Variable focal length lens device

Abstract

To provide a variable focal length lens device capable of securing a wide scan range.SOLUTION: A variable focal length lens device 1 includes: a variable focal length optical system 10A that changes a focal length; a beam splitter 15 that causes passing light, which is reflected off an object W and passes through the variable focal length optical system 10A, to branch into branched beams L1 and L2; image-forming lenses 16 and 17 that condense the branched beams L1 and L2 respectively; an imaging element 21 that captures an image of the object W by receiving the branched beam L1 condensed by the image-forming lens 16; and an imaging element 22 that captures an image of the object W by receiving the branched beam L2 condensed by the image-forming lens 17. An imaging distance D1 on an optical axis from the imaging element 21 to the image-forming lens 16 and an imaging distance D2 on an optical axis from the imaging element 22 to the image-forming lens 17 are different from each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a variable focal length lens device. [Background technology]

[0002] In recent years, a liquid resonance lens, which is a refractive index distribution type focal length variable lens, has been developed, and a focal length variable lens device is known as a microscope system configured by combining this liquid resonance lens with an objective lens (see, for example, Patent Document 1). In this focal length variable lens device, the refractive index of the liquid resonance lens changes periodically in response to a drive signal, causing the focal position to vary periodically, making it possible to obtain a focused image over a wide range in the optical axis direction without using a mechanical lens drive means. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-074722 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned variable focal length lens device, the range of variation of the focal position (i.e., the scan range in the optical axis direction in which a focused image can be obtained) is determined according to the optical magnification of the objective lens, and the higher the optical magnification of the objective lens, the smaller the scan range. Therefore, when performing an inspection or the like that requires high resolution, the higher the magnification of the objective lens used, the narrower the scan range becomes, which is a problem. An object of the present invention is to provide a variable focal length lens device that can ensure a wide scanning range. [Means for solving the problem]

[0005] A variable focal length lens device according to one embodiment of the present invention comprises a variable focal length optical system that changes a focal length, a beam splitter that splits a passing light reflected by an object and passing through the variable focal length optical system into a first branched light and a second branched light, one or more imaging lenses that collect the passing light before it is split by the beam splitter or that collect the first branched light and the second branched light, respectively, a first imaging element that images the object by receiving the collected first branched light, and a second imaging element that images the object by receiving the collected second branched light, wherein a first imaging distance, which is the distance on the optical axis from the first imaging element to the imaging lens arranged immediately before the first imaging element, and a second imaging distance, which is the distance on the optical axis from the second imaging element to the imaging lens arranged immediately before the second imaging element, are different from each other.

[0006] In such a configuration, the range of variation of the focus position of the image formed by the first imaging element (hereinafter, the first focus position) and the range of variation of the focus position of the image formed by the second imaging element (hereinafter, the second focus position) are arranged at different positions on the optical axis. Therefore, the combined range of variation of the first focus position and the second focus position is wider than each of the ranges of variation alone. Therefore, a wider scan range than conventionally possible can be secured for acquiring a focused image.

[0007] In one embodiment of the present invention, a gap may exist on the optical axis between a range of variation of a first focusing position, which is the focusing position of an image formed by the first imaging element, and a range of variation of a second focusing position, which is the focusing position of an image formed by the second imaging element.

[0008] In one aspect of the present invention, a range of variation of a first focusing position, which is the focusing position of an image formed by the first imaging element, and a range of variation of a second focusing position, which is the focusing position of an image formed by the second imaging element, may be continuous with each other on the optical axis.

[0009] The variable focal length lens device according to an aspect of the present invention may further include a movement mechanism that moves the second imaging element along the incident direction of the second split light. In such a configuration, the difference between the first imaging distance and the second imaging distance can be easily changed.

