Oral cavity imaging device

Abstract

To provide an oral cavity imaging device which is easy to operate, can easily and excellently image subject tissue, and can particularly contribute to screening of oral cavity cancer.SOLUTION: An oral cavity imaging device according to the present invention includes: an excitation light source 20 that emits excitation light in a predetermined wavelength range that excites subject tissue in an oral cavity; an imaging device 35 that receives fluorescence emitted from the subject tissue excited by the excitation light and images the subject tissue; and a mirror 24 that reflects the excitation light emitted from the excitation light source 20 and directs it toward the subject tissue, and reflects light in the predetermined wavelength range among the fluorescence emitted by the subject tissue and transmits other fluorescence. In addition, an optical axis O3 of the imaging optical system of the imaging device 35 substantially coincides with an illumination optical axis O2 of the excitation light reflected by the mirror 24 and directed to the subject tissue.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an oral cavity imaging device that captures images of tissues within the oral cavity for examination, and in particular to an oral cavity imaging device that is suitable for screening for oral cancer. [Background technology]

[0002] Oral cancer accounts for about 1-2% of all cancers, with an incidence rate of 8-9 per 100,000 people. More than 90% of cases are classified as squamous cell carcinoma, with the tongue being the most common site. Cancer can also develop in the gums, cheek mucosa, palate, and lips.

[0003] In Japan, oral cancer is often discovered at an advanced stage and treatment begins at a later stage than in Western countries, and it has been pointed out that there is little awareness of oral cancer among the public and few opportunities for screening tests.

[0004] When oral cancer progresses and primary tumor resection or reconstructive surgery is performed, oral functions such as chewing, swallowing, and speaking generally decline, making early detection and treatment, which are minimally invasive and require only partial resection, extremely important. To achieve this, oral cancer screening tests must be actively conducted.

[0005] For this reason, systems for oral cancer screening and information management (see, for example, Patent Document 1) have been developed, as well as intraoral fluorescence observation devices for oral cancer screening that utilize optical technology, taking advantage of the property of healthy oral mucosa to emit green fluorescence when excited by blue light. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-077436 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional systems and observation devices are large and complex, require tedious setup, and are difficult to operate, often making it difficult to efficiently obtain images with good contrast. Furthermore, although detecting oral cancer is difficult unless you are a specialized oral surgeon, it would be desirable to establish an examination system that allows for easy screening during examinations, especially at dental clinics, where there are many opportunities to observe the oral cavity.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide an oral cavity imaging device that is easy to operate, can easily and effectively photograph test tissue, and can particularly contribute to the screening of oral cancer. [Means for solving the problem]

[0009] To achieve the above object, the oral cavity imaging device of the present invention includes a basic configuration including an excitation light source that emits excitation light in a predetermined wavelength range to excite intraoral tissue, an imaging device that images the test tissue by receiving fluorescence emitted from the test tissue irradiated and excited by the excitation light, and a mirror that reflects the excitation light emitted from the excitation light source and directs it toward the test tissue, and that reflects fluorescence within the predetermined wavelength range emitted by the test tissue and transmits the remaining fluorescence, wherein the optical axis of the imaging optical system of the imaging device and the irradiation optical axis of the excitation light reflected by the mirror and directed toward the test tissue are substantially aligned (hereinafter referred to as a first characteristic configuration). Alternatively, under the basic configuration, the incident direction of the fluorescence that passes through the mirror and enters the imaging device is substantially aligned with the irradiation direction of the excitation light that is reflected by the mirror and directed toward the test tissue (hereinafter referred to as a second characteristic configuration). Alternatively, under the basic configuration, the optical axis of the imaging optical system of the imaging device is positioned so that the imaging optical system can receive the fluorescence at an amount of light that is 50% or more of its maximum amount (the optical axis of the imaging optical system is configured to be positioned at a position within a plane 150 mm away from the center of the mirror where it can receive an amount of light that is 50% of the maximum amount of light at the center position) (hereinafter referred to as a third characteristic configuration).

[0010] In this way, by having at least one of the first, second, and third characteristic configurations, i.e., by matching the irradiation range with the shooting range or by appropriately setting (adjusting) the amount of light for shooting, it becomes possible to obtain clear images with good contrast of the test tissue, thereby enabling accurate diagnosis, particularly for screening of oral cancer.

