Imaging optical system and imaging device

Abstract

In these imaging optical system and imaging device, the imaging optical system forms, for each lens pair comprising a first lens and a second lens facing each other of a first lens array and a second lans array, a partial image comprising a light flux from a part of a subject on an imaging surface, and forms a whole image of the subject on the imaging surface by combining partial images formed on the imaging surface by a plurality of lens pairs of the first lens array and the second lens array. In the imaging optical system, halfway between the two lens arrays in an optical axis direction, an optical element is provided at a distance S1 from each of the two lens arrays and at a position where an intermediate image is formed by a first lens adjacent to a first lens facing at least the part of the subject, and the intermediate image is formed on the imaging surface by a second lens facing the adjacent first lens and superimposed on a partial image formed by a lens pair including the first lens facing the part of the subject.

Description

Imaging Optical System and Imaging Device

[0001] The present disclosure relates to an imaging optical system and an imaging device.

[0002] Japanese Patent No. 6462837 describes an observation method using a microphotographing device that enables easy observation of an observation target.

[0003] Japanese Unexamined Patent Application Publication No. 2020-008667 describes a microscopic observation device that can easily observe the entire observation target using fluorescence from the observation target irradiated with excitation light.

[0004] Even if an attempt is made to shorten the optical path length with a normal imaging optical system, there is a limit to the focal length due to restrictions in lens design, and thus it is restricted. If the diameter of the lens is reduced, the focal length also becomes smaller, but there are restrictions such as a smaller field of view.

[0005] In addition, in an imaging optical system, it is desirable to obtain a bright image when observing a subject.

[0006] An object of the present disclosure is to provide an imaging optical system and an imaging device that can achieve a short optical path length while maintaining a sufficient field of view and obtain a bright image.

[0007] The imaging optical system of this disclosure comprises: a first lens array configured by arranging a plurality of first lenses having the same optical performance and focal length fa on a two-dimensional plane; and a second lens array configured by arranging a plurality of second lenses having the same optical performance as the first lens array in the same manner as the first lens array, and with the optical axis of each of the plurality of second lenses aligned with the optical axis of each of the plurality of first lenses, the second lens array is positioned at a distance of 2S1 on the optical axis from the first lens array; and for each pair of lenses consisting of the first lens and the second lens facing each other in the first lens array and the second lens array, a partial image consisting of a light beam from a part of the subject is formed on the imaging surface, and the first lens array In an imaging optical system that combines partial images formed on the imaging surface by a plurality of lens pairs of Ray and the second lens array to form an overall image of a subject on the imaging surface, the optical element is further provided at a position midway between the first lens array and the second lens array in the optical axis direction, at a distance S1 from the first lens array and the second lens array, and at a position where an intermediate image is formed by a first lens adjacent to at least a first lens facing a part of the subject, the intermediate image is imaged onto the imaging surface by a second lens facing the adjacent first lens, and superimposed on the partial image formed by the lens pair including the first lens facing a part of the subject.

[0008] The imaging device of this disclosure comprises the imaging optical system of this disclosure and an image sensor.

[0009] According to the imaging optical system and imaging device of this disclosure, it is possible to obtain a bright image with a short optical path length while maintaining a sufficient field of view.

[0010] This is a schematic diagram of the imaging optical system of the first embodiment. This diagram illustrates the operation of the imaging optical system of the first embodiment. This is a schematic diagram of the imaging optical system of the second embodiment. This diagram illustrates the operation of the imaging optical system of the second embodiment. This is a schematic diagram of the imaging optical system of the third embodiment. This diagram illustrates the operation of the imaging optical system of the third embodiment. This is an external view of the imaging device of the fourth embodiment. This is a schematic diagram of the imaging device of the fourth embodiment.

[0011] [First Embodiment] The imaging optical system of the first embodiment of this disclosure will be described below with reference to the drawings. Figure 1 is a schematic diagram of the imaging optical system 1 of the first embodiment. In Figure 1, the left side is the object side and the right side is the image side. Also in Figure 1, the optical axis Z and the image plane I of the imaging optical system 1 are shown together.