[0010] In one aspect of the present invention, the variable focal length optical system comprises an objective lens, an intermediate imaging lens that collects light from the objective lens to form an intermediate image, a relay lens that relays the intermediate image to infinity together with the imaging lens, and a variable focal length lens that is arranged between the relay lens and the one or more imaging lenses and has a refractive index that changes periodically in response to an input drive signal, and it is preferable that the front principal point of the variable focal length lens has a conjugate relationship with the exit pupil of the objective lens. In this configuration, even if the first and second focusing positions change, the magnifications of the images incident on the first and second imaging elements are constant, making it easy to perform observation while changing the first and second focusing positions.

[0011] In one aspect of the present invention, the variable focal length optical system may further include a diaphragm disposed at a rear focus of the objective lens and a front focus of the intermediate imaging lens. In such a configuration, a double-telecentric optical system including a variable focal length optical system is formed, so that the sizes of the images incident on the first imaging element and the second imaging element can be made to be the same.

[0012] The variable focal length lens device according to an aspect of the present invention may further include an image processing unit that aligns the sizes of a first image output from the first imaging element and a second image output from the second imaging element. Effect of the Invention

[0013] According to the present invention, it is possible to provide a variable focal length lens device that can ensure a wider scan range than conventional ones. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a variable focal length lens device according to an embodiment of the present invention; [Diagram 2] 5A to 5C are diagrams illustrating changes in the focal position caused by the variable focal length lens device according to the embodiment. [Diagram 3] FIG. 2 is a block diagram showing a variable focal length lens device according to the embodiment. [Figure 4] 6 is a graph illustrating an example of a fluctuation waveform of a focus position in the embodiment. [Diagram 5] 6 is a graph illustrating an example of a fluctuation waveform of a focus position in the embodiment. [Figure 6] FIG. 11 is a schematic diagram showing a variable focal length lens device according to a modified example of the embodiment. [Figure 7] FIG. 11 is a schematic diagram showing a variable focal length lens device according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, one embodiment of the present invention will be described. 1 is a schematic diagram of a variable focal length lens device 1 according to this embodiment. This variable focal length lens device 1 periodically changes two focus positions Pf1, Pf2 and acquires images Im1, Im2 of an object W corresponding to each of the focus positions Pf1, Pf2.

[0016] (Configuration of variable focal length lens device) As shown in FIG. 1, the variable focal length lens device 1 includes an imaging optical system 10, an imaging unit 20 that images an object W through the imaging optical system 10, an illumination unit 30 that illuminates the object W, a lens control unit 40 that controls the operation of the liquid resonance lens 14 included in the imaging optical system 10, and a control device 50 that operates the lens control unit 40 and performs image processing, etc.

[0017] The imaging optical system 10 includes a variable focal length optical system 10A that periodically changes the focal length, a beam splitter 15 that splits the transmitted light reflected by an object W and passing through the variable focal length optical system 10A into branched light L1 and L2, an imaging lens 16 that collects the branched light L1, and an imaging lens 17 that collects the branched light L2.

[0018] The variable focal length optical system 10A has an objective lens 11, an intermediate imaging lens 12, a relay lens 13, and a liquid resonance lens 14. The objective lens 11, the intermediate imaging lens 12, the relay lens 13, and the liquid resonance lens 14 are arranged on an optical axis A1 in this order from the object side (front side).

[0019] The objective lens 11 is an infinity-corrected lens disposed opposite the object W, and emits light incident from the object W as a parallel light beam. The intermediate imaging lens 12 collects the parallel light beam incident from the objective lens 11 to form an intermediate image. Moreover, the rear focal position of the objective lens 11 and the front focal position of the intermediate imaging lens 12 are at the same position on the optical axis, and an aperture 18 is disposed at that position. Of the light incident on the objective lens 11, light whose chief ray is parallel to the optical axis passes through the aperture 18, and the chief ray of the light that has passed through the aperture 18 becomes parallel to the optical axis on the image side after leaving the intermediate imaging lens 12 (double-sided telecentric).

[0020] The relay lens 13 is an infinity-corrected lens arranged on the image side of the intermediate imaging lens 12, and constitutes a relay optical system together with the imaging lenses 16 and 17. The relay optical system relays the intermediate image formed by the intermediate imaging lens 12 to infinity.

