Focal length variable lens device

Abstract

A variable focal length lens device (201A) is provided with: a first variable focal length lens (11); a second variable focal length lens (21) disposed behind the first variable focal length lens (11); a third variable focal length lens (31) disposed behind the second variable focal length lens (21); a fixed focal length lens (41) disposed behind the third variable focal length lens (31); a first conjugate point (1) separated forward from the first variable focal length lens (11) by a first focal length (f1); a second conjugate point (2) separated rearward from the focal length fixed lens (41) by a fourth focal length (f4); and a third conjugate point (3) separated rearward from the second focal length variable lens (21) at a second focal length (f2) and forward from the third focal length variable lens (31) at a third focal length (f3), the first partial optical system (111) being an infinite conjugate system with respect to the first conjugate point (1), and the second partial optical system (121) being an infinite conjugate system with respect to the third conjugate point (3).

Description

Technical Field

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

[0002] Optical technology is applied to various devices such as processing devices, observation devices, distance measuring devices, and lighting devices. In such devices, it is required to be able to freely change the magnification and focal position of the optical system.

[0003] Generally speaking, in order to change the magnification and focal position, it is necessary to change the configuration of optical components such as lenses and shooting elements constituting the optical system in the direction of the optical axis. The device structure based on the movement of optical components has many problems from the perspectives of design complexity, device size, manufacturing cost and reliability. In particular, this problem is significant in the magnification adjustment mechanism that is difficult to deal with by simply extracting all or part of the lens group. Even so, in observation devices such as cameras and microscopes, the magnification and focal position are adjusted by using a mechanical drive mechanism, but this mechanical drive mechanism still has problems from the perspective of higher speed responsiveness on the basis of the above-mentioned problems.

[0004] On the other hand, a variable focal length lens device is provided that can make the focal length variable without a mechanical driving mechanism. In the variable focal length lens device, for example, a liquid lens using an electrowetting technique is used. The liquid lens is used as a variable focal length lens. Generally speaking, the liquid lens functions as a plano-convex lens or a plano-concave lens, and therefore, in order to suppress aberrations, it is preferably composed of an infinite conjugate system.

[0005] Patent Document 1 discloses a shape measuring device using the above-mentioned variable focal length lens.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-053491 Summary of the invention

[0007] The shape measuring device disclosed in Patent Document 1 has three focal variable lenses. Among them, one focal variable lens arranged on the object side is used to change the focal position. In addition, two focal variable lenses arranged on the image side are used to change the magnification. The principle of variable magnification is to adjust the ratio between the finite synthetic focal length and the focal length of the focal variable lens on the object side according to the formula of the synthetic lens through the two focal variable lenses on the image side so as to achieve the desired magnification. By using two focal variable lenses, the two degrees of freedom required for adjusting the focal length and the main surface position are ensured. On the other hand, in the present invention, the two focal variable lenses on the magnification adjustment side form an infinite conjugate system with two lenses as one group, so that the lens located on the most image side becomes a finite conjugate system when observed alone through the lens. Therefore, aberrations are easily generated.

[0008] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a variable focal length lens device capable of arbitrarily changing the magnification and focal position suitable for a variable focal length lens.

[0009] The focal length variable lens device of the present invention comprises: a first focal length variable lens having a first focal length; a second focal length variable lens disposed behind the first focal length variable lens and having a second focal length; a third focal length variable lens disposed behind the second focal length variable lens and having a third focal length; a focal length fixed lens disposed behind the third focal length variable lens and having a fourth focal length; a first conjugate point disposed at a position separated from the first focal length variable lens by the first focal length to the front and serving as a focal position; and a second conjugate point disposed at a position separated from the first focal length variable lens by the first focal length to the front and serving as a focal position. A shooting element or a light guide unit is arranged at a position separated by the fourth focal length backward from the fixed focal length lens; and a third conjugate point is arranged at a position separated by the second focal length backward from the second variable focal length lens and by the third focal length forward from the third variable focal length lens, a first partial optical system consisting of the first variable focal length lens and the second variable focal length lens is an infinite conjugate system relative to the first conjugate point, and a second partial optical system consisting of the third variable focal length lens and the fixed focal length lens is an infinite conjugate system relative to the third conjugate point.

[0010] Effects of the Invention

[0011] According to the present invention, the magnification and the focal position suitable for the variable focal length lens can be arbitrarily changed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a diagram showing a configuration of a variable focal length lens device according to Embodiment 1. FIG.

[0013] FIG. 2 is a diagram showing another configuration of the variable focal length lens device according to the first embodiment.

[0014] FIG. 3 is a diagram showing another configuration of the variable focal length lens device according to the first embodiment.

[0015] FIG. 4 is a diagram showing another configuration of the variable focal length lens device according to the first embodiment.

[0016] Figure 5 1 is a diagram showing the operation of the variable focal length lens device according to the first embodiment.

[0017] Figure 6 It is a diagram showing another operation of the variable focal length lens device according to the first embodiment.

[0018] Figure 7 It is a diagram showing another operation of the variable focal length lens device according to the first embodiment.

[0019] Figure 8 It is a diagram showing another operation of the variable focal length lens device according to the first embodiment.

[0020] Fig. 9 It is a diagram showing another operation of the variable focal length lens device according to the first embodiment.

[0021] FIG. 10 is a diagram showing a configuration of a variable focal length lens device according to Embodiment 2. FIG.

[0022] FIG. 11 is a diagram showing another configuration of the variable focal length lens device according to the second embodiment.

[0023] FIG. 12 is a diagram showing a configuration of a variable focal length lens device according to Embodiment 3. FIG.

