JP2010002255A - Optical system for measurement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system for measurement capable of improving detection sensitivity using a filter for interference without extending the total length of the optical system. <P>SOLUTION: The optical system for measurement includes: a first lens 5 that faces a measurement target, has positive power, and condenses luminous flux from each point in a region to be measured of the measurement target as parallel luminous flux; an aperture diaphragm 6 that is arranged at a nearly rear focus position of the first lens 5 to regulate the incidence angle of luminous flux entering the first lens 5 from each point; a second lens 7 that has a front focus at the arrangement position of the aperture diaphragm 6 and forms an image of the region to be measured at a rear focus position based on luminous flux entering through the aperture diaphragm 6; a light guide 8 that has an incidence end face at the rear focus position of the second lens 7 and divides each luminous flux entering an incidence end face 8a into three luminous flux groups; and a light reception means for receiving each luminous flux group via an interference filter 11 arranged opposite to the emission surface of the light guide 8. An incidence angle at the position of the incidence end face 8a of the light guide 8 is set smaller than that at the position of the aperture diaphragm 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a measurement optical system used for measuring the characteristics of a color to be measured, and relates to a measurement optical suitable for a colorimeter that measures display characteristics (for example, chromaticity, luminance, color difference, etc.) of a color LCD. Regarding the system.

Conventionally, as a measurement optical system used in colorimeters that measure the display characteristics of color LCDs (for example, chromaticity, brightness, color difference, etc.), even when the light intensity is weak, the characteristics of the color to be measured are accurately measured. In order to achieve this, an objective lens having a positive power for condensing only a light beam having an emission angle of a predetermined value or less among light beams from the measurement target region to be measured is provided, and a plurality of light beams collected by the objective lens are collected. The optical fiber is made to enter an incident end face of a light guide formed by bundling a plurality of optical fibers, the light guide is divided into three parts, and each light beam is emitted from the exit end face of each of the divided light guides. Each of the emitted light beams is received by a light receiving element, and the characteristics of the color to be measured are measured based on the photoelectric conversion signal related to the tristimulus values (R, G, B) of light. (See Patent Document 1).
Japanese Patent Laid-Open No. 2002-318080

  Conventionally, in this measurement optical system, in order to obtain tristimulus values of light, spectral sensitivity correction filters having sensitivity in each wavelength region of R (red), B (blue), and G (green) It is arranged in front of the element. A color glass filter is usually used as the spectral sensitivity correction filter.

  However, since this type of colored glass filter has low transmittance, the amount of light received by the light receiving element is reduced, and when the light intensity is weak, the color characteristics are considerably difficult to measure and the detection sensitivity is improved. Thus, it is insufficient to accurately measure the characteristics of the color to be measured.

  Therefore, it is conceivable to use an interference filter having a high transmittance as the spectral sensitivity correction filter. However, if the incident angle of the light beam incident on this interference filter is large, the wavelength of light shifts to the shorter side. There is a problem that it is difficult to accurately measure color characteristics.

  In addition, if the focal length of the objective lens is set to be large, the incident angle at the light entrance end face position can be reduced, and the incident angle is stored and propagated to the light guide exit end face for output and interference. Although the incident angle with respect to the filter can be reduced, such a configuration causes a problem that the entire length of the measurement optical system is increased.

  The present invention has been made in view of the above circumstances, and provides a measurement optical system capable of improving detection sensitivity using an interference filter without increasing the total length of the optical system. .

  The invention according to claim 1 is a first lens that confronts the measurement object and has a positive power and collects and collimates light beams from each point of the measurement target area of the measurement object, and the first lens An aperture stop that is disposed at a substantially rear focal position of the lens and restricts an incident angle of a light beam incident on the first lens from each of the points; a front focal point at the substantially disposed position of the aperture stop; and A second lens for forming an image of the measured region at a rear focal position based on a light beam incident through an aperture stop; and an incident end face at an approximate rear focal position of the second lens. A beam splitting unit that splits each beam incident on the beam into three beam groups, and a light receiving unit that receives each beam group through an interference filter disposed opposite to the exit surface of the beam splitting unit. The incident angle of the light beam at the incident end face position of the light beam splitting means is the Is set smaller than the incident angle at the mouth aperture position, the output from the light receiving means is a measuring optical system characterized in that it is used to measure the color characteristics.