[0012] As shown in Figure 1, the imaging optical system 1 comprises a first microlens array 10, a second microlens array 20, and a third microlens array 30. The third microlens array 30 corresponds to an optical element in the technology of this disclosure.

[0013] The first microlens array 10 is composed of multiple first microlenses 11 having the same focal length fa and optical performance, arranged on a two-dimensional plane.

[0014] The second microlens array 20 is configured by arranging a plurality of second microlenses 21, which have the same optical performance as the first microlens 11, in the same manner as the first microlens array 10.

[0015] Furthermore, the second microlens array 20 is positioned at a distance of 2S1 on the optical axis from the first microlens array 10, with the optical axis of each of the multiple second microlenses 21 aligned with the optical axis Z of each of the multiple first microlenses 11.

[0016] In the imaging optical system 1, for each pair of lenses consisting of a first microlens 11 and a second microlens 21 facing each other in the first microlens array 10 and the second microlens array 20, a partial image Ip consisting of a light beam from a part of the subject is formed on the imaging surface Sim. The partial images Ip formed on the imaging surface Sim by multiple lens pairs of the first microlens array 10 and the second microlens array 20 are then combined to form an overall image Iw of the subject on the imaging surface Sim.

[0017] The third microlens array 30 is positioned midway between the first microlens array 10 and the second microlens array 20 in the optical axis Z direction, at a distance S1 from the first microlens array 10 and the second microlens array 20, and at a position where an intermediate image is formed by the first microlens 11 adjacent to the first microlens 11 that faces at least a part of the subject.

[0018] Furthermore, the third microlens array 30 is configured such that a plurality of third microlenses 31 are arranged in the same manner as the first lens array 10, and the optical axis Z of each of the plurality of third microlenses 31 is aligned with the optical axis Z of each of the plurality of first microlenses 11.

[0019] Here, the third microlens 31 is configured to satisfy the following conditions (1) and (2): fa < S1 < 2fa ... (1) fb = (1 / 2) × S1 ... (2) In conditions (1) and (2), fa: focal lengths of the first microlens 11 and the second microlens 21 fb: focal length of the third microlens 31 S1: distance from the first microlens 11 to the intermediate image, or distance from the intermediate image to the second microlens 21.

[0020] Furthermore, as shown in Figure 2, the third microlens array 30 is configured to superimpose an intermediate image Ipmb formed by a first microlens 11b adjacent to a first microlens 11a facing a part Opa of the subject onto a partial image Ipa1 formed by a lens pair including the first microlens 11a facing a part Opa of the subject, by imaging the intermediate image Ipmb formed by a second microlens 21 facing the adjacent first microlens 11b.

[0021] Here, we will explain in detail the contents of conditional expressions (1) and (2).

[0022] Assuming that each first microlens 11 in the first microlens array 10 is a thin lens with negligible thickness, the imaging relationship is given by equation (3) and the image magnification relationship is given by equation (4). (1 / S0) + (1 / S1) = 1 / f …(3) m = S1 / S0 …(4)

[0023] In equations (3) and (4), S0 is the distance from the object to the lens, S1 is the distance from the lens to the image, f is the focal length of the lens, and m is the magnification of the image relative to the object.

[0024] In Case 1, if the distance S0 from the object to the lens is set to infinity, then from equation (3), we can see that the distance S1 from the lens to the image becomes the focal length fa. When we calculate the magnification of the image in this case from equation (4), we find that the image becomes infinitely small.

[0025] Furthermore, in Case 2, when the distance S0 from the object to the lens and the distance S1 from the lens to the image are the same, we can see from equation (3) that S0 = S1 = f / 2. Also, if we can find the magnification of the image in this case from equation (4), we can see that the magnification is 1, that is, the size of the object and the image are the same.

