CN111726488B

CN111726488B - Optical system

Info

Publication number: CN111726488B
Application number: CN202010479109.3A
Authority: CN
Inventors: 李佳妮; 若林央; 陈扬辉
Original assignee: Shenzhen Bosen Photoelectric Technology Co ltd
Current assignee: Shenzhen Bosen Photoelectric Technology Co ltd
Priority date: 2020-05-29
Filing date: 2020-05-29
Publication date: 2022-07-08
Anticipated expiration: 2040-05-29
Also published as: WO2021237840A1; CN111726488A

Abstract

The invention provides an optical system. The optical system includes: at least one aspherical lens, which is formed of plastic and is a lens commonly used in various optical systems; and at least one spherical lens formed of glass that can be replaced to change the optical performance of the optical system. Thus, an optical system with diversified optical performances can be provided, which is low in cost, small in size, high in performance and the like.

Description

Optical system

Technical Field

The present invention relates to an optical system, and more particularly, to an optical system capable of replacing a lens.

Background

With respect to optical systems such as a monitoring camera and an in-vehicle camera, the market requires diversification of the angle of view, the focal length, the kind of a sensor, and the like of a lens. In particular, in the vehicle-mounted camera, specifications for observation and automation are required to be diversified depending on applications (for example, monitoring the front, monitoring the rear, observing the conditions in the vehicle, and the like) and vehicle types. Further, the diversification is demanded, and cost reduction, miniaturization, high performance, and the like are demanded.

In an optical system such as a monitoring camera or an in-vehicle camera, the use of a plastic aspherical lens is effective for cost reduction, downsizing, and high performance. However, although the cost of the components of the plastic aspherical lens is low, the cost of the mold for manufacturing the plastic aspherical lens is considerably high. In the case of producing optical systems with diversified optical properties, different molds are required to be prepared to manufacture different plastic aspherical lenses, which results in high cost on the molds, and thus not only does not reduce the cost of the optical system, but also increases the cost of the optical system.

Disclosure of Invention

Problems to be solved by the invention

The invention provides an optical system with low cost, miniaturization, high performance and diversified optical performance.

Means for solving the problems

To achieve the above object, an embodiment of the present invention provides an optical system including: at least one aspherical lens, which is formed of plastic and is a lens commonly used in various optical systems; and at least one spherical lens formed of glass that can be replaced to change the optical performance of the optical system.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the above configuration, the use of the plastic aspherical lens enables downsizing, high performance, and cost reduction of the component itself, and the plastic aspherical lens having a high mold cost is used in common in various optical systems, thereby reducing initial cost input and cost reduction. Further, by replacing the glass spherical lens with a less initial cost without using a mold, the optical performance such as a change in the angle of view and diversification of the sensor can be diversified. Thus, the initial cost and the cost of the component are both reduced, and an optical system with diversified optical performances, which is low in cost, small in size, high in performance, and the like, can be provided.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention.

Fig. 1 is a configuration diagram of an imaging apparatus 10 of embodiment 1.

Fig. 2 is a structural diagram of an imaging device 20 in which a glass spherical lens in the imaging device 10 is replaced in example 1.

Fig. 3 is a view of the field of view of the lens unit 100 of embodiment 1 as a function of MTF.

Fig. 4 is a view of the field of view of the lens unit 200 of embodiment 1 as a function of MTF.

Fig. 5 is a structural diagram of the image pickup apparatus 30 of embodiment 2.

Fig. 6 is a structural diagram of an imaging device 40 in which a glass spherical lens in the imaging device 30 is replaced in example 2.

Fig. 7 is a view of the field of view of the lens unit 300 of embodiment 2 as a function of MTF.

Fig. 8 is a view of the field of view of the lens unit 400 of embodiment 2 as a function of MTF.

Description of the reference numerals

10-40: a camera device; 100-400: a lens unit; 110-410: a first lens group; 120-420: a second lens group; 130 to 430: a diaphragm; L1-L6: first to sixth lenses; 500: a flat glass filter; 600. 700: an image sensor.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Further, in the drawings, like reference numbers indicate functionally identical or similar elements. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In some instances, methods, procedures, components, and circuits that are well known to those skilled in the art have not been described in detail so as not to obscure the present invention.

