JP7440860B2 - Crystalline lens transmission spectrum estimation system and crystalline lens transmission spectrum estimation method - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act [1] Published in VISION Vol. 31, No. 1, Visual Society of Japan 2019 Winter Conference Abstracts, Page 34 (Published by Visual Society of Japan, Publication date: January 20, 2019) [2] Presented at the 2019 Winter Conference of the Vision Society of Japan (Date: January 29 to January 31, 2019, hosted by the Visual Society of Japan, Opening date: January 30, 2019)

The present invention relates to a crystalline lens transmission spectrum estimation system and a crystalline lens transmission spectrum estimation method.

It is known that the optical density of the crystalline lens of the human eye (hereinafter simply referred to as crystalline lens) increases with age. Age-related changes in the optical density of the crystalline lens are thought to affect visual functions such as how colors are perceived and non-visual functions such as adjustment of daily rhythm. Therefore, various techniques have been proposed to easily measure the optical density of the crystalline lens according to age.

For example, Patent Document 1 discloses a device that evaluates the glare of a light source felt by a person to be measured (hereinafter sometimes simply referred to as the person). The device disclosed in Patent Document 1 acquires the transmission characteristics of the crystalline lens of the subject's eye, and determines the transmission characteristics of the subject's eye based on the spectrum of the light emitted from the light source and the transmission characteristics acquired as described above. Calculate the spectrum of light that reaches the retina. Thereafter, the device disclosed in Patent Document 1 calculates and outputs an index representing the glare of the light source felt by the subject based on the above-mentioned light spectrum.

Patent Document 2 discloses an apparatus that easily measures the spectral sensitivity characteristics of the human eye. The device disclosed in Patent Document 2 uses a plurality of light sources irradiated from a measurement light source based on the spectral luminous efficiency of an average observer, which is classified according to age group, degree of progression of symptoms, etc. The light intensity ratio between different colored lights that is perceived as equibright by an average observer of the same classification is derived. Next, in the device disclosed in Patent Document 2, the test subject observes the light in which the light intensity ratio is changed using the different colored lights, and when the test subject reports that the light seems to be of equal brightness, the calculation is performed as described above. Based on the classification correspondence data created in advance from the light intensity ratio between the colored lights, the subject is sorted into the corresponding classification. Thereafter, the subject's spectral sensitivity characteristics are estimated from the assigned classifications.

Japanese Patent Application Publication No. 2008-093131 JP2008-237492A

However, with conventional devices such as the devices disclosed in Patent Documents 1 and 2 mentioned above, when determining the optical density of the crystalline lens according to the age of the subject, they rely on the senses and responses of the subject, and errors due to senses occur. In some cases, the optical density of the crystalline lens could not be determined because measurements could not be performed when the subject had difficulty responding.

The present invention has been made in view of the above-mentioned circumstances, and provides a crystalline lens transmission spectrum estimation system and a crystalline lens transmission spectrum estimation method for easily determining the optical density of the crystalline lens without relying on the senses of a subject. do.

The present invention includes the following aspects.
[1] The brightness of images of a plurality of mutually different wavelengths formed by the crystalline lens is measured as an actual luminance for each of the plurality of mutually different wavelengths, and the size of the image is measured as an actual size for each of the plurality of mutually different wavelengths. a ratio of the measured brightness of each of the plurality of mutually different wavelengths to a reference brightness obtained in advance for each of the plurality of mutually different wavelengths, and a ratio of the measured brightness of each of the plurality of mutually different wavelengths; an optical density calculation unit that calculates the measured optical density of the crystalline lens at each of the plurality of mutually different wavelengths based on a ratio between the measured size and a reference size obtained in advance for each of the plurality of mutually different wavelengths; an optical density that satisfies a predetermined condition for the measured optical density at each of the plurality of mutually different wavelengths and estimates a known optical density obtained in advance for a predetermined wavelength range that includes the plurality of mutually different wavelengths as an estimated optical density; A transmission spectrum of a crystalline lens, comprising: an estimation section; and a spectrum calculation section that calculates the transmittance of the crystalline lens in the predetermined wavelength range as a transmission spectrum of the crystalline lens based on the estimated optical density in the predetermined wavelength range. Estimation system.
[2] The known optical density obtained in advance for the predetermined wavelength range is calculated based on the crystalline lens age of the crystalline lens for each wavelength within the predetermined wavelength range and a predetermined coefficient according to the crystalline lens age. , the transmission spectrum estimation system for a crystalline lens according to [1].
[3] The transmission spectrum estimation system for a crystalline lens according to [1] or [2], wherein the image is an image formed by reflection on a surface of the crystalline lens that is adjacent to the vitreous body.
[4] The transmission spectrum of the crystalline lens according to any one of [1] to [3], wherein the plurality of mutually different wavelengths include 600 nm and at least one wavelength within a wavelength band of 400 nm or more and less than 600 nm. Estimation system.
[5] The crystalline lens transmission spectrum estimation system according to any one of [1] to [4], further comprising a light source that irradiates the crystalline lens with the plurality of lights of different wavelengths.
[6] The transmission spectrum estimation system for a crystalline lens according to any one of [1] to [5], wherein a gaze object is placed within the field of view of an eye having the crystalline lens .
[7] The brightness of images of a plurality of mutually different wavelengths formed by the crystalline lens is measured as an actual luminance for each of the plurality of mutually different wavelengths, and the size of the image is measured as an actual size for each of the plurality of mutually different wavelengths. and a ratio between the measured brightness of each of the plurality of mutually different wavelengths and a reference brightness obtained in advance for each of the plurality of mutually different wavelengths, the measured size of each of the plurality of mutually different wavelengths, and the plurality of and a reference size obtained in advance for each of the different wavelengths, calculate the measured optical density of the crystalline lens at each of the plurality of different wavelengths, and calculate the actual measured optical density at each of the plurality of different wavelengths. The difference between the optical density and a predetermined known optical density obtained in advance including the plurality of mutually different wavelengths among the known optical densities obtained in advance for a predetermined wavelength range including the plurality of mutually different wavelengths is the smallest. estimating the known optical density as an estimated optical density, and calculating the transmittance of the crystalline lens in the predetermined wavelength range as a transmission spectrum of the crystalline lens based on the estimated optical density in the predetermined wavelength range; A method for estimating the transmission spectrum of the crystalline lens.

