Optical characteristic measuring optical system and optical characteristic measuring apparatus

Abstract

To provide an optical characteristic measuring optical system and an optical characteristic measuring apparatus that can obtain a two-dimensional image close to a viewed image as well as measuring optical characteristics of an object to be measured.SOLUTION: An optical characteristic measuring optical system has a first optical system (11) which captures an infinite conjugate image and a second optical system (12) which captures a conjugate image of an object to be measured. The first optical system (11) and second optical system (12) share a first lens group (G1), and are arranged on two optical axes divided by an optical element (5) deflecting an optical axis respectively to constitute one measurement optical system. Further, the second optical system (12) has its aperture diaphragm arranged nearby intermediate image formation. Here, -1.0<Δp / f1<3.0 holds for the distance Δp from an image-side paraxial focus of a first lens group (G1) to the aperture diaphragm and the focal length f1 of the first lens group.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical characteristic measuring optical system and an optical characteristic measuring device. [Background technology]

[0002] In recent years, coating and decoration technologies have been developed to meet the need for improved design in ICT products such as smartphones and industrial products such as automobiles. For example, coating technologies have been developed that exhibit complex reflective properties, such as metallic paint on automobile exteriors, which look different depending on the viewing angle or the direction of light.

[0003] When evaluating the appearance of a surface with such reflective properties, conventional colorimeters or glossmeters can only evaluate under certain conditions, so it is difficult to say that they can fully evaluate the appearance of the surface. To evaluate complex reflective properties, it is necessary to evaluate the Bidirectional Reflectance Distribution Function (BRDF), which represents the reflective angle characteristics that depend on the illumination angle or the receiving angle. By evaluating the BRDF, it is possible to quantitatively evaluate the difference in appearance depending on the way the light hits the surface and the observation direction.

[0004] Furthermore, when evaluating metallic paints, there is a demand to evaluate the distribution of glittering materials (such as aluminum flakes) contained in the paint. For this reason, there is a demand not only to be able to evaluate the reflective properties of the paint surface, but also to be able to obtain two-dimensional images of the paint surface.

[0005] Goniophotometers are commonly used as devices for measuring BRDF. However, when measuring BRDF, it is necessary to move the illumination and measurement parts of the goniophotometer. For this reason, measuring BRDF using a goniophotometer has the following issues: 1) it takes time to measure, 2) it measures discrete illumination and reception angles, and 3) the measurement device is large. There is a demand for a measuring device that can measure BRDF in a short time and is compact. Furthermore, there is a demand for the measuring device to be able to obtain two-dimensional images of the measurement target.

[0006] As an invention that meets these demands, WO 2006 / 050978 (Patent Document 1) discloses a reflection angle characteristic device that uses a relay-type Fourier transform optical system. According to this invention, the BRDF of the measurement target can be measured in one shot. Furthermore, Example 4 (FIG. 5) of WO 2006 / 050978 discloses an optical system that can acquire a two-dimensional image of the measurement target surface. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2006 / 050978 Summary of the Invention [Problem to be solved by the invention]

[0008] The device disclosed in WO 2006 / 050978 has a problem in that an image of a measurement target acquired by an optical system for acquiring a two-dimensional image deviates from the appearance of the measurement target when a person visually views the measurement target. According to WO 2006 / 050978, a lens 3 having a positive power and a lens 13 having a positive power are arranged to sandwich an intermediate image position (Fourier plane 9). These lenses 3 and 13 are lenses common to the BRDF measurement optical system and the optical system for acquiring a two-dimensional image. The intermediate image position corresponds to the focal position of the lens 3.

[0009] If there is an aperture stop at the focal position of the lens 3, the chief ray becomes parallel to the optical axis on the measurement object side, so that the optical system for acquiring a two-dimensional image becomes a so-called object-side telecentric optical system. However, according to WO 2006 / 050978, the aperture stop in the optical system for acquiring a two-dimensional image is located at a position far away from the intermediate image formation position. As a result, since the optical system for acquiring a two-dimensional image is not an object-side telecentric optical system, the observation angle is greatly inclined at the periphery of the measurement area. On the other hand, when a person looks at an object, he or she sees light that is generally nearly parallel to the line of sight. Therefore, the image captured by the optical system disclosed in WO 2006 / 050978 deviates from the appearance when viewed with the naked eye.

