JP2006250656A - Method and apparatus for measuring illuminance unevenness of light emitting device array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the illuminance unevenness of a light emitting device array simply and correctly. <P>SOLUTION: The measurement equipment for measuring the illuminance unevenness of an LED module provided with an LED array includes an oval diffusion plate dispersed with light diffusive material in the transparent plate. At the measurement, the LED module is turned on while saving the diffusion plate from the light path, the output light from the LED array is made directly to focus on the CCD sensor, the first imaging data (direct light data) is obtained. Then, the diffusion plate is inserted into the light path, and transmitted light which is the output light from the LED array transmitted through the diffusion plate is made to focus on the CCD image sensor, the second imaging data (transparent light data) is obtained. By verifying the two kinds of imaging data, the position of device corresponding to generation part of the unevenness of the illuminance is specified. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for measuring illuminance unevenness of a light emitting element array in which a plurality of light emitting elements are arranged.

  A light source device (for example, see Patent Documents 1 to 4 below) including an LED array in which a plurality of LED (Light Emitting Diode) chips as light emitting elements are arranged is known. It is used as an irradiation light source for photosensitive materials such as recording paper. Such a light source device often has to irradiate light with a uniform illuminance on the light receiving surface of the photosensitive material.

  In an LED array, a plurality of LED chips, which are point light sources, are arranged and mounted on an aluminum substrate or the like, thereby forming a flat light emitting surface. Therefore, if there is a luminance difference between individual LED chips or variations in the mounting position, illuminance unevenness occurs in the light emitting surface. Therefore, in the LED array, for example, the illuminance unevenness is measured for each unit at the time of manufacture, and the luminance correction of each LED chip is performed so as to eliminate the illuminance unevenness according to the measurement result.

  Irradiance measurement is performed by, for example, irradiating light from the LED array to a photosensitive material in which the light receiving surface is arranged in parallel to the light emitting surface of the LED array, developing the irradiated area, and receiving the received light image. This is done by visually confirming. For example, when illuminance unevenness is confirmed in the received light image, the LED chip in the LED array corresponding to the location where the illuminance unevenness is generated is specified, and the drive current value of the LED chip is eliminated. Correct as follows.

JP 2002-374004 A JP-A-7-190726 JP 2000-36209 A Japanese Patent Laid-Open No. 11-282097

  However, since the method described above actually checks the illuminance unevenness using a photosensitive material, it is possible to accurately grasp the state of occurrence of the unevenness, but the work itself is a manual operation, so that the work efficiency is poor. There is. Therefore, a CCD image sensor is used to receive the output light from the LED array, and the received light image is displayed on a monitor to check the illuminance unevenness of the LED array. However, in the photosensitive material, the irradiated light diffuses inside, whereas the CCD image sensor does not have the internal diffusion of light like the photosensitive material, so that the received image does not match that of the photosensitive material, There was a problem that the illuminance unevenness could not be measured accurately.

  An object of the present invention is to provide a method and an apparatus for measuring illuminance unevenness of a light emitting element array, which can measure illuminance unevenness easily and accurately.

An uneven illuminance measuring apparatus for a light emitting element array according to the present invention is an uneven illuminance measuring apparatus for a light emitting element array in which a plurality of light emitting elements are arranged on a substrate. Imaging means for receiving light distribution data to obtain light distribution data representing the light distribution of the light emitting surface;
An opal type diffusion plate provided in an optical path from the light emitting surface to the light receiving surface so as to be insertable / removable and containing a light diffusing substance dispersed inside the transparent plate, The first light distribution data for specifying the position of each light emitting element on the substrate is obtained by receiving light from the light emitting surface with the imaging means in a state of being retracted from the light source, and the opal type A second light distribution for examining the illuminance distribution of the transmitted light by receiving the transmitted light emitted from the light emitting surface and transmitted through the opal type diffuser with the diffuser inserted in the optical path. It is characterized by acquiring data.

  It is preferable to provide analysis means for analyzing illuminance unevenness based on the two types of light distribution data of the first light distribution data and the second light distribution data.

  The analysis means checks the presence / absence of illuminance unevenness based on the second light distribution data and the illuminance unevenness occurrence portion where it occurs, and the light emitting element corresponding to the illuminance unevenness generation portion based on the first light distribution data Is preferably specified.

  Furthermore, it is preferable to provide correction value calculation means for calculating a correction value of the drive current of each light emitting element so that unevenness in illuminance is eliminated based on the analysis result by the analysis means.

  It is preferable to provide a monitor for visualizing and displaying the light distribution status based on the first and second light distribution data.

