Patent Publication Number: US-2022221504-A1

Title: Test apparatus, test method, and computer-readable storage medium

Description:
The contents of the following Japanese patent application(s) are incorporated herein by reference:
     NO. 2021-003813 filed in JP on Jan. 13, 2021   

     BACKGROUND 
     1. Technical Field 
     The present invention relates to a test apparatus, a test method, and a computer-readable storage medium. 
     2. Related Art 
     A method is known in which one of a pair of LEDs to be inspected is caused to emit light and the other is caused to receive the light, and optical characteristics of the LED are inspected using a current value of a current output by a photoelectric effect (see, for example, Patent Documents 1 and 2). 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese translation publication of PCT route patent application No. 2019-507953 
         Patent Document 2: Japanese Patent Application Publication No. 2010-230568 
       
    
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an example of an overall view illustrating an outline of a test apparatus  100  for testing a plurality of LEDs  10 . 
         FIG. 2  is an example (A) of a side view and an example (B) of a plan view of a placement unit  150 , an LED group placed on the placement unit  150 , and an electrical connection unit  110  in a state where a plurality of probes  113  are in contact with a specific set of the plurality of LEDs  10  in the LED group. 
         FIG. 3  is an example of a plan view of the placement unit  150  and a light intensity measurement unit  170  placed on the placement unit  150 . 
         FIG. 4  is an example of a flowchart for explaining a flow of a test method by the test apparatus  100 . 
         FIG. 5  is an example of a flowchart illustrating a flow of generating a correction map to calculate a corrected measurement value of a photoelectric signal of each LED  10  by the test apparatus  100 . 
         FIG. 6  is an example of a flowchart for explaining a flow of calculating a correction value for calibrating the measurement values of a plurality of sensors  173  of the light intensity measurement unit  170  by the test apparatus  100 . 
         FIG. 7  is an example of an overall view illustrating an outline of a test apparatus  200  for testing a plurality of LEDs  20 . 
         FIG. 8  is an example of a plan view of the placement unit  150  and a light intensity measurement unit  175  placed on the placement unit  150 . 
         FIG. 9  is an example of a flowchart for explaining a flow of a test method by the test apparatus  200 . 
         FIG. 10  is an example of a flowchart for explaining a flow of generating a correction map to calculate a corrected measurement value of the photoelectric signal of each LED  10  by the test apparatus  200 . 
         FIG. 11  is another example of a flowchart for explaining a flow of generating a correction map to calculate a corrected measurement value of the photoelectric signal of each LED  10  by the test apparatus  200 . 
         FIG. 12  is still another example of a flowchart for explaining a flow of generating a correction map to calculate a corrected measurement value of the photoelectric signal of each LED  10  by the test apparatus  200 . 
         FIG. 13  is another example of a flowchart for explaining a flow of a test method by the test apparatus  200 . 
         FIG. 14  is still another example of a flowchart for explaining a flow of a test method by the test apparatus  200 . 
         FIG. 15  is an example of an overall view illustrating an outline of a test apparatus  300  for testing a plurality of LEDs  30 . 
         FIG. 16  is a diagram illustrating an example of a computer  1200  in which a plurality of aspects of the present invention may be embodied in whole or in part. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all combinations of features described in the embodiments are essential to the solution of the invention. In the drawings, the same or similar parts are denoted by the same reference numerals, and redundant description may be omitted. 
       FIG. 1  is an example of an overall view illustrating an outline of a test apparatus  100  for testing a plurality of LEDs  10 . In  FIG. 1 , an X axis having a +X direction in the right-hand direction facing the paper surface, a Z axis having a +Z direction in the upper direction facing the paper surface, and a Y axis having a +Y direction in the depth direction facing the paper surface are illustrated so as to be orthogonal to each other. Hereinafter, description may be made using these three axes. 
     The test apparatus  100  uses the photoelectric effect of the LED  10  to collectively test the optical characteristics of the plurality of LEDs  10  on the basis of the photoelectric signal output from the LED  10  irradiated with light. The test apparatus  100  includes an electrical connection unit  110 , a light source unit  120 , a temperature control unit  126 , a measuring unit  130 , a control unit  140 , a storage unit  145 , a placement unit  150 , and a blocking unit  160 . The test apparatus  100  may not include the temperature control unit  126 , the storage unit  145 , the placement unit  150 , and the blocking unit  160 . 
     The test apparatus  100  according to the present embodiment collectively tests the optical characteristics of a specific set of the plurality of LEDs  10  in the LED group in a state where the LED group in which the plurality of LEDs  10  are formed on a wafer  15 , which is the LED wafer before the wiring by the backplane is provided, is placed on the placement unit  150 . The LED  10  in the present embodiment is a micro LED having a dimension of 100 μm or less. Note that, instead of the micro LED, the LED  10  may be a mini LED having a dimension larger than 100 μm and equal to or less than 200 μm, an LED having a dimension larger than 200μm, or another light emitting device such as an LD. 
     In addition, the plurality of LEDs  10  in the present embodiment are not electrically connected to each other on the wafer  15 . Note that the plurality of LEDs  10  may be formed on a wafer provided with electric wiring or on a glass-based panel (PLP) having a substantially rectangular outer shape, and may be electrically connected to each other to be formed in units or cells. In this case, for example, the respective colors of RGB may be mixed by a technique of performing laser lift-off and transferring from the respective monochromatic wafers of RGB or a technique of dyeing or applying a fluorescent paint on a monochromatic wafer of any of RGB. 
     The electrical connection unit  110  is, for example, a probe card (probe substrate), and is electrically connected to a terminal  11  of each of the plurality of LEDs  10  to be tested. Note that, in the specification of the present application, in a case where the term “being electrically connected” is defined, it is intended to be electrically connected by contact or to be electrically connected in a non-contact manner. The electrical connection unit  110  in the present embodiment is electrically connected by being in contact with the terminal  11  of each of the plurality of LEDs  10 , but may be electrically connected in a non-contact manner by, for example, electromagnetic induction or near field communication. 
     The electrical connection unit  110  in the present embodiment also sequentially switches a set of the plurality of LEDs to be tested to which it connects from among the LED group placed on the placement unit  150  by the placement unit  150  moving with the LED group placed thereon. The electrical connection unit  110  in the present embodiment is disposed between the light source unit  120  and the plurality of LEDs  10 , and includes a substrate  111  and a plurality of probes  113 . 
     The substrate  111  has an opening  112  that allows light from the light source unit  120  to pass toward the plurality of LEDs  10 . In  FIG. 1 , the opening  112  is indicated by a broken line. 
     The plurality of probes  113  extend from the substrate  111  toward each of the plurality of LEDs  10  exposed in the opening  112  and contact the terminal  11  of each of the plurality of LEDs  10 . The other end of each probe  113  opposite to the one end in contact with the terminal  11  is electrically connected to the electric wiring provided on the substrate  111 . The plurality of electric wirings of the plurality of probes  113  extend from the side surface of the substrate  111  and are electrically connected to the measuring unit  130 . 
     Note that it is preferable that the plurality of probes  113  have the same shape and dimension with each other and have the same distance, with each other, from the LEDs  10  they are in contact with so that the light reception amounts of each of the plurality of LEDs  10  are equal to each other. In addition, each of the plurality of probes  113  is preferably plated or colored so that light is not diffusely reflected on the surface of the probe  113 . 
     The light source unit  120  collectively irradiates the plurality of LEDs  10  with light. The light source unit  120  in the present embodiment irradiates the plurality of LEDs with light in a reaction wavelength band of the plurality of LEDs. The light source unit  120  in the present embodiment includes a light source  121  and a lens unit  123 . 
     The light source  121  emits light in the reaction wavelength band of the plurality of LEDs  10 . The light source  121  may be, for example, a light source that emits light in a wide wavelength band, such as a xenon light source, or may be a light source that emits light in a narrow wavelength band, such as a laser light source. The light source  121  may include a plurality of laser light sources having wavelengths that are different from each other. 