[0021] The liquid resonance lens 14 is disposed on the image side of the relay lens 13, i.e., between the relay lens 13 and the imaging lenses 16 and 17, and has a front principal point that is conjugate with the exit pupil of the objective lens 11. This liquid resonance lens 14 is configured as a gradient index type variable focal length lens.

[0022] A known technique can be used for the specific configuration of the liquid resonance lens 14. For example, the liquid resonance lens 14 has a cylindrical case filled with liquid and a cylindrical vibration member made of a piezoelectric material. This vibration member is connected to the lens control unit 40 via a signal line while immersed in the liquid in the case, and vibrates in response to a drive signal Cf (e.g., a sinusoidal AC signal) input from the lens control unit 40. When the frequency of the drive signal Cf is adjusted to a resonance frequency, a standing wave is generated in the liquid inside the liquid resonance lens 14, and the refractive index of the liquid changes periodically. The case of the liquid resonance lens 14 has a window portion through which light passes, and the refractive index of the liquid in the case changes periodically, thereby causing the refractive index of the liquid resonance lens 14 to change periodically. This causes the focal length of the focal length variable optical system 10A to change periodically, and as a result, the focal positions Pf1 and Pf2 of the images formed by the image pickup elements 21 and 22 of the imaging unit 20 to change periodically (see FIG. 2).

[0023] 1, the beam splitter 15 is an optical component that splits incident light into two beams, and is disposed on the image side of the variable focal length optical system 10A, i.e., between the liquid resonance lens 14 and the imaging lenses 16 and 17. The beam splitter 15 splits the transmitted light that has passed through the liquid resonance lens 14 into a branched light L1 that passes through the beam splitter 15 and a branched light L2 that is reflected by the beam splitter 15. The branched light L1 travels along the optical axis A1, and the branched light L2 travels along the optical axis A2 that is perpendicular to the optical axis A1.

[0024] Each of the imaging lenses 16 and 17 relays the intermediate image formed by the intermediate imaging lens 12 together with the relay lens 13, and re-images the intermediate image at each of the imaging elements 21 and 22 of the imaging unit 20. Specifically, the imaging lens 16 is disposed on the optical axis A1, and re-images the intermediate image at the imaging element 21 by collecting the branched light L1 branched by the beam splitter 15. The imaging lens 17 is disposed on the optical axis A2, and re-images the intermediate image at the imaging element 22 by collecting the branched light L2 branched by the beam splitter 15.

[0025] In this embodiment, each of the objective lens 11, the intermediate imaging lens 12, the relay lens 13, and the imaging lenses 16 and 17 may be configured as a lens group combining a plurality of lenses. In this embodiment, the imaging lenses 16 and 17 have the same configuration and the same focal length.

[0026] The imaging unit 20 includes an imaging element 21 corresponding to the first imaging element of the present invention, and an imaging element 22 corresponding to the second imaging element of the present invention. Each of the imaging elements 21 and 22 is an existing CCD (Charge Coupled Device) image sensor or the like. The image sensor 21 has an image sensor surface 210 disposed perpendicular to the optical axis A1. The image sensor 21 receives the branched light L1 collected by the imaging lens 16 on the image sensor surface 210 to capture an image of the object W, and outputs an image Im1 in a predetermined signal format to the control device 50. Similarly, the image sensor 22 has an image sensor surface 220 disposed perpendicular to the optical axis A2. The image sensor 21 receives the branched light L2 collected by the imaging lens 17 on the image sensor surface 220 to capture an image of the object W, and outputs an image Im2 in a predetermined signal format to the control device 50.

[0027] Here, imaging distance D1, which is the distance on optical axis A1 from the image sensor 21 to the immediately preceding imaging lens 16 (for example, from the imaging surface 210 of the image sensor 21 to the principal point of the imaging lens 16), and imaging distance D2, which is the distance on optical axis A2 from the image sensor 22 to the immediately preceding imaging lens 17 (for example, from the imaging surface 220 of the image sensor 22 to the principal point of the imaging lens 17), are different distances. Specifically, the imaging distance D1 is set to a distance X, and the imaging distance D2 is set to a distance X+aβ 2 Here, it is preferable that the distance X is a value that is set so that the image sensor 21 is disposed within the focal depth of the image pickup optical system 10. Similarly, the distance X+aβ 2 is preferably a value that is set so that the image sensor 22 is located within the focal depth of the imaging optical system 10.

