Fixed-focus spectrum lens

Abstract

The invention provides a fixed-focus spectrum lens. The fixed-focus spectrum lens sequentially comprises a prism, a color wheel and a lens group from an object side to an image side along an optical axis, the lens group sequentially comprises a first lens, a second lens, a third lens and a fourth lens from an object side to an image side along an optical axis. The color wheel and the first to fourth lenses are arranged on the light emitting side of the prism, and the optical axis is turned on the reflecting surface of the prism. The fixed focus spectrum lens has four lenses with diopters, and the diopters of the first to fourth lenses are respectively positive, negative, positive and negative.

Description

Technical Field

[0001] The invention relates to an optical device, in particular to a fixed-focus spectrum lens. Background Art

[0002] A spectral lens is an advanced optical device that can capture optical information in multiple independent bands. It provides deeper and more detailed optical information by distinguishing different bands. For example, the ultraviolet band can be used for counterfeit banknote identification, anti-counterfeiting labels, cultural relic protection and defect detection; the visible light band can be used for daily photography, product appearance inspection and automated visual systems; the near-infrared light band can be used for biomedicine, agriculture and food testing and monitoring. However, the wavelength range covered by the spectral lens of the existing technology is not large enough, and refocusing is required for different bands, which makes the operation complex. Summary of the invention

[0003] The present invention provides a fixed-focus spectrum lens, which can image various different wave bands without the need for refocusing for different wave bands.

[0004] According to one embodiment of the present invention, a fixed-focus spectral lens is provided, which includes a prism, a color wheel, and a lens group in order from the object side to the image side along the optical axis. The lens group includes a first lens, a second lens, a third lens, and a fourth lens in order from the object side to the image side along the optical axis. The color wheel and the first to fourth lenses are arranged on the light-emitting side of the prism, and the optical axis turns on the reflection surface of the prism. The fixed-focus spectral lens has a total of four lenses with refractive power, and the refractive powers of the first to fourth lenses are positive, negative, positive, and negative, respectively.

[0005] Based on the above, the fixed-focus spectral lens provided in the embodiment of the present invention uses a color wheel to image various different bands, and provides accurate optical information for different applications corresponding to different bands. For different bands, the fixed-focus spectral lens does not need to be refocused.

[0006] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1A A schematic diagram of a fixed-focus spectral lens according to a first embodiment of the present invention is shown;

[0008] Figure 1B and Figure 1C for Figure 1A Schematic diagram of field curvature of fixed-focus spectrum lens;

[0009] Figure 1D for Figure 1A Schematic diagram of the distortion of a fixed-focus spectrum lens;

[0010] Figure 2AA schematic diagram of a fixed-focus spectral lens according to a second embodiment of the present invention is shown;

[0011] Figure 2B and Figure 2C for Figure 2A Schematic diagram of field curvature of fixed-focus spectrum lens;

[0012] Figure 2D for Figure 2A Schematic diagram of the distortion of a fixed-focus spectrum lens;

[0013] Figure 3 A schematic diagram showing a color wheel according to some embodiments of the present invention.

[0014] Description of Figure Numbers:

[0015] 0: Aperture

[0016] 1, 2, 3, 4: Lens

[0017] 5: Prism

[0018] 6: Color Wheel

[0019] 10: Fixed-focus spectrum lens

[0020] 15, 25, 35, 45, 65, 75: side view

[0021] 16, 26, 36, 46, 66, 76: like side view

[0022] 55: Light-entering surface

[0023] 56: Bright side

[0024] 57: Reflective surface

[0025] 61: Upper cover

[0026] 61H: Opening

[0027] 62:Ontology

[0028] 99: Imaging surface

[0029] 621: filter layer

[0030] 622: filter layer

[0031] 623: Filter layer

[0032] 624: Filter layer

[0033] 625: filter layer

[0034] 626: filter layer

[0035] 627: Filter layer

[0036] 628: Filter layer

[0037] A1, A2, A3: Direction

[0038] I: optical axis DETAILED DESCRIPTION

[0039] Reference Figure 1A as well as Figure 3 ,in Figure 1A FIG. 1 is a schematic diagram showing a fixed-focus spectral lens according to a first embodiment of the present invention, Figure 3 A schematic diagram showing a color wheel according to some embodiments of the present invention.