[0026] In this embodiment, the first microlens 11 constituting the first microlens array 10 can be imaged within the range of Case 1 to Case 2. That is, if the size of the subject captured by one microlens is equal to the size of the microlens, the size of the intermediate image will range from infinitesimally small to the same diameter as the third microlens 31. By keeping the intermediate image within this size range, the overall image formed by this optical system can be created. The second microlens 21 constituting the second microlens array 20 has the same optical performance as the first microlens 11. Furthermore, regarding infinity, even an imaged distance of about 10 mm can be considered as infinity if the lens is sufficiently small and the focal length is sufficiently short. The focal length fb of the third microlens 31 is half the image-side focal length S1 of the first microlens 11.

[0027] Furthermore, if fb is the focal length of the third microlens 31 constituting the third microlens array 30 used in the imaging optical system 1 of this embodiment, then fb must be set to half the object-side imaging distance and the image-side imaging distance of the third microlens array 30. With this relationship, according to equation (3), the third microlens 31 adjacent to the opposing pair of microlenses propagates the light ray passing through the center of the adjacent first microlens 11 to the second microlens 21 as a light ray symmetrical to the plane of the third microlens array 30, and further forms an image at a position symmetrical to the subject (see Figure 2). This image then superimposes on the image formed by the optical system consisting of the directly opposing first, second, and third microlenses. At this time, fb is expressed by equation (5) based on equations (3) and (4). fb = S1 / 2 = (1 / 2) × [fa / {1 - (fa / S0)}] = fa × (m+1) / 2 …(5)

[0028] In equation (5), S0 is the distance from the object to the lens in the first microlens 11, S1 is the distance from the lens to the image in the first microlens 11, m is the magnification of the image relative to the object, fa is the focal length of the first microlens 11 (the same applies to the second microlens 21), and fb is the focal length of the third microlens 31.

[0029] In the imaging optical system 1 of this embodiment, since the objective is to have a short optical path length, it is not practical to set the imaging distance on the object side of the first microlens array 10 to infinity.

[0030] Therefore, they are placed at a finite distance that can be approximated as infinity. The determination of the infinity approximation here is as follows: The image (primary image) of the first microlens 11 is formed in the paired third microlens 31. At that time, the image formed near the center of the third microlens 31 is an inverted image of the object, but aberrations become large at points with high image heights away from the center, which degrades the quality of the image finally formed by the imaging optical system 1.

[0031] Here, the image height of the primary image decreases as the object-side imaging distance of the first microlens 11 increases. In other words, there is a trade-off relationship between the object-side imaging distance and image quality.

[0032] Furthermore, the focal length fb of the third microlens 31 needs to be varied to match the image-side imaging distance of the first microlens 11. The minimum limit for this variation is fa / 2, at which point the image quality is best.

[0033] The object-side imaging distance of the first microlens 11 is determined by how much image quality degradation is tolerable, and this determines how much the focal length of the intermediate lens should be greater than fa / 2. By configuring the system to satisfy equation (5), a short optical path length can be achieved while maintaining a sufficient field of view. Conditional equations (1) and (2) can then be derived by rearranging equation (5).

[0034] Next, the operation of the imaging optical system 1 of this embodiment will be described.

[0035] As described above, in the imaging optical system 1 of this embodiment, the object to be observed is imaged using a first microlens array 10 and a second microlens array 20 having the same lens configuration. This makes it possible to maintain a sufficient field of view while having a short optical path length.

[0036] Furthermore, as shown in Figure 2, the third microlens array 30 superimposes an intermediate image Ipmb formed by a first microlens 11b adjacent to a first microlens 11a facing a portion Opa of the subject onto a partial image Ipa formed by a lens pair including the first microlens 11a facing a portion Opa of the subject, using a second microlens 21.

[0037] This makes it possible to increase the amount of light in the partial image Ipa compared to the case where a partial image Ipa is formed only by a lens pair including the first microlens 11a facing a part of the subject Opa. Therefore, a bright image can be obtained with the imaging optical system 1 of this embodiment.

[0038] [Second Embodiment] Next, the imaging optical system of the second embodiment will be described. Figure 3 is a schematic diagram of the imaging optical system 2 of the second embodiment.