[0024] FIG. 13 is a diagram showing another configuration of the variable focal length lens device according to the third embodiment. DETAILED DESCRIPTION

[0025] In order to explain the present invention in more detail below, the embodiment for carrying out the present invention will be described with reference to the accompanying drawings.

[0026] Implementation method 1.

[0027] Regarding the variable focal length lens devices 201A to 201D according to the first embodiment, referring to FIGS. 1 to 2 Fig. 9 Provide explanation.

[0028] Fig. 1 is a diagram showing a configuration of a variable focal length lens device 201A according to Embodiment 1. The variable focal length lens device 201A shown in Fig. 1 includes an optical system 101 and an imaging element 51. In the variable focal length lens device 201A, the side where the optical system 101 is arranged is the front side, and the side where the imaging element 51 is arranged is the rear side.

[0029] The optical system 101 includes a first variable focal length lens 11 , a second variable focal length lens 21 , a third variable focal length lens 31 , and a fixed focal length lens 41 .

[0030] The first variable focal length lens 11, the second variable focal length lens 21, the third variable focal length lens 31, and the fixed focal length lens 41 are arranged in order from the front side to the rear side. The first variable focal length lens 11, the second variable focal length lens 21, the third variable focal length lens 31, the fixed focal length lens 41, and the imaging element 51 are arranged on the same axis, that is, on the same optical axis.

[0031] The first variable focal length lens 11, the second variable focal length lens 21, and the third variable focal length lens 31 use liquid as the medium of the lens, and the shape of the liquid is electrically controlled, thereby forming a liquid lens in which the curvature radius of the curved surface of the lens surface changes. As a result, the focal length of the variable focal length lenses 11, 21, and 31 can be changed.

[0032] Specifically, the focal length variable lens 11, 21, 31 encapsulates liquid in a stretchable resin film, and a part of the liquid is pressed into the lens by a piezoelectric actuator, thereby changing the pressure of the liquid. As a result, the radius of curvature of the curved surface that becomes the lens surface of the focal length variable lens 11, 21, 31 changes, so the focal length can be changed. In addition, the focal length variable lens 11, 21, 31 can use electrowetting. In this case, the focal length variable lens 11, 21, 31 applies a voltage between an electrode with low wettability and a droplet thereon, thereby changing the contact angle of the droplet. As a result, the focal length of the focal length variable lens 11, 21, 31 can be changed.

[0033] On the other hand, the focal length of the fixed-focus lens 41 is constant because the radius of curvature of the curved surface of the lens surface does not change, for example. The fixed-focus lens 41 is made of glass or the like, for example.

[0034] The first variable focal length lens 11 , the second variable focal length lens 21 , the third variable focal length lens 31 , and the fixed focal length lens 41 are convex lenses.

[0035] The first variable focal length lens 11 has a first focal length f1. The front surface of the first variable focal length lens 11 is a plane, and the rear surface thereof is a convex curved surface. The second variable focal length lens 21 has a second focal length f2. The front surface of the second variable focal length lens 21 is a convex curved surface, and the rear surface thereof is a plane. The third variable focal length lens 31 has a third focal length f3. The front surface of the third variable focal length lens 31 is a plane, and the rear surface thereof is a convex curved surface. The fixed focal length lens 41 has a fourth focal length f4. The front surface of the fixed focal length lens 41 is a convex curved surface, and the rear surface thereof is a plane.

[0036] The inter-lens distance d between the second focal length variable lens 21 and the third focal length variable lens 31 is defined by the following equation (1).

[0037] d=f2+f3 · · · (1)

[0038] A first conjugate point 1 is set in front of the first variable focal length lens 11. The first conjugate point 1 is separated from the first variable focal length lens 11 forward by a first focal length f1. The first conjugate point 1 is a point where an object to be photographed is arranged, and is a focal position. A second conjugate point 2 is set behind the fixed focal length lens 41. The second conjugate point 2 is separated from the fixed focal length lens 41 backward by a fourth focal length f4. The second conjugate point 2 is a point where an imaging element 51 is arranged.

[0039] A third conjugate point 3 is set behind the second variable focal length lens 21. The third conjugate point 3 is arranged to be separated from the second variable focal length lens 21 by the second focal length f2 to the rear. In addition, it can be seen from formula (1) that the third conjugate point 3 is also a point separated from the third variable focal length lens 31 by the third focal length f3 to the front. At this time, the second variable focal length lens 21 and the third variable focal length lens 31 are configured to have positive focal lengths f2 and f3. Therefore, the third conjugate point 3 is arranged between the second variable focal length lens 21 and the third variable focal length lens 31.

[0040] In the variable focal length lens device 201A, an object arranged at the first conjugate point 1 is imaged by the optical system 101 on the imaging element 51 arranged at the second conjugate point 2 .

[0041] The first variable focal length lens 11 and the second variable focal length lens 21 constitute a first partial optical system 111 in the relationship between the first conjugate point 1 and the third conjugate point 3. The first partial optical system 111 constitutes an infinite conjugate system (see Figure 1B In addition, the third variable focal length lens 31 and the fixed focal length lens 41 constitute a second partial optical system 121 in the relationship between the third conjugate point 3 and the second conjugate point 2, and the second partial optical system 121 constitutes an infinite conjugate system (refer to Figure 1B ).

[0042] Here, the definition of positive and negative in the focal length variable lens device 201A is described. The inter-lens distance d is always a positive value. The focal lengths f1 to f4 are positive values ​​in the case of a convex lens and negative values ​​in the case of a concave lens.

