JP5079347B2 - Target presentation device - Google Patents

Description

  The present invention relates to an optotype presenting apparatus that presents an optotype to an eye to be examined.

As a target presentation device used for visual acuity inspection and refractive correction inspection, the target drawn on the target disc plate is illuminated from behind, and the target is projected onto a screen arranged at a distance inspection distance such as 5 m. A projection type projector (see Patent Document 1), having a target disc plate in the housing, and using a concave mirror to emit a target light beam optically at a predetermined distance inspection distance from the observation window, thereby inspecting A space-saving type that presents a visual target to an eye to be examined (see Patent Document 2) is known. In this type of apparatus, conventionally, a halogen lamp that emits steady light has been used as an illumination light source for a target.
JP 2003-310552 A Japanese Patent Laid-Open No. 2005-87760

  In recent years, due to technological advances in LEDs, LEDs that emit white light have been put into practical use, and white LEDs have been used in various lighting devices. In the above-described visual target presenting apparatus, it is conceivable to use a white LED instead of the halogen lamp. However, when a white LED was used in place of the halogen lamp, the following problems were found.

  In the refraction correction inspection, in order to check the suitability of refraction correction, as shown in FIG. 2 (a), a black color composed of letters and symbols in a red background 11 and a green background 13 in which the presentation screen is divided in half. There is a red-green test that presents a red-green test target 10 with a target 12. In this red-green inspection, in addition to the target disc plate on which the black target 12 is formed, a red filter and a green filter divided in half are arranged in the target display optical path, and these are illuminated from behind by an illumination light source. By doing so, a red-green test target is presented. In order to present this red-green test target, when a red filter and a green filter that have been used with a halogen lamp are illuminated with a white LED as they are, the red background 11 is darker than the green background 13. I found a problem. If the green background 13 and the red background 11 are not presented with substantially the same brightness, the reliability of the red-green test is lowered.

  In view of the above-described problems of the prior art, the present invention has the same brightness as possible for the red background and the green background of the red-green test target without increasing the cost even when the white LED is used as the illumination light source for presenting the target. An object of the present invention is to provide an optotype presenting apparatus that can be presented and can ensure the reliability of the red-green test.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) An inspection target on which various inspection targets including a predetermined target for red-green inspection are formed is switched to the optical path, and a red filter and a green filter for dividing the presentation screen are switched to the presentation optical path. In the optotype presenting apparatus that illuminates the red filter and the green filter with an illumination light source from behind, and presents a red-green inspection target having a target in the red background and the green background,
As the illumination light source, a white LED having a light emission characteristic in which a light emission component in the green wavelength region is strong with respect to a light emission component in the red wavelength region is provided, and each filter when the white LED is used as the red filter and the green filter is provided. Using red and green filters with different changes in visual characteristics with respect to thickness changes, the thickness of both filters is adjusted to be the same in order to suppress the occurrence of shadows at the joint of both filters, and the white LED The present invention is characterized in that a filter manufactured by determining the thicknesses of both filters so that the visual characteristics of red and green are substantially the same when the red-green test target is presented by illumination is provided.
(2) In the optotype presenting apparatus according to (1) , red and green visual sensations when the red-green inspection optotype is presented by illumination of the white LED at the same thickness as the red filter and the green filter . It is characterized in that a red filter and a green filter having transmittance changes with substantially the same characteristics are determined from commercially available ones, and both filters are polished at the same time after being bonded, and a filter manufactured with the same thickness is provided. To do.

  According to the present invention, it is possible to present the red background and the green background of the red-green inspection target with the same brightness as much as possible without increasing the cost by using the white LED as the light source. This enables highly reliable red / green inspection.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an optical system of a projection-type target presenting apparatus used in the present embodiment.

  Reference numeral 1 denotes an illumination light source, on which a white LED is arranged. 2 is a condenser lens, and 3 is a projection lens. A chart disk plate 4 and a mask plate 5 are disposed between the condenser lens 2 and the projection lens 3. The chart disk plate 4 is a disk-shaped plate made of a transparent material such as glass, and a large number of inspection targets are formed on the same circumference of the chart disk plate 4 by chromium vapor deposition. The inspection target is illuminated from behind by the illumination light source 1 through the condenser lens 2. The chart disk plate 4 is rotated by a motor 6 to switch the type of inspection target. The mask plate 5 is used to apply a mask such as a column mask, a row mask, or a single character mask to the visual acuity inspection. The mask plate 5 is rotated by a motor 7 to switch the type of mask applied to the inspection target to be projected. The projection screen 8 is placed at a position away from the optotype presenting apparatus by a predetermined distance such as 5 m.

