TWI651549B - Fresnel lens - Google Patents

Abstract

A Fresnel lens comprising a Fresnel face. The Fresnel face includes a plurality of Fresnel effective faces through which the imaging light passes, and two adjacent Fresnel effective faces are interconnected by a Fresnel ineffective face. One of the Fresnel ineffective faces on one of the sections including an optical axis of the Fresnel lens is located at one end of the tooth peak of the Fresnel lens and a connection at one end of the valley of the Fresnel lens The straight line and a reference line clip a draft angle. The optical axis coincides with the cross section. The reference line is parallel to the optical axis and passes through the Fresnel effective surface at one end of the tooth peak. The angle of each draft angle is less than 90 degrees. These draft angles include first, second, third, fourth, and fifth draft angles that are gradually increasing from the radially outward angle of the optical axis.

Description

Fresnel lens

This invention relates to a lens and, more particularly, to a Fresnel lens.

In the prior art, the optical imaging quality of a typical Fresnel lens is often caused by reflection or refraction of light incident on the Fresnel ineffective surface to form stray light, which causes a spot or a spot on the image to affect the image quality. In practice, when a Fresnel lens is produced by injection molding, a draft angle must be designed to separate the Fresnel lens from the mold. However, in the prior art, the draft angles of the Fresnel lenses are the same, and the rays that are incident on the Fresnel ineffective surface are reflected at the same angle to form stray light. Such a design causes stray light to concentrate and has high illuminance, so that a clear spot is formed on the image plane, and image quality and sharpness are affected and decreased. Therefore, how to reduce the stray illumination and improve the overall sharpness of the imaging to improve the optical imaging quality of the Fresnel lens is a subject of research in the field.

The present invention provides a Fresnel lens that has good optical imaging quality.

A Fresnel lens according to an embodiment of the present invention includes a Fresnel surface. The Fresnel face includes a plurality of Fresnel effective faces that allow imaging light to pass through. Two adjacent Fresnel effective faces are interconnected by a Fresnel ineffective face. One of a cross section of an Fresnel ineffective plane on one of the optical axes including the Fresnel lens is located at one end of the tooth peak of the Fresnel lens and a connecting line at one end of the valley of the Fresnel lens The reference line clips a draft angle. The reference line is parallel to the optical axis and passes through the Fresnel effective surface at one end of the tooth peak. The optical axis coincides with the cross section. The angle of each draft angle is less than 90 degrees. The draft angle includes a first draft angle calculated from the optical axis radially outward as a first one, and a second draft angle calculated from the optical axis radially outward as a second, a self-light The axis is calculated radially outward as the third third draft angle, one from the optical axis radially outward as the fourth fourth draft angle and one from the optical axis radially outward. The fifth fifth draft angle. The second draft angle is greater than the first draft angle. The third draft angle is greater than the second draft angle. The fourth draft angle is greater than the third draft angle. The fifth draft angle is greater than the fourth draft angle.

Based on the above, in the Fresnel lens of the embodiment of the present invention, by providing a draft angle which is gradually increased from the optical axis in the Fresnel lens, the irradiation area of the stray light can be effectively dispersed and the stray light can be reduced. The illuminance, in turn, achieves good optical imaging quality.

The above described features and advantages of the invention will be apparent from the following description.

The Fresnel lens of the following embodiments of the present invention can be applied to a display device of a head-mounted analog stereo vision such as virtual reality (VR), or a portable electronic device such as a mobile phone, a camera, a tablet, or It is an optical imaging lens such as a Personal Digital Assistant (PDA) or an optical lens for illumination.

In order to explain the configuration relationship of the Fresnel lens of the following embodiments in detail, the Fresnel lens of the following embodiment can be regarded as being in a three-dimensional space constructed by the X-axis, the Y-axis, and the Z-axis, and the three-axis X-axis and Y-axis And the Z axis is perpendicular to each other.

1 to 4 are schematic cross-sectional views of a Fresnel lens according to various embodiments of the present invention.

