Compound lens

Abstract

A compound lens includes four coaxially aligned lenses: (i) a first lens, and in order of increasing distance from the first lens and on the same side thereof (ii) a second lens, an inter-lens substrate, a third lens, and a fourth lens. The first and third lenses are negative lenses. The second and fourth lenses are positive lenses.

Description

Background Technology

[0001] Medical endoscopy, machine vision, eye / face tracking, and other applications require compact cameras that can capture high-quality images with a wide field of view and can be manufactured using low-cost processes compatible with high-volume production. Summary of the Invention

[0002] The embodiments disclosed herein include lenses that enable such cameras. A compound lens includes four coaxially aligned lenses: (i) a first lens, and (ii) a second lens in increasing order of distance from the first lens and on the same side thereon, an inter-lens substrate, a third lens, and a fourth lens. The first and third lenses are negative lenses. The second and fourth lenses are positive lenses. Attached Figure Description

[0003] Figure 1 This is a cross-sectional view of a lesion-containing chamber imaged by an endoscopic camera, which includes a compound lens, in an embodiment.

[0004] Figure 2 This is a schematic cross-sectional view of a compound lens, which is Figure 1 Examples of compound lenses in [the text].

[0005] Figure 3 It is used for visible light imaging. Figure 2 A cross-sectional view of an embodiment of the compound lens.

[0006] Figure 4 It shows Figure 3 A table of exemplary parameters for the compound lens.

[0007] Figure 5 It is used for near-infrared imaging. Figure 2 A cross-sectional view of an embodiment of the compound lens.

[0008] Figure 6 It shows Figure 5 A table of exemplary parameters for the compound lens.

[0009] Figure 7 It is used for infrared imaging. Figure 2 A cross-sectional view of an embodiment of the compound lens.

[0010] Figure 8 It shows Figure 7 A table of exemplary parameters for the compound lens. Detailed Implementation

[0011] Figure 1This is a cross-sectional view of an endoscope 195 inside a chamber 190 that includes lesion 192. Lesion 192 is located on the sidewall 191 of the chamber. For example, chamber 190 may be part of the esophagus or intestine. Endoscope 195 includes a camera 180 for imaging lesion 192. Camera 180 includes a lens 182 that partially defines the field of view 188 of camera 180. Without departing from the scope of this document, camera 180 may be part of a device other than an endoscope, such as a security camera, mobile device, or other consumer electronics.

[0012] Figure 2 This is a cross-sectional view of a compound lens 200, an example of lens 182 of camera 180. The compound lens 200 includes a lens 210, and lenses 220, 260, 230, and 240 arranged in increasing order of distance from lens 210 and on the same side thereof. Lenses 210 and 230 are negative lenses. Lenses 220 and 240 are positive lenses. Lenses 210-240 are coaxial with a common optical axis 201. Lenses 210-240 have respective object-side surfaces 211, 221, 231, and 241, and respective image-side surfaces 212, 222, 232, and 242. At least one of surfaces 212, 221, 232, and 242 may be non-planar and aspherical. At the optical axis 201, at least one of surfaces 212 and 232 may be concave, and at least one of surfaces 221 and 242 may be convex.

[0013] The compound lens 200 may further include at least one of a substrate 250, a substrate 270, a spectral filter 280, and a cover glass 290. Substrates 250, 260, and 270 have respective object-side surfaces 251, 261, and 271, and respective image-side surfaces 252, 262, and 272. At least one of surfaces 211, 222, 231, 241, 251, 261, 262, 271, and 272 may be planar. The spectral filter 280 and the cover glass 290 have respective object-side surfaces 281 and 291. The aperture stop of the lens 200 may be located at surface 231 or 271.

