Measurement optical system and photometric and colorimetric device

Abstract

The invention provides an optical system for measurement and a photometric and colorimetric device, which can introduce more light quantity and restrain enlargement. A measurement optical system (20) is provided with, in order from the object side: a first lens group (LG1) that includes at least one lens and has a positive refractive power; a second lens group (LG2) including at least one lens and having positive refractive power; a first aperture (S1); and a third lens group (LG3) including at least one lens and having positive refractive power. The optical system for measurement is further provided with a second aperture (S2) disposed in the vicinity of the position of the image-side focal point (f1) of the first lens group and / or in the vicinity of the position at which the second lens group and the third lens group are conjugated with the image-side focal point of the first lens group. The absolute value of the lateral magnification of the first aperture (S1) with respect to the first lens group and the second lens group is 0.7 or less.

Description

Technical Field

[0001] The present invention relates to a measurement optical system for guiding light from an object to be measured to a light receiving section, and a photometric and colorimetric device including the measurement optical system. Background Art

[0002] In recent years, the demand for high-contrast display devices such as organic EL (electro luminescence) displays has been increasing. In order to achieve high contrast, low-brightness performance must be improved, and for this purpose, a photometric and colorimetric device that can evaluate low-brightness performance is needed. In such a photometric and colorimetric device, a measurement optical system that can guide more light from the object to be measured to the light receiving unit is required.

[0003] For example, in the measurement optical system described in Patent Document 1, an aperture is arranged on a conjugate surface of the measured surface to define the measured area, and the angle of light rays obtained by arranging the incident surface of the light guide at the focal point of the entire optical system is defined. Thus, the amount of light that cannot enter the light guide due to the large incident angle of the off-axis light beam is reduced.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2018 / 230177 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] However, in the measurement optical system described in Patent Document 1, the size of the aperture is larger than that of the measured surface, which is in a conjugate relationship with the measured surface and the aperture. Therefore, when the measured area is to be expanded in order to ensure more light, the aperture needs to be expanded in the same proportion. As a result, the measurement optical system and even the photometric and colorimetric device as a whole are enlarged.

[0009] An object of the present invention is to obtain a larger amount of light while suppressing an increase in size.

[0010] Technical solutions for solving technical problems

[0011] In order to achieve the above object, the measuring optical system of the present invention comprises, in order from the object side:

[0012] A first lens group includes at least one lens and has positive refractive power;

[0013] a second lens group including at least one lens and having positive refractive power;

[0014] First aperture;

[0015] a third lens group including at least one lens and having positive refractive power;

[0016] The lens further comprises a second aperture, the second aperture being arranged near the image side focus of the first lens group and near at least one of a position conjugate with the image side focus of the first lens group with respect to the second lens group and the third lens group.

[0017] An absolute value of a lateral magnification of the first aperture with respect to a surface of the first lens group and the second lens group that is conjugate with the first aperture is 0.7 or less.

[0018] Effects of the Invention

[0019] According to the present invention, it is possible to capture a greater amount of light while suppressing an increase in size. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is a block diagram showing the configuration of a photometric and colorimetric device according to an embodiment.

[0021] Figure 2 It is a diagram showing the configuration of the measuring optical system according to the first embodiment.

[0022] Figure 3 This is a diagram for explaining the angle at which light from the first aperture in the first embodiment is incident on the second aperture via the third lens group.

[0023] Figure 4 This is a table showing the focal lengths of the respective lens groups in the lens units according to the first embodiment to the third embodiment.

[0024] Figure 5 This is a table showing the intervals on the optical axis when each lens group in the lens unit of the first embodiment to the third embodiment is a thin-walled lens.

[0025] Figure 6 It is a diagram showing the configuration of a measuring optical system according to a second embodiment.

[0026] Figure 7 It is a diagram showing the configuration of a measuring optical system according to a third embodiment.

[0027] Figure 8 It is a diagram showing the configuration of a measuring optical system according to a fourth embodiment.

[0028] Fig. 9 It is a diagram showing the configuration of a measuring optical system according to a fifth embodiment.