[0040] The fixed-focus spectral lens 10 includes a prism 5, a color wheel 6, a lens 1, a lens 2, a lens 3, and a lens 4 in order from the object side to the image side along the optical axis I, wherein the lens 1, the lens 2, the lens 3, and the lens 4 constitute a lens group. The lens 1, the lens 2, the lens 3, and the lens 4 may include plastic or glass. The aperture O of the lens group is located between the color wheel 6 and the lens 1. The object side described above is in the positive direction of the direction A1 relative to the fixed-focus spectral lens 10, and the image side is in the positive direction of the direction A2 relative to the fixed-focus spectral lens 10.

[0041] The prism 5 includes a light incident surface 55, a light emitting surface 56, and a reflective surface 57. The optical axis I turns on the reflective surface 57 of the prism 5. Light can enter the prism 5 from the light incident surface 55 of the prism 5, be reflected by the reflective surface 57, and leave the prism 5 from the light emitting surface 56. The color wheel 6, lens 1, lens 2, lens 3, and lens 4 are arranged on the light emitting side of the prism 5.

[0042] The color wheel 6 of the first embodiment can Figure 3 The color wheel 6 includes an upper cover 61 and a body 62. The upper cover 61 has an opening 61H for allowing light to pass through. The body 62 includes a filter layer 621, a filter layer 622, a filter layer 623, a filter layer 624, a filter layer 625, a filter layer 626, a filter layer 627, and a filter layer 628, wherein the wavelength bands corresponding to these filter layers may not overlap with each other at all, or may overlap partially. The upper cover 61 is used to limit the light passing through the opening 61H to only pass through one of the filter layers 621, the filter layer 622, the filter layer 623, the filter layer 624, the filter layer 625, the filter layer 626, the filter layer 627, and the filter layer 628, and not pass through multiple filter layers at the same time.

[0043] The body 62 can be rotated with its geometric center as the center point of rotation, so as to set any filter layer at a position corresponding to the opening 61H according to needs, so as to allow light with appropriate wavelength to pass through the selected filter layer and filter out the wavelength band that needs to be filtered out.

[0044] The upper cover 61 and the body 62 each have an object side surface 65, 75 for the imaging light to pass through and an image side surface 66, 76 for the imaging light to pass through. The lens 1, the lens 2, the lens 3, and the lens 4 each have an object side surface 15, 25, 35, 45 for the imaging light to pass through and an image side surface 16, 26, 36, 46 for the imaging light to pass through. When a light is emitted from an object to be photographed, the light enters the prism 5 from the light incident surface 55 of the prism 5, is reflected on the reflection surface 57 of the prism 5, and then is emitted from the light exit surface 56 of the prism 5, and then passes through the color wheel 6, the lens 1, the lens 2, the lens 3, and the lens 4 in sequence, and forms an image on the imaging surface 99.

[0045] In some embodiments, the filter layers 621, 622, 623, 624, 625, 626, 627, and 628 of the body 62 may cover the entire visible light band, so the fixed-focus spectrum lens 10 may image the entire visible light band. However, this is not a limitation, in some embodiments, the filter layers of the body 62 may only correspond to some specific narrow bands, so that the fixed-focus spectrum lens 10 can provide more accurate optical information for applications corresponding to the narrow bands.

[0046] The lens 1 has positive refractive power, the optical axis region of the object side surface 15 is convex, the optical axis region of the image side surface 26 is convex, and both the object side surface 15 and the image side surface 16 are spherical surfaces.

[0047] The lens 2 has negative refractive power, the optical axis region of the object side surface 25 is a concave surface, the optical axis region of the image side surface 26 is a concave surface, and both the object side surface 25 and the image side surface 26 are spherical surfaces.

[0048] The lens 3 has positive refractive power, the optical axis region of the object side surface 35 is convex, the optical axis region of the image side surface 36 is convex, and both the object side surface 35 and the image side surface 36 are aspherical surfaces.

