JPS6338175A - Measuring instrument for light emission characteristic of semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To measure a light emitting element in a chip state or at a stage close to its state by processing a photodetected image remaining in a video camera owing to after image characteristics of a solid-state image pickup element and computing light emission characteristics. CONSTITUTION:When a measurement start command is inputted to a processor 11, a driving pulse generator 9 applies driving pulses to the light emitting element 1 through a probe 14 and the element 1 emits light instantaneously. Its emitted light is diffracted spectrally; and light (a) is projected on a screen 3 and picked up by a video camera 5 and light (b) is picked up by a video camera 6 respectively. At this time, images remains in the video cameras 5 and 6 awhile because of the characteristics of the solid-state image pickup elements and image signals are sent out to the processor 11. The processor 11 computes light emission characteristics and sends out the result to a display/recording device 12, which outputs the air field pattern and field pattern of the element 1. Then electric power for light emission is applied for an about 100sec short time and the element 1 never has such as temperature rise that thermal stress remains even before being cased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for measuring characteristics of laser diodes, light emitting diodes, and semiconductor light emitting devices.

[Prior art]

In particular, semiconductor light-emitting devices (hereinafter referred to as light-emitting devices) used as light generation sources serving as measurement media are required to have good light-emitting characteristics, so it is important to measure the light-emitting custom-made products. The light emitting characteristics of a light emitting element are divided into far field pattern characteristics, in which the light emission of the light emitting element is observed at a position distant from the light emitting point, and near field pattern characteristics, in which the light emitting state at the light emitting point of the light emitting element is observed. be.

Conventional far-field pattern custom-made measurement equipment projects the light from the light-emitting element to be measured onto a photodiode array, switches each cell of the photodiode array using a demultiplexer, and detects the light reception level of each cell. We process it using a processing unit (CPU) to obtain custom orders.

In addition, conventional near-field pattern custom-made measurement equipment uses an optical system to magnify the image of the light-emitting end face of the light-emitting element to be measured and forms the image on the photodiode array, and in the same way as above, each cell of the photodiode array receives light. The level is detected and pressure is applied to the processing equipment.

[Problem that the invention seeks to solve]

According to the conventional measuring device described above, the light emitting drive of the light emitting element to be measured needs to be repeated as many times as the number of cells in the photodiode array, and therefore thermal stress is applied to the light emitting element to be measured. It is necessary to measure the characteristics after appropriate heat dissipation measures have been taken, that is, when the light emitting element chip is sealed inside the case and the product is ready. Conventional measuring devices are not suitable as means for custom-made measurements in the manufacturing process of light emitting devices because the number of steps required to seal the light emitting device chips is wasted.

Additionally, it is desirable that far-field pattern characteristics and near-field pattern customization be measured under the same light emission conditions, but with conventional measurement equipment, far-field pattern characteristics and near-field pattern characteristics are measured using separate devices. However, there is a problem in that it is difficult to make the measurement conditions the same.

The present invention is proposed to solve the above problems, and it is possible to determine the state of a light emitting element when it is in a chip state or a state close to it (for example, in a heaton in a case/in a state with a chip mounted on a case). The object of the present invention is to obtain an apparatus, and further to obtain an apparatus capable of simultaneously measuring far-field pattern characteristics and near-field pattern characteristics at the above-mentioned stage.

[Means for solving problems]

For the above purpose, the present invention sets the light emitting drive time of the light emitting element to be measured to an extremely short time (for example, about 100 nSec) to the extent that no thermal stress remains on the chip of the light emitting element, and The instantaneous light emission is imaged with a video camera (CCD type or MOS type video camera) using a solid-state image sensor, and even after the instantaneous light emission ends, the received light image that remains on the video camera due to the characteristics of the solid-state image sensor is captured. The instantaneous light emitted from the light emitting element is split into two directions by a spectroscopic means (for example, -fmirror), and the light emitting characteristics of the light emitting element are obtained by processing the light emitting element. The light is projected onto a screen and imaged by the video camera to obtain far-field pattern characteristics, and the light from the other direction is directly imaged by the video camera to obtain near-field pattern characteristics. .