[0029] Description of Reference Numerals

[0030] 100: light and color measuring device;

[0031] 11: light receiving part;

[0032] 11a, 11b, 11c: X filter, Y filter, Z filter (color filter);

[0033] 11d, 11e, 11f: light receiving element for X filter, light receiving element for Y filter, light receiving element for Z filter (light receiving element);

[0034] 12: Control department;

[0035] 20, 20B, 20C, 20D, 20E: optical system for measurement;

[0036] 21, 21B, 21C, 21D, 21E: lens unit;

[0037] 22: light guide component;

[0038] 25d: ND filter;

[0039] CF: infrared cut filter;

[0040] f1: focus (image-side focus of the first lens group);

[0041] LG1, LG1b, LG1c: first lens group;

[0042] LG2, LG2b, LG2c: second lens group;

[0043] LG3, LG3b, LG3c: the third lens group;

[0044] S1: first aperture;

[0045] S2: second aperture;

[0046] OB: object to be measured;

[0047] SM: measured surface;

[0048] Ax: optical axis. DETAILED DESCRIPTION

[0049] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0050] <First embodiment>

[0051] [Overall structure of the photometric and colorimetric device]

[0052] Figure 1 : is a block diagram showing the structure of the photometric and colorimetric device 100 according to the present embodiment.

[0053] As shown in the figure, the photometry and colorimetry device 100 includes a measurement optical system 20 , a light receiving unit 11 , a control unit 12 , an input unit 13 , and a display unit 14 .

[0054] The measuring optical system 20 receives light from the object to be measured OB, and guides the received light to the light receiving unit 11. The object to be measured OB is a light emitting body in the present embodiment.

[0055] The details of the structure of the measuring optical system 20 will be described later.

[0056] The light receiving unit 11 receives light from the object OB guided by the measurement optical system 20, performs photoelectric conversion on the received light, and outputs an electrical signal corresponding to the light intensity. The light receiving unit 11 includes, for example, a spectrometer that splits the light from the object OB and a photoelectric conversion element that performs photoelectric conversion on the light split by the spectrometer.

[0057] Specifically, the light receiving unit 11 of the present embodiment has a structure for measuring the color and brightness of the object OB to be measured based on the tristimulus values ​​of XYZ. More specifically, the light receiving unit 11 has: three X filters 11a, Y filters 11b, and Z filters 11c corresponding to the color equalization functions X, Y, and Z specified by CIE (International Commission on Illumination), respectively; and X filter light receiving elements 11d, Y filter light receiving elements 11e, and Z filter light receiving elements 11f for receiving the light filtered by these filters and performing photoelectric conversion. The X filter 11a, the Y filter 11b, and the Z filter 11c are equivalent to an example of the color filter of the present invention.

[0058] In such a light receiving unit 11, light from the object OB is filtered by the X filter 11a, and the X filter light receiving element 11d performs photoelectric conversion, and outputs an electric signal (X signal) corresponding to the light intensity. Similarly, an electric signal (Y signal) is output through the Y filter 11b and the Y filter light receiving element 11e, and an electric signal (Z signal) is output through the Z filter 11c and the Z filter light receiving element 11f. These X signal, Y signal, and Z signal are output to the control unit 12.

[0059] The input unit 13 is an input means for an operator to perform various inputs for operating the photometric and colorimetric device 100. The input unit 13 includes, for example, various buttons and input devices, and outputs input signals corresponding to the contents of these operations to the control unit 12.

[0060] The display unit 14 is, for example, a liquid crystal display, an organic electroluminescent display, or other display. The display unit 14 displays various information such as the color and brightness of the object OB measured based on the display signal input from the control unit 12. It should be noted that the display unit 14 may be a touch panel that also serves as a part of the input unit 13, or may include a speaker capable of playing (outputting) sound.

[0061] The control unit 12 is composed of, for example, a CPU (Central Processing Unit), and controls the operation of each part of the photometric and colorimetric device 100. For example, the control unit 12 measures the light from the object OB using the measurement optical system 20 and the light receiving unit 11 based on the operation command input from the input unit 13. Then, the control unit 12 obtains the color and brightness of the object OB based on the electrical signal output from the light receiving unit 11.

