JPH011925A - Equipment for testing light emitting devices - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the optical testing of light emitting devices and display devices, and more particularly to the optical testing of light emitting devices and display devices, and more particularly, for use in conjunction with conventional automatic test equipment to test various light emitting devices. This relates to a device for optically testing.

BACKGROUND OF THE INVENTION With advances in automatic test equipment (ATE), testing of the electrical functionality of complex equipment has become highly automated. For example, printed circuit boards containing various individual components, integrated circuits, and other devices.

"bed of nail"
Test equipment allows a wide range of electrical tests to be performed. However, printed circuit boards often contain light emitting components, such as light emitting diodes and seven segment displays, which must be tested both electrically and optically. Optical testing determines whether a component actually emits light at the appropriate times, whether the emission exceeds a minimum allowable brightness, and whether the brightness is sufficiently uniform among a large number of components, etc. be judged.

One technique for optically testing light-emitting devices includes a mechanical vision system, such as a television camera aimed at the light-emitting device (DUT) under test.

The image formed by the camera provides information about the brightness of the emitter and the brightness of the background pixel by pixel. An analog/digital conversion is then performed and the equivalent binary value is stored in memory.

The problem that the invention aims to solve The disadvantages of this type of vision system are numerous.

First, the output signals generated by the vision system are typically not electrically equivalent to traditional ATE inputs, and therefore a direct connection between the vision system and the ATE host is not possible.6 As a result, testing Optical testing of the equipment under test cannot be combined with electrical testing into a common automated test program.

Second, for some types of optical testing, the vision system generates a large amount of data that is not useful. For example, suppose the purpose of the test is simply to determine whether a particular light emitting device emits light at a particular time. Also assume that the device under test is a printed circuit board containing a large number of widely spaced light emitting diodes, and that the viewing angle of the camera is wide enough to cover the entire surface of the circuit board. Under these conditions, most of the vixels in the image formed by the camera are not of the diode itself and are therefore not of interest.

Additionally, most of the corresponding binary data is irrelevant and a data reduction process must be performed, which typically requires complex image processing software.

Third, the camera exhibits a fixed, uniform spatial resolution over its entire field of view. This presents a significant disadvantage in cases where the device under test comprises multiple groups of closely spaced light-emitting devices at wide intervals. In order to analyze two adjacent light-emitting devices while monitoring the entire device under test, an additional camera must be added to the vision system, which increases the system cost from
and increased complexity.

Finally, the cost of a vision system includes the camera(s) and the large memory required to store the data.
It is very expensive because it requires image processing software.

SUMMARY OF THE INVENTION The present invention provides a test device that can be used in conjunction with conventional automatic test equipment to perform optical tests on a wide variety of light emitting devices.

The test apparatus includes a plurality of individual optical probes arranged in a preselected pattern, each probe corresponding to a particular light-emitting component of the device under test. Each probe is placed in close proximity to the light emitting component, and a fiber optic cable connects each probe to a detector. Each detector generates an electrical output signal related to the intensity of the light transmitted by the fiber optic cable. The detector output signal is electrically compatible with and can be directly coupled to a conventional ATE input. Each detector can be calibrated individually.

OPERATION OF THE INVENTION Each probe can be mounted in a fixed position or can be in a telescoping configuration to test devices having light-emitting components of varying heights. Additionally, the light conducting fiber within each fiber optic cable can be recessed relative to its casing, effectively reducing the acceptance angle.

As a result, the spatial resolution of the test equipment can be adjusted for each probe.

Advantages of the Invention The present invention provides additional advantages over conventional vision systems. For example, each light-emitting component being tested is paired with an individual probe, eliminating the need for a camera. Furthermore, since each probe is directed at a specific light-emitting component rather than an area containing multiple components, the present invention provides
Data is generated for only that light emitting component. Thus, by eliminating large amounts of irrelevant data, the present invention eliminates the need for large memories to store such data and the complex software required to process this data.

The test device and probe of the present invention are low in cost and simple in structure. Additionally, the test equipment is durable and easy to operate.

Example The invention is particularly pointed out in the claims.

These and other advantages of the present invention will be understood from the following detailed description, taken in conjunction with the accompanying drawings.

FIG. 1 is a block diagram illustrating a known system for automatically testing the electrical functionality of a given device. The automatic test equipment 2 is equipped with a plurality of output lines 4,
These lines are connected to a plurality of drive devices 6.