[0011] In the first characteristic configuration, "substantially coincident" refers not only to a perfect coincidence between the optical axis of the imaging optical system of the imaging device and the optical axis of the excitation light reflected by the mirror and directed toward the test tissue, but also to a case in which the optical axis of the imaging optical system and the optical axis of the excitation light are parallel but not coincident, with a deviation within a predetermined range. When the optical axis of the imaging optical system and the optical axis of the excitation light are parallel, the deviation between the optical axes is preferably within 3 mm. This allows optimal illumination for imaging by the imaging device and the acquisition of clear images with good contrast of the test tissue. In the second characteristic configuration, "substantially coincident" refers not only to a perfect coincidence between the direction of incidence of the fluorescence incident on the imaging device and the direction of irradiation of the excitation light directed toward the test tissue, but also to a deviation within a predetermined range, specifically, an angular deviation of within ±5 degrees.

[0012] Here, the aforementioned deviation of 3 mm and deviation angle of ±5 degrees are assumed to be when the test tissue is viewed at a position 150 mm away from the center of the mirror. 150 mm is assumed to be the appropriate positional relationship between observation with the naked eye and an imaging device with an irradiation function, and it is preferable that the deviation amount be 3 mm and the deviation angle be ±5 degrees at this 150 mm position.

[0013] Furthermore, in the above configuration of the present invention, it is preferable that the mirror is positioned so as to diagonally intersect the optical path of the fluorescence emitted from the test tissue and proceeding toward the imaging device and the optical path of the excitation light emitted from the excitation light source, i.e., a single mirror is used common to the two optical paths, but separate mirrors may be used for the optical paths of the fluorescence and the excitation light. In the case where separate mirrors are used, the mirror provided in the optical path of the excitation light emitted from the excitation light source needs to reflect the excitation light within a predetermined wavelength range (e.g., light of a first color) emitted from the excitation light source and direct it toward the test tissue, while the mirror provided in the optical path of the fluorescence proceeding toward the imaging device needs to reflect light within the predetermined wavelength range (e.g., light of the first color) of the fluorescence emitted by the test tissue and transmit other fluorescence (light of colors other than the first color).

[0014] Furthermore, in the above-described configuration of the present invention, it is preferable that the emission optical axis of the excitation light emitted from the excitation light source and directed toward the mirror is approximately perpendicular to the optical axis of the imaging optical system of the imaging device. When these optical axes are exactly perpendicular to each other and the mirror is tilted at exactly 45 degrees relative to these optical axes, the optical axis of the imaging optical system of the imaging device and the irradiation optical axis of the excitation light reflected by the mirror and directed toward the test tissue will be perfectly aligned, and the amount of misalignment between these optical axes will be zero. In other words, the amount of misalignment between the optical axes described above is determined by the mechanical positional relationship between the mirror, the imaging device, and the excitation light source.

[0015] In the above configuration of the present invention, it is preferable that the mirror reflects light with a wavelength of less than 500 nm incident on the mirror at an incident angle of approximately 45° as excitation light in the predetermined wavelength range, and transmits light with a wavelength of 500 nm or more as the other fluorescence. This allows the mirror to reflect blue light and transmit other light, allowing the oral cavity imaging device of the above configuration to be used for accurate diagnosis of diseased tissue such as oral cancer, taking advantage of the characteristic that healthy oral mucosa is excited by blue light and emits green fluorescence. An example of such a wavelength-selective mirror is a dichroic mirror.

[0016] Furthermore, the oral cavity photographing device of the present invention having the above-described configuration preferably further includes a control circuit for controlling the excitation light source and the photographing device, and the control circuit is capable of adjusting the amount of excitation light emitted from the excitation light source. This maximizes light utilization efficiency and also makes it possible to obtain optimal amounts of light (selectively change the illumination light amount and the photographing light amount) for observation, which requires the highest possible illuminance (brightness), and for photographing, which requires an amount of light appropriate for photographing (excessive light amount should be avoided). In particular, it makes it possible to prevent the occurrence of the so-called blown-out highlight phenomenon, in which excessively bright areas appear white in the photographed image.