[0062] [Structure of the measurement optical system]

[0063] Figure 2 It is a diagram showing the structure of the measuring optical system 20 according to the first embodiment.

[0064] As shown in the figure, the measuring optical system 20 includes a lens unit 21 and a light guide member 22 .

[0065] The light-guiding component 22 guides the light incident from the lens unit 21 to the light-receiving portion 11. More specifically, the incident surface of the light-guiding component 22 is arranged near the second aperture S2 of the lens unit 21 to be described later, and guides the light incident on the second aperture S2. The light-guiding component 22 of the present embodiment is a beam splitter that splits the incident light in order to guide the light to the three filters of the light-receiving portion 11. Specifically, the light-guiding component 22 is a bundle of fibers that divides a plurality of bundled bare optical fibers into three bundles midway, so that the incident light incident from one incident surface is emitted from three exit surfaces. However, the light-guiding component 22 is not limited to an optical fiber bundle, and may be, for example, a light guide or the like.

[0066] The lens unit 21 allows light from the object OB to enter the light guide member 22. Specifically, the lens unit 21 includes a first lens group LG1, a second lens group LG2, a first aperture S1, a third lens group LG3, and a second aperture S2 in order from the object side (the object OB side).

[0067] The first lens group LG1 includes at least one lens having positive refractive power (optical power). The first lens group LG1 of this embodiment includes a convex first lens L1. The first lens group LG1 converges light (light beam) introduced from the measured surface SM near the focus f1 of the first lens group LG1.

[0068] The second lens group LG2 includes at least one lens having positive refractive power. The second lens group LG2 of this embodiment has a convex lens second lens L2. The light beam converged at the focus f1 of the first lens group LG1 by the first lens group LG1 diffuses after passing through the focus f1. The second lens group LG2 converges the diffused light beam toward the first aperture S1. In other words, the first lens group LG1 and the second lens group LG2 form an image of the light image from the object OB to be measured as an intermediate image on the opening surface of the first aperture S1.

[0069] The third lens group LG3 includes at least one lens having positive refractive power. The third lens group LG3 of this embodiment includes a convex third lens L3 and a fourth lens L4. The third lens group LG3 makes the light beam converged by the second lens group LG2 and passing through the first aperture S1 converge toward the second aperture S2.

[0070] An infrared cut filter CF is arranged between the second lens group LG2 and the first aperture S1. In a photometric and colorimetric device that divides the optical path into a plurality of parts using the light guide member 22 as in the present embodiment, the light receiving unit 11 (light receiving element) also has sensitivity in the infrared wavelength region. Therefore, in a photometric and colorimetric device that processes only the visible light region, it is necessary to cut off infrared light before the light receiving unit 11 by the infrared cut filter CF. The position of the infrared cut filter CF is not particularly limited, but it is more preferable to arrange it in an area with a small beam diameter from the viewpoint of miniaturization.

[0071] The first aperture S1 is an optical component that specifies the measurement diameter, for example, a plate-shaped component having a circular opening corresponding to the measurement diameter. The first aperture S1 is arranged near the focus on the object side of the third lens group LG3 (hereinafter, there is a case where this arrangement is referred to as an "ideal arrangement"). Here, "arranged near the focus" ideally means arranged at the focus in paraxial optics, but in a real optical system, it means arranged at the optimal position near the focus according to the residual aberration.

[0072] The second aperture S2 is arranged near a position conjugated with the focus f1 on the image side (light guide component 22 side) of the first lens group LG1 relative to the second lens group LG2 and the third lens group LG3. That is, the second aperture S2 is arranged near the second focus of the entire measuring optical system 20 (lens unit 21). The first focus of the entire measuring optical system 20 is the focus f1 of the first lens group LG1. Here, being arranged "near" the focus is ideally to be arranged at the focus in paraxial optics, but in a real optical system it means being arranged at the best position near the focus according to the residual aberration. The second aperture S2 can be a plate-shaped component having an opening like the first aperture S1, and the incident surface (diameter) of the light guide component 22 can also serve as the second aperture S2.

