Photometric device, and converging lens unit

Abstract

To downsize a photometric device measuring a viewing angle characteristic.SOLUTION: A photometric device comprises: a converging lens unit in which incidence light is emitted from a location apart from an optical axis in proportion to an incidence angle; and an image sensor. The converging lens unit includes at least: a spherical lens that is located on an object side; and an aspherical lens that is located on an imaging side relative to the spherical lens. When an optical length from a measured object to a light reception surface of the image sensor is L and an optical focal length of the converging lens unit is f, the converging lens unit satisfies a condition of L / f<10.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a photometric device and a condenser lens unit, and more particularly to a photometric device and a condenser lens unit used in a spectroscopic measurement device and a viewing angle characteristic measurement device. [Background technology]

[0002] Conventionally, photometric devices that measure the display characteristics of liquid crystal displays and the like have been known (Patent Document 1). If such photometric devices are equipped with a spectroscopic means, they can disperse the received light and measure it for each wavelength. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-207406 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, displays have become not only liquid crystal displays, but also self-emitting elements such as OLEDs and micro LEDs, and they are becoming finer, so there is a need to measure their viewing angle characteristics. In conventional photometric devices, the light receiving optical system only deflects the incident light into parallel light, and does not have the function to measure the viewing angle characteristics. For example, if you want to measure the viewing angle characteristics using a conventional photometric device, you need to scan the photometric device itself in the angular direction and measure the light for each angle.

[0005] Therefore, at least one of the objectives of the present disclosure is to measure the viewing angle characteristics using a photometric device.

[0006] Also, at least one of the objectives of the present disclosure is to reduce the size of the photometric device.

[0007] In addition, problems that are obvious to a person skilled in the art and can be read from the embodiments and explanations characteristic of the present disclosure described in the specification, drawings, etc. of the present disclosure may also become problems that the divided invention must solve if a divisional application based on the present disclosure is filed. [Means for solving the problem]

[0008] In order to achieve at least one of the above-mentioned objects, the photometric device disclosed herein comprises a focusing lens unit in which incident light is emitted from a position away from the optical axis in proportion to the angle of incidence, and an image sensor, wherein the focusing lens unit includes at least a spherical lens located on the object side and an aspherical lens located on the image side of the spherical lens, and satisfies the condition L / f<10, where L is the optical length from the object to be measured to the light receiving surface of the image sensor and f is the optical focal length of the focusing lens unit. Effect of the Invention

[0009] According to the present disclosure, the viewing angle characteristics can be measured using a photometric device. [Brief description of the drawings]

[0010] [Figure 1] 1 is an overall configuration diagram showing a photometry device according to an embodiment. [Diagram 2] FIG. 3 is a ray tracing diagram of the condenser lens unit according to the first embodiment. [Diagram 3] FIG. 1 is a diagram showing a measurement image of the angular distribution of spectral radiance. [Figure 4] FIG. 11 is a ray tracing diagram of the condenser lens unit according to the second embodiment. [Diagram 5] FIG. 11 is a ray tracing diagram of the condenser lens unit according to the third embodiment. [Figure 6] FIG. 11 is a ray tracing diagram of the condenser lens unit according to the fourth embodiment. [Figure 7] FIG. 13 is a table summarizing each embodiment. [Figure 8] FIG. 11 is a ray tracing diagram of a relay lens unit according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present disclosure will be described with reference to the drawings.

[0012] 1 is an overall configuration diagram showing a photometric device according to an embodiment of the present disclosure. The photometric device may be, for example, a spectroscopic measurement device having a function of performing spectroscopic measurement. The photometric device may also have a function of colorimetric measurement. The photometric device 1 includes at least a basic optical system 10, a spectroscopic unit 20, an image sensor 30, and a housing 50 that houses them.

[0013] The photometric device 1 has the functions of, for example, a spectroradiometer and a spectroscopic camera, and light incident from the basic optical system 10 is dispersed into multiple wavelengths by the spectroscopic section 20 and images are formed on the light receiving surface of the image sensor 30, thereby making it possible to obtain images for each of the multiple wavelengths.

[0014] Although not shown, the basic optical system 10 has a lens group in which a plurality of lenses are arranged along an optical axis, and has the function of deflecting the received light and finally guiding it to the light receiving surface of the image sensor 30.

