Patent Application
20220400944
The present disclosure relates to a method for testing visual characteristics, a method for determining characteristics of optical filter, an optical filter, an optical element set for testing visual characteristics and a test image for testing visual characteristics.
As impairments of a human visual sense, there has been known color blindness or color weakness, in which sensitivity to light in a specific wavelength band is low, and photosensitivity, in which people feel dazzled by light in a specific wavelength band. The photosensitivity is, for example, Irlen syndrome. These visual impairments are caused by higher or lower sensitivities of three cone cells (S, M, and L cone cells) or rod cells on a patient's retina compared to normal subjects. These S, M. and L cone cells are cells that respond to blue light, green light, and red light, respectively. The rod cells are cells that respond to the light intensity. The light sensitivity of a human depends on brightness of the environment, and the sensitivity in a bright environment is called photopic vision and the sensitivity in a dark environment is called scotopic vision. The photopic vision is mainly achieved by the cone cells, while the scotopic vision is mainly achieved by the rod cells (see
In order to make an optical filter adjusted to the patient, it is necessary to test the patient's visual characteristics (sensitivities) to various colors of light. However, since there are countless combinations of sensitivities to various lights, the test of visual characteristics is burdensome for both a testing person and the patient.
There have heretofore been known, a method for making eyeglasses that classify a patient's color vision characteristics. In this method, color vision characteristics are classified into 32 types based on test results of multiple patients' color vision characteristics, in this method, it is examined which of the 32 types of color vision characteristics the patient's color vision characteristics correspond to. By determining the characteristics of the optical filter based on the test results, the patient's color vision abnormality is suppressed.
In the color vision testing method described in Patent Document 1, it is determined which of the predetermined types of color vision characteristics the patient's color vision characteristics correspond to. Therefore, there is a problem that accurate test results are unable to be obtained for patients with color vision characteristics that do not correspond to any of the predetermined types, or for patients having intermediate color vision characteristics between a plurality of types. In the test of visual characteristics described in Patent Document 1, the color vision characteristics are classified according to the wavelength band to which the cone cells are sensitive, but the sensitivity of the rod cells is not taken into consideration. Therefore, the test of visual characteristics described in Patent Document 1 is unable to examine abnormalities in visual characteristics caused by influences of the rod cells. In addition, the method does not take into account the photopic, scotopic, and mesopic visions, which are affected by the combined sensitivity of the cone cells and the rod cells.
The present disclosure was made in view of the above circumstances, and the purpose of the present disclosure is to provide a method for testing visual characteristics, a method for determining the characteristics of an optical filter, an optical filter, an optical element set for testing visual characteristics, and a test image for testing visual characteristics, with less load on the subject of the test.
According to aspects of the present disclosure, there is provided a method for testing visual characteristics, comprising a first determining step of determining whether a first test condition is satisfied when a subject is looking at a test image through an optical element for testing, and at least one of a changing step of changing the optical element for testing to be placed between the subject and the test image from one element to another among a plurality of optical elements included in an optical element set prepared for the optical element for testing, and a providing step of providing the subject with a particular image as the test image. The particular image includes a first image area containing a color to which rod cells of a human are sensitive, the first image area being placed on the particular image in such a manner that light coming from the first image area forms an image on a region outside a central fovea of a retina of the subject when the subject is looking at a center of the particular image. The optical element set includes a plurality of first optical elements configured to transmit light of a first wavelength band to which the rod cells are sensitive within a visible light band, the plurality of first optical elements having respective different transmittances in the first wavelength band. The plurality of first optical elements have a common upper limit of the first wavelength band, the upper limit of the first wavelength band being set between a wavelength at which an absorption spectrum of S cone cells of the human and an absorption spectrum of the rod cells intersect each other, and a wavelength at which the absorption spectrum of the rod cells and an absorption spectrum of M cone cells of the human intersect each other. When the method for testing visual characteristics comprises the changing step, the first determining step specifies, from among the plurality of first optical elements, a first optical element that satisfies the first test condition when the subject is looking at the test image through the first optical element placed between the subject and the test image.