According to the above-described inspection illumination device and inspection apparatus, an inspector can separate and visually recognize the hue of the specularly reflected light from the inspection target section, regardless of the shape of the inspection target section.

FIG. 1 is a schematic diagram of a lens transmission spectrum estimation system (estimation system) according to an embodiment of the present invention. FIG. 2 is a side view for explaining the principle of forming a Purkinje image in the estimation system shown in FIG. 1. FIG. 3 is a schematic diagram for explaining the brightness and size of a Purkinje image in the estimation system shown in FIG. 1. FIG. 4 is a schematic diagram different from FIG. 1 of an estimation system according to an embodiment of the present invention. FIG. 5 is a block diagram regarding the optical density calculation section, optical density estimation section, and spectrum calculation section of the estimation system shown in FIG. 1. FIG. 6 is a schematic diagram of a part of the transmittance spectrum estimation system in the example. FIG. 7 is a photograph of the Purkinje image obtained in the example. FIG. 8 is a graph showing the distribution of actually measured optical densities of crystalline lenses of a plurality of subjects calculated in Examples. FIG. 9 is a graph showing estimated optical densities estimated for each age group in Examples. FIG. 10 is a graph showing transmission spectra for each age group estimated in the example.

Hereinafter, preferred embodiments of a crystalline lens transmission spectrum estimation system and a crystalline lens transmission spectrum estimation method according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, a crystalline lens transmission spectrum estimation system 10 (hereinafter sometimes simply referred to as estimation system 10) according to an embodiment of the present invention includes an image data measurement section 20, an optical density calculation section 50, , an optical density estimation section 60, and a spectrum calculation section 70.

The image data measuring unit 20 measures the brightness and size of the Purkinje images 120 of a plurality of different wavelengths formed by the crystalline lens 310 as actual brightness and actual size for each of the plurality of mutually different wavelengths. The Purkinje image 120 is an image reflected by the surface of the cornea or crystalline lens.

Generally, there are multiple types of Purkinje images 120. The plurality of types of Purkinje images include, for example, as shown in FIG. 2, a first Purkinje image 121 to a fourth Purkinje image 124. The first Purkinje image 121 is the reflected light 202 when the incident light 200 that entered the eye of the subject (not shown) is reflected by the surface 302a of the cornea 302 of the subject's eye on the near side in the direction of incidence of the incident light 200. It is an image formed by The second Purkinje image 122 is an image formed by reflected light 204 when transmitted light 205 transmitted through the surface 302a of the cornea 302 is reflected by the surface 302b on the back side of the cornea 302 in the direction of incidence of the incident light 200. . The first Purkinje image 121 and the second Purkinje image 122 are not reversed with respect to the projected image 130 in the vertical direction and in the horizontal direction perpendicular to the vertical direction, and are oriented in the same direction. In addition, in FIG. 2, the first Purkinje image 121 and the second Purkinje image 122 are illustrated as being superimposed on each other.

The third Purkinje image 123 is an image formed by reflected light 206 when transmitted light 210 transmitted through the surface 302b of the cornea 302 is reflected by the surface 310a on the near side of the crystalline lens 310 in the direction of incidence of the incident light 200. . The third Purkinje image 123 is not reversed in the vertical direction and in the horizontal direction perpendicular to the vertical direction with respect to the projected image 130, and is oriented in the same direction. The fourth Purkinje image 124 is an image formed by reflected light 208 when transmitted light 215 transmitted through the surface 310a of the crystalline lens 310 is reflected by the surface 310b on the back side of the crystalline lens 310 in the direction of incidence of the incident light 200. . The fourth Purkinje image 124 is inverted with respect to the projected image 130 in the vertical direction and in the horizontal direction orthogonal to the vertical direction, and is oriented in opposite directions.

The image data measurement unit 20 measures the brightness and size of the fourth Purkinje image 124. As shown in FIG. 2, the reflected light 204 is tilted relative to the reflected light 202 because it is refracted through the surface 302a after exiting the surface 302b of the cornea 302. However, since the cornea 302 is very thin (for example, thinner than the maximum thickness of the crystalline lens 310), the reflected lights 202 and 204 can be said to be substantially parallel to each other. On the other hand, after the reflected light 208 is emitted from the surface 310b of the crystalline lens 310, it is refracted each time it sequentially passes through the surface 310a and the surfaces 302b and 302a of the cornea 302. Therefore, reflected light 208 is more inclined with respect to reflected light 202 than reflected lights 202, 204, and 206. In other words, the angle θ4 between the reflected light 208 (hereinafter simply referred to as reflected light 208) that has exited the surface 302a of the cornea 302 and the incident light 200 is the angle θ4 between the other reflected lights 202, 204, and the surface 302a of the cornea 302. Each of the reflected lights 206 is larger than each of the angles (not shown) made with the incident light 200.