[0015] The spectroscopic unit 20 has a function of splitting the light guided by the basic optical system 10 into a plurality of wavelengths. The spectroscopic unit 20 is, for example, a transmission wavelength changing filter, a grating element, a prism, etc. The spectroscopic unit 20 can select wavelengths in 1 nm increments to acquire an image.

[0016] The image sensor 30 is an element in which a plurality of pixels are arranged two-dimensionally, such as a CMOS, a CCD, etc. The wavelength to which the image sensor 30 is sensitive may be, for example, 380 to 780 nm in the visible light range for humans, or may be other wavelengths such as infrared or ultraviolet ranges.

[0017] The housing 50 is provided with a mount 51 for separately adding an optional lens such as a wide-angle lens. The mount 51 is, for example, a C-mount type mount, and has a predetermined diameter and a predetermined screw shape, making it compatible with various interchangeable lenses. This allows the condenser lens unit 60 to be added as an additional objective lens, that is, as an option.

[0018] Using such a mount 51, a condenser lens unit 60 is attached to the photometric device 1. The optical axis of the condenser lens unit 60 is aligned with the optical axis X of the basic optical system 10.

[0019] The condenser lens unit 60 is an optical system including at least a spherical lens 61 and an aspherical lens 62, and is a Fourier transform lens unit that performs an optical Fourier transform.

[0020] Such a photometric device 1 can be connected to a computer such as a PC (not shown), store measured data, and process images using dedicated software installed on the PC to generate measurement results and data such as images representing the measurement results. For example, data showing the measurement results of the viewing angle characteristics described later can be generated.

[0021] The condenser lens unit 60 of the present disclosure will be described with reference to Fig. 2. Fig. 2 is a cross-sectional view of the condenser lens unit cut along the optical axis, and is also a ray tracing diagram that shows a schematic diagram of how light emitted from light sources that are multiple objects to be measured and present on an object plane OP is guided.

[0022] In FIG. 2, the focusing lens unit 60 is configured such that a spherical lens 61 (first lens group), an aspherical lens 62 (second lens group), and an optical filter 63 are arranged along the optical axis X from the object plane OP to the image plane IP, and light travels from the left side to the right side of the drawing.

[0023] The roles of the spherical lens 61 and the aspherical lens 62 are integrated, but if pressed, the spherical lens 61 has as high a refractive index as possible to collect light from a wide angle, while the aspherical lens 62 plays a role similar to that of a field lens that adjusts the image.

[0024] Moreover, the spherical lens 61 and the aspherical lens 62 can also be regarded as a first lens group and a second lens group, respectively, and each may be composed of a plurality of lenses.

[0025] The spherical lens 61 is a lens having at least one surface that is spherical and the other surface that is flat or spherical, and does not have an aspheric surface. For example, the lens may be a bi-spherical lens, or a so-called plano-convex lens having a spherical surface on one side and a flat surface on the other side.

[0026] The aspherical lens 62 is a lens in which at least one surface is an aspherical surface and does not have a spherical surface. The meaning of aspherical is technically interpreted as broadly as possible, and refers to a surface that is different from a spherical surface, i.e., a simple surface represented by a certain curvature, and is adjusted to have a specific mathematical shape or a shape that can exhibit a specified optical performance in order for a designer to optimize the convergence of light according to the purpose. Typical examples include aspherical lenses, toric lenses, Fresnel lenses, parabolic lenses, hyperbolic lenses, etc.

[0027] The optical filter 63 may be any of various filters for realizing predetermined optical characteristics, such as a wavelength selection filter or an ND filter, and the condenser lens unit 60 does not necessarily have to include the optical filter 63.

[0028] The optical Fourier transform by the condenser lens unit 60 will be described. The condenser lens unit 60 is, for example, an fθ lens (the "equidistant projection lens" of the present invention), and has the property that the focal length of the outgoing light is constant regardless of the angle of the incident light. On the other hand, the focal position of the outgoing light that has passed through the lens is proportional to the angle of the incident light. This relationship is expressed as f(θ)=f·θ, where f is the focal length, θ is the angle of the incident light to the lens, and f(θ) is the focal position of the light that has passed through the lens (the displacement in the Y direction from the optical axis X). Such an fθ lens is an imaging lens of the equidistant projection type. In more detail, f is the so-called optical focal length, which is the focal length of the entire condenser lens unit 60, not the focal length of each individual lens.