  In the imaging means, at least four light receiving cells arranged in a matrix on the light receiving surface are assigned to one light emitting element, and each imaging data obtained by the plurality of light receiving cells is assigned. It is preferable to obtain the peak value of the light output of one light emitting element by averaging.

  It is preferable to provide a moving mechanism for moving the opal type diffusion plate between an insertion position for inserting the opal type diffusion plate into the optical path and a retreat position for retracting from the insertion position.

  The method for measuring illuminance unevenness of a light emitting element array according to the present invention is an optical path from a light emitting surface of the light emitting element array to a light receiving surface of an imaging means in the method of measuring uneven illuminance of a light emitting element array in which a plurality of light emitting elements are arranged on a substrate. From the state in which the opal diffusion plate included in a state where the light diffusion material is dispersed inside the transparent plate is retracted, the light emitted from the light emitting surface is received by the imaging unit, A first step of acquiring first light distribution data for specifying a position of each light emitting element on the substrate; and the opal diffused light emitted from the light emitting surface in a state where the opal diffuser is inserted in the optical path. And a second step of acquiring second light distribution data for examining the illuminance distribution of the transmitted light by receiving the transmitted light transmitted through the plate by the imaging means.

  According to the present invention, the opal diffusion plate contained in a state where the light diffusing material is dispersed inside the transparent plate is retracted from the optical path from the light emitting surface of the light emitting element array to the light receiving surface of the imaging unit. In the state, the light emitted from the light emitting surface is received by the imaging means, thereby obtaining first light distribution data for specifying the position of each light emitting element on the substrate, and the opal diffuser plate Second light distribution data for examining the illuminance distribution of the transmitted light by receiving the transmitted light emitted from the light emitting surface and transmitted through the opal diffuser plate in the state where it is inserted in the optical path; Therefore, by comparing these two kinds of light distribution data, the illuminance unevenness can be measured easily and accurately.

  As shown in FIG. 1A, the LED module 10 includes, for example, an aluminum substrate 11 with high heat dissipation, an LED array 12 mounted on the substrate 11, and the LED array 12 for driving. Driver IC14. The LED array 12 is formed by arranging a plurality of LED chips 13 in a line. A conductive pattern is formed on the substrate 11, and each LED chip 13 and a terminal of the driver IC 14 are bonded to the substrate 11 with wires and electrically connected via the conductive pattern. Since the LED chip 13 generates a large amount of heat, a heat sink 16 is attached to the substrate 11 on the surface opposite to the chip mounting surface. As shown in FIG. 1B, for example, the LED module 10 irradiates the photosensitive material 17 being conveyed with light, and exposes the light receiving surface with uniform illuminance.

  FIG. 2 shows a measuring device 21 that measures the illuminance unevenness of the LED module 10. The measuring device 21 includes a CCD camera 22 and a device main body 23. The CCD camera 22 includes a CCD image sensor 24 that is an image pickup unit and a lens unit 26 disposed in front of the CCD image sensor 24. The CCD image sensor 24 photoelectrically converts light incident on the light receiving surface 24a and outputs it as an electrical imaging signal. The LED module 10 is set so that its light emitting surface 10a is parallel to the light receiving surface 24a.

  Of course, the optical path from the light emitting surface 10a to the light receiving surface 24a may not be a straight line as in this example, and an optical component such as a reflection mirror may be arranged in the optical path and bent. In that case, the light emitting surface 10a and the light receiving surface 24a are not necessarily parallel to each other. If the optical path is bent as described above, the degree of freedom in layout of the LED module 10 and the CCD image sensor 24 is increased, which contributes to, for example, downsizing of the measuring device 21.

  The lens unit 26 focuses the output light output from the light emitting surface 10a on the light receiving surface 24a. When the LED module 10 is turned on, the output light enters the light receiving surface 24a of the CCD image sensor 24, and the light distribution on the light emitting surface 10a is projected onto the light receiving surface 24a. The CCD image sensor 24 outputs an imaging signal representing the light distribution to the apparatus main body 23.

  As shown in FIG. 3, the light receiving surface 24a of the CCD image sensor 24 is configured by a plurality of light receiving cells 25 made of photosensors arranged in a matrix, as is well known. Then, the number of pixels of the CCD image sensor 24 is determined so that, for example, four light receiving cells 25 are assigned to one LED chip 13. This is because the light output of each light emitting surface (hereinafter referred to as the element light emitting surface) of each LED chip 13 has a large luminance difference (output difference) between the central luminance and the peripheral luminance. For this reason, for example, if the sensitivity is increased to such an extent that peripheral luminance can be captured, the luminance range of the light output often does not fall within the dynamic range of the CCD image sensor 24, such that the vicinity of the center is blown out. It is difficult to capture the maximum luminance of 13. Therefore, by assigning a plurality of light receiving cells 25 to one LED chip 13 and averaging the light amount signals detected by each light receiving cell 25, the maximum luminance of each LED chip 13 can be compared. .