[0043] As a method of measuring the position of a reference point with a predetermined position as the reference point, when the distance is separated by a positive focal length from the reference point toward the front, the position is defined as being located in front of the reference point. In addition, when the distance is separated by a negative focal length from the reference point toward the front, the position is defined as being located behind the reference point. In addition, when the distance is separated by a positive focal length from the reference point toward the rear, the position is defined as being located behind the reference point. Furthermore, when the distance is separated by a negative focal length from the reference point toward the rear, the position is defined as being located in front of the reference point.

[0044] The magnification of the entire optical system 101 is defined as a negative value in the case of an inverted image and a positive value in the case of an erected image. In addition, the magnification of the telephoto system composed of the second focal length variable lens 21 and the third focal length variable lens 31 is defined as a negative magnification when f3 / f2>0 and a positive magnification when f3 / f2<0.

[0045] FIG2 is a diagram showing the structure of a focal length variable lens device 201B according to Embodiment 1. The focal length variable lens device 201B shown in FIG2 differs from the focal length variable lens device 201A in the method of setting the second focal length f2 and the third focal length f3. The focal length variable lens device 201B includes an optical system 102 and an imaging element 51.

[0046] The optical system 102 includes a first variable focal length lens 11, a second variable focal length lens 22, a third variable focal length lens 32, and a fixed focal length lens 41. The first variable focal length lens 11, the second variable focal length lens 22, the third variable focal length lens 32, and the fixed focal length lens 41 are arranged in order from the front side toward the rear side. The first variable focal length lens 11, the second variable focal length lens 22, the third variable focal length lens 32, and the fixed focal length lens 41 are arranged on the same optical axis.

[0047] The second variable focal length lens 22 is a convex lens. The front surface of the second variable focal length lens 22 is a convex curved surface, and the rear surface thereof is a flat surface. The third variable focal length lens 32 is a concave lens. The front surface of the third variable focal length lens 32 is a flat surface, and the rear surface thereof is a concave curved surface.

[0048] The second variable focal length lens 22 has a positive second focal length f2. The third variable focal length lens 32 has a negative third focal length f3. When these focal lengths f2 and f3 satisfy equation (1), the third conjugate point 3 is arranged behind the third variable focal length lens 32 as the entire device. In other words, the third conjugate point 3 is arranged with the third variable focal length lens 32 as a reference, and is separated from the third variable focal length lens 32 by the third focal length f3 toward the front.

[0049] The first variable focal length lens 11 and the second variable focal length lens 22 constitute a first partial optical system 112 in the relationship between the first conjugate point 1 and the third conjugate point 3. The first partial optical system 112 constitutes an infinite conjugate system (see Figure 2B ). The third variable focal length lens 32 and the fixed focal length lens 41 constitute a second partial optical system 122 in the relationship between the third conjugate point 3 and the second conjugate point 2. The second partial optical system 122 constitutes an infinite conjugate system (refer to Figure 2B ).

[0050] FIG3 is a diagram showing the structure of a focal length variable lens device 201C according to Embodiment 1. The focal length variable lens device 201C shown in FIG3 differs from the focal length variable lens devices 201A and 201B in the method of setting the second focal length f2 and the third focal length f3. The focal length variable lens device 201C includes an optical system 103 and an imaging element 51.

[0051] The optical system 103 includes a first variable focal length lens 11, a second variable focal length lens 23, a third variable focal length lens 33, and a fixed focal length lens 41. The first variable focal length lens 11, the second variable focal length lens 23, the third variable focal length lens 33, and the fixed focal length lens 41 are arranged in order from the front side toward the rear side. The first variable focal length lens 11, the second variable focal length lens 23, the third variable focal length lens 33, and the fixed focal length lens 41 are arranged on the same optical axis.

[0052] The second variable focal length lens 23 is a concave lens. The front surface of the second variable focal length lens 23 is a concave curved surface, and the rear surface thereof is a flat surface. The third variable focal length lens 33 is a convex lens. The front surface of the third variable focal length lens 33 is a flat surface, and the rear surface thereof is a convex curved surface.

[0053] The second variable focal length lens 23 has a negative second focal length f2. The third variable focal length lens 33 has a positive third focal length f3. When these focal lengths f2 and f3 satisfy equation (1), the third conjugate point 3 is arranged as a whole behind the second variable focal length lens 23. In other words, the third conjugate point 3 is arranged with the second variable focal length lens 23 as a reference and separated from the second variable focal length lens 23 to the rear by the second focal length f2.

[0054] The first variable focal length lens 11 and the second variable focal length lens 23 constitute a first partial optical system 113 in the relationship between the first conjugate point 1 and the third conjugate point 3. The first partial optical system 113 constitutes an infinite conjugate system (see Figure 3B ). The third variable focal length lens 33 and the fixed focal length lens 41 constitute a second partial optical system 123 in the relationship between the third conjugate point 3 and the second conjugate point 2. The second partial optical system 123 constitutes an infinite conjugate system (refer to Figure 3B ).

[0055] FIG4 is a diagram showing the structure of a focal length variable lens device 201D according to Embodiment 1. The focal length variable lens device 201D shown in FIG4 differs from the focal length variable lens devices 201A to 201C in the method of setting the second focal length f2 and the third focal length f3. The focal length variable lens device 201D includes an optical system 104 and an imaging element 51.

[0056] The optical system 104 includes a first variable focal length lens 11, a second variable focal length lens 24, a third variable focal length lens 34, and a fixed focal length lens 41. The first variable focal length lens 11, the second variable focal length lens 24, the third variable focal length lens 34, and the fixed focal length lens 41 are arranged in order from the front side toward the rear side. The first variable focal length lens 11, the second variable focal length lens 24, the third variable focal length lens 34, and the fixed focal length lens 41 are arranged on the same optical axis.