Referring first to FIG. 1, in the present embodiment, the Fresnel lens 100 has a Fresnel surface 110 and a surface 120 opposite the Fresnel surface 110. In an embodiment of the invention, the surface 120 may be a planar, concave, convex or Fresnel surface, and in the present embodiment, the surface 120 is exemplified by a plane. The cross section shown in Fig. 1 includes an optical axis I of the Fresnel lens 100, that is, the optical axis I coincides with the cross section (XY plane) of Fig. 1.

Fresnel face 110 includes a plurality of Fresnel effective faces 112 through which imaging light passes. The Fresnel ineffective faces 114 are interconnected between two adjacent Fresnel effective faces 112. These Fresnel effective faces 112 are staggered between these Fresnel ineffective faces 114. In an embodiment of the invention, the Fresnel effective surface 112 is a curved surface having a generally optical lens having its corresponding optical function. For example, if the optical lens is a converging lens (for example, a convex lens), its corresponding optically functional curved surface has a convergence function. If the optical lens is a diverging lens (for example, a concave lens), the corresponding optically functional curved surface has divergence. Features. Thus, as the light passes through the Fresnel effective surface 112, it is refracted by the Fresnel effective surface 112 and the light is concentrated or diverged. On the other hand, when the light passes through the Fresnel ineffective surface 114, it is refracted by the Fresnel ineffective surface 114, and the light exits the Fresnel lens 100 to form stray light in a non-original optical design consideration. In the present embodiment, the shape of the Fresnel effective surface 112 is exemplified by a convex surface having a converging function. In other embodiments, the shape of the Fresnel effective surface 112 may also be a concave surface having a diverging function, and the invention is not limited thereto. On the other hand, in the present embodiment, the Fresnel ineffective surface 114 is a conical surface.

From another point of view, these Fresnel effective faces 112 and the Fresnel ineffective faces 114 form a plurality of teeth S radially outward from the optical axis I, and these teeth S comprise a central tooth SC and a plurality of peripherals The tooth SP (represented by the central tooth SC and the five peripheral teeth SP in FIG. 1), the central tooth SC and the peripheral teeth SP are radially outward from the optical axis I as the central tooth SC and the first peripheral tooth SP1, respectively. The second peripheral tooth SP2, the third peripheral tooth SP3, the fourth peripheral tooth SP4, and the fifth peripheral tooth SP5. The Radial Direction is, for example, the direction of the positive X-axis, the direction of the negative X-axis, the direction of the positive Z-axis, the direction of the negative Z-axis, or other direction perpendicular to the Y-axis, wherein the optical axis I is parallel to the Y-axis. In the present embodiment, the central tooth SC includes a central Fresnel effective surface 112c and the optical axis I passes through the center of the central Fresnel effective surface 112c. Each of the peripheral teeth SP includes a Fresnel effective surface 112 and a Fresnel ineffective surface 114. Each of the peripheral teeth SP has a tooth peak of the Fresnel lens 100 and a valley of the Fresnel lens 100. The tooth peak is a position where the peripheral tooth SP corresponds to the maximum thickness of the surface 120, and the valley is a position where the peripheral tooth SP corresponds to the minimum thickness of the surface 120. One of the Fresnel ineffective faces 114 on one of the sections including the optical axis I of the Fresnel lens 100 (i.e., the cross section (XY plane) of FIG. 1) is located at one end of the 100 tooth peak of the Fresnel lens. A connecting line L at one end of the valley of the Fresnel lens 100 and a reference line RL sandwich the draft angle θ. The reference line RL is parallel to the optical axis I and passes through one end of the Fresnel effective surface 114 at the tooth peak. The angle of each draft angle θ is less than 90 degrees. The draft angle θ includes a first first draft angle θ1 from the optical axis I radially outward, and a second second draft angle θ2 from the optical axis I radially outward. A third third draft angle θ3 from the optical axis I radially outward, a fourth fourth draft angle θ4 from the optical axis I radially outward and a radial direction from the optical axis I The fifth fifth draft angle θ5 is calculated from the outside.

