Microscope and Method

Abstract

This invention provides a medical microscope that allows the observer to view the observed object in a natural, three-dimensional manner. [Solution] The medical microscope 10 includes an objective optical system 122, an image sensor 122, a display element 132, and an eyepiece optical system 131 that guides the image light from the display element 132 to the observer. The objective optical system 122 includes an objective optical system 122a and an objective optical system 122b, and the objective optical system 122a and the objective optical system 122b are arranged such that a convergence angle is formed by the optical axis of the objective optical system 122a and the optical axis of the objective optical system 122b. The horizontal or vertical number of pixels of the display element 132 is 2000 or more and 4000 or less. The field of view of the eyepiece optical system 131 is 35 degrees or more and 60 degrees or less.

Description

Technical Field

[0001] The present disclosure relates to a medical microscope used in medical treatment.

Background Art

[0002] Medical practitioners may use a medical microscope to observe a patient's treatment site. In recent years, a 3D digital microscope has been attracting attention as a medical microscope for observing a patient's treatment site, instead of an optical stereo microscope.

[0003] For example, Japanese Patent No. 6469292 (Patent Document 1) describes a system configured such that an observer can perform dental treatment while stereoscopically viewing a tooth image by displaying an image of a tooth captured by an image sensor provided in a microscope on a display unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When an optical stereo microscope is used, an observer can directly observe the actual treatment site through a lens. However, when a 3D digital microscope is used, an observer observes an image obtained by imaging the treatment site, rather than directly observing the treatment site through a lens. Therefore, the 3D digital microscope requires a device for stereoscopically viewing an image in a natural feeling as if directly observing the treatment site through a lens. However, a medical microscope with such a device has not been found.

[0006] The purpose of this disclosure is to provide a medical microscope that allows the observer to view the image of the object being observed in a natural-looking stereoscopic manner. [Means for solving the problem]

[0007] The medical microscope relating to this disclosure includes an objective optical system, an image sensor that captures an image of a subject formed through the objective optical system, a display element that displays the image acquired by the image sensor, and an eyepiece optical system that guides the image light from the display element to the observer. The objective optical system includes a first objective optical system and a second objective optical system. The image sensor includes a first image sensor corresponding to the first objective optical system and a second image sensor corresponding to the second objective optical system. The display element includes a first display element corresponding to the first image sensor and a second display element corresponding to the second image sensor. The eyepiece optical system includes a first eyepiece optical system corresponding to the first display element and a second eyepiece optical system corresponding to the second display element. The first and second objective optical systems are arranged such that a convergence angle is formed by the optical axis of the first objective optical system and the optical axis of the second objective optical system. The horizontal or vertical number of pixels of the display element is 2000 or more and 4000 or less. The field of view of the eyepiece optical system is 35 degrees or more and 60 degrees or less. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a medical microscope that allows the observer to view the image of the object being observed in a natural-looking stereoscopic manner. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing an example configuration of a microscope and a system using a microscope related to this embodiment. [Figure 2] This is a block diagram showing the detailed configuration of the microscope. [Figure 3] This is a schematic diagram illustrating the principle of stereoscopic vision using a microscope. [Figure 4]This diagram illustrates the difference between the microscope in this embodiment and Comparative Example 1. [Figure 5] This diagram shows the configuration of the eyepiece unit. [Figure 6] This diagram shows the relationship between the field of view and the number of pixels. [Figure 7] This is a conceptual diagram to explain the apparent distance to the screen in stereoscopic viewing. [Figure 8] This is a conceptual diagram to explain the principal ray angle. [Figure 9] This diagram illustrates the working distance from the objective unit to the subject. [Figure 10] This diagram illustrates the relationship between the convergence angle and the focus adjustment range. [Figure 11] This graph shows the relationship between the convergence angle and the focus adjustment range. [Figure 12] This is a diagram illustrating a variation. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described in detail with reference to the drawings. Parts identical or corresponding to those shown in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated.

[0011] <Overall Structure> Figure 1 is a schematic diagram showing an example of the configuration of a microscope 10 and a system using the microscope 10 according to this embodiment. Using Figure 1, an example of a system to which the microscope 10 according to this embodiment is applied will be explained. The microscope 10 is a medical microscope used for medical treatment. Here, dental treatment is given as an example of medical treatment. However, the microscope 10 according to this disclosure can be applied to medical treatment in other medical fields besides dentistry, such as surgery and dermatology.

[0012] FIG. 1 shows an example of a system including a microscope 10 and a chair unit 20. The microscope 10 and the chair unit 20 are communicably connected by a CAN (Controller Area Network). The microscope 10 is supported by an arm 302 rotatably attached to a pole 301. The microscope 10 is a digital stereo microscope. The microscope 10 has a function of three-dimensionally photographing a subject and allowing an observer to view a stereoscopic image of the subject. Note that the arm 302 may be attached to a support member extending from a ceiling or a wall.

