JP4449145B2 - Inspection device for light emitting element array - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inspection apparatus for a light emitting element array that measures the operation and light quantity distribution of light emitting element arrays that are sequentially turned on, rather than all the light emitting points are turned on all at once.
[0002]
[Prior art]
A write head (optical write head) of an optical printer is a light source for exposing a photosensitive drum to light, and has a light emitting element array. FIG. 1 shows a principle diagram of an optical printer having an optical writing head. A photoconductive material (photosensitive member) such as amorphous Si is made on the surface of the cylindrical photosensitive drum 2. This drum rotates at the speed of printing. The surface of the photosensitive drum of the rotating drum is uniformly charged by the charger 4. Then, the optical writing head 6 irradiates the photosensitive member with light of a dot image to be printed, and neutralizes the charging where the light hits. Subsequently, the developing unit 8 applies toner to the photoconductor according to the charged state on the photoconductor. Then, the toner is transferred onto the paper 14 sent from the cassette 12 by the transfer device 10. The sheet is heated and fixed by the fixing device 16 and sent to the stacker 18. On the other hand, the drum that has been transferred is neutralized by the erasing lamp 20 over the entire surface, and the remaining toner is removed by the cleaner 22.
[0003]
The structure of the optical writing head 6 is shown in FIG. The optical writing head is composed of a light emitting element array 24 and a rod lens array 26, and the focal point of the lens is formed on the photosensitive drum 2.
[0004]
In the optical writing head, the direction in which the light emitting points of the light emitting element array are arranged (parallel to the rotation axis of the photosensitive drum) is the main scanning direction, and the direction orthogonal to the main scanning direction is the sub scanning direction.
[0005]
The light-emitting element array used in such an optical writing head is connected to a driver circuit having a sequential lighting function or includes a driver having a sequential lighting function in order to light up sequentially.
[0006]
Such a light emitting element array is manufactured on a wafer, cut into chips, and incorporated into a write head. Regardless of which inspection is performed, an inspection for evaluating the quality of the light emitting element array by measuring the operation and light quantity distribution is performed.
[0007]
FIG. 3 shows a conventional light-emitting element array inspection apparatus. In this conventional apparatus, in order to measure the amount of light emitted from the light emitting element array 80, the light receiving head 100 including the imaging optical system 102 and the light receiving element 101 is disposed immediately above the light emitting point, and the output signal of the light receiving element 101 is output. taking measurement. In the figure, reference numeral 103 denotes a signal line from the light receiving element.
[0008]
[Problems to be solved by the invention]
Since the imaging optical system 102 has a relatively large numerical aperture, the field of view is narrow, and the position of the light receiving head 100 is adjusted each time the position of the light emitting point of the light emitting element array changes. In this case, the light emitting element array 80 may be moved or the light receiving head 100 may be moved. However, when the inspection apparatus is used for the prober inspection in the wafer state, it is difficult to move the wafer side. Therefore, the light receiving head side is moved. Thus, since it is necessary to mechanically move the light receiving head, it takes time to measure the light amount distribution of the light emitting element array.
[0009]
In addition, in the case of a light-emitting element array with a built-in driver or a light-emitting element array with a driver circuit connected, to check whether all the light-emitting points emit light normally, the correct position must be reached under the actual usage conditions. It is necessary to check whether the light emitting point emits light.
[0010]
In the conventional light emitting element array inspection apparatus, if it is intended to obtain the position information of the light emitting point, a light receiving head is required that can only view one light emitting point of the light emitting point array that is fully lit in actual operating conditions. . In such a light receiving head with a narrow field of view, a slight positional deviation also affects the sensitivity, so a highly accurate feeding mechanism is required. In addition, as many feeding operations as the number of light emitting points occur, and it takes time for measurement.
[0011]
An object of the present invention is to provide an inspection device for a light emitting element array capable of measuring the operation and light quantity distribution of the light emitting element array in a short time.