The optical system of the embodiment of the invention is composed of a plastic aspheric lens and a glass spherical lens, wherein the plastic aspheric lens is generalized in various optical systems, the glass spherical lens is replaceable, and the optical system with the replaceable lens and the variable focal length is formed by the generalized plastic aspheric lens and the replaced different glass spherical lens.

In other words, the optical system includes: at least one aspherical lens, which is formed of plastic and is a lens commonly used in various optical systems; and at least one spherical lens formed of glass that can be replaced to change the optical performance of the optical system.

Thus, the use of the plastic aspherical lens enables miniaturization, high performance, and cost reduction of the component itself, and the plastic aspherical lens with high mold cost is used in common in various optical systems, thereby reducing initial cost input and cost reduction. Further, diversification of optical performance such as change of a viewing angle and diversification of a sensor is realized by replacing a glass spherical lens which does not require a mold and requires a small initial cost. Thus, the initial cost and the cost of the component are both reduced, and an optical system with diversified optical performances, which is low in cost, small in size, high in performance, and the like, can be provided.

For example, the total number of lens pieces of the optical system is 6, wherein 3 lens pieces are plastic aspheric lenses, and 3 lens pieces are glass spherical lenses. By using 3 plastic aspherical lenses, the resolving power of the optical system can be improved. In addition, the volume of the optical system can be reduced, and the optical system can be miniaturized. In addition, 3 plastic aspherical lenses are generalized, and thus the development cost of the optical system is reduced.

For example, the 6 lenses may be composed of a first glass spherical lens L1, a second glass spherical lens L2, a third plastic aspherical lens L3, a fourth glass spherical lens L4, a fifth plastic aspherical lens L5, and a sixth plastic aspherical lens L6, which are arranged in order from the object side to the image side, wherein the first lens L1, the second lens L2, and the fifth lens L5 are all concave lenses, and the third lens L3, the fourth lens L4, and the sixth lens L6 are all convex lenses. By providing the positive and negative lenses at an interval, chromatic aberration of the optical system can be effectively corrected. Preferably, the first lens L1 and the second lens L2 are meniscus concave lenses, the third lens L3 is a meniscus convex lens, the fourth lens L4 and the sixth lens L6 are double convex lenses, and the fifth lens L5 is a double concave lens.

In addition, the focal length of the third lens L3 and the combined focal length of the fifth lens L5 and the sixth lens L6 satisfy the following conditional expressions:

4<f3/f<8,

40<|f56|/f<80

where f3 is the focal length of the third lens L3, f56 is the combined focal length of the fifth lens L5 and the sixth lens L6, and f is the focal length of the optical system.

When the three lenses of the third lens L3, the fifth lens L5, and the sixth lens L6 satisfy the above conditional expressions, the focal lengths of the three lenses are limited to a certain range. Since the three lenses of the third lens L3, the fifth lens L5, and the sixth lens L6 are common lenses, the focal lengths of the three lenses are limited to a certain range, and thus the difficulty in matching with a glass lens to be replaced can be reduced.

The optical system may be an optical system including a first lens group having negative refractive power, a stop, a second lens group having positive refractive power, and a flat glass filter, which are arranged in this order from the object side to the image side, wherein the first lens group includes 3 lenses, and the second lens group includes 3 lenses.

For example, the first lens group includes first to third lenses L1 to L3 arranged in order from the object side to the image side, the second lens group includes fourth to sixth lenses L4 to L6 arranged in order from the object side to the image side, the first lens L1 and the second lens L2 are concave lenses of a glass spherical surface, the third lens L3 is a convex lens of a plastic aspherical surface, the fourth lens L4 is a convex lens of a glass spherical surface, the fifth lens L5 is a concave lens of a plastic aspherical surface, and the sixth lens L6 is a convex lens of a plastic aspherical surface. Preferably, the first lens L1 and the second lens L2 are meniscus concave lenses of a glass spherical surface, the third lens L3 is a plastic aspherical meniscus convex lens, the fourth lens L4 is a glass spherical double convex lens, the fifth lens L5 is a plastic aspherical double concave lens, and the sixth lens L6 is a plastic aspherical double convex lens.