According to aspects of the present disclosure, there is provided a method for determining characteristics of optical filter including a determining step of determining transmittance, in the first wavelength band, of an optical filter used for adjusting light intensity based on transmittance, in the first wavelength band, of the first optical element, the first optical element being determined to be satisfied the first test condition.
According to aspects of the present disclosure, there is provided an optical filter that transmittance in the first wavelength band of the optical filter being set to transmittance, in the first wavelength band, determined by the method for testing visual characteristics.
According to aspects of the present disclosure, there is provided an optical element set for testing visual characteristics including a plurality of optical elements. The optical element set includes a plurality of first optical elements configured to transmit light of a first wavelength band to which rod cells of a human are sensitive within a visible light band, the plurality of first optical elements having respective different transmittances in the first wavelength band. The plurality of first optical elements have a common upper limit of the first wavelength band, the upper limit of the first wavelength band being set between a wavelength XS-Rod at which an absorption spectrum of S cone cells of the human and an absorption spectrum of the rod cells intersect each other, and a wavelength XRod-M at which an absorption spectrum of the rod cells and an absorption spectrum of M cone cells of the human intersect each other.
According to aspects of the present disclosure, there is provided a test image for testing visual characteristics, including a first image area including a color to which rod cells of a human are sensitive, the first image area being placed in such a manner that light emitted from the first image area forms an image on a region outside a central fovea of a retina of a subject when the subject is looking at a center of the test image.
Hereinafter, an illustrative embodiment according to aspects of the present disclosure will be described referring to the accompanying drawings.
[Testing System of Visual Characteristics]
The display 100 is, for example, a liquid crystal display or a CRT (Cathode Ray Tube) display. The display 100 displays a test image 110. The display 100 is used to show the test image 110 to the subject 500. The display 100 is not limited to the liquid crystal display that displays an image based on image signals. For example, the display 100 is equipped with a film on which the test image 110 is printed and a backlight that illuminates the film. The test image 110 may be presented to the subject 500 by illuminating the film with illumination light.
The display 100 is covered with the light shielding hood 200. The light shielding hood 200 is configured to prevent the test image 110 from being illuminated by external light and changing the brightness and color of the test image 110 as seen by the subject 50. The inside of the light shielding hood 200 should be black, which absorbs light, in order to prevent light from reflecting and affecting the test of visual characteristics.
The color filter 300 is worn over eyes of the subject 500 like glasses during the test of visual characteristics. The color filter 300 may be placed between the eyes of the subject 500 and the test image 110, and its form is not limited. For example, the color filter 300 may be positioned on the front surface of the display 100 to cover the test image 110, or it may be placed between the subject 500 and the display 100 and within the light shielding hood 200. A plurality of color filters 300 having different characteristics may be used. The plurality of color filters 300 are examples of a set of optical elements for the test of visual characteristics.
In the test of visual characteristics, the subject 500 views the test image 110 through the color filter 300. The subject 500 then changes the color filter 300 to test how much glare the subject 500 perceives on the test image 110 (i.e., degree of photosensitivity) and how the subject perceives the color of the test image 110 (i.e., color vision). Since the color filter 300 is used to test the subject 500, it should have the characteristic of transmitting light in the visible light band. The color filter 300 may have any transmittance in bands other than the visible light band.
When the visual characteristics of the subject 500 are tested by the test of visual characteristics, a correction filter that corrects the visual characteristics of the subject 500 can be produced based on the test results. The test results are used not only to produce the correction filter, but also to adjust the brightness and color of the lighting equipment or monitors such as TVs and mobile terminals used by the subject 500 to match the visual characteristics of the subject 50.
[Color Filter]
Color filter 300 is a bandpass filter that transmits only light in a specific wavelength band. The bandwidth of the bandpass filter is determined based on the characteristics of human cone and rod cells.