[0017] An oral imaging device with such a light intensity adjustment function is particularly useful in situations where a doctor uses the illumination of the imaging device to observe a living body with the naked eye and only captures an abnormality with a camera when it is found. When visually inspecting intraoral tissue with the naked eye, a higher illumination intensity improves visibility. However, capturing an image of the tissue with a camera while the illumination intensity is high can exceed the limit of the light received by the camera's imaging unit, resulting in overexposure in the captured image. Therefore, by automatically reducing (adjusting) the illumination intensity (excitation light intensity) so as not to exceed the limit of the light received by the camera's imaging unit when capturing an image of the tissue, overexposure can be reduced.

[0018] In addition, in relation to the control circuit's adjustment of the excitation light intensity, the oral cavity imaging device of the present invention may include a shutter switch for driving a shutter that controls the exposure of the imaging unit of the imaging device. In this case, the control circuit preferably controls the excitation light source to reduce the intensity of the excitation light when the shutter switch is switched from OFF, which does not expose the imaging unit, to ON, which exposes the imaging unit, and controls the imaging device to capture an image of the test tissue when the shutter switch is switched from ON to OFF. This ensures the highest possible illuminance (brightness) during observation, while providing an appropriate amount of light for imaging (avoiding excessive light). In this configuration, for example, the light intensity may be adjusted (dimmed) when the operator half-presses the shutter switch. Alternatively, the light intensity may be adjusted (dimmed) when the operator presses the shutter switch with their finger, and imaging may be performed when the operator releases their finger from the shutter switch. This allows for easy operation to ensure sufficient illumination light intensity during visual observation and reduce overexposure. Alternatively, the control circuit may reduce the amount of excitation light when the shutter switch is half-pressed, control the imaging device to image the test tissue when the shutter switch is fully pressed, and restore the amount of excitation light to the original amount including the maximum amount when the shutter switch is fully released and imaging by the imaging device is completed. Alternatively, the control circuit may have a first control mode in which excitation light is emitted from the excitation light source at a first light amount, a second control mode in which excitation light is emitted from the excitation light source at a second light amount that is reduced from the first light amount, and a third control mode in which the imaging device is controlled to emit excitation light from the excitation light source at the second light amount that is reduced from the first light amount and to image the test tissue, and switch among the three control modes in response to operation of the shutter switch. [Effects of the Invention]

[0019] The oral cavity photographing device of the present invention is easy to operate, can photograph the tissue to be examined simply and effectively, and can particularly contribute to the screening of oral cavity cancer. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic perspective view of an oral cavity photographing apparatus according to an embodiment of the present invention. [Figure 2] 2A is a schematic front view of the oral cavity photographing device of FIG. 1, FIG. 2B is a cross-sectional view taken along line AA in FIG. 2A, and FIG. 2C is a cross-sectional view taken along line CC in FIG. [Figure 3] 2 is a schematic diagram showing the directions of travel of excitation light and fluorescence emitted by the optical elements of the oral cavity imaging device of FIG. 1. FIG. [Figure 4] 2A is a perspective view of an LED filter provided in an excitation light source such as an LED of the oral cavity imaging device of FIG. 1, and FIG. 2B is a cross-sectional view of the LED lens of FIG. 2A. [Figure 5] 2 is a ray diagram showing reflection of excitation light by a mirror of the oral cavity imaging device of FIG. 1. [Figure 6] FIG. 2 is a block diagram of components related to light intensity adjustment of the oral cavity photographing device of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. This embodiment can realize a highly reliable system, particularly in a sensing system, and contributes to the development of resilient infrastructure. The target is "9. Industry, innovation and infrastructure" of the Sustainable Development Goals (SDGs) advocated by the United Nations, which states, "9.1 Develop quality, reliable, sustainable and resilient infrastructure, including regional and transborder infrastructure, to support economic development and human well-being, with a focus on affordable and equitable access for all."

[0022] 1 and 2 show an oral cavity imaging device 1 according to one embodiment of the present invention. As shown, this oral cavity imaging device 1 is configured with various optical elements built into a resin housing 10. The housing 10 has a substantially L-shaped configuration in which a first cylindrical portion 10A and a second cylindrical portion 10B, each having a substantially rectangular parallelepiped shape, intersect perpendicularly, forming an illumination / light-receiving portion 10C at the intersection. For convenience, a coordinate system for defining directions is shown in FIGS. 1 and 2. Here, the extension direction of the first cylindrical portion 10A is defined as the X direction, the extension direction of the second cylindrical portion 10B is defined as the Y direction, and the direction perpendicular to the X and Y directions is defined as the Z direction.