[0057] The second variable focal length lens 24 and the third variable focal length lens 34 are flat plane lenses. The front and rear surfaces of the second variable focal length lens 24 are planes. The front and rear surfaces of the third variable focal length lens 34 are planes.

[0058] The second variable focal length lens 24 has a second focal length f2 that is a negative infinite value. The third variable focal length lens 34 has a third focal length f3 that is a positive infinite value. These focal lengths f2 and f3 substantially satisfy equation (1), and the third conjugate point 3 is arranged infinitely in front of the second variable focal length lens 24 as the entire device. In other words, the third conjugate point 3 is arranged with the second variable focal length lens 24 as a reference, and is separated from the second variable focal length lens 24 to the rear by the second focal length f2. In the variable focal length lens device 201D, the focal lengths f2 and f3 are infinite, so the second variable focal length lens 24 and the third variable focal length lens 34 function as parallel flat plates whose front and rear surfaces are parallel.

[0059] The first variable focal length lens 11 and the second variable focal length lens 24 constitute a first partial optical system 114 in the relationship between the first conjugate point 1 and the third conjugate point 3. The first partial optical system 114 constitutes an infinite conjugate system (see Figure 4B ). The third variable focal length lens 34 and the fixed focal length lens 41 constitute a second partial optical system 124 in the relationship between the third conjugate point 3 and the second conjugate point 2, and the second partial optical system 124 constitutes an infinite conjugate system.

[0060] Although not shown in the figure, the optical system 104 may be configured such that the second focal length variable lens 24 has a second focal length f2 of a positive infinite value, and the third focal length variable lens 34 has a third focal length f3 of a negative infinite value. In this case, the third conjugate point 3 is arranged infinitely behind the third focal length variable lens 34 as the entire device. In other words, the third conjugate point 3 is arranged with the third focal length variable lens 34 as a reference, and is separated from the third focal length variable lens 34 by the third focal length f3 toward the front.

[0061] In addition, the variable focal length lens devices 201A to 201D are devices for measuring the image of an object, and include a general image processing device and an illumination device. In the case where the variable focal length lens devices 201A to 201D include an illumination device, it is considered that the illumination device shares a part of the optical system 101 to 104, or a structure that does not share. In addition, in the case where the illumination device shares a part of the optical system 101 to 104, it is considered that a spectrometer is arranged between the first variable focal length lens 11 and the second variable focal length lens 21 to 24 to combine the light of each other on the same axis, and a spectrometer is arranged between the first variable focal length lens 11 and the second variable focal length lens 21 to 24 to combine the light of each other on the same axis, etc.

[0062] When a liquid lens is used as the variable focal length lens, a power source and a control unit (not shown) such as a driver substrate for driving the liquid lens are included.

[0063] Next, the operation of the variable focal length lens device 201A will be representatively described with reference to Fig. 1. The variable focal length lens device 201A can arbitrarily change the magnification and the focal position.

[0064] First, a description will be given of a case where the variable focal length lens device 201A adjusts the focal position.

[0065] In the variable focal length lens device 201A, the first variable focal length lens 11 adjusts the first focal length f1 so that the distance between the first variable focal length lens 11 and the object to be measured coincides with the first focal length f1. As described above, if they coincide, the focus position adjustment of the variable focal length lens device 201A is completed.

[0066] Next, a case where the variable focal length lens device 201A changes the magnification will be described.

[0067] The second focal length f2 and the third focal length f3 are limited by the inter-lens distance d as shown in formula (1). In contrast, the formula (2) shown below is a formula for calculating the focal length of a commonly known synthetic lens. When formula (1) is satisfied, the focal length of the synthetic lens becomes infinite and is not defined in formula (2).

[0068] f*=f2×f3 / (f2+f3-d) · · · (2)

[0069] Therefore, the condition shown in the formula (1) indicates that it is an afocal system that enlarges or reduces the light beam. At this time, the magnification m related to the optical system 101 is obtained using the formula (3) shown below, for example.

[0070] m=f2 / f1×f4 / f3 (3)

[0071] Here, for the sake of convenience, the afocal system magnification m* is defined by the following equation (4) in distinction from the magnification m of the optical system 101 .

[0072] m*=f3 / f2 (4)

[0073] Figure 5 2 is a diagram showing the operation of the telephoto system by the second variable focal length lens 21 and the third variable focal length lens 31. Figure 5 Three actions are shown as examples.

[0074] In each operating state, the second variable focal length lens 21 and the third variable focal length lens 31 satisfy equation (1) while being adjusted to different focal lengths. The variable focal length lens device 201A changes the position of the third conjugate point 3 by different operating conditions, for example, having third conjugate points 3, 3', 3".

[0075] When the focal length variable lens device 201A has the third conjugate point 3, the afocal system magnification m* is 2. Therefore, the ratio of the light beam in front of the second focal length variable lens 21 to the light beam behind the third focal length variable lens 31 is doubled.

[0076] When the focal length variable lens device 201A has the third conjugate point 3', the telephoto system magnification m* is 1. Therefore, the ratio of the light beam in front of the second focal length variable lens 21 to the light beam behind the third focal length variable lens 31 is 1.

[0077] When the focal length variable lens device 201A has the third conjugate point 3", the telephoto system magnification m* is "1 / 2". Therefore, the ratio of the light beam in front of the second focal length variable lens 21 and the light beam behind the third focal length variable lens 31 becomes 1 / 2 times.

[0078] Figure 6 2 is a diagram showing the operation of the telephoto system by the second variable focal length lens 22 and the third variable focal length lens 32. Figure 6 Three actions are shown as examples.

[0079] In each operation state, the second variable focal length lens 22 and the third variable focal length lens 32 satisfy equation (1) while being adjusted to different focal lengths. The variable focal length lens device 201B changes the position of the third conjugate point 3 by different operation conditions, for example, having third conjugate points 3, 3', 3".