The crystalline lens 310 is adjacent to the vitreous body 330. The vitreous body 330 is located on the back side of the crystalline lens 310 in the direction of incidence of the incident light 200. That is, the fourth Purkinje image 124 is an image formed by reflection on the surface 310b of the crystalline lens 310 adjacent to the vitreous body 330.

As shown in FIG. 1, the image data measurement unit 20 includes, for example, a light source 22, an optical fiber 24, a shaping filter 28, and an imaging camera 30. The light source 22 emits polychromatic light including at least a plurality of mutually different wavelengths. The input end of the optical fiber 24 is connected to the output part of the light source 22. The light source 22 includes, for example, a xenon lamp (not shown) capable of emitting white light as polychromatic light, and a bandpass filter. As the bandpass filter inside the light source 22 rotates, a plurality of lights IL1, ..., ILm having different wavelengths λ1, ..., λm among the polychromatic lights of the xenon lamp are transmitted through the bandpass filter, The light is input into the optical fiber 24 and output from the output end 25 of the optical fiber 24. m represents the number of a plurality of mutually different wavelengths, and is a natural number of 2 or more. It is preferable that the wavelengths λ1, . . . , λm include 600 nm and at least one wavelength within a wavelength band of 400 nm or more and less than 600 nm.

The shaping filter 28 has a plate surface substantially perpendicular to the optical axis (broken line in FIG. 1) of the lights IL1, . . . , ILm emitted from the output end 25 of the optical fiber 24. It is provided at a position away from the output end 25. A hole having a diameter of, for example, about 3 mm is formed in the center portion of the molding filter 28. The lights IL1, . . . , ILm pass through holes formed in the shaping filter 28 and are shaped into a predetermined shape. The lights IL1, . . . , ILm are irradiated onto the eye 350 of the measurement target placed on the path.

The imaging camera 30 receives the reflected lights RL1, . ..., 124-m is imaged. Information regarding the fourth Purkinje images 124-1, . . . , 124-m captured by the imaging camera 30 is transmitted to a computer 40 such as a personal computer via a cable.

The calculator 40 includes an optical density calculation section 50, an optical density estimation section 60, and a spectrum calculation section 70. However, in FIG. 1 and FIG. 3 described later, the optical density calculation section 50, optical density estimation section 60, spectrum calculation section 70, and crystalline lens 310 are omitted.

The optical density calculation unit 50 measures the brightness of the fourth Purkinje images 124-1, . . . , 124-m formed by the crystalline lens 310 and captured by the imaging camera 30 as actual brightness. Further, the optical density calculation unit 50 measures the sizes of the fourth Purkinje images 124-1, . . . , 124-m as actual sizes. For example, the measured brightness of the fourth Purkinje images 124-1, ..., 124-m is the average value of brightness within the range of each of the fourth Purkinje images 124-1, ..., 124-m. be. Similarly, the measured size of the fourth Purkinje images 124-1, . . . , 124-m is the position corresponding to 1/2 of the vertical axis when the maximum value of the vertical axis of the profile illustrated in FIG. This is the width of the profile (distance to the actual measurement position), and is the so-called full width at half maximum (FWHM) of the profile illustrated in FIG. Furthermore, the actual size of the fourth Purkinje images 124-1, . . . , 124-m corresponds to 1/e ² of the vertical axis when the maximum value of the vertical axis of the profile illustrated in FIG. It may also be the width of the profile at the position (distance from the actually measured position).

The optical density calculation unit 50 calculates the measured brightness and the measured size of the fourth Purkinje images 124-1, ..., 124-m of the eye whose optical density is substantially constant regardless of the wavelengths λ1, ..., λm. Information on the reference brightness and reference size calculated using the same calculation method as each of the above is obtained in advance. The optical density calculation unit 50 calculates the density based on the ratio between the measured brightness of each of the wavelengths λ1, ..., λm and the reference brightness, and the ratio of the measured size and the reference size of each of the wavelengths λ1, ..., λm. Then, the measured optical densities AD _media (λ1), . . . , AD _media (λm) at each of the wavelengths λ1, . . . , λm are calculated.

The optical density calculation unit 50 calculates a plurality of known optical density distributions for each of the wavelengths λ1, . Information on the concentrations FD _media (λ1), . . . , FD _media (λm) is obtained in advance. The predetermined wavelength range is, for example, a wavelength band of visible light, and is in the range of 380 nm or more and 780 nm or less. The plurality of known optical density distributions are, for example, optical density distributions depending on the age of the subject. The optical density calculation unit 50 selects a known optical density FD _media (λk) that has the smallest difference from the measured optical density AD _media (λk) among the plurality of known optical densities FD _media (λk) as an estimated optical density ED _media ( λ). k is a natural number from 1 to m.

The spectrum calculation unit 70 calculates the transmittance T(λk) of the crystalline lens 310 in a predetermined wavelength range as the transmission spectrum T(λ) of the crystalline lens 310 based on the estimated optical density ED _media (λ) in the predetermined wavelength range.