[0028] For example, distance X is the back focal length of imaging lenses 16 and 17 . Also, the distance X+aβ 2 The parameter a in corresponds to the difference between the in-focus position Pf1 and the in-focus position Pf2 at any point in time (see FIG. 2). This parameter a can be set to any value other than 0, and is preferably equal to or greater than (Z1+Z2) / 2. Also, the distance X+aβ 2 The parameter β in corresponds to the lateral magnification of the imaging optical system 10. In particular, when the relay optical system formed by the relay lens 13 and the imaging lenses 16 and 17 is a unity magnification relay, the parameter β corresponds to the lateral magnification of the objective lens 11.

[0029] Since the imaging distances D1 and D2 are different from each other, a fluctuation range Z1 of the in-focus position Pf1 of the image formed by the imaging element 21 and a fluctuation range Z2 of the in-focus position Pf2 of the image formed by the imaging element 22 are different from each other on the optical axis A1. Note that in this embodiment, the imaging lenses 16 and 17 have the same focal length, so the fluctuation ranges Z1 and Z2 have the same dimensions.

[0030] In FIG. 1, the illumination unit 30 includes a light source 31 that emits light, and a beam splitter 32 that guides the light emitted from the light source 31 to an object W. The light source 31 is configured with a light emitting element such as an LED. The light source 31 is controlled by the lens control unit 40, and may emit pulsed light at a timing synchronized with an arbitrary phase of the drive signal Cf, or may emit continuous light. The beam splitter 32 is disposed between the objective lens 11 and the intermediate imaging lens 12, and reflects the light emitted from the light source 31 toward the objective lens 11. The light reflected by the beam splitter 32 is irradiated onto the object W via the objective lens 11. The beam splitter 32 also transmits the light reflected by the object W and passing through the objective lens 11.

[0031] The lens control unit 40 controls the operations of the liquid resonance lens 14, the imaging unit 20, and the illumination unit 30. Specifically, as shown in Fig. 3, the lens control unit 40 has a drive control unit 41 that outputs a drive signal Cf to the liquid resonance lens 14, an imaging control unit 42 that outputs an imaging signal Cc to the imaging unit 20, and an emission control unit 43 that outputs an emission signal Ci to the light source 31. The lens control unit 40 may be configured as hardware using multiple ICs or the like, or may be configured mainly with a computer equipped with a CPU, and realized by the CPU executing a program stored in a storage unit.

[0032] The drive control unit 41 detects the vibration state Vf of the liquid resonance lens 14, and outputs a sinusoidal AC signal controlled based on the detected vibration state Vf as the drive signal Cf. The vibration state Vf of the liquid resonance lens 14 can be detected by using one or more of the drive voltage, drive current, active power, and voltage-current phase difference, which is the phase difference between the drive voltage and drive current, supplied to the liquid resonance lens 14 by the drive signal Cf, either alone or in combination.

[0033] The imaging control unit 42 controls the timing of image detection of the imaging unit 20 by the imaging signal Cc. Each of the imaging elements 21, 22 of the imaging unit 20 detects one frame of images Im1, Im2 by continuing exposure only during the period from on to off of the imaging signal Cc. For example, the imaging signal Cc continues to be in the on state for multiple cycles of the drive signal Cf.

[0034] The light emission control unit 43 uses the light emission signal Ci to control the light source 31. For example, when the light emission control unit 43 outputs a pulsed light emission signal Ci at a timing when the drive signal Cf has an arbitrary phase, the light source 31 can emit a pulsed light at a timing synchronized with the phase.