  In the inspection target, a red-green inspection target 10 is prepared as shown in FIG. 2A in order to inspect whether or not the refractive correction is overcorrected. The red-green test target 10 has a black target 12 composed of letters and symbols on each of a red background 11 on the left half and a green background 13 on the right half. The red / green test target 10 is formed on the projection screen 8 by the black target 12 formed on the chart disk plate 4 and the red filter 31 and the green filter 33 (see FIG. 2B) provided on the mask plate 5. Projected. The red filter 31 and the green filter 33 are joined at the joining portion 32 so as to divide the presentation screen in half at the same thickness t = t1. The visual target 12 is switched to the presentation optical path by the rotation of the chart disk plate 4, and the red filter 31 and the green filter 33 are also switched to the presentation optical path by the rotation of the mask plate 5.

  The light beam emitted from the illumination light source 1 is condensed by the condenser lens 2 and illuminates the mask plate 5 and the chart disk plate 4. The target illuminated through the mask plate 5 is projected onto the projection screen 8 by the projection lens 3 and presented to the eye to be examined.

  When correcting myopic eyes, an examination using the red-green examination target 10 will be briefly described. When the visual target 12 on the green background 13 side looks clearer than the visual target 12 on the red background 11 side, it indicates that the eye is focused in the direction of hyperopia from the normal vision state. Overcorrected. On the contrary, when the visual target 12 on the red background 11 side looks clearer than the visual target 12 on the green background 13 side, it indicates that the eye is focused in the near vision direction from the normal vision state. A case where they both look the same is regarded as a normal vision state. At the time of refractive correction, it is determined whether or not the correction power is overcorrected by checking the above-mentioned appearance using the red-green test target 10. In order to accurately perform such inspection with the red-green inspection target 10, the brightness of the red background 11 and the green background 13 needs to be visually recognized substantially the same.

  Next, the visual characteristic that the red background 11 and the green background 13 are substantially the same will be described. First, a difference in light emission characteristics between a conventional halogen lamp used for the illumination light source 1 and a white LED will be described with reference to FIG. In FIG. 3, the normalized emission characteristics with the wavelength λ (nm) on the horizontal axis and the peak value of each light source as 1 are shown on the vertical axis. Graph 36 shows the light emission characteristics of the halogen lamp. Graph 38 shows the light emission characteristics of the white LED. Looking at the light emission characteristic graph 36 of the halogen lamp, the red wavelength region (visible region on the longer wavelength side than the wavelength 600 nm) exhibiting a red color with respect to the light emission component in the green wavelength region (wavelength 520 to 570 nm) exhibiting a green color. Strong luminescent component. On the other hand, when looking at the graph 38 of the light emission characteristics of the white LED, contrary to the halogen lamp, the light emission component in the red wavelength region exhibiting red has a peak near the wavelength of 550 nm, and the green wavelength exhibits green. The luminescent component in the region (wavelength around 520 to 570 nm) is strong. The light emission characteristics of the halogen lamp and the white LED are almost the same as those shown in FIG.

  FIG. 4 is a diagram showing luminous efficiency (specific luminous sensitivity) in photopic vision of the human eye. As shown in the graph 40, in general, the luminous efficiency is stronger in the green wavelength region (near the wavelength of 520 to 570 nm) than in the red wavelength region.

  FIG. 5 is a diagram showing light source spectral luminous characteristics actually perceived by the human eye, which is obtained by multiplying the luminous characteristics of the halogen lamp and white LED of FIG. 3 by the luminous efficiency of the human eye of FIG. It is. A graph 42 shows the spectral luminous characteristics of the halogen lamp, and a graph 44 shows the spectral luminous characteristics of the white LED. The visual characteristics of the red background 11 and the green background 13 when the red-green test target 10 is presented are the spectral visual characteristics of the graph 42 and the graph 44 in FIG. It is obtained by multiplying the transmission characteristics.

  FIG. 6 is a diagram showing the transmission characteristics of the conventional red filter and green filter used in the optotype presenting apparatus in which a halogen lamp is applied as the light source 1. In FIG. 6, the transmission characteristic of the red filter is indicated by a graph 52, and the transmission characteristic of the green filter is indicated by a graph 54. Here, a commercially available Sharp Cut Filter “R62” manufactured by HOYA was used for the red filter, and a Green Filter “G530” also manufactured by HOYA was used for the green filter. Both the red filter and the green filter had a thickness t of 1.3 mm. The transmission characteristics of the green filter at this time are transmitted through wavelengths in the range of 450 to 600 nm as shown in the graph 54 (transmittance is almost 0 in the wavelength range of 450 nm or less and 600 nm or more), It has a peak with a transmittance of about 30% near a wavelength of 530 nm. As shown in the graph 52, the transmission characteristic of the red filter has a transmittance of 80% or more on the long wavelength side of 640 nm or longer, a transmittance of almost 0% on the short wavelength side of the wavelength of 600 nm, and a transmittance of 50%. Is near the wavelength of 620 nm.