[0010] The present invention has been made in consideration of these problems, and aims to provide an optical property measurement optical system and an optical property measurement device that are capable of not only measuring the optical properties of the object to be measured, but also acquiring two-dimensional images that are close to those seen with the naked eye. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, an optical characteristic measurement optical system according to one aspect of the present invention is an optical characteristic measurement optical system for measuring reflected light from a measurement object, and comprises a first optical system and a second optical system for measuring a common measurement object, the first optical system consisting of, in order from the object side, a first lens group having positive power, a second lens group having positive power, an aperture stop, a first image sensor, and an illumination light source, and is a relay optical system that forms an intermediate image between the first lens group and the second lens group, the aperture stop is disposed in the second lens group so that its entrance pupil is on the object side of the first lens group, the measurement object is disposed near the entrance pupil of the aperture stop, the first image sensor is disposed conjugate to object-side infinity, and the second optical system consists of, in order from the object side, a first lens group common to the first optical system, a third lens group having positive power, and a second image sensor, and the second image sensor is disposed at a position conjugate to the measurement object. If the distance in the optical axis direction from the image-side paraxial focal point of the first lens group to the aperture stop is Δp and the focal length of the first lens group is f1, the following conditional formula (1) is satisfied, -1.0<Δp / f1<3.0 (1) The first optical system and the second optical system share the first lens group, and the optical property measurement optical system further has an optical element that deflects the optical axis toward the image side of the first lens group, the optical axis being branched into two directions by the optical element, the first optical system being disposed in the first of the two directions, and the second optical system being disposed in the second of the two directions.

[0012] Preferably, the optical property measuring optical system has an intermediate image formed by the first lens group, another optical element that deflects the optical axis between the first image sensor, and a light source that can emit light to any minute area on the surface at a position conjugate to the other object-side infinity to which the optical axis is deflected by the other optical element.

[0013] Preferably, when the distance between the first lens group and the second lens group is L and the effective diameter of the largest lens in the first lens group is φ1, the following conditional expression (2) is satisfied.

[0014] 0.4 <L / φ1<3.0 ···(2) Preferably, in the first optical system, when the angle of the light ray reflected from the center of the measurement object is θ and the position at which the light ray reaches the image sensor is Y(θ), θ and Y(θ) have an approximately proportional relationship, and when the maximum image height is Ymax and the maximum light ray angle is θmax, the following conditional formula (3) is satisfied: −0.1<(Y(θmax / 2)-Ymax / 2) / Ymax<0.1 (3) is satisfied.

[0015] Preferably, the optical characteristic measuring optical system further includes a light source arranged around the aperture stop of the second optical system and capable of illuminating the measurement object when the measurement object is imaged by the second optical system.

[0016] Preferably, when the back focus of the first optical system is fB and the effective diameter of the surface of the second lens group closest to the image side is φ2, fB / φ2 satisfies the following conditional expression (4).

[0017] 1.0 <fB / φ2<3.0 ···(4) In another aspect of the present invention, an optical characteristic measuring device includes any one of the optical characteristic measuring optical systems described above, and has a function of measuring the optical characteristics of a measurement object and a function of imaging the measurement object. Effect of the Invention

[0018] According to the present disclosure, it is possible to provide an optical property measuring optical system and an optical property measuring device that are capable of measuring the optical properties of a measurement target and also of acquiring a two-dimensional image close to that seen with the naked eye. [Brief description of the drawings]

[0019] [Figure 1] 1 is a diagram showing a configuration of an optical characteristic measuring optical system according to a first embodiment. [Figure 2A] FIG. 2 is a diagram showing a first optical system of an optical characteristic measuring optical system according to the first embodiment. [Figure 2B] FIG. 2 is a diagram showing a second optical system of the optical characteristic measuring optical system according to the first embodiment. [Diagram 3] FIG. 13 is a diagram showing a configuration of an optical characteristic measuring optical system according to a second embodiment. [Figure 4A] FIG. 13 is a diagram showing a first optical system of an optical characteristic measuring optical system according to a second embodiment. [Figure 4B] FIG. 13 is a diagram showing a second optical system of an optical characteristic measuring optical system according to a second embodiment. [Diagram 5] FIG. 13 is a diagram showing a configuration of an optical characteristic measuring optical system according to a third embodiment. [Figure 6A] FIG. 13 is a diagram showing a first optical system of an optical characteristic measuring optical system according to a third embodiment. [Figure 6B] FIG. 13 is a diagram showing a second optical system of an optical characteristic measuring optical system according to a third embodiment. [Figure 7] 1 is a schematic diagram illustrating the configuration of an optical characteristic measuring apparatus including an optical characteristic measuring optical system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. An optical property measuring optical system according to the embodiment of the present invention has a first optical system that captures an infinite conjugate image and a second optical system that captures a conjugate image of a measurement target. The first optical system and the second optical system share a first lens group and are arranged on two optical axes separated by an optical element that deflects the optical axis, forming a single measuring optical system.

[0021] Furthermore, the aperture stop of the second optical system is disposed near the intermediate image. Specifically, if the distance in the optical axis direction from the image-side paraxial focal point of the first lens group to the aperture stop is Δp and the focal length of the first lens group is f1, then Δp / f1 satisfies the following conditional expression.

[0022] -1.0<Δp / f1<3.0 By satisfying the above condition, the aperture stop of the second optical system is located near the intermediate image, so that the observation angle of the second optical system can be made close to parallel, which makes it possible to measure the optical characteristics of the object to be measured and to obtain a two-dimensional image close to that seen with the naked eye.