  According to a second aspect of the present invention, in order to make the incident angle at the incident end face position of the light beam dividing means smaller than the incident angle at the aperture stop position, the size of the incident end face of the light beam dividing means is the aperture. 2. The measuring optical system according to claim 1, wherein the measuring optical system is set larger than the size of the stop.

  According to a third aspect of the present invention, the field stop for defining the size of the region to be measured is disposed on the incident end face of the light beam splitting means. It is a system.

  According to a fourth aspect of the present invention, the light beam splitting means includes a light guide member in which a large number of optical fibers are bundled, and the multiple optical fibers have a pseudo image forming positional relationship of the light beams formed on the incident end face. 4. The measuring optical system according to claim 3, wherein the measuring optical system is bundled so as to be random.

  According to a fifth aspect of the present invention, the light receiving means is disposed so as to face the emission end face and has a positive power for condensing the light beam emitted from the emission end face; The measurement optical system according to claim 4, further comprising a light receiving unit that receives light collected by the lens.

  According to the first to fourth aspects, the detection sensitivity can be improved using the interference filter without increasing the total length of the optical system.

  Further, according to the fifth aspect of the invention, in addition to the above effects, the light receiving sensitivity can be improved.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a color measuring optical system according to the present invention will be described below with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration of a colorimeter measurement optical system according to the present invention. In FIG. 1, reference numeral 1 denotes a liquid crystal panel, reference numeral 1a denotes a display surface of the liquid crystal panel 1, and 2 denotes It is an optical system for measurement. Here, the display surface 1a is an object to be measured, and a part of the display surface 1a is a measurement target area.

  The measuring optical system 2 is generally composed of a cylindrical body 3 and a housing 4. A first lens 5, an aperture stop 6, and a second lens 7 are provided inside the cylindrical body 3, and the housing 4 has other measurement circuits including, for example, a light guide 8, a light receiving unit 9, and an arithmetic circuit 10. A mechanism required for measurement such as a power supply circuit and a measurement switch is provided.

  The tip 3a of the cylindrical body 3 is in contact with the display surface 1a during measurement, and the first lens 5 is opposed to the display surface 1a during measurement. The cylindrical body 3 plays a role of shielding external light and a role of defining a distance of the display surface 1a from the first lens 5.

  The first lens 5 has a positive power and is disposed such that its front focal position f1 is located on the display surface 1a. The first lens 5 has a role of collecting and collimating the light flux from the region to be measured on the display surface 1a. In FIG. 1, reference characters Pa1 to Pa3 indicate light beams incident on the first lens 5 from the point a, reference characters Pb1 to Pb3 indicate light beams incident on the first lens 5 from the point b, and reference characters Pc1 to Pc3 indicate point c. The light beams from the points a, b, and c in the region to be measured are collected by the first lens 5, collimated, and guided to the aperture stop 6.

  The aperture stop 6 is disposed at the rear focal position f1 'of the first lens 5 and has a role of regulating the incident angle of the light beam incident on the first lens 5 from the points a, b, and c. Here, the aperture stop 6 plays a role of shielding a light beam traveling from the measurement region to the first lens 5 at an angle exceeding plus / minus 2.5 degrees with respect to the principal rays Pa2, Pb2, and Pc2.

  Here, the colorimeter is required to block the light beam from the measurement area toward the first lens 5 at an angle exceeding plus or minus 2.5 degrees with respect to the principal rays Pa2, Pb2, and Pc2. Is based on international standards.