[0039] The imaging optical system 2 of the second embodiment is different from the imaging optical system 1 of the first embodiment in that the optical element disposed between the first microlens array 10 and the second microlens array 20 is changed. In the present embodiment, the same reference numerals are assigned to the same components as those in the first embodiment, and the description of the same components is omitted unless particularly necessary.

[0040] As shown in FIG. 3, the imaging optical system 2 includes a first microlens array 10, a second microlens array 20, and a two-plane orthogonal reflector array 32.

[0041] The two-plane orthogonal reflector array 32 is configured as a set of two-plane orthogonal reflectors as unit elements having two orthogonal reflecting surfaces, and has a common plane perpendicular to the reflecting surfaces of all the unit elements as an element plane. From an optical viewpoint, each two-plane orthogonal reflector is configured with two side walls perpendicular to each other of an optical aperture through which light rays pass as reflecting surfaces.

[0042] Further, as shown in FIG. 4, the two-plane orthogonal reflector array 32 superimposes an intermediate image Ipmb formed by a first microlens 11b adjacent to a first microlens 11a facing a part Opa of the subject on a partial image Ipa formed by a lens pair including the first microlens 11a facing the part Opa of the subject by the second microlens 21.

[0043] Next, the operation of the imaging optical system 2 of the present embodiment will be described.

[0044] As described above, in the imaging optical system 2 of the present embodiment, an observation target is imaged using the first microlens array 10 and the second microlens array 20 having the same lens configuration. Thereby, a short optical path length can be achieved while maintaining a sufficient field of view.

[0045] Further, as shown in FIG. 4, the two-plane orthogonal reflector array 32 superimposes an intermediate image Ipmb formed by a first microlens 11b adjacent to a first microlens 11a facing a part Opa of the subject on a partial image Ipa formed by a lens pair including the first microlens 11a facing the part Opa of the subject by a second microlens 21.

[0046] As a result, the amount of light of the partial image Ipa can be increased as compared with the case where the partial image Ipa is formed only by the lens pair including the first microlens 11a facing the part Opa of the subject. From the above, in the imaging optical system 2 of the present embodiment, a bright image can be obtained.

[0047] [Third Embodiment] Next, the imaging optical system of the third embodiment will be described. FIG. 5 is a schematic configuration diagram of the imaging optical system 3 of the third embodiment.

[0048] The imaging optical system 3 of the third embodiment is different from the imaging optical system 1 of the first embodiment in that an optical element arranged between the first microlens array 10 and the second microlens array 20 is changed. In the present embodiment, the same reference numerals are assigned to the same components as those in the first embodiment, and the description of the same components is omitted unless particularly necessary.

[0049] As shown in FIG. 5, the imaging optical system 3 includes a first microlens array 10, a second microlens array 20, and a diffuser plate 33.

[0050] The diffuser plate 33 is configured to superimpose an intermediate image Ipmb formed by a first microlens 11b adjacent to a first microlens 11a facing a part Opa of the subject on a partial image Ipa formed by a lens pair including the first microlens 11a facing the part Opa of the subject by a second microlens 21, as shown in FIG. 6.

[0051] Next, the operation of the imaging optical system 3 of the present embodiment will be described.

[0052] As described above, in the imaging optical system 3 of this embodiment, the object to be observed is imaged using a first microlens array 10 and a second microlens array 20 having the same lens configuration. This makes it possible to maintain a sufficient field of view while having a short optical path length.

[0053] Furthermore, as shown in Figure 6, the diffuser plate 33 superimposes the intermediate image Ipmb, formed by the first microlens 11b adjacent to the first microlens 11a facing a portion Opa of the subject, onto the partial image Ipa formed by the lens pair including the first microlens 11a facing a portion Opa of the subject, using the second microlens 21.

[0054] This makes it possible to increase the light intensity of the partial image Ipa compared to the case where only a lens pair including the first microlens 11a facing a part of the subject Opa forms the partial image Ipa. As a result, a bright image can be obtained with the imaging optical system 3 of this embodiment.

