Optics: measuring and testing – Lens or reflective image former testing
Reexamination Certificate
2000-01-31
2001-11-20
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Lens or reflective image former testing
Reexamination Certificate
active
06320652
ABSTRACT:
This application is based on patent application Hei.11-23096 filed in Japan, the contents of which are hereby incorporated by references.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical measuring apparatus used, for example, in a calibration of an apparatus such as a liquid crystal display panel (hereinafter abbreviated as LCD panel).
2. Description of the Related Art
An optical measuring apparatus has conventionally been used in a manufacturing line of an LCD panel for measuring optical characteristics such as chromaticity and luminance. Adjustment of white balance, quality control and shipping inspection of the LCD panel are executed by using the result of the measurement of the optical characteristics.
A conventional optical measuring apparatus such as the LCD color analyzer CA-110 produced by MINOLTA CO., LTD. comprises a probe and a main unit. The probe includes a photosensor for receiving rays emitted from a region of an LCD panel which is to be measured (hereinafter abbreviated as measurement region). The main unit calculates xyY (chromaticity coordinates and luminance) and T&Dgr;uvY (correlated color temperature, color difference and luminance), which are established by Commission Internationale de I'Eclairage (CIE), by basing on output of the photosensor of the probe. The calculated values are displayed on a display panel of the main unit.
The above-mentioned conventional optical measuring apparatus for the LCD panel is a noncontact type apparatus, in which the probe is positioned distant by a predetermined distance from the LCD panel. It is necessary to position the probe accurately at the position distant from the predetermined distance from the LCD panel.
Furthermore, in the measurement using the noncontact type optical measuring apparatus, rays of ambient illumination are reflected by a surface of the LCD panel, so that the reflected rays can enter into the photosensor of the probe as stray rays. When the stray rays enter into the probe, that is, the reflected rays of the ambient illumination are included in rays directly emitted from the measurement region of the LCD panel, output value from the photosensor of the probe is varied. As a result, the optical characteristics of the LCD panel are not estimated accurately. Especially, when the luminance of the LCD panel is relatively low, the stray rays largely affects the accuracy of the measurement. For solving this problem, it is necessary to reduce the ambient illumination of the prove and the LCD panel.
In another conventional optical measuring apparatus such as the CRT color analyzer CA-100 produced by MINOLTA CO., LTD., which is used for measuring optical characteristics of a CRT (Cathode Ray Tube) apparatus, a probe is directly contacted on a measurement region on The CRT apparatus. When this contact type apparatus is used for measuring the optical characteristics of the LCD panel, it causes the following problems.
The LCD panel is configured by that a liquid crystal layer is disposed between two glass plates for making the thickness of the liquid crystal layer even. When the probe is directly contacted on the surface of the LCD panel, the glass plate to which the probe is contacted is warped, so that the thickness of the liquid crystal layer in a region around the contacting portion of the probe and the LCD panel is varied. When the thickness of the liquid crystal layer is varied, colors of an image displayed on the region of the LCD panel is varied. In this case, the region where the thickness of the liquid crystal layer is varied corresponds to the measurement region. Thus, it is substantially impossible to measure the optical characteristics of the LCD panel by the conventional contact type apparatus.
On the other hand, it is conventionally known that the chromaticity and the luminance of the image displayed on the LCD panel varies when an observer moves from the front center of the LCD panel to the side thereof. This phenomenon is caused by light distribution of the LCD panel, that is, the larger the exit angle of the rays emitted from the LCD panel becomes, the smaller the intensity of the light becomes.
A light distribution of a typical LCD panel on the market is shown in FIG.
19
A. The light distribution of the LCD panel is substantially symmetrical with respect to the normal “N” at the center of the LCD panel
12
in both of the vertical direction XX and the horizontal direction YY, so that an image can be displayed preferably when it is observed from the front center thereof. However, when the LCD panel is observed from the side at an observing angle larger than a predetermined angle &agr; against the normal “N”, the chromaticity and the luminance of the image are largely varied. It is generally said that the angle of view of the LCD panel is narrow.
In the conventional noncontact type optical measuring apparatus, the probe is positioned distant from the LCD panel, so that the probe receives not only paraxial rays but also the rays having exit angles larger than the predetermined angle &agr; (in the following description, the angle &agr; is called “maximum exit angle”). Thus, the accuracy and the repeatability of the measurement of the optical characteristics of the LCD panel by the conventional optical measuring apparatus are not so high.
Furthermore, in a kind of the LCD panel, the symmetry of the light distribution against the normal “N” will be deteriorated as shown in
FIG. 19B
when the display of the image is changed. For example, when the color of the image is gradually changed from white to black, it is observed that an exit angle of rays against the normal “N”, at which the luminance of the image becomes the largest, increases. The variation of the light distribution of the LCD panel on the market is generally restricted only in the vertical direction XX in the figure. In this description, the spatial oblique coordinates are designated by symbols XX, YY and ZZ for distinguishing from tristimulus values X, Y and Z.
As shown in
FIG. 20
, even when the photosensor R of the probe is disposed on the normal “N” at the center of the LCD panel
12
for receiving rays emitted from the measurement region
121
, the output S
R
from the photosensor R varies corresponding to the variation of the light distribution of the LCD panel
12
.
SUMMERY OF THE INVENTION
A purpose of this invention is to provide a contact type optical measuring apparatus by which optical characteristics of an object such as an LCD panel can be measured accurately.
An optical measuring apparatus in accordance with an aspect of the present invention comprises a housing with a contact portion for contacting on a surface of an object at position distant from a region to be measured, and a photosensor fixed on the housing and positioned with respect to the contact portion.
By such a configuration, when the optical measuring apparatus is directly contacted on the object such as the LCD panel, thickness of a liquid crystal layer in the vicinity of the contact portion varies. However, the contact portion is distant from the region to be measured (measurement region), so that the thickness of the liquid crystal layer in the measurement region is hardly varied. Since the photosensor is fixed on the housing, the photosensor is automatically positioned at the position distant by a predetermined distance from the surface of the LCD panel. Furthermore, the housing shields the ambient illumination, so that no stray ray enters into the photosensor.
Furthermore, it is preferable further to comprise an optical system guiding rays emitted from the region to be measured and having exit angles equal to or smaller than a predetermined angle. By such a configuration, stray rays having the exit angle larger than the predetermined angle hardly enter the photosensor. The noise component due to the stray rays becomes much smaller, so that the S/N of the output signal of the apparatus increases.
REFERENCES:
patent: 5293178 (1994-03-01), Kobayashi
patent: 5696550 (1997-12-01), Aoki et al.
patent: 5757346 (
Kamiya Makoto
Morimoto Teruo
Naruse Kazuhiko
Saika Takashi
Font Frank G.
McDermott & Will & Emery
Minolta Co. , Ltd.
Stafira Michael P.
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