[Configuration of Example]

FIG. 1 is a block diagram showing the arrangement of the optical system and each part of the processing system of an apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the optical system includes a spectroscopic means (hereinafter referred to as a spectroscopic means) such as a half mirror, which is provided in front of the path (a) of the light emitted from the light emitting element 10 to be measured with its reflective surface facing the light emitting element 1 side. , taking a half mirror as an example) 2, the half mirror 2 is 2
The path (hereinafter referred to as the direction) of the first light that has been split into two directions.

) (B) and the second direction (C) (The path of the transmitted light of the half mirror 2 is the first direction (B), and the path of the reflected light is the second direction.
Let the direction be (c). )K respectively provided with a screen 3 and a magnifying lens 4, a first direction (b) and a second direction e two video cameras 5 whose imaging directions (lens orientations) are respectively set. and 6.

The video cameras 5 and 6 are, for example, C.
It has a solid-state image sensor such as a CD image sensor or a MOS image sensor. This solid-state image sensor has an afterimage characteristic that retains a light-receiving image for a while even after light is no longer being received.

Further, the video cameras 5 and 6 are respectively provided with electric aperture mechanisms 51 and 61 that control the amount of incident light. For example, when the light-emitting element 1 to be measured has a strong emission intensity, such as a laser diode, the electric aperture mechanism 51, 61 reduces the amount of incident light so that the solid-state image pickup devices of the video cameras 5 and 6 do not become saturated. B. This is not necessary if the light emitting element 1 is an element with low emission intensity. Note that the twJ aperture mechanism 51, 61 is the video camera 5, 6.
The one built into the lens can be used.
When the amount of incident light cannot be suppressed by the aperture mechanism built into the lens, a separate aperture mechanism with a larger aperture ability is provided.

The screen 3 projects the light emitted from the light-emitting cable 1, and the projected image on the screen 3 is transmitted to the first video camera 5 (symbol # to distinguish between the two video cameras).
5" is called the "first video camera", and the one with symbol #6# is called the second video camera) to obtain the far field pattern characteristics. In other words, the focus of the first video camera 5 is aligned with the projected image on the screen 3.

Further, the magnifying lens 4 magnifies the light emitting point of the light emitting element 1, and the light emitting point of the light emitting element 1 magnified by the magnifying lens 4 is imaged by a second video camera or camera 6 to obtain near field pattern characteristics. .

That is, the focus of the second video camera 6 is set at the imaging position 1it of the light-emitting point of the light-emitting element 1 by the magnifying lens 4 (at a distance from the light-emitting point!#).

In the configuration of the optical system described above, a magnifying lens 4 is provided in the first path (b), a screen 3 is provided in the second path (c), and the near field pattern is captured by the first video camera 5. Customization may be made to obtain the far field pattern characteristics with the second video camera 6.

In addition, when it is necessary to measure only either the far-field pattern characteristics or the near-field pattern characteristics, there is no need for spectroscopy using the half mirror 2, and the path of the emitted light from the light-emitting element 10 (a) is replaced by the screen 3 or magnification. It is only necessary to provide a lens 4, and only one video camera is required.

Furthermore, the magnifying lens 4 may not be necessary in some cases, such as when the light emitting element 1 has a large light emitting area, or when the video camera 6 for near-field pattern imaging has an image magnifying function.

Next, as shown in FIG. 1, the processing system processes the video camera 5.
Two A/D converters each convert image signals from 6 to A/D.
D converters 7 and 8, a drive pulse generator 9 that supplies a drive pulse with an extremely short duration to the light emitting element to be measured IK, and a synchronization signal sent to the video camera 5.6 and A/D converters 7 and 8; The system is also controlled all at once, including a synchronizing signal generator 10 that sends a drive pulse sending timing signal to the drive pulse generator 9, and setting of aperture values of the electric aperture mechanisms 51 and 61 of the video cameras 5 and 6. Tomo K, above A/D
A processing device (so-called CPU) 11 for processing images 1 and 1 sent from the video cameras 5 and 6 via the converter 7.8 to obtain custom-made light emission (custom-made far-field pattern and custom-made near-field pattern); Display/recording device 12 for displaying and/or recording the luminescence #j obtained in step 11
Consists of.

