JPS62108586A - Compensator for dispersion of amount of light from led array - Google Patents

Abstract

PURPOSE:To equalize the distribution of the amount of light by mounting a compensating circuit controlling a drive circuit on the basis of compensating data and a compensating-data varying means measuring the amount of light from an LED array and varying compensating data for a memory means on the basis of the measured value. CONSTITUTION:Compensating data from a compensating-data memory circuit 11 are inputted from a picture-signal input terminal 1 and processed by a compensating circuit 3 together with a picture signal from a selector 2, and inputted to a drive circuit 5, and power inputted from a power input terminal 4 is fed to an LED array 6 on the basis of the signal inputted from the compensating circuit 3. When a signal is outputted by a conduction timer 12, the selector 2 is changed over, a picture-signal generating circuit 13 for measuring the amount of light is connected, and a picture signal for measurement light-emitting the LED array 6 in succession at every one element is transmitted over a light-amount measuring instrument 7. When the amount of light of all LED elements is measured completely, the data of the compensating-data memory circuit 11 are rewritten anew on the basis of the whole LED element light-amount measuring data in a RAM9, and used for compensating the dispersion of the amount of light of the LED array 6. Accordingly, the distribution of the amount of light can be kept uniform at all times regardless of the conduction time period of the LED array.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an LED array light intensity variation correction device used in optical printers and the like.

BACKGROUND OF THE INVENTION FIG. 3 is a schematic block diagram showing an example of a conventional LED array light amount variation correction device.

This LED array light amount variation correction device has a plurality of L
An LED array 56 composed of ED elements, a drive circuit 55 that drives the LED array 56, an RCMsr that stores correction data for correcting the light amount of the LED array 56, and correction data and image signals stored in a ROM 57. A correction circuit 53 is provided which creates a correction signal from an image signal inputted from an input terminal 51 and outputs this correction signal to a drive circuit 55, and selectively drives an LED array 56 in response to the image signal.

In this LED array light amount variation correction device, the power input to the drive circuit 55 via the power input terminal 54 is corrected based on a correction signal and then supplied to the LED array 56. In this way, variations in light amount of the UΦ array caused by differences in characteristics of each LED element are corrected, and the light amount distribution is made uniform.

Problems to be Solved by the Invention However, according to the conventional LED array light intensity variation device described above, although the light intensity variation correction is properly performed at the beginning of use, the correction is no longer performed properly as time passes. There has been a problem in that variations in the amount of light from the LED array gradually increase.

Experiments have revealed that this problem occurs for the following reasons.

In other words, as the IJD array energization time elapses, the characteristics of each element of the LED array change, and the degree of change is different for each element, so even though the light intensity distribution of each element of the LED array changes. Since constant correction data based on the light intensity distribution before change is used, a problem arises in that appropriate light intensity variation correction is not performed as described above.

The present invention has been made in view of the above-mentioned problems.
It is an object of the present invention to provide an LED array light amount variation correction device that can always maintain a uniform sight distribution regardless of the D array energization time.

Means for Solving the Problems In order to achieve the above object, the present invention includes a rewritable storage means storing correction data for correcting the light amount of the LED array, and an LED array drive circuit based on the correction data. A correction circuit that controls and measures the amount of light from the LED array.
and correction data changing means for changing the correction data in the storage means based on this measured value.

The correction data changing means includes, for example, a measurement image signal generation circuit that supplies a measurement image signal to the LED array via a correction circuit and a drive circuit, and a light intensity measurement circuit that measures the light amount of the LED array based on this measurement image signal. and a data rewriting circuit that outputs a rewriting signal corresponding to the measured value to the storage means.

Operation When this device starts to be used, the correction data stored in the storage means is the data set in advance, and the image signal is corrected using this data to cause the LED array to emit light.

Then, when a predetermined energization time has elapsed, the correction data changing means is activated to measure the LFJ array light amount based on the measurement image signal. The correction data in the storage means is changed based on this measured value.

Embodiment FIG. 1 is a schematic block diagram showing an LED array light amount variation correction device according to an embodiment of the present invention.

This LED array light amount variation correction device has a plurality of L
An LED array 6 composed of ED elements, a drive circuit 5 that drives the LED array 6, a rewritable correction data storage circuit 11 that stores correction data for correcting the light amount of the LED array 6, and a correction data storage circuit 11 that stores correction data for correcting the light amount of the LED array 6. a correction circuit 3 that controls the drive circuit 5 based on this; a correction data changing means 20 that measures the amount of light from the LED array 6 and changes the correction data in the correction data storage circuit 11 based on the measured value; and an image signal input terminal 1. a selector 2 that switches between an image signal inputted through the image signal and a measurement image signal of a light intensity measurement image signal generation circuit 13 to be described later, and outputs one of the signals to the correction circuit 3; The power supply timer 12 is connected to the power supply timer 12 and controls the time of each of the power supply timers.