The S, M, and L cone cells are sensitive to light in the blue, green, and red wavelength bands, respectively. However, when a human recognizes colors, the intensity of the light absorbed by the S, M. and L cone cells does not necessarily correspond to B, G, and R components in an RGC color space. In the following, a two-color experiment by Edwin Herbert Land on human color vision will be described. In the two-color experiment, a slide (a positive film) R of an image of a subject photographed through a red filter and a slide (a positive film) G of an image of a subject photographed through a green filter are used. The images on the slides R and G are, respectively, monochrome images represented in a grayscale according to the light intensity distributions of photographed subject images.
The slide R is illuminated with red light and projected onto a screen. The slide G is illuminated with white light and projected onto the screen. As a result, a composite projected image is displayed on the screen, in which a projected image with only a red wavelength component and a projected image with a white wavelength component are superimposed on each other. The light intensity of the two projection images projected on the screen is adjusted according to a subject who watches the composite projection image. The subject then perceives the composite projection image as a full-color image including blue and green colors. In other words, in this two-color experiment, the subject perceives blue and green colors in the projected image superimposed by the red and white lights.
In the two-color experiment, when the slide R is illuminated with a white light and the slide G is illuminated with a green light, and a projected image with a white wavelength component and a projected image with a green wavelength component are superimposed on the screen to create a composite projection image, the subject perceives blue and red colors for the composite projection image superimposed by the white and green lights.
Thus, the visual characteristics of the human is not merely linear addition of the three primary colors (red, green, and blue) of lights, but is significantly related to the cognitive functions of the brain. In the two-color experiment, the human perceives full-color for projected images superimposed by the red and white lights or by the white and green lights. Therefore, the M cone cells and L cone cells, which are sensitive to the green light and the red light, respectively, are thought to be used by the human to recognize full-color.
In addition, since the cone cells are mainly responsible for the photopic vision, it is thought that in bright areas, the human recognizes colors by the M and L cone cells, and recognizes the brightness of light by the remaining S cone cells. On the other hand, since rod cells are mainly responsible for scotopic vision, it is thought that in dark area, humans recognize the brightness of light by these rod cells. Therefore, a human with high sensitivities to the S cone cells and the rod cells, which are used to recognize the brightness of light, experiences the symptoms of photosensitivity, in which the human feels dazzled by the light. In addition, color weakness or color blindness occurs in a human whose the sensitivities of the M cone cells and the L cone cells used for color perception (i.e., sensitivity to the green light and sensitivity to the red light) are different from each other.
The characteristics of the color filter 300 are determined to be suitable for testing the degree of photosensitivity and the difference in sensitivity to green light and red light. The color filter 300 includes filter 300Rod suitable for testing the degree of photosensitivity, and filters 300M and 300L suitable for testing sensitivity difference between the sensitivity to the green light and the sensitivity to the red light.
The filter 300Rod is used to test the degree of photosensitivity of the subject 500, and has a characteristic of transmitting light in the wavelength band to which the S cone cells and the rod cells are sensitive.
The filter 300Rod has the characteristics of transmitting light in the wavelength band to which the S cone and the rod cells are sensitive, as shown by the solid line in
In order to transmit more light in the wavelength band that the S cone cells are sensitive, the filter 300Rod may transmit light at a wavelength below the peak wavelength PS of sensitivity of the S cone cells. However, light with the wavelength below the peak wavelength PS of the S cone cells has little effect on the color perceived by a human, although it makes the human feel the brightness of light. Therefore, if the subject 500 has symptoms of photosensitivity, the filter 300Rod that does not transmit light with a wavelength below the peak wavelength PS of the sensitivity of the S cone cells is able to effectively suppress the symptoms of photosensitivity of the subject 500 without significantly affecting the color vision of the subject 500.
In addition, the filter 300Rod is used to test the light sensitivities of the S cone and the rod cells of the subject 500, and the upper limit of the bandwidth BRod is not limited to the peak wavelength PRod (about 498 nm) of the rod cells.