The optical density calculation section 50, the optical density estimation section 60, and the spectrum calculation section 70 are configured as programs that execute respective processing contents, and are built into the computer 40.

A crystalline lens transmission spectrum estimation method according to an embodiment of the present invention includes the first to fifth steps described below.

In the first step, using the image data measurement unit 20, the optical density (to be distinguished from the known optical density, it is referred to as absolute optical density) in a predetermined wavelength range ZD _media (λk) is determined in advance at the wavelength λ1,... , λm (having a known optical density) is set at the position of the eye 350 in FIG. The eye 350 is irradiated with the incident light ILk. Subsequently, the imaging camera 30 receives the reflected light RLk and images the fourth Purkinje image 124-k. Here, the fourth Purkinje image 124-k of the simulated eye is referred to as Purkinje image Ref[124-k]. Information regarding the Purkinje image Ref[124-k] captured by the imaging camera 30 is transmitted to the optical density calculation unit 50 of the computer 40.

In the optical density calculation unit 50, the Purkinje image Ref[124-k] is expressed as a profile plotted on a graph in which the horizontal axis is the measured position and the vertical axis is the luminance as shown in FIG. 3, and the maximum value and full width at half maximum of the profile are are determined, and are respectively defined as a reference brightness FL (λk) and a reference size FW (λk). Note that the actually measured position of the profile described above is expressed by the number of pixels of the imaging camera 30. The brightness of the profile described above is represented by the brightness, or gradation, of each pixel of the imaging camera 30. Each pixel of the imaging camera 30 and its actual size are calibrated, and the brightness or gradation of each pixel of the imaging camera 30 and the brightness of light incident on the imaging camera 30 are also calibrated. The obtained reference brightness FL (λk) and reference size FW (λk) are stored in the storage unit 45 of the computer 40, an arbitrary database, or the like.

Next, in the second step, the luminance of the fourth Purkinje image 124-k of a plurality of mutually different wavelengths λk formed by the crystalline lens 310 is measured as the actual luminance AL(λk) for each of the plurality of wavelengths λk, The size of the Purkinje image 124-k is measured as an actual size AW(λk) for each of a plurality of wavelengths λk.

To explain in detail, the subject's eye is set at the position of the eye 360 in FIG. 4, and the gaze object 90 is placed within the field of view of the eye 360 as shown in FIG. That is, in the estimation system 10, the gaze object 90 is placed behind the crystalline lens 310 in the direction of incidence of the incident light (a plurality of lights of different wavelengths) ILk.

Subsequently, using the image data measurement unit 20, the shaping filter 28 is activated to irradiate the eye 350 with the incident light ILk, similarly to the first step. The imaging camera 30 receives the reflected light RLk and captures a fourth Purkinje image 124-k. Here, the fourth Purkinje image 124-k of the subject's eye is referred to as Purkinje image Meas[124-k]. Information regarding the Purkinje image Meas[124-k] captured by the imaging camera 30 is transmitted to the optical density calculation unit 50 of the computer 40.

Next, the Purkinje image Meas[124-k] is expressed as a profile plotted on a graph where the horizontal axis is the measured position and the vertical axis is the brightness as shown in FIG. 3, and the maximum value and full width at half maximum of the profile are determined. Let them be measured luminance AL (λk) and measured size AW (λk), respectively.

Next, in the third step, as shown in FIG. k) and the ratio between the measured size AW (λk) of each of the plurality of wavelengths λk and the reference size FW (λk) obtained in advance, the plurality of wavelengths of the crystalline lens 310 of the subject's eye. The measured optical density AD _media (λk) at each of λk is calculated.

To explain in detail, the optical density calculation unit 50 calculates the actual measurement from the actual measurement brightness AL (λk), the reference brightness FL (λk), the actual measurement size AW (λk), and the reference size FW (λk) using the following equation (1). Calculate the optical density AD _media (λk).

Next, in the fourth step, the optical density estimating unit 60 calculates the measured optical densities AD _media (λk) of each of the plurality of wavelengths λk and one or more types of known optical densities FD _media obtained in advance for a predetermined wavelength range. (λk), the type of known optical density FD _media (λk) that “has the smallest difference from the measured optical density AD _media (λk)” is estimated as the estimated optical density ED _media (λ) under a predetermined condition.

To explain in detail, for example, one or more kinds of known optical densities FD _media (λk) obtained in advance are obtained based on psychological/physical methods (for example, see J. van de Kraats et al., 2007). ). This known optical density FD _media (λk) is determined by the coefficients of two predetermined groups: the coefficients of the first group {d _RL (age), d _TP (age), d _LY (age), d _LOUV (age), d _LO (age), d _neutral }, and the coefficients of the second group {M _RL (λ), M _TP (λ), M _LY (λ), M _LOUV (λ), M _LO (λ)}, as shown below. It is expressed as in equation (2).

By substituting each wavelength λk (k=1 to m) for the wavelength λ in equation (2), the known optical density FD _media (λk) for each wavelength λk is obtained. As can be seen from equation (2), when the variable age is changed, the same number of known optical densities FD _media (λk) as the number of changed ages is obtained. Therefore, for each wavelength λk, the age of the known optical density FD _media (λk) that has the smallest difference from the measured optical density AD _media (λk) is calculated, and the age is set as the crystalline lens age AGE. The optical density estimation unit 60 substitutes the lens age AGE into the age in equation (2) to estimate the estimated optical density ED _media (λ).