[0023] As can be seen from Fig. 2(b), which is a cross-sectional view taken along line AA in Fig. 2(a), an excitation light source 20 is disposed near the illumination / light-receiving unit 10C within the first tubular portion 10A, which also functions as a gripping unit. The excitation light source 20 emits excitation light in a predetermined wavelength range to excite intraoral tissue. In particular, in this embodiment, a blue LED that emits blue light with a wavelength of 430 to 490 nm as excitation light is used as the excitation light source 20 (hence, hereinafter, the excitation light source may be referred to as an LED (LED chip)). The blue LED (LED chip) 20 is mounted on a control board 50 (see also Fig. 3) together with an LED driver 58 (see Fig. 6) that turns it on.

[0024] In order to achieve high utilization efficiency of the excitation light from the excitation light source 20, in this embodiment, the excitation light from the excitation light source 20 is radiated through a lens 22. Here, the lens 22 is configured to collect and collimate the excitation light that is widely diverged from the excitation light source 20 made of an LED chip. Specifically, as shown in FIG. 4 , the lens 22 has a substantially truncated cone shape and a housing groove 22a at its bottom for housing the LED chip 20, which is the excitation light source. The lens 22 also has a hemispherical first lens portion 22A located at the center inside and a second lens portion 22B that extends radially outward toward the upper side (the emission side) to form the side of the truncated cone. The lens 22 emits blue excitation light emitted from the LED chip 20 embedded in its bottom portion through the first lens portion 22A, and then repeatedly reflects the light from the reflecting surface 22Ba, which gradually expands radially outward of the second lens portion 22B surrounding the first lens portion 22A, converting the light into nearly parallel light (collimated light) and directing it to the mirror 24, described later, located within the illumination / light-receiving portion 10C.

[0025] Between the mirror 24 and the lens 22, an LED filter 26 is provided to cut off light in a wavelength range other than blue light.

[0026] Within the approximately cubic illumination / light-receiving unit 10C, mirrors 24 are disposed diagonally across almost the entire internal space. These mirrors 24 reflect blue excitation light (light with a wavelength of 430 to 490 nm) emitted from the excitation light source 20 and direct it through the irradiation port 10Ca to the outside of the device (and thus, toward the tissue under test during examination imaging, as operated by the operator). They also reflect blue light (blue light with a wavelength of 430 to 490 nm) from light incident from the outside (fluorescence emitted by the tissue under test during examination imaging) and transmit other light (fluorescence). In this embodiment, a dichroic mirror is used as the wavelength-selective mirror 24.

[0027] An imaging device (camera) 35 consisting of a lens unit 30 and an image sensor 32 is disposed within the second tube portion 10B, facing the mirror 24. The imaging device 35 captures an image of the test tissue by receiving fluorescence emitted from the test tissue when the tissue is excited by irradiation with excitation light. The image sensor 32 is positioned to receive an image of the object (test tissue) formed by the lens unit 30. The image sensor 32 has a transparent cover on the outside and is equipped with a CCD, CMOS, or the like inside, and converts light that is collected through the lens unit 30 and reaches the image sensor 32 into an electrical signal. The converted electrical signal is then converted into analog data or digital data, which are components of the image data captured by the imaging device 35.

[0028] A filter 28 is disposed between the lens unit 30 and the mirror 24 to cut out the small amount of blue light that passes through the mirror 24. Examples of such a filter 28 include a bandpass filter that transmits only visible fluorescence, or a longpass filter that transmits visible fluorescence and infrared light.

[0029] The aforementioned mirror 24 disposed within the illumination / light-receiving unit 10C is positioned so as to cross obliquely (at 45° in this embodiment) the optical path of the fluorescence emitted from the test tissue and proceeding toward the imaging device 35, and the optical path of the excitation light emitted from the excitation light source 20 (see also FIG. 3). Therefore, as described above, the mirror 24 reflects blue light (excitation light with a wavelength of 430 to 490 nm (or less than 500 nm)) incident on the mirror 24 from the excitation light source 20 at an incident angle of approximately 45°, while transmitting light with a longer wavelength (or a wavelength of 500 nm or more).