[0012]
[Means for Solving the Problems]
In a light emitting element array with a built-in driver, a light emitting element array to which a driver circuit having a sequential lighting function is connected, or an optical writing head configured to have a light emitting element array, are all light emitting points emitting normally? In order to confirm this, the spatial light quantity is examined, and the number and position of the peaks are examined. This can be realized by a combination of a light receiving element array arranged in “at least one dimension” and an imaging system. However, in a light receiving element array such as a one-dimensional CCD, there are many variations in sensitivity and noise, and it is difficult to obtain an accurate light output from this output. Further, if a sufficient number of light receiving elements do not receive light for one light emitting point of the light emitting element array, an accurate light quantity value cannot be obtained due to the beat component of the pitch between the light emitting elements and the light receiving elements.
[0013]
Therefore, in the present invention, a second light receiving element different from the CCD light receiving element is placed at a position away from the light emitting element array, and the light receiving points of the light emitting element array are turned on one by one in order. By measuring the output signal of the element, it was possible to accurately measure the amount of light.
[0014]
Therefore, the light-emitting element array inspection apparatus of the present invention is characterized in that the measurement of the light amount distribution of the light-emitting element array is time-divided and it is spatially determined whether or not there is a point that does not emit light in the light-emitting element array. .
[0015]
According to a first aspect of the invention,
In the inspection device for the light emitting element array that measures the operation of the light emitting element array that lights up sequentially, the light quantity distribution,
An imaging optical system that forms an image of light emitted from the light emitting point of the light emitting element array;
A half mirror that divides light passing through the imaging optical system into two directions;
A light receiving element array for receiving one of the divided lights;
A light receiving element for receiving the other divided light,
Evaluating the operation of the light emitting element array by the output of the light receiving element array,
Measure the light distribution by the output of the light receiving element,
It is characterized by that.
[0016]
According to a second aspect of the invention,
In the inspection device for the light emitting element array that measures the operation of the light emitting element array that lights up sequentially, the light quantity distribution,
An imaging optical system that forms an image of light emitted from the light emitting point of the light emitting element array;
A light receiving element array for receiving light passing through the imaging optical system;
A light receiving element that receives light emitted from the light emitting point of the light emitting element array,
Evaluating the operation of the light emitting element array by the output of the light receiving element array,
Measure the light distribution by the output of the light receiving element,
It is characterized by that.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0018]
[Example 1]
FIG. 4 shows a light-emitting element array inspection apparatus according to the first embodiment. This apparatus includes a light receiving head 200. In this light receiving head, an imaging optical system 202 provided on the side facing the light emitting element array 80, a half mirror 203, and a light receiving element array provided in a portion where light transmitted through the half mirror 203 forms an image. 204 and a light receiving element 201 for light output monitoring provided in a portion where the light reflected by the half mirror 203 forms an image.
[0019]
In the figure, 205 is a signal line of the light receiving element 201, and 206 is a signal line of the light receiving element array 204.
[0020]
The light emitted from a light emitting point of the light emitting element array 80 passes through the coupling optical system 202 and is divided into two paths by the half mirror 203. One light is directed to the light receiving element 201 and the other light is directed to the light receiving element array. An image is formed on 204. These light emission point images move on the light receiving element 201 and the light receiving element array 204 as the position of the light emitting point of the light emitting element array moves. Therefore, the light receiving range of the light receiving element 201 and the light receiving element array 204 needs an area in which the light emitting point image of the moving light emitting element array can be accommodated.
[0021]
Specifically, the light receiving element array 204 is a one-dimensional CCD sensor having a pixel pitch of 6 microns and a number of pixels of 1024 bits. The refresh rate of the CCD was 50 Hz. On the other hand, as the light receiving element 201, a Si photodiode having a light receiving portion of 10 mm × 10 mm was used, and the short-circuit current was subjected to current-voltage conversion of 10 ⁸ V / A and extracted as a voltage signal. In addition, the image forming optical system 202 is 1 ×. The distribution ratio of the half mirror 203 is 50:50. For this reason, the pitch of the 600 dpi light emitting points of the light emitting element array corresponds to about 7 pixels on the CCD.
[0022]
Next, the operation of the light emitting element array inspection apparatus having the above configuration will be described.
[0023]
The light emitting element array 80 to be measured is a 600 dpi, 128 light emitting element built-in driver type light emitting element array.