[0013] The microscope 10 includes a pair of objective units 12, a pair of eyepiece units 13, a pair of handles 102, and a housing 101. In FIG. 1, the microscope 10 is illustrated from an angle at which only one of the pair of objective units 12, one of the pair of eyepiece units 13, and one of the pair of handles 102 are visible. For this reason, the other objective unit 12, the other eyepiece unit 13, and the other handle 102 do not appear in FIG. 1. The housing 101 is attached to the tip of the arm 302. The housing 101 houses the pair of objective units 12 and the pair of eyepiece units 13. The pair of handles 102 are provided on the housing 101.

[0014] The objective unit 12 includes an objective optical system such as an objective lens 1210, and the eyepiece unit includes an eyepiece optical system such as an eyepiece lens 1310. Among the objective units 12, the portion including the objective lens 1210 protrudes from the housing 101 and is directed toward the subject. Among the eyepiece units 13, the portion including the eyepiece lens 1310 protrudes from the housing 101 and is directed toward the pupil of the observer.

[0015] The microscope 10 images a pair of subject images captured by a pair of objective units 12 and generates a pair of images for stereoscopic viewing. The pair of objective units 12 function as an imaging device (camera). An observer observes the pair of images with both eyes through a pair of eyepiece units 13. At this time, a stereoscopic image of the subject is provided to the observer.

[0016] The observer is, for example, a surgeon. The subject is, for example, a patient. During dental treatment, the subject is the patient's oral cavity. The oral cavity includes teeth, periodontal tissues, tongue, and salivary glands. The surgeon holds the handle 102 and moves the microscope 10 to observe the oral cavity and finely adjust the observation range.

[0017] The chair unit 20 includes an examination chair 21, a foot controller 23, and a base 29. The patient receives treatment from the surgeon on the examination chair 21. A basin unit 27 is arranged around the examination chair 21. The chair unit 20 may include the basin unit 27. The basin unit 27 includes a cleaning unit 28. The cleaning unit 28 has a water faucet and a saliva ejector. The patient rinses the oral cavity using the cleaning unit 28. An instrument stand may be arranged around the examination chair 21. The instrument stand may have a storage section for storing a plurality of types of instruments such as cutting tools and medical instruments.

[0018] The examination chair 21 includes a seat 211, a backrest 212, and a headrest 213. The seat 211 is attached to the base 29. The base 29 has a mechanism for raising and lowering the seat 211. The backrest 212 is attached to the seat 211 so as to be tiltable with respect to the seat 211. The headrest 213 is attached to the backrest 212 so as to be tiltable with respect to the backrest 212.

[0019] The foot controller 23 has multiple pedals that accept foot input from the operator. These multiple pedals include a pedal that drives the base 29, a pedal that drives the backrest 212, and a pedal that drives the headrest 213. The operator changes the posture of the medical chair 21 to the appropriate position by pressing on the multiple pedals.

[0020] Figure 1 illustrates a position where the backrest 212 is nearly horizontal to the seat 211, and the headrest 213 is nearly horizontal to the backrest 212. The position of the medical chair 21 is determined by the height of the seat 211, the tilt angle of the backrest 212, and the tilt angle of the headrest 213.

[0021] <Hardware Configuration> Figure 2 is a block diagram showing the detailed configuration of the microscope 10. As shown in Figure 2, the microscope 10 comprises a pair of observation units 11a and 11b and a control device 14. Hereinafter, observation units 11a and 11b will be collectively referred to as "observation unit 11".

[0022] The observation unit 11 includes an objective unit 12 and an eyepiece unit 13. The control device 14 controls the objective unit 12 and the eyepiece unit 13.

[0023] The control device 14 includes a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). The CPU executes operating programs stored in ROM, etc. ROM stores programs and other data executed by the CPU. RAM serves as a workspace for the CPU when executing programs and temporarily stores programs and data used when executing programs. The control devices 14 and 24 may consist of at least one semiconductor integrated circuit such as a processor, at least one application-specific integrated circuit (ASIC), at least one DSP (Digital Signal Processor), at least one FPGA (Field Programmable Gate Array), and / or other circuits having arithmetic functions. The control device 14 may consist of processing circuitry.

[0024] Each of the pair of observation units 11 comprises an objective unit 12 and an eyepiece unit 13. Hereinafter, the objective unit 12 provided in observation unit 11a will be referred to as "objective unit 12a," and the objective unit 12 provided in observation unit 11b will be referred to as "objective unit 12b." Similarly, hereafter, the eyepiece unit 13 provided in observation unit 11a will be referred to as "eyepiece unit 13a," and the eyepiece unit 13 provided in observation unit 11b will be referred to as "eyepiece unit 13b."