     The lens unit  123  includes one or more lenses, is provided adjacent to the irradiation unit of the light source  121 , and converts the diffused light irradiated from the light source  121  into parallel light  122 . In  FIG. 1 , the parallel light  122  is indicated by hatching. The projection plane of the parallel light  122  in the XY plane covers at least the opening  112  of the substrate  111 . 
     The temperature control unit  126  suppresses temperature rise of the plurality of LEDs  10  due to irradiation with the light. The temperature control unit  126  in the present embodiment includes a temperature suppression filter  125  and a filter holding unit  124 . The temperature suppression filter  125  has high light transmittance and absorbs a heat ray of incident light. The filter holding unit  124  is provided adjacent to the lens unit  123  and holds the temperature suppression filter  125 . Note that the temperature control unit  126  may further include a cooler that cools the heat absorbed by the temperature suppression filter  125 . 
     In order to keep the temperatures of the plurality of LEDs  10  constant, the temperature control unit  126  may include, instead of or in addition to the above configuration, a temperature applying apparatus that adjusts the temperatures of the plurality of LEDs  10 , an air blowing mechanism that blows air toward the plurality of LEDs  10 , and the like. In a case where the air blowing mechanism is used, the temperature control unit  126  may further include a static electricity removing unit that prevents the plurality of LEDs  10  from being charged with static electricity when air is blown by the air blowing mechanism. The static electricity removing unit may be, for example, an ionizer. The above described temperature applying apparatus may be provided on the placement unit  150 , the substrate  111 , or the like in a manner contacting the plurality of LEDs  10 . In addition, the above described air blowing mechanism may be provided on the side of the placement unit  150  so as not to contact the plurality of LEDs  10 . 
     The measuring unit  130  measures the photoelectric signal which is obtained by photoelectrically converting the light irradiated by the light source unit  120  and output via the electrical connection unit  110  by each of the plurality of LEDs  10 . The measuring unit  130  in the present embodiment measures the photoelectric signal from a set of the plurality of LEDs  10  to which the electrical connection unit  110  is sequentially connected. 
     More specifically, the measuring unit  130  in the present embodiment is connected to the electrical wiring electrically connected to each probe  113  of the electrical connection unit  110 , and measures the current value of the current output from the set of the plurality of LEDs  10  switched to contact the plurality of probes  113  among the LED group placed on the placement unit  150 . Note that the measuring unit  130  may measure a voltage value corresponding to the current value instead of the current value. 
     The measuring unit  130  according to the present embodiment further measures the intensity of light with which the position of each of the plurality of LEDs  10  is irradiated by the light source unit  120 . Note that the measuring unit  130  also functions as an example of a second measuring unit. 
     The control unit  140  controls each component of the test apparatus  100 . The control unit  140  in the present embodiment controls the light source  121  of the light source unit  120 , thereby controlling the irradiation time, wavelength, and intensity of the parallel light  122  with which the plurality of LEDs  10  are collectively irradiated. The control unit  140  according to the present embodiment also controls the placement unit  150 , thereby performing control to sequentially switch a set of the plurality of LEDs  10  to be tested from among the LED group placed on the placement unit  150 . More specifically, the control unit  140  drives the placement unit  150  so that the probe  113  comes into contact with the terminal  11  of each LED  10  of the set. Note that the control unit  140  may grasp the position coordinates in the space of the plurality of probes  113  and the relative position between each of the plurality of probes  113  and each LED  10  on the placement unit  150  by referring to the reference data in the storage unit  145 . 
     The control unit  140  further acquires a correction map including a correction value for correcting the variation in intensity of the light with which each position of the plurality of LEDs  10  is irradiated by the light source unit  120 . The control unit  140  in the present embodiment generates the correction map on the basis of the measurement result by the measuring unit  130  in advance, and stores the correction map in the storage unit  145 . In the case where the measurement results of the plurality of LEDs  10  are acquired, the control unit  140  in the present embodiment acquires the correction map from the storage unit  145 . Note that the correction map may be generated and held by an external apparatus having the same light source as the light source  121 . In this case, the control unit  140  may acquire the correction map from the external apparatus. 
     The control unit  140  further determines the quality of each of the plurality of LEDs  10  on the basis of the measurement result by the measuring unit  130  and the above described correction map. More specifically, the control unit  140  in the present embodiment corrects the measurement value of the photoelectric signal measured for each of the plurality of LEDs  10  by the measuring unit  130  using the correction value for the position of each of the plurality of LEDs  10  in the correction map. The control unit  140  according to the present embodiment further determines the quality of each of the plurality of LEDs  10  on the basis of the corrected measurement value of the photoelectric signal. 
     The control unit  140  according to the present embodiment further determines at least one LED in which the correction value obtained by correcting the measured photoelectric signal by the correction map is out of the normal range among the plurality of LEDs  10  as defective. The control unit  140  controls the sequence of these configurations by referring to the storage unit  145 . Note that the control unit  140  serves as an example of an acquisition unit, a determination unit, and a generation unit. 
     The storage unit  145  stores the above described correction map, reference data for determining the quality of each of the plurality of LEDs  10 , a determination result, reference data for moving the placement unit  150 , a sequence and a program for controlling each component in the test apparatus  100 , and the like. The storage unit  145  is referred to by the control unit  140 . 
     The LED group is placed in the placement unit  150 . The placement unit  150  in the illustrated example has a substantially circular outer shape in a plan view, but may have another outer shape. The placement unit  150  has a function of holding a vacuum chuck, an electrostatic chuck, and the like, and holds the wafer  15  of the placed LED group. The placement unit  150  moves two-dimensionally in the XY plane and moves up and down in the Z axis direction by being driven and controlled by the control unit  140 . In  FIG. 1 , illustration of the placement unit  150  on the negative direction side of the Z axis will be omitted. In addition, in  FIG. 1 , the moving direction of the placement unit  150  is indicated by a white arrow. The same applies to the following drawings. 
     The blocking unit  160  blocks light other than the light from the light source unit  120 . The surface of the blocking unit  160  in the present embodiment is entirely painted black to prevent irregular reflection of light on the surface. In addition, as illustrated in  FIG. 1 , the blocking unit  160  in the present embodiment is provided so as to be in close contact with each of the outer periphery of the light source  121  and the outer periphery of the substrate  111 , and this configuration blocks light other than the light from the light source unit  120 . 
       FIG. 2  is an example of a side view (A) and an example of a plan view (B) of the placement unit  150 , an LED group placed on the placement unit  150 , and the electrical connection unit  110  in a state where a plurality of probes  113  are in contact with a specific set of the plurality of LEDs  10  in the LED group. (A) of  FIG. 2  extracts and illustrates only the placement unit  150 , the LED group, and the electrical connection unit  110  illustrated in  FIG. 1 . In (B) of  FIG. 2 , the plurality of LEDs  10  that cannot be visually recognized due to the substrate  111  in the LED group on the placement unit  150  are indicated by broken lines. 
     As illustrated in (B) of  FIG. 2 , two terminals  11  are formed on each LED  10  so as to be separated from each other in the Y axis direction. In addition, the plurality of LEDs  10  are placed in a state of being arranged in a matrix on the placement unit  150 , and in the illustrated example, are arranged in a matrix of 6 columns in the X axis direction and 6 rows in the Y axis direction. 
     The opening  112  of the substrate  111  has a rectangular profile elongated in the Y axis direction. In the illustrated example, as a set of the plurality of LEDs  10  of which the optical characteristics are collectively measured, twelve LEDs  10  of two columns in the X axis direction and six rows in the Y axis direction are exposed in the opening  112 . One probe  113  of the electrical connection unit  110  is configured to be in contact with each of the plurality of terminals  11  located in the opening  112  of the substrate  111 . 