In the present embodiment, in the first peripheral tooth SP1, the first connecting straight line L1 (the first Fresnel invalid surface 1141) and the first reference line RL1 sandwich the first draft angle θ1, and the first Fresnel There is only one first Fresnel effective surface 1121 between the ineffective surface 1141 and the second Fresnel inactive surface 1142. In the second peripheral tooth SP2, the second connecting straight line L2 (the second Fresnel invalid surface 1142) and the second reference line RL2 sandwich the second draft angle θ2, and the second Fresnel invalid surface 1142 and the third There is only one second Fresnel effective surface 1122 between the Fresnel ineffective faces 1143. In the third peripheral tooth SP3, the third connecting straight line L3 (the third Fresnel invalid surface 1143) and the third reference line RL3 sandwich the third draft angle θ3, and the third Fresnel invalid surface 1143 and the fourth There is only one third Fresnel effective surface 1121 between Fresnel ineffective faces 1144. In the fourth peripheral tooth SP4, the fourth connecting straight line L4 (the fourth Fresnel invalid surface 1144) and the fourth reference line RL4 sandwich the fourth draft angle θ4, and the fourth Fresnel invalid surface 1144 and the fifth There is only one fourth Fresnel effective surface 1124 between the Fresnel ineffective faces 1145. In the fifth peripheral tooth SP5, the fifth connecting straight line L5 (the fifth Fresnel ineffective surface 1145) and the fifth reference line RL5 sandwich the fifth draft angle θ5. The magnitude relationship of these draft angles θ is such that the second draft angle θ2 is greater than the first draft angle θ1. The third draft angle θ3 is greater than the second draft angle θ2. The fourth draft angle θ4 is greater than the third draft angle θ3. The fourth draft angle θ4 is greater than the third draft angle θ3. The fifth draft angle θ5 is greater than the fourth draft angle θ4. In other words, the angular relationship of these draft angles θ is gradually increasing radially outward from the optical axis I.

Table 1 below shows the maximum illuminance measured at different viewing angles of a Fresnel lens of a comparative embodiment and a Fresnel lens of the embodiment of Fig. 1. Table 2 below is the stray light area measured by the Fresnel lens of the comparative embodiment and the Fresnel lens of the embodiment of Fig. 1 at different viewing angles. Among them, in the Fresnel lens of the comparative example, the size of each draft angle is the same as each other.  <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td> field of view (degrees) </td><td> 10 </td><td> 15 </td></tr><tr><td> The maximum illuminance of the stray light of the Fresnel lens of the comparative example (lux, Lux) </td><td> 0.00196 </td><td> 0.00319 < /td></tr><tr><td> The maximum illuminance of the stray light of the Fresnel lens of the embodiment of Fig. 1 (lux, Lux) </td><td> 0.00115 </td><td> 0.00146 </ Td></tr></TBODY></TABLE> Table 1  <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td> field of view (degrees) </td><td> 10 </td><td> 15 </td></tr><tr><td> The stray light area of the Fresnel lens of the comparative example (mm²) </td><td> 44 </td> <td> 36.44 </td></tr><tr><td> The stray light area of the Fresnel lens of the embodiment of Fig. 1 (mm²) </td><td> 88 </td><td> 56.4 </td></tr></TBODY></TABLE> Table 2 As can be seen from Table 1 above, the Fresnel lens 100 of the present embodiment is at different viewing angles. The maximum illuminance of the generated stray light is smaller than the maximum illuminance of the stray light generated by the Fresnel lens of the comparative example. As can be seen from Table 2 above, the area of stray light generated by the Fresnel lens 100 of the present embodiment is larger than the area of stray light generated by the Fresnel lens of the comparative example at different viewing angles. From this point of view, the Fresnel lens 100 of the present embodiment can effectively reduce the maximum illuminance of stray light and the same total stray light energy at different viewing angles compared to the Fresnel lens of the comparative embodiment. The area of the stray light distribution is dispersed to reduce the effect of stray light on the image quality. Therefore, the Fresnel lens 100 of the present embodiment has good optical imaging quality.  