The mechanism for supplying light emitting power from the driving pulse generator 9 to the light emitting element 1 may have an appropriate structure depending on the type of the light emitting element 1 and the processing method used in the measurement stage. For example, if the light emitting element 1 is a laser diode, If all the measurement of the light emitting characteristics is carried out at the stage of the chip, since both sides of the chip are Ti and there are light emitting points on the end faces, the Rf stand 13 of the light emitting element 1 is The probe 14 is connected to the Ikekata pole of the output of the drive pulse generator 9, with one pole of the output of the drive pulse generator 9 connected to the placed seedling 13, and the probe 14 connected to the Ikekata pole of the output of the drive pulse generator 9. The structure may be such that it is brought into contact with the @ pole on the upper surface of the light emitting element 1 on the mounting table 13.

[Effect of the embodiment]

FIG. 2 is a time chart for explaining the operation of the embodiment, and shows signals sent to points A to F shown in FIG. 1. The operation of the embodiment shown in FIG. 1 will be explained with reference to FIG. Note that the following operation is an operation when the light emitting element 1 to be measured is a laser diode with high emission intensity.

The processing device 11 is inputted with predicted maximum value data of the light emission intensity of the light emitting element 1 from a data input device (not shown), and the processing device 11 inputs the predicted maximum value data to the video cameras 5 and 6 from the predicted maximum value data. An optimum aperture value is calculated so that the level of incident light does not saturate the solid-state image pickup device (does not reach the maximum image pickup level), and each electric aperture mechanism 51, 61 is set to the optimum aperture value.

As shown in FIG. 2A, the synchronization signal generator 10 sends a camera synchronization signal to the video cameras 5, 6 and the A/D converter 7.8 at a set period t. repeats the imaging operation, and the A/D converter 7.8 sends the surface image signal converted into a digital signal to the processing device 11 in synchronization with the imaging operation of the video camera 5.6. However, at this stage, the light emitting element 1 is not emitting light, so a signal related to measurement is not yet sent out.

After placing the light emitting element 1 on the mounting table 13 and setting the probe 14 on the light emitting element 1, when a measurement start command is input to the processing device 11, the processing device 11 generates a washing synchronization signal generator as shown in FIG. 2B. 10/Send out yacht 1S. The synchronization signal generator 10 sends the drive pulse sending timing 1M shown in FIG. 2 CK to the drive pulse generator 9 at the same time as the first camera synchronization signal sent after the yacht signal sent to the above eight points is manually input. . From this K, the operating pulse generator 9 outputs a drive pulse with a pulse width of 11 to the probe 14 as shown in the second diagram.1, the pulse width of this drive pulse is ttlti1o.

It is set for an extremely short time of about n5ec,
These pulses pass through the entire probe 14 to the light emitting element 1:
The light emitting element 1 is marked as JD, and the light emitting element 1 is illuminated at the same time. Note that the pulse width of the above drive pulse is 1. Even if it is specified in the synchronization signal generator 10 or the drive pulse generator 9
It may also be specified.

When the light emitting element 1 emits light as described above, FIG.
As shown, the emitted light is emitted in the direction of the light path (a), and the emitted light is emitted from the half mirror 2 (therefore, the first direction (b)
The light is split into a second direction (c) and proceeds.

The emitted light that has proceeded in the first direction draws a projected image on the screen 3, and this projected image is captured by the first video camera 5, which is focused on the screen 3. Further, the emitted light that has proceeded to the second direction (c) is focused on the imaging position of the light emitting point of the light emitting element 10 by the magnifying lens 4 (or the light emitting point of the light emitting element 1 when the magnifying lens 4 is not present). The image is captured by the second video camera 6.

In the above operation, the imaging time of the two video cameras 5 and 6 is 100 nsec per light emitting interval of the light emitting element 1, but the solid-state image sensor used in the video cameras 5 and 6 is According to the custom order, the captured images remain in the respective video cameras 5 and 6 for a while, and as shown in FIG. 2FK, image signals based on the remaining images are sent to the processing bag fil. Then, according to the camera synchronization signal sent from the synchronization signal generator 10, the image signal output from the video camera 5.6 is synchronized with the imaging operation of the video camera 5, 6, and the image signal is sent to the A/D converter 7, 8. The signals are each converted into digital signals and input to the processing device 11. It is assumed that the scanning of the imaging screens of the video cameras 5 and 6 is completed in one cycle of the camera synchronization signal.