[0023] To explain in more detail, an optical characteristic measurement optical system according to an embodiment of the present invention is an optical characteristic measurement optical system for measuring reflected light from a measurement object, and comprises a first optical system and a second optical system for measuring a common measurement object. The first optical system is a relay optical system that forms an intermediate image between the first lens group and the second lens group, and consists of, from the object side, a first lens group having positive power, a second lens group having positive power, an aperture stop, a first image sensor, and an illumination light source. The aperture stop is disposed in the second lens group so that its entrance pupil is on the object side of the first lens group. The measurement object is disposed near the entrance pupil of the aperture stop. The first image sensor is disposed conjugate to object-side infinity. The second optical system is, from the object side, a first lens group common to the first optical system, a third lens group having positive power, and a second image sensor, and the second image sensor is disposed at a position conjugate to the measurement object.

[0024] If the distance in the optical axis direction from the image-side paraxial focal point of the first lens group to the aperture stop is Δp and the focal length of the first lens group is f1, the following conditional expression is satisfied.

[0025] -1.0<Δp / f1<3.0 (1) The first optical system and the second optical system share the first lens group, and the optical property measurement optical system further has an optical element that deflects the optical axis toward the image side of the first lens group, the optical axis being branched into two directions by the optical element, the first optical system being disposed in the first of the two directions, and the second optical system being disposed in the second of the two directions.

[0026] By having the above-mentioned configuration of the first optical system, the first imaging element is placed at an infinite conjugate position, and the first optical system becomes an optical system (i.e., a Fourier transform optical system) in which the coordinates on the imaging surface of the first imaging element are determined according to the angle of the light ray incident from the object side. Due to this characteristic, the angular distribution of the reflected light from the measurement object can be imaged on the imaging surface of the first imaging element. Furthermore, by placing the aperture stop so that the entrance pupil is located closest to the object side and placing the measurement object near the entrance pupil, it is possible to measure approximately the same position for all reflection angles.

[0027] Because the first lens group forms an image of light rays at an extremely wide angle of about 80°, it is difficult to correct various aberrations, particularly the field curvature and distortion that become larger as the angle becomes wider, using only the first lens group. By making the first optical system a relay optical system, the aberrations that occur in the first lens group can be corrected by the second lens group, maintaining good aberration performance.

[0028] Furthermore, by configuring the second optical system as described above, the second image sensor can capture a two-dimensional image of the measurement target. By arranging the aperture stop so as to satisfy conditional formula (1), the aperture stop can be arranged near the intermediate image position and the entrance pupil is moved away from the measurement target, so that the second optical system has a configuration close to object-side telecentric. In an object-side telecentric optical system, the chief ray is parallel to the optical axis on the measurement target side. When a person looks at an object, he or she sees light that is generally close to parallel to the line of sight, so it is possible to obtain a two-dimensional image close to that seen with the naked eye.

[0029] Furthermore, by sharing the first lens group between the first and second optical systems and splitting the optical axis into two by an optical element and arranging the first and second optical systems in the respective directions, two different optical systems can be configured for the same measurement position. This makes it possible to simultaneously or consecutively obtain the reflection angle distribution and two-dimensional image, enabling measurements to be completed in a short time.

[0030] More preferably, the value Δp / f1 satisfies the following conditional expression (1)′. -0.8<Δp / f1<2.0...(1)' More preferably, the value Δp / f1 satisfies the following conditional expression (1)″.

[0031] -0.6<Δp / f1<1.5...(1)'' In an embodiment of the present invention, the optical property measuring optical system may have an intermediate image formed by the first lens group and another optical element that deflects the optical axis between the first image sensor, and a light source that can illuminate any minute area on a surface at a position conjugate to the other object-side infinity to which the optical axis is deflected by the other optical element.

[0032] Since the optical system closer to the object than the additional optical elements also functions as the illumination optical system, there is no need to provide a separate optical system for illumination. This simplifies the optical system. Furthermore, by having a light source that can emit light to any minute area on the surface at a position conjugate to infinity on the object side, it is possible to illuminate the measurement object with parallel light having an angle according to the position of emission. This allows the measurement object to be illuminated at any angle, making it possible to measure the BRDF in more detail.

[0033] In an embodiment of the present invention, if the distance between the first and second lens groups is L and the effective diameter of the largest lens in the first lens group is φ1, it is preferable to satisfy the following conditional expression (2).

[0034] 0.4 <L / φ1<3.0 ···(2) When the value of L / φ1 exceeds the lower limit of conditional expression (2), a sufficient distance can be provided between the first lens group and the second lens group, making it easier to place an optical element that deflects the optical axis and an aperture stop between the first lens group and the second lens group. On the other hand, when the value of L / φ1 is below the upper limit of conditional expression (2), it is possible to avoid an unnecessarily large total optical length, thereby preventing an increase in the size of the measuring device.

[0035] More preferably, the value L / φ1 satisfies the following conditional expression (2)′. 0.5 <L / φ1<2.5 ···(2)‘ More preferably, the value L / φ1 satisfies the following conditional formula (2)″.

