TWI479181B - Optical module - Google Patents

Description

Optical module

The invention relates to an optical module for capturing images by a mobile phone, in particular to an optical module comprising four lenses.

At present, the development trend of mobile phones is getting thinner and thinner, and the requirements for resolution of mobile phone lenses are getting higher and higher. Therefore, mobile phone lenses need to be specially designed to meet the requirements of high resolution. The lens is generally assembled by fixing one to several lenses and apertures through the lens holder. For the lens that sells a large number of markets, because it needs to produce tens of thousands of lenses every day, it is foreseeable that it is good for production. The rate requirement is almost 100%, so special attention must be paid to its manufacturing capabilities.

The restrictions on lens design depend mainly on the specifications proposed by the customer. The main specifications include the following:

Effective Focal Length

The effective focal length will determine the overall dimensions of the lens. The term effective focal length mentioned below will be replaced by the English EFL.

Back Focal Length

Back focal length (BFL) is the image side of the lens closest to the image sensor The distance from the vertex to the sensing surface of the image sensor on the optical axis.

Convergence

The convergence C is equal to the reciprocal of the EFL and may also be referred to as the refractive power of the lens.

Field of View

The EFL value and the image size of the focal plane of the lens determine the size of the viewing angle. The term angle of view will be replaced by the English FOV. When a circular image with a diameter equal to D and its image center is at the intersection of the optical axis and the focal plane of the lens, the FOV value can be obtained by the following formula: FOV=2. Arctan[D/(2.EFL)] where Arctan is the inverse of the tangent of the angle.

When the image is rectangular and its image center point is at the intersection of the optical axis and the image plane, the D value in the above formula is the diagonal length of the rectangular image.

For the definition of the position of any point on the image, the common practice is defined by height or angle. The height refers to the distance from any point on the image to the center of the image. The angle refers to any point on the image and the center point of the image. The angle of view corresponding to the line segment, both expressed as a percentage relative to the maximum half angle of view, is recorded as x% hFOV.

In the field of lens design, we all know that the larger the angle of view, the larger the geometric aberration. Under this condition, it is difficult to design a lens. High resolution and low astigmatism.

Aperture Number F#

The aperture in the lens is mainly used to control the amount of light entering the lens. The aperture size and EFL value determine the aperture value of the lens. The aperture value is equal to EFL divided by the aperture diameter. The aperture value is represented by F#.

When the aperture is used to control the amount of light entering the lens, the aperture is often referred to as the diaphragm.

The aperture value mainly affects four important parameters, including the amount of light reaching the image sensor. The amount of light is inversely proportional to the square of the aperture value. Depth of field (DoF), hyperfocal distance (HyF), and hyperfocal distance refer to the lens. When focusing on the hyperfocal distance, the object can be clearly imaged from the image sensor at a distance from the lens to the infinity of the lens, and the depth of focus (dof), the depth of focus refers to the image sensing The error value of the position relative to the lens does not affect the image sharpness within the error value range.

Resolution

Resolution is the modulation transfer function (MTF) measured at a particular spatial frequency. The resolution is used to describe the contrast of a lens for consecutive black-and-white strip images of the same width, each pair of black and white strips. The width of the image is equal to the reciprocal of the spatial frequency.

MTF is usually expressed as a percentage of the maximum possible contrast, for For a given shot, the MTF is between 0% and 100% and the maximum MTF is 100%.

The spatial frequency is expressed as the pair value in each millimeter, and the Line Pair Per Millimeters is abbreviated to lppm.

Aberrations

Aberrations include geometric aberrations and chromatic aberrations.

Geometric aberrations include geometric distortion, astigmatism, and EFL differences in different regions of the image. Geometric aberrations depend on the curvature of the lens and the aspheric coefficients that define the depressions on the lens surface.

Chromatic aberrations include colored stripes (the edges of the object are surrounded by various colors that are parallel to the edge of the object) and color regions (for example, white images appear pink at the corners).

Targeted Costs

The target cost mainly depends on the number of lenses constituting the lens, and the present invention can achieve the reduction of the aberration by balancing the convergence between the lenses, instead of increasing the number of lenses to achieve the reduction of the aberration.