  The number of light receiving cells 25 assigned to one LED chip 13 may be four or more. The LED chip 13 is mounted on the substrate 11 according to a predetermined arrangement rule, but due to an error that occurs during mounting, the mounting position of the LED chip 13 varies vertically and horizontally as shown in FIG. Therefore, if the allocation number of the light receiving cells 25 is increased, the area of the light receiving area A allocated to one LED chip 13 is increased accordingly, and therefore, it is easy to fit each LED chip 13 in the light receiving area A. can get.

  The apparatus body 23 includes a controller 31, a monitor 32, an HDD 33, an A / D converter 34, a data analysis unit 36, and a correction value calculation unit 37. The controller 31 includes a CPU, a memory, and the like, and controls each part of the apparatus. The A / D converter 34 converts the analog imaging signal output from the CCD image sensor 24 into digital imaging data. This imaging data is stored in a HDD (Hard Disk Drive) 33 that is a data storage device as light distribution data representing the light distribution of the LED array 12. On the monitor 32, an image obtained by visualizing the light distribution of the LED array 12 projected on the light receiving surface 24a of the CCD image sensor 24 based on the light distribution data, a graph showing the illuminance distribution, and the like are displayed.

  The data analysis unit 36 performs illuminance unevenness measurement based on the light distribution data. Based on the analysis result of the data analysis unit 36, the correction value calculation unit 37 corrects the drive current value of each LED chip 13 determined in advance so that the illuminance unevenness of the LED array 12 is eliminated, and performs correction driving. Calculate the current value.

  In addition, a diffusing plate 41 for diffusing the output light from the light emitting surface 10a is detachably disposed in the optical path between the LED module 10 and the CCD camera 22. As shown in FIG. 4, the diffusing plate 41 is an opal type diffusing plate in which a light diffusing material 43 is kneaded into a transparent glass plate 42. The diffuser plate generally has the effect of dimming and diffusing strong light, but the opal diffuser plate has a light diffusing material dispersed inside, and transmitted light passing through it diffuses light inside. Arise. As described above, the opal diffuser has light diffusion characteristics close to those of the photosensitive material 17 as compared with a frost diffuser whose surface is roughened (for example, polished glass). Therefore, it is possible to simulate the light receiving state of the photosensitive material 17 by capturing the transmitted light.

  There are various types of photosensitive materials, and the light diffusion characteristics differ depending on the type. The light diffusing characteristics of the opal diffuser also differ depending on the type and amount of light diffusing substances contained in it, so the opal diffuser used is the one closest to the light diffusing characteristics of various photosensitive materials. It is preferable.

  The measuring device 21 is provided with a moving mechanism 46 that moves the diffuser plate 41 between an insertion position for inserting it into the optical path and a retracted position for retracting from the insertion position. The moving mechanism 46 is controlled by the controller 31. The light distribution on the light emitting surface 10a is shot in two times, with the diffuser plate 41 inserted into the optical path and withdrawn, and uneven illuminance is analyzed based on these two types of light distribution data. . Moreover, the imaging | photography in each state may not be once, but you may image | photograph several times and average them. This improves the measurement accuracy.

  FIG. 5 shows light distribution data obtained by retracting the diffusing plate 41 from the optical path and receiving the output light from the light emitting surface 10a by the light receiving surface 24a. FIG. 6 shows that the diffusing plate 41 is inserted into the optical path. The light distribution data obtained by irradiating the diffusion plate 41 with output light from the light emitting surface 10a and receiving the transmitted light with the light receiving surface 24a is shown. Here, since the light distribution data shown in FIG. 5 is light distribution data obtained without being transmitted through the diffusion plate 41, it is called direct light data, and the light distribution data shown in FIG. 6 is transmitted through the diffusion plate 41. The light distribution data thus obtained is referred to as transmitted light data. FIGS. 5A and 6A are light distribution images obtained by visualizing the light distribution of the light emitting surface 10a formed on the light receiving surface 24a of the CCD image sensor 24. FIGS. (B) represents the illuminance distribution in the longitudinal direction at a specific position in the width direction of the light emitting surface 10a.

