angle between the mirrors.

The optical path of this embodiment is the same as that of the third embodiment, and is li (obj) → M1 → M2 → M3 → M4 → M3 → M2 → M5 → lo (img), and the angle α between the normal of the reflection surface of each mirror Mi and the + Z axis is α_iCoordinates (M) of the reflection point of the mirror Mi on the X-Z plane_iX，M_iZ) As shown in table five:

table five, optical parameter table of fifth embodiment

TTL＝D_i+D₁+D₂+D₃+D₄+D₅+D₆+D_O＝492.98mm

\frac{D_{refl}}{2 (TTL - D_{refl})} = 0.9933

FOL＝0.3711

compared with the fourth embodiment, the present embodiment has a larger thickness of the frame, but a significantly smaller length, i.e. the image scanning device can be reduced in size by only adjusting the distance between the mirrors, thereby achieving the requirement of miniaturization.

In summary, the image scanning module according to the present invention has the advantages of utilizing the optical path formed by the multiple reflection of the five reflectors and at least two reflectors, increasing the depth of field by increasing the length of the optical path, and greatly reducing or eliminating the stray light generated by the multiple reflection of the reflectors, thereby reducing the ghost phenomenon.

According to the utility model discloses an another efficiency of the image scanning module of five speculum lies in making when assembling, only needs the distance of adjustment speculum and needn't angle regulation, can be applied to A4/A3 size, different and get for instance the effective focal length of lens group, provides extensive application.

The foregoing is by way of example only, and not limiting. It is intended that all equivalent modifications or variations not departing from the spirit and scope of the present invention shall be included in the scope of the appended claims.

Claims

1. An image scanning module with five reflectors is characterized by comprising at least one light source, five reflectors, an image taking lens group, an image sensor and a frame; wherein,

the light source irradiates a file to be scanned to generate an image light beam Li incident on the image scanning module; the five reflectors are used for reflecting the image light beam Li to form an image light beam Lo incident on the image capturing lens group; the image capturing lens assembly is used for focusing the incident image light beam Lo on the image sensor; the frame is used for accommodating the light source, the five reflectors, the image capturing lens group and the image sensor; the image light beam Li, the five reflectors and the image light beam Lo form a light path, and on the light path, at least two reflectors in the five reflectors are multiple reflections with more than two reflections; and optical conditions are satisfied:

wherein p is the total number of reflections along the optical path, α_iIs the included angle between the normal of the reflection surface of the ith reflector of the light path and the + Z axis.

2. The five-mirror image scanning module of claim 1, wherein the total optical path length of the optical path and the distance between the five mirrors satisfy the following condition:

wherein TTL is total optical path length and D_reflIs the sum of the distances between the five reflectors along the optical path.

3. The five-mirror image scanning module of claim 1, wherein the five mirrors are mirror M1, mirror M2, mirror M3, mirror M4 and mirror M5, respectively, and the optical paths are image beam Li → mirror M1 → mirror M2 → mirror M3 → mirror M4 → mirror M3 → mirror M2 → mirror M5 → image beam Lo, and multiple reflections of each secondary reflection are performed at the mirror M2 and the mirror M3.

4. The image scanning module as claimed in claim 1, wherein the light source is one of a cold cathode fluorescent lamp, a light emitting diode lamp and a xenon lamp.