Next, in the fifth step, the optical density estimation unit 60 calculates the transmittance T (λ) of the crystalline lens 310 of the eye 360 in a predetermined wavelength range based on the estimated optical density ED _media (λ) in a predetermined wavelength range. It is calculated as a transmission spectrum of 310.

To explain in detail, the optical density estimating unit 60 substitutes the estimated age AGE for the age in equation (2), and calculates the known optical density FD _media (λk) in which all the coefficients of the first group are constants as the estimated optical density ED _media (λ). The estimated optical density ED _media (λ) is a function determined only by an arbitrary wavelength λ. The transmittance T(λ) is expressed by the estimated optical density ED _media (λ) as shown in the following equation (3).

If the predetermined wavelength range is the wavelength band of visible light as described above, and is in the range of 380 nm or more and 780 nm or less, then the horizontal axis is at least the wavelength from 380 nm to 780 nm, and the vertical axis is expressed by equation (3). When the transmittance T(λ) is plotted, the transmission spectrum of the crystalline lens 310 is illustrated.

By performing each of the above steps, the transmission spectrum of the crystalline lens 310 of the subject's eye 360 is calculated for at least an arbitrary wavelength λ included in a predetermined wavelength range.

According to the estimation system 10 of the present embodiment described above, the optical density calculation unit 50, the optical density estimation section 60 and the spectrum calculation section 70 each calculate the transmittance T(λ) of the crystalline lens 310 at an arbitrary wavelength λ, that is, the transmission spectrum of the crystalline lens 310. That is, as long as the eye 360 can be irradiated with light of a plurality of wavelengths λk and the Purkinje image Meas[124-k] can be captured, the transmission spectrum of the crystalline lens 310 can be easily calculated without relying on the subject's senses.

Further, according to the estimation system 10 of the present embodiment, the known optical density FD _media (λk) is calculated based on the lens age AGE of the crystalline lens 310 for each wavelength λk within the predetermined wavelength range and the first group according to the crystalline lens age AGE. is calculated based on the coefficients (predetermined coefficients) {d _RL (AGE), d _TP (AGE), d _LY (AGE), d _LOUV (AGE), d _LO (AGE), d _neutral }. That is, if the measured luminance AL (λk) and the measured size AW (λk) are obtained from the Purkinje image Meas[124-k], the lens age AGE of the crystalline lens 310 is calculated according to the above-mentioned equations (1) to (3). At the same time, the transmission spectrum of the crystalline lens 310 can be easily calculated.

Further, according to the estimation system 10 of the present embodiment, the Purkinje images Meas[124-k] and Ref[124-k] are formed by reflection on the surface 310b adjacent to the vitreous body 330 among the surfaces of the crystalline lens 310. It is a statue of Therefore, the optical density of the crystalline lens 310 is well reflected in both the measured brightness AL (λk) and the measured size AW (λk) of the Purkinje image Meas[124-k], and the estimated optical density ED _media (λ) and the measured size AW (λk) of the crystalline lens 310 are well reflected. Transmission spectra can be calculated with high accuracy. Further, as illustrated in FIGS. 1 and 3, the angle θ4 between the optical axis of the incident light ILk and the optical axis of the reflected light RLk can be ensured. This makes it easier to arrange the light source 22, optical fiber 24, shaping filter 28, and imaging camera 30 of the image data measurement section 20.

Further, according to the estimation system 10 of the present embodiment, the plurality of mutually different wavelengths λk include 600 nm and at least one wavelength within a wavelength band of 400 nm or more and less than 600 nm. In this case, the plurality of wavelengths λk include, for example, 600 nm, which is the reference wavelength, and a wavelength range shorter than 600 nm (that is, a range where the optical density is high and changes with age are large). Therefore, in the wavelength range with high optical density, the lens age AGE of the crystalline lens 310 and the transmission spectrum of the crystalline lens 310 can be calculated more accurately than when using other wavelength ranges. Note that if the wavelength is about 600 nm, the change in the optical density of the crystalline lens with age is small and the difference in optical density with age is close to zero, so basically it is preferable to set the reference wavelength to a visible wavelength of 600 nm or more. However, the reference wavelength may be changed as appropriate depending on the conditions of the subject.

Further, according to the estimation system 10 of the present embodiment, by further including the light source 22 that irradiates the incident light ILk of a plurality of wavelengths λk toward the crystalline lens 310, light sources etc. are prepared individually for the plurality of wavelengths λk. It is simple and space-saving.

Furthermore, according to the estimation system 10 of the present embodiment, Purkinje images Meas[124-k] of a plurality of wavelengths λk are formed on the rear side of the crystalline lens 310 in the direction of incidence of the incident light ILk of a plurality of wavelengths λk. Since the gaze object 90 is placed, when capturing the Purkinje image Meas[124-k], the movement of the crystalline lens 310 is substantially stopped, the Purkinje image Meas[124-k] is stabilized, and the variations among the plurality of wavelengths λk are reduced. and errors can be suppressed.

Further, according to the transmission spectrum estimation method of the crystalline lens of the present embodiment, at least the second to fifth steps are performed using the estimation system 10 described above, and the crystalline lens 310 can be easily estimated without relying on the subject's senses. The transmission spectrum of can be calculated.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments. The present invention can be modified within the scope of the invention as defined in the claims.