[0049] The lens 4 has negative refractive power, and the optical axis region of the object side surface 45 is a concave surface, the optical axis region of the image side surface 46 is a concave surface, and both the object side surface 45 and the image side surface 46 are spherical surfaces.

[0050] Other detailed optical data of the first embodiment are shown in Table 1. The half field angle of the fixed-focus spectrum lens 10 is 15°, and the effective focal length (EFL) is 7.585 mm.

[0051] Table 1:

[0052]

[0053] In Table 1, the curvature radius of lens 1, lens 2, lens 3, and lens 4 refers to the curvature radius of each lens in the optical axis area. The spacing of the light-entering surfaces 55 of the prism 5 (as indicated in Table 1 as 5.500 mm) is the total length of the optical axis I inside the prism 5 in the direction A1 and in the direction A2. The spacing of the light-emitting surfaces 56 (as indicated in Table 1 as 0.500 mm) is the distance between the light-emitting surfaces 56 of the prism 5 and the object side surface 65 of the upper cover 61 on the optical axis I, that is, the gap between the prism 5 and the upper cover 61 on the optical axis I. The spacing of the object side surface 65 (as indicated in Table 1 as 0.500 mm) is the thickness of the upper cover 61 on the optical axis I, and so on. The spacing of the aperture 0 (as indicated in Table 1 as 0.100 mm) is the distance between the aperture 0 and the object side surface 15 of the lens 1 on the optical axis I, that is, the gap between the aperture 0 and the lens 1 on the optical axis I. The spacing of the object side surface 15 (1.547 mm as shown in Table 1) is the thickness of the lens 1 on the optical axis I. The spacing of the image side surface 16 (0.100 mm as shown in Table 1) is the distance between the image side surface 16 and the object side surface 25 on the optical axis I, that is, the gap between the lens 1 and the lens 2 on the optical axis I, and so on.

[0054] In this embodiment, the object-side surface 35 and the image-side surface 36 of the lens 3 are both aspherical surfaces, and these aspherical surfaces are defined according to the following formula (1):

[0055] (1)

[0056] Y: the distance between the point on the aspheric curve and the optical axis;

[0057] Z: Aspheric depth, that is, the vertical distance between the point on the aspheric surface that is Y away from the optical axis and the tangent plane tangent to the vertex on the aspheric optical axis;

[0058] R: radius of curvature of the lens surface;

[0059] K: cone coefficient;

[0060] a 2i : 2i-th order aspheric coefficient.

[0061] The cone coefficient K and various aspheric coefficients in the aspheric formula (1) of this embodiment are shown in Table 2. In Table 2, number 35 represents the object side surface 35 of the lens 3, and number 36 represents the image side surface 36 of the lens 3.

[0062] Table 2:

[0063]

[0064] It should be noted that the fixed-focus spectral lens provided according to the embodiment of the present invention is not limited to the values ​​shown in Table 1 and Table 2. In some embodiments, Figure 1AThe ratio of the distance between lens 2 and lens 3 on the optical axis I to the effective focal length of the fixed-focus spectral lens 10 may be greater than or equal to 0.25 and less than or equal to 0.35. In some embodiments, Figure 1A The ratio of the distance between lens 2 and lens 3 on the optical axis I to the effective focal length of fixed-focus spectral lens 10 may be greater than or equal to 0.29 and less than or equal to 0.33. In some embodiments, Figure 1A The gap between the aperture 0 and the lens 1 on the optical axis I can be greater than or equal to 0.1 mm.

[0065] Also refer to Figures 1B to 1D , Figure 1B : shows a graph of field curvature aberration in the tangential direction when light rays with wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, 750 nm, 850 nm and 950 nm are incident on the fixed-focus spectrum lens 10 of the first embodiment. Figure 1C : shows a curve diagram of field curvature aberration in the sagittal direction when light rays with wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, 750 nm, 850 nm and 950 nm are incident on the fixed-focus spectrum lens 10 of the first embodiment, Figure 1D The graph shows the distortion when light rays with wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, 750 nm, 850 nm and 950 nm are incident on the fixed-focus spectrum lens 10 of the first embodiment. It should be noted that the above 7 representative wavelengths correspond to different colors of light in the entire visible light band and the near-infrared band.