More details on EFL, C, BFL, FOV, MTF, and F# can be found in the academic literature, such as Modern Optical by Warren J Smith, published by McGraw Hill. It can be found in the Engineer's book.

Because there are many specifications, people can understand that the lens is actually designed according to some special specifications. However, many mobile phone manufacturers will develop several lenses with different specifications (EFL, FOV, etc. according to the same image sensor). Specifications such as MTF have changed slightly). It is possible to design a versatile lens that allows various design parameters to be varied within a certain range.

There are a number of lenses described in the prior art, which are composed of four lenses or four groups of lenses, such as Japanese Patent No. JP2003098428, JP2007108770, JP7098430, JP11190820, and US Pat. No. 5,367,405, the limitations of which include the type of lens used, the focal length of the lens, and Aspherical surfaces specially designed for special applications are different from the present invention.

The invention provides an optical module comprising a first lens, a second lens, a third lens and a fourth lens from the object side to the image side. The first lens is a positive refractive power concave-convex lens comprising a first optical surface and a second optical surface, the first optical surface being convex and facing the object side. The second lens is a meniscus lens having a negative refractive power, comprising a third optical surface and a fourth optical surface, the third optical surface facing the object side. The third lens is a positive refractive power convex lens, including a fifth The optical surface and a sixth optical surface, the fifth optical surface being concave and facing the object side, the sixth optical surface being convex and facing the image side. The fourth lens is a lens having a negative refractive power, comprising a seventh optical surface and an eighth optical surface, the seventh optical surface facing the object side.

Wherein, if C1 is the convergence of the first lens and C is the convergence of the optical module, then 1.1 C 1/ C 1.35.

Wherein, if C1 is the convergence of the first lens and C2 is the convergence of the second lens, then | C 1/ C 2| 2.

Wherein, if C1 is the convergence of the first lens and C3 is the convergence of the third lens, then 0.5 C 1/ C 3 1.1.

Wherein, if C1 is the convergence of the first lens, and Vd1 is the Abbe coefficient of the first lens, then C1/Vd1 5.2.

Wherein, if C2 is the convergence of the second lens and Vd2 is the Abbe coefficient of the second lens, then |C2/Vd2| 7.

Wherein, if Ci is the convergence of the ith lens, Vdi is the Abbe coefficient of the ith lens, i=1, 2, 3, 4, then |Σ(Ci/Vdi)| 4.

Wherein, when the wavelength is 0.555 micrometers and the spatial frequency is 89 lppm, the optical modulation center modulation transfer function (MTF) value is greater than or equal to 75%.

Wherein, when the half angle of view is 50%, the wavelength is 0.555 micrometer, and the spatial frequency is 89 lppm, the difference between the sagittal direction and the meridional modulation transfer function (MTF) of the optical module is less than 8%; when the half angle of view is 90%, Wavelength is At 0.555 micron and a spatial frequency of 89 lppm, the difference between the sagittal direction and the meridional modulation transfer function (MTF) of the optical module is less than 15%.

Wherein, when the half angle of view is 50%, the wavelength is 0.555 micrometer, and the spatial frequency is 89 lppm, the sagittal MTF value of the optical module is greater than or equal to 70%, and the meridional to MTF value is greater than or equal to 65%.

Wherein, when the half angle of view is 90%, the wavelength is 0.555 micrometer, and the spatial frequency is 89 lppm, the sagittal MTF value of the optical module is greater than or equal to 58%, and the meridional to MTF value is greater than or equal to 51%.

The optical module may further include an aperture disposed between the first lens and the second lens or between the object side and the first lens.

The material of the first lens may be glass, and the material of the second, third, and fourth lenses may be plastic.

Alternatively, the first and second lenses are made of glass, and the third and fourth lenses are made of plastic.

Alternatively, the first and third lenses are made of glass, and the second and fourth lenses are made of plastic.

Among them, when the wavelength is 0.555 micron, the effective focal length (EFL) of the optical module is less than 4.4 mm.

Among them, when the wavelength is 0.555 micron, the effective focal length (EFL) of the optical module is less than 3.6 mm.