[0080] When the focal length variable lens device 201B has the third conjugate point 3, the afocal system magnification m* is 1 / 3. Therefore, the ratio of the light beam in front of the second focal length variable lens 22 to the light beam behind the third focal length variable lens 32 is 1 / 3.

[0081] When the focal length variable lens device 201B has the third conjugate point 3', the telephoto system magnification m* is 1 / 2. Therefore, the ratio of the light beam in front of the second focal length variable lens 21 to the light beam behind the third focal length variable lens 31 is 1 / 2.

[0082] When the variable focal length lens device 201B has the third conjugate point 3", the telephoto system magnification m* is "3 / 5". Therefore, the ratio of the light beam in front of the second variable focal length lens 21 and the light beam behind the third variable focal length lens 31 is 3 / 5 times.

[0083] Figure 7 2 is a diagram showing the operation of the telephoto system by the second variable focal length lens 23 and the third variable focal length lens 33. Figure 7 Three actions are shown as examples.

[0084] In each operating state, the second variable focal length lens 22 and the third variable focal length lens 32 satisfy equation (1) while being adjusted to different focal lengths. The variable focal length lens device 201C changes the position of the third conjugate point 3 by different operating conditions, for example, having third conjugate points 3, 3', 3".

[0085] When the focal length variable lens device 201C has the third conjugate point 3, the afocal system magnification m* is 3. Therefore, the ratio of the light beam in front of the second focal length variable lens 23 and the light beam behind the third focal length variable lens 33 is tripled.

[0086] When the focal length variable lens device 201C has the third conjugate point 3', the telephoto system magnification m* is 2. Therefore, the ratio of the light beam in front of the second focal length variable lens 23 and the light beam behind the third focal length variable lens 33 is doubled.

[0087] When the focal length variable lens device 201C has the third conjugate point 3", the telephoto system magnification m* is "5 / 3". Therefore, the ratio of the light beam in front of the second focal length variable lens 23 and the light beam behind the third focal length variable lens 33 is 5 / 3 times.

[0088] Therefore, in order to change the first focal length f1 and adjust the focal position in the variable focal length lens devices 201A to 201C, and to suppress the variation of the magnification m, it is known that the afocal system magnification m* must be adjusted.

[0089] When equations (2) and (3) are substituted into equation (4) and rearranged, the telephoto system magnification m* can be expressed by the following equation (5) using the magnification m of the optical system 101 , the first focal length f1 , and the fourth focal length f4 .

[0090] m*=f4 / (m×f1) · · · (5)

[0091] Furthermore, by rearranging the equations (1) and (3), the second focal length f2 can be expressed by the following equation (6), and the third focal length f3 can be expressed by the following equation (7).

[0092] f2=d×m×f1 / (m×f1+f4) · · · (6)

[0093] f3=d×f4 / (m×f1+f4) · · · (7)

[0094] Therefore, the object arranged at the first conjugate point 1 is corrected to an arbitrary optical system magnification by the second variable focal length lenses 21 to 23 and the third variable focal length lenses 31 to 33, and then imaged on the imaging element 51. In addition, if the first focal length f1 is changed and the position of the first conjugate point 1 is adjusted to a position different from the position where the object is arranged, the object is further corrected to an arbitrary optical system magnification by the second variable focal length lenses 21 to 23 and the third variable focal length lenses 31 to 33 in this state, and then imaged on the imaging element 51.

[0095] Here, in order to make the operation of the variable focal length lens devices 201A to 201C easier to understand, specific numerical values ​​are used for description.

[0096] For example, it is assumed that the magnification m is set to "1" and the focal position (first conjugate point 1) is changed between 50 mm and 150 mm. In addition, the inter-lens distance d between the second variable focal length lenses 21 to 23 and the third variable focal length lenses 31 to 33 is set to 200 mm.

[0097] Only the case where the first focal length f1 is 50 mm and 150 mm is used as a representative example. When the first focal length f1 is 50 mm, the second focal length f2 is 100 mm, the third focal length f3 is 100 mm, and the fourth focal length f4 is 50 mm. In addition, when the first focal length f1 is 150 mm, the second focal length f2 is 150 mm, the third focal length f3 is 50 mm, and the fourth focal length f4 is 50 mm. Moreover, in accordance with the change of the first focal length f1 from 50 mm to 150 mm, the second focal length f2 is adjusted from 100 mm to 150 mm according to formula (6). In addition, the third focal length f3 is adjusted from 100 mm to 50 mm according to formula (7).

[0098] Figure 8 1 and 2 are diagrams showing the operation of the telephoto system by the second variable focal length lenses 21 and 23 and the third variable focal length lenses 31 and 33 .

[0099] The magnification m of the optical systems 101 to 103 has positive and negative differences, so it can be seen that in equations (5), (6), and (7), there are two operation modes with the same absolute value of the magnification m. Figure 5 , 6 The reduction conditions for each ratio shown, or Figure 5 , 7 The two operation modes correspond to the positive and negative differences of the telephoto system magnification m*, which have the same absolute value.

[0100] Figure 8 is an example of two action modes when the absolute value of the telephoto system magnification m* is 2. In the action mode in which the telephoto system magnification m* is 2, the second focal length variable lens 23 and the third focal length variable lens 33 satisfy equations (1) and (4). On the other hand, in the action mode in which the telephoto system magnification m* is -2, the second focal length variable lens 21 and the third focal length variable lens 31 satisfy equations (1) and (4). In the above two action modes, the position of the third conjugate point 3 changes, and each of the third conjugate points 3 after the change is illustrated as the third conjugate point 3, 3'. In switching between the two action modes, the sign of the optical system magnification is reversed, so there is an effect of freely reversing the acquired captured image.