[0024]
First, when the light emitting element array 80 is lit at the upper limit speed at which it is actually used, it is confirmed whether there is any abnormality in the light emitting point transfer operation. Here, all the points were lit at a transfer rate of 2 Mdot / s. Since 128 pixels are drawn at 2 Mdot / s, the time required for the light emitting element array to draw one line is 64 μs. Since the frame frequency of the CCD is 50 Hz, an average light amount distribution of light emission of about 300 times is obtained in the light receiving element array 204. A certain threshold is set for this light quantity distribution, the number of peaks exceeding this threshold is counted, and when the number of light emitting points of the light emitting element reaches 128, a normal transfer operation is performed. Judge that Since there is a spatial sensitivity distribution unique to the optical system, the output signal is corrected by numerically multiplying the inverse function of the spatial sensitivity distribution function. An example of the evaluation result signal is shown in FIG. In the figure, the 30th to 90th portions of the CCD pixel numbers (1 to 1024) for the first 7 light emitting points are shown. The vertical axis is the output of the light receiving element array, and 255 is the output of the AD converter that becomes full scale.
[0025]
Next, the transfer rate was set to 1 kdot / s, the output signal of the light receiving element 201 was measured, and the light output distribution of each light emitting point was obtained. The light output was measured 100 μs after the target light emitting point started to emit light. Here, the reason why the transfer speed of the light emitting point is slowed down to 1 kdot / s is that the current-voltage conversion speed is not so fast and that the measurement is repeated in order to increase the measurement accuracy. Since there is a spatial sensitivity distribution unique to the optical system, the output signal is corrected by numerically multiplying the inverse function of the spatial sensitivity distribution function. An example of the evaluation result signal is shown in FIG. The vertical axis is converted to output power by multiplying by a certain correction coefficient. From FIG. 6, it can be seen that the light output is detected and the transfer operation is normally performed for all 128 light emitting points.
[0026]
[Example 2]
FIG. 7 shows a light emitting element array inspection apparatus according to the second embodiment. This apparatus differs from the apparatus of the first embodiment of FIG. 4 in that a light receiving element 201 is provided outside the measuring head 300 without using a half mirror. The same components as those in FIG. 4 are denoted by the same reference numerals.
[0027]
According to this light-emitting element array inspection apparatus, the influence of the angle dependency of the half mirror can be eliminated. The operation is the same as that of the light emitting element array detection apparatus of FIG.
[0028]
[Example 3]
Instead of making all the light emitting points emit light at the time of evaluation by the light receiving element array 204, for example, it is possible to make evaluation by lighting every other light emitting point. For this method, any of the light-emitting element array inspection apparatus shown in FIG. 4 or 7 can be used.
[0029]
FIG. 8 shows an output signal example of the light receiving element array 204 when the 1200 dpi / 256 light emitting element array is fully lit. The light emission point pitch of 1200 dpi corresponds to about 3.5 pixels on the CCD, and as can be seen from FIG. 8, the difference between the maximum value and the minimum value of the light amount distribution corresponding to each light emission point is not so great. For this reason, it is necessary to set a high threshold value for determination, and there is a possibility of erroneous determination.
[0030]
Therefore, according to the present embodiment, all the odd-numbered light emitting points are first turned on, the light output distribution of the light receiving element array 204 (see FIG. 8) is taken, the number of peaks is counted, and then only the even-numbered light emitting points are counted. All the lights were turned on and the number of peaks was counted to confirm that normal transfer operation was performed. The measurement of the light output by the light receiving element 201 is the same as that in the first embodiment.
[0031]
This evaluation method can also be used when the difference between the maximum value and the minimum value is not so large when the width of the non-light emitting portion (distance in the main scanning direction) is narrow relative to the pitch of the light emitting points of the light emitting element array.
[0032]
Also, this evaluation method can be used when an optical writing head is evaluated when a light emission point image (light emission spot) spreads due to the influence of a rod lens or the like, making it difficult to distinguish between two adjacent light emission points.
[0033]
In this embodiment, the odd number / even number and every other one are turned on, but the present invention is not limited to this, and any number may be used as necessary.
[0034]
[Example 4]
In the first and second embodiments, the light-emitting element array 204 is a one-dimensional light-emitting element array. However, in this embodiment, a two-dimensional light-receiving element array is used instead of a one-dimensional light-receiving element array.