  The transmission characteristic of such a red filter and green filter (thickness t is 1.3 mm) multiplied by the light source spectral characteristic (graph 42) of the halogen lamp in FIG. 5 is the visual characteristic shown in FIG. It becomes. In FIG. 7, a graph 56 shows the luminous characteristic by the red filter, and a graph 58 shows the luminous characteristic by the green filter. The red luminous peak was around 630 nm and the green luminous peak was around 540 nm. Referring to FIG. 7, it can be seen that the visual characteristics of red and green have almost the same strength. Note that the luminance ratio of red and green perceived by the human eye is expressed as an area ratio surrounded by graphs 56 and 58, respectively. In FIG. 7, the luminance ratio of green to red is calculated to be 1: 1.3. It is considered that the luminance at which the red background 11 and the green background 13 are substantially the same for the human eye is almost good if the luminance ratio of green to red is in the range of 1: 0.8 to 1: 1.6.

  On the other hand, the light source 1 is replaced with a white LED, and the red and green filters having the transmission characteristics shown in FIG. The visual characteristics shown in FIG. In FIG. 8, a graph 60 shows the luminous characteristics by the red filter, and a graph 62 shows the luminous characteristics by the green filter. FIG. 8 shows that the green luminous characteristic is relatively strong and the red luminous characteristic is significantly weaker than that of the halogen lamp (FIG. 7). The luminance ratio of green to red is about 1: 3.6. This is because, as shown in FIG. 3, the light emission characteristics of the white LED are weak in its red component as compared with the halogen lamp.

  As shown in FIG. 8, if the red background 11 by the red filter and the green background 13 by the green filter are significantly different in brightness, accurate red-green inspection cannot be performed. Therefore, it is necessary to reduce the difference in brightness between the red background 11 and the green background 13 that occurs when the white LED is used, and to the same extent as when a conventional halogen lamp is used. Hereinafter, this method will be described.

  Even if the white LED changes the electric driving method (voltage, current), the light emission characteristics thereof hardly change. Further, since any manufacturer's white LED has almost the same light emission characteristics, measures such as increasing red or decreasing green cannot be taken on the white LED side. Therefore, the luminance difference between the two colors is reduced by changing the transmission characteristics of at least one of the red filter and the green filter. It is technically possible to make the transmission characteristics of the red and green filters desired. However, it is very expensive in terms of cost to design and manufacture the transmission characteristics of each filter in a small amount only for use in the visual target presentation device. On the other hand, by using commercially available red filters and green filters that are generally distributed, the apparatus can be made inexpensive in terms of cost. However, the types of commercially available filters are limited.

  Therefore, the transmittance of the green filter is adjusted so as to make the green component weaker than before by adjusting the thickness of each filter while using a commercially available red filter and green filter.

  Here, it is necessary to consider that the thickness t of the red filter 31 and the green filter 33 shown in FIG. If the thicknesses t of the two filters are different, the joint portion 32 becomes a step, and the boundary portion between the two filters becomes a shadow and is projected onto the projection screen 8. This shadow is bothersome for the subject and tends to hinder the gaze of the target by the subject's eye. Further, the corners of the commercially available red filter 31 and green filter 33 are chamfered by 0.05 to 0.1 mm in order to prevent chipping. If this chamfer remains, the adhesive remains protruding in the process of joining both filters, and it also becomes a shadow when the target is presented. In order to prevent this, the two filters are bonded and then polished simultaneously to produce the same thickness.

  First, the change in transmission characteristics when the thickness of the green filter “G530” manufactured by HOYA, which is a commercial product, is changed as the green filter will be described. “G530” manufactured by HOYA is provided with a thickness of 2.5 mm. The transmission characteristic is shown by a graph 64a in FIG. 9, and the peak wavelength is about 20% in the vicinity of the wavelength of 530 nm. In FIG. 9, a graph 64b shows transmission characteristics when the thickness of “G530” manufactured by HOYA is 1.3 mm (this is the same as the graph 54 in FIG. 6), and the transmittance peak is about 30%. It has become. Graph 64c shows the transmission characteristics when the thickness of “G530” manufactured by HOYA is set to 2.2 mm, and the peak of transmittance is reduced to about 22%.