[0101] Furthermore, a description will be given of a case where the above two operation modes are particularly suitable when a variable focal length lens serving as a liquid lens is employed.

[0102] It is reported that in the liquid lens, the deterioration of the characteristics of the posture dependence caused by gravity or the like becomes larger or smaller. At this time, in the optical configuration of the plane in which the optical axis is arranged perpendicularly to the direction of gravity, the aberration characteristics are sometimes different between the upper side of the lens (the side opposite to the ground) and the lower side of the lens (the ground side). The asymmetric aberration centered on the optical axis as described above is difficult to correct, but by effectively using the above two action modes, it is possible to perform digital correction for the asymmetric aberration.

[0103] That is, when the telephoto system magnification m* is positive, the light passing through the lower side of the second variable focal length lenses 21 to 23 will pass through the lower side of the third variable focal length lenses 31 to 33. At this time, the aberration caused by the posture will be equally affected by the two variable focal length lenses. In contrast, when the telephoto system magnification m* is negative, the light passing through the lower side of the second variable focal length lenses 21 to 23 will pass through the upper side of the third variable focal length lenses 31 to 33. At this time, the aberration caused by the posture is averaged by the two variable focal length lenses. Moreover, based on the difference between the characteristics of the captured image when the telephoto system magnification m* is positive and the characteristics of the captured image when the telephoto system magnification m* is negative, the aberration caused by the posture is expressed as a difference. Therefore, the above difference is digitally image corrected, thereby suppressing the aberration caused by the posture.

[0104] Fig. 9 2 is a diagram showing the operation of the telephoto system by the second variable focal length lenses 21 and 24 and the third variable focal length lenses 31 and 34. Fig. 9 yes Figure 8 The special example of two operation modes in which the absolute value of the magnification m is the same is an example of two operation modes in a case where the absolute value of the magnification m is 1.

[0105] In the action mode in which the telephoto system magnification m* is 1, the second variable focal length lens 24 and the third variable focal length lens 34 both become parallel plates, and they roughly satisfy equations (1) and (4). In the action mode in which the telephoto system magnification m* is -1, the second variable focal length lens 21 and the third variable focal length lens 31 satisfy equations (1) and (4). In the above two action modes, the position of the third conjugate point 3 changes, and each of the changed third conjugate points 3 is illustrated as the third conjugate point 3, 3'. In the switching of the two action modes, the sign of the optical system magnification is reversed, so there is an effect of freely reversing the acquired captured image.

[0106] Furthermore, since an infinite focal length is strictly impossible in manufacturing, in the actual operation of a variable focal length lens, the condition where the reciprocal of the focal length, that is, the refractive power becomes 0 within the variable range can obviously be regarded as an infinite focal length.

[0107] As described above, the variable focal length lens device 201A to 201D according to the first embodiment comprises: a first variable focal length lens 11 having a first focal length f1; second variable focal length lenses 21 to 24, which are arranged behind the first variable focal length lens 11 and have a second focal length f2; third variable focal length lenses 31 to 34, which are arranged behind the second variable focal length lenses 21 to 24 and have a third focal length f3; a fixed focal length lens 41, which is arranged behind the third variable focal length lenses 31 to 34 and has a fourth focal length f4; a first conjugate point 1, which is arranged at a position separated from the first variable focal length lens 11 by the first focal length f1 to the front and becomes a focal position; and a second conjugate point 21 to 24, which is arranged behind the second variable focal length lenses 21 to 24 and have a third focal length f3. 2, which is arranged at a position separated from the fixed focal length lens 41 by the fourth focal length f4 in the rear, and the imaging element 51 is provided; and the third conjugate point 3, which is arranged at a position separated from the second variable focal length lenses 21 to 24 by the second focal length f2 in the rear, and separated from the third variable focal length lenses 31 to 34 by the third focal length f3 in the front, the first partial optical system 111 to 114 composed of the first variable focal length lens 11 and the second variable focal length lenses 21 to 24 is an infinite conjugate system with respect to the first conjugate point 1, and the second partial optical system 121 to 124 composed of the third variable focal length lenses 31 to 34 and the fixed focal length lens 41 is an infinite conjugate system with respect to the third conjugate point 3. Therefore, the variable focal length lens devices 201A to 201D can arbitrarily change the magnification and focus position suitable for the variable focal length lenses.

[0108] In addition, as the principle of the liquid lens as a specific example of the variable focal length lens, the use of a piezoelectric actuator and the use of electrowetting are cited, but even if it is based on other principles, it is obvious that the effect of the invention can be obtained. In addition, even if it is a lens with a variable focal length function other than a liquid lens, the effect of the invention can be obtained in the same way.

[0109] The liquid lens cited as the variable focal length lens may have an optical function like a solid lens such as glass or a cover glass in addition to a liquid portion having a lens function.

[0110] Focus Adjustment Mechanism of Variable-Focus Lens When a liquid lens is used as the variable-focus lens, for example, the liquid lens is controlled by an electrical physical quantity such as a voltage applied to the liquid lens.

[0111] As the shapes of the variable focal length lens and the fixed focal length lens, plano-convex, plano-concave, or flat plate are cited, but each may not have a strictly planar portion. Even if the so-called optimally shaped lens, such as a meniscus lens suitable for an infinite conjugate system, has a gentle curvature on the planar side, the effect of the invention can obviously be obtained.

[0112] In the first embodiment, the case where the telephoto system has three operating points is described, but it is obviously not limited to 3. For example, when a liquid lens is used as a variable focal length lens, the number of possible operating points is determined by the range of voltage applied to the liquid lens and the resolution.