[0029] This converts the spatial frequency components of the input light into positions on the output surface of the lens in the plane corresponding to the focal length (IP in this figure). In other words, the fθ lens is also a Fourier transform lens.

[0030] For example, the output position of the light beam group RB1 having a large incident angle to the condenser lens unit 60 is farther away from the optical axis X than the output position of the light beam group RB2 having a small incident angle to the condenser lens unit 60. This makes it possible to measure the angular distribution of the spectral radiance of the measurement target.

[0031] 3 is a diagram showing a measurement image of the angular distribution of spectral radiance. The light whose incident angle has been converted to the output position by the condenser lens unit 60 is guided by the basic optical system 10 while basically maintaining its in-plane distribution, is dispersed by the spectroscopic section 20, and reaches the light receiving surface of the image sensor 30. Then, the angular distribution of the spectral radiance is generated based on the image received by the image sensor 30. In the photometric device (spectroscopic measurement device) of the present disclosure, such a distribution diagram can be generated for each wavelength.

[0032] Moreover, this measurement can be performed in one shot from a fixed point without changing the angle of the measurement device relative to the measurement target in order to measure the viewing angle.

[0033] The object or measurement subject for measuring the angular distribution of such spectral radiance is, for example, a light-emitting device in a broad sense, such as a self-luminous element such as an OLED (organic light-emitting element) or a micro LED, or a liquid crystal element having a light source as a backlight, or a display that uses these elements or devices as pixels.

[0034] The inspection needs for these light-emitting elements and displays have been mentioned above, but we will now go into more detail. In recent years, the resolution of displays has improved dramatically, and the elements that make up displays have also become smaller. It is desirable to measure the viewing angle characteristics of these elements using spectroscopic measuring devices such as spectroradiometers and spectroscopic cameras.

[0035] Furthermore, displays are not limited to flat displays, but include curved displays, foldable displays, etc. In order to evaluate such displays of various shapes, it is also desirable to reduce the size of the device.

[0036] According to the above-described condenser lens unit 60 of the present disclosure, it is possible to make the optical system compact and reduce its diameter. In order to make the optical system compact, it is preferable that the ratio of the optical length L to the optical focal length f: L / f<10. It is even more preferable that L / f<4.

[0037] Explaining this with reference to Fig. 2, the optical length L is the distance from the measurement target to the image plane IP. In this figure, the position of the measurement target is the object plane OP. When the image sensor 30 is directly disposed on the image plane IP, the optical length L is understood as shown in the relationship in this figure, but when the basic optical system 10 described above or the relay lens unit 70 described later is interposed, the optical length L is formally extended, but in reality, the light receiving surface of the basic optical system 10 or the relay lens unit 70 described later corresponds to the image plane IP.

[0038] Moreover, the optical focal length f is the distance from the exit surface to the image surface IP of the condenser lens unit 60. When the position of the exit surface changes in the radial direction, the center position in the radial direction is used as the starting point.

[0039] Furthermore, in inspection applications for self-luminous elements such as the above-mentioned OLEDs (organic electroluminescence elements) and micro LEDs, the maximum lens diameter of the above-mentioned condenser lens unit 60 is preferably 100 mm or less from the viewpoint of miniaturization of the measuring device.

[0040] Examples according to the embodiments of the present disclosure will be described below. Example 1 In FIG. 2, the spherical lens 61 of the condenser lens unit 60 has a refractive index n of 1.8829 and a dispersion νd of 40.76, while the aspherical lens 62 has a refractive index n of 1.7645 and a dispersion νd of 49.09, with an optical length L of 12.683 mm and an optical focal length f of 5.226. The spherical lens 61 has a concave surface on the light receiving side and a convex surface on the light projecting side, while the aspherical lens 62 has a flat surface on the light receiving side and an aspherical surface on the light projecting side. The optical filter 63 has a flat plate shape, and no refraction occurs other than that due to the material. This allows the measurement of a viewing angle characteristic of ±60 degrees. In addition, the ratio of the optical length L to the optical focal length f is L / f=2.427, making the optical system compact.