For example, in each of the embodiments described above, the number of the plurality of mutually different wavelengths may be at least two, preferably about eight, but is not particularly limited as long as it is two or more. Furthermore, in the above embodiment, the known optical density FD _media (λk) expressed by equation (2) was used; however, if the optical density is expressed as a function of an arbitrary wavelength, (2 ) can be used without being limited to what is expressed by the formula.

In addition, the estimation system 10 described above includes a light source 22 that can emit light of a plurality of wavelengths λ1, ..., λm, and an imaging camera that can acquire Purkinje images for each wavelength λ1, ..., λm. 30 and the distance between the light source 22 and the imaging camera 30 and the eyes 350 and 360 is not particularly limited as long as the angle θ4 between the traveling direction of the incident light ILk emitted from the light source 22 and the imaging direction of the imaging camera 30 can be secured. , the relative placement of the light source 22 and the imaging camera 30 with respect to the eyes 350, 360 is not limited. For example, the light source 22 and the imaging camera 30 may be provided inside the head-mounted display, that is, inside the casing of the head-mounted display, in a relative arrangement that ensures the angle θ4.

Furthermore, in the above estimation system 10 and crystalline lens transmission spectrum estimation method, the acquisition time of the Purkinje image depends on the time for emitting the incident light ILk of mutually different wavelengths from the light source 22. As the rotation time (i.e., switching time) of the bandpass filter in the light source 22 is shortened and the frame rate of the imaging camera 30 is shortened accordingly, the acquisition time of the Purkinje image can be shortened, and the transmission spectrum of the crystalline lens can be obtained more quickly. It can be estimated.

In the crystalline lens transmission spectrum estimation method of the embodiment described above, the brightness and size of the fourth Purkinje image of the simulated eye at each wavelength λk were obtained as an example of the reference brightness FL (λk) and the reference size (λk). However, in the method for estimating the transmission spectrum of a crystalline lens according to the present invention, the reference brightness FL (λk) and the reference size (λk) may be anything that makes it possible to calculate the actual measured optical density AD _media (λk), and It is not limited to the brightness and size of the fourth Purkinje image. Since the measured optical density AD _media (λk) is a physical quantity that indicates how much the intensity of light of each wavelength λk incident on the eye is attenuated before being reflected as, for example, the fourth Purkinje image, the reference brightness FL (λk) The reference size (λk) may be the brightness and size of an image formed by an image whose optical density is approximately constant regardless of the wavelength in a predetermined wavelength band including a plurality of wavelengths λ1 to λm. It may be the brightness and size of an image formed by a member having a predetermined optical density in a wavelength band.

In the estimation system 10 described above, the light emitted from the light source 22 is guided by the optical fiber 24, and is emitted from the optical fiber 24 as incident light ILk to the eyes 350, 360. However, as long as the fourth Purkinje image 124 can be photographed, the configuration for making the incident light ILk of a plurality of wavelengths enter the eyes 350 and 360 in the estimation system 10 is not particularly limited. For example, if the light source 22 is provided with an LED that emits light of wavelengths λ1, . Further, by using an LED as the light source 22, the intensity of the light emitted from the light source 22 can be appropriately lowered, so a cover member, a filter with holes, etc. may be unnecessary. This allows the estimation system 10 to be downsized.

Next, examples of the present invention will be described. Note that the present invention is not limited to the following examples.

In this example, the estimation system 10 described in FIGS. 1 and 4 was prototyped. In the prototype, a commercially available xenon lamp (model number: MAX-301, manufactured by Asahi Spectroscopy Co., Ltd.) and a plurality of color filters were used as the light source 22. In this example, in order to obtain the fourth Purkinje image 124, we focused on a total of eight wavelengths: 430 nm, 460 nm, 470 nm, 480 nm, 500 nm, 520 nm, 540 nm, and 600 nm. Eight commercially available color filters (model numbers: MX0430, MX0600, etc., manufactured by Asahi Spectroscopy Co., Ltd.) were used to correspond to the aforementioned eight wavelengths.

As the optical fiber 24, a commercially available light guide (model number: UD0164, manufactured by Asahi Spectroscopy Co., Ltd.) was used. As shown in FIG. 6, a cover member in which a circular hole with a diameter of 3 mm in front view was formed on the path of the incident light ILk was provided at the output end of the light guide. The cover member was formed from a styrene board colored black. Although high-intensity white light is emitted from the xenon lamp, by providing a cover member at the output end of the light guide, the intensity of the light ILk from the light source 22 can be appropriately suppressed and irradiated to the eye 360. In this embodiment, k=8 as described above.

As the imaging camera 30, a commercially available CMOS camera (model number: BFS-U3-32S4M-C, manufactured by FLIR Systems, Inc.) was used. A commercially available fixed focus lens (model number: TECHSPEC C series 50 mm VIS-NIR, manufactured by Edmund Optics Japan Co., Ltd.) with a focal length of 50 mm and a numerical aperture of 0.018 was provided in the light receiving section of the CMOS camera. A light bulb-colored light emitting diode (LED) (forward voltage VF=3.2V, forward current IF=20 mA, luminous intensity IV=18000 mcd) was used as the gaze object 90 shown in FIG. 4.