[0113] Implementation method 2.

[0114] The variable focal length lens devices 202A and 202B according to Embodiment 2 will be described using Fig. 10 and Fig. 11. Configurations having the same functions as those described in Embodiment 1 are denoted by the same reference numerals and their description will be omitted.

[0115] Fig. 10 is a diagram showing the structure of a variable focal length lens device 202A according to Embodiment 2. The variable focal length lens device 202A shown in Fig. 10 is configured such that an optical fiber 61 is arranged instead of an imaging element 51 at the position of a third conjugate point 3 formed by an image of the first conjugate point 1.

[0116] Specifically, the variable focal length lens device 202A includes a light receiving element 52, an optical fiber 61, an illumination light source 62, and a circulator 63 instead of the imaging element 51 of the variable focal length lens device 201A. The optical fiber 61 constitutes a light guide unit, and the circulator 63 constitutes an optical splitter.

[0117] One end of the optical fiber 61 forms the third conjugate point 3. The other end of the optical fiber 61 is connected to the circulator 63. The optical fiber 61 is, for example, a single optical fiber or an optical fiber obtained by bundling a plurality of optical fibers. The circulator 63 has two ports. One port is optically connected to the illumination light source 62. The other port is optically connected to the light receiving element 52. As an optical connection method, for example, a space optical system and a fiber optical system are used.

[0118] Next, the operation of the variable focal length lens device 202A will be described. The operation of the optical system 101 of the variable focal length lens device 202A adjusting the focal position is the same as the operation of the optical system 101 of the variable focal length lens device 201A adjusting the focal position. In addition, the operation of the optical system 101 of the variable focal length lens device 202A changing the magnification m is the same as the operation of the optical system 101 of the variable focal length lens device 201A changing the magnification m.

[0119] The illumination light emitted from the illumination light source 62 passes through the optical fiber 61 and the optical system 101 in sequence by the action of the circulator 63. Then, the illumination light passing through the optical system 101 irradiates the object arranged at the first conjugate point 1. On the other hand, the illumination light reflected and scattered by the object passes through the optical system 101 and the optical fiber 61 in sequence. Then, the illumination light passing through the optical fiber 61 is incident on the light receiving element 52 by the action of the circulator 63. As a result, the variable focal length lens device 202A can obtain a captured image of the object from the light receiving element 52 that receives the illumination light.

[0120] Therefore, the object arranged at the first conjugate point 1 is imaged on the imaging element 51 after being corrected to an arbitrary optical system magnification by the second variable focal length lens 21 and the third variable focal length lens 31. In addition, if the first focal length f1 is changed and the position of the first conjugate point 1 is adjusted to a position different from the position where the object is arranged, the object is further corrected to an arbitrary optical system magnification by the second variable focal length lens 21 and the third variable focal length lens 31 in this state and then imaged on the imaging element 51.

[0121] In addition, the focal length variable lens device 202A shown in FIG10 has an optical system 101, but it may be replaced with an optical system 103 as shown in FIG11. FIG11 is a diagram showing the structure of a focal length variable lens device 202B involved in Embodiment 2. The focal length variable lens device 202B has an optical system 103, a light receiving element 52, an optical fiber 61, an illumination light source 62, and a circulator 63. In addition, the focal length variable lens device 202A has an optical system 101, but it may be replaced with an optical system 102 shown in FIG2 or an optical system 104 shown in FIG4.

[0122] As described above, the focal length variable lens device 202A, 202B involved in the second embodiment comprises: a first focal length variable lens 11, which has a first focal length f1; second focal length variable lenses 21, 23, which are arranged behind the first focal length variable lens 11 and have a second focal length f2; third focal length variable lenses 31, 33, which are arranged behind the second focal length variable lenses 21, 23 and have a third focal length f3; a focal length fixed lens 41, which is arranged behind the third focal length variable lenses 31, 33 and has a fourth focal length f4; a first conjugate point 1, which is arranged at a position separated from the first focal length variable lens 11 by the first focal length f1 to the front and becomes a focal position; and a second conjugate point 21, 23, which is arranged behind the second focal length variable lens 21, 23 and has a third focal length f3. The optical fiber 61 is provided at the point 2, which is arranged at a position separated from the fixed focal length lens 41 by the fourth focal length f4 in the rear direction, and the third conjugate point 3, which is arranged at a position separated from the second variable focal length lenses 21, 23 by the second focal length f2 in the rear direction, and separated from the third variable focal length lenses 31, 33 by the third focal length f3 in the front direction, the first partial optical system 111, 113 composed of the first variable focal length lens 11 and the second variable focal length lenses 21, 23 is an infinite conjugate system with respect to the first conjugate point 1, and the second partial optical system 121, 123 composed of the third variable focal length lenses 31, 33 and the fixed focal length lens 41 is an infinite conjugate system with respect to the third conjugate point 3. Therefore, the variable focal length lens devices 202A, 202B can arbitrarily change the magnification and focal position suitable for the variable focal length lenses.

[0123] Implementation method 3.

[0124] The variable focal length lens devices 203A and 203B according to Embodiment 3 will be described using Fig. 12 and Fig. 13. Configurations having the same functions as those described in Embodiment 1 are denoted by the same reference numerals and their description will be omitted.

[0125] FIG12 is a diagram showing the structure of a focal length variable lens device 203A according to Embodiment 3. The focal length variable lens device 203A shown in FIG12 is configured to obtain an interference signal of light by combining the illumination light emitted from the illumination light source 62 into a reference optical path 71 and a signal optical path 72a through the light receiving element 53 after the illumination light is split. That is, the focal length variable lens device 203A is configured to add a reference optical path 71 and signal optical paths 72a, 72b to the above-mentioned focal length variable lens device 202A.