[0073] In the measurement optical system 20 thus constructed, first, the first lens group LG1 converges the light (light beam) introduced from the measured surface SM near the focus f1 of the first lens group LG1. The light converged at the focus f1 by the first lens group LG1 diffuses after passing through the focus f1. The second lens group LG2 converges the diffused light toward the first aperture S1. The light that has passed through the first aperture S1 converges toward the second aperture S2 through the third lens group LG3.

[0074] At this time, since the first aperture S1 and the measured surface SM are in a conjugate relationship with each other, when there is uneven brightness on the measured surface SM, the same uneven light quantity is generated at each point on the opening surface of the first aperture S1. However, the third lens group LG3 guides the light beams emitted from each point of the first aperture S1 in a manner that spreads to the entire second aperture S2, thereby suppressing the influence of uneven brightness on the measured surface SM.

[0075] In addition, the first aperture S1 is arranged near the focal point on the object side of the third lens group LG3 (ideal arrangement). Therefore, the light emitted from each point of the first aperture S1 enters the second aperture S2 (light guide member 22) at the same angle. That is, the light emitted from the center of the first aperture S1 enters the second aperture S2 vertically. In addition, the light emitted from the outermost peripheral portion of the first aperture S1 enters the second aperture S2 at the largest angle relative to the axis perpendicular to the optical axis Ax.

[0076] Since the angle range of the light that can be introduced by the light guide member 22 is limited, this ideal arrangement is suitable in order to more effectively collect the light on the light guide member 22 .

[0077] Assume that in a non-ideal configuration, such as Figure 3 As shown in the figure, the incident angle of the light emitted from each point of the first aperture S1 is different depending on the position of the light entering the second aperture S2 (light guide member 22). Under the condition that the opening angle of the light beam entering the center of the second aperture S2 is the same, the light beam shown by the dotted line in the figure enters the second aperture S2 at a larger angle than the ideal configuration. When this angle is larger than the angle of the light beam introduced by the light guide member 22, the amount of light that can be introduced into the light guide member 22 is reduced compared to the ideal configuration.

[0078] In this regard, in the present embodiment, the first aperture S1 is arranged near the focal point on the object side of the third lens group LG3, so that it is possible to reduce the light loss caused by the large incident angle of the off-axis light beam.

[0079] In addition, in the lens unit 21, the absolute value of the lateral magnification of the first aperture S1 relative to the surface conjugate with the first aperture S1 is 0.7 or less with respect to the first lens group LG1 and the second lens group LG2. The lateral magnification is the lateral magnification of the first aperture S1 relative to the measured surface SM, that is, the ratio of the opening diameter of the first aperture S1 to the measured diameter of the measured surface SM. Among them, the absolute value of the lateral magnification is more preferably less than 0.65, and further preferably less than 0.61. In the lens unit 21 of the first embodiment, the absolute value of the lateral magnification is 0.40.

[0080] In the conventional optical system, the lateral magnification of the first aperture S1 relative to the measured surface SM is large. Therefore, when the measurement area of ​​the measured surface is expanded, the first aperture is increased in size accordingly. In this regard, in the present embodiment, by suppressing the lateral magnification of the first aperture S1 relative to the measured surface SM to be less than 0.7, it is possible to avoid increasing the size of the measurement optical system 20 (lens unit 21).

[0081] In addition, the lens unit 21 satisfies the following conditional expression.

[0082] F1G / F2G>1.1 ... (1)

[0083] Among them, F1G is the focal length of the first lens group LG1, and F2G is the focal length of the second lens group LG2.

[0084] In addition, it is preferable that the lens unit 21 satisfies the following conditional expression (1a).

[0085] F1G / F2G>1.2 ... (1a)

[0086] More preferably, the lens unit 21 satisfies the following conditional expression (1b).

[0087] F1G / F2G>1.3 ... (1b)

[0088] More preferably, the lens unit 21 satisfies the following conditional expression (1c).

[0089] F1G / F2G>1.4 ... (1c)

[0090] In the lens unit 21 of the first embodiment, F1G / F2G=2.52.