  The second lens 7 has a front focal position f2 at the position where the aperture stop 6 is disposed, and plays a role of forming an image of the measurement region at the rear focal position f2 ′ based on the light beam incident through the aperture stop 6. The second lens also has a positive power like the first lens 5. The focal length of the second lens 7 is shorter than the focal length of the first lens 5.

  The light guide 8 is composed of a fiber bundle in which a large number of optical fibers are bundled. In this fiber bundle, the incident end face 8a side is bundled into one, and the exit end face side is divided into three fiber bundles. The exit end faces of the fiber bundles divided into the three fiber bundles are denoted by reference numerals 8br, 8bg, and 8bb, respectively. As shown in FIG. 2, the emission end faces 8br, 8bg, and 8bb are arranged so that, for example, line segments connecting the center positions O1, O2, and O3 form an equilateral triangle.

  The incident end face 8a of the light guide 8 is disposed at the rear focal position f2 'of the second lens 7, and the light guide 8 splits the image forming light flux incident on the incident end face 8a into three light flux groups. As a role.

  As schematically shown in FIG. 3, the multiple optical fibers are formed by being bundled so that the imaging position relationship of the image forming light beam formed on the incident end face 8a is pseudo-random. Since the image forming light beams emitted from the respective emission end faces 8br to 8bb and incident on each light receiving element to be described later are pseudo-randomly mixed and incident on the respective light receiving elements, unevenness in the amount of light of the image forming light beam is reduced. The

  The light receiving means 9 is roughly composed of interference filters 11a to 11c and light receiving elements 12a to 12c. The interference filters 11a to 11c are arranged to face the emission end faces 8br, 8bg, and 8bb, respectively. The light receiving elements 12a to 12c are arranged corresponding to the interference filters 11a to 11c.

  The interference filter 11a has a filter characteristic that transmits red (R) light out of the light flux emitted from the emission end face 8br, and the interference filter 11b emits green (G) light out of the light flux emitted from the emission end face 8bg. The interference filter 11c has a filter characteristic that transmits blue (B) light out of the light beam emitted from the emission end face 8bb.

  The light receiving element 12a outputs a photoelectric conversion signal based on the light in the red wavelength range transmitted through the interference filter 11a, and the light receiving element 12b outputs a photoelectric conversion signal based on the light in the green wavelength range transmitted through the interference filter 11b. The light receiving element 12c outputs a photoelectric conversion signal based on the light in the blue wavelength band transmitted through the interference filter 11c, and each photoelectric conversion signal is input to the arithmetic circuit 10 and other measurement circuits. Color characteristics such as brightness and color difference are measured.

  The entrance end face 8a of the light guide 8 is provided with a field stop 13 that defines the size of the region to be measured, so that extra light from the region to be measured is shielded. The size of the field stop 13, that is, the size of the incident end face 8 a of the light guide 8 is set to be larger than the size of the aperture stop 6, whereby the incident end face 8 a of the light guide 8 is set to the aperture stop 6. When the incident end surface 8a of the light guide 8 is disposed at the rear focal position f2 ′ of the second lens 7 with respect to the maximum incident angle α1 of each light beam incident on the incident end surface 8a. The maximum incident angle α2 of each light beam incident on the end face 8a can be moderated. As a result, even when the interference filters 11a to 11c having high transmittance are used, the light wavelength is prevented from shifting to the shorter side. Color characteristics can be measured accurately.

  Further, when the incident end face 8a is intentionally arranged at the position of the aperture stop 6, the maximum incident angle α1 of each image-forming light beam incident on the incident end face 8a is preserved and propagated to and emitted from the exit end faces 8br to 8bb. When the measurement optical system is configured using the interference filters 11a to 11c, it is necessary to increase the focal length of the first lens 5 in order to reduce the maximum incident angle α1, and the light is guided accordingly. Since the incident end face 8a of the body 8 becomes larger, the length of the light guide 8 is required, and the total length of the measurement optical system must be increased. In the embodiment of the present invention, the first lens 5 and the first The measurement optical system is configured by a telecentric optical system using the two lenses 7, and the maximum incident angle α2 of the image-forming light beam incident on the incident end face 8a via the second lens 7 is made gentler than the maximum incident angle α1. Configure Because, without increasing the total length of the measurement optical system can be made compact.