[0036] 0.6 <L / φ1<2.0 ···(2)‘‘ In the first optical system, when the angle of the light ray reflected from the center of the object to be measured is θ and the position at which the light ray reaches the image sensor is Y(θ), θ and Y(θ) are in an approximately proportional relationship. If the maximum image height is Ymax and the maximum light ray angle is θmax, the following conditional formula (3) is satisfied: It is preferable to satisfy −0.1<(Y(θmax / 2)−Ymax / 2) / Ymax<0.1 (3).

[0037] When θ and Y(θ) are approximately proportional to each other and (Y(θmax / 2)-Ymax / 2) / Ymax satisfies the upper and lower limits of the range determined by conditional formula (3), the angular distribution of the reflection from the measurement object is imaged as the illuminance distribution on the image sensor almost as it is. This makes it easy to perform correction calculations to convert the position on the image sensor to the angle of reflection from the measurement object.

[0038] It is more preferable that (Y(θmax / 2)−Ymax / 2) / Ymax satisfies the following conditional expression (3)′.

[0039] -0.08<(Y(θmax / 2)-Ymax / 2) / Ymax<0.08 ···(3)' It is even more preferable that (Y(θmax / 2)−Ymax / 2) / Ymax satisfies the following conditional expression (3)″.

[0040] -0.05<(Y(θmax / 2)-Ymax / 2) / Ymax<0.05 ···(3)'' In an embodiment of the present invention, the optical characteristic measuring optical system may have a light source arranged around the aperture stop of the second optical system and capable of illuminating the measurement target when the measurement target is imaged by the second optical system, thereby enabling the entire imaging range of the second optical system to be uniformly illuminated, thereby enabling an image closer to that seen by the naked eye to be obtained.

[0041] In an embodiment of the present invention, when the back focus of the first optical system is fB and the effective diameter of the surface of the second lens group closest to the image side is φ2, it is preferable that fB / φ2 satisfies the following conditional expression (4).

[0042] 1.0 <fB / φ2<3.0 ···(4) Conditional expression (4) is a condition for disposing an optical element between the intermediate image formed by the first lens group and the first image sensor, and in the back focus portion of the first optical system. When conditional expression (4) is satisfied, the entire first optical system can also be used as an illumination optical system, eliminating the need for additional lenses. This further simplifies the configuration of the optical system.

[0043] When fB / φ2 exceeds the lower limit of conditional expression (4), the back focus becomes longer. This makes it possible to minimize the vignetting of light rays and to arrange optical elements. On the other hand, when fB / φ2 falls below the upper limit of conditional expression (4), it is possible to prevent the total optical length from becoming unnecessarily large, and therefore it is possible to miniaturize the measuring device.

[0044] It is more preferable that fB / φ2 satisfies the following conditional expression (4)′. 1.3 <fB / φ2<2.8 ···(4)‘ More preferably, fB / φ2 satisfies the following conditional formula (4)″.

[0045] 1.6 <fB / φ2<2.6 ···(4)‘‘ In an embodiment of the present invention, it is preferable that the optical property measuring device includes any one of the optical property measuring optical systems described above, and has a function of measuring the optical property of a measurement object and a function of imaging the measurement object. This makes it possible to obtain a two-dimensional image close to that seen with the naked eye in addition to measuring the optical property (reflection property) of the measurement object. In addition, it is possible to prevent the optical property measuring device from becoming large.

[0046] (Configuration of optical system for measuring optical characteristics) The configuration of an optical characteristic measuring optical system according to an embodiment of the present invention will be described with reference to Figs. 1 to 6B. Figs. 1 to 6B are diagrams showing the configuration of an optical characteristic measuring optical system according to first to third embodiments, respectively. In Figs. 1 to 6B, the first to third embodiments are denoted as "EX1", "EX2", and "EX3", respectively.

[0047] (First embodiment) 1 to 2B, the optical characteristic measuring optical system according to the first embodiment includes a first optical system 11 and a second optical system 12 that measure a common measurement target M. Fig. 2A is a diagram showing only the first optical system 11, and Fig. 2B is a diagram showing only the second optical system 12.

[0048] The first optical system 11 consists of, in order from the object side, a first lens group G1 having positive power, a second lens group G2 having positive power, an aperture stop S1, a first image sensor (not shown), and an illumination light source (not shown).

[0049] The first lens group G1 is made up of lenses L1, L2, and L3. The second lens group G2 is made up of lenses L4, L5, L6, L7, L8, and L9. The first optical system 11 is a relay optical system that forms an intermediate image between the first lens group G1 and the second lens group G2.

[0050] The aperture stop S1 is disposed in the second lens group G2. The entrance pupil of the aperture stop S1 is directed toward the object side of the first lens group G1. The measurement target M is disposed near the aperture stop S1.