In addition, the surface shapes of the aspherical lenses in the optical system all satisfy the following conditional expressions:

wherein z is a distance between a point on the curved surface of the aspherical lens and a vertex of the curved surface in the optical axis direction, y is a distance between a point on the curved surface of the aspherical lens and the optical axis, c is a curvature at the vertex of the curved surface, k is a conic coefficient, and B, C, D, E, F are a fourth-order coefficient, a sixth-order coefficient, an eighth-order coefficient, a tenth-order coefficient, and a twelfth-order coefficient, respectively.

The above conditional expression is an aspherical functional expression, and the aspherical shape determined by the functional expression has a characteristic of axial symmetry, and therefore, a mold for an aspherical lens having an aspherical shape determined by the functional expression is easily manufactured. In addition, since the difficulty of manufacturing the mold for the aspherical lens is low, the manufacturing cost of the mold for the aspherical lens is also low.

In the present invention, the relationship between the angle of view and the image height is referred to as a projection system. In the optical system of the present embodiment, the projection system is fixed regardless of the change in the focal length, that is, the projection system always performs equidistant projection regardless of the change in the focal length. Since it is necessary to change the aspherical lens of the optical system to change the projection system of the optical system, the aspherical lens can be used in common by always making the projection system of the optical system equidistant.

For example, the projection may be an equidistant projection. The equidistant projection mode can ensure that the corresponding radial distances of objects positioned at the same field angle on the image surface are equal, so that the spatial angular coordinate information of the target object can be conveniently extracted from the image, and the extraction of the information of the target object has good real-time performance.

Hereinafter, an embodiment of an optical system will be described in detail with reference to the drawings, taking an image pickup apparatus as an example.

Example 1

Fig. 1 is a configuration diagram of an image pickup apparatus 10 according to embodiment 1. As shown in fig. 1, the image pickup device 10 has a lens unit 100, an image sensor 600 such as a CMOS or CCD, and a flat glass filter 500 provided between the lens unit 100 and the image sensor 600. The image sensor 600 has a photosensitive surface IS. The flat glass filter 500 is a filter for cutting light of a specific wavelength. Although not shown, the imaging device 10 has a fixing mechanism for fixing the lens unit 100, the flat glass filter 500, and the image sensor 600.

The lens unit 100 includes a first lens group 110 having negative power, a stop 130, and a second lens group 120 having positive power, which are arranged in order from the object side to the image side. The first lens group 110 is composed of a first lens L1, a second lens L2, and a third lens L3 arranged in order from the object side to the image side, the second lens group 120 is composed of a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged in order from the object side to the image side, the first lens L1 and the second lens L2 are meniscus concave lenses of a glass spherical surface protruding to the object side, the third lens L3 is a meniscus convex lens of a plastic aspherical surface protruding to the image side, the fourth lens L4 is a double convex lens of a glass spherical surface, the fifth lens L5 is a double concave lens of a plastic aspherical surface, and the sixth lens L6 is a double convex lens of a plastic aspherical surface.

Fig. 2 is a structural diagram of an imaging device 20 in which a glass spherical lens in the imaging device 10 is replaced in example 1. As shown in fig. 2, the image pickup device 20 includes a lens unit 200, an image sensor 600 such as a CMOS or CCD, and a flat glass filter 500 provided between the lens unit 200 and the image sensor 600, and the image sensor 600 has a light-sensing surface IS. The flat glass filter 500 is a filter for cutting light of a specific wavelength. Although not shown, the imaging device 20 includes a fixing mechanism for fixing the lens unit 200, the flat glass filter 500, and the image sensor 600.

The lens unit 200 includes a first lens group 210 having negative power, a stop 230, and a second lens group 220 having positive power, which are arranged in order from the object side to the image side. The first lens group 210 is composed of a first lens L1 ', a second lens L2', and a third lens L3, which are arranged in order from the object side to the image side, the second lens group 220 is composed of a fourth lens L4 ', a fifth lens L5, and a sixth lens L6, which are arranged in order from the object side to the image side, the first lens L1' and the second lens L2 'are meniscus concave lenses having a glass spherical surface and protruding toward the object side, the third lens L3 is a meniscus convex lens having a plastic aspherical surface and protruding toward the image side, the fourth lens L4' is a double convex lens having a glass spherical surface, the fifth lens L5 is a double concave lens having a plastic aspherical surface, and the sixth lens L6 is a double convex lens having a plastic aspherical surface.