For example, the upper limit of the bandwidth BRO of the filter 300Rod may be the wavelength XRod-M (about 515 nm) at which the absorption spectrum of the rod cells and the absorption spectrum of the M cone cell intersect each other. This wavelength XRod-M is longer than the peak wavelength PRod and shorter than the peak wavelength PM. In a band with a wavelength longer than XRod-M, the sensitivity of the rod cells is relatively low and the sensitivity of the M cone cells is relatively high. Therefore, if the upper limit of the bandwidth BRod of the filter 300Rod is longer than the wavelength XRod-M, the degree of light absorbed by the M cone cells will be larger, and it may not be possible to accurately test for photosensitivity due to the rod cells.
In addition, the upper limit of the bandwidth BR d of the filter 300Rod may be shorter than the peak wavelength PRod (about 498 nm) of sensitivity of the rod cells. For example, the upper limit of the bandwidth BRod of the filter 300Rod may be the wavelength XS-Rod (about 453 nm) at which the absorption spectrum of the S cells and the absorption spectrum of the rod cells intersect each other. This wavelength XS-Rod is longer than the peak wavelength PS and shorter than the peak wavelength PRod. In the band with a wavelength shorter than the XS-Rod wavelength, the sensitivity of the rod cells is relatively low and the sensitivity of the S cone cells is relatively high. Therefore, if the upper limit of the bandwidth BRod of the filter 300Rod is shorter than the wavelength XS-Rod, the degree of light absorbed by the S cone cells will be larger, and it may not be possible to accurately test for photosensitivity due to rod cells.
In addition, in order to accurately test photosensitivity caused by rod cells, the bandwidth BRod of the filter 300Rod should include a wavelength band close to the peak sensitivity wavelength PRod of rod cells. Therefore, the upper limit of the bandwidth BRod of filter 300Rod should be shorter than the peak sensitivity wavelength PRod of the rod cell, but it should not be too far from the peak wavelength PRod. For example, when the difference between the peak sensitivity wavelength PRod of the rod cells and the wavelength XRod-M at which the absorption spectrum of the rod cells and the absorption spectrum of the M cone cells are intersect each other is Δ, by setting the upper limit of the bandwidth BRod of filter 300Rod within the range of PRod±Δ, it is possible to accurately test for photosensitivity caused by rod cells.
The filter 300M is a filter for testing the sensitivity to green light of the subject 500 and has a characteristic of transmitting light in the wavelength band to which M cone cells are sensitive.
The filter 300M, as shown by the solid line in
The characteristics of the filter 300M are used to make a correction filter that corrects the visual characteristics of the subject 500. If the subject 500 wishes to emphasize the brightness of the correction filter, the upper limit of the bandwidth BM of filter 300M may be set to the wavelength PPho (about 570 nm), which is the wavelength of maximum sensitivity for the photopic vision shown in
In order to increase the degree of light in the wavelength band to which the M cone cells are sensitive among the light transmitted through the filter 300M, the lower limit of the bandwidth BM of the filter 300M may be set to the wavelength XRod-M (about 515 nm), which is the wavelength at which the absorption spectrum of the rod cells and that of M cone cells intersect each other. The bandwidth BM of the filter 300M in this case is shown in
The rod cells are cells that respond to intensity of light and do not affect the color perception (color vision) of the subject. Therefore, even if the lower limit of the bandwidth BM of the filter 300M is set to the peak sensitivity wavelength PRod of the rod cells, the sensitivity of the M cone cells to green light can be tested. In addition, when the lower limit of the bandwidth BM is set to the peak sensitivity wavelength PRod of the rod cells, compared to when the lower limit is set to the wavelength XRod-M, the test image 110 that the subject 50 watches becomes brighter. This makes it easier for the subject 500 to watches the test image 110.
The filter 300L is a filter for testing the sensitivity of the subject 500 to red light. The filter 300L has the characteristic of transmitting light in the wavelength band to which the L cone cells are sensitive.