[0051] The first imaging element is disposed conjugate with object-side infinity. Therefore, the first optical system 11 is an optical system that captures an image of the object M at infinity conjugate. In FIG. 1, an image plane IM1 is shown instead of the first imaging element (this also applies to the figures described below). A light-shielding diaphragm S3 is provided in front of the first imaging element (image plane IM1).

[0052] The second optical system 12 is composed of, in order from the object side, a first lens group G1, a third lens group G3 having a positive power, and a second image sensor (not shown). The first lens group G1 is common to the first optical system 11. The third lens group G3 is composed of lenses L11, L12, and L13.

[0053] The second imaging element is disposed at a position conjugate with the measurement object. Therefore, the second optical system captures a conjugate image of the measurement object M. In FIG. 1, an image plane IM2 is shown instead of the second imaging element.

[0054] The aperture stop S1 is disposed near the intermediate imaging position so as to satisfy the conditional expression (1). In the first embodiment, the aperture stop S1 is disposed closer to the object (measurement target M) side than the intermediate imaging position. This results in the second optical system 12 being configured to be nearly object-side telecentric. This makes it possible to obtain a two-dimensional image that is close to what one would see with the naked eye.

[0055] The optical characteristic measuring optical system further includes an optical element 5 that deflects the optical axis AX toward the image side of the first lens group G1. Specifically, the optical element 5 branches the optical axis AX into an optical axis AX1 and an optical axis AX2. The direction of the optical axis AX1 and the direction of the optical axis AX2 are different from each other. A first optical system 11 is disposed in the direction of the optical axis AX1, and a second optical system 12 is disposed in the direction of the optical axis AX2.

[0056] The type of the optical element 5 is not particularly limited, and for example, a beam splitter, a half mirror, or the like can be used as the optical element 5. The optical element 5 may be a mirror having the size of the aperture of the aperture stop S1 and capable of being inserted and removed. This mirror is removed when imaging by the first optical system 11, and is inserted when imaging by the second optical system 12. Alternatively, the optical element 5 may be a beam splitter having a reflection-enhancing film formed to the size of the aperture of the aperture stop S1. Note that, although the aperture stop S1 and the optical element 5 are shown in substantially the same position in FIG. 1, when the optical element 5 is a removable mirror, the optical element 5 and the aperture stop S1 may be arranged so as not to impede the movement of the optical element 5.

[0057] The optical characteristic measurement optical system may further include an optical element 7 and a light source 8. The optical element 7 deflects an optical axis AX1 between the intermediate image formed by the first lens group G1 and the first image sensor. In FIG. 1, the optical axis AX3 corresponds to the optical axis deflected from the optical axis AX1 by the optical element 7. The position of the light source 8 is a position conjugate with the object-side infinity on the optical axis AX1 (i.e., the optical axis AX3) deflected by the optical element 7. It should be noted that although the optical element 7 and the light source 8 are shown in FIG. 1, their positions in FIG. 1 may not necessarily be accurate.

[0058] The optical element 7 may be, for example, a beam splitter, a half mirror, etc. The light source 8 is an element that can emit light in any minute area on the surface. Although not particularly limited, the light source 8 may be, for example, a micro display.

[0059] The optical characteristic measuring optical system may further include a light source 9 arranged around the aperture stop S1 of the second optical system 12 to illuminate the measurement target when the measurement target is imaged by the second optical system 12. The light source 9 may be, for example, a ring illumination. The light source 9 uniformly illuminates the entire imaging range of the second optical system 12. Note that although the light source 9 is shown in FIG. 1, the position of the light source 9 in FIG. 1 may not be exactly the same.

[0060] According to the first embodiment, the above configuration makes it possible to measure the optical characteristics of the measurement target, and also to obtain a two-dimensional image close to that seen with the naked eye.

[0061] (Second embodiment) 3 to 4B, the optical characteristic measuring optical system according to the second embodiment includes a first optical system 11 and a second optical system 12 that measure a common measurement target M. Fig. 4A is a diagram showing only the first optical system 11, and Fig. 4B is a diagram showing only the second optical system 12.

[0062] The first optical system 11 consists of, in order from the object side, a first lens group G1 having positive power, a second lens group G2 having positive power, an aperture stop S1, a first image sensor (not shown), and an illumination light source (not shown).

[0063] The first lens group G1 is made up of lenses L1, L2, L3, and L4. The second lens group G2 is made up of lenses L5, L6, L7, L8, and L9. In this respect, the second embodiment differs from the first embodiment.

[0064] The aperture stop S1 is disposed near the intermediate imaging position so as to satisfy conditional expression (1). In the second embodiment, the aperture stop S1 is disposed closer to the object (measurement target M) than the intermediate imaging position. The aperture stop S1 is disposed closer to the object (measurement target M) than the optical element 5. In this respect, the second embodiment differs from the first embodiment. However, since the aperture stop S1 is disposed so as to satisfy conditional expression (1), the second optical system 12 has a configuration close to object-side telecentric, as in the first embodiment. Therefore, in the second embodiment as well, it is possible to obtain a two-dimensional image close to that seen with the naked eye.