[0091] The above conditional expression (1) stipulates that the refractive power of the second lens group LG2 is greater than the refractive power of the first lens group LG1. By satisfying this conditional expression, the light obtained from the measured surface SM can be appropriately guided to the first aperture S1, which is a region that is conjugate with the measured surface SM and smaller than the measured surface SM. That is, the optical system 20 (lens unit 21) for measurement can be appropriately miniaturized.

[0092] In addition, the lens unit 21 satisfies the following conditional expression.

[0093] F2G / F3G>1.1 ... (2)

[0094] Among them, F2G is the focal length of the second lens group LG2, and F3G is the focal length of the third lens group LG3.

[0095] Furthermore, it is preferable that the lens unit 21 satisfies the following conditional expression (2a).

[0096] F2G / F3G>1.3 ... (2a)

[0097] More preferably, the lens unit 21 satisfies the following conditional expression (2b).

[0098] F2G / F3G>1.4 ... (2b)

[0099] More preferably, the lens unit 21 satisfies the following conditional expression (2c).

[0100] F2G / F3G>1.5 ... (2c)

[0101] In the lens unit 21 of the first embodiment, F2G / F3G=2.15.

[0102] The above conditional expression (2) stipulates that the refractive power of the third lens group LG3 is greater than the refractive power of the second lens group LG2. By satisfying this conditional expression, the light passing through the focus f1 of the first lens group LG1 can be appropriately guided to the second aperture S2, which is a region that is conjugate with the focus f1 and smaller than the focus f1 surface. That is, the measurement optical system 20 (lens unit 21) can be appropriately miniaturized.

[0103] The focal lengths of the lens groups in the lens unit 21 of the first embodiment and the intervals on the optical axis Ax when the lens groups are thin-walled lenses are shown in FIG. Figure 4 and Figure 5 .

[0104] [Technical Effects of the First Embodiment]

[0105] As described above, according to the present embodiment, the measurement area of ​​the measured surface SM is defined by the first aperture S1 in a conjugate relationship with the measured surface SM. In addition, the angle of the light introduced from the measured surface SM is defined by configuring the second aperture S2 at the focal position of the entire measurement optical system 20. Thus, the light loss caused by the large incident angle of the off-axis light beam can be reduced, and the focusing efficiency can be improved.

[0106] In addition, the absolute value of the lateral magnification of the first aperture S1 and the surface (measured surface SM) conjugated with the first aperture S1 with respect to the first lens group LG1 and the second lens group LG2 is 0.7 or less. Therefore, unlike the conventional method in which the absolute value of the lateral magnification is large, the enlargement of the first aperture S1 accompanying the expansion of the measurement area of ​​the measured surface SM can be avoided. Therefore, more light can be introduced and the enlargement can be suppressed.

[0107] Furthermore, according to the present embodiment, the measuring optical system 20 satisfies the above-mentioned conditional expression (1).

[0108] Thus, light acquired from the measurement surface SM can be appropriately guided to the first aperture S1 which is a region conjugate with the measurement surface SM and smaller than the measurement surface SM. That is, the measurement optical system 20 (lens unit 21 ) can be appropriately miniaturized.

[0109] Furthermore, according to the present embodiment, the measuring optical system 20 satisfies the above-mentioned conditional expression (2).

[0110] Thus, light passing through the focus f1 of the first lens group LG1 can be appropriately guided to the second aperture S2 which is a region conjugate with the focus f1 and smaller than the focus f1. That is, the measuring optical system 20 (lens unit 21) can be appropriately miniaturized.

[0111] In addition, according to the present embodiment, the first aperture S1 is arranged near the focal point on the object side of the third lens group LG3.

[0112] This can reduce the light loss caused by the large incident angle of the off-axis light beam.

[0113] <Second embodiment>

[0114] Figure 6 It is a diagram showing the configuration of a measuring optical system 20B according to the second embodiment.

[0115] As shown in the figure, the measuring optical system 20B of the second embodiment is different from the measuring optical system 20 of the first embodiment in the configurations of the first lens group, the second lens group, and the third lens group.

[0116] In the following description of each embodiment, points different from the configuration of the measuring optical system 20 of the first embodiment will be mainly described, and description of points that are the same in configuration will be omitted.