The filter 300L transmits only light at wavelengths above the wavelength XM-L (about 548 nm), where the absorption spectrum of the M cone cells intersects that of L cone cells, as shown by the solid line in
In the wavelength band shorter than the wavelength XM-L, the sensitivity of the L cone cells becomes lower and the sensitivity of the M cone cells becomes dominant. Therefore, if the lower limit of the bandwidth BL of the filter 300L is set shorter than the wavelength XM-L, the sensitivity to red light by the L cone cells may not be accurately tested.
If the subject 500 wants to emphasize the brightness of the correction filter made based on the characteristics of the filter 300L, the lower limit of the bandwidth BL of filter 300L may be the wavelength PPho (about 570 nm), which is the wavelength of maximum sensitivity of the photopic vision shown in
It should be noted that the filters 300Rod, 300M, and 300L need not be perfectly rectangular as shown in
In addition, the color filter 300 includes a plurality of filters with different transmittance for each of the three filters 300Rod, 300M, and 300L, which have different bandwidths. In detail, the color filter 300 has 10 different filters with transmittance in the band varying from 10% to 100% in 10% increments for each of the filters 300Rod, 300M, and 300L, respectively. In other words, the color filter 300 contains a total of 30 different filters with different bandwidths or transmittances. The transmittance within the bandwidth of the color filter 300 need not differ in 10% increments. By decreasing the increments of transmittance and increasing the number of the color filters 300, the sensitivity of each cone and rod cell of the subject 500 can be tested more accurately, but the time and load required for the test will increase. On the other hand, by increasing the increments of transmittance and decreasing the number of color filters 300, the time and load required for the test can be reduced, but the accuracy of the test results for the sensitivity of each the cone and rod cell of the subject 500 will be smaller.
In addition, the characteristics of the filters 300Rod, 300M and 300L shown in
[Test Image]
Next, the test image 110 displayed on the display 100 will be explained.
The test image 110 includes a circular inner area 120 located near the center of the test image 110 and an outer area 130 around it. The inner area 120 and the outer area 130 of the test image 110 have colors different from each other. In the example shown in
The inner area 120 is a region corresponding to a central fovea on a human retina. The size of the inner area 120 is set so that light coming from the inner area 120 forms an image within the central fovea. The size of the inner area 120 is set such that the apex angle θIN of a cone with the inner area 120 as a base and eyes of the subject 500 as a vertex is about 2 degrees. This apex angle θIN of about 2 degrees corresponds to the size of the field of view by the central fovea (i.e., the viewing angle). The diameter of the inner area 120 depends on the distance between the subject 500 and the display 100 in the testing system of visual characteristics 1. The size of the inner area 120 should be set so that light coming from the inner area 120 forms an image in the central fovea, and the apex angle θIN need not be exactly 2 degrees.
The outer area 130 corresponds to an area surrounding the central fovea on the human retina. The size of the outer area 130 is set in such a manner that light coming from the outer area 130 forms an image on the rod cells located outside the central fovea. The size of the outer area 130 is set in such a manner that an apex angle θOUT (see
In the central fovea on the human retina, the M cone cells, which are sensitive to green light, and the L cone cells, which are sensitive to red light, are located in large numbers. The central fovea also contains few S-cone and rod cells. On the other hand, the S. M, and L cone cells and the rod cells are located in the region outside the central fovea.
A human's eyesight is higher when the central fovea is used. When a human sees objects, images, or letters, the human recognizes a shape and color of the observed object mainly by using the M and L cone cells located in the central fovea. In other words, the human can recognize colors using only the M and L cone cells. In addition, humans recognize not only color but also brightness by using the S and M cone cells and the rod cells around the central fovea. Therefore, it is possible to test a human's color vision by a visual test targeting the M cone cells and the L cone cells in the central fovea. In addition, the degree of photosensitivity can be tested by examining the S cone cells and rod cells around the central fovea.