The optical module may further include an infrared filter and/or an image The sensor is disposed between the fourth lens and the image side.

The optical module has a viewing angle (FOV) between 63 degrees and 75 degrees.

The optical module may further include an image sensor disposed between the fourth lens and the image side, including five million pixels, each pixel area being less than or equal to 1.4 micrometers and 1.4 micrometers, arranged in a rectangular shape. The ratio of the long side to the short side of the array, rectangular array is about 4/3.

Alternatively, the image sensor comprises 7.9 million pixels, each pixel area is less than or equal to 1.4 micrometers and 1.4 micrometers, arranged in a rectangular array, and the ratio of the long side to the short side of the rectangular array is about 4 /3.

The above described objects, features, and advantages of the invention will be apparent from the description and appended claims

1 is a schematic illustration of a four-lens optical module 10 in accordance with an embodiment of the present invention.

The optical module 10 has an object side 12 and an image side 14, and includes a positive lens 16 having a positive refractive power from the object side 12 to the image side 14 having a focal length F1 and including a first optical surface 18 and a second The optical surface 20, the first optical surface 18 is convex and faces the object side 12.

The optical module 10 further includes a second lens 22 having a negative refractive power having a focal length F2 and including a third optical surface 24 and a fourth optical surface 26, the third optical surface 24 facing the object side 12.

The optical module 10 further includes a third lens 27 having a positive refractive power having a focal length F3 and including a fifth optical surface 28 and a sixth optical surface 29, the fifth optical surface 28 facing the object side 12 and being concave. The sixth optical surface 29 faces the image side 14 and is convex.

The optical module 10 further includes a fourth lens 30 having a negative refractive power having a focal length F4 and including a seventh optical surface 31 and an eighth optical surface 32, the seventh optical surface 31 facing the object side 12.

Preferably, the optical module 10 further includes an aperture 33 disposed between the first lens 16 and the second lens 22, or before the first lens 16, preferably the first lens 16 is made of glass. to make.

Preferably, the two optical surfaces of each of the four lenses are aspherical and each lens is made by molding.

According to the present invention, the overall refractive power of the optical module is distributed between the four lenses, and the positive refractive power lens and the negative refractive power lens respectively have a positive influence and a negative influence on the overall refractive power of the optical module.

According to the present invention, the refractive power of the first lens needs to be between 1.1 and 1.35 times the optical module refractive power, and the relationship between the two can be expressed by the following mathematical formula: Where C1 is the convergence of the first lens and C is the convergence of the entire optical module.

Further, according to the present invention, the absolute value of the ratio of the refractive power of the first lens to the refractive power of the second lens must be greater than or equal to 2, and the relationship between the two can be expressed by the following mathematical formula:

In addition, according to the present invention, the ratio of the refractive power of the first lens to the refractive power of the third lens needs to be between 0.5 and 1.1, and the relationship between the two can be expressed by the following mathematical formula:

If the high refractive power characteristics are concentrated on the first lens 16 and the third lens 27 without adding additional restrictions, high dispersion will result.

Since the EFL of a lens depends on its refractive index, for an optical module whose EFL is F, the dispersion Δf refers to the difference between the EFL values measured by the red line c and the blue line f of hydrogen at both ends of the visible spectrum. That is, Δf=EFL(Nc)-EFL(Nf).

According to the academic literature, a glass lens A that converges to Ca, has a refractive index of Nda, an Abbe's coefficient of Vda, and a glass lens B that converges to Cb, has a refractive index of Ndb, and has an Abbe's coefficient of Vdb is combined to have a convergence of C. A lenticular optical module, the two lenticular optical modules will have minimal dispersion when the underlying conditions are met: (Ca/Vda+Cb/Vdb) as close to zero as possible (~0)

It is assumed that Vdi represents the Abbe's coefficient of the i-th lens relative to the sodium yellow line (wavelength λ equals 587.56 nm) whose wavelength is in the middle of the visible spectrum.

When expanded into a multi-lens optical module, the above conditions will become as follows: Σ(Ci/Vdi)~0 (4)

Among them, Ci and Vdi are the convergence and Abbe coefficient of the ith lens, respectively.

