JPS62108587A - 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 selecting circuit selecting compensating data memorized in a memory means and a compensating circuit controlling a drive circuit on the basis of the selected compensating data. CONSTITUTION:A memory means 3 is constituted of three ROMs 3a-3c, each ROM previously memorizes compensating data corresponding to the time characteristics of an LED array 5, and predetermined compensating data are used for compensating the amount of light. Signals are outputted by a conduction timer 7 every time the LED array 5 is conducted for a fixed time, and the ROMS 3a-3c are selected by changing over a selector 8. The selected compensating data are inputted to a compensating circuit 2, a picture signal is compensated on the basis of the compensating data, and a compensating signal is outputted to a drive circuit 4. Power inputted to the drive circuit 4 is controlled by the compensating signal, and fed to the LED array 5. Accordingly, even when the distribution of the amount of light of each element for the LED array changes, the dispersion of the amount of light corresponding to the change sections is compensated, thus keeping the distribution of the amount of light uniform at all times.

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. 2 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 15 composed of ED elements, a drive circuit 14 that drives the LED array 15, a ROM 13 that stores correction data for correcting the light amount of the LED array 15, and the correction data and image signals stored in the ROM 13. It includes a correction circuit 12 that creates a correction signal from an image signal input from an input terminal 11 and outputs this correction signal to a drive circuit 14, and selectively drives an LED array 15 in response to the image signal.

In this LED array light amount variation correction device, the power input to the drive circuit 14 via the power input terminal 16 is corrected based on a correction signal and then supplied to the LED array 15. In this way, the light intensity distribution of the LED array is corrected to make the light intensity distribution uniform, which is caused by the difference in the characteristics of each LED element.

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 LED 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 light amount distribution regardless of the array energization time.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention includes a storage means that stores in advance a plurality of data for correcting the light amount of the LED array according to the elapse of the energization time; A selection circuit that selects data that meets predetermined conditions from the data for
and a correction circuit that controls the array drive circuit.

The storage means may be composed of a plurality of circuits, for example, and each circuit may store different light amount correction data in advance. In this case, the selection circuit can select the light amount correction data by switching the circuit.

As the LED array energization time elapses, the selection circuit selects light amount correction data corresponding to the elapsed time from the storage means. Based on the selected light amount correction data, the correction circuit controls the drive circuit to correct the light amount of the LED array.

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 5 composed of ED elements, a drive circuit 4 for driving the LED array 5, a storage means 3 storing a plurality of correction data for correcting the light amount of the LED array 5,
A selector 8 is connected to the energization timer 1 and selects predetermined correction data from the storage means 3 according to the measured value of the energization timer 7. and a correction circuit 2 which outputs a correction signal based on these input data, and the correction signal outputted from the correction circuit 2 causes the drive circuit 4 to
is now under control.

In this embodiment, the storage means 3 includes three ROMs 3a and 3b.

3C, each of which has stored in advance correction data according to the time characteristics of the LED array 5, and the selector 8 is configured with these ROMs 3a, 3b, 3c.
O') can be selected and predetermined correction data can be used for light amount correction.

The correction data stored in the ROMs 3a, 3b, 3c is based on the LFJ as the energization time of the LED array 5 elapses.
) is set in anticipation of changes in the light intensity distribution of each element in the array.

An example of a method for predicting changes in light intensity distribution is to first turn on the lights for several tens of hours, and then use statistical methods to predict the light intensity distribution 100 hours later and 200 hours later based on changes in the scene distribution during that period. There is a method to set the correction data in this way.

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

When the device begins to be operated, the energization timer 7 is activated. The energization timer 7 outputs a signal every time the LED array 5 is energized for a predetermined period of time. Note that this predetermined time is defined as the amount of light distribution of the LED array 5 changing due to changes over time;
This is the energization time within a range in which a phenomenon in which the light amount variation correction based on the initial correction data cannot be performed normally and the light amount variation tolerance value is exceeded does not occur. Specifically, it has been found through experiments that this value may be approximately 100 hours.

When there is an output from the energization timer 7, the selector 8 selects RC) M3a, 3b, and 3c which have stored correction data corresponding to the output value.

The selected correction data is input to the correction circuit 2, the image signal is corrected based on this correction data, and the correction signal is output to the drive circuit 4. This correction signal controls the power input to the drive circuit 4 via the power input terminal 6, and the thus controlled power is supplied to the LED array 5. As a result, the LED array 5 emits light with a uniform light amount distribution.

In this embodiment, a case has been described in which the number of memory circuits constituting the memory means is three, but the number is not limited to this, and may be two or four or more. By increasing the number in this way, more accurate control can be performed.

Further, depending on the combination of selection circuits, one memory circuit may be used, and a plurality of correction data may be stored in this memory circuit.

Furthermore, in this embodiment, the timing at which the memory circuit is switched by the selector is determined by the measurement of the energization timer.
The method is not limited to this method.

Effects of the Invention As is clear from the above explanation, according to the American invention, a plurality of correction data are stored in the storage means, and appropriate correction data is selected from these correction data by a selection circuit according to the elapse of the LED array energization time. Since the LED light intensity is corrected based on this correction data, L
Even if the light amount distribution of each element of the ED array changes, light amount variation correction corresponding to the change is performed, and the light amount distribution can always 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, and FIG. 2 is a schematic block diagram showing a conventional LED array light amount variation correction device.
FIG. 2 is a schematic block diagram showing an example of an array light amount variation correction device. 2... Correction circuit, 3... Storage means, 3a, 3b, 3
c... ROM14... Drive circuit, 5... LED array, 7... Energization timer, 8... Selector.

Claims (1)

[Claims] an LED array composed of a plurality of LED elements; a drive circuit for driving the LED array; and a storage means storing a plurality of types of correction data according to the elapse of energization time for correcting the light amount of the LED array; An LED array light amount variation correction device comprising a selection circuit that selects correction data stored in the storage means in accordance with the elapse of energization time, and a correction circuit that controls the drive circuit based on the selected correction data. .