  When the diffusing plate 41 is retracted from the optical path, the light diffusion of each LED chip 13 is small. Therefore, by directly acquiring the optical data, the mounting position of each LED chip 13 is obtained as shown in FIG. As shown in FIG. 5B, the luminance difference (output difference) of the maximum luminance (peak value of light output) of each LED chip 13 can be measured. Of course, when the maximum luminance exceeds the dynamic range of the CCD image sensor 24, the luminance difference cannot be measured. In such a case, sensitivity adjustment of the CCD image sensor 24 is required. Furthermore, in the case of direct light data, since the light diffusion characteristics of the light receiving surface 24a of the CCD image sensor 24 and the photosensitive material 17 are different, it is difficult to measure the light diffusion state when the photosensitive material 17 is irradiated, and uneven illuminance is present. It is not possible to specify the presence or absence and location of the occurrence.

On the other hand, by obtaining the transmitted light data, it is possible to measure the occurrence of uneven illuminance of the LED array 12. Since the diffusion plate 41 has a diffusion characteristic similar to that of the photosensitive material 17, when the transmitted light is received by the CCD image sensor 24, the output light from the LED array 12 is transmitted to the photosensitive material 17 as shown in FIG. The diffusion state as if it was irradiated can be captured. In this transmitted light image, a portion with high density indicates low luminance, and a portion with low density indicates high luminance. As shown in this figure, the luminance of the central region in the width direction of the LED array 12 is the highest, and the luminance decreases toward the peripheral region. FIG. 6B is a graph showing the illuminance distribution in the longitudinal direction at a specific position in the width direction. From these images in FIG. 6A and the illuminance distribution in FIG. 6B, the presence / absence of illuminance unevenness in the light emitting surface 10a and the occurrence portion thereof are specified.

  Based on the transmitted light data, the data analysis unit 36 checks the presence / absence of illuminance unevenness and the portion where the illuminance occurs and collates the transmitted light data and the direct light data so that the respective pixel positions correspond to each other. Thus, the LED chip 13 corresponding to the portion where the illuminance unevenness is generated is specified. The correction value calculation unit 37 corrects the preset drive current value so that the uneven illuminance due to the identified LED chip 13 is eliminated. Then, the corrected drive current value (correction value) is stored in the HDD 33 together with the identification information of the LED chip 13. This correction value data is used as a light emission control value of the LED module 10.

  As shown in FIG. 7, the LED module 10 constitutes a light source device 62 together with, for example, a controller 61 that controls the LED module 10. The light source device 62 is provided with an EEPROM 63. In the EEPROM 63, the drive current values (I1 to I10) corrected by the measuring device 21 are stored together with the identification IDs (No1 to No10) of the LED chips 13. The controller 61 reads the drive current value from the EEPROM 63 and turns on the LED module 10 based on the value.

  Hereinafter, the operation of the above configuration will be described with reference to the flowchart shown in FIG. When the LED module 10 is assembled, it is set in the measuring device 21 and uneven illuminance is measured. The LED module 10 is turned on. First, the diffusion plate 41 is retracted from the optical path, and the output light from the LED array 12 is directly received by the CCD image sensor 24 to directly acquire optical data. Next, the diffusing plate 41 is inserted into the optical path, and the transmitted light data transmitted through the diffusing plate 41 is acquired by the CCD image sensor 24.

  The data analysis unit 36 analyzes the transmitted light data to check the presence / absence of uneven illuminance and the portion where the illuminance occurs, and compares the transmitted light data with the direct light data to identify the LED chip 13 corresponding to the uneven illuminance occurrence portion. To do. The correction value calculation unit 37 calculates a correction value (drive current value) for the identified LED chip 13. The calculated correction value is stored in the EEPROM 63 of the light source device 62. Note that the LED module 10 may be turned on using this correction value, and the measurement and the calculation of the correction value may be repeated according to the above-described procedure.

  As described above, since the illuminance unevenness occurrence state is examined based on the transmitted light data transmitted through the diffusion plate 41, the light receiving state can be predicted without using the photosensitive material 17, so that it can be easily and accurately performed. It is possible to measure illuminance unevenness.

  In the above embodiment, the acquired light distribution data is analyzed by the data analysis unit, and the driving current value is corrected by the correction value calculation unit based on the analysis result. However, based on the light distribution data Then, the light distribution and the illuminance distribution on the light emitting surface may be displayed on a monitor, and the drive current value may be obtained by performing an analysis by visually confirming it.

  In the above embodiment, the present invention has been described by taking an LED chip as an example of a light emitting element. However, the present invention is not limited to an LED chip, and can be applied to other light emitting elements such as an EL (Electro Luminescence) element. Moreover, although the number of array lines of the LED array has been described as an example of one row, it is needless to say that a plurality of rows may be used.