[0065] In the second embodiment, the aperture stop S1 and the optical element 5 are inserted and removed together. When capturing an image of the first optical system 11, both the aperture stop S1 and the optical element 5 are retracted from the optical path. When capturing an image of the second optical system 12, both the aperture stop S1 and the optical element 5 are inserted. In the second embodiment, the optical element 5 can be a beam splitter or a mirror.

[0066] Other configurations of the optical characteristic measuring optical system according to the second embodiment are similar to those of the optical characteristic measuring optical system according to the first embodiment, and therefore the following description will not be repeated. In the second embodiment, in addition to measuring the optical characteristics of the object to be measured, it is also possible to obtain a two-dimensional image close to that seen with the naked eye. Although the optical element 7, the light source 8, and the light source 9 are not shown in FIG. 3, these elements can also be added to the optical characteristic measuring optical system according to the second embodiment.

[0067] (Third embodiment) As shown in Figures 5 to 6B, the optical characteristic measuring optical system according to the third embodiment includes a first optical system 11 and a second optical system 12 that measure a common measurement target M. Figure 6A is a diagram showing only the first optical system 11, and Figure 6B is a diagram showing only the second optical system 12.

[0068] The first optical system 11 is composed of, in order from the object side, a first lens group G1 having a positive power, a second lens group G2 having a positive power, an aperture stop S1, a first image sensor (not shown), and an illumination light source (not shown). As in the first embodiment, the first lens group G1 is composed of lenses L1, L2, and L3. The second lens group G2 is composed of lenses L4, L5, L6, L7, L8, and L9.

[0069] In the third embodiment, an aperture formed in the housing 15 of the first optical system 11 is used as the aperture stop S1. The aperture stop S1 is disposed near the intermediate image position so as to satisfy the conditional expression (1). In the third embodiment, the aperture stop S1 is disposed closer to the image side than the intermediate image position. The aperture stop S1 is disposed closer to the image side than the optical element 5. Specifically, the aperture stop S1 is disposed on the second optical axis (optical axis AX2). In these respects, the third embodiment differs from the first and second embodiments. However, since the aperture stop S1 is disposed so as to satisfy the conditional expression (1), the second optical system 12 has a configuration close to object side telecentric, as in the first and second embodiments. Therefore, in the third embodiment, it is possible to obtain a two-dimensional image close to that seen by the naked eye. In the third embodiment, a beam splitter or a removable mirror can be used for the optical element 5. When the optical element 5 is a removable mirror, the optical element 5 is retracted from the optical path when the first optical system 11 captures an image, and is inserted when the second optical system 12 captures an image.

[0070] Other configurations of the optical characteristic measuring optical system according to the third embodiment are similar to those of the optical characteristic measuring optical system according to the first and second embodiments, and therefore the following description will not be repeated. In the third embodiment, in addition to measuring the optical characteristics of the measurement object, it is also possible to obtain a two-dimensional image close to that seen with the naked eye. Although the optical element 7, the light source 8, and the light source 9 are not shown in FIG. 5, these elements can also be added to the optical characteristic measuring optical system according to the third embodiment. EXAMPLES

[0071] The configuration of the optical characteristic measuring optical system according to the embodiment of the present invention will be described in more detail below with reference to the construction data of the examples. Examples 1 to 3 (EX1 to 3) given here are numerical examples corresponding to the above-mentioned first to third embodiments, respectively, and the lens configuration diagrams (FIGS. 1 to 6B) representing the first to third embodiments show the optical configurations (lens arrangement, lens shape, etc.) of the corresponding Examples 1 to 3, respectively.

[0072] In the construction data for each example, the surface data is shown in the left column as follows: surface number, radius of curvature (mm), axial surface spacing (mm), refractive index for the d-line (wavelength 587.56 nm), Abbe number for the d-line, and effective radius (mm). Note that "inf" in the table is an abbreviation for "infinity."

[0073] [Numerical Example 1] <1st optical system> The lens data and characteristics (various values) of the first optical system are shown in Tables 1 and 2. Note that the surface numbers in Table 1 are assigned in order from the object side (this also applies to the tables described below).

[0074] [Table 1]

[0075] [Table 2]

[0076] <Second optical system> The lens data and characteristics (various values) of the second optical system are shown in Tables 3 and 4.

[0077] [Table 3]

[0078] [Table 4]

[0079] [Numerical Example 2] <1st optical system> Tables 5 and 6 show the lens data and characteristics (various values) of the first optical system.

[0080] [Table 5]

[0081] [Table 6]

[0082] <Second optical system> Tables 7 and 8 show the lens data and characteristics (various values) of the second optical system.

[0083] [Table 7]

[0084] [Table 8]

[0085] [Numerical Example 3] <1st optical system> The lens data and characteristics (various values) of the first optical system are shown in Tables 9 and 10.

[0086] [Table 9]

[0087] [Table 10]

[0088] <Second optical system> Tables 11 and 12 show the lens data and characteristics (various values) of the second optical system.