Adding this condition means that the optical module must be composed of a lens with positive convergence and a lens with negative convergence, and then different materials are used to adjust the Abbe's coefficient to satisfy the condition (4).

The present invention includes alternating positive and negative lenses, and in addition, the lens according to the present invention is required to satisfy the underlying conditions (C is expressed in diopter):

Where i=1, 2, 3, 4 and Ci is the convergence of the i-th lens, Vdi is the Abbe coefficient of the i-th lens relative to the wavelength of the above-mentioned sodium yellow line, and the Abbe's coefficient Vdi is defined as Vdi=(Ndi -1) / (Nfi-Nci), where Ndi is the refractive index of the i-th lens relative to the yellow-yellow line whose wavelength is in the middle of the visible spectrum, and Nfi is the refractive index of the i-th lens relative to the blue line of hydrogen. Nci is the refractive index of the i-th lens relative to the red line of hydrogen.

It should be noted that when the first lens 16 has a relatively large refractive power C1 exceeding 250 diopters, it is easy to satisfy the condition (5) as long as Vd1>65.

Further, according to the four-lens optical module of the present invention, the lens satisfies the above conditions (1) to (3) and the conditions (5) to (7), which can greatly improve astigmatism and achieve high optical efficiency. performance. For example, according to the four-lens optical module of the present invention, when the wavelength is 0.555 micrometers and the spatial frequency is 89 lppm, the center (0% degree half angle, 0% degree hFOV) MTF is greater than or equal to 75%.

According to the optical module of the present invention, it is further shown that when the half angle of view is 50%, the wavelength is 0.555 micrometers, and the spatial frequency is 89 lppm, the difference between the sagittal direction and the MTF of the meridional direction is less than 8%. When the half angle of view is 90%, the wavelength is 0.555 micrometers, and the spatial frequency is 89 lppm, the difference between the sagittal direction and the MTF of the meridional direction is less than 15%.

According to the optical module of the preferred embodiment of the present invention, when the half angle of view is 50%, the wavelength is 0.555 micrometers, and the spatial frequency is 89 lppm, the sagittal MTF value is greater than or equal to 70%, and the meridional MTF value is greater than or equal to 65%.

According to the optical module of the preferred embodiment of the present invention, when the half angle of view is 90%, the wavelength is 0.555 micrometers, and the spatial frequency is 89 lppm, the sagittal MTF value is greater than or equal to 58%, and the meridional MTF value is greater than or equal to 51%.

An optical module according to a preferred embodiment of the present invention has a viewing angle of between 63 and 75 degrees. The inventors pointed out that the four-lens optical module according to the present invention has a viewing angle between 63 degrees and 75 degrees, and its full view. The angular MTF value and the meridional MTF value in the angular range can be well balanced. When using an image sensor with a diagonal length to focal length ratio between 1.27 and 1.55, the image resolution can reach 5 million paintings. Between the above and eight million pixels, the aperture value is less than 2.5.

Embodiments of the present invention will now be described in detail.

First Embodiment: EFL=4.22 mm (C=237) of optical module

Figure 2 is a schematic illustration of an optical module 210 in accordance with the present invention.

The optical module 210 has an object side 212 and an image side 214. The optical module includes a first lens 216 having a positive refractive power from the object side 212 to the image side 214, and has a focal length F1 and includes a first optical surface 218. And a second optical surface 220, the first optical surface 218 is convex and faces the object side 212.

The optical module 210 then includes a second lens 222 having a negative refractive power having a focal length F2 and including a third optical surface 224 and a fourth optical surface 226, the third optical surface 224 facing the object side 212.

The optical module 210 further includes a third lens 227 having a positive refractive power having a focal length F3 and including a fifth optical surface 228 and a sixth optical surface 229, the fifth optical surface 228 facing the object side 212 and being concave. The sixth optical surface 229 faces the image side 214 and is convex.

The optical module 210 further includes a fourth lens 230 having a negative refractive power, the focal length is F4 and includes a seventh optical surface 231 and a first The eight optical surface 232, the seventh optical surface 231 faces the object side 212.

The optical module 210 further includes a diaphragm or aperture 233 disposed between the first lens 216 and the second lens 222.