These drives 6 are then connected to a device under test (DUT) 10 by means of a plurality of probes 8 .

The device 10 undergoing this test is connected by a plurality of probes 12 to a plurality of electrical sensors 14 . These sensors 14 are provided with a plurality of output lines 16 connected to the test device 2.

Generally, test equipment 2 is programmed to automatically perform a series of electrical tests on device 10 under test. The sensor 14 is connected to the device 1 to be tested.
0 and supplies data to the test device 2. However, sensor 14 is generally responsive only to electrical signals and cannot sense optical signals generated by light-emitting components of device 10 under test.

FIG. 2 is a block diagram of a system for optically testing one or more light emitting devices. For consistency, parts similar to those shown in FIG. 1 are designated by the same reference numerals. Optical test equipment 24 includes one or more optical fibers 18 , each connected to a photodetector 22 by a fiber optic cable 20 . The probe 18 is placed in close proximity to the device 10 under test and the light generated by the components thereon.

It is sent along a fiber optic cable 20 to a detector 22 . The output line 17 of the detector 22 is connected to the sensor 14. As a result, the optical functionality of the device 10 subjected to the test can be automatically tested by the test device 2 in the same manner as described above.

FIG. 3 is an elevational view of the test apparatus 24 shown in FIG. Pinch plate 27 is arranged on retaining plate 26. Two tensioners 29 extend through the pinch plate 27 to the retaining plate 26. Additionally, two pins 31 extend upwardly from the device 10 under test. The two bushings 33 are attached to the retaining plate 26.
extends downward from the bottom of the

Both plates 26 and 27 have a plurality of bores 28 extending therethrough. These bores 28 are arranged in a preselected pattern that corresponds to the arrangement of a number of light emitting components 30, 32 and 34.

An optical probe 18 is disposed in each of these bores 28 . Each probe 18 is equipped with a fiber optic cable 2,0. Each cable 20 extends upwardly from the pinch plate 27 into a bore 38 located in the support member 36. A detector 22 is positioned adjacent each bore 38 and is connected to the end of a cable 20 disposed within the bore. Extending from each detector 22 is a multi-pin connector 42 lead 40 . Therefore, connector 42 connects test device 24
Serves as an interface to. connector 4
A connector 44 shaped to mate with 2 serves to connect test device 24 to sensor 14 via line 17 (FIG. 2).

Each tensioner 29 is, for example, a screw placed in a slot, and when this screw is loosened, the pinch plate 27
can be slid laterally relative to the retaining plate 26. By slightly laterally displacing the pinch plate 27 relative to the retaining plate 26 and tightening the tensioner 29, a lateral force is exerted on the probe 18. This lateral force tends to hold the probes 18 in their respective correct positions.

The operation of the test device 24 will be briefly described below.

First, the holding plate 26 is placed in close proximity to the device 10 being tested. pin 31 engages bushing 33;
Correct alignment of the holding plate 26 and the device 10 under test is ensured.

As a result, the probe 18 is placed in close proximity to the light-emitting components 30, 32 and 34, so that it can receive the light emitted by these components. Test equipment 2
The program controls the drive 6 which in turn enables the device 10 under test to operate in a series of preselected conditions or states. During one of the preselected states, one or more light emitting components 30, 32 or 34 emit light. The probe 18 corresponding to the component that emitted the light conducts a portion of the emitted light along its fiber optic cable 20 to its corresponding detector 22 .

Detector 22 generates an electrical output signal with a magnitude representative of the intensity of the light it receives. This output signal is sent along one of the leads 40 and lines 17 to the corresponding sensor 14. By comparing the output signals received from the various sensors 14 with preselected criteria, the test device 2 determines whether a particular light-emitting component actually emits light at the appropriate times and the brightness of that component. whether it is the minimum,
It can be determined whether two or more parts have uniform brightness, and so on.

Apart from mounting the probe 18 in a fixed position, 1
More than one probe can have a telescoping mechanism as shown in FIGS. 4A-4E. The fiber optic cable 20 includes a light-conducting inner core 50 surrounded by an outer cladding 49 and a jacket 48 . One end of the optical fiber cable 20 is inserted into a cylindrical sleeve 52 . This sleeve 52 can, for example, be secured to the jacket 48 by two crimping means 54. The portion of fiber optic cable 20 that extends below sleeve 52.