[0025] In other words, "objective unit 12" is a collective term for "objective units 12a and 12b," and "eyepiece unit 13" is a collective term for "eyepiece units 13a and 13b."

[0026] The objective unit 12 includes an objective optical system 121 and an image sensor 122. The eyepiece unit 13 includes an eyepiece optical system 131 and a display element 132. Hereinafter, the objective optical system 121 provided in the objective unit 12a will be referred to as "objective optical system 121a", the objective optical system 121 provided in the objective unit 12b will be referred to as "objective optical system 121b", the image sensor 122 provided in the objective unit 12a will be referred to as "image sensor 122a", and the image sensor 122 provided in the objective unit 12b will be referred to as "image sensor 122b".

[0027] In other words, "objective optical system 121" is a collective term for "objective optical systems 121a and 121b," and "image sensor 122" is a collective term for "image sensors 122a and 122b."

[0028] Similarly, in the following, the eyepiece optical system 131 provided in the eyepiece unit 13a will be referred to as "eyepiece optical system 131a", the eyepiece optical system 131 provided in the eyepiece unit 13b will be referred to as "eyepiece optical system 131b", the display element 132 provided in the eyepiece unit 13a will be referred to as "display element 132a", and the display element 132 provided in the eyepiece unit 13b will be referred to as "display element 132b".

[0029] In other words, "eyepiece optical system 131" is a collective term for "eyepiece optical systems 131a and 131b," and "display element 132" is a collective term for "display elements 132a and 132b." The display element 132 displays the image acquired by the image sensor 122. The eyepiece optical system 131 guides the image light from the display element 132 to the observer.

[0030] The image sensor 122 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The shape of the imaging area of ​​the image sensor 122 is, for example, a square. However, the shape of the imaging area of ​​the image sensor 122 does not have to be a square; for example, it may be a rectangle other than a square. The display element 132 constitutes a flat panel display such as an LCD (Liquid Crystal Display) or an organic EL (Electroluminescence). The image sensor 122 captures the subject image formed through the objective optical system 121.

[0031] <Principle of Stereoscopic Vision> Figure 3 is a schematic diagram illustrating the principle of stereoscopic vision using the microscope 10. The principle of stereoscopic vision using the microscope 10 will be explained using Figure 3.

[0032] As shown in Figure 3, the pair of objective units 12a and 12b are positioned such that a convergence angle is formed at the intersection of the optical axes passing through the centers of the objective lenses 1210, 1210. The subject is located at the intersection of the optical axes. Figure 3 shows the oral cavity of a patient as an example of a subject. The pair of image sensors 122a and 122b capture the image of the subject captured by the objective lens 1210 and output the image signal to the control device 14. There is a positional shift between the image acquired by image sensor 122a and the image acquired by image sensor 122b, corresponding to the convergence angle. This positional shift corresponds to "parallax".

[0033] The control device 14 displays the image acquired by the image sensor 122a on the display element 132a (see Figure 2), and the image acquired by the image sensor 122b on the display element 132b (see Figure 2). As a result, a pair of images that produce parallax are displayed on the display elements 132a and 132b. The observer observes the pair of images through the pair of eyepiece units 13a and 13b shown in Figure 2. This allows the observer to view the subject in stereoscopic vision.

[0034] <Comparison of this embodiment with Comparative Example 1> Figure 4 is a diagram illustrating the difference between the microscope 10 according to this embodiment and Comparative Example 1. The microscope according to Comparative Example 1 is an optical stereo microscope 1000. The optical stereo microscope 1000 comprises a pair of objective units 1200, 1200 and a pair of eyepiece units 1300, 1300. The microscope 10 according to this embodiment comprises a pair of objective units 12, 12 and a pair of eyepiece units 13, 13.

[0035] Microscope 10 and optical stereo microscope 1000 are similar in that they both have a pair of objective units and a pair of eyepiece units. It goes without saying that each of the objective unit 12 (1200) and the eyepiece unit 13 (1300) includes an optical system, the optical system of objective unit 12 (1200) includes an objective lens, and the optical system of eyepiece unit 13 (1300) includes an eyepiece lens.

[0036] The optical stereo microscope 1000 delivers the image of the object being observed directly to the observer's eye via the optical path OP1 within the objective unit 1200 and the eyepiece unit 1300. Therefore, the observer can observe the object as it is, through the objective lens of the objective unit 1200 and the eyepiece lens of the eyepiece unit 1300.