[0117] Specifically, the lens unit 21B of the measuring optical system 20B includes, in order from the object side (the side of the object OB to be measured), a first lens group LG1b, a second lens group LG2b, a first aperture S1, a third lens group LG3b, and a second aperture S2.

[0118] The first lens group LG1b includes a first lens L1 and a second lens L2 which are convex lenses.

[0119] The second lens group LG2b has a third lens L3 which is a convex lens.

[0120] The third lens group LG3b includes a fourth lens L4 and a fifth lens L5, a sixth lens L6 and a seventh lens L7 which are convex lenses. The fourth lens L4 and the fifth lens L5 are cemented to each other.

[0121] The infrared cut filter CF is arranged on the object side of the second lens group LG2b.

[0122] It should be noted that the arrangement of the first aperture S1 and the second aperture S2 on the optical axis Ax is the same as that in the first embodiment.

[0123] In the lens unit 21B, the absolute value of the lateral magnification of the first aperture S1 and the surface conjugate with the first aperture S1 with respect to the first lens group LG1b and the second lens group LG2b is 0.61.

[0124] The focal lengths of the lens groups in the lens unit 21B of the second embodiment and the intervals on the optical axis Ax when the lens groups are thin-walled lenses are as follows: Figure 4 and Figure 5 shown.

[0125] According to the second embodiment described above, the same effects as those of the first embodiment described above can be obtained.

[0126] <Third embodiment>

[0127] Figure 7 It is a diagram showing the configuration of a measuring optical system 20C according to the third embodiment.

[0128] As shown in the figure, a measuring optical system 20C according to the third embodiment is different from the measuring optical system 20 according to the first embodiment in the configurations of the first lens group, the second lens group, and the third lens group.

[0129] Specifically, the lens unit 21C of the measuring optical system 20C includes, in order from the object side (the side of the object OB to be measured), a first lens group LG1c, a second lens group LG2c, a first aperture S1, a third lens group LG3c, and a second aperture S2.

[0130] The first lens group LG1c includes a first lens L1 which is a convex lens.

[0131] The second lens group LG2c has a second lens L2 which is a convex lens.

[0132] The third lens group LG3c includes a third lens L3 which is a convex lens.

[0133] It should be noted that the arrangement of the first aperture S1 and the second aperture S2 on the optical axis Ax is the same as that in the first embodiment.

[0134] In the lens unit 21C, the absolute value of the lateral magnification of the first aperture S1 and the surface conjugate with the first aperture S1 with respect to the first lens group LG1c and the second lens group LG2c is 0.44.

[0135] In addition, the basic structure of the lens unit 21C is the same as that of the first and second embodiments, but each convex lens of the second lens group LG2c and the third lens group LG3c adopts an aspherical lens. Thus, a structure with a minimum number of lenses in which only one convex lens is configured in each lens group is realized. If the number of lenses increases, the light loss caused by reflection at the interface between the lens and the air increases, so the light loss can be suppressed by reducing the number of lenses.

[0136] The focal lengths of the lens groups in the lens unit 21C of the third embodiment and the intervals on the optical axis Ax when the lens groups are thin-walled lenses are as follows: Figure 4 and Figure 5 shown.

[0137] According to the third embodiment described above, the same effects as those of the first embodiment described above can be obtained.

[0138] In addition, by adopting aspherical lenses for the second lens group LG2c and the third lens group LG3c, the number of lenses can be reduced. Furthermore, the light loss caused by reflection at the interface between the lens and the air can be suppressed.

[0139] <Fourth embodiment>

[0140] Figure 8 It is a diagram showing the configuration of a measuring optical system 20D according to a fourth embodiment.

[0141] like Figure 8 As shown in FIG. 1 , the measuring optical system 20D according to the fourth embodiment is different from the measuring optical system 20 according to the first embodiment in that it includes an ND filter (Neutral Density Filter) 25 d .

[0142] In the lens unit 21D of the measuring optical system 20D, an ND filter 25d is arranged between the third lens group LG3 and the second aperture S2. The ND filter 25d is supported in a pluggable manner. In addition, the position of the ND filter 25d is not particularly limited, but it is more preferable from the perspective of miniaturization if it is arranged in an area with a small beam diameter.