       FIG. 3  is an example of a plan view of the placement unit  150  and a light intensity measurement unit  170  placed on the placement unit  150 . The light intensity measurement unit  170  is disposed at the same position as the wafer  15  on the placement unit  150  when the wafer  15  holding the plurality of LEDs  10  is not placed on the placement unit  150 . In  FIG. 3 , the opening  112  and the plurality of LEDs  10  are each indicated by broken lines. 
     The measuring unit  130  in the present embodiment includes a light intensity measurement unit  170 . The light intensity measurement unit  170  in the present embodiment includes a holding unit  171  and a plurality of sensors  173 . The holding unit  171  is a substrate-shaped member and holds the plurality of sensors  173  disposed in the surface. Each of the plurality of sensors  173  may be a sensor that detects luminance and/or illuminance of a surrounding environment, such as a photodiode. Each of the plurality of sensors  173  may be set in dimension according to, for example, a ratio of the number of the plurality of sensors  173  to the number of the plurality of LEDs  10 . In the case where the ratio is 1:1, as an example, each sensor  173  may have the same dimension as the LED  10 . 
     The light intensity measurement unit  170  has a group of sensors  173  covering the same area as the plurality of LEDs  10  exposed from the substrate  111  in the opening  112 , and as an example, may have the same number of sensors  173  as the plurality of LEDs  10  exposed. Similarly to the wafer  15  illustrated in  FIG. 1  and  FIG. 2 , with the holding unit  171  placed on the placement unit  150 , each of the plurality of sensors  173  exposed in the opening  112  is disposed at the same position as each of the plurality of LEDs  10  exposed in the opening  112 . 
     Note that the light intensity measurement unit  170  may be provided in the placement unit  150  instead of the above described configuration. In this case, when the wafer  15  is not placed in the placement unit  150 , that is, when the light from the light source unit  120  is not blocked by the wafer  15 , the plurality of sensors  173  of the light intensity measurement unit  170  may receive the light. 
       FIG. 4  is an example of a flowchart for explaining a flow of a test method by the test apparatus  100 . The flow is started when, for example, a user performs an input for starting a test of the LED group with respect to the test apparatus  100  with the LED group placed on the placement unit  150 . 
     The test apparatus  100  executes an electrical connection step of electrically connecting the electrical connection unit  110  to the terminal  11  of each of the plurality of LEDs  10  to be tested (Step S 101 ). As a specific example, the control unit  140  outputs a command to the placement unit  150 , and moves the placement unit  150  such that a set of the plurality of LEDs  10  to be tested first among the LED groups on the placement unit  150  comes into contact with the plurality of probes  113 . 
     The test apparatus  100  executes an irradiation step of collectively irradiating the plurality of LEDs  10  with light (Step S 103 ). As a specific example, the control unit  140  outputs a command to the light source unit  120 , and irradiates a set of the plurality of LEDs  10  exposed in the opening  112  with the parallel light  122 . 
     The test apparatus  100  executes a measurement step of measuring the photoelectric signal which is obtained by photoelectrically converting irradiated light and output via the electrical connection unit  110  by each of the plurality of LEDs  10  (Step S 105 ). As a specific example, the control unit  140  issues a command to the measuring unit  130 , causes the measuring unit  130  to measure the current value of the current output from the set of the plurality of LEDs  10  switched to contact the plurality of probes  113  among the LED group placed on the placement unit  150 , and causes the measurement result to be output to the control unit  140 . 
     The control unit  140  stores the respective measurement results of the sets of the plurality of LEDs  10  in the storage unit  145 . 
     The test apparatus  100  determines whether the measurement of all the LEDs  10  placed on the placement unit  150  has been completed (Step S 107 ), and if not completed (Step S 107 : NO), executes a set switching step of switching a set of the plurality of LEDs  10  to be tested (Step S 109 ), and returns to Step S 101 . As a specific example, the control unit  140  refers to the reference data in the storage unit  145 , determines whether the measurement results of all the LEDs  10  placed on the placement unit  150  are stored, and if not stored, issues a command to the placement unit  150 , and then moves the placement unit  150  so as to switch to a set of the plurality of LEDs  10  to be tested. 
     In a case where the measurement of all the LEDs  10  placed on the placement unit  150  has been completed in Step S 107  (Step S 107 : YES), the test apparatus  100  executes an acquisition step of acquiring a correction map including a correction value for correcting the variation in intensity of the light with which the position of each of the plurality of LEDs is irradiated (Step S 110 ). As a specific example, the control unit  140  acquires a correction map generated in advance and stored in the storage unit  145 . 
     The test apparatus  100  executes a determination step of determining the quality of each of the plurality of LEDs  10  on the basis of the measurement result of the above described measurement step and the above described correction map (Step S 111 ), and the flow ends. As a specific example, the control unit  140  refers to the reference data in the storage unit  145 , and in a case where the measurement results of all the LEDs  10  placed on the placement unit  150  are stored, determines the quality of each of the plurality of LEDs  10  on the basis of the measurement results and the correction map. 
     The control unit  140  according to the present embodiment determines, as described above, at least one LED  10 , in which the correction value obtained by correcting the measured photoelectric signal by the correction map is out of the normal range among the plurality of LEDs  10  as defective. As an example of the normal range described herein, a range based on a statistic corresponding to a correction value obtained by correcting the photoelectric signal output by each of the plurality of LEDs  10  by the correction map may be used. 
     More specifically, as an example of the normal range, a range based on a statistic in the entire wafer  15 , that is, a statistic of the plurality of LEDs  10  of the correction value obtained by correcting the current value of the current output from each of the plurality of LEDs  10  on the placement unit  150  using the correction map may be used, or a range based on a statistic of the correction value in the entire lot including the wafer  15  may be used. As an example of the statistic, a range within the average value ±1σ, a range within the average value ±2σ, or a range within the average value ±3G of the correction value may be used. 
     In this case, the control unit  140  corrects, using the correction map, the current value of the current output from each of the plurality of LEDs  10  on the placement unit  150  stored in the storage unit  145  to calculate the correction value, and calculates the average value and the standard deviation σ on the basis of the correction value. In a case where there are a plurality of peaks in the correction value, the statistic of the correction values may be calculated using statistical processing capable of corresponding to the plurality of peaks without using the standard deviation. 
     As another example of the above described normal range, a range based on a statistic corresponding to a correction value obtained by correcting the photoelectric signals output by the LEDs  10  disposed at the same position among sets of the plurality of LEDs  10  by the correction map in the measurement results obtained by performing a plurality of measurements by the measuring unit  130  while sequentially changing the set of the plurality of LEDs  10  to be tested from the LED group may be used. More specifically, as an example of the normal range, for example, a range within an average value ±1σ, a range within the average value ±2σ, or a range within the average value ±3σ of the correction values obtained by correcting, with the LEDs  10  disposed in the same row and the same column, among the LED groups arranged in a matrix of 6 columns in the X axis direction and 6 rows in the Y axis direction on the placement unit  150  illustrated in  FIG. 2 , as target LEDs, the current value of the current output from the target LED in each of the plurality of LED groups on the plurality of placement units  150  using the correction map may be used. In this case, the control unit  140  corrects the current values of the currents output from the plurality of target LEDs stored in the storage unit  145  using the correction map to calculate the correction value, and calculates the average value and the standard deviation σ on the basis of the correction value. 
     As another example of the above described normal range, a range obtained by adding a margin determined on the basis of the specification of the LED  10  to a reference value determined on the basis of the specification of the LED  10  may be used. In this case, the control unit  140  may refer to information indicating the range stored in advance in the storage unit  145 . 
       FIG. 5  is an example of a flowchart for explaining a flow of generating a correction map and calculating a corrected measurement value of the photoelectric signal of each LED  10  by the test apparatus  100 . The flow is started when, for example, a user performs an input for starting the flow with respect to the test apparatus  100  with the light intensity measurement unit  170  disposed on the placement unit  150 . 