[0066] like Figure 1B as well as Figure 1C As shown in the field curvature aberration curve, the field curvature aberration of the seven representative wavelengths in the entire field of view falls within ±0.05 mm, indicating that the fixed-focus spectrum lens 10 of the first embodiment can effectively eliminate the field curvature aberration. Figure 1D As shown in the distortion curve diagram, the distortion aberration of the seven representative wavelengths in the entire field of view is less than ±1.6564%; and when the spatial frequency is 125 lp / mm, the modulation transfer function (MTF) of the fixed-focus spectral lens 10 still has a performance greater than 0.4, indicating that the fixed-focus spectral lens 10 of the first embodiment has good imaging quality in the entire visible light band and near-infrared band.

[0067] Reference Figure 2A as well as Figure 3 ,in Figure 2AFIG. 1 is a schematic diagram showing a fixed-focus spectral lens according to a second embodiment of the present invention, Figure 3 A schematic diagram showing a color wheel according to some embodiments of the present invention.

[0068] The fixed-focus spectral lens 10 includes a prism 5, a color wheel 6, a lens 1, a lens 2, a lens 3, and a lens 4 in order from the object side to the image side along the optical axis I, wherein the lens 1, the lens 2, the lens 3, and the lens 4 constitute a lens group. The lens 1, the lens 2, the lens 3, and the lens 4 may include plastic or glass. The aperture O of the lens group is located between the color wheel 6 and the lens 1. The object side described above is in the positive direction of the direction A1 relative to the fixed-focus spectral lens 10, and the image side is in the positive direction of the direction A2 relative to the fixed-focus spectral lens 10.

[0069] The prism 5 includes a light incident surface 55, a light emitting surface 56, and a reflective surface 57. The optical axis I turns on the reflective surface 57 of the prism 5. Light can enter the prism 5 from the light incident surface 55 of the prism 5, be reflected by the reflective surface 57, and leave the prism 5 from the light emitting surface 56. The color wheel 6, lens 1, lens 2, lens 3, and lens 4 are arranged on the light emitting side of the prism 5.

[0070] The color wheel 6 of the second embodiment can Figure 3 The color wheel 6 includes an upper cover 61 and a body 62. The upper cover 61 has an opening 61H for allowing light to pass through. The body 62 includes a filter layer 621, a filter layer 622, a filter layer 623, a filter layer 624, a filter layer 625, a filter layer 626, a filter layer 627, and a filter layer 628, wherein the wavelength bands corresponding to these filter layers may not overlap with each other at all, or may overlap partially. The upper cover 61 is used to limit the light passing through the opening 61H to only pass through one of the filter layers 621, the filter layer 622, the filter layer 623, the filter layer 624, the filter layer 625, the filter layer 626, the filter layer 627, and the filter layer 628, and not pass through multiple filter layers at the same time.

[0071] The body 62 can be rotated with its geometric center as the center point of rotation, so as to set any filter layer at a position corresponding to the opening 61H according to needs, so as to allow light with appropriate wavelength to pass through the selected filter layer and filter out the wavelength band that needs to be filtered out.

[0072] The upper cover 61 and the body 62 each have an object side surface 65, 75 for the imaging light to pass through and an image side surface 66, 76 for the imaging light to pass through. The lens 1, the lens 2, the lens 3, and the lens 4 each have an object side surface 15, 25, 35, 45 for the imaging light to pass through and an image side surface 16, 26, 36, 46 for the imaging light to pass through. When a light is emitted from an object to be photographed, the light enters the prism 5 from the light incident surface 55 of the prism 5, is reflected on the reflection surface 57 of the prism 5, and then is emitted from the light exit surface 56 of the prism 5, and then passes through the color wheel 6, the lens 1, the lens 2, the lens 3, and the lens 4 in sequence, and forms an image on the imaging surface 99.

[0073] In some embodiments, the filter layers 621, 622, 623, 624, 625, 626, 627, and 628 of the body 62 may cover the entire visible light band, so the fixed-focus spectrum lens 10 may image the entire visible light band. However, this is not a limitation, in some embodiments, the filter layers of the body 62 may only correspond to some specific narrow bands, so that the fixed-focus spectrum lens 10 can provide more accurate optical information for applications corresponding to the narrow bands.