[0014] In the embodiments, at least one of the following conditions is satisfied: lens 210 is on substrate 250, lens 220 is on substrate 260, lens 230 is on substrate 260, and lens 240 is on substrate 270. Regarding the surfaces, in the embodiments, at least one of the following conditions is satisfied: object-side surface 211 is on image-side surface 252, image-side surface 222 is on object-side surface 261, object-side surface 231 is on image-side surface 262, and object-side surface 241 is on image-side surface 272.

[0015] The compound lens 200 has an effective focal length f between the principal plane 284 and the image plane 299.eff And the total trajectory length T between the object-side surface 251 and the image plane 299. In an embodiment, the ratio T / f eff Satisfy 3 <T / f eff <13, which limits the lateral and longitudinal dimensions of the compound lens 200. In the embodiment, T / f eff The aforementioned lower and upper limits are satisfied at wavelengths between 420nm and 860nm.

[0016] Lenses 210, 220, 230, and 240 have their own focal lengths f1, f2, f3, and f4. In this embodiment, the ratio R1 = (f1 + f3)f eff / (f1f3) is greater than -2.5 and less than -0.3. The benefit of limiting the ratio R1 within this range is to balance the distortion of the compound lens 200. In an embodiment, the ratio R2 = (f2 + f4)f eff / (f2f4) is greater than 0.4 and less than 3. The benefit of limiting the ratio R2 within the above range is to balance aberrations and improve the modulation transfer function of the compound lens 200. In the embodiment, at wavelengths between 420 nm and 860 nm, the values ​​of ratios R1 and R2 are within their respective ranges.

[0017] Lenses 210 and 240 each have their own Abbe number V. 210 and V 240 Abbe number V 210 and V 240 λ was calculated at the blue, green, and red Fraunhofer F-, d-, and C- spectral lines, respectively. F =486.1nm, λ d =587.6nm, and λ c = 656.3nm. In the embodiment, V 210 ≥37 and V 240 ≥26, which leads to a reduction in color difference such as lateral color and axial color.

[0018] Figure 3 This is a cross-sectional view of a compound lens 300, which is an embodiment of a compound lens 200 used for imaging at visible light wavelengths. The compound lens 300 includes a substrate 360, lenses 310, 320, 330, and 340, and may further include at least one of a substrate 350, a substrate 370, an aperture stop 365, an IR cutoff filter 380, and a cover glass 390. Lenses 310-340 are coaxial with an optical axis 301. When the compound lens 300 includes a substrate 370, the aperture stop 365 is located on the object-side surface 371 and may be an opaque coating on surface 371.

[0019] Lenses 310-340 have their respective object-side surfaces 311, 321, 331 and 341, and their respective image-side surfaces 312, 322, 332 and 342. Substrates 350, 360, 370, IR cut-off filter 380 and cover glass 390 have their respective object-side surfaces 351, 361, 371, 381 and 391, and their respective image-side surfaces 352, 362, 372, 382 and 392.

[0020] In this document, figures are represented by reference numerals with specific tens and units digits. Figure 3 The elements in the following figures or diagrams have the same tens digit and units digit. Figure 2 Examples of components. For example, lens 310, surface 311 and surface 312 are examples of lens 210, surface 211 and surface 212, respectively.

[0021] Figure 4 Table 400 shows exemplary parameters of the surfaces and substrate of the compound lens 300. Table 400 includes columns 404, 406, 408, 410, 412, 414, and 421-427. Column 421 represents the surface of the compound lens 300 and also the aperture stop 365. Column 423 includes the thickness values ​​between adjacent surfaces of the compound lens 300 on the optical axis 301. For example, the axial distance between surfaces 311 and 312 is 0.030 mm, which is the axial thickness of the lens 310. Column 426 represents the minimum diameter of each surface, which is sufficient to allow light incident on surface 311 to pass through the aperture stop 365 and also through that surface.

[0022] The non-planar surface of Table 400 is characterized by the surface depression z shown in Equation 1. sag definition.