     The test apparatus  100  collectively irradiates a set of the plurality of sensors  173  exposed in the opening  112  with light by the light source  121 , and measures the luminance amount of each sensor  173  (Step S 201 ). The test apparatus  100  quantifies the measured luminance amount and stores the quantified luminance amount in the storage unit  145  as data of the correction map as illustrated in  FIG. 5  (Step S 203 ). 
     The test apparatus  100  drives the placement unit  150  as indicated by a black arrow in  FIG. 5  to move the wafer  15  in parallel, and collectively irradiates a set of the plurality of LEDs  10  exposed in the opening  112  with light by the same light source  121 , and measures the photoelectric signal which is obtained by photoelectrically converting the light and output by each LED  10  (Step S 205 ). The test apparatus  100  acquires the correction map from the storage unit  145 , and applies the correction map to the measurement value of the photoelectric signal of each LED  10  for each set of the plurality of LEDs  10  (Step S 207 ). The test apparatus  100  calculates the corrected measurement value of the photoelectric signal of each LED  10  (Step S 209 ), and ends the flow. 
     Note that Step S 205  in the flow corresponds to Steps S 101  to S 109  in the flow illustrated in  FIG. 4 , and Steps S 207  and S 209  in the flow correspond to Steps S 110  and S 111  in the flow illustrated in  FIG. 4 . The corrected measurement value calculated in the flow is used in the determination in Step S 111  illustrated in  FIG. 4 . 
       FIG. 6  is an example of a flowchart for explaining a flow of calculating a correction value for calibrating the measurement values of the plurality of sensors  173  of the light intensity measurement unit  170  by the test apparatus  100 . The flow is started when, for example, the user performs an input for starting the flow with respect to the test apparatus  100  with the light source  121  of the light source unit  120  replaced with a surface light source of which the uniformity has been calibrated, and the light intensity measurement unit  170  disposed on the placement unit  150  for example. 
     The control unit  140  in the present embodiment may additionally calibrate the measurement values by the plurality of sensors  173  of the light intensity measurement unit  170  by the surface light source of which the uniformity has been calibrated. The test apparatus  100  collectively irradiates a set of the plurality of sensors  173  exposed in the opening  112  with light by the surface light source of which the uniformity has been calibrated, and measures the luminance amount of each sensor  173  (Step S 251 ). The test apparatus  100  quantifies the measured luminance amount and stores the quantified luminance amount in the storage unit  145  as a correction value for calibrating the measurement values by the plurality of sensors  173  measured for the correction map (Step S 253 ), and the flow ends. 
     As a comparative example with the test method by the test apparatus  100  of the present embodiment, for example, a test method of optical characteristics of LEDs is conceivable, in which a plurality of LEDs arranged on a wafer are sequentially turned on one by one, and light is received by an image sensor, a spectral luminance meter, or the like to determine whether the light is correctly emitted. 
     In a case where the optical characteristics of the plurality of LEDs described above are collectively measured using the test method of the comparative example, light irradiated from each of the plurality of adjacent LEDs interferes with each other, and a defective LED having a relatively deteriorated optical characteristic cannot be correctly identified. In addition, an image sensor or the like becomes very expensive for performing image recognition in a wide range with high accuracy. In particular, in a case where a plurality of micro LEDs are tested, the problem becomes remarkable. 
     On the other hand, according to the test apparatus  100  of the present embodiment, the electrical connection unit  110  is electrically connected to the terminal  11  of each of the plurality of LEDs  10  to be tested, the plurality of LEDs  10  are collectively irradiated with light, a photoelectric signal is measured which is obtained by photoelectrically converting irradiated light, and output via the electrical connection unit  110  by each of the plurality of LEDs  10 . Further, according to the test apparatus  100 , the quality of each of the plurality of LEDs  10  is determined on the basis of the measurement results of the plurality of LEDs  10 . As a result, the test apparatus  100  can not only shorten the processing time by simultaneously measuring the photoelectric signals of the plurality of LEDs  10 , but also can correctly identify a defective LED  10  having deteriorated optical characteristics by determining the quality of the LED  10  using the photoelectric signals measured without being affected by the measurement of the optical characteristics of the other LEDs  10 . In addition, according to the test apparatus  100 , the number of LEDs  10  to be simultaneously measured can be easily expanded. 
     In a case where the photoelectric signal output by collectively irradiating the plurality of LEDs with the light from the light source is measured, the outside of the irradiation region of the light with which the plurality of LEDs are irradiated from the light source may be darker than the center side, or the intensity of light may vary depending on the position in the irradiation region. On the other hand, according to the test apparatus  100  of the present embodiment, the quality of each of the plurality of LEDs  10  is determined on the basis of the measurement value of the photoelectric signal output by each of the plurality of LEDs  10  and the correction map including the correction value for correcting the variation in intensity of the light with which the position of each of the plurality of LEDs  10  is irradiated by the light source unit  120 . As a result, the test apparatus  100  can correct the variation in intensity of the light with which the position of each of the plurality of LEDs  10  is irradiated by the light source unit  120 , and can enhance the measurement accuracy of the optical characteristics of the plurality of LEDs  10 . 
     According to the test apparatus  100  of the present embodiment, the plurality of probes  113  and the substrate  111  used for measuring the optical characteristics of the plurality of LEDs  10  can also be shared for measurement of the electrical characteristics of the plurality of LEDs  10 , for example, a VI test using an LED tester. 
     According to the test apparatus  100  of the present embodiment, for the other configurations except for the light source unit  120  and the blocking unit  160 , that is, for the electrical connection unit  110 , the measuring unit  130 , the control unit  140 , the storage unit  145 , and the placement unit  150 , those used for testing devices other than optical devices such as the LED group can be used. 
     In the above embodiment, the plurality of LEDs  10  have been described as a configuration in which the terminals  11  are on the light emitting surface side. Alternatively, the plurality of LEDs  10  may have terminals  11  on the opposite side of the light emitting surface. The plurality of probes  113  may have different lengths depending on whether each terminal  11  of the plurality of LEDs  10  is located on the light emitting surface side or on the opposite side of the light emitting surface. 
     In the above embodiment, the configuration has been described in which the placement unit  150  on which the LED group is placed is moved so that the position coordinates of the plurality of probes  113  of the electrical connection unit  110  and the position coordinates of the plurality of LEDs  10  of the LED group coincide with each other in the XY plane, and then the placement unit  150  is moved up and down to bring the plurality of terminals  11  of the plurality of LEDs  10  into contact with the plurality of probes  113 . Alternatively, the plurality of terminals  11  of the plurality of LEDs  10  may be brought into contact with the plurality of probes  113  by moving the substrate  111  up and down after the movement in the above described XY plane. 
     In the above embodiment, the placement unit  150  has been described as having a substantially circular outer shape. Alternatively, for example, in a case where an LED group in which a plurality of LEDs  10  are formed is placed on a glass-based panel (PLP) having a substantially rectangular outer shape in which electric wiring are formed, the placement unit  150  may have a substantially rectangular outer shape in correspondence with the outer shape of the LED group. 
       FIG. 7  is an example of an overall view illustrating an outline of a test apparatus  200  for testing a plurality of LEDs  20 . In the description of the embodiment illustrated in  FIG. 7 , the same configurations as those of the embodiment described with reference to  FIG. 1  to  FIG. 6  are denoted by the corresponding reference numerals, and redundant description will be omitted. However, in  FIG. 7 , the measuring unit  130 , the control unit  140 , the storage unit  145 , and the placement unit  150  of the test apparatus  100  described with reference to  FIG. 1  to  FIG. 6  will be not illustrated for the purpose of simply clarifying the description. The same applies to the drawings of the embodiments described below, and redundant description will be omitted. 