[0089] [Table 11]

[0090] [Table 12]

[0091] (Configuration of optical property measuring device) Fig. 7 is a schematic diagram of an optical characteristic measuring device including an optical characteristic measuring optical system according to an embodiment of the present invention. As shown in Fig. 7, an optical characteristic measuring device 100 includes an optical characteristic measuring optical system 101. The optical characteristic measuring optical system 101 has a first optical system 11 and a second optical system 12. The optical characteristic measuring optical system 101 can have the configuration of an optical system according to any one of the first to third embodiments described above.

[0092] The first optical system 11 has an illumination device 3, a first lens group G1, an aperture stop S1, a second lens group G2, and a first image sensor 21. The illumination device 3 is a device for illuminating a measurement object M. Furthermore, the first optical system 11 can have an optical element 7 and a light source 8 shown in FIG.

[0093] The second optical system 12 has a first lens group G1, a third lens group G3, an optical element 5, and a second imaging element 22. The first lens group G1 is common to the first optical system 11 and the second optical system 12. The second optical system 12 may have a light source 9 shown in FIG.

[0094] The optical characteristic measuring device 100 further includes a control unit 50, an input unit 51, an output unit 52, an IF (interface) unit 53, and a storage unit 54. The control unit 50 controls the optical characteristic measuring device 100. For example, the control unit 50 processes an image signal from the first imaging element 21. In this way, the control unit 50 obtains a BRDF. The control unit 50 further processes an image signal from the second imaging element 22 to generate image data of the measurement object M.

[0095] The input unit 51 is connected to the control unit 50. For example, the input unit 51 is a device that inputs, to the optical characteristic measuring apparatus 100, various commands such as a command specifying the measurement target M, and various setting information required for measuring the optical characteristics.

[0096] The output unit 52 is connected to the control unit 50. The output unit 52 is controlled by the control unit 50 and outputs the commands and data input by the input unit 51. Furthermore, the output unit 52 outputs the optical characteristics (reflection characteristics) of the measurement object M measured by the optical characteristic measuring apparatus 100.

[0097] For example, the output unit 52 may be a display or a printer. When the output unit 52 is a display, the output unit 52 displays an image of the measurement object M captured by the optical property measuring apparatus 100, in addition to the optical properties of the measurement object M. The input unit 51 and the output unit 52 may be realized by a touch panel.

[0098] The IF unit 53 is connected to the control unit 50. The IF unit 53 is a circuit that inputs and outputs data to and from an external device under the control of the control unit 50. The standard for data communication is not limited to a specific standard.

[0099] The storage unit 54 is connected to the control unit 50. The storage unit 54 is controlled by the control unit 50 and stores various predetermined programs and various predetermined data. The programs stored in the storage unit 54 may include, for example, a control program for controlling each unit of the optical property measuring device 100, an arithmetic program for calculating the reflection characteristic (BRDF), and the like. Furthermore, the storage unit 54 stores, for example, image data of the measurement object M acquired by the first imaging element 21 and image data of the measurement object M acquired by the second imaging element 22.

[0100] The above-described embodiment can be modified in various ways. Modifications included in the embodiment of the present invention will be described below.

[0101] (1) In the optical characteristic measuring apparatus 100 according to the embodiment of the present invention, the BRDF may be measured for each wavelength.

[0102] For this reason, it is preferable that the illumination device 3 (light source) of the first optical system 11 can emit light with a plurality of different spectra. Alternatively, the first imaging element 21 of the first optical system 11 may be capable of separately receiving a plurality of different spectra. The first imaging element 21 may be, for example, an RGB sensor. Filters having a plurality of different bandpass characteristics may be arranged in front of the first imaging element 21 so as to be replaceable.

[0103] (2) In the optical characteristic measuring apparatus 100 according to the embodiment of the present invention, a configuration for increasing the amount of illumination light and the amount of received light may be employed.

[0104] For example, a surface light source may be used as the illumination device 3 of the first optical system 11, and a microlens array may be disposed on the object side of the surface light source. For example, a microdisplay may be used as the light source for the illumination device 3. However, because a microdisplay has a wide light distribution characteristic, only a portion of the light emitted by the microdisplay can be used as illumination light. By combining a microlens array with a microdisplay, it is possible to give directionality to the light, thereby increasing the utilization efficiency of the light emitted from the microdisplay.

[0105] Alternatively, the optical element 5 that splits the optical axis of the first optical system 11 and the second optical system 12 may be a mirror arranged so as to be insertable and removable on the optical axis. If the optical element 5 that splits the optical axis is, for example, a half mirror with a reflectance of 50%, the amount of illumination light is halved by the half mirror. When the reflected light passes through the half mirror, the amount of light is further halved. As a result, the amount of received light is 1 / 4 or less of the amount of illumination light. Therefore, the optical element 5 may be a mirror that can be inserted and removed on the optical axis as described above. The mirror is removed when measuring the BRDF by the first optical system 11, and is inserted when imaging by the second optical system 12. This can substantially eliminate the loss of light amount as described above, and can increase the amount of illumination light and the amount of received light.