Further, in the present embodiment, since each Fresnel ineffective surface 114 is a conical surface, and the intersecting line of each Fresnel ineffective surface 114 intersecting the section including the optical axis I is a straight line, the Fresnel of the present embodiment The lens 100 is easier to machine and facilitates measurement and correction calculations after injection molding. Moreover, it should be noted that in FIG. 1, with the five peripheral teeth S and the corresponding five draft angles θ as representative, other peripheral teeth may be added in the radial direction outward in the fifth peripheral teeth S5. The number of teeth added from the fifth peripheral tooth S5 in the radial direction may be arbitrarily or appropriately changed, and the present invention is not limited thereto.

Referring to FIG. 2, the cross section shown in FIG. 2 includes an optical axis I of the Fresnel lens 100a. The Fresnel lens 100a of the embodiment of Fig. 2 is substantially similar to the Fresnel lens 100 of the embodiment of Fig. 1, with the difference between the Fresnel faces 110a in the Fresnel face 110a, respectively. It is a surface having a curvature in the direction of the section including the optical axis I, that is, a surface having a curvature on the section shown in FIG. Through the above design, the Fresnel lens 100a of the present embodiment can more effectively guide the stray light caused by the single peripheral tooth SP to different directions, and can prevent the excessive concentration of stray light and the appearance of obvious spots or spots to reduce The effect of stray light on optical imaging quality.

Referring to FIG. 3, the cross section shown in FIG. 3 includes an optical axis I of the Fresnel lens 100b. The Fresnel lens 100b of the embodiment of Fig. 3 is substantially similar to the Fresnel lens 100 of the embodiment of Fig. 1, with the difference between: in the Fresnel lens 100b, each tooth S is perpendicular to the light The pitch P (Pitch) in the direction of the axis I (i.e., the direction of the positive X-axis, the direction of the negative X-axis, the direction of the positive Z-axis, the direction of the negative Z-axis, or any direction parallel to the XZ plane) is identical to each other. SC hereinafter for the center tooth pitch Pc, and the periphery of the teeth of the tooth pitch P _p SP separate definitions. For the center tooth SC, the pitch Pc of the center tooth SC in the direction perpendicular to the optical axis I is defined as the distance from the optical axis I to the center tooth SC and the first peripheral tooth SP1 (ie, closest to the center tooth SC). The distance of the valley between the teeth SP1). For the peripheral teeth SP, the pitch P _p of each of the peripheral teeth SP in the direction perpendicular to the optical axis I is defined as the valley of each peripheral tooth SP on the side close to the optical axis I and the distance from the optical axis I The distance between the valleys on one side. SC is the central tooth pitch Pc equal to each peripheral tooth pitch P _p of the SP, the SP and the periphery of the teeth pitch P _p identical to each other. If a Fresnel lens having a Fresnel effective surface 112 having a large radius of curvature is manufactured, and the pitch P of a tooth S is designed correspondingly with a certain tooth depth, the pitch P of one tooth S is larger. However, such a Fresnel lens is difficult to maintain a certain number of teeth, and it is difficult to make the Fresnel lens thin. Therefore, by designing the same pitch P of each tooth S, it is possible to manufacture the Fresnel lens 100b having the Fresnel effective surface 112 having a large radius of curvature with a relatively small thickness while maintaining a certain number of teeth. . At the same time, the Fresnel surface 100b can be easily processed by the above design. The pitch P of the preferred effect is in the range of 0.05 mm ≦ P ≦ 0.60 mm.