     In the embodiment described with reference to  FIG. 1  to  FIG. 6 , the electrical connection unit  110  has been described as a configuration in which the electrical connection unit  110  is disposed between the light source unit  120  and the plurality of LEDs  10 , and includes the substrate  111  and the plurality of probes  113  provided in the opening  112  of the substrate  111 . In the embodiment illustrated in  FIG. 7  and subsequent drawings, instead, an electrical connection unit  210  is disposed such that the plurality of LEDs  20  and  30  are located between the light source unit  120  and the electrical connection unit  210 , and has a substrate  211  and a plurality of probes  213  extending from the substrate  211  toward each of the plurality of LEDs  20  and  30  and contacting terminals  21  and  31  of each of the plurality of LEDs  20  and  30 . 
     In the embodiment illustrated in  FIG. 7 , the LED group is a surface emitting type in which the light emitting surfaces of the plurality of LEDs  20  do not face a wafer  25 , each terminal  21  of the plurality of LEDs  20  faces the wafer  25 , and the wafer  25  is formed with a plurality of vias  26  extending in the Z axis direction at the position of each terminal  21 . In such a case, the electrical connection unit  210  may bring the plurality of probes  213  into contact with the respective terminals  21  of the plurality of LEDs  20  from the negative direction side of the Z axis of the wafer  25  through the plurality of vias  26  formed in the wafer  25 . 
     In the electrical connection unit  210  of the embodiment illustrated in  FIG. 7 , the substrate  211  may not have the opening  112  of the electrical connection unit  110  in the embodiment described with reference to  FIG. 1  to  FIG. 6 , and the plurality of probes  213  may not extend in the XY plane. As illustrated in  FIG. 7 , the plurality of probes  213  may extend in the Z axis direction toward the terminals  21  of each LED  20  so as to form a mountain shape together with the substrate  211 . The same applies to the embodiments described below, and redundant description will be omitted. 
       FIG. 8  is an example of a plan view of the placement unit  150  and the light intensity measurement unit  175  placed on the placement unit  150 . The measuring unit  130  according to the present embodiment includes the light intensity measurement unit  175  instead of the light intensity measurement unit  170  in the embodiment described with reference to  FIG. 1  to  FIG. 6 . The light intensity measurement unit  175  has the same number of sensors  173  as the number of the plurality of LEDs  20 , and each of the plurality of sensors  173  is disposed at the same position as the position of each of the plurality of LEDs  20 . Note that the light intensity measurement unit  175  may include a two-dimensional luminance meter for collectively measuring the intensity of light with which the position of each of the plurality of LEDs  20  instead of the sensors  173  having the same number as the plurality of LEDs  20  is irradiated. 
       FIG. 9  is an example of a flowchart for explaining a flow of a test method by the test apparatus  200 . The test apparatus  200  according to the present embodiment functions similarly to the test apparatus  100  according to the embodiment described with reference to  FIG. 1  to  FIG. 6 , and executes Steps S 101 , S 103 , S 105 , S 110 , and S 111  of the flow illustrated in  FIG. 4 . However, unlike the test apparatus  100  according to the embodiment described with reference to  FIG. 1  to  FIG. 6 , the test apparatus  200  according to the present embodiment does not execute Steps S 107  and S 109  of the flow illustrated in  FIG. 4 . 
       FIG. 10  is an example of a flowchart for explaining a flow of generating the correction map and calculating the corrected measurement value of the photoelectric signal of each LED  20  by the test apparatus  200 . Similarly to the flow illustrated in  FIG. 5 , the flow is started when, for example, the user performs an input for starting the flow with respect to the test apparatus  200  with the light intensity measurement unit  175  disposed on the placement unit  150 . 
     The test apparatus  200  collectively irradiates the plurality of sensors  173  with light by the light source  121 , and measures the luminance amount of each sensor  173  (Step S 301 ). The test apparatus  200  quantifies the measured luminance amount and stores the quantified luminance amount in the storage unit  145  as data of the correction map as illustrated in  FIG. 10  (Step S 303 ). 
     The test apparatus  200  collectively irradiates the plurality of LEDs  20  with light by the same light source  121 , and measures a photoelectric signal which is obtained by photoelectrically converting the light and output by each LED  20  (Step S 305 ). The test apparatus  200  acquires the correction map from the storage unit  145 , and applies the correction map to the measurement value of the photoelectric signal of each LED  20  (Step S 307 ). The test apparatus  200  calculates the corrected measurement value of the photoelectric signal of each LED  20  (Step S 309 ), and ends the flow. 
     Note that Step S 305  in the flow corresponds to Steps S 101  to S 105  in the flow illustrated in  FIG. 9 , and Steps S 307  and S 309  in the flow correspond to Steps S 110  to S 111  in the flow illustrated in  FIG. 9 . The corrected measurement value calculated in the flow is used in the determination in Step S 111  illustrated in  FIG. 9 . 
       FIG. 11  is another example of a flowchart for explaining a flow of generating the correction map and calculating the corrected measurement value of the photoelectric signal of each LED  20  by the test apparatus  200 . The measuring unit  130  according to the present embodiment includes a light intensity measurement unit  176  instead of the light intensity measurement unit  175  in the embodiment described with reference to  FIG. 10 . 
     The measuring unit  130  according to the present embodiment measures the intensity of light with which the positions of several LEDs  20  are irradiated, which is a part of the light with which the position of each of the plurality of LEDs  20  is irradiated by the light source unit  120 . The light intensity measurement unit  176  of the measuring unit  130  according to the present embodiment has a smaller number of sensors  173  than the plurality of LEDs  20 , and the plurality of sensors  173  each are disposed at the positions of the several LEDs  20  described above. The plurality of sensors  173  are separated from each other by a predetermined interval, for example, as illustrated in  FIG. 11 . The light intensity measurement unit  176  can reduce the number of sensors  173  as compared with the light intensity measurement unit  175 . Note that the arrangement of the plurality of sensors  173  illustrated in  FIG. 11  is merely an example, and other arrangements may be adopted. 
     Note that the light intensity measurement unit  176  may include a two-dimensional luminance meter for collectively measuring the intensity of light with which the positions of several LEDs  20  are irradiated instead of the smaller number of sensors  173  than the plurality of LEDs  20 . The number of pixels of the two-dimensional luminance meter may be smaller than the number of pixels of another two-dimensional luminance meter for collectively measuring the intensity of light with which the position of each of the plurality of LEDs  20  is irradiated. 
     Similarly to the flow illustrated in  FIG. 10 , the flow illustrated in  FIG. 11  is started when, for example, the user performs an input for starting the flow with respect to the test apparatus  200  with the light intensity measurement unit  176  disposed on the placement unit  150 . 
     The test apparatus  200  collectively irradiates the plurality of sensors  173  with light by the light source  121 , and measures the luminance amount of each sensor  173  (Step S 401 ). 
     The control unit  140  in the present embodiment interpolates the intensities of the lights with which the positions of the rest LEDs  20  other than the several LEDs  20  described above are irradiated among the plurality of LEDs  20  on the basis of the measurement results of the plurality of sensors  173  by the measuring unit  130 , and generates the correction map. Specifically, the test apparatus  200  quantifies the luminance amount measured in Step S 401 , calculates a correction coefficient from the quantified data, and interpolates the numerical values at the positions where the sensor  173  is not disposed with respect to the plurality of LEDs  20  using the correction coefficient. The test apparatus  200  stores the interpolated data in the storage unit  145  as a correction map (Step S 403 ), and proceeds to Step S 305  of the flow illustrated in  FIG. 10 . 
       FIG. 12  is still another example of a flowchart illustrating a flow of generating the correction map and calculating the corrected measurement value of the photoelectric signal of each LED  20  by the test apparatus  200 . The measuring unit  130  according to the present embodiment includes a light intensity measurement unit  177  instead of the light intensity measurement unit  176  in the embodiment described with reference to  FIG. 11 . 