[0023]

[0024] In equation 1, z sag It is a function of the radial coordinate r, where the directions z and r are parallel to and perpendicular to the optical axis 301, respectively. The exponent i is a positive integer, and... Figure 4 In the example, N = 7. In Equation 1, the parameter R is the surface radius of curvature listed in column 422 of Table 400. The parameter k refers to the conic constant shown in column 427. Columns 404, 406, 408, 410, 412, and 414 contain the aspherical coefficients α4, α6, α8, α... 10 α 12 and α 14 The value of z in Table 400. The units of the quantities in Table 400 and the z in the equations. sag Consistent. Equation 1 is expressed in millimeters.

[0025] Columns 424 and 425 respectively list the wavelengths λ in free space. d The values ​​of the material's refractive index and Abbe number at 587.6 nm. The refractive index and Abbe number corresponding to a surface characterize the material between that surface and the surfaces in the next row. For example, the refractive index and Abbe number associated with surface 311 are 1.51 and 61.2, respectively, which are the refractive index and Abbe number of lens 310.

[0026] The compound lens 300 has f 300 =0.43mm (at λ0 = 570nm), effective focal length, 125 degrees field of view, and f-number equal to 4. The total trajectory length of the compound lens 300 between surface 311 and image plane 399 is T. 300 = 2.08mm. The ratio of total trajectory length to effective focal length is T. 300 / f 300 =1.65.

[0027] Lenses 310-340 each have focal lengths f1, f2, f3, and f4, each of which can be approximated by the lens manufacturer's equation using the values ​​of radius of curvature, axial thickness, and refractive index from Table 4. The calculated focal lengths are f1 = -0.38 mm, f2 = 0.69 mm, f3 = -1.86 mm, and f4 = 0.48 mm, such that R1 = -1.55 and R2 = 1.74. The wavelength dependence of the refractive index and its relationship with λ... d The effective focal length between λ = 587.6 nm and λ0 = 570 nm is small enough that the above focal length values ​​and ratios are applicable to λ. d Both λ0 and λ0.

[0028] Figure 5 This is a cross-sectional view of a compound lens 500, an embodiment of compound lens 200, used for imaging at near-infrared wavelengths. The compound lens 500 includes a substrate 560, lenses 510, 520, 530, and 540, and may further include at least one of a substrate 550, a substrate 570, an aperture stop 565, and a cover glass 590. Lenses 510-540 are coaxial with an optical axis 501. The aperture stop 565 is located on the image-side surface 562 and may be an opaque coating on surface 562.

[0029] Lenses 510-540 have their respective object-side surfaces 511, 521, 531 and 541, and their respective image-side surfaces 512, 522, 532 and 542. Substrates 550, 560, 570 and cover glass 590 have their respective object-side surfaces 551, 561, 571 and 591, and their respective image-side surfaces 552, 562, 572 and 592.

[0030] Figure 6 Table 600 provides exemplary parameters of the surface and substrate of the compound lens 500. Table 600 includes columns 604, 606, 608, 610, 612, 614, 616, and 621-627, which follow the same conventions as those in Table 400 above. Column 621 represents the surface of the compound lens 500 and also represents the aperture stop 565. Columns 624 and 625 are similar to columns 424 and 425 of Table 400, and therefore include parameters for the free-space wavelength λ, respectively. d The refractive index and Abbe number of the material at 587.6 nm.

[0031] The compound lens 500 has f 300 =0.49mm (at λ0 = 850nm), effective focal length, 103 degrees field of view, and f-number equal to 1.95. The total trajectory length of the compound lens 500 between surface 511 and image plane 599 is T. 500 = 2.17mm. The ratio of total trajectory length to effective focal length is T. 500 / f 500 =4.43.