[0074] The lens 1 has positive refractive power, the optical axis region of the object side surface 15 is convex, the optical axis region of the image side surface 26 is convex, and both the object side surface 15 and the image side surface 16 are spherical surfaces.

[0075] The lens 2 has negative refractive power, the optical axis region of the object side surface 25 is a concave surface, the optical axis region of the image side surface 26 is a concave surface, and both the object side surface 25 and the image side surface 26 are spherical surfaces.

[0076] The lens 3 has positive refractive power, the optical axis region of the object side surface 35 is convex, the optical axis region of the image side surface 36 is convex, and both the object side surface 35 and the image side surface 36 are aspherical surfaces.

[0077] The lens 4 has a negative refractive power and is a negative meniscus lens with a concave surface facing the image side. The optical axis region of the object side surface 45 is convex, and the optical axis region of the image side surface 46 is concave. Both the object side surface 45 and the image side surface 46 are spherical.

[0078] Other detailed optical data of the second embodiment are shown in Table 3. The half field angle of the fixed-focus spectrum lens 10 is 15.1°, and the effective focal length (EFL) is 11.332 mm.

[0079] Table 3:

[0080]

[0081] In Table 3, the curvature radius of lens 1, lens 2, lens 3, and lens 4 refers to the curvature radius of each lens in the optical axis area. The spacing of the light-entering surfaces 55 of the prism 5 (as indicated in Table 3 as 7.500 mm) is the total length of the optical axis I inside the prism 5 in the direction A1 and in the direction A2. The spacing of the light-emitting surfaces 56 (as indicated in Table 3 as 0.500 mm) is the distance between the light-emitting surfaces 56 of the prism 5 and the object side surface 65 of the upper cover 61 on the optical axis I, that is, the gap between the prism 5 and the upper cover 61 on the optical axis I. The spacing of the object side surface 65 (as indicated in Table 3 as 0.500 mm) is the thickness of the upper cover 61 on the optical axis I, and so on. The spacing of the aperture 0 (as indicated in Table 3 as 0.100 mm) is the distance between the aperture 0 and the object side surface 15 of the lens 1 on the optical axis I, that is, the gap between the aperture 0 and the lens 1 on the optical axis I. The spacing of the object side surface 15 (1.977 mm as shown in Table 3) is the thickness of the lens 1 on the optical axis I. The spacing of the image side surface 16 (0.372 mm as shown in Table 3) is the distance between the image side surface 16 and the object side surface 25 on the optical axis I, that is, the gap between the lens 1 and the lens 2 on the optical axis I, and so on.

[0082] In this embodiment, the object-side surface 35 and the image-side surface 36 of the lens 3 are both aspherical surfaces, and these aspherical surfaces are defined according to the above formula (1).

[0083] The cone coefficient K and various aspheric coefficients in the aspheric formula (1) of this embodiment are shown in Table 4. In Table 4, number 35 represents the object side surface 35 of the lens 3, and number 36 represents the image side surface 36 of the lens 3.

[0084] Table 4:

[0085]

[0086] It should be noted that the fixed-focus spectral lens provided according to the embodiment of the present invention is not limited to the values ​​shown in Table 3 and Table 4. In some embodiments, Figure 2A The ratio of the distance between lens 2 and lens 3 on the optical axis I to the effective focal length of the fixed-focus spectral lens 10 may be greater than or equal to 0.25 and less than or equal to 0.35. In some embodiments, Figure 2A The ratio of the distance between lens 2 and lens 3 on the optical axis I to the effective focal length of the fixed-focus spectral lens 10 may be greater than or equal to 0.25 and less than or equal to 0.27. In some embodiments, Figure 2A The gap between the aperture 0 and the lens 1 on the optical axis I can be greater than or equal to 0.1 mm.