The inner area 120 of the test image 110 is the area used for testing color vision of the M and L cone cells and contains chromatic colors. On the other hand, the outer area 130 is preferably achromatic (i.e., magnitudes of the R. G, and B components in the RGB color space are the same). This is because if the outer area 130 is colored, the color of the outer area 130 may affect the color vision test using the inner area 120. The color of the outer area 130 is not limited to achromatic colors, but have to contain colors to which the rod cells are sensitive. For example, the color of the outer area 130 is a color other than black (i.e., all of the magnitudes of the R, G, and B components are zero). The color of the outer area 130 may also be white. The outer area 130 need not be a uniform color throughout, but may include areas of relatively low or high brightness.
The inner area 120 includes at least two divided areas 121 and 122. At least one of magnitudes of the R component and the G component are different between the divided area 121 and the divided area 122. The B components of the divided areas 121 and 122 have arbitrary magnitudes. For example, the magnitude of the B components may be the same or different between divided area 121 and divided area 122. Furthermore, the magnitude of the B component in divided area 121 and divided area 122 may be zero. The inner area may include three or more divided areas of different colors. In addition, multiple types of the test images 110 with different numbers, shapes, and colors of divided areas of the inner areas 120 may be used for visual test.
In addition, if one of the divided areas 121 and 122 has an R component (i.e. the magnitude of the R component is not zero), the R component of the other of the divided areas 121 and 122 may be zero. Also, if one of the divided areas 121 and 122 has a G component (i.e. if the magnitude of the G component is non-zero), the G component of the other may be zero.
The two divided areas 121 and 121 of the inner area 120 are set in such a manner that a normal person who does not have color blindness can clearly recognize the difference between the two colors when looking at the two divided areas 121, 122.
The brightness of the color of the outer area 130 is set in such a manner that a normal person, who does not have photosensitivity, does not feel dazzled by the test image 110.
[Method of Visual Test]
Next, a method of testing visual characteristics using the testing system of visual characteristics 1 will be described.
[Processing Step S101 in
In processing step S101, the degree of photosensitivity of the subject 500 is tested. In other words, the degree to which the S cone and rod cells of the subject 500 are more sensitive than those of a normal person is tested.
An inspector of the visual characteristics displays the test image 110 on the display 100 and presents it to the subject 500.
The subject 500 wears one of the multiple filters 300 and watches the test image 110 displayed on the display 100 in the light shielding hood 200. At this time, the subject 500 is looking at the center of the test image 110, i.e., the inner area 120. Thus, light coming from the outer area 130 to form an image on the retina in the region outside the central fovea, where a lot of the rod cells are located.
The subject 500 switches between 10 different filters 300Rod with different transmittance in the bandwidth BRod while observing the test image 110. Then, the subject 500 selects the filter 300Rod that did not cause glare to the test image 110. If there is more than one filter 300Rod that the subject 500 did not feel dazzled by the test image 110, the subject 500 selects the filter 300Rod with the highest transmittance. The condition in which the subject 500 does not feel dazzled by the test image 110 is an example of the first test condition of this application.
The brightness of the test image 110 is set such that a person who does not have photosensitivity does not feel dazzled. Therefore, if the degree of photosensitivity of the subject 500 is small, or if the subject 500 does not have photosensitivity, the subject 500 will select the filter 300Rod, which has a relatively high transmittance. On the other hand, if the degree of photosensitivity of subject 500 is high, the subject 500 will select the filter 300Rod with a relatively low transmittance.
The glare that the subject 500 feels dazzled is subjective to the subject 500. Therefore, the transmittance of the filter 300Rod is not necessarily determined only by the magnitude of sensitivity of the S cone cells and rod cells, but also includes the influence of the subject's preference for vision.
[Processing Step S102 in
In processing step S102, it is tested whether the subject 500 has low sensitivity to either green light or red light. In other words, the difference between the sensitivity of the M cone cells and the L cone cells of the subject 500 is tested.
This test is performed, for example, using the well-known Ishihara color test chart. The Ishihara color test chart is a chart commonly used in testing for color deficiency. The Ishihara color test chart is colored in such a way that letters (e.g., numbers) can be recognized when a color vision of a subject is normal or when color deficiency of the subject is properly corrected. Since the Ishihara color test chart is well known to those skilled in the art, explanation thereof is omitted herein.