[0032] Lenses 510-540 each have focal lengths f1, f2, f3, and f4, each of which can be approximated by the lens manufacturer's equation using the values ​​of radius of curvature, axial thickness, and refractive index from Table 6. The calculated focal lengths are f1 = -0.58 mm, f2 = 0.55 mm, f3 = -2.20 mm, and f4 = 0.74 mm, such that R1 = -1.06 and R2 = 1.56. The wavelength dependence of the refractive index and its relationship with λ... d The effective focal length between λ = 587.6 nm and λ0 = 850 nm is small enough that the above focal length values ​​and ratios are applicable to λ. d Both λ0 and λ0.

[0033] Figure 7 This is a cross-sectional view of a compound lens 700, an embodiment of compound lens 200 used for imaging at near-infrared wavelengths. The compound lens 700 includes a substrate 760, lenses 710, 720, 730, and 740, and may further include at least one of a substrate 750, a substrate 770, an aperture stop 765, and a cover glass 790. Lenses 710-740 are coaxial with an optical axis 701. The aperture stop 765 is located at the image-side surface 762 and may be an opaque coating on surface 762.

[0034] Lenses 710-740 have respective object-side surfaces 711, 721, 731 and 741, and respective image-side surfaces 712, 722, 732 and 742. Substrates 750, 760, 770 and cover glass 790 have respective object-side surfaces 751, 761, 771 and 791, and respective image-side surfaces 752, 762, 772 and 792.

[0035] Figure 8 Table 800 provides exemplary parameters of the surface and substrate of the compound lens 700. Table 800 includes columns 804, 806, 808, 810, 812, 814, 816, and 821-827, which follow the same conventions as those in Table 400 above. Column 821 represents the surface of the compound lens 700 and also represents the aperture stop 765. Columns 824 and 825 are similar to columns 424 and 425 of Table 400; therefore, columns 824 and 825 respectively include parameters for the free-space wavelength λ. d The refractive index and Abbe number of the material at 587.6 nm.

[0036] The compound lens 700 has f 300 =0.27mm (at λ0 = 850nm), effective focal length, 103 degrees field of view, and f-number equal to 1.95. The total trajectory length of the compound lens 700 between surface 711 and image plane 799 is T. 700 = 2.21mm. The ratio of total trajectory length to effective focal length is T. 700 / f 700 =8.19.

[0037] Lenses 710-740 each have focal lengths f1, f2, f3, and f4, each of which can be approximated by the lens manufacturer's equation using the values ​​of radius of curvature, axial thickness, and refractive index from Table 8. The calculated focal lengths are f1 = -0.58 mm, f2 = 0.55 mm, f3 = -2.20 mm, and f4 = 0.74 mm, making R1 = -1.06 and R2 = 1.56. The wavelength dependence of the refractive index and its relationship with λ... d The effective focal length between λ = 587.6 nm and λ0 = 850 nm is small enough that the above focal length values ​​and ratios are applicable to λ. d Both λ0 and λ0.

[0038] Feature combination

[0039] The features described above and those in the following claims can be combined in various ways without departing from the scope of the invention. The following examples illustrate some possible, non-limiting combinations:

[0040] (A1) A compound lens comprising four coaxially aligned lenses: (i) a first lens, and (ii) a second lens, an inter-lens substrate, a third lens, and a fourth lens arranged in order of increasing distance from the first lens and on the same side thereof. The first and third lenses are negative lenses. The second and fourth lenses are positive lenses.

[0041] (A2) In the embodiment of (A1), the second lens has a planar image-side surface on the planar object-side surface of the inter-lens substrate. The third lens has a planar object-side surface on the planar image-side surface of the inter-lens substrate.

[0042] (A3) In embodiments (A1) or (A2), an image-side substrate is also included; the fourth lens has a planar object-side surface on the planar image-side surface of the image-side substrate.

[0043] (A4) In any of the embodiments (A1)-(A3), an object-side substrate is further included; the first lens has a planar object-side surface on the planar image-side surface of the object-side substrate.