  The transmittance Tb when the transmittance at the thickness ta of the filter is Ta, and the thickness is changed to tb with the same material,

It is calculated by the relational expression.

  Using the above formula, the visual characteristics were obtained when the thickness of “G530” manufactured by HOYA was changed from 1.3 mm to 2.5 mm at intervals of 0.1 mm. FIG. 10 is a diagram showing visual characteristics when white LEDs are used. The visual characteristic when the thickness of “G530” is 1.3 mm is shown by a graph 74b. On the other hand, the visual characteristic when the thickness of “G530” is 2.2 mm is shown by a graph 74c. The graph 74a shows the visual characteristics with the thickness of “G530” being 2.5 mm. The results of the visual characteristics for other thicknesses are not shown. As shown in FIG. 10, it can be seen that the green component is weakened by making the thickness of “G530” thicker than 1.3 mm.

  Next, a method for enhancing the red component will be described. A red filter which is a commercially available Sharp Cut Filter “R62” manufactured by HOYA is provided with a thickness of 2.5 mm. The transmission characteristic (thickness: 2.5 mm) of “R62” manufactured by HOYA is shown by a graph 66 in FIG. 11. The transmittance in the wavelength region exhibiting red is 90% or more, and the transmittance of the red component is high. For this reason, even if the thickness of the red filter is reduced, the change in transmittance is small, and the red component cannot be strengthened so much. Therefore, in order to strengthen the red component, a red filter having a transmission region shifted to the short wavelength side with respect to the wavelength characteristic of “R62” manufactured by HOYA is used.

  A graph 68 in FIG. 11 shows transmission characteristics of a red filter “RG610” manufactured by SCHOTT. “RG610” manufactured by SCHOTT Co., Ltd. is provided with a thickness of 3.0 mm, has a transmittance of almost 0 on the shorter wavelength side than the wavelength of 590 nm, has a transmittance of 80% or more on the longer wavelength side of the wavelength of 630 nm, and is 50%. The transmittance is in the vicinity of a wavelength of 610 nm. In the “RG610” manufactured by SCHOTT, the wavelength at which the transmittance sharply decreases (wavelength near the transmittance of 50%) is shifted to the short wavelength side by about 10 nm compared to “R62” manufactured by HOYA. As a result, the transmitted red component is stronger than “R62”.

  A commercially available red filter is “R60” manufactured by HOYA. This red filter has a wavelength of about 600 nm in which the wavelength near the transmittance of 50% is further shifted to the short wavelength side by about 10 nm than “RG610” manufactured by SCHOTT Co., Ltd. at a thickness of 2.5 mm. The wavelength region to be short is shorter than the wavelength of 580 nm and has a transmittance of 80% or higher on the longer wavelength side of 620 nm or longer. This “R60” manufactured by HOYA can also be used as a red filter, but the component that looks orange is slightly stronger. As a red filter, it is preferable that a wavelength region having a transmittance of 50% or more is at least near a wavelength of 600 to 620 nm.

  The visual characteristics when the thickness of the red filter “RG610” manufactured by SCHOTT is 2.2 mm is shown by a graph 76 in FIG. Incidentally, a graph 78 in FIG. 10 shows the visual characteristics of “R62” manufactured by HOYA having a thickness of 1.3 mm, which was used in the case of a halogen lamp. Comparing the areas of the graphs 76 and 78, it can be seen that the graph 76 is wider and the red component is strengthened. Regarding the red filter, the intensity of the red component does not change so much even if the thickness is changed in any case.

  As described above, “G530” manufactured by HOYA is used as a green filter, and “RG610” manufactured by SCHOTT is used as a red filter. The thickness t was calculated so as to be the same. When the thickness t of both HOYA “G530” and SCHOTT “RG610” is 2.2 mm, the luminance ratio of green (area of graph 74) to red (area of graph 76) is 1: 1.5. The brightness ratio of the conventional halogen lamp was approached.

  As described above, the commercially available green filter “G530” manufactured by HOYA has a thickness of 2.5 mm, and after joining the red filter and the green filter, the back surface and the surface of both filters are respectively attached. Considering the polishing process to reduce the thickness by polishing, the thickness is about 2.2 mm from the viewpoint of ease of manufacture. Even in this case, the brightness of the red background 11 and the green background 13 is sufficiently recognized and sufficient for practical use. More preferably, the thickness t can be up to 2.4 mm by performing the polishing process after joining both filters with high accuracy. In this case, the luminance ratio of green to red is 1: 1.3, and the brightness of both can be made the same even for those used in conventional halogen lamps. It can be said that the range in which the visual characteristics of red and green are substantially the same is almost satisfactory if the luminance ratio of green to red is in the range of 1: 0.8 to 1: 1.6.