[Processing Step S103 in
In processing step S103, the color vision of the subject 500 is tested. In detail, the sensitivity of one of the M and L cone cells that is determined to be sensitive in step S102 is tested compared to the sensitivity of the other.
The subject 500 wears either one of the filters 300M and 300L and observes the test image 110 displayed on the display 100 in the light shielding hood 200. When it is determined in step S102 that the M cone cells of the subject 500 have higher sensitivity than the L cone cells, the subject 500 wears the filter 300M. When it is determined in step S102 that the L cone cells of the subject 500 have higher sensitivity than the M cone cells, the subject 500 wears the filter 300L.
The subject 500, with either one of the filters 300M and 300L wore, watches the center of the test image 110, that is, the inner area 120. As a result, the light coming from the inner region 120 is imaged in the central fovea on the retina, where a lot of the M and L cone cells are located.
The subject 500 observes the test image 110 while switching 10 types of the filters 300M or the filters 300L having different transmittances of the bandwidth. Then, the subject 500 selects the filter 300M or the filter 300L that allow the subject 500 to clearly recognize the color difference between the multiple divided areas 121 and 122 of the inner area 120. When there are a plurality of the filters 300M or a plurality of the filters 300L that allow the subject 500 to clearly recognize the color difference between the plurality of divided areas 121 and 122, the filter 300M or the filter 300L that the subject 500 can most clearly recognize the color difference among them is selected. A condition in which the subject 500 can clearly recognize the difference in color between the divided areas 121 and 122 is an example of the second test condition of the present application.
For example, when the sensitivities of the M cone cells of the subject 500 are higher than the sensitivities of the L cone cells, the subject 500 wears the filter 300M in step S103. Then, the subject 500 selects the filter 300M that allow the subject 500 to most clearly recognize the difference in color between the divided areas 121 and 122. If the difference between the sensitivities of the M cone cells and the sensitivities of the L cone cells are small, the subject 500 selects the filter 300M having a relatively high transmittance of the bandwidth BM. Further, as the sensitivities of the M cone cells are larger than the sensitivities of the L cone cells, the subject 500 selects the filter 300M having a low transmittance of the bandwidth BM.
The difference in color between the divided areas 121 and 122 recognized by the subject 500 is due to the subjectivity of the subject 500. Therefore, the filter 300M or the filter 300L selected by the subject 500 is not necessarily determined only by the difference in sensitivity between the M cone cells and the L cone cells, and includes the influence of the subject 500's preference on the color vision.
In addition, the subject 500 may have lower (or higher) sensitivity than that of a healthy subject for both the M cone cells and the L cone cells. Therefore, in step S103, both the test with the subject 500 wearing the filter 300M and the test with the subject 500 wearing the filter 300L may be performed. Thereby, it is possible to test how much the sensitivities of the M cone cells and the L cone cells of the subject 500 differs from the sensitivities of the M cone cells and the L cone cells of a healthy person.
Further, if it is known in advance that the subject 500 does not have photosensitivity, the step S101 may be omitted. Further, when only the degree of photosensitivity of the subject 500 is tested, only the step S101 may be executed.
[Correction Filter]
Once the visual characteristics of the subject 500 are tested by the method of testing visual characteristics, the test results are used to make a correction filter that corrects the visual characteristics of the subject 500. The correction filter may be any one that changes the transmission spectrum, and there is no particular limitation on the material or the principle of changing the transmission spectrum. The correction filter is an example of the optical filter of this application.
The characteristics of the correction filter are determined based on the characteristics of the filter 300Rod selected in step S101 and at least one of the characteristics of the filter 300M and the filter 300L selected in step S103.
The transmittance of the correction filter in the bandwidth BRod which is the same as the bandwidth of the filter 300Rod is set to substantially the same transmittance as that of the selected filter 300Rod.