Referring to FIG. 4, the cross section shown in FIG. 4 includes an optical axis I of the Fresnel lens 100c. The Fresnel lens 100c of the embodiment of Fig. 4 is substantially similar to the Fresnel lens 100 of the embodiment of Fig. 1, with the difference between the two: in the Fresnel lens 100c, the teeth S are parallel to the light. The direction of the axis I (i.e., the direction of the positive Y-axis, the direction of the negative Y-axis, the direction of the positive Z-axis, the direction of the negative Z-axis, or any direction parallel to the YZ plane) is the same as each other. SC hereinafter for the central tooth and the surrounding teeth depth of the teeth SP SGc tooth depth separate definitions SG _p. For the center tooth SC, the tooth depth SGc of the center tooth SC is defined as the valley of the center tooth SC at the apex of the optical axis I to the edge of the center tooth SC (ie, between the center tooth SC and the first peripheral tooth SP1) The distance of the valleys in the direction parallel to the optical axis I. For the peripheral tooth SP, the tooth depth SG _{p of} the peripheral tooth SP is defined as the Fresnel invalid surface 114 of the peripheral tooth SP located at one end of the tooth peak of the peripheral tooth SP on the section including the optical axis I The end of the valley of the peripheral tooth SP is in a direction parallel to the optical axis I. SC central tooth gear SG _c is equal to the depth of each peripheral tooth depth of the teeth SP SG _p, peripheral teeth and these teeth SP SG _p depths identical to each other. Since the Fresnel effective surface 112 close to the optical axis I is relatively gentle, and the Fresnel effective surface 112 away from the optical axis I is inclined, if the pitch of each tooth S is designed with the same tooth depth SG, it can be manufactured. The Fresnel lens 100c having the first peripheral tooth SP1 farther from the optical axis I can thereby prevent the generation of stray light near the imaging center. At the same time, the Fresnel surface 100c can be easily processed by the above design. A range having a better effect is 0.001 mm ≦ SG ≦ 0.400 mm.

It should be noted that, in order to clearly show the drawings, the fourth peripheral teeth S4, the fifth peripheral teeth S5, and the corresponding fourth draft angle θ4 and the fifth draft angle θ5 are omitted in FIGS. 2 to 4, and Corresponding related descriptions can be supported by those skilled in the art with reference to Figure 1 and related paragraphs.

In summary, the Fresnel lens of the above embodiment of the present invention can achieve the following effects and advantages:

1. The Fresnel lens of the above various embodiments of the present invention maximizes the imaging ray incident on the Fresnel effective surface 112 by providing a draft angle θ which is gradually increased from the optical axis I at a radially outward angle. The imaging light to the Fresnel invalid surface 114 is minimized to reduce the maximum illuminance of the stray light, and the area of the stray light distribution is dispersed under the same total stray light energy, so that the overall illumination of the image is relatively uniform, and the local illuminance is uneven. The phenomenon, in order to achieve the advantages of improved imaging clarity. Moreover, since the central field of view of the human eye is much more sensitive than the peripheral field of view, the sharpness of the center of the image provides a more pronounced perception of the human eye, so the first draft angle θ1 to the fifth draft angle θ5 are set from the radial direction of the optical axis I. The outward angle is increasing, which can effectively improve the central definition of the image.

2. If each draft angle θ is greater than or equal to 1 ∘ and less than or equal to 25 ∘, the draft angle θ can be prevented from being too small, and the lens structure is difficult to be demolded during the forming process, and the excessive optical effective portion is also avoided.

3. The Fresnel lens in the above various embodiments of the present invention may further include a sixth draft angle which is calculated from the optical axis I radially outward as a sixth, and a radial direction from the optical axis I. Calculated as the seventh seventh draft angle, one from the optical axis I radially outward as the eighth eighth draft angle, one from the optical axis I radially outwards as the ninth The ninth draft angle and one from the optical axis I are radially outwardly calculated as the tenth tenth draft angle, and the sixth draft angle is greater than the fifth draft angle, and the seventh draft angle is greater than the sixth The draft angle, the eighth draft angle is greater than the seventh draft angle, the ninth draft angle is greater than the eighth draft angle, and the tenth draft angle is greater than the ninth draft angle, which can more effectively reduce the maximum illumination of stray light , to reduce the phenomenon of uneven local illumination, and thus achieve improved imaging clarity.