[0037] In contrast, the microscope 10 captures an image of the object being observed, which enters the objective unit 12 via the optical path OP2, using the image sensor 122, and displays the image obtained from the capture on the display element 132 in the eyepiece unit 12. The observer observes the image delivered from the display element 132 via the optical path OP3. Thus, the microscope 10 is a "3D digital microscope".

[0038] In the case of a 3D digital microscope, the objective unit and eyepiece unit can be operated independently, which improves the flexibility of treatment positions.

[0039] Furthermore, with the optical stereo microscope 1000, there is a risk that the laser light used in dental treatment could directly enter the observer's eye when it enters the objective lens. In contrast, this risk does not exist with a 3D digital microscope. Thus, the 3D digital microscope has numerous advantages that the optical stereo microscope 1000 does not.

[0040] However, 3D digital microscopes face the challenge of how to allow the observer to view the object in a natural (as it is) three-dimensional manner through improvements in imaging and image presentation. In short, the challenge of a "3D digital microscope" is to allow the observer to view the image of the object in a natural three-dimensional manner. This challenge does not arise in Comparative Example 1, which provides the observer with an image of the object itself through a lens. In this embodiment, to solve this problem, we will explain more specific design values ​​required for a 3D digital microscope, using microscope 10 as an example.

[0041] <Eyepiece Unit Configuration> Figure 5 shows the configuration of the eyepiece unit 13. As shown in Figure 5, the eyepiece unit 13 comprises a display element 132 and an eyepiece optical system 131. The eyepiece optical system 131 includes an eyepiece lens 1310 and a field lens 1311. The observer looks through the eyepiece lens 1310 and observes the image displayed on the display element 132. The eyepiece unit 13 has an optical path OP3 formed therein to guide the image of the display element 132 to the observer's pupil.

[0042] The optical path OP3 contains an eyepiece lens 1310 and a field lens 1311. The field lens 1311 is positioned between the display element 132 and the eyepiece lens 1310. Thus, the eyepiece optical system 131 includes multiple lenses arranged in the direction of the optical path OR3 that guides image light from the display element 132 to the observer. Aberrations are corrected by the combination of the field lens 1311 and the eyepiece lens 1310.

[0043] If only one eyepiece 1310 is placed in the optical path OR3, the eyepiece 1310 functions like a magnifying glass. In this case, there is almost no distortion in the image at the center of the field of view, but at the periphery of the field of view, the image is distorted or blurred due to the effects of aberrations. Therefore, in this embodiment, multiple lenses are placed in the optical path OR3 to provide the observer with an image with minimal distortion across the entire field of view. In Figure 5, two lenses are shown as an example of multiple lenses. However, three or more lenses may be placed in the optical path OR3.

[0044] The display element 132 constitutes a screen for displaying images. Image light from the center of the screen passes through the center of the field lens 1311 and the center of the eyepiece lens 1310 and reaches the observer's pupil. Image light from the edges of the screen is refracted by the field lens 1311 and then reaches the observer's pupil via the eyepiece lens 1310. The observer perceives the screen on which the image is projected as extending over a field of view angle θv.

[0045] The field lens 1311 also contributes to reducing the size of the eyepiece 1310. If the field lens 1311 is not placed between the display element 132 and the eyepiece 1310, the size of the eyepiece 1310 needs to be large enough to allow light from one edge of the screen to the other. However, by placing the field lens 1311 between the display element 132 and the eyepiece 1310, the optical axis can be bent toward the center of the eyepiece 1310. As a result, the diameter of the eyepiece 1310 can be reduced.

[0046] <Design values ​​for eyepiece unit 13> The design values ​​for the eyepiece unit 13 are described below. As shown in Figure 5, the eye point AP of the eyepiece unit 13 is 10 mm (millimeters) or more, the field of view angle θv of the eyepiece optical system in the eyepiece unit 13 is 35 degrees (degrees) or more and 60 degrees or less, the diameter of the eyepiece lens 1310 is 60 mm or less, and the number of pixels of the display element 132 is 2000 or more and 4000 or less. Note that the design value for the number of pixels may be for horizontal pixels or for vertical pixels. For example, if the field of view is designed to be a perfect circle, the number of horizontal pixels and the number of vertical pixels are the same. In order to design the field of view to be a perfect circle, the designer needs to use an image sensor 122 that has a square imaging area. Note that if an image sensor 122 with an imaging area other than a square, such as a rectangle, is used, the field of view is a circle with a diameter equal to the vertical width.

[0047] The eye point AP is the distance from the observer-side lens surface of the eyepiece 1310 to the observer's pupil. Generally, if the eye point AP is short (for example, 5 mm), it does not affect the observation of an uncorrected observer. However, if the eye point AP is short, an observer wearing glasses will need to remove their glasses to look through the eyepiece 1310.