[0030] 5 (see also FIG. 2(b)), the wavelength-selective mirror 24 causes the optical axis O3 of the imaging optical system (lens unit 30) of the imaging device 35 to substantially coincide with the irradiation optical axis O2 of the excitation light reflected by the mirror 34 and directed toward the test tissue, or causes the incident direction of the fluorescence that passes through the mirror 24 and enters the imaging device 35 to substantially coincide with the irradiation direction of the excitation light that is reflected by the mirror 24 and directed toward the test tissue, or further, the optical axis O3 of the imaging optical system (lens unit 30 and image sensor 32) of the imaging device 35 is positioned so that the imaging optical system can receive fluorescence at an intensity that is 50% or more of its maximum intensity. In addition, in this embodiment, the emission optical axis O1 of the excitation light emitted from the excitation light source 20 and directed toward the mirror 24 and the optical axis O3 of the imaging optical system of the imaging device 35 are substantially perpendicular (orthogonal in this embodiment).

[0031] When light is irradiated onto a tissue to be examined (such as the tongue) by the LED 20 as in this embodiment, the center (the point where the optical axis meets the tissue to be examined) is the brightest, and the amount of light decreases as the distance from that point to the outside increases. Therefore, in this embodiment, the LED 20 is irradiated so that the amount of light emitted from the LED 20 is the brightest at the part that is most desired to be observed with the naked eye. As described above, the center of the illumination range is aligned with the center of the camera's imaging range, thereby positioning the center of the imaging range at the brightest point, enabling the desired clarity of the photograph to be obtained.

[0032] In the above configuration, the term "substantially coincident" between the optical axes O2 and O3 refers not only to the complete coincidence between the optical axis of the imaging optical system of the imaging device and the optical axis of the excitation light reflected by the mirror and directed toward the test tissue, but also to the case where the optical axis of the imaging optical system and the optical axis of the excitation light are parallel but misaligned within a predetermined range. When the optical axis of the imaging optical system and the optical axis of the excitation light are parallel, the misalignment between the optical axes is preferably within 3 mm. This allows optimal illumination for imaging by the imaging device and the acquisition of clear, high-contrast images of the test tissue. Furthermore, the term "substantially coincident" between the incident direction and the illumination direction refers not only to the complete coincidence between the incident direction of the fluorescence entering the imaging device and the illumination direction of the excitation light directed toward the test tissue, but also to the case where these directions are misaligned within a predetermined range, specifically, within ±5 degrees.

[0033] In this case, the aforementioned 3 mm offset and ±5° offset angle are based on the assumption that the test tissue is viewed at a position 150 mm away from the center of the mirror. The 150 mm offset is assumed to be based on the appropriate positional relationship between visual observation and the imaging device with illumination function. At this 150 mm position, it is preferable that the offset be 3 mm and the offset be ±5 degrees. This assumed 150 mm was determined as a position that satisfies both the requirement that the LED 20 of the oral cavity imaging device 1 illuminate the test tissue in the oral cavity as brightly as possible and that the main body of the oral cavity imaging device 1 does not interfere with the visual observation of the test tissue in the oral cavity. The focal position of the optical lens during imaging is also set nearby. However, the usage state of the oral cavity imaging device 1 is not limited to 150 mm.

[0034] Furthermore, in addition to the optical components described above, the oral cavity photographing device 1 of this embodiment is also provided with a shutter switch (shutter button) 34 for driving a shutter that controls exposure to the imaging section (image sensor 32) of the imaging device 35 (see FIGS. 1, 2, and 6). A signal accompanying the ON / OFF of the shutter switch 34 is input to a control circuit 60 on a control board 50 that controls the imaging device (camera) 35 and an LED driver 58, as shown in FIG. 6. The shutter switch 34 is provided in a position (for example, on the outer surface of the first tube portion 10A near the illumination / light-receiving section 10C) that can be easily operated by the fingers of the hand holding the first tube portion 10A.