4. On the side of the Fresnel lenses 100, 100a, 100b, 100c of the above-described plurality of embodiments adjacent to the Fresnel faces 100, 100a, 100b, 100c, if these Fresnel ineffective faces 114 are in the optical axis The sum of the lengths of the plurality of orthographic projections of the plurality of sections on the section perpendicular to the reference plane RP of the optical axis I divided by the plurality of sections of the Fresnel effective plane 112 on the section containing the optical axis I The ratio of the sum of the lengths of the plurality of orthographic projections on the reference plane RP perpendicular to the optical axis I satisfies the condition of 0.230 or less, thereby avoiding the loss of excessive optical effective portions, achieving good optical imaging quality, and having better effects. The numerical range is that the above ratio satisfies 0.230 or less and 0.045 or more. The reference plane RP is an XZ plane composed of an X axis and a Z axis.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100, 100a, 100b, 100c‧ ‧ Fresnel lens

110, 110a, 110b, 110c‧‧ Fresnel

112‧‧‧ Fresnel effective noodles

120‧‧‧ surface

112c‧‧‧Central Fresnel Effective Side

1121‧‧‧First Fresnel Effective Face

1122‧‧‧Second Fresnel Effective Surface

1123‧‧‧ third Fresnel effective surface

1124‧‧‧Four Fresnel Effective Surface

1125‧‧‧ fifth Fresnel effective surface

114‧‧‧ Fresnel invalid face

1141‧‧‧First Fresnel Invalid Face

1142‧‧‧Second Fresnel Invalid Face

1143‧‧‧ Third Fresnel Invalid Face

1144‧‧‧Four Fresnel Invalid Face

1145‧‧‧Five Fresnel Invalid Face

I‧‧‧ optical axis

L‧‧‧Connected straight line

L1‧‧‧ first connection line

L2‧‧‧Second connection line

L3‧‧‧ third connecting line

L4‧‧‧fourth connecting straight line

L5‧‧‧ fifth connection straight line

S‧‧‧ teeth

SC‧‧‧Central tooth

SP‧‧‧ peripheral teeth

SP1‧‧‧first peripheral tooth

SP2‧‧‧Second peripheral tooth

SP3‧‧‧ Third peripheral tooth

SP4‧‧‧4th peripheral tooth

SP5‧‧‧ fifth peripheral tooth

SG‧‧‧ tooth depth

SGc‧‧‧ tooth depth of the central tooth

SG _p ‧‧‧ tooth depth of the peripheral teeth

P‧‧‧ pitch

Pc‧‧‧ the pitch of the central tooth

P _p ‧‧‧ pitch of the surrounding teeth

RL‧‧ reference line

RL1‧‧‧ first reference line

RL2‧‧‧ second reference line

RL3‧‧‧ third reference line

RL4‧‧‧ fourth reference line

RL5‧‧‧ fifth reference line

RP‧‧‧ reference plane

X‧‧‧X axis

Y‧‧‧Y axis

Z‧‧‧Z axis

Θ‧‧‧ draft angle

Θ1‧‧‧first draft angle

Θ2‧‧‧second draft angle

Θ3‧‧‧ third draft angle

θ 4‧‧‧four draft angle

θ 5‧‧‧ fifth draft angle

1 to 4 are schematic cross-sectional views of a Fresnel lens according to various embodiments of the present invention.

Claims (10)