In this embodiment, the correction data changing means 20 includes a light amount measurement image signal generation circuit 13 that supplies a measurement image signal to the LED array 6 via the selector 2, and a light amount measurement image signal generation circuit 13 that sequentially processes each element based on this measurement image signal. A light intensity measuring device 7 that measures the light intensity of the emitting LED array 6, an A/D circuit 8 that converts the measured light intensity into a digital signal, a RAM 9 that temporarily stores the signal from the NΦ circuit 8, and a A data rewrite circuit 10 is provided which outputs a rewrite signal based on the light amount measurement data of all LED elements stored in the RAM 9 to the correction data storage circuit 11 when the light amount measurement is completed.

The light amount measuring device 7 can be realized, for example, by the configuration shown in FIG. This light amount measuring device 7 consists of: (1) LEDs that emit light sequentially for each element;
An optical sensor 7a that receives light from the array 6 and converts it into an electrical signal, and an amplifier 7 that amplifies the electrical signal of the optical sensor 7a.
b. The optical sensor 7a is configured to mechanically scan and receive light in synchronization with the measurement image signal output from the light amount measurement image signal generation circuit 13. in this case,
Since the area of the light-receiving portion of the optical sensor 7a is usually several thousand times larger than the cross-sectional area of the light spot of one LED element, the mechanical accuracy in scanning is not particularly problematic and a simple configuration can be achieved.

Further, the correction data storage circuit 11 is, for example, an electrically rewritable so-called EPROM (erasable a
This can be realized using ndprogramrrnable ROM).

The operation of the LED array light amount variation correction device configured as above will be explained.

When this device is operated, first, the correction data storage circuit 1
1 correction data is input from the image signal input terminal 1 and processed by the correction circuit 3 together with the image signal passing through the selector 2, and is input to the drive circuit 5.

The drive circuit 5 supplies power input from the power input terminal 4 to the LED array 6 based on the signal input from the correction circuit 3. At this time, the power applied to each LED element is controlled based on the correction information, and the light intensity variation of the LED array 6 is corrected. And by this, the LED
The array 6 emits light with a uniform light amount distribution.

At this time, power is selectively supplied to each LED element according to the image signal ζ, and any LED element can be caused to emit light.

The energization timer 12 outputs a signal every time the LED array 6 is energized for a predetermined period of time. Note that this predetermined time is within a range in which the light intensity distribution of the LED array 6 changes due to changes over time, the light intensity variation correction based on the initial correction data cannot be performed normally, and the phenomenon in which the light intensity variation exceeds the allowable value occurs. is the energization time. Specifically, this value is
Based on experimental results, it has been found that approximately 100 hours is sufficient.

After this, the operation when the energization timer 7 outputs a signal will be explained.

When the energization timer 7 outputs a signal, the selector 2 is switched and the image signal generation circuit 13 for light amount measurement is connected. One LED array 6 is connected to the image signal generation circuit 13 for light intensity measurement.
A measurement image signal that causes each element to sequentially emit light is output, and is supplied to a light amount measuring device 7 via a correction circuit 3 and a drive circuit 5. The light amount measuring device 7 measures the amount of light for each LED element. The measured light amount for each LED element is determined by the N circuit 8.
The signal is converted into a digital signal and stored in the RAM 9.

When the measurement of the light intensity of all the LED elements is completed, the data in the correction data storage circuit 11 is rewritten by the data rewriting circuit 10 based on the measurement data of the light intensity of all the LED elements stored in the RAM 9. The data rewritten in this manner is then used to correct variations in light amount of the LED array 6 in the same manner as described above.

In this embodiment, the rewriting timing of the correction data is created using the energization timer 12, but the present invention is not necessarily limited to this.

Effects of the Invention As is clear from the above explanation, according to the present invention, the correction data for light amount variation is changed according to the energization time of the LED array, so the light amount is always maintained regardless of the energization time of the LED array. Distribution can be kept uniform.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an LED array light amount variation correction device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing an example of a light amount measuring device of the LED array light amount variation correction device, and FIG. FIG. 2 is a schematic block diagram showing an example of a conventional LED array light amount variation correction device. 2... Selector, 3... Correction circuit, 5... Drive circuit, 6... LED array, 7... Light amount measuring device, 10
. . . data rewriting circuit, 11 . . . correction data rewriting circuit, 12 . . . energization timer, 20 . . . correction data changing means. Name of agent: Patent attorney Toshio Nakao (1 person)
2 Shi! Figure 3

Claims (1)

[Claims] an LED array composed of a plurality of LED elements; a drive circuit for driving the LED array; a rewritable storage means storing correction data for correcting the light amount of the LED array; a correction circuit that controls the drive circuit; and a correction circuit that measures the amount of light from the LED array;
and correction data changing means for changing the correction data in the storage means based on the measured value.