[0035] The control device 50 is a device configured by a general-purpose personal computer. The control device 50 includes an arithmetic circuit such as a CPU and a storage unit, and functions as a lens operation unit 51, an image processing unit 52, and a display control unit 53 by the arithmetic circuit reading and executing software recorded in the storage unit. In addition, a display unit 54 such as a display and an operation unit 55 such as a keyboard are connected to the control device 50 as a user interface.

[0036] The lens operation unit 51 performs various settings for the lens control unit 40 . The image processing unit 52 captures and processes the images Im1 and Im2 from the image pickup devices 21 and 22. The display control unit 53 causes the display unit 54 to display the images Im1, Im2, etc., processed by the image processing unit 52. The display control unit 53 may cause the display unit 54 to simultaneously display the images Im1, Im2, or may cause the display unit 54 to switch between the images based on a user operation or the like.

[0037] In the variable focal length lens device 1 described above, when imaging an object W, it is possible to obtain an image Im1 focused at a desired height position within the variation range Z1 of the focusing position Pf1, and an image Im2 focused at a desired height position within the variation range Z2 of the focusing position Pf2. For example, when the light source 31 emits pulsed light at a timing synchronized with an arbitrary phase of the drive signal Cf, images Im1 and Im2 focused at the focusing positions Pf1 and Pf2 corresponding to the phases can be simultaneously acquired. Also, when the light source 31 irradiates continuous light, images Im1 and Im2 can be simultaneously acquired as focal sweep images in which the focusing positions Pf1 and Pf2 change continuously within the variation ranges Z1 and Z2.

[0038] (effect) In this embodiment, as described above, the imaging distance D1 from the imaging element 21 to the imaging lens 16 and the imaging distance D2 from the imaging element 22 to the imaging lens 17 are different from each other. As a result, the variation range Z1 of the focal position Pf1 of the image formed by the imaging element 21 and the variation range Z2 of the focal position Pf2 of the image formed by the imaging element 22 are disposed at different positions on the optical axis (see FIG. 2). The combined range of the variation range Z1 of the focal position Pf1 and the variation range Z2 of the focal position Pf2 is wider than one variation range Z1 (or variation range Z2), and can be used as a scan range capable of acquiring a focused image. Therefore, in this embodiment, a scan range capable of acquiring a focused image can be secured wider than in the past. As a result, even when a high-magnification objective lens 11 is used, a wide scan range capable of acquiring a focused image can be secured.

[0039] Here, examples of fluctuation waveforms of the focus positions Pf1 and Pf2 are shown in FIGS. In this embodiment, as shown in FIG. 4, the parameter a is greater than (Z1+Z2) / 2, so that a gap G on the optical axis may exist between the variation range Z1 of the focal position Pf1 and the variation range Z2 of the focal position Pf2. For example, when pulsed illumination is performed at an arbitrary detection phase θd, an image Im1 focused at the focal position Pf1-d corresponding to the detection phase θd and an image Im2 focused at the focal position Pf2-d corresponding to the detection phase θd are respectively acquired. In this case, the larger the gap G, the larger the difference Dd between the focal position Pf1-d and the focal position Pf2-d. For example, images Im1 and Im2 focused at two positions that are farther apart than the dimensions of the variation ranges Z1 and Z2 of the focal positions Pf1 and Pf2 can be simultaneously acquired.

[0040] In this embodiment, as shown in Fig. 5, the parameter a is equal to (Z1+Z2) / 2, so that the range Z1 of the focal position Pf1 and the range Z2 of the focal position Pf2 may be continuous with each other on the optical axis. In this case, images Im1 and Im2 focused at desired positions in the continuous range (Z1+Z2) that combines the range Z1 of the focal position Pf1 and the range Z2 of the focal position Pf2 can be obtained. For example, by repeating imaging, images (image Im1 or image Im2) focused at n positions at a predetermined pitch from the position T1 corresponding to the negative peak of the focal position Pf1 to the position Tn corresponding to the positive peak of the focal position Pf2 can be obtained.