  In the above embodiment, the light emitting element array is used as an irradiation light source for the photosensitive material. However, the light emitting element array is used for headlights for automobiles, indoor lighting, backlights for liquid crystal displays, strobe devices, signal lights, and the like. Is possible. When using a light emitting element array for such various uses, it is often used in combination with a diffusion plate. The present invention can also be applied when measuring the illuminance unevenness of such a light emitting element array. In this case, it is preferable to perform measurement by selecting an opal type diffusion plate used in the illuminance unevenness measuring device in accordance with the light diffusion characteristics of the diffusion plate combined with the light emitting element array.

It is an external view of an LED module. It is a block diagram of a measuring device. It is explanatory drawing of the light-receiving surface of a CCD image sensor. It is explanatory drawing of an opal type | mold diffuser plate. It is explanatory drawing of direct optical data. It is explanatory drawing of the transmitted light data. It is explanatory drawing of a light source device. It is a flowchart which shows a measurement procedure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 LED module 12 LED array 13 LED chip 21 Measuring apparatus 22 CCD camera 24 CCD image sensor 31 Movement mechanism 36 Data analysis part 37 Correction value calculation part 41 Diffusion plate

Claims (8)

In an illuminance unevenness measuring device of a light emitting element array in which a plurality of light emitting elements are arranged on a substrate,
Imaging means for receiving light emitted from a light emitting surface of the light emitting element array at a light receiving surface and obtaining light distribution data representing light distribution on the light emitting surface;
An opal type diffusion plate provided in an optical path from the light emitting surface to the light receiving surface so as to be insertable / removable and containing a light diffusing substance dispersed inside the transparent plate;
First light distribution data for specifying the position of each light emitting element on the substrate is received by the imaging means with light from the light emitting surface in a state where the opal diffuser is retracted from the optical path. And obtaining the illuminance distribution of the transmitted light by receiving the transmitted light emitted from the light emitting surface and transmitted through the opal diffuser with the imaging means in a state where the opal diffuser is inserted into the optical path. A device for measuring illuminance unevenness of a light-emitting element array, characterized by acquiring second light distribution data for checking.   The illuminance unevenness measurement of the light emitting element array according to claim 1, further comprising an analyzing unit that analyzes the illuminance unevenness based on the two types of light distribution data of the first light distribution data and the second light distribution data. apparatus.   The analysis means checks the presence / absence of illuminance unevenness based on the second light distribution data and the illuminance unevenness occurrence portion where it occurs, and the light emitting element corresponding to the illuminance unevenness generation portion based on the first light distribution data The illuminance unevenness measuring apparatus for a light emitting element array according to claim 2, wherein:   The correction value calculating means for calculating the correction value of the drive current of each light emitting element is provided so as to eliminate unevenness of illuminance based on the analysis result by the analyzing means. 4. An uneven illuminance measuring apparatus for a light emitting element array according to 3.   5. The illuminance unevenness measuring apparatus for a light-emitting element array according to claim 1, further comprising a monitor for visualizing and displaying a light distribution state based on the first and second light distribution data. .   In the imaging means, at least four light receiving cells arranged in a matrix on the light receiving surface are assigned to one light emitting element, and each imaging data obtained by the plurality of light receiving cells is assigned. The average illuminance unevenness measuring device for a light emitting element array according to any one of claims 1 to 5, wherein the peak value of the light output of one light emitting element is obtained.   The light emission according to any one of claims 1 to 6, further comprising a moving mechanism for moving the opal diffuser plate between an insertion position for inserting the opal type diffusion plate into the optical path and a retraction position for retreating from the insertion position. Device array illuminance unevenness measuring device. In a method for measuring illuminance unevenness of a light emitting element array in which a plurality of light emitting elements are arranged on a substrate,
The light emitting surface in a state in which an opal type diffusion plate contained in a state where a light diffusing substance is dispersed inside the transparent plate is retracted from an optical path from the light emitting surface of the light emitting element array to the light receiving surface of the imaging unit. A first step of acquiring first light distribution data for specifying the position of each light emitting element on the substrate by receiving the light emitted from the image pickup means;
In order to check the illuminance distribution of the transmitted light by receiving the transmitted light emitted from the light emitting surface and transmitted through the opal diffuser with the imaging means inserted in the state where the opal diffuser is inserted in the optical path. A second step of acquiring second light distribution data; and a method for measuring illuminance unevenness of a light-emitting element array.

Images