In the lens unit 200 of the present embodiment, 3 plastic aspherical lenses, i.e., the third lens L3, the fifth lens L5, and the sixth lens L6 are the same as the

lens unit

100, and 3 glass spherical lenses, i.e., the first lens L1 ', the second lens L2 ', and the fourth lens L4 ' are different from the lens unit 100.

In the lens unit 100 and the lens unit 200 of the present embodiment, 3 plastic aspherical lenses, that is, the third lens L3, the fifth lens L5, and the sixth lens L6 are used, so that the resolving power of the optical system can be improved, and the volume of the lens unit 100 and the lens unit 200 can be reduced, thereby downsizing the lens unit 100 and the lens unit 200. In addition, since the 3-piece plastic aspherical lens is commonly used in the imaging device 10 and the imaging device 20, the development cost of the optical system is reduced.

In the lens unit 100 (lens unit 200) of the present embodiment, the first lens L1 (first lens L1 '), the second lens L2 (second lens L2 '), and the fourth lens L4 (fourth lens L4 ') are glass spherical lenses that are designed independently in accordance with the imaging requirements of the imaging device 10 (imaging device 20). In the lens unit 100 and the lens unit 200 of the present embodiment, different focal lengths and different viewing angle ranges can be obtained on the same image sensor by using different 3 glass spherical lenses and matching with a common 3 plastic aspheric lens.

The lens unit 100 of the image pickup apparatus 10 of the present embodiment has a focal length f of 1.92mm, an f-number f/# of 2.2, a horizontal angle of view of 180 °, and a total length TTL of 20.3 mm.

In the imaging device 10 of embodiment 1, the projection method is equidistant projection (y ═ f θ). This is the most suitable way for so-called fisheye lenses with a horizontal viewing angle of 180.

The lens unit 200 of the image pickup apparatus 20 of the present embodiment has a focal length f of 2.59mm, an f-number f/# of 2.2, a horizontal angle of view of 128 °, and a total length TTL of 18.3 mm.

In the case of a horizontal viewing angle of 128 °, although the projection method y ═ f tan θ is generally used in many cases, the projection method is equidistant projection (y ═ f θ) in the present embodiment. Since the aspheric lens needs to be changed to change the projection method, the imaging device 10 and the imaging device 20 according to the present embodiment can be used in common by making the projection method equal in distance (y ═ f θ).

For example, the design parameters of the lens unit 100 of the present embodiment are shown in table 1-1. The surface radius and thickness are in mm.

TABLE 1-1

For example, the design parameters of the lens unit 200 of the present embodiment are shown in tables 1-2. The surface radius and thickness are in mm.

Tables 1 to 2

For example, aspherical parameters of the third lens, the fifth lens, and the sixth lens of the

lens units

100 and 200 of the present embodiment are shown in tables 1 to 3.

Tables 1 to 3

Fig. 3 is a view of the lens unit 100 of the present embodiment as a function of MTF. Fig. 4 is a view field versus MTF of the lens unit 200 of the present embodiment.

Example 2

Fig. 5 is a structural diagram of the image pickup apparatus 30 of embodiment 2. As shown in fig. 5, the image pickup device 30 has a lens unit 300, an image sensor 700 such as a CMOS or CCD, and a flat glass filter 500 provided between the lens unit 300 and the image sensor 700. The image sensor 700 has a photosensitive surface IS. The flat glass filter 500 is a filter for cutting light of a specific wavelength. Although not shown, the imaging device 30 includes a fixing mechanism for fixing the lens unit 300, the flat glass filter 500, and the image sensor 700.