[0035]
When evaluating an optical writing head, the position of the light emission spot may be shifted in the sub-scanning direction due to the influence of a rod lens or the like. By using the two-dimensional light receiving element array, the center of gravity of the light emitting spot can be simultaneously evaluated. Using this data, the timing of light emission can be adjusted to compensate for the deviation of the light emission spot in the sub-scanning direction.
[0036]
When evaluating an optical writing head, the size of the light emission spot may vary due to the influence of a rod lens or the like. Using a two-dimensional light receiving element array, the size of the light emission spot can be measured simultaneously. By using this data and adjusting the amount of light at the light emitting point, it is possible to compensate for the influence of fluctuations in the light emitting spot.
[0037]
【The invention's effect】
According to the present invention, when evaluating a light emitting element array that is sequentially turned on, and an optical writing head that combines the light emitting element arrays, the light amount distribution is measured in a time-sharing manner, and whether or not there is any point that does not emit light is a space. Therefore, the light quantity distribution measurement and the normal light emission at the light emission point can be simultaneously confirmed in a short time.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a principle diagram of an optical printer including an optical writing head.
FIG. 2 is a diagram showing a structure of an optical writing head.
FIG. 3 is a diagram showing a conventional light-emitting element array inspection apparatus.
FIG. 4 is a diagram showing a light-emitting element array inspection apparatus according to a first embodiment.
FIG. 5 is a diagram illustrating an example of an evaluation result signal.
FIG. 6 is a diagram illustrating an example of an evaluation result signal.
FIG. 7 is a view showing a light emitting element array inspection apparatus according to a second embodiment.
FIG. 8 is a diagram illustrating an example of an output signal of a light receiving element array.
[Explanation of symbols]
80 Light emitting element array 200 Light receiving head 201 Light receiving element 202 Imaging optical system 203 Half mirror 204 Light receiving element array 205 Signal line 206 of light receiving element 201 Signal line 300 of light receiving element array 204 Light receiving head

Claims (7)

In the light emitting element array inspection apparatus for measuring the light emission distribution, the light emitting point transfer operation of the light emitting element array having the light emitting points that are sequentially turned on,
An imaging optical system for focusing the light emitted from the light emitting point of the light emitting element array,
A half mirror that divides light passing through the imaging optical system into two directions;
A light receiving element array for receiving one of the divided lights;
A light receiving element that receives the other divided light and has a light receiving portion with an area in which the moving light emitting point image is accommodated , and
Evaluating the transfer operation of the light emitting point of the light emitting element array by detecting the light output from the light emitting point by the output of the light receiving element array,
Measure the light quantity distribution of the light emitting element array in a time division by the output of the light receiving element,
An inspection apparatus for a light-emitting element array. In the light emitting element array inspection apparatus for measuring the light emission distribution, the light emitting point transfer operation of the light emitting element array having the light emitting points that are sequentially turned on,
An imaging optical system for focusing the light emitted from the light emitting point of the light emitting element array,
A light receiving element array for receiving light passing through the imaging optical system;
A light receiving element that receives light emitted from the light emitting point of the light emitting element array without passing through the imaging optical system ;
Evaluating the transfer operation of the light emitting point of the light emitting element array by detecting the light output from the light emitting point by the output of the light receiving element array,
Measure the light quantity distribution of the light emitting element array in a time division by the output of the light receiving element,
An inspection apparatus for a light-emitting element array.   3. The light-emitting element array inspection apparatus according to claim 1, wherein the light-receiving element array is a one-dimensional light-receiving element array.   3. The light-emitting element array inspection apparatus according to claim 1, wherein the light-receiving element array is a two-dimensional light-receiving element array. 5. The light emitting element according to claim 1 , wherein a transfer operation of the light emitting point of the light emitting element array is evaluated by detecting a light output from the light emitting point that is sequentially and sequentially turned on. Array inspection equipment. 5. The transfer operation of the light emitting points of the light emitting element array is evaluated by detecting a light output from the light emitting points that are sequentially lit at least every other one. 5 . Inspection device for light emitting element array. In the evaluation of the transfer operation of the light emitting point, a threshold is set for the detected light output from the light emitting point, and the number of peaks exceeding the threshold becomes the number of light emitting points lit. The light-emitting element array inspection apparatus according to claim 1, wherein the light-emitting element array inspection apparatus is evaluated as normal.

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