  Preferably, assuming that the area of the aperture stop 6 is S1 and the incident end face 8a of the light guide 8, that is, the area of the field stop 13 is S2, the product S1 · sinα1 of the sign of the maximum incident angle α1 of the aperture stop 6 and the area S1. The first lens 5 and the second lens 7 are disposed so that is equal to the product S2 · sin α2 of the sine of the maximum incident angle α2 and the area S2, and the first lens 5 and the second lens 7 are interposed. Therefore, it is desirable to arrange the incident end face 8a with respect to the second lens 7 so that the measurement region and the incident end face 8a are optically conjugate.

  As described above, in the embodiment of the present invention, the light receiving elements 12a to 12c are directly disposed opposite to the interference filters 11a to 11c. However, as shown in FIG. 4, the emission end faces 8br to 8bb and the interference filter 11a are arranged. To 11c, a condensing lens 14 having a positive power for condensing the light beams emitted from the emission end faces 8br to 8bb is disposed and transmitted through the interference filters 11a to 11c constituting a part of the light receiving unit. If the configuration is such that the light beam is converged on the light receiving elements 12a to 12c, the light receiving sensitivity can be further improved.

  According to the embodiment of the present invention, the detection sensitivity of weak light is improved, and there is an effect that the black measurement sensitivity of the measurement target area can be improved.

It is explanatory drawing which shows typically the optical system for a measurement of this invention. It is a top view which shows the positional relationship of the output end surface shown in FIG. It is a perspective view which shows typically an example of the optical fiber bundle concerning this invention. It is explanatory drawing which shows typically the other example of the optical system for a measurement concerning this invention.

Explanation of symbols

5 ... 1st lens 6 ... Aperture stop 7 ... 2nd lens 8 ... Light guide 8a ... Incident end face

Claims (5)

A first lens that faces a measurement object and has a positive power and collects and collimates a light beam from each point of the measurement target area of the measurement object;
An aperture stop disposed at a substantially rear focal position of the first lens and restricting an incident angle of a light beam incident on the first lens from each point;
A second lens having a front focal point at a substantially disposed position of the aperture stop and forming an image of the measured region at a rear focal point based on a light beam incident through the aperture stop;
A light beam splitting unit that has an incident end surface at a substantially rear focal position of the second lens and divides each light beam incident on the incident end surface into three light beam groups;
A light receiving means for receiving each of the light flux groups through an interference filter disposed to face the exit surface of the light flux splitting means,
An incident angle of a light beam at an incident end face position of the light beam splitting unit is set smaller than an incident angle at the aperture stop position, and an output from the light receiving unit is used for measuring a color characteristic. Optical system for measurement.   In order to make the incident angle at the incident end face position of the light beam dividing means smaller than the incident angle at the aperture stop position, the size of the incident end face of the light beam dividing means is set larger than the size of the aperture stop. The measuring optical system according to claim 1, wherein:   3. The measurement optical system according to claim 2, wherein a field stop for defining the size of the measurement area is disposed on an incident end face of the light beam splitting unit.   The light beam splitting means comprises a light guide that bundles a plurality of optical fibers, and the plurality of optical fibers are bundled so that the image forming positional relationship of the light beam formed on the incident end face becomes pseudo-random. The measuring optical system according to claim 3, wherein the measuring optical system is provided.   The light-receiving means receives the light condensed by the condensing lens and the condensing lens that is disposed to face the emitting end surface and has a positive power for condensing the light beam emitted from the emitting end surface. The measuring optical system according to claim 4, further comprising: a light receiving portion that performs measurement.

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