The lens unit 300 includes a first lens group 310 having negative power, a stop 330, and a second lens group 320 having positive power, which are arranged in order from the object side to the image side. The first lens group 310 is composed of a first lens L1, a second lens L2, and a third lens L3 arranged in order from the object side to the image side, the second lens group 320 is composed of a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged in order from the object side to the image side, the first lens L1 and the second lens L2 are meniscus concave lenses of a glass spherical surface protruding to the object side, the third lens L3 is a meniscus convex lens of a plastic aspherical surface protruding to the image side, the fourth lens L4 is a double convex lens of a glass spherical surface, the fifth lens L5 is a double concave lens of a plastic aspherical surface, and the sixth lens L6 is a double convex lens of a plastic aspherical surface.

Fig. 6 is a configuration diagram of an imaging device 40 of example 2, in which a glass spherical lens in the imaging device 30 is replaced. As shown in fig. 6, the image pickup device 40 includes a lens unit 400, an image sensor 700 such as a CMOS or CCD, and a flat glass filter 500 provided between the lens unit 400 and the image sensor 700. The image sensor 700 has a photosensitive surface IS. The flat glass filter 500 is a filter for cutting light of a specific wavelength. Although not shown, the imaging device 40 has a fixing mechanism for fixing the lens unit 400, the flat glass filter 500, and the image sensor 700.

The lens unit 400 includes a first lens group 410 having negative power, a stop 430, and a second lens group 420 having positive power, which are arranged in order from the object side to the image side. The first lens group 410 is composed of a first lens L1 ', a second lens L2', and a third lens L3, which are arranged in order from the object side to the image side, the second lens group 420 is composed of a fourth lens L4 ', a fifth lens L5, and a sixth lens L6, which are arranged in order from the object side to the image side, the first lens L1' and the second lens L2 'are meniscus concave lenses having a glass spherical surface and protruding toward the object side, the third lens L3 is a meniscus convex lens having a plastic aspherical surface and protruding toward the image side, the fourth lens L4' is a double convex lens having a glass spherical surface, the fifth lens L5 is a double concave lens having a plastic aspherical surface, and the sixth lens L6 is a double convex lens having a plastic aspherical surface.

In the lens unit 400 of the present embodiment, 3 plastic aspherical lenses, i.e., the third lens L3, the fifth lens L5, and the sixth lens L6 are the same as the

lens unit

300, and 3 glass spherical lenses, i.e., the first lens L1 ', the second lens L2 ', and the fourth lens L4 ' are different from the lens unit 300.

In the lens unit 300 and the lens unit 400 of the present embodiment, 3 plastic aspherical lenses, that is, the third lens L3, the fifth lens L5, and the sixth lens L6 are used, so that the resolving power of the optical system can be improved, and the volume of the lens unit 300 and the lens unit 400 can be reduced, thereby miniaturizing the lens unit 300 and the lens unit 400. In addition, since the 3-piece plastic aspherical lens is commonly used in the image pickup device 30 and the image pickup device 40, the development cost of the optical system is reduced.

In the lens unit 300 (lens unit 400) of the present embodiment, the first lens L1 (first lens L1 '), the second lens L2 (second lens L2 '), and the fourth lens L4 (fourth lens L4 ') are glass spherical lenses designed independently in accordance with the imaging requirements of the imaging device 30 (imaging device 40). In the lens unit 300 and the lens unit 400 of the present embodiment, different focal lengths and different viewing angle ranges can be obtained on the same image sensor by using different 3 glass spherical lenses and matching with a common 3 plastic aspheric lens.

The lens unit 300 of the image pickup apparatus 30 of the present embodiment has a focal length f of 1.86mm, an f-number f/# of 2.2, a horizontal angle of view of 180 °, and a total length TTL of 20.0 mm.

The lens unit 400 of the image pickup apparatus 40 of the present embodiment has a focal length f of 2.48mm, an f-number f/# of 2.2, a horizontal field angle of 125 °, and a total length TTL of 18.7 mm.

The projection systems of the imaging device 30 and the imaging device 40 are the same as those of the imaging device 10 and the imaging device 20, and are equidistant projection (y ═ f θ).

For example, the design parameters of the lens unit 300 of the present embodiment are shown in table 2-1. The surface radius and thickness are in mm.

TABLE 2-1

The design parameters of the lens unit 400 of the present embodiment are shown in table 2-2. The surface radius and thickness are in mm.