The optical module 210 can optionally include an infrared filter 240 disposed between the fourth lens 230 and the image side 214.

The optical module 210 can also optionally include an image sensor 250 disposed between the fourth lens 230 and the image side 214 (after the infrared filter 240). Alternatively, the optical module 210 can be used with the image sensor 250, but the image sensor 250 does not belong to a portion of the optical module.

According to an embodiment of the invention, the image sensor 250 includes at least 7.9 million pixels (arranged in a rectangular array), and the ratio of the long side to the short side approaches 4/3, and each pixel area Less than or equal to 1.4 microns multiplied by 1.4 microns.

According to another embodiment of the present invention, the image sensor 250 includes at least five million pixels (arranged in a rectangular array), and the ratio of the long side to the short side approaches 4/3, and each pixel area is smaller than Or equal to 1.4 microns multiplied by 1.4 microns.

The aperture value F# of the optical module 210 is equal to 2.5.

Its full viewing angle is equal to 67 degrees.

The material used in the lens has the following characteristics:

The optical module in Figure 2 has the following characteristics:

The optical module 210 completely satisfies the condition (1), the condition (2), the condition (3), the condition (5), the condition (6), and the condition (7).

Figure 3 is a schematic diagram of the half angle of view of the optical module 210 relative to the MTF. The graph shows the arc labeled as a percentage (from 0% - 0.0 to 100% - 1.0) when the wavelength is 0.555 microns and the spatial frequency is 89 lppm. The MTF (marker S1) and the meridional MTF (marker T1) change with respect to the half-view position (in millimeters). The MTF corresponding to each different half-view is as follows: Center MTF: 83%

50% half-view MTF: sagittal to MTF=80%, meridional to MTF=77%

90% half-view MTF: sagittal to MTF=71%, meridional to MTF=69%

The relative difference between the sagittal direction and the meridional MTF in the range of 50% half angle of view is less than 4%, and the relative difference between the sagittal direction and the meridional MTF in the 90% half angle of view is less than 8%.

In the illustrated embodiment, the full half angle of view corresponds to an image height of 2.856 mm.

Second embodiment: EFL=3.314 mm (C=302) of the optical module

Figure 4 is a schematic illustration of an optical module 410 in accordance with the present invention.

The optical module 410 has an object side 412 and an image side 414. The object side 412 to the image side 414 includes a first lens 416 having a positive refractive power having a focal length F1 and including a first optical surface 418 and a second surface. Optical surface 420, first optical surface 418 is convex and faces object side 412.

The optical module 410 further includes a second lens 422 having a negative refractive power having a focal length F2 and including a third optical surface 424 and a fourth optical surface 426, the third optical surface 424 facing the object side 412.

The optical module 410 further includes a third lens 427 having a positive refractive power having a focal length F3 and including a fifth optical surface 428 and a sixth optical surface 429. The fifth optical surface 428 faces the object side 412 and is concave. The sixth optical surface 429 faces the image side 414 and is convex.

The optical module 410 further includes a fourth lens 430 having a negative refractive power having a focal length F4 and including a seventh optical surface 431 and an eighth optical surface 432, the seventh optical surface 431 facing the object side 412.

The optical module 410 includes a diaphragm or aperture 433 that is in contact with the first optical surface 418.

The optical module 410 can include an infrared filter like the optical module 210, or can be used with the image sensor like the optical module 210.

The optical module 410 is applicable to an image sensor 450 of about five million pixels (arranged in a rectangular array), and the ratio of the long side to the short side is close to 4/3, and the area of each pixel is approximately equal to 1.4 micron. Multiply by 1.4 microns.

The aperture value F# of the optical module 410 is equal to 2.4.

Its full viewing angle is equal to 67.4 degrees.

The material used in the lens has the following characteristics:

This optical module has the following characteristics:

This optical module completely satisfies the condition (1), the condition (2), the condition (3), the condition (5), the condition (6), and the condition (7).