Based on the above-mentioned crystalline lens transmission spectrum estimation method, a prototype estimation system 10 was used to test 10 subjects in the young age group (20 to 34 years old) and the middle age group (35 to 49 years old). The transmission spectra of the crystalline lenses of a total of 26 subjects, including 9 middle subjects and 7 older subjects ranging from 50 to 70 years old, were estimated. FIG. 7 is an example of a first Purkinje image, a third Purkinje image, and a fourth Purkinje image formed by the eyes of a certain subject. In the prototype estimation system 10, as the diameter of the hole formed in the cover member becomes smaller, the first Purkinje image, the third Purkinje image, and the fourth Purkinje image are separated from each other and become easier to identify. The image becomes very small. The diameter of the hole formed in the cover member is not limited to 3 mm, but if it is 3 mm as an example, the first Purkinje image, the third Purkinje image, and the fourth Purkinje image can be identified, respectively, as shown in FIG. It can be seen that the fourth Purkinje image can be sensed by separating them from each other as shown in FIG.

The fourth Purkinje image Meas[124-k] formed by the eyes 360 of each of the 26 subjects was photographed, and the measured luminance AL(λk) and The actual size AW (λk) was measured. Further, reference brightness FL (λk) and reference size FW (λk) were measured using a commercially available simulated eye whose optical density is constant regardless of the wavelength in the visible wavelength band.

Next, the measured optical density AD _media (λk) was calculated for each subject based on the above-mentioned equation (1). That is, in this example, for each subject, AD _media (430 nm), AD _media (460 nm), AD _media (470 nm), AD _media (480 nm), AD _media (500 nm), AD _media (520 nm), AD _media (540 nm) ), AD _media (600 nm), eight actually measured optical densities were calculated. FIG. 8 shows the results of calculating AD _media (λk) for each of the eight wavelengths described above for subjects in each age group (Young, Middle, Old) in the form of standard deviation error bars. In addition, in FIG. 8, the error bars of the standard deviation of the measured optical density AD _media (λk) are set in the negative direction for the young age group and in the positive direction for the middle-aged and elderly groups so that the error bars do not overlap between age groups. displayed.

Subsequently, in the optical density estimating section 60, the wavelength λk (k = 1 to 8, that is, eight wavelengths of 430nm, 460nm, 470nm, 480nm, 500nm, 520nm, 540nm, and 600nm) is added to the wavelength λ of equation (2) above. By substituting each of , the known optical density FD _media (λk) of each wavelength λk was obtained. The age of the known optical density FD _{media (λk) at which the difference from the measured optical density AD media} (λk) at each of the above-mentioned eight wavelengths for each _subject was the smallest was calculated and defined as the crystalline lens age AGE.

Subsequently, in the optical density estimating section 60, the lens age AGE obtained for each subject was substituted into the above-mentioned equation (2) to estimate the estimated optical density ED _media (λ) (λ=430 nm to 600 nm). Since the estimated optical density ED _media (λ) is determined by (2), the estimated optical density ED _media (λ) for each subject was obtained as a continuous function dependent on the wavelength λ. FIG. 9 shows the results of calculating the average value of the estimated optical density ED _media (λ) for each age group in order to see the tendency of change in the transmission spectrum of the crystalline lens for each age group.

Next, by substituting the calculated average estimated optical density ED _media (λ) for each age group into the above equation (3), the transmittance T (λ) of the crystalline lens of multiple subjects in each age group (hereinafter referred to as The average transmittance T _AVE (λ) was calculated. Figure 10 shows the average transmittance T _AVE (λ) in the visible wavelength band from 380 nm to 700 nm for each age group, that is, the calculated average transmission spectrum of the crystalline lens in the visible wavelength band for multiple subjects in each age group. shows.

As explained above, in this example, based on the transmission spectrum estimation method of the crystalline lens described above, the fourth Purkinje image of the crystalline lens of each of the 26 subjects in three age groups was obtained. The average transmission spectrum of the crystalline lens was calculated. From the three transmission spectra shown in FIG. 10, it is possible to read the tendency of changes in the transmission spectrum of the crystalline lens depending on the age group.

For example, as shown in FIG. 10, in the entire wavelength band from 400 nm to 700 nm, the average transmittance T _AVE (λ) of the crystalline lens is lower in the middle age group than in the young age group, and The average transmittance T _AVE (λ) of the crystalline lens was lower in the older age group than in the middle age group. This indicates that, as is already known, the optical density of the crystalline lens increases with age. However, in this example, as shown in _{FIG .} λ) could be quantitatively obtained as a transmission spectrum over the visible wavelength band of 380 nm or more and 700 nm or less. This shows that the difference in the average transmittance T _AVE (λ) of the crystalline lens between the young and middle-aged groups is not constant in the visible wavelength band from 380 nm to 700 nm. It was found that the difference in the average transmittance T _AVE (λ) of the crystalline lens and the layer is not constant in the visible wavelength band of 380 nm or more and 700 nm or less. Furthermore, at the same wavelength λ, the average transmittance T _AVE (λ) of the crystalline lens between the middle-aged group and the older age group is greater than the difference in the average transmittance T _AVE (λ) of the crystalline lens between the young age group and the middle-aged group. There is a large difference in the average transmittance T _AVE (λ) of the crystalline lens between the young and middle-aged groups, and a difference in the average transmittance T _AVE (λ) of the crystalline lens between the middle-aged and elderly groups. It was found that the difference is not constant in the visible wavelength band from 380 nm to 700 nm. In particular, in the visible wavelength band from 450 nm to 500 nm, the difference in average transmittance T _AVE (λ) of the crystalline lens between middle-aged and elderly groups was larger than in other visible wavelength bands. From this, it was found that the optical density of the crystalline lens of older people tends to be higher for visible blue light than for red and green visible light.