It is later cut to the desired length. As shown in FIGS. 4B and 4C, the free end of fiber optic cable 20 is inserted into spring 56, which is positioned adjacent to and over sleeve 52. As shown in FIGS.

Cable 20 (and sleeve 52 and spring 56) is then inserted into second sleeve 58.

A crimp means 60 located on the top of the sleeve 58 comprises:
Spring 56 is prevented from moving upward.

As shown in FIG. 4D, retaining ring 62 is slid to the free end of fiber optic cable 20 and positioned adjacent sleeve 58. Retaining ring 62 is secured to jacket 48 by crimp means 64 to limit downward movement of sleeve 52 and cable 20.

Applying an upward force to the bottom of probe 18 causes cable 2
0 and sleeve 52 move upward.

Retract the probe to compress spring 56.

When this force is removed, spring 58 returns probe 18 to its extended position. Therefore, as shown in FIG. 4E, the assembled probe 18 is attached to the holding plate 2.
Once positioned at 6, each individual probe 18 can be extended and retracted to accommodate devices under test with light emitting components of various heights.

The light-conducting inner core 50 can be selectively recessed into the jacket 48 along with the outer cladding 49. The effect of retracting the inner core 50 is that the acceptance angle of the probe 18 can be reduced. In other words, when inner core 50 is retracted, it accepts or "sees" light from a narrower field of view than it would otherwise. As a result, the spatial resolution of the test device 24 can be effectively changed from probe to probe. For example, if a number of light-emitting components are placed very close to each other, the acceptance angle of the corresponding probes may be adjusted so that one probe does not receive the light emitted by an adjacent component. can do.

FIG. 5 is a schematic diagram of the detector 22 shown in FIG. The two transistors 66 and 68 are arranged in a Darlington pair configuration. Transistor 68 is a light sensing transistor. The load resistor 70 is the transistor 6
6 and the ground potential. The end of fiber optic cable 20 is positioned proximate the collector base junction of transistor 68. lead 40
As shown in FIGS. 2 and 3, the electrical sensor 14
is directly connected to.

When light conducted by fiber optic cable 20 illuminates transistor 68, an output signal Vo is generated. The magnitude of this output signal vO represents the magnitude of the brightness of light received by the transistor 68.

The combination of transistors 66 and 68 is available as a separate part, such as Motorola part MFOD-73, which includes a connector for attaching fiber optic cable 20. The load resistance 70 is
For example, it may be a separate resistor or a rheostat. When using a rheostat, each detector 22 is
Individual calibration can be accomplished by simply placing the probe 18 near the calibrated light source and adjusting the rheostat to set the output signal Vo to a predetermined level.

The foregoing description is limited to specific embodiments of the invention. However, some or all of the effects of the present invention can be obtained even if various changes and modifications are made to the present invention. It is therefore intended that all such changes and modifications that come within the spirit and scope of the invention be included within the scope of the following claims.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of a known system for automatically testing the electrical functionality of a device under test; FIG. 2 is a functional block diagram of a known system for automatically testing the electrical functionality of one or more light-emitting devices; FIG. 3 is an elevational view of an optical test apparatus constructed in accordance with a preferred embodiment of the present invention; FIGS. 48-4E; FIG.
The figures are a series of cross-sectional views showing the assembly of the telescoping probe, and FIG. 5 is a circuit diagram of the detector shown in FIG. 2...Test device 6...Drive device 8...Probe 10...Device to be tested 12...Probe 14...Sensor 20...Optical fiber cable 22...Photodetector 24 ...Optical test device 26...Holding plate 27...Pinch plate 28...Bore 29...Tightener 30.32.
34...Light emitting part 33...Bushing 42.44...Cleaning of connector n section (1 piece in content) FIGURE 5 Procedure amendment writing method) 1. Indication of incident Patent application No. 1988 67976 No. 2
, Title of the invention Apparatus 3 for testing light emitting devices
, Relationship to the case of the person making the amendment Applicant name: Zienrad Incorporated 4,
Agent Address: 3-3-1 Kuunouchi, Chiyoda-ku, Tokyo Telephone:
211-8741 Name (5995) Patent Attorney Minoru Nakamura
.