[0055] [Fourth Embodiment] Next, an imaging device according to the fourth embodiment will be described. Figure 7 is an external view of the imaging device 100 according to the fourth embodiment. Figure 8 is a schematic configuration diagram of the imaging device 100 according to the fourth embodiment.

[0056] As shown in Figure 7, the imaging device 100 is a device for imaging the sample placed in the sample placement section 102a.

[0057] The imaging device 100 is used in conjunction with an information processing device such as a smartphone 110. The smartphone 110 can display the image of the sample captured by the imaging device 100 on its monitor 111.

[0058] As shown in Figure 8, the imaging device 100 comprises a housing 101, an imaging optical system 1, a cover glass 102, an image sensor 103, a signal processing unit 104, and an external connection terminal 105.

[0059] The imaging device 100 of this embodiment includes the imaging optical system 1 described in the first embodiment above, but the imaging optical system to be combined with the imaging device 100 may be the imaging optical system 2 described in the second embodiment above, or the imaging optical system 3 described in the third embodiment above.

[0060] The cover glass 102 has a surface (upper side in Figure 10) that functions as a sample placement area 102a.

[0061] The image sensor 103 is positioned at the imaging position of the imaging optical system 1 and captures the image formed by the imaging optical system 1.

[0062] The signal processing unit 104 performs the process of transmitting the signal output from the image sensor 103 to an external information processing device.

[0063] The external connection terminal 105 is a terminal for connecting to an external information processing device, and can be, for example, a USB (Universal Serial Bus) terminal.

[0064] Since the imaging device 100 of this embodiment is equipped with the imaging optical system 1 described in the first embodiment above, it is possible to maintain a sufficient field of view while having a short optical path length and acquiring a bright image.

[0065] [Modifications] The technology of this disclosure is not limited to the embodiments described above, and various modifications and applications are possible without departing from the gist of the technology of this disclosure.

[0066] The disclosure of Japanese Patent Application No. 2024-192166, filed on 31 October 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. An imaging optical system comprising: a first lens array configured by arranging a plurality of first lenses having the same focal length fa and optical performance on a two-dimensional plane; and a second lens array configured by arranging a plurality of second lenses having the same optical performance as the first lens array in the same manner as the first lens array, and with the optical axis of each of the plurality of second lenses aligned with the optical axis of each of the plurality of first lenses, the second lens array is positioned at a distance of 2S1 on the optical axis from the first lens array; wherein for each pair of opposing first and second lenses in the first and second lens arrays, a partial image consisting of a light beam from a part of the subject is formed on the imaging surface, and the partial images formed on the imaging surface by the plurality of lens pairs of the first and second lens arrays are combined to form a whole image of the subject on the imaging surface, Furthermore, the imaging optical system is characterized by providing an optical element at a position midway between the first lens array and the second lens array in the optical axis direction, at a distance S1 from the first lens array and the second lens array, and at a position where an intermediate image is formed by a first lens adjacent to at least a part of the subject, and by forming the intermediate image on the imaging surface with a second lens adjacent to the adjacent first lens, and superimposing it on a partial image formed by a lens pair including the first lens facing a part of the subject.

2. The imaging optical system according to claim 1, wherein the optical element is a third lens array configured by arranging a plurality of third lenses in the same manner as the first lens array, and the optical axes of each of the plurality of third lenses are aligned with the optical axes of each of the plurality of first lenses, and the imaging optical system according to claim 1 satisfies the following conditions: when the focal lengths of the first lens and the second lens are fa, the focal length of the third lens is fb, and the distance from the first lens to the intermediate image is S1, fa < S1 < 2fa ... (1) fb = (1 / 2) × S1 ... (2).

3. The imaging optical system according to claim 1, wherein the optical element is a two-plane orthogonal reflector array.

4. The imaging optical system according to claim 1, wherein the optical element is a diffuser plate.

5. An imaging apparatus comprising an imaging optical system according to any one of claims 1 to 4, and an image sensor.

Images