Figure 5 is a schematic diagram of the half angle of view of the optical module 410 relative to the MTF. The graph shows the arc labeled as a percentage (from 0% - 0.0 to 100% - 1.0) when the wavelength is 0.555 microns and the spatial frequency is 89 lppm. The MTF (marker S1) and the meridional MTF (marker T1) change with respect to the half-view position (in millimeters). The MTF corresponding to each different half-view is as follows: Center MTF: 81.8%

50% half-view MTF: sagittal to MTF=80%, meridional to MTF=78%

90% half-view MTF: sagittal to MTF=77%, meridional to MTF=70%

The relative difference between the sagittal direction and the meridional MTF in the range of 50% half angle of view is less than 4%, and the relative difference between the sagittal direction and the meridional MTF in the 90% half angle of view is less than 8%.

The full half angle of view is equivalent to an image height of 2.27 mm.

Although the present invention has been described above in terms of the preferred embodiments, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

10‧‧‧Optical module

12‧‧‧ object side

14‧‧‧ image side

16‧‧‧First lens

18‧‧‧First optical surface

20‧‧‧Second optical surface

22‧‧‧second lens

24‧‧‧ Third optical surface

26‧‧‧ Fourth optical surface

27‧‧‧ third lens

28‧‧‧ Fifth optical surface

29‧‧‧ Sixth optical surface

30‧‧‧Fourth lens

31‧‧‧ seventh optical surface

32‧‧‧ Eighth optical surface

33‧‧‧ aperture

210‧‧‧Optical module

212‧‧‧ ‧ side

214‧‧‧ image side

216‧‧‧ first lens

218‧‧‧First optical surface

220‧‧‧Second optical surface

222‧‧‧second lens

224‧‧‧ Third optical surface

226‧‧‧ Fourth optical surface

227‧‧‧ third lens

228‧‧‧ fifth optical surface

229‧‧‧ sixth optical surface

230‧‧‧Fourth lens

231‧‧‧ seventh optical surface

232‧‧‧ eighth optical surface

233‧‧‧ ray or aperture

240‧‧‧Infrared filter

250‧‧‧Image Sensor

410‧‧‧Optical module

412‧‧‧ ‧ side

414‧‧‧ image side

416‧‧‧ first lens

418‧‧‧First optical surface

420‧‧‧Second optical surface

422‧‧‧second lens

424‧‧‧ Third optical surface

426‧‧‧Fourth optical surface

427‧‧‧ third lens

428‧‧‧ fifth optical surface

429‧‧‧ sixth optical surface

430‧‧‧4th lens

431‧‧‧ seventh optical surface

432‧‧‧ eighth optical surface

433‧‧‧ ray or aperture

450‧‧‧Image sensor

1 is a schematic view of a four-lens optical module in accordance with an embodiment of the present invention.

2 is a schematic view of an optical module according to another embodiment of the present invention.

Figure 3 is a diagram of the modulation transfer function of the optical module of Figure 2 at a spatial frequency equal to 89 lppm.

Figure 4 is a schematic diagram of an optical module in accordance with another embodiment of the present invention.

Figure 5 is a diagram of the modulation transfer function of the optical module of Figure 4 at a spatial frequency equal to 89 lppm.

10‧‧‧Optical module

12‧‧‧ object side

14‧‧‧ image side

16‧‧‧First lens

18‧‧‧First optical surface

20‧‧‧Second optical surface

22‧‧‧second lens

24‧‧‧ Third optical surface

26‧‧‧ Fourth optical surface

27‧‧‧ third lens

28‧‧‧ Fifth optical surface

29‧‧‧ Sixth optical surface

30‧‧‧Fourth lens

31‧‧‧ seventh optical surface

32‧‧‧ Eighth optical surface

33‧‧‧ aperture

Claims (18)