A Fresnel lens comprising: a Fresnel surface comprising a plurality of Fresnel effective faces for passing imaging light, and two adjacent Fresnel effective faces being interconnected by a Fresnel ineffective surface; One of the Fresnel ineffective faces on one of the sections including an optical axis of the Fresnel lens is located at one end of the tooth peak of the Fresnel lens and a connection at one end of the valley of the Fresnel lens The straight line and a reference line have a draft angle, the reference line is parallel to the optical axis and passes through the Fresnel effective surface at one end of the tooth peak, the optical axis coincides with the cross section, and the angle of each draft angle Less than 90 degrees; wherein the draft angles include a first draft angle calculated from the optical axis radially outward, and a second from the optical axis radially outward a second draft angle, a third draft angle calculated from a radially outward direction of the optical axis, and a fourth fourth draft angle calculated from a radially outward direction of the optical axis a fifth draft angle calculated as a fifth from the optical axis radially outward; wherein the second draft angle is greater than the first draft angle, the third draft angle In the second draft angle, the fourth draft angle is greater than the third draft angle, and the fifth draft angle is greater than the fourth draft angle, wherein the Fresnel lens meets the following conditional formula: 0.05 Mm ≦ P ≦ 0.60 mm, where P is the pitch of the teeth of the Fresnel face. The Fresnel lens of claim 1, wherein each draft angle is greater than or equal to 1° and less than or equal to 25°. The Fresnel lens of claim 1, wherein the draft angle further comprises a sixth draft angle calculated as a sixth from the optical axis radially outward, and an optical axis from the optical axis Calculated as a seventh seventh draft angle radially outward, an eighth draft angle calculated from the optical axis radially outward, and counting radially outward from the optical axis a ninth draft angle and a tenth draft angle calculated from the optical axis radially outward, and the sixth draft angle is greater than the fifth draft angle, the first The seventh draft angle is greater than the sixth draft angle, the eighth draft angle is greater than the seventh draft angle, the ninth draft angle is greater than the eighth draft angle, and the tenth draft angle is greater than the ninth Draft angle. The Fresnel lens of claim 1, wherein the Fresnel ineffective faces are surfaces having a curvature in a cross-sectional direction. The Fresnel lens of claim 1, wherein the plurality of teeth of the Fresnel face comprise a central tooth from the radially outward direction of the optical axis and a plurality of peripheral teeth, wherein the peripheral teeth are The pitches in the direction perpendicular to the optical axis are identical to each other, wherein the pitch of each peripheral tooth in a direction perpendicular to the optical axis is defined as the valley of each peripheral tooth on the side close to the optical axis and away from The distance between the valleys of one side of the optical axis in a direction perpendicular to the optical axis. The Fresnel lens of claim 5, wherein a pitch of the central tooth in a direction perpendicular to the optical axis is the same as a pitch of each peripheral tooth in a direction perpendicular to the optical axis, Wherein the pitch of the central tooth in a direction perpendicular to the optical axis is defined as a valley from the optical axis to the central tooth and a peripheral tooth closest to the central tooth in a direction perpendicular to the optical axis the distance. The Fresnel lens of claim 1, wherein the plurality of teeth of the Fresnel face comprise a central tooth from the radially outward direction of the optical axis and a plurality of peripheral teeth, the peripheral teeth being parallel The depths of the teeth in the direction of the optical axis are identical to each other, wherein the depth of the teeth of each of the peripheral teeth in a direction parallel to the optical axis is defined as the Fresnel ineffective face of the peripheral tooth on the section containing the optical axis The distance from one end of the tooth peak of the peripheral tooth to the end of the tooth valley of the peripheral tooth in a direction parallel to the optical axis. The Fresnel lens of claim 7, wherein the central tooth has a tooth depth in a direction parallel to the optical axis that is the same as a tooth depth of each peripheral tooth in a direction parallel to the optical axis, The depth of the tooth in the direction parallel to the optical axis of the central tooth is defined as the distance of the apex of the central tooth at the optical axis to the valley of the edge of the central tooth in a direction parallel to the optical axis. The Fresnel lens of claim 8, wherein the Fresnel lens conforms to the following conditional formula: 0.001 mm ≦S ≦ 0.400 mm, where S is the depth of each tooth of the Fresnel face. The Fresnel lens of claim 1, wherein on the one side of the Fresnel lens, the plurality of Fresnel ineffective faces have a plurality of cut lines on the cross section on a reference plane The sum of the lengths of the positive projections divided by the sum of the lengths of the plurality of orthographic projections of the plurality of sections of the Fresnel effective plane on the reference plane is less than or equal to 0.230, wherein the reference The plane is perpendicular to the optical axis.