     The light intensity measurement unit  177  of the measuring unit  130  according to the present embodiment sequentially measures the intensity of the light with which the position of each of the plurality of LEDs  20  is irradiated by the light source unit  120  by sequentially moving the position of each of the plurality of LEDs  20 . The light intensity measurement unit  177  has one sensor  173 , and the sensor  173  is movable on the surface of the holding unit  171 . The light intensity measurement unit  177  can further reduce the number of sensors  173  as compared with the light intensity measurement units  175  and  176 , and the like. Note that the movement path of the sensor  173  indicated by an arrow in  FIG. 12  is merely an example, and may be another movement path. 
     Similarly to the flow illustrated in  FIG. 11 , the flow illustrated in  FIG. 12  is started when, for example, the user performs an input for starting the flow with respect to the test apparatus  200  with the light intensity measurement unit  177  disposed on the placement unit  150 . 
     The test apparatus  200  irradiates the sensor  173  sequentially moving in the position of each of the plurality of LEDs  20  with light by the light source  121 , measures the luminance amount of the sensor  173  at each position (Step S 501 ), and proceeds to Step S 303  of the flow illustrated in  FIG. 10 . 
     The test apparatus  200  according to the embodiment described above has the same effect as the test apparatus  100  according to the embodiment described with reference to  FIG. 1  to  FIG. 6 . Since the test apparatus  200  includes the electrical connection unit  210  having a configuration in which the plurality of probes  213  extend in the Z axis direction from one surface of the substrate  211  having no opening toward the terminal  21  of each LED  20 , the number of probes  213  can be increased and the number of LEDs  20  to be measured at the same time can be increased as compared with the case of using the electrical connection unit  110  having the plurality of probes  113  extending toward the terminal  11  of the LED  20  exposed in the opening  112  of the substrate  111  according to the embodiment described with reference to  FIG. 1  to  FIG. 6 . 
     Note that, in the present embodiment, the placement unit  150  on which the LED group is placed is moved so that the position coordinates of the plurality of probes  113  of the electrical connection unit  110  and the position coordinates of the plurality of LEDs  20  of the LED group coincide with each other in the XY plane, and then the substrate  211  of the electrical connection unit  210  is moved up and down as indicated by a white arrow in each drawing, whereby the plurality of terminals  21  of the plurality of LEDs  20  may be brought into contact with the plurality of probes  213 . 
     In the present embodiment, the configuration illustrated in  FIG. 7  may be reversed in the Z axis direction, and thus the plurality of LEDs  20  may be irradiated, from the negative direction of the Z axis, with the parallel light  122  from the light source unit  120 . 
     In the present embodiment, in order to prevent the wafer  25  from being deformed by the pressing of the electrical connection unit  210  by the plurality of probes  213 , a support plate that transmits light, such as glass, may be interposed between the wafer  25  and the blocking unit  160 . In a case where the plurality of LEDs  20  are located on the light source unit  120  side as illustrated in  FIG. 7 , it is preferable that the support plate is configured not to contact the plurality of LEDs  20  so as not to destroy the plurality of LEDs  20  formed on the wafer  25 . Any of the points described above is similar in a plurality of embodiments described below, and redundant description will be omitted. 
     Note that, in the test apparatuses  100  and  200  according to the above embodiments, the description has been given that the control unit  140  is configured to generate the correction map using the holding unit  171  that holds one or more sensors  173  or the luminance meter instead of the wafers  15  and  25  that hold the plurality of LEDs  10  and  20 . Alternatively, the control unit  140  may generate the correction map on the basis of an average value of the photoelectric signals output by the LEDs  10  and  20  disposed at the same position between the sets of the plurality of LEDs  10  and  20  in the measurement results obtained by performing a plurality of measurements by the measuring unit  130  while sequentially changing the set of the plurality of LEDs  10  and  20  to be tested from the LED group. 
     For example, when the number of wafers  15  and  25  to be tested is, for example, 30, the photoelectric signals of 30 wafers  15  and  25  may be measured, an average value of the photoelectric signals output by the LEDs  10  and  20  disposed at the same position between the sets of the plurality of LEDs  10  and  20  may be calculated, and the above described correction map may be generated on the basis of the average value. 
     As a result, the test apparatuses  100  and  200  can omit the configuration of the light intensity measurement unit  170  and the like. 
     In this case, among the measurement values of the photoelectric signals output by the LEDs  10  and  20  disposed at the same position between the sets of the plurality of LEDs  10  and  20 , for example, the measurement values that are significantly abnormal compared to the others, such as the measurement values of the photoelectric signals output by the defective LEDs  10  and  20 , may be excluded. For the exclusion, a predetermined threshold value for the measurement value may be used. As a result, the calculation accuracy of the average value described above can be enhanced. 
       FIG. 13  is another example of a flowchart for explaining the flow of the test method by the test apparatus  200 . The control unit  140  of the test apparatus  200  according to the present embodiment additionally or alternatively changes the intensity of the light irradiated by the light source unit  120 , and determines the quality of each of the plurality of LEDs  20  on the basis of the measurement result by the measuring unit  130  in a case where the intensity is changed. In other words, the control unit  140  changes the intensity of the light irradiated by the light source unit  120 , and determines the response of each LED  20  to the change in the intensity of the light. Note that the control unit  140  according to the present embodiment functions as an example of a light source control unit. 
     The LED  20  emits stronger light as the current value to be applied is higher, but there is an individual difference, and when the current value is low, characteristics cannot be fully exhibited, that is, light cannot be appropriately emitted in some cases. Therefore, in the case of causing the LED  20  to perform photoelectric conversion, it can be regarded that the LED  20  is capable of appropriately emitting light even at a low current value as long as an appropriate reaction, that is, an appropriate photoelectric signal is output even when the LED  20  is irradiated with weak light. 
     Similarly to the flow illustrated in  FIG. 4 , the flow illustrated in  FIG. 13  is started when, for example, the user performs an input for starting the test of the LED group with respect to the test apparatus  200  with the LED group placed on the placement unit  150 . The test apparatus  200  executes Steps S 101 , S 103 , and S 105  corresponding to Steps S 121 , S 123 , and S 125  in the flow illustrated in  FIG. 4 . 
     The test apparatus  200  determines whether the measurement result necessary for determining the quality of each of the plurality of LEDs  20  on the wafer  25  is obtained by changing the intensity of light (Step S 127 ), and if not obtained (Step S 127 : NO), the light source control step of changing the intensity of the light irradiated in the irradiation step of Step S 123  is executed (Step S 129 ), and the process returns to Step S 123 . As a specific example, the control unit  140  may refer to the reference data in the storage unit  145  and determine whether a measurement result in a case where the plurality of LEDs  20  are irradiated with light having an intensity equal to or higher than a predetermined threshold value and a measurement result in a case where the plurality of LEDs  20  are irradiated with light having an intensity equal to or lower than the predetermined threshold value are stored. In a case where at least one of these measurement results is not stored in the storage unit  145 , the control unit  140  changes the intensity of light irradiated from the light source unit  120  and irradiates the plurality of LEDs  20  with light again. 
     In a case where the measurement result necessary for determining the quality of each of the plurality of LEDs  20  on the wafer  25  is obtained in Step S 127  (Step S 127 : YES), the test apparatus  200  executes the determination step of determining the quality of each of the plurality of LEDs  20  on the basis of the measurement result of the measurement step in a case where the intensity is changed in the light source control step of Step S 129  (Step S 131 ), and the flow ends. 
     The test apparatus  200  according to the embodiment described above has the same effects as the test apparatuses  100  and  200  according to the plurality of embodiments described with reference to  FIG. 1  to  FIG. 12 . For example, the control unit  140  in the present embodiment may calculate a photoelectric gain of each of the plurality of LEDs  20  on the basis of the measurement result of each of two or more different intensities. In this case, control unit  140  may determine that at least one LED  20  of which the photoelectric gain is out of the normal range among the plurality of LEDs  20  is defective. More specifically, the control unit  140  may determine that at least one LED  20  of which the photoelectric gain is out of the normal range at any of two or more different intensities is defective. 