[0048] The design value of 10mm corresponds to approximately the distance from the eyeglasses to the observer's pupil. Therefore, by designing the eye point AP to be 10mm or more, the observer can easily look through the eyepiece 1310 while wearing eyeglasses. A more preferable design value for the eye point AP is between 17mm and 20mm.

[0049] Figure 6 shows the relationship between the field of view and the number of pixels. The relationship between the field of view θv and the number of pixels of the display element 132 will be explained in detail with reference to Figure 6. The field of view refers to the angle of the field of view that an observer can see when looking through the eyepiece 1310. If the field of view is too wide, the number of pixels per degree of field of view decreases, and the pixels become more prominent. For this reason, if the field of view is too wide, the observer will perceive the image as having low resolution. Conversely, if the field of view is too narrow, the observer will only be able to see a small portion of the object being observed, thus reducing the observer's work efficiency.

[0050] Here, we will explain the relationship between field of view and pixels in more detail using the unit "ppd (pixels per degree)". "ppd" refers to the number of pixels on the screen in the horizontal or vertical direction that are contained within one degree of field of view. For example, 60 ppd corresponds to the limit of resolution at which an observer with 1.0 visual acuity can distinguish one pixel. Therefore, when an observer with 0.7 visual acuity looks at a screen with 60 ppd, the observer will not be able to clearly distinguish the boundary between two adjacent pixels, and will perceive the boundary between the two adjacent pixels as blurred. As a result, the observer with 0.7 visual acuity can see a continuous image where there are no boundaries between pixels.

[0051] The inventor's experiments showed that when a design value of 40 ppd or higher was used, observers with visual acuity of approximately 1.0 to 1.2 could recognize the boundaries between pixels, but felt that these boundaries were almost imperceptible, resulting in a natural and clear image displayed on the screen.

[0052] The horizontal or vertical pixel count of the display element 132 is between 2000 and 4000, and the field of view angle θv of the eyepiece optical system 131 is between 35 and 60 degrees. Examples of combinations of pixel count and field of view angle within these ranges are shown below, along with the "ppd" values.

[0053] (A) (2000 pixels, 60-degree field of view), 33 ppd (B) (2000 pixels, 35-degree field of view), 57 ppd (C) (4000 pixels, 60-degree field of view), 60ppd (D) (4000 pixels, 35-degree field of view), 114ppd Of the above (A) to (D), (B) to (D) satisfy the condition of "40 ppd or more". Therefore, it is desirable for the designer to adopt one of the above (A) to (D) as the design value (number of pixels, field of view) for the microscope 10. However, the designer may adopt (A) as the design value for the microscope 10 even though it does not satisfy the condition of "40 ppd or more".

[0054] As shown in Figure 6, the eyepiece optical system 131 forms an image circle Cr whose maximum diameter is smaller than the horizontal width of the display element 132. The image circle Cr shown in Figure 6 may be a perfect circle. In this case, the eyepiece optical system 131 forms an image circle Cr whose maximum diameter is smaller than both the horizontal and vertical widths of the display element 132. The image circle Cr may also be an ellipse. In this case, the maximum diameter of the image circle Cr may be smaller than both the horizontal width and the vertical width of the display element 132.

[0055] Figure 7 is a conceptual diagram illustrating the apparent distance to the screen SL in stereoscopic vision. When viewing an object in stereoscopic vision, the observer directs each eye inward and focuses on a single point on the object. The human brain unconsciously controls the distance to the object and the direction of the eyes, so the observer can usually view the object in stereoscopic vision without feeling any discomfort. However, if the relationship between the distance to the object and the convergence angle of the eyes is significantly different from the normal situation, an "angle of convergence discrepancy" occurs. When an angle of convergence discrepancy occurs, the observer can still view the object in stereoscopic vision, but experiences significant eye strain.

[0056] Furthermore, at very close distances, such as about 30 mm from the observer's eye, the act of observing the image itself can cause fatigue. Therefore, in this embodiment, the "apparent distance" to the screen SL is adjusted to about 250 mm using the eyepiece 1310, and an appropriate convergence angle is set in the pair of eyepiece optical systems 131 so that the lines of sight of the observer's left eye and right eye coincide at a distance of 250 mm. This makes it possible to construct an eyepiece optical system that provides natural stereoscopic vision with less fatigue. A specific example of the convergence angle will be described later using Figure 9.

[0057] Figure 8 is a conceptual diagram illustrating the principal ray angle θr. In the eyepiece optical system 131, multiple light beams are generated from the screen of the display element 132 toward the observer's pupil. Figure 8 shows light beams Lf1 to Lf3 as an example of multiple light beams. The light ray that occurs in the center of the light beam is called the "principal ray". Figure 8 shows the principal rays Cf1 to Cf3.