The transmittance of the correction filter in the bandwidth BM which is the same as the bandwidth of the filter 300M is set to substantially the same transmittance as the selected filter 300M when the filter 300M is selected in step S103. On the other hand, when the filter 300M is not selected in step S103 (for example, when only the filter 300L is selected), the transmittance of the bandwidth BM of the correction filter is set to approximately 100%.
The transmittance of the correction filter in the bandwidth BL which is the same as the bandwidth of the filter 300L is set to substantially the same transmittance as the selected filter 300L when the filter 300L is selected in step S103. On the other hand, when the filter 300L is not selected in step S103 (for example, when only the filter 300M is selected), the transmittance of the bandwidth BL of the correction filter is set to approximately 100%.
As shown in
In the example shown in
In this way, the correction filter is produced based on the test result of the visual characteristics, and the subject 500 can correct the visual characteristics by wearing the correction filter. Specifically, this correction filter can suppress photosensitivity caused by the S cone cells and rod cells of the subject 500. In addition, this correction filter can reduce color vision deficiency caused by the sensitivity difference or sensitivity ratio between the M and L cone cells of the subject 500.
Further, in the present embodiment, the subject 500 observes the test image 110 while switching the plurality of filters 300Rods having different transmittances (up to 10 types of filters 300Rods in this embodiment), thereby the degree of photosensitivity can be tested. Further, in the present embodiment, since the filter 300Rod transmits light that the S cone cells and the rod cells are sensitive, the degree of photosensitivity caused by the rod cells can be tested.
Further, the subject 500 can test the color vision of the subject 500 by observing the test image 110 while switching the plurality of filters 300M having different transmittances or the plurality of filters 300L having different transmittances (up to 10 types of filters 300M or up to 10 types of filters 300L in this embodiment). Further, in the present embodiment, since the filter 300M transmits the light that the M cone cells are sensitive and the filter 300L transmits the light that the L cone cells are sensitive, color vision abnormalities due to sensitivity difference or ratio between the M cone cells and the L cone cell can be tested.
Furthermore, in the present embodiment, as the color filter 300, 10 types of filters having different transmittances from each other are prepared for each of the filter 300Rod, the filter 300M, and the filter 300L. However, in the present embodiment, it is not necessary to test all combinations of these color filters 300 for testing the visual characteristics of the subject 500. In the present embodiment, the visual characteristics of the subject 500 are tested by a unique measurement method of visual characteristics in consideration of the characteristics of each cone cells and rod cells, and 20 types of color filters 300 are used for the test (That is, 10 types of the filters 300Rod, and 10 types of the filters 300M or 300L). Therefore, it is possible to suppress the burden on the subject 500 and the inspector by the test of visual characteristics.
In the present embodiment, as the test image 110, a plurality of divided areas 121 and 122 having different colors are provided in the inner region 120 corresponding to the central fovea, and the outer area 130 around the divided areas 120 is achromatic. As a result, with using only one test image 110, the color vision characteristics of the subject 500 (that is, the characteristics corresponding to the difference or ratio of the sensitivities of the M and L cone cells) and the degree of photosensitivity (that is, characteristics corresponding to the sensitivity of the S cone cells and rod cells). Therefore, it is possible to suppress the burden on the subject and the inspector caused by the test of visual characteristics, and to test the accurate visual characteristics in consideration of the characteristics of each cone cells and rod cells.
The above is a description of an exemplary embodiment of the present disclosure. The embodiments of the present disclosure are not limited to those described above, and various variations are possible within the scope of the technical concept of the present disclosure. For example, the embodiments explicitly indicated by way of example in the specification or combinations of obvious embodiments as appropriate are also included in the embodiments of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-028739 | Feb 2020 | JP | national |
This is a Continuation-in-Part of International Application No. PCT/JP2021/006094 filed on Feb. 18, 2021, which claims priority from Japanese Patent Application No. 2020-28739 filed on Feb. 21, 2020. The entire disclosures of the prior applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2021/006094 | Feb 2021 | US |
| Child | 17892988 | US |