As mentioned above, from the results of this example, according to the above-mentioned method for estimating the transmission spectrum of the crystalline lens, the optical density of the crystalline lens at a predetermined wavelength is simply calculated after taking the fourth Purkinje image at a plurality of predetermined wavelengths. We have confirmed that it is possible to not only obtain, but also calculate the transmission spectrum of the crystalline lens in the visible wavelength band including a predetermined wavelength. By obtaining the transmission spectrum in the visible wavelength band, we can understand the visual and non-visual functions of the subject, which are reflected in changes in the transmission spectrum of the crystalline lens in each age group, and determine the appropriate diagnosis, living environment, and usage for the subject. We can make suggestions for auxiliary equipment, etc.

In this example, in order to examine trends in changes in lens transmission spectra for each age group, the average estimated optical density ED _media (λ) at each of eight wavelengths for multiple subjects in each age group was calculated. The value was calculated. However, for example, if you want to know the change in the lens transmission spectrum for each subject within the same age group, use equation (3) based on the estimated optical density ED _media (λ) estimated at each of the eight wavelengths for each subject. The transmittance T(λ) for each subject may be calculated from . By doing so, it is possible to calculate the transmission spectrum of the crystalline lens of each subject, and it is possible to investigate changes in the transmission spectrum of the crystalline lens of each subject with age and the relationship between the factors of the change and lifestyle habits.

10 Estimation system (crystalline lens transmission spectrum estimation system)
20 Image data measurement unit 50 Optical density calculation unit 60 Optical density estimation unit 70 Spectrum calculation unit

Claims (7)

Image data in which the brightness of images of a plurality of mutually different wavelengths formed by the crystalline lens is measured as an actual luminance for each of the plurality of mutually different wavelengths, and the size of the image is measured as an actual size for each of the plurality of mutually different wavelengths. Actual measurement section,
a ratio between the measured brightness of each of the plurality of mutually different wavelengths and a reference brightness obtained in advance for each of the plurality of mutually different wavelengths, the measured size of each of the plurality of mutually different wavelengths, and the ratio of the plurality of mutually different wavelengths; an optical density calculation unit that calculates the measured optical density of the crystalline lens at each of the plurality of mutually different wavelengths based on a ratio with a reference size obtained in advance for each of the different wavelengths;
an optical density that satisfies a predetermined condition for the measured optical density at each of the plurality of mutually different wavelengths and estimates a known optical density obtained in advance for a predetermined wavelength range that includes the plurality of mutually different wavelengths as an estimated optical density; Estimating section;
a spectrum calculation unit that calculates the transmittance of the crystalline lens in the predetermined wavelength range as a transmission spectrum of the crystalline lens based on the estimated optical density in the predetermined wavelength range;
A system for estimating the transmission spectrum of crystalline lenses. The known optical density obtained in advance for the predetermined wavelength range is calculated based on the crystalline lens age of the crystalline lens for each wavelength within the predetermined wavelength range and a predetermined coefficient according to the crystalline lens age.
The transmission spectrum estimation system for a crystalline lens according to claim 1. The image is an image formed by reflection on a surface of the crystalline lens adjacent to the vitreous body.
The transmission spectrum estimation system for a crystalline lens according to claim 1 or 2. The plurality of mutually different wavelengths include 600 nm and at least one wavelength within a wavelength band of 400 nm or more and less than 600 nm,
The transmission spectrum estimation system for a crystalline lens according to any one of claims 1 to 3. further comprising a light source that irradiates the crystalline lens with the plurality of lights of different wavelengths;
The transmission spectrum estimation system for a crystalline lens according to any one of claims 1 to 4. a gaze object is placed within the visual field of the eye having the crystalline lens;
The transmission spectrum estimation system for a crystalline lens according to any one of claims 1 to 5. measuring the brightness of images of a plurality of mutually different wavelengths formed by the crystalline lens as measured brightness for each of the plurality of mutually different wavelengths, and measuring the size of the image as a measured size for each of the plurality of mutually different wavelengths;
a ratio between the measured brightness of each of the plurality of mutually different wavelengths and a reference brightness obtained in advance for each of the plurality of mutually different wavelengths, the measured size of each of the plurality of mutually different wavelengths, and the ratio of the plurality of mutually different wavelengths; Calculating the measured optical density of the crystalline lens at each of the plurality of mutually different wavelengths based on the ratio with a reference size obtained in advance for each of the different wavelengths,
Measured optical densities at each of the plurality of mutually different wavelengths and predetermined pre-obtained optical densities including the plurality of mutually different wavelengths among the known optical densities obtained in advance for a predetermined wavelength range including the plurality of mutually different wavelengths. Estimating the known optical density with the smallest difference from the known optical density as the estimated optical density,
calculating the transmittance of the crystalline lens in the predetermined wavelength range as a transmission spectrum of the crystalline lens based on the estimated optical density in the predetermined wavelength range;
A method for estimating the transmission spectrum of a crystalline lens.

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