[0058] The principal ray angle θr is the angle between the normal to the screen of the display element 132 and the principal ray. In this embodiment, the principal ray angle θr of the microscope 10 is a value of 1 degree or less. The reason for designing the principal ray angle θr to be a value of 1 degree or less is explained below.

[0059] The microscope 10 adjusts the diopter by changing the distance from the display element 132 to the eyepiece lens 1310 according to the observer's visual acuity. For example, the control device 14 (see Figure 2) moves the display element 132 horizontally in the direction of the optical path OR in response to the observer's operation. When the principal ray angle θr is large, the range of the screen visible to the observer changes before and after diopter adjustment. In other words, when the principal ray angle θr is large, the magnification of the eyepiece optical system 131 changes before and after diopter adjustment.

[0060] In particular, if the observer's left and right visual acuity differs significantly, the difference in magnification between the left and right eyepiece optical systems 131 becomes large. As a result, it becomes difficult for the observer to perceive depth. In the inventor's experiments, it was necessary to design the movement range of the display element 132 to be approximately 28 mm in order to adjust the diopter within the range that satisfies the JIS standard. When the principal ray angle was 1 degree, the area of ​​the screen that the observer could see changed by approximately 0.5 mm before and after diopter adjustment. One pixel of the display element used in the experiment was 0.024 mm. Therefore, when the principal ray angle was 1 degree, the area of ​​the screen that the observer could see changed by an area equivalent to approximately 21 pixels before and after diopter adjustment.

[0061] Through experiments, the inventors confirmed that if the change in the number of pixels due to diopter adjustment is around 20, observers generally do not notice any discomfort. Based on this, the inventors concluded that it is appropriate to set the principal ray angle θr to 1 degree or less.

[0062] <Design values ​​for object unit 12> Figure 9 is a diagram illustrating the working distance WD from the objective unit 12 to the subject. Figure 9 shows a patient's oral cavity as an example of a subject. As shown in Figure 9, the objective optical systems 121a and 121b are arranged such that a convergence angle θc is formed by the optical axis of the objective optical system 121a and the optical axis of the objective optical system 121b.

[0063] The working distance WD of the objective optical system 121 is between 250 mm and 450 mm, the convergence angle θc of the objective optical system 121 is between 4 degrees and 8 degrees, and the distance Ds of the pair of objective optical systems 121,121 is 25 mm. The working distance WD is the distance from the objective optical system 121 to the subject. More precisely, the working distance WD is the distance from the subject-side lens surface of the objective lens 1210 to the subject.

[0064] In typical microscopes, the working distance is only a few millimeters. Even in the case of typical optical stereo microscopes, the working distance is only about 50 mm. Thus, the working distance of typical microscopes is short. However, in the case of medical microscopes, the observer needs to magnify the treatment area with the microscope while inserting a medical instrument (such as an air turbine) into the treatment area. Considering the observer's operability, it is preferable to have a longer working distance (WD) in the case of medical microscopes. Therefore, in this embodiment, the working distance (WD) is designed to be between 250 mm and 450 mm.

[0065] When the working distance (WD) is 250 mm or more, the diameter of the objective lens 1210 is approximately 25 mm. From the standpoint of miniaturization, it is desirable to reduce the diameter of the objective lens 1210, but reducing the diameter reduces the F-number (aperture value). As a result, the illumination of the optical system becomes very low. For this reason, in this embodiment, the diameter of the objective lens 1210 is set to approximately 25 mm.

[0066] When the diameter of the objective lens 1210 is approximately 25 mm, the distance Ds between the objective optical system 121 (121a) and the objective optical system 121 (121b) must be at least 25 mm, taking into account the imaging function. Alternatively, the distance between the objective lenses 1210 provided in each of the pair of objective optical systems 121 may be defined as "distance Ds".

[0067] When the working distance WD is 250 mm and the diameter of the objective lens 1210 is 25 mm, the convergence angle θc is approximately 5.7 degrees. Increasing the distance Ds will increase the convergence angle θc. For example, when the working distance WD is 250 mm and the distance Ds is 35 mm, the convergence angle θc is approximately 8 degrees. From the perspective of the diameter of the objective lens 1210, it is desirable to have a convergence angle θc of approximately 5.7° or more. Note that the working distance WD only needs to be 250 mm or more, and may exceed, for example, 450 mm.

[0068] Figure 10 is a diagram illustrating the relationship between the convergence angle θc and the focus adjustment range. Figure 11 is a graph showing the relationship between the convergence angle θc and the focus adjustment range. As shown in Figure 10, the imaging ranges 1220a and 1220b captured by the objective optical systems 121a and 121b shift depending on the focus distance. When the portion of the "Center" line shown in Figure 10 is included in both the imaging range 1220a and the imaging range 1220b, the microscope 10 can acquire a pair of images for stereoscopic viewing.