[0126] The reference optical path 71 optically connects the illumination light source 62 and the light receiving element 53. The signal optical path 72a optically connects the illumination light source 62 and one port of the circulator 63. The signal optical path 72b optically connects the other port of the circulator 63 and the light receiving element 53.

[0127] Next, the operation of the variable focal length lens device 203A will be described. The operation of the optical system 101 of the variable focal length lens device 203A adjusting the focal position is the same as the operation of the optical system 101 of the variable focal length lens device 201A adjusting the focal position. In addition, the operation of the optical system 101 of the variable focal length lens device 203A changing the magnification m is the same as the operation of the optical system 101 of the variable focal length lens device 201A changing the magnification m.

[0128] The illumination light emitted from the illumination light source 62 is split into a reference optical path 71 and a signal optical path 72a. The illumination light split into the reference optical path 71 is incident on the light receiving element 53 through the reference optical path 71. On the other hand, the illumination light split into the signal optical path 72a is sequentially passed through the optical fiber 61 and the optical system 101 by the action of the circulator 63. Then, the illumination light passing through the optical system 101 irradiates the object arranged at the first conjugate point 1. On the other hand, the illumination light reflected and scattered by the object is sequentially passed through the optical system 101 and the optical fiber 61. Then, the illumination light passing through the optical fiber 61 is incident on the light receiving element 52 through the signal optical path 72b by the action of the circulator 63. At this time, the illumination light incident on the light receiving element 53 from the signal optical path 72b interferes with the illumination light incident on the light receiving element 53 from the reference optical path 71. As a result, the variable focal length lens device 203A can obtain interference information of the illumination light from the light receiving element 52 that receives the two illumination lights.

[0129] In addition, the focal length variable lens device 203A shown in FIG12 has the optical system 101, but it can also replace the optical system 101 with an optical system 103 as shown in FIG13. FIG13 is a diagram showing the structure of the focal length variable lens device 203B involved in the third embodiment. The focal length variable lens device 203B has the optical system 103, the light receiving element 53, the optical fiber 61, the illumination light source 62, the circulator 63, the reference optical path 71, and the signal optical paths 72a and 72b. In addition, the focal length variable lens device 203A has the optical system 101, but it can also replace the optical system 101 with the optical system 102 shown in FIG2 or the optical system 104 shown in FIG4.

[0130] In addition, the variable focal length lens devices 203A and 203B include a general interference information processing device required for a heterodyne detection system or the like.

[0131] When the variable focal length lens devices 203A and 203B are used as interference information processing devices, the variable focal length lens devices 203A and 203B use a wavelength variable light source instead of the illumination light source 62, and the wavelength is temporally scanned, so that the distance measurement of the FMCW method can be performed based on the wavelength difference when the wavelengths are combined. As described above, the variable focal length lens devices 203A and 203B used as interference information processing devices can measure the distance based on the wavelength difference, so that interference information can be obtained even from an object that is arranged offset relative to the first conjugate point 1.

[0132] Furthermore, the present invention can freely combine the various embodiments within the scope of the disclosure, can modify arbitrary components of the various embodiments, or can omit arbitrary components in the various embodiments.

[0133] Industrial Applicability

[0134] The variable focal length lens device according to the present invention is suitable for use in a variable focal length lens device or the like that can arbitrarily change the magnification and focal position suitable for the variable focal length lens.

[0135] Description of the label

[0136] 1 first conjugate point, 2 second conjugate point, 3 third conjugate point, 11 first variable focal length lens, 21-24 second variable focal length lens, 31-34 third variable focal length lens, 41 fixed focal length lens, 51 imaging element, 52, 53 light receiving element, 61 optical fiber, 62 light source for illumination, 63 circulator, 71 reference optical path, 72a, 72b signal optical path, 101-104 optical system, 111-114 first partial optical system, 121-124 second partial optical system, 201A-201D, 202A, 202B, 203A, 203B variable focal length lens device, f1 first focal length, f2 second focal length, f3 third focal length, f4 fourth focal length, d distance between lenses.

Claims

1. A variable focal length lens device, characterized in that: have: a first variable focal length lens having a first focal length; a second variable focal length lens, which is disposed behind the first variable focal length lens and has a second focal length; a third variable focal length lens, which is disposed behind the second variable focal length lens and has a third focal length; A fixed focal length lens, which is arranged behind the third variable focal length lens and has a fourth focal length; a first conjugate point, which is arranged at a position separated from the first variable focal length lens by the first focal length in the front direction and becomes a focal position; A second conjugate point is arranged at a position separated from the fixed focal length lens by the fourth focal length in the rear, where a photographing element or a light guide unit is arranged; as well as a third conjugate point, which is arranged at a position separated from the second focal length variable lens rearward by the second focal length and separated from the third focal length variable lens forward by a third focal length, The first partial optical system composed of the first variable focal length lens and the second variable focal length lens is an infinite conjugate system with respect to the first conjugate point. The second partial optical system composed of the third variable focal length lens and the fixed focal length lens is an infinite conjugate system with respect to the third conjugate point.

2. The variable focal length lens device according to claim 1, characterized in that: have: An optical splitter, which is arranged at a subsequent stage of the light guiding unit; a light source for illumination, connected to one end of the optical splitter; and The light receiving element is connected to the other end of the optical splitter.

3. The variable focal length lens device according to claim 2, characterized in that: A reference optical path is provided for transmitting the illumination light split from the illumination light source to the light receiving element.

4. The variable focal length lens device according to claim 3, characterized in that: The illumination light source is a wavelength-variable light source.

Images