[0041] Here, the size constraints in the area direction of the image sensor 30 when the condenser lens unit 60 is attached to a photometric device using a C mount will also be described. Since the C mount has a diameter of 1 inch (=25.4 mm), the maximum outer diameter of the condenser lens unit 60 is also at least 25.4 mm or less. In that case, the area of ​​the light receiving surface of the image sensor 30 is also within the range of a 1 inch diameter. Such constraints on the application of the C mount may be applied to embodiments other than Example 1.

[0042] Example 2 FIG. 4 is a ray tracing diagram in a cross section of the focusing lens unit according to the second embodiment cut along the optical axis. In FIG. 4, the spherical lens 61 of the focusing lens unit 60 has a refractive index n of 1.8829 and a dispersion νd of 40.76, and the aspherical lens 62 has a refractive index n of 1.7645 and a dispersion νd of 49.09, and uses the same high refractive index glass material as in the first embodiment. On the other hand, the lens shapes and dimensions are different, the spherical lens 61 has a flat surface on the light receiving side and a spherical surface on the light projecting side, and the aspherical lens 62 has a convex shape on both sides, and each has an aspherical surface with a different shape, an optical length L of 9.284 mm, and an optical focal length f of 3.278. This allows the measurement of a viewing angle characteristic of ±80 degrees. In addition, the ratio of the optical length L to the optical focal length f: L / f=2.833, and the optical system is made compact.

[0043] Example 3 Fig. 5 is a ray tracing diagram in a cross section of the focusing lens unit according to the third embodiment cut along the optical axis. In Fig. 5, the spherical lens 61 of the focusing lens unit 60 has a refractive index n of 1.7645 and a dispersion vd of 49.09, and the aspherical lenses 62A and 62B have a refractive index n of 1.7645 and a dispersion vd of 49.09. The spherical lens 61 and the aspherical lenses 62A and 62B are made of the same high refractive index glass material, and the aspherical lens is composed of two lens groups. The spherical lens 61 has a flat surface on the light receiving side and a spherical surface on the light projecting side, the aspherical lens 62A has aspherical surfaces with different shapes, both of which are convex, and the aspherical lens 62B has aspherical surfaces with different shapes, with a concave surface on the light receiving side and a convex surface on the light projecting side. The optical length L is 13.593 mm, and the optical focal length f is 6.248. This makes it possible to measure a viewing angle characteristic of ±70 degrees. In addition, the ratio of the optical length L to the optical focal length f is L / f=2.176, making the optical system compact.

[0044] Example 4 FIG. 6 is a ray tracing diagram in a cross section of the focusing lens unit according to the fourth embodiment cut along the optical axis. In FIG. 6, the spherical lens 61 of the focusing lens unit 60 has a refractive index n of 1.8268 and a dispersion νd of 43.55, and the aspherical lens 62 has a refractive index n of 1.6309 and a dispersion νd of 61.10. The spherical lens 61 has a flat surface on the light receiving side and a convex surface on the light projecting side, while the aspherical lens 62 has a convex surface on the light receiving side and a concave surface on the light projecting side, each of which is an aspherical surface with a different shape. The optical length L is 20.731 mm, and the optical focal length f is 2.530. This allows the measurement of a viewing angle characteristic of ±80 degrees. In addition, the ratio of the optical length L to the optical focal length f: L / f=8.195, which makes the optical system compact.

[0045] Fig. 7 is a table summarizing Examples 1 to 4. All of Examples 1 to 4 satisfy the requirement of the ratio of optical length L to optical focal length f: L / f<10, and the optical system is compact. Furthermore, in Examples 1 to 3, L / f<4, and the optical system is even more compact.

[0046] Here, the amount of displacement in the Y direction due to the Fourier transform of the incident light is expressed as f(θ)=f·θ, as described above. When the viewing angle of the measurement target is, for example, ±θ, the light with the maximum incident angle is +θ and -θ, and the amount of displacement of the light from the + side and - side at the maximum incident angle is f·θ, respectively. Then, the opening of the focal position after passing through the focusing lens unit 60 is 2×f·θ with the optical axis X as the center. In this sense, when measuring light with the maximum viewing angle ±θ, the effective outer diameter of the focusing lens unit 60 needs to be at least 2×f·θ or more.