  In the above embodiment, “G530” manufactured by HOYA was used as the green filter, and “RG610” manufactured by SCHOTT was used as the red filter. Absent. For example, as a commercially available green filter exhibiting a green color, “G545” manufactured by HOYA can be used. The transmission characteristics when the thickness of the filter is 2.5 mm are shown in FIG. Looking at this transmission characteristic, the center wavelength of green is shifted to the longer wavelength side by about 10 nm with respect to the transmission characteristic of “G530” manufactured by HOYA shown in FIG. 9, and the range of the transmission region is 500 to 600 nm. It has become. The peak wavelength is 540 to 550 nm, and the transmittance is 10 to 15% at a thickness of 2.5 mm. In this case, although it is slightly closer to yellowish green, the transmittance peak is lower than that of “G530” manufactured by HOYA, so by adjusting the thickness of the filter (even if the thickness t is 2.2 mm in the practical range). Further, the green component can be weakened. In addition, when using “G545” manufactured by HOYA, “R62” manufactured by HOYA is used as a red filter, and the thickness t of both is 2.2 mm in the practical range, which is almost the same as the previous embodiment. Results.

  Further, commercially available red filters and green filters are not limited to the above, and even commercially available green filters and red filters of other manufacturers can be used as long as their wavelength regions are close to those described above. As for the red filter, when using a filter with a red wavelength region peak transmittance of less than 70% at a thickness of 3 mm, the change in the transmittance due to the reduction of the filter thickness also increases. As the filter thickness changes, the thickness is determined so that the visual characteristics of red and green are substantially the same.

  As described above, an example of a target presentation apparatus that projects a target on the screen 8 placed at a predetermined distance from the subject has been described. It can also be applied to the space-saving type described in the 87760 publication. This type of apparatus has a chart disk plate and mask plate similar to those in the optical system of FIG. 1 in a housing, and these are illuminated by an illumination light source, and optically by a concave mirror and a half mirror disposed in the same housing. The target is placed at a distant distance such as 5 m. In this case as well, a white LED is used as an illumination light source, and red and green inspection red and green filters arranged on the mask plate are used as described above to appropriately perform red and green inspection. Can do.

It is a figure which shows the optical system of a projection type target presentation apparatus. It is a figure which shows the target and filter of a red-green test | inspection. It is a figure explaining the light emission characteristic of an illumination light source. It is a figure explaining the visual efficiency of a human eye. It is a figure explaining the visual characteristic of a human eye. It is a figure explaining the transmission characteristic of the filter for halogen lamps. It is a figure explaining the visual characteristic of a red-green target when a halogen lamp is used as a light source. It is a figure explaining the visual characteristics at the time of using a filter for halogen lamps when white LED is used as a light source. It is a figure explaining the transmission characteristic of a green filter. It is a figure explaining the visual characteristics in each filter. It is a figure explaining the difference in the transmission characteristic by the classification of a red filter. It is a figure explaining the transmission characteristic of another kind of red filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illumination light source 5 Mask board 8 Projection screen 10 Red-green inspection target 31 Red filter 32 Joint part 33 Green filter

Claims (2)

A test target in which various test targets including a predetermined target for red-green test are formed is arranged by switching to the optical path, and a red filter and a green filter for dividing the presentation screen are arranged by switching to the presentation optical path, In the optotype presenting apparatus that illuminates the red filter and the green filter from behind with an illumination light source, and presents a red-green inspection optotype having an optotype in a red background and a green background,
As the illumination light source , a white LED having a light emission characteristic in which a light emission component in the green wavelength region is stronger than a light emission component in the red wavelength region is provided,
As the red filter and the green filter, a red filter and a green filter having different changes in visual characteristics with respect to a change in the thickness of each filter when the white LED is used are used , and shadows are generated at the joint portion of both filters. the thickness of both filters as red and green visual characteristics are substantially the same when the thickness of both filters is adjusted to the same and present a red-green test chart and the illumination of the white LED in order to keep An optotype presenting apparatus comprising a filter manufactured by determining the length. The visual target presenting device according to claim 1, wherein the red and green filters have substantially the same red and green visual characteristics when a red-green test target is presented by illumination of the white LED at the same thickness. A visual target characterized in that a red filter and a green filter having the same transmittance change are determined from commercially available ones, and both filters are bonded and polished simultaneously to provide a filter manufactured with the same thickness. Presentation device.