     For example, the control unit  140  in the present embodiment may determine that at least one LED  20  in which the photoelectric signal measured at each of two or more different intensities among the plurality of LEDs  20  is out of the normal range is defective. More specifically, the control unit  140  may determine that at least one LED  20  in which the photoelectric signal is out of the normal range at any of two or more different intensities is defective. 
       FIG. 14  is still another example of a flowchart for explaining the flow of the test method by the test apparatus  200 . Additionally or alternatively, the control unit  140  of the test apparatus  200  according to the present embodiment changes the wavelength of the light irradiated by the light source unit  120  within a predetermined range including a predetermined reaction wavelength of the plurality of LEDs  20 , and determines the quality of each of the plurality of LEDs  20  on the basis of the measurement result by the measuring unit  130  in a case where the wavelength is changed. In other words, the control unit  140  changes the wavelength of the light irradiated by the light source unit  120  within a predetermined range including a predetermined reaction wavelength of the plurality of LEDs  20 , and determines the reaction of each LED  20  to the wavelength change of the light. 
     In the LED  10  in which the light emission wavelength is shifted to be defective, the peak of the reaction to the light from the light source  121  is also shifted. Therefore, the test apparatus  200  additionally has a function of shifting the wavelength of the light irradiated by the light source  121 , that is, a wavelength selection function. As a specific example, in a case where the light source  121  is a light source having a wide wavelength band, for example, a xenon light source, the test apparatus  200  may have a configuration in which a spectroscope using, for example, a slit is installed on the light output side (front end) of the light source  121  to spectrally separate light from the light source  121  and transmit only light having a specific wavelength. As another example, in a case where the light source  121  is a laser light source having a narrow wavelength band, the test apparatus  200  may include a diffraction grating or the like at the front end of the light source  121 . As another example, the light source  121  may include a plurality of laser light sources having a narrow wavelength band. 
     The control unit  140  sweeps the wavelength of the light from the light source  121 , for example, in one nanostep from 350 nm to 400 nm, and determines which wavelength each LED  10  reacts with, thereby determining the light emission wavelength of each LED  10 . 
     Similarly to the flow illustrated in  FIG. 4 , the flow illustrated in  FIG. 14  is started when, for example, the user performs an input for starting the test of the LED group with respect to the test apparatus  200  with the LED group placed on the placement unit  150 . The test apparatus  200  executes Steps S 101 , S 103 , and S 105  corresponding to Steps S 141 , S 143 , and S 145  in the flow illustrated in  FIG. 4 . 
     The test apparatus  200  changes the wavelength of the light within a predetermined range including a predetermined reaction wavelength of the plurality of LEDs  20 , determines whether a measurement result necessary for determining the quality of each of the plurality of LEDs  20  on the wafer  25  is obtained (Step S 147 ), and if not obtained (Step S 147 : NO), executes the light source control step of changing the wavelength of the light irradiated in the irradiation step of Step S 143  within a predetermined range including a predetermined reaction wavelength of the plurality of LEDs  20  (Step S 149 ), and returns to Step S 143 . As a specific example, the control unit  140  may refer to the reference data in the storage unit  145  and determine whether measurement results in a case where the plurality of LEDs  20  are irradiated with light of a predetermined number of different wavelengths centered on design reaction wavelengths of the plurality of LEDs  20  are stored. In a case where the measurement result based on the light having the predetermined number or more of different wavelengths is not stored in the storage unit  145 , the control unit  140  shifts the wavelength of the light irradiated from the light source unit  120  by, for example, a predetermined wavelength width, and irradiates the plurality of LEDs  20  with light again. 
     In a case where the measurement result necessary for determining the quality of each of the plurality of LEDs  20  on the wafer  25  is obtained in Step S 147  (Step S 147 : YES), the test apparatus  200  executes the determination step of determining the quality of each of the plurality of LEDs  20  on the basis of the measurement result of the measurement step in a case where the wavelength is changed in the light source control step of Step S 149  (Step S 151 ), and the flow ends. 
     The test apparatus  200  according to the embodiment described above has the same effects as the test apparatuses  100  and  200  according to the plurality of embodiments described with reference to  FIG. 1  to  FIG. 13 . For example, the control unit  140  in the present embodiment may calculate the photoelectric gain of each of the plurality of LEDs  20  on the basis of the measurement result at each of two or more different wavelengths. In this case, control unit  140  may determine that at least one LED  20  of which the photoelectric gain is out of the normal range among the plurality of LEDs  20  is defective. More specifically, the control unit  140  may determine that at least one LED  20  of which the photoelectric gain is out of the normal range at any of two or more different wavelengths is defective. 
     For example, the control unit  140  in the present embodiment may determine that at least one LED  20  in which the photoelectric signal measured at each of two or more different wavelengths among the plurality of LEDs  20  is out of the normal range is defective. More specifically, the control unit  140  may determine that at least one LED  20  in which the photoelectric signal is out of the normal range at any of two or more different wavelengths is defective. 
       FIG. 15  is an example of an overall view illustrating an outline of a test apparatus  300  for testing a plurality of LEDs  30 . Unlike the test apparatuses  100  and  200 , the test apparatus  300  has a posture in which the entire test apparatus  200  is inverted in the Z axis direction. In the embodiment illustrated in  FIG. 15 , the LED group is a back-side emission type in which the light emitting surfaces of the plurality of LEDs  30  face a wafer  35 , and the wafer  35  transmits light. Each terminal  31  of the plurality of LEDs  30  does not face the wafer  35 . Note that, in the LED group of a back-side emission type as in the present embodiment, the plurality of LEDs  30  and the wafer  35  on which the plurality of LEDs  30  are mounted may be collectively referred to as a wafer. 
     In such a configuration, the electrical connection unit  210  brings the plurality of probes  213  into contact with the respective terminals  31  of the plurality of LEDs  30  from the positive direction side of the Z axis of the wafer  35 . In the embodiment illustrated in  FIG. 15 , unlike the placement unit  150 , the placement unit  155  has a light transmission unit  156  at the center of the XY plane so as not to block the light irradiated by the plurality of LEDs  30  and transmitted through the wafer  35 , and holds the wafer  35  around the light transmission unit  156 . As an example, the light transmission unit  156  may be a simple through hole, or may have a configuration in which a member that transmits light such as glass is fitted in the through hole. The test apparatus  300  of the embodiment illustrated in  FIG. 15  has the same effect as the test apparatuses  100  and  200  of the plurality of embodiments described with reference to  FIG. 1  to  FIG. 14 . 
     In the plurality of embodiments described above, in a case where the LED group has a configuration in which the plurality of LEDs are formed on a glass-based panel (PLP) having a substantially rectangular outer shape on which electric wirings are formed, the electrical connection unit may have a configuration in which the probes are brought into contact with the respective wirings in the row direction and the column direction arranged on the two side surfaces of the panel. 
     Various embodiments of the present invention may also be described with reference to flowcharts and block diagrams, where the blocks may represent (1) a step of processing in which an operation is executed or (2) a section of an apparatus that is responsible for executing the operation. Certain steps and sections may be implemented by dedicated circuitry, programmable circuitry provided with computer readable instructions stored on a computer readable medium, and/or a processor provided with computer readable instructions stored on a computer readable medium. The dedicated circuitry may include digital and/or analog hardware circuits, and may include integrated circuits (ICs) and/or discrete circuits. The programmable circuitry may include reconfigurable hardware circuits including memory elements such as logic AND, logic OR, logic XOR, logic NAND, logic NOR, and other logic operations, flip-flops, registers, field programmable gate arrays (FPGA), programmable logic arrays (PLA), and the like. 