[0047] 2 × f·θ in each embodiment varies depending on the viewing angle of the light being measured, and when calculated, gives the values ​​shown in Table 1. Looking at these values, all fall within the range of 2 × f·θ<25.4 (mm), and the dimensions have been miniaturized to a level that allows for installation using a C mount.

[0048] This concludes the description of the embodiments of the present disclosure, but the scope of application of the present disclosure is not limited to the examples described above, and for example, the following modified examples may also be used.

[0049] (Modification) Fig. 8 is a ray tracing diagram in a cross-sectional view of a relay lens unit 70 according to a modified example taken along the optical axis. In Fig. 8, a relay lens unit 70 composed of a plurality of lenses is disposed behind the condenser lens unit 60. In the photometric device of the present disclosure, an optical system acting as a relay, such as the relay lens unit 70, may be inserted between the condenser lens unit 60 and the image sensor 30 in this manner.

[0050] In addition, in the present disclosure, it is possible to implement a combination of the above-described embodiments and examples. For example, in the above-described embodiment, the spectroscopic measurement of the photometric device 1 is mainly described, but the photometric device 1 may also have a colorimetric measurement function. By applying the photometric device 1 to a color luminance meter, it is possible to perform luminance measurement, chromaticity measurement, etc. [Explanation of symbols]

[0051] 1 Photometering device 10 Basic optical system 20 Spectroscopic section 30 Image Sensor 50 Case 51 Mounting section 60 Condenser lens unit 61 Spherical Lens 62 Aspheric Lenses 63 Optical Filters 70 Relay lens unit f optical focal length L Optical length OP object plane IP image plane RB1 ray group RB2 ray group X optical axis

Claims

1. 1. A photometric device comprising: a condenser lens unit that emits incident light from a position away from an optical axis in proportion to the angle of incidence; An image sensor, The condenser lens unit includes at least A spherical lens located on the object side; an aspheric lens located on the image side relative to the spherical lens, A photometric device that satisfies the condition L / f<10, where L is the optical length from the object to be measured to the light receiving surface of the image sensor and f is the optical focal length of the focusing lens unit.

2. the photometric device includes a spectroscopic unit between the condenser lens unit and the image sensor, 2. The photometric device according to claim 1, wherein the focusing lens unit is an equidistant projection f(θ) lens in which a focal position of the outgoing light that has passed through the spherical lens and the aspherical lens is proportional to the incident angle, and a focal length of the outgoing light is constant regardless of the angle of the incident light.

3. 3. The photometric device according to claim 1, wherein the relationship between the optical length L and the optical focal length f satisfies the condition L / f<4.

4. 3. The photometric device according to claim 1, further comprising a relay lens unit comprising a plurality of lenses disposed behind said condenser lens unit.

5. The object to be measured is a display using an OLED, a micro LED, or a liquid crystal having a light source as a backlight, the image sensor is sensitive to wavelengths in the human visible light range; The photometric device according to claim 2 , which measures the viewing angle characteristics of light emitted from the display.

6. 6. The photometric device according to claim 5, wherein the maximum lens diameter of the condenser lens unit is 100 mm or less.

7. A condenser lens unit that can be attached as an objective lens to a spectroscopic measurement device having an image sensor and a spectroscopic unit, At least a spherical lens located on the object side; an aspheric lens located on the image side of the spherical lens; an equidistant projection f(θ) lens in which the focal position of the outgoing light passing through the spherical lens and the aspherical lens is proportional to the angle of the incident light, and the focal length of the outgoing light is constant regardless of the angle of the incident light; A focusing lens unit configured to satisfy the condition L / f<10, where L is the optical length from the object to be measured to the light receiving surface of the image sensor and F is the optical focal length of the focusing lens unit.

8. When the maximum viewing angle of light emitted from the light source that is the object to be measured is ±θ, the condition 2×f·θ<25.4 (mm) is satisfied, The condenser lens unit according to claim 7 , wherein the condenser lens unit has mounting compatibility with a C-mount format.

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