Claims (15)

[Claims] (1) A retractable probe for optically testing a light emitting device, comprising a fiber optic cable having first and second ends, the cable including a light conducting fiber disposed within a casing. an optical fiber cable and an extension means,
the first end of the cable is disposed on the extension means, and in response to a longitudinal force applied to the cable;
A telescoping probe characterized in that said extension means serve to retract and extend said first end of said cable. (2) the extension means further comprises a spring, the casing being threaded through the spring, the spring being spaced apart from the first end of the cable, and further comprising a first sleeve, the casing being threaded through the spring; threaded through the sleeve such that the first sleeve is disposed between the first end of the cable and the spring, the first sleeve being secured to the casing, and further comprising: the spring and the spring; a second sleeve surrounding a portion of the first sleeve, the second sleeve being secured to the casing such that the spring
movement along the casing in a direction away from an end of the second sleeve, further comprising a retaining ring, the casing being threaded through the ring and disposed adjacent the second sleeve, the retaining ring being disposed adjacent the second sleeve; The second sleeve was prevented from moving along the casing in a direction away from the first end, and the first sleeve was allowed to slide longitudinally within the second sleeve. The probe according to claim 1. (3) the second end of the cable is connected to detection means for generating an output signal in response to the light transmitted by the fiber; 2. The probe of claim 1, having a size related to the strength of the probe. (4) The probe according to claim 3, wherein the detection means includes means for calibrating the output signal. 5. The probe of claim 1, wherein the light conducting fiber is recessed into the casing a preselected distance to reduce the receiving angle of the fiber. (6) An apparatus for optically testing one or more light emitting devices arranged in a preselected pattern, comprising holding means for fixing one or more probe means, the probe means arranged to correspond to said preselected pattern, i) each of said probe means includes a light conducting fiber and a detector, said fiber having first and second ends; said first end of the fiber is adapted to receive light emitted by a selected one of said light emitting devices, said second end of said fiber is connected to detection means, ii) said detection means , generating an output signal in response to the light transmitted by the fiber, the output signal having a magnitude related to the intensity of the light. (7) The holding means includes a first plate means having a plurality of holes arranged therein, the holes being arranged to correspond to the preselected pattern, each of the holes being arranged in a manner corresponding to the preselected pattern. 7. Apparatus according to claim 6, wherein the hole is adapted to receive one or more of said probe means. (8) The holding means further includes a second plate means, the second plate means being disposed adjacent to the first plate means, and the second plate means including: A plurality of holes are arranged corresponding to the holes arranged in said first plate means, said second plate means comprising one or more tightening means, said tightening means comprising:
8. The apparatus of claim 7, wherein said second plate is secured to said first plate, whereby each said probe means is held in a substantially constant position. (9) the optical conductive fiber is arranged within the casing;
7. The apparatus of claim 6, wherein the fiber is retracted into the casing by a preselected distance, thereby effectively reducing the acceptance angle of the fiber. 10. The apparatus of claim 6, wherein the detector includes means for calibrating the output signal. (11) An apparatus for optically testing one or more light-emitting devices arranged in a preselected pattern, the light-emitting devices being interfaced to automatic test equipment to be automatically tested. an optical test apparatus comprising retaining means for securing one or more probe means, the probe means being arranged to correspond to said preselected pattern; i) a plurality of said probe means; each includes a light conducting fiber and a detector, said fiber having first and second ends, said first end of said fiber being emitted by a selected one of said light emitting devices; said second end of said fiber is connected to detection means, ii) said detection means for generating an output signal in response to the light transmitted by said fiber; Test equipment, characterized in that the output signal has a magnitude related to the intensity of the light, and that the output signal is compatible with the automatic test equipment. (12) The holding means includes plate means, and the first
a plurality of holes are disposed in the plate means, the holes being arranged to correspond to the preselected pattern, each of the holes being adapted to receive one or more of the probe means; Apparatus according to claim 11. (13) The holding means further includes a second plate means, the second plate means being disposed adjacent to the first plate means, and the second plate means including:
A plurality of holes are arranged corresponding to the holes arranged in said first plate means, and said second plate means includes one or more tensioning means, said tensioning means being arranged in said second plate means. 13. The apparatus of claim 12, wherein the probe means is fixed to the first plate, whereby each of the probe means is held in a substantially fixed position. 14. The light conducting fiber is disposed within a casing, and the fiber is retracted into the casing a preselected distance, thereby effectively reducing the acceptance angle of the fiber. equipment. 15. The apparatus of claim 11, wherein the detector includes means for calibrating the output signal.