[0106] (3) In the optical characteristic measuring apparatus 100 according to the embodiment of the present invention, a configuration for further shortening the measurement time may be employed.

[0107] For example, the lighting device 3 may be configured to emit light from light-emitting positions corresponding to a plurality of angles simultaneously. The lighting device 3 may be a surface light-emitting element configured to emit light in any plurality of regions on the light-emitting surface simultaneously.

[0108] As the glossiness of the measurement target increases, the diffusivity of the reflected light decreases. However, by simultaneously emitting light from the lighting device 3 at light-emitting positions corresponding to multiple angles, it is possible to simultaneously measure the reflection characteristics at multiple angles. This allows the measurement time to be shortened.

[0109] (4) In the optical characteristic measuring apparatus 100 according to the embodiment of the present invention, configurations for performing measurements in accordance with various industrial standards may be employed.

[0110] For example, the lighting device 3 may be configured to emit light at all positions corresponding to a lighting angle of 45° in all azimuth angles. In this case, the lighting device 3 will perform 45° circular lighting. By measuring the amount of light reflected in the 0° direction at that time, it becomes possible to perform the same measurement as the color measurement of the 45°c:0° geometry defined in standards such as JIS.

[0111] Although the embodiment and examples of the present invention have been described, the embodiment disclosed herein should be considered as illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, and it is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0112] 3 illumination device, 5, 7 optical element, 8, 9 light source, 11 first optical system, 12 second optical system, 15 housing, 21 first imaging element, 22 second imaging element, 50 control unit, 51 input unit, 52 output unit, 53 IF unit, 54 memory unit, 100 optical characteristic measuring device, 101 optical characteristic measuring optical system, AX, AX1, AX2, AX3 optical axis, G1 first lens group, G2 second lens group, G3 third lens group, IM1 image plane, L1 to L9, L11, L12 lenses, M measurement object.

Claims

1. An optical characteristic measurement optical system for measuring reflected light from a measurement object, a first optical system and a second optical system for measuring a common measurement target; The first optical system includes, in order from the object side, a first lens group having a positive power; a second lens group having a positive power; and An aperture stop; A first imaging element; An illumination source; a relay optical system that forms an intermediate image between the first lens group and the second lens group, the aperture stop is disposed in the second lens group such that an entrance pupil of the aperture stop is on the object side of the first lens group; the measurement object is disposed near the entrance pupil of the aperture stop; the first image sensor is disposed conjugate to infinity on the object side; The second optical system includes, in order from the object side, the first lens group common to the first optical system; a third lens group having a positive power; and a second imaging element; The second imaging element is disposed at a position conjugate with the object to be measured, When a distance in the optical axis direction from an image-side paraxial focal point of the first lens group to the aperture stop is Δp and a focal length of the first lens group is f1, the following conditional expression (1) is satisfied: -1.0<Δp / f1<3.0...(1) the first optical system and the second optical system share the first lens group; the optical characteristic measuring optical system further includes an optical element that deflects an optical axis toward an image side of the first lens group, the optical axis being branched into two directions by the optical element, The first optical system is disposed in a first direction of the two directions, The second optical system is disposed in a second direction of the two directions.

2. another optical element that deflects an optical axis between an intermediate image formed by the first lens group and the first image sensor; The optical characteristic measuring optical system according to claim 1 , further comprising a light source capable of illuminating any minute area on a surface at a position conjugate with the other object-side infinity to which the optical axis is deflected by the other optical element.

3. If the distance between the first lens group and the second lens group is L and the effective diameter of the largest lens in the first lens group is φ1, the following conditional expression (2) is satisfied: 0.4<L / φ1<3.0...(2) 3. The optical characteristic measuring optical system according to claim 1, wherein

4. In the first optical system, when an angle of a light ray reflected from the center of the measurement object is defined as θ and a position at which the light ray reaches an image sensor is defined as Y(θ), θ and Y(θ) are in a substantially proportional relationship, If the maximum image height is Ymax and the maximum light ray angle is θmax, the following conditional expression (3) is satisfied: -0.1<(Y(θmax / 2)-Ymax / 2) / Ymax<0.1...(3) 4. The optical characteristic measuring optical system according to claim 1, wherein

5. The optical characteristic measuring optical system according to any one of claims 1 to 4, further comprising a light source arranged around the aperture stop arranged in the second optical system and capable of illuminating the measurement object when the measurement object is imaged by the second optical system.

6. If the back focus of the first optical system is fB and the effective diameter of the surface of the second lens group closest to the image side is φ2, the following conditional expression (4) is satisfied: 1.0<fB / φ2<3.0...(4) The optical characteristic measuring optical system according to any one of claims 2 to 5, which satisfies the following:

7. The optical characteristic measuring optical system according to any one of claims 1 to 6, An optical characteristic measuring device having a function of measuring the optical characteristics of the measurement object and a function of imaging the measurement object.

Images