     The computer readable medium may include any tangible device capable of storing instructions to be executed by a suitable device, so that the computer readable medium having the instructions stored therein will have a product including instructions that can be executed to create means for executing the operations specified in flowcharts or block diagrams. Examples of the computer readable medium may include an electronic storage medium, a magnetic storage medium, an optical storage medium, an electromagnetic storage medium, a semiconductor storage medium, and the like. More specific examples of the computer readable medium may include a floppy (registered trademark) disk, a diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an electrically erasable programmable read-only memory (EEPROM), a static random access memory (SRAM), a compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a Blu-ray (registered trademark) disk, a memory stick, an integrated circuit card, and the like. 
     The computer readable instructions may include source code or object code written in any combination of one or more programming languages, including assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, or an object oriented programming language such as Smalltalk (registered trademark), JAVA (registered trademark), C++, or the like, and conventional procedural programming languages such as the “C” programming language or similar programming languages. 
     The computer readable instructions may be provided for a processor or programmable circuitry of a general purpose computer, special purpose computer, or other programmable data processing apparatuses locally or via a wide area network (WAN) such as a local area network (LAN), the Internet, or the like, and execute the computer readable instructions to create means for executing the operations specified in flowcharts or block diagrams. Examples of the processor include a computer processor, a processing unit, a microprocessor, a digital signal processor, a controller, a microcontroller, and the like. 
       FIG. 16  illustrates an example of a computer  1200  in which a plurality of aspects of the present invention may be embodied in whole or in part. A program installed in the computer  1200  can cause the computer  1200  to function as an operation associated with the apparatus according to the embodiment of the present invention or one or more “units” of the apparatus, or execute the operation or the one or more “units”, and/or cause the computer  1200  to execute a process according to the embodiment of the present invention or a step of the processing. Such programs may be executed by a CPU  1212  to cause the computer  1200  to execute certain operations associated with some or all of the blocks in the flowcharts and block diagrams described in the present specification. 
     The computer  1200  according to the present embodiment includes the CPU  1212 , a RAM  1214 , a graphics controller  1216 , and a display device  1218 , which are interconnected by a host controller  1210 . The computer  1200  also includes input/output units such as a communication interface  1222 , a hard disk drive  1224 , a DVD-ROM drive  1226 , and an IC card drive, which are connected to the host controller  1210  via an input/output controller  1220 . The computer also includes legacy input/output units such as a ROM  1230  and a keyboard  1242 , which are connected to the input/output controller  1220  via an input/output chip  1240 . 
     The CPU  1212  operates according to programs stored in the ROM  1230  and the RAM  1214 , thereby controlling each unit. The graphics controller  1216  acquires image data generated by the CPU  1212  in a frame buffer or the like provided in the RAM  1214  or in the graphics controller  1216  itself, such that the image data is displayed on the display device  1218 . 
     The communications interface  1222  communicates with other electronic devices via a network. The hard disk drive  1224  stores programs and data used by the CPU  1212  in the computer  1200 . The DVD-ROM drive  1226  reads program or data from the DVD-ROM  1201  and provides the programs or data to the hard disk drive  1224  via the RAM  1214 . The IC card drive reads programs and data from the IC card and/or writes the programs and data to the IC card. 
     The ROM  1230  stores a boot program and the like, therein, executed by the computer  1200  at the time of activation and/or a program depending on hardware of the computer  1200 . The input/output chip  1240  may also connect various input/output units to the input/output controller  1220  via a parallel port, a serial port, a keyboard port, a mouse port, or the like. 
     The program is provided by a computer-readable storage medium such as a DVD-ROM  1201  or an IC card. The program is read from a computer-readable storage medium, installed in the hard disk drive  1224 , the RAM  1214 , or the ROM  1230  that are also examples of the computer-readable storage medium, and executed by the CPU  1212 . The information processing described in these programs is read by the computer  1200  and provides cooperation between the programs and various types of hardware resources described above. The apparatus or method may be configured by implementing operation or processing of information according to the use of the computer  1200 . 
     For example, in a case where communication is executed between the computer  1200  and an external device, the CPU  1212  may perform a communication program loaded in the RAM  1214  and instruct the communication interface  1222  to execute communication processing on the basis of a process described in the communication program. Under the control of the CPU  1212 , the communication interface  1222  reads transmission data stored in a transmission buffer area provided in a recording medium such as the RAM  1214 , the hard disk drive  1224 , the DVD-ROM  1201 , or the IC card, transmits the read transmission data to the network, or writes reception data received from the network in a reception buffer area or the like provided on the recording medium. 
     In addition, the CPU  1212  may cause the RAM  1214  to read all or a necessary part of a file or database stored in an external recording medium such as the hard disk drive  1224 , the DVD-ROM drive  1226  (DVD-ROM  1201 ), the IC card, or the like, and may execute various types of processing on data on the RAM  1214 . 
     Next, the CPU  1212  may write back the processed data to the external recording medium. 
     Various types of information such as various types of programs, data, tables, and databases may be stored in a recording medium in order to be subjected to information processing. The CPU  1212  may execute various types of processing on the data read from the RAM  1214 , including various types of operations, information processing, conditional determination, conditional branching, unconditional branching, information retrieval/replacement, and the like, which are described throughout the present disclosure and specified by a command sequence of a program, and writes back the results to the RAM  1214 . Further, the CPU  1212  may retrieve information in a file, a database, or the like in the recording medium. For example, in a case where a plurality of entries each having the attribute value of a first attribute associated with the attribute value of a second attribute is stored in the recording medium, the CPU  1212  may retrieve an entry matching the condition in which the attribute value of the first attribute is specified from among the plurality of entries, read the attribute value of the second attribute stored in the entry, and thereby acquire the attribute value of the second attribute associated with the first attribute satisfying the predetermined condition. 
     The programs or software modules according to the above description may be stored in a computer-readable storage medium on or near the computer  1200 . In addition, a recording medium such as a hard disk or a RAM provided in a server system connected to a dedicated communication network or the Internet can be used as a computer-readable storage medium, thereby providing a program to the computer  1200  via the network. 
     While the embodiments of the present invention have been described, the technical scope of the invention is not limited to the above described embodiments. It is apparent to those skilled in the art that various modifications or improvements can be made to the above described embodiments. In addition, the matters described for a specific embodiment can be applied to other embodiments within a scope not technically contradictory. In addition, each component may have a similar feature to other component having the same name and different reference signs. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the invention. 
     The operations, procedures, steps, and stages of each process performed by an apparatus, system, program, and method shown in the claims, embodiments, or diagrams can be performed in any order as long as the order is not indicated by “prior to,” “before,” or the like and as long as the output from a previous process is not used in a later process. Even if the process flow is described using phrases such as “first” or “next” in the claims, embodiments, or diagrams, it does not necessarily mean that the process must be performed in this order. 
     EXPLANATION OF REFERENCES 
     
         
           10 ,  20 ,  30 : LED 
           11 ,  21 ,  31 : terminal 
           15 ,  25 ,  35 : wafer 
           100 ,  200 ,  300 : test apparatus 
           110 ,  210 : electrical connection unit 
           111 ,  211 : substrate 
           112 : opening 
           113 ,  213 : probe 
           120 : light source unit 
           121 : light source 
           122 : parallel light 
           123 : lens unit 
           124 : filter holding unit 
           125 : temperature suppression filter 
           126 : temperature control unit 
           130 : measuring unit 
           140 : control unit 
           145 : storage unit 
           150 ,  155 : placement unit 
           156 : light transmission unit 
           160 : blocking unit 
           170 ,  175 ,  176 ,  177 : light intensity measurement unit 
           171 : holding unit 
           173 : sensor 
           1200 : computer 
           1201 : DVD-ROM 
           1210 : host controller 
           1212 : CPU 
           1214 : RAM 
           1216 : graphics controller 
           1218 : display device 
           1220 : input/output controller 
           1222 : communication interface 
           1224 : hard disk drive 
           1226 : DVD-ROM drive 
           1230 : ROM 
           1240 : input/output chip 
           1242 : keyboard