[0035] The irradiation port 30Ca of the illumination / light-receiving unit 10C may be provided with a protective hood (not shown) to prevent the mirror 24 and lens unit 30 from fogging due to the subject's breathing and from becoming dirty due to coughing. The second tube portion 10B is provided with an aperture ring / focus ring 40 (see FIG. 1) for the imaging device 35. Furthermore, the end face of the distal end of the first tube portion 10A is provided with electrical elements 36 (see FIG. 2(b)), such as a connection terminal for a transmission cable that transmits image signals from the imaging device 35 to an external device such as a monitor, and a power switch for driving the device.

[0036] Furthermore, in this embodiment, the aforementioned control circuit 60 (see FIG. 6 ), which controls the imaging device (camera) 35 and the LED driver 58, is capable of adjusting the amount of excitation light emitted from the excitation light source (LED) 20. Specifically, for example, when the shutter switch 34 is switched from switch OFF, which does not expose the imaging section (image sensor 32), to switch ON, which exposes the imaging section, the control circuit 60 controls the excitation light source 20 to reduce the amount of excitation light, and when the switch is switched from ON to switch OFF, the control circuit 60 controls the imaging device 35 to capture an image of the test tissue.

[0037] That is, in this embodiment, the amount of excitation light emitted from the excitation light source as the illumination light amount is automatically adjusted during shooting. Specifically, as an example, the illumination light amount (amount of excitation light) is automatically adjusted when the shutter switch 34 is half-pressed, or the illumination light amount (amount of excitation light) is automatically adjusted when the shutter switch 34 is pressed, and shooting is automatically performed when the shutter switch 34 is released. Furthermore, the control circuit 60 controls the reduction in the amount of light by controlling the current supplied to the LED 20 to reduce the amount of light emitted by the LED 20 (for example, during observation with the naked eye, the LED 20 is made to emit light at the maximum amount of light, and during shooting, the current amount is temporarily changed to 50%. Furthermore, after shooting is completed, the light amount of the LED 20 is controlled to return to its original amount).

[0038] Such control of the excitation light intensity (illumination light intensity) and imaging is particularly useful in a usage pattern in which a doctor observes a living organism with the naked eye using the illumination of the oral cavity imaging device 1, and only captures an image of the abnormality with the camera 35 when it is found. That is, when visually observing a living organism's test tissue with the naked eye, a higher illumination light intensity improves visibility, but if the test tissue is photographed with the camera 35 while the illumination light intensity is high, the amount of light received by the image sensor 32 of the camera 35 exceeds its limit, causing excessively bright areas in the captured image to appear white, a phenomenon known as blown-out highlights. Therefore, by reducing the illumination light intensity (automatically adjusting the illumination light intensity) so as not to exceed the limit of the light received by the image sensor 32 of the camera 35 when photographing the test tissue, it is possible to reduce blown-out highlights.

[0039] Alternatively, as a modified example, the control circuit 60 may reduce the amount of excitation light when the shutter switch 34 is half-pressed, control the imaging device 35 to capture an image of the test tissue when the shutter switch 34 is fully pressed, and restore the amount of excitation light from the LED 20 to the original amount, including the maximum amount, when the shutter switch 34 is fully released and imaging by the imaging device 35 is completed. Alternatively, the control circuit 60 may have a first control mode in which the LED 20 emits excitation light at a first light amount, a second control mode in which the LED 20 emits excitation light at a second light amount that is less than the first light amount, and a third control mode in which the imaging device 35 is controlled to emit excitation light at the second light amount that is less than the first light amount and capture an image of the test tissue, and switch between the three control modes depending on the operation of the shutter switch 34.

[0040] When examining the intraoral tissue of a subject using the oral cavity imaging device 1 configured as described above, an operator (examiner) such as a doctor first observes the living body with the naked eye (searching for abnormalities) using the illumination (excitation light) of the oral cavity imaging device 1. Specifically, the operator holds the first tube portion 10A in his / her hand, points the irradiation port 30Ca of the illumination / light-receiving unit 10C into the oral cavity 80 of the subject (see FIG. 3), and observes the tissue at a position approximately 150 mm away from the center of the mirror 24. At this stage (or before pointing the irradiation port 30Ca toward the oral cavity 80), if the power switch is turned on, as shown in FIG. 3, the blue excitation light emitted from the excitation light source 20, with light of other wavelengths completely filtered out by the filter 26, travels in the X direction along the emission optical axis O1 (along the longitudinal direction of the first tube portion 10A), strikes the mirror 24 at a 45° angle, is reflected by the mirror 24, and is guided into the oral cavity 80 of the subject in the Y direction along the irradiation optical axis O2. Needless to say, in this case, the excitation light L1 is guided as a bundle of rays as shown in Fig. 5. At this time, the light emission amount of the LED 20 is controlled to the maximum light amount as a preferable brightness.