Incidentally, since the retention level of the images remaining in the video cameras 5 and 6 slowly attenuates with the passage of time, the level of the image signal described above gradually decreases as shown in FIG. 2FK.

However, since the light emission timing of the light emitting element 1 is synchronized with the camera synchronization number 1B, the time between the light emission of the light emitting element 10 and the image readout from the video camera 5.6 is kept constant, so that the image signal of the image signal is Since the ratio (1,/1.) between the maximum level t and the minimum level 1t is constant, this reduction in the image signal can be corrected by processing in the processing device 11.

In the processing device 11, the video camera 5,
The display/recording device [12
The display/recording device 12 outputs a far field pattern and a near field pattern of the light emitting element 1.

In the above operation, the time for applying light emitting power to the light emitting element 1 is 1 o on 5 ec, i degrees, which is an extremely short time, and the light emitting element 1 is exposed to thermal stress even before the casing. It is not subject to temperature rise.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the time for applying light emitting power to the light emitting element to be measured is extremely short, about 100 n5ec, so even if the light emitting element to be measured is in a state before the casing, The light emitting element is not subjected to a temperature rise that would cause residual thermal stress. Therefore, since the light emitting characteristics can be measured at the chip or at a processing stage close to the chip, wasteful casing work for defective products can be avoided.

In addition, since the light emitted by the light-emitting element to be measured is spectrally analyzed and the far-field pattern characteristics and near-field pattern custom-made are measured at the same time, the two custom-made can be measured under the same environmental conditions, resulting in extremely reliable measurement data. is obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a time chart showing the operation. (Main symbols) 1... Light-emitting element to be measured 2... Nof mirror 3.
...Screen 4...Magnifying lens 5.6...
Video camera 9... Drive pulse generator 11... Processing device. Figure 1

Claims (1)

[Scope of Claims] 1. A drive pulse generator that supplies light emitting power to a semiconductor light emitting device under test for an extremely short period of time, and instantaneous light emission of the semiconductor light emitting device when the light emitting power is supplied from the drive pulse generator. Light emission of a semiconductor light emitting element, which is made up of a video camera using a solid-state image sensor to take an image, and a processing device that processes the received light image remaining in the video camera due to the afterimage custom order of the solid-state image sensor and calculates the light emission custom order. Characteristic measuring device. 2. The device for measuring light emitting characteristics of a semiconductor light emitting device according to claim 1, wherein the video camera is a CCD type video camera. 3. The device for measuring light emitting characteristics of a semiconductor light emitting device according to claim 1, wherein the video camera is a MOS type video camera. 4. A drive pulse generator that supplies light emitting power for an extremely short period of time to the semiconductor light emitting device under test, and two paths of light caused by the instantaneous light emission of the semiconductor light emitting device when the light emitting power is supplied from the drive pulse generator. A spectroscopic means that divides the light into directions, a screen that projects the transmitted light into one direction,
A video camera in which a solid-state image sensor is used and whose imaging direction is set in one of the above directions and is focused on the screen, and a video camera in which a solid-state image sensor is used and whose imaging direction is set in the other direction The above two videos are captured by a video camera separate from the above which is set in the same direction and focused on the light emitting point of the semiconductor light emitting device or a position equivalent to the light emitting point, and the afterimage characteristics of the solid state image sensor. A light emitting characteristic measuring device for a semiconductor light emitting device, comprising a processing device that processes a received light image remaining in a camera and calculates far field pattern characteristics and near field pattern characteristics of the semiconductor light emitting device. 5 Claim 4 in which the spectroscopic means is a half mirror
An apparatus for measuring light emitting characteristics of a semiconductor light emitting device according to 2. 6. The device for measuring light emitting characteristics of a semiconductor light emitting device according to claim 4, wherein the video camera is a CCD type video camera. 7. The device for measuring light emitting characteristics of a semiconductor light emitting device according to claim 4, wherein the video camera is a MOS type video camera.