An optical module having an object side and an image side, the optical module from the object side to the image side comprising: a first lens, a positive refractive power concave-convex lens, comprising a first optical surface and a a second optical surface having a convex surface facing the object side; a second lens being a concave lens having a negative refractive power, comprising a third optical surface and a fourth optical surface, the third optical surface Facing the object side; a third lens is a positive refractive power concave-convex lens comprising a fifth optical surface and a sixth optical surface, the fifth optical surface being concave and facing the object side, the sixth optical surface a convex surface facing the image side; a fourth lens being a lens having a negative refractive power, comprising a seventh optical surface and an eighth optical surface, the seventh optical surface facing the object side; wherein, |C1/C2 | 2, C1/Vd1 5.2, 1.1 C1/C 1.35, C1 is that the convergence of the first lens is equal to the reciprocal of the effective focal length of the first lens, the unit of convergence of the first lens is 1/m, and C2 is that the convergence of the second lens is equal to the effective focal length of the second lens. Reciprocal, the unit of convergence of the second lens is 1/m, Vd1 is the Abbe coefficient of the first lens, and C is the reciprocal of the convergence of the optical module equal to the effective focal length of the optical module, the optical module The unit of convergence is 1/m. The optical module of claim 1, wherein C1 is that the convergence of the first lens is equal to the reciprocal of the effective focal length of the first lens, the unit of convergence of the first lens is 1/m, and C3 is that the convergence of the third lens is equal to the reciprocal of the effective focal length of the third lens. The unit of convergence of the third lens is 1/m. The optical module of claim 1, wherein C2 is that the convergence of the second lens is equal to the reciprocal of the effective focal length of the second lens, the unit of convergence of the second lens is 1/m, and Vd2 is the Abbe coefficient of the second lens. The optical module of claim 1, wherein Ci is the reciprocal of the ith lens equal to the effective focal length of the ith lens, the unit of convergence of the ith lens is 1/m, and Vdi is the Abbe coefficient of the ith lens, i=1, 2, 3, 4 . The optical module of claim 1, wherein the optical module central modulation transfer function (MTF) value is greater than or equal to 75% when the wavelength is 0.555 micrometers and the spatial frequency is 89 lppm. The optical module of claim 1, wherein the half angle of view is 50%, the wavelength is 0.555 micrometers, and the spatial frequency is 89 lppm. The difference between the sagittal direction and the meridional modulation transfer function (MTF) of the optical module is less than 8%; when the half angle of view is 90%, the wavelength is 0.555 micrometers, and the spatial frequency is 89 lppm, the sagittal direction of the optical module The difference from the meridian modulation transfer function (MTF) is less than 15%. The optical module of claim 1, wherein the optical module has a sagittal MTF value greater than or equal to 70% when the half angle of view is 50%, the wavelength is 0.555 micrometers, and the spatial frequency is 89 lppm, and the meridional direction is The MTF value is greater than or equal to 65%. The optical module of claim 1, wherein when the half angle of view is 90%, the wavelength is 0.555 micrometers, and the spatial frequency is 89 lppm, the sagittal MTF value of the optical module is greater than or equal to 58%, and the meridional direction The MTF value is greater than or equal to 51%. The optical module of claim 1, further comprising an aperture disposed between the first lens and the second lens or between the object side and the first lens. The optical module of claim 1, wherein the first lens is made of glass, and the second, third, and fourth lenses are made of plastic. The optical module of claim 1, wherein the first and second lenses are made of glass, and the third and fourth lenses are made of plastic. The optical module of claim 1, wherein The first and third lenses are made of glass, and the second and fourth lenses are made of plastic. The optical module of claim 1, wherein the optical module has an effective focal length (EFL) of less than 4.4 mm when the wavelength is 0.555 micrometers. The optical module of claim 13, wherein the optical module has an effective focal length (EFL) of less than 3.6 mm when the wavelength is 0.555 micrometers. The optical module of claim 1, further comprising an infrared filter and/or an image sensor disposed between the fourth lens and the image side. The optical module of claim 1, wherein the optical module has a viewing angle (FOV) of between 63 degrees and 75 degrees. The optical module of claim 1, further comprising an image sensor disposed between the fourth lens and the image side, comprising five million pixels, each pixel area being smaller than Or equal to 1.4 microns by 1.4 microns, arranged in a rectangular array, the ratio of the long side to the short side of the rectangular array is about 4/3. The optical module of claim 17, wherein the image sensor comprises 7.9 million pixels, each pixel area being less than or equal to 1.4 micrometers and 1.4 micrometers, arranged in a rectangular array. The ratio of the long side to the short side of the rectangular array is about 4/3.