Tables 2 to 2

Aspherical parameters of the third lens, the fifth lens and the sixth lens of the

lens unit

100 or 200 of the present embodiment are shown in tables 2 to 3.

Tables 2 to 3

Fig. 7 is a view field versus MTF of the lens unit 300 of the present embodiment. Fig. 8 is a view field versus MTF of the lens unit 400 of the present embodiment.

Example 3

In the

lens units

100 and 200 of embodiment 1 and the

lens units

300 and 400 of embodiment 2, the plastic aspherical lenses L3, L5, and L6 are commonly used, and only the glass spherical lenses L1, L2, and L4 need to be replaced to meet the requirements of different imaging devices.

The

lens units

100 and 200 of embodiment 1 and the

lens units

300 and 400 of embodiment 2 are devices that can satisfy the requirement of using the same image sensor to achieve different focal lengths and angles of view. Therefore, it is conceivable to realize the same f-number and angle of view using different image sensors by combining the image pickup device 10 with the image pickup device 30 or the image pickup device 40, or combining the image pickup device 20 with the image pickup device 30 or the image pickup device 40.

By designing the plastic aspheric lens with high research and development cost to be universal in various lens units, the research and development cost and period of various lens units can be greatly reduced, the utilization rate of the plastic aspheric mold is improved, and the production cost is reduced.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An optical system comprising a glass spherical lens and a plastic aspherical lens, characterized by comprising a front group located in front of a diaphragm and a rear group located behind the diaphragm,

the front group and the rear group are respectively composed of a glass spherical lens and a plastic aspherical lens,

in each of said front group and said rear group, at least one of the front lenses is a glass spherical lens and the rear lens is a plastic aspherical lens,

the optical performance of the optical system is changed by replacing the glass spherical lens.

2. The optical system according to claim 1,

the optical property that is changed is the focal length.

3. The optical system according to claim 2,

the glass spherical lenses are all replaced simultaneously.

4. The optical system according to claim 3,

the front group consists of three lenses, the first lens and the second lens are concave lenses of a glass spherical surface, the third lens is a convex lens of a plastic aspheric surface, the rear group consists of three lenses, the fourth lens is a convex lens of a glass spherical surface, the fifth lens is a concave lens of a plastic aspheric surface, and the sixth lens is a convex lens of a plastic aspheric surface.

5. The optical system according to claim 4,

the following conditional expressions are satisfied:

4<f3/f<8

40<|f56|/f<80

wherein f3 is the focal length of the third lens,

f56 is the combined focal length of the fifth and sixth lenses,

f is the focal length of the optical system.

6. The optical system according to claim 1,

the optical system comprises a first lens group with negative focal power, a diaphragm, a second lens group with positive focal power and a plane glass filter, wherein the first lens group, the diaphragm, the second lens group with positive focal power and the plane glass filter are sequentially arranged from the object side to the image side, the first lens group consists of 3 lenses, and the second lens group consists of 3 lenses.

7. The optical system according to claim 6,

the first lens group consists of a first lens, a second lens and a third lens which are sequentially arranged from the object side to the image side, the second lens group consists of a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from the object side to the image side, the first lens and the second lens are concave lenses of glass spherical surfaces, the third lens is a convex lens of plastic aspherical surfaces, the fourth lens is a convex lens of glass spherical surfaces, the fifth lens is a concave lens of plastic aspherical surfaces, and the sixth lens is a convex lens of plastic aspherical surfaces.

8. The optical system according to claim 1,

each aspheric lens in the optical system satisfies the following conditional expression:

wherein z is a distance between a point on the curved surface of the aspherical lens and a vertex of the curved surface in the optical axis direction,

y is the distance between a point on the curved surface of the aspherical lens and the optical axis,

c is the curvature at the apex of the curved surface,

k is a coefficient of a quadratic surface,

b is a coefficient of a fourth-order surface,

c is a coefficient of a sixth-order surface,

d is the coefficient of the surface of the eighth order,

e is a coefficient of a surface of a tenth order,

f is a coefficient of the twelve-order surface.

9. The optical system according to claim 1,

the projection mode of the optical system is fixed.

10. The optical system according to claim 9,

the projection mode of the optical system is an equidistant projection mode.