[0041] In this embodiment, the diaphragm 18 is disposed at the rear focal point of the objective lens 11 and the front focal point of the intermediate imaging lens 12. The front principal point of the liquid resonance lens 14 is disposed so as to be conjugate with the exit pupil of the objective lens 11. Furthermore, the front focal points of the lenses 16 and 17 are disposed so as to coincide with the rear principal point of the liquid resonance lens 14. As a result, the imaging optical system 10 of this embodiment is configured as a double-telecentric optical system. According to this configuration, the sizes of the images incident on the image sensor 21 and the image sensor 22 can be made uniform. This makes it easy to compare the images Im1 and Im2 with each other without performing a process to adjust the sizes of the images Im1 and Im2. Furthermore, according to this configuration, the exit pupil of the objective lens 11 is telecentrically relayed, so that the magnifications of the images incident on the image sensors 21 and 22 are constant even if the focal positions Pf1 and Pf2 change. This makes it easy to perform observation while changing the focal positions Pf1 and Pf2.

[0042] [Variations] The present invention is not limited to the above-described embodiment, and modifications within the scope of the present invention are included in the present invention.

[0043] As shown in FIG. 6, the variable focal length lens device 1A according to the modified example may further include a movement mechanism 60 that moves the image sensor 22 along the incident direction of the branched light L2 (i.e., the optical axis A2). The movement mechanism 60 may have an arbitrary drive source, or may be manually operated by a user. The movement mechanism 60 moves the image sensor 22, thereby changing the difference between the imaging distance D1 and the imaging distance D2 (i.e., the distance X+aβ 2 Of these, aβ 2 The difference a (see FIG. 2) between the in-focus position Pf1 and the in-focus position Pf2 at any point in time is changed. With this configuration, the distance between the fluctuation range Z1 of the in-focus position Pf1 and the fluctuation range Z2 of the in-focus position Pf2, or the overlapping range of the fluctuation ranges Z1 and Z2, etc. can be easily changed.

[0044] As shown in FIG. 7, in the focal length variable lens device 1B according to the modified example, the beam splitter 15 may be disposed between the imaging lens 16 and the image sensor 21. In this case, the focal length variable lens device 1B includes the imaging lens 16 but does not include the imaging lens 17. The imaging lens 16 collects the light that has passed through the liquid resonance lens 14 and before being split by the beam splitter 15. With this configuration, the number of lenses used can be reduced while relaying the intermediate images to the image sensors 21 and 22. The imaging distance D2 is the distance along the optical axes A1 and A2 from the image sensor 22 to the immediately preceding imaging lens 16. Specifically, in FIG. 7, the imaging distance D2 is the sum of the distance D2-1 from the image sensor 22 to the beam splitter 15 and the distance D2-2 from the beam splitter 15 to the imaging lens 16.

[0045] In the above embodiment, the imaging optical system 10 is not limited to being bilaterally telecentric, and may be object-side telecentric. In this case, the image size may be different between the image Im1 output from the imaging element 21 and the image Im2 output from the imaging element 22. In this case, the image processing unit 52 may perform image processing to make the sizes of the images Im1 and Im2 uniform. Note that the size standard may be one of the images Im1 and Im2, or the other standard.

[0046] In the above embodiment, if fluctuations in size of the images Im1, Im2 due to fluctuations in the focus positions Pf1, Pf2 are not an issue, the imaging optical system 10 does not need to be bilaterally telecentric or object-side telecentric.

[0047] In the above embodiment, the beam splitter 15 divides the passing light that passes through the liquid resonance lens 14 at an arbitrary ratio, but it may also be possible to temporally split the passing light into a first branched light and a second branched light by switching between reflection and transmission.

[0048] In the above embodiment, the imaging element 21 corresponds to the first imaging element of the present invention, and the imaging element 22 corresponds to the second imaging element of the present invention, but the correspondence between them may be reversed. For example, the moving mechanism 60 described in the above modification may move the imaging element 21 along the incident direction of the branched light L1 (i.e., the optical axis A1).