[0041] If an abnormality is found in the living body through such an examination, the operator will photograph the abnormality with camera 35. Specifically, the operator presses shutter switch 34 while pointing irradiation port 30Ca of illumination / light-receiving unit 10C toward the abnormality. When shutter switch 34 is half-pressed, the amount of illumination light (amount of excitation light) is automatically reduced, and when shutter switch 34 is released, imaging device (camera) 35 takes an image.

[0042] In this case, the test tissue is irradiated and excited by the excitation light L1, and emits fluorescence. This fluorescence enters the device 1 in the Y direction along the optical axis O3 of the imaging optical system (lens unit 30 and image sensor 32) of the imaging device 35 through the irradiation port 30Ca of the illumination / light-receiving unit 10C. Of the incident fluorescence, blue light L1' is reflected by the mirror 24, while fluorescence L2 of other wavelengths is transmitted by the mirror 24 and guided to the imaging device 35. Then, after the slight blue light L1' is safely removed by the filter 28, this transmitted light (fluorescence) is focused onto the image sensor 32 via the lens unit 30 and converted into an electrical signal. If the test tissue is healthy, it emits green fluorescence, but lesions such as oral cancer do not emit green fluorescence. Therefore, oral cancer, etc. can be identified by analyzing the captured image based on the fluorescence that reaches the image sensor 32. In FIG. 3, for the sake of clarity, the illumination optical axis O2 and the optical axis O3 of the imaging optical system are drawn parallel to each other and not coincident with each other, but as mentioned above, these optical axes O2 and O3 coincide with each other.

[0043] As described above, according to the oral cavity photographing device 1 of this embodiment, the LED 20 emits light at the maximum light intensity when not photographing (when observing with the naked eye), and the amount of illumination light for the living body is automatically adjusted when photographing.In other words, when photographing the test area, the amount of illumination light is reduced so as not to exceed the limit of the amount of light received by the camera's imaging unit, so that the illumination light intensity when visually observing can be ensured and whiteout can be reduced with simple operations.

[0044] Furthermore, according to the oral cavity imaging device 1 of this embodiment, the optical axis O3 of the imaging optical system of the imaging device 35 is substantially aligned with the optical axis O2 of the excitation light, or the incident direction of the fluorescence that passes through the mirror 24 and enters the imaging device 35 is substantially aligned with the irradiation direction of the excitation light that is reflected by the mirror 24 and directed toward the test tissue. Furthermore, the optical axis O3 of the imaging optical system of the imaging device 35 is positioned so that the imaging optical system can receive the fluorescence at an intensity of 50% or more of its maximum intensity. Therefore, clear images with good contrast of the test tissue can be obtained. In particular, as described above, the adoption of a configuration in which the optical elements essential for examination are efficiently built into a compact housing provides excellent operability, allowing test tissue to be captured simply and clearly without complex initial setup, such as camera angle setting. Therefore, dentists who frequently observe patients' oral cavity interiors can easily perform screening between treatments.

[0045] While the present invention has been described above in connection with various embodiments, it is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention. For example, in the present invention, the configurations of the device components and the shapes of the lenses and mirrors are not limited to those of the above-described embodiments. Furthermore, while the above-described embodiments are configured to capture still images using a camera, the camera may also be capable of capturing video in reduced light conditions. Furthermore, some or all of the above-described embodiments may be combined, or some components may be omitted from one of the above-described embodiments, without departing from the spirit of the present invention. [Explanation of symbols]

[0046] 1 Oral cavity imaging device 20 Excitation light source 24. Mirror 34 Shutter switch 35 Imaging device 60 Control circuit

Claims

1. an excitation light source that emits excitation light in a predetermined wavelength range that excites test tissue in the oral cavity; an imaging device that images the test tissue by receiving fluorescence emitted from the test tissue that has been irradiated and excited by the excitation light; a mirror that reflects the excitation light emitted from the excitation light source and directs it toward the test tissue, and that reflects light within the predetermined wavelength range among the fluorescence emitted by the test tissue and transmits other fluorescence; Equipped with An oral cavity imaging device characterized in that the optical axis of the imaging optical system of the imaging device and the irradiation optical axis of the excitation light reflected by the mirror and directed toward the test tissue are approximately aligned.