[0087] Also refer to FIG. 2B to FIG. 2D , Figure 2B: shows a graph of field curvature aberration in the tangential direction when light rays with wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, 750 nm, 850 nm and 950 nm are incident on the fixed-focus spectrum lens 10 of the second embodiment, Figure 2C : shows a curve diagram of field curvature aberration in the sagittal direction when light rays with wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, 750 nm, 850 nm and 950 nm are incident on the fixed-focus spectrum lens 10 of the second embodiment, Figure 2D The graph shows the distortion when light rays with wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, 750 nm, 850 nm and 950 nm are incident on the fixed-focus spectrum lens 10 of the second embodiment. It should be noted that the above 7 representative wavelengths correspond to different colors of light in the entire visible light band and the near-infrared band, respectively.

[0088] like Figure 2B as well as Figure 2C As shown in the field curvature aberration curve, the field curvature aberration of the seven representative wavelengths in the entire field of view falls within ±0.20 mm, indicating that the fixed-focus spectrum lens 10 of the second embodiment can effectively eliminate the field curvature aberration. Figure 2D As shown in the distortion curve diagram, the distortion aberration of the seven representative wavelengths in the entire field of view is less than ±1.5004%; and when the spatial frequency is 125 lp / mm, the modulation transfer function (MTF) of the fixed-focus spectral lens 10 still has a performance greater than 0.2, indicating that the fixed-focus spectral lens 10 of the second embodiment has good imaging quality in the entire visible light band and near-infrared band.

[0089] Based on the above, the fixed-focus spectral lens provided by the embodiment of the present invention has good imaging quality in the entire visible light band and the near-infrared band. The fixed-focus spectral lens can provide accurate optical information for different applications corresponding to different bands. For different bands, the fixed-focus spectral lens does not need to be refocused. In addition, the band can be easily switched using a rotatable color wheel.

Claims

1. A fixed-focus spectral lens, characterized in that: The fixed-focus spectral lens includes a prism, a color wheel, and a lens group in sequence along the optical axis from the object side to the image side. The lens group includes a first lens, a second lens, a third lens and a fourth lens in sequence from the object side to the image side along the optical axis. The color wheel and the first to fourth lenses are arranged on the light-emitting side of the prism, and the optical axis turns on the reflection surface of the prism. The fixed-focus spectrum lens has four lenses with refractive power, and the refractive powers of the first lens to the fourth lens are positive, negative, positive, and negative respectively.

2. The fixed-focus spectral lens according to claim 1, characterized in that: A ratio of a distance between the second lens and the third lens on the optical axis to an effective focal length of the fixed-focus spectrum lens is greater than or equal to 0.25 and less than or equal to 0.

35.

3. The fixed-focus spectral lens according to claim 1, characterized in that: At least one of the first lens, the second lens, and the fourth lens is a spherical lens.

4. The fixed-focus spectral lens according to claim 1, characterized in that: The third lens is an aspherical lens.

5. The fixed-focus spectral lens according to claim 1, characterized in that: The first lens is a biconvex lens.

6. The fixed-focus spectral lens according to claim 1, characterized in that: The second lens is a biconcave lens.

7. The fixed-focus spectral lens according to claim 1, characterized in that: The third lens is a biconvex lens.

8. The fixed-focus spectral lens according to claim 1, characterized in that: The fourth lens is a biconcave lens.

9. The fixed-focus spectrum lens according to claim 1, characterized in that: The fourth lens is a negative meniscus lens with a concave surface facing the image side.

10. The fixed-focus spectral lens according to claim 1, characterized in that: The first lens, the second lens, and the fourth lens are spherical lenses.

11. The fixed-focus spectral lens according to claim 1, characterized in that: A ratio of a distance between the second lens and the third lens on the optical axis to an effective focal length of the fixed-focus spectrum lens is greater than or equal to 0.25 and less than or equal to 0.

27.

12. The fixed-focus spectral lens according to claim 1, characterized in that: A ratio of a distance between the second lens and the third lens on the optical axis to an effective focal length of the fixed-focus spectral lens is greater than or equal to 0.29 and less than or equal to 0.

33.

13. The fixed-focus spectral lens according to claim 1, characterized in that: The aperture of the lens group is located between the color wheel and the first lens, and the gap between the aperture and the first lens on the optical axis is greater than or equal to 0.1 mm.

Images