[0049] The variable focal length lens device 1 of the embodiment includes two imaging elements 21 and 22, but may include three or more imaging elements. For example, the variable focal length lens device 1 of the embodiment may further include a second beam splitter that branches a third branched light from any of the branched lights, a third imaging lens that collects the third branched light, and a third imaging element that captures an image formed by the third imaging lens. When the imaging distance from the third imaging element to the third imaging lens is different from the imaging distances D1 and D2, a wider scan range can be ensured in which a focused image can be acquired.

[0050] In the above embodiment, a liquid resonance lens 14 whose refractive index changes according to the input drive signal Cf is described as the variable focal length lens of the present invention, but other types of variable focal length lenses whose focal length can be changed within a predetermined range by any means may also be used. [Explanation of symbols]

[0051] 1, 1A, 1B... variable focal length lens device, 10... imaging optical system, 10A... variable focal length optical system, 11... objective lens, 12... intermediate imaging lens, 13... relay lens, 14... liquid resonance lens, 15... beam splitter, 16... imaging lens, 17... imaging lens, 18... aperture, 20... imaging unit, 21... imaging element (first imaging element), 210... imaging surface, 22... imaging element (second imaging element), 220... imaging surface, 30... illumination unit, 31... light source, 32... beam splitter, 40... lens control unit, 41... drive control unit, 42... imaging control unit, 4 3...light emission control unit, 50...control device, 51...lens operation unit, 52...image processing unit, 53...display control unit, 54...display unit, 55...operation unit, 60...movement mechanism, A1, A2...optical axis, Cc...imaging signal, Cf...driving signal, Ci...light emission signal, D1...imaging distance (first imaging distance), D2...imaging distance (second imaging distance), G...gap, Im1, Im2...image, L1...branched light (first branched light), L2...branched light (second branched light), Pf1...focusing position (first focusing position), Pf2...focusing position (second focusing position), Vf...vibration state, W...object, Z1, Z2...variation range.

Claims

1. A variable focal length optical system that changes a focal length; a beam splitter that splits light reflected by an object and passing through the variable focal length optical system into a first split light and a second split light; one or more imaging lenses that collect the passing light before being split by the beam splitter or that collect each of the first split light and the second split light; a first imaging element that receives the first branched light and captures an image of the object; a second image sensor configured to receive the collected second split light and capture an image of the object; A variable focal length lens device, in which a first imaging distance, which is the distance on the optical axis from the first imaging element to the imaging lens arranged immediately before the first imaging element, and a second imaging distance, which is the distance on the optical axis from the second imaging element to the imaging lens arranged immediately before the second imaging element, are different from each other.

2. 2. The variable focal length lens device according to claim 1, wherein a gap exists on the optical axis between a range of variation of a first focusing position, which is the focusing position of an image formed by the first imaging element, and a range of variation of a second focusing position, which is the focusing position of an image formed by the second imaging element.

3. 2. The variable focal length lens device according to claim 1, wherein a range of variation of a first focusing position, which is the focusing position of an image formed by the first imaging element, and a range of variation of a second focusing position, which is the focusing position of an image formed by the second imaging element, are continuous with each other on the optical axis.

4. The variable focal length lens device according to claim 1 , further comprising a movement mechanism that moves the second image pickup element along the incident direction of the second split light.

5. The variable focal length optical system includes: An objective lens; an intermediate imaging lens that collects light from the objective lens to form an intermediate image; a relay lens that relays the intermediate image to infinity together with the imaging lens; a variable focal length lens that is disposed between the relay lens and the one or more imaging lenses and has a refractive index that changes periodically in response to an input drive signal; 2. The variable focal length lens device according to claim 1, wherein a front principal point of the variable focal length lens has a conjugate relationship with an exit pupil of the objective lens.

6. The variable focal length lens device according to claim 5 , wherein the variable focal length optical system further comprises a diaphragm disposed at a rear focus of the objective lens and a front focus of the intermediate imaging lens.

7. The variable focal length lens device according to claim 5 , further comprising an image processing unit that equalizes the sizes of a first image output from the first imaging element and a second image output from the second imaging element.

Images