2. an excitation light source that emits excitation light in a predetermined wavelength range that excites test tissue in the oral cavity; an imaging device that images the test tissue by receiving fluorescence emitted from the test tissue that has been irradiated and excited by the excitation light; a mirror that reflects the excitation light emitted from the excitation light source and directs it toward the test tissue, and that reflects light within the predetermined wavelength range among the fluorescence emitted by the test tissue and transmits other fluorescence; Equipped with An oral cavity imaging device characterized in that the incident direction of the fluorescence that passes through the mirror and enters the imaging device is approximately the same as the irradiation direction of the excitation light that is reflected by the mirror and directed toward the test tissue.

3. an excitation light source that emits excitation light in a predetermined wavelength range that excites test tissue in the oral cavity; an imaging device that images the test tissue by receiving fluorescence emitted from the test tissue that has been irradiated and excited by the excitation light; a mirror that reflects the excitation light emitted from the excitation light source and directs it toward the test tissue, and that reflects light within the predetermined wavelength range among the fluorescence emitted by the test tissue and transmits other fluorescence; Equipped with An oral cavity imaging device characterized in that the optical axis of the imaging optical system of the imaging device is positioned so that the imaging optical system can receive the fluorescent light at an amount of light that is 50% or more of its maximum amount.

4. An oral cavity imaging device as described in any one of claims 1 to 3, characterized in that the mirror reflects light with a wavelength of less than 500 nm that is incident on the mirror at an incident angle of approximately 45° as excitation light in the specified wavelength range, and transmits light with a wavelength of 500 nm or more as the other fluorescence.

5. the mirror is positioned so as to diagonally cross an optical path of the fluorescence emitted from the test tissue toward the imaging device and an optical path of the excitation light emitted from the excitation light source; an optical axis of the excitation light emitted from the excitation light source and directed toward the mirror is substantially perpendicular to an optical axis of the imaging optical system of the imaging device; The oral cavity photographing device according to any one of claims 1 to 3.

6. The oral cavity imaging device according to claim 1 , further comprising a control circuit for controlling the excitation light source and the imaging device, wherein the control circuit is capable of adjusting the amount of the excitation light emitted from the excitation light source.

7. a shutter switch for driving a shutter that controls exposure to an imaging unit of the imaging device; the control circuit controls the excitation light source to adjust the amount of excitation light when the shutter switch is switched from a switch OFF state in which the imaging unit is not exposed to light to a switch ON state in which the imaging unit is exposed to light, and controls the imaging device to image the test tissue when the switch is switched from the switch ON to the switch OFF. The oral cavity photographing apparatus according to claim 6 .

8. 8. The oral cavity photographing device according to claim 7, wherein, when the switch is ON, the control circuit reduces the amount of the excitation light when the shutter switch is half-pressed.

9. The oral cavity photographing device according to claim 7, wherein the control circuit controls the imaging device to reduce the amount of excitation light when the shutter switch is pressed, and to capture an image of the test tissue when the shutter switch is released.

10. The oral cavity photographing device of claim 7, wherein the control circuit controls the imaging device to reduce the amount of excitation light when the shutter switch is half-pressed, to image the test tissue when the shutter switch is fully pressed, and to return the amount of excitation light to its original amount, including the maximum amount, when the shutter switch is completely released and photographing by the imaging device is completed.

11. a control circuit for controlling the excitation light source and the imaging device, and a shutter switch for driving a shutter that controls exposure of an imaging unit of the imaging device, The oral cavity imaging device according to any one of claims 1 to 3, characterized in that the control circuit has a first control mode in which excitation light is emitted from the excitation light source at a first light amount, a second control mode in which excitation light is emitted from the excitation light source at a second light amount that is less than the first light amount, and a third control mode in which the control circuit controls the imaging device to emit excitation light from the excitation light source at the second light amount that is less than the first light amount and to image the test tissue, and switches between the three control modes in response to operation of the shutter switch.

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