[0069] Figure 11 is a graph obtained when the working distance WS is set to 350 mm and the magnification of the objective lens 1210 is set to 33x. As shown in the graph, it can be seen that the smaller the convergence angle θc, the wider the focus range can be secured. For practical purposes, it is desirable to set the convergence angle θc to between 4 and 8 degrees.

[0070] <Variation> Figure 12 is a diagram illustrating a modified example. The eyepiece unit 130, which is a modified example, differs from the eyepiece unit 13 described so far in that it is provided with a mirror 1315 and two eyepiece lenses (eyepiece lenses 1310a and 1310b).

[0071] In the eyepiece unit 130, the field lens 1311 and the eyepieces 1310a and 1310b are arranged such that the optical axis of the field lens 1311 intersects with the optical axes of the eyepieces 1310a and 1310b. The mirror 1315 refracts the image light toward the observer. More specifically, the mirror 1315 reflects the image light output from the field lens 1311, changing the direction of the image light so that it is directed toward the eyepieces 1310a and 1310b. Therefore, the optical path OR4 of the eyepiece unit 130 is bent from a direction parallel to the optical axis of the field lens 1311 to a direction parallel to the optical axes of the eyepieces 1310a and 1310b.

[0072] In the modified version, the size of the eyepiece unit 130 can be reduced in a direction parallel to the optical axes of the eyepieces 1310a and 1310b. This allows the observer to observe the treatment area while looking through the eyepiece unit 130 at a close distance to the patient. Furthermore, the eyepiece unit 130 in the modified version is equipped with two eyepieces 1310a and 1310b. Therefore, the resolution can be further increased compared to the eyepiece unit 13. Thus, the eyepiece optical system in the modified version includes multiple lenses (field lens 1311, eyepieces 1310a and 1310b) arranged in the direction of the optical path OR4 that guides the image light from the display element 132 to the observer.

[0073] The eyepiece unit 130 is equipped with a field lens 1311, similar to the eyepiece unit 13. As explained earlier, this allows for a reduction in the diameter of the eyepieces 1310a and 1310b. Furthermore, in the eyepiece unit 130, the field lens 1311 allows for a reduction in the size of the mirror 1315.

[0074] In the modified example, a microscope 10 is envisioned in which an eyepiece unit 130 is applied in place of the eyepiece unit 13. Various design values ​​for the eyepiece unit 13 have been described so far. These design values ​​may be applied to the eyepiece unit 130 in the modified example, as long as no inconsistencies arise.

[0075] <Other variations> In this embodiment, an example is shown in which the objective unit 12 and the eyepiece unit 13 are housed in the observation unit 11. However, the observation unit 11 that houses the objective unit 12 and the eyepiece unit 13 does not necessarily have to exist. The microscope 10 only needs to have a structure that transmits the image acquired by the objective unit 12 to the eyepiece unit 13.

[0076] Therefore, it is sufficient that the objective unit 12 and the eyepiece unit 13 are connected in a way that enables communication. In this case, a configuration in which the objective unit 12 and the eyepiece unit 13 communicate directly may be adopted, or a configuration in which the objective unit 12 and the eyepiece unit 13 communicate via the control device 14 may be adopted. As for the communication method, a wired communication method using wiring may be adopted, or a wireless communication method that does not use wiring may be adopted.

[0077] In this embodiment, specific examples of various design values ​​for the microscope 10 have been described. However, the microscope 10 only needs to have a horizontal or vertical pixel count of 2000 or more and 4000 or less for the display element 132, and a field of view of 35 degrees or more and 60 degrees or less for the eyepiece optical system 131. Under these conditions, the microscope 10 only needs to adopt at least one of the other design values ​​described in this embodiment.

[0078] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included. The configurations illustrated in these embodiments and those illustrated in the variations may be combined as appropriate.

[0079] (Claim 1) A medical microscope comprising an objective optical system, an image sensor for capturing an image of a subject formed through the objective optical system, a display element for displaying the image acquired by the image sensor, and an eyepiece optical system for guiding the image light from the display element to an observer, wherein the objective optical system comprises a first objective optical system and a second objective optical system, the image sensor comprises a first image sensor corresponding to the first objective optical system and a second image sensor corresponding to the second objective optical system, the display element comprises a first display element corresponding to the first image sensor and a second display element corresponding to the second image sensor, the eyepiece optical system comprises a first eyepiece optical system corresponding to the first display element and a second eyepiece optical system corresponding to the second display element, the first objective optical system and the second objective optical system are arranged such that a convergence angle is formed by the optical axis of the first objective optical system and the optical axis of the second objective optical system, the horizontal pixel count or vertical pixel count of the display element is 2000 or more and 4000 or less, and the field of view of the eyepiece optical system is 35 degrees or more and 60 degrees or less.