[0143] According to the fourth embodiment described above, the same effects as those of the first embodiment described above can be obtained.

[0144] Furthermore, by providing the ND filter 25d, a higher brightness region can be appropriately measured.

[0145] That is, the optical system (lens unit) for measurement of the present embodiment can introduce more light, and is therefore suitable as a photometric and colorimetric device for low brightness areas. However, in high brightness areas, the amount of light that can be introduced by the light receiving element exceeds the allowable value. Therefore, by inserting the ND filter 25d, it is possible to perform photometric and colorimetric measurement in a higher brightness area without changing the spectral distribution of the introduced light beam. Furthermore, by configuring the ND filter 25d to be pluggable, the measurement range can be expanded compared to the past.

[0146] In addition, it is obvious that the ND filter 25d can be arranged in the same manner also in the above-mentioned second embodiment or third embodiment.

[0147] <Fifth embodiment>

[0148] Fig. 9 It is a diagram showing the configuration of a measuring optical system 20E according to a fifth embodiment.

[0149] As shown in the figure, the position of the second aperture S2 of the measuring optical system 20E according to the fifth embodiment is different from that of the measuring optical system 20 according to the first embodiment.

[0150] Specifically, in the lens unit 21E of the measuring optical system 20E, the second aperture S2 is arranged near the focal point f1 of the first lens group LG1. The second aperture S2 in this case is a plate-shaped member having a circular opening.

[0151] According to the fifth embodiment described above, the same effects as those of the first embodiment described above can be obtained.

[0152] That is, according to this embodiment, the second aperture S2 is arranged near the focus f1 on the image side of the first lens group LG1. That is, relative to the position of the second aperture S2 in the first embodiment, it is arranged near a position that is in a conjugate relationship with the second lens group LG2 and the third lens group LG3. Therefore, by such a second aperture S2, the angle of the light introduced from the measured surface SM can be specified.

[0153] It should be noted that, in the second embodiment or the third embodiment, the second aperture S2 can obviously be moved in the same manner. In addition, the second aperture S2 can be arranged both near the focus f1 on the image side of the first lens group LG1 and near a position conjugate with the focus f1.

[0154] [other]

[0155] As mentioned above, although one embodiment of the present invention has been described, the embodiment to which the present invention can be applied is not limited to the above-described embodiment, and can be appropriately modified within the scope not departing from the gist of the present invention.

Claims

1. An optical system for measurement, characterized in that: From the object side, it has: A first lens group includes at least one lens and has positive refractive power; a second lens group including at least one lens and having positive refractive power; First aperture; a third lens group including at least one lens and having positive refractive power; The lens further comprises a second aperture, the second aperture being arranged near the image side focus of the first lens group and near at least one of a position conjugate with the image side focus of the first lens group with respect to the second lens group and the third lens group. An absolute value of a lateral magnification of the first aperture with respect to a surface of the first lens group and the second lens group that is conjugate with the first aperture is 0.7 or less.

2. The measuring optical system according to claim 1, Satisfy the following conditions F1G / F2G>1.1 ... (1) in, F1G: focal length of the first lens group; F2G: Focal length of the second lens group.

3. The measuring optical system according to claim 1 or 2, Satisfy the following conditions F2G / F3G>1.1 ... (2) Among them, F2G: focal length of the second lens group; F3G: Focal length of the third lens group.

4. The measuring optical system according to claim 1, The first aperture is arranged near the focal point on the object side of the third lens group.

5. The measuring optical system according to claim 1, Equipped with infrared cut filter.

6. The measuring optical system according to claim 1, Equipped with ND filter.

7. The measuring optical system according to claim 1, A light guide member is provided, the light guide member being arranged at a position closer to the image side than the vicinity of a position where the second lens group and the third lens group are conjugate with the image side focal point of the first lens group, and guiding the light incident on the second aperture.

8. A light and color measuring device, characterized in that: have: The measuring optical system according to claim 1; a color filter for filtering the light guided by the measurement optical system; a light receiving element that performs photoelectric conversion on the light filtered by the color filter; A control unit is configured to obtain the color and brightness of the object to be measured based on the electrical signal output from the light receiving element.

Images