[0044] (A5) In any of embodiments (A1)-(A4), the first lens, the second lens, the third lens, and the fourth lens together have an effective focal length f. eff This allows the image to be formed at an image plane located at a distance T from the object-side surface of the object-side substrate, and the ratio T / f eff Satisfy 3 <T / f eff <13.

[0045] (A6) In any of the embodiments (A1)-(A5), the Abbe number of the first lens is at least 37 and the Abbe number of the fourth lens is at least 26.

[0046] (A7) In any of embodiments (A1)-(A6), the first lens, the second lens, the third lens, and the fourth lens together have an effective focal length f. eff This allows the image to be formed on the image plane.

[0047] (A8) In any of embodiments (A1)-(A7), the first lens and the third lens have respective focal lengths f1 and f3, and the ratio (f1+f3)f eff / (f1f3) is greater than -2.5 and less than -0.3.

[0048] (A9) In any of embodiments (A1)-(A8), the second lens and the fourth lens have respective focal lengths f2 and f4, and the ratio (f2+f4)f eff / (f2f4) is greater than 0.4 and less than 3.

[0049] (A10) In any of the embodiments (A1)-(A9), the image-side surface of the first lens is concave at the optical axis of the four coaxially aligned lenses.

[0050] (A11) In any of the embodiments (A1)-(A10), at the optical axis of the four coaxially aligned lenses, the object-side surface of the second lens and the image-side surface of the third lens are convex and concave, respectively.

[0051] (A12) In any of the embodiments (A1)-(A11), the object-side surface of the fourth lens is convex at the optical axis of the four coaxially aligned lenses.

[0052] Modifications to the above methods and systems may be made without departing from the scope of the embodiments of the present invention. Therefore, it should be noted that the content contained in the above specification or shown in the accompanying drawings should be interpreted as illustrative rather than restrictive. In this document, unless otherwise stated, the phrase "in embodiments" is equivalent to the phrase "in some embodiments" and does not refer to all embodiments. The following claims are intended to cover all general and specific features described herein, as well as all statements regarding the scope of the inventive methods and systems that are linguistically adequate to fall between the two.

Claims

1. A composite lens, comprising: Four coaxially aligned lenses, including a first lens, and a second lens, an inter-lens substrate, a third lens, and a fourth lens arranged in order of increasing distance from the first lens and on the same side thereof; The first lens and the third lens are negative lenses; The second lens and the fourth lens are positive lenses. The fourth lens has a planar object-side surface facing the third lens; The composite lens further includes an object-side substrate. The first lens, the second lens, the third lens, and the fourth lens together have an effective focal length. This allows the image to be formed at a distance from the object-side surface of the object-side substrate. At the image plane, and the ratio satisfy ; The first lens and the third lens each have their own focal length. and ,ratio Greater than -2.5 and less than -0.3; and The second lens and the fourth lens each have their own focal length. and ,ratio Greater than 0.4 and less than 3.

2. The composite lens according to claim 1, wherein the second lens has a planar image-side surface on the planar object-side surface of the inter-lens substrate, and the third lens has a planar object-side surface on the planar image-side surface of the inter-lens substrate.

3. The composite lens according to claim 1 further includes an image-side substrate, wherein the planar object-side surface of the fourth lens is on the planar image-side surface of the image-side substrate.

4. The composite lens according to claim 1, wherein the first lens has a planar object-side surface on the planar image-side surface of the object-side substrate.

5. The composite lens according to claim 1, wherein the Abbe number of the first lens is at least 37 and the Abbe number of the fourth lens is at least 26.

6. The composite lens according to claim 1, wherein the image-side surface of the first lens is concave at the optical axis of the four coaxially aligned lenses.

7. The composite lens according to claim 1, wherein at the optical axis of the four coaxially aligned lenses, the object-side surface of the second lens and the image-side surface of the third lens are convex and concave, respectively.

8. The composite lens according to claim 1, wherein the image-side surface of the fourth lens is convex at the optical axis of the four coaxially aligned lenses.

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