[0080] (Claim 2) The medical microscope according to claim 1, wherein the eyepiece optical system includes a plurality of lenses arranged in the direction of the optical path that guides the image light from the display element to the observer.

[0081] (Claim 3) The medical microscope according to claim 2, wherein the plurality of lenses include an eyepiece and a field lens disposed between the display element and the eyepiece.

[0082] (Claim 4) The medical microscope according to claim 1, wherein the eyepiece optical system includes an eyepiece lens having a diameter of 60 millimeters or less.

[0083] (Claim 5) The medical microscope according to any one of claims 1 to 4, wherein the convergence angle is 4 degrees or more and 8 degrees or less, and the working distance is 250 millimeters or more.

[0084] (Claim 6) The eyepiece optical system forms an image circle whose maximum diameter is smaller than the horizontal or vertical width of the display element, according to any one of claims 1 to 4.

[0085] (Claim 7) The medical microscope according to any one of claims 1 to 4, wherein the principal ray angle of the eyepiece optical system is 1 degree or less.

[0086] (Claim 8) The eyepiece optical system has an eye point of 10 millimeters or more, as described in any one of claims 1 to 4.

[0087] (Claim 9) The eyepiece optical system comprises a mirror that refracts the image light toward the observer, as described in any one of claims 1 to 4.

[0088] (Claim 10) The medical microscope according to any one of claims 1 to 4, wherein the distance between the first objective optical system and the second objective optical system is 25 mm. [Explanation of Symbols]

[0089] 10 Microscope, 11,11a,11b Observation unit, 12,12a,12b,1200 Objective unit (imaging device), 13,13a,13b,130,1300 Eyepiece unit, 14 Control device, 20 Chair unit, 21 Examination chair, 23 Foot controller, 27 Basin unit, 28 Cleaning unit, 29 Base, 101 Housing, 102 Handle, 121,121a,121b Objective optical system, 122,122a,122b Image sensor, 131,131a,131b Eyepiece optical system, 132,132a,132b Display element, 211 Seat, 212 Backrest, 213 Headrest, 301 Pole, 302 Arm, 1210 Objective lens, 1220a, 1220b; Imaging area, 1310, 1310a, 1310b; Eyepiece, 1311; Field lens, 1315; Mirror, AP; Eye point, Cr; Image circle, La, Lb; Optical axis, Lf1~Lf3; Light beam, OP1~OP4; Optical path, SC; Screen, WS; Working distance, θc; Convergence angle, θr; Principal ray angle, θv; Field of view.

Claims

1. A microscope for observing a subject, A pair of display elements that the observer looks at with each of their eyes, An image sensor that corresponds to each of the pair of display elements and outputs a pair of images of the captured subject, A control device that displays each of the pair of images on the pair of display elements in such a way that it creates parallax for an observer looking through the pair of display elements, Equipped with, The control device is a microscope that adjusts the convergence angle of the pair of images to be displayed on the display element by acquiring a portion of the pair of images output from the image sensor.

2. The microscope according to claim 1, wherein the control device acquires a portion of the pair of images output from the image sensor according to the focus distance.

3. The microscope according to claim 1 or claim 2, wherein the convergence angle is 4 degrees or more and 8 degrees or less.

4. The system further comprises an objective optical system corresponding to the aforementioned image sensor, The microscope according to claim 1 or claim 2, wherein the working distance, which is the distance from the objective optical system to the subject, is 250 millimeters or more.

5. The microscope according to claim 1, wherein the subject is the oral cavity and the microscope is a dental microscope.

6. A method for controlling a microscope used to observe a subject, The aforementioned microscope is A pair of display elements that the observer looks at with each of their eyes, Each of the pair of display elements corresponds to an image sensor that outputs a pair of images of the captured subject, The method described above includes a number of steps performed by a computer, The aforementioned steps are: The steps include: displaying each of the pair of images on the pair of display elements in such a way that a parallax is created for an observer looking through the pair of display elements; A method comprising the step of adjusting the convergence angle of the pair of images to be displayed on the display element by acquiring a portion of the pair of images output from the image sensor.

7. The method according to claim 6, wherein the adjustment step includes the step of acquiring a portion of the pair of images output from the image sensor according to the focus distance.

8. The method according to claim 6 or claim 7, wherein the convergence angle is 4 degrees or more and 8 degrees or less.

9. The microscope further comprises an objective optical system corresponding to the image sensor, The method according to claim 6 or claim 7, wherein the working distance, which is the distance from the objective optical system to the subject, is 250 millimeters or more.

10. The method according to claim 6 or 7, wherein the subject is the oral cavity and the microscope is a dental microscope.

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