JPH0667619A - Method and device for light emission control - Google Patents

Abstract

PURPOSE:To control light emitting elements such as LEDs to uniform light emission intensity respectively irrelevantly to the number of light emitting elements which illuminate as to the light emission device which has the light emitting elements. CONSTITUTION:An illuminating light emitting element quantity calculating circuit 5 calculates the number of light emitting elements which are turned on in light emitting element arrays 4a, 4b having light emitting elements to be turned on selectively, a strobe signal ST generated corresponding to the number of the light emitting elements to be turned on in the light emitting element arrays 4a, 4b...4n is generated by a variable pulse width generating circuit 6, and drivers 3a, 3b,...3n which drive the light emitting element arrays 4a, 4b...4n are controlled with the strobe signal ST.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emission control method and apparatus, and is particularly suitable for stabilizing the light emission intensity when a large number of light emitting diodes such as an LED (light emitting diode) printer is selectively driven. The present invention relates to a light emission control method and device.

[0002]

2. Description of the Related Art Conventionally, an optical printer for recording information by irradiating light is known, but an LED printer having a large number of LEDs arranged in a row to form a latent image is one of them. Is one. In the case of this LED printer, it is necessary to arrange a large number of LEDs in order to improve the print quality, particularly in order to increase the resolution, while in order to eliminate the uneven density, the large number of LEDs should be uniform at any time. It is necessary to turn on with the emission intensity of.

FIG. 5 is a block diagram of an apparatus for realizing a conventional light emission control method used for driving an LED of such an LED printer. In the figure, 4a, 4b,
... 4n is a light emitting element array in which a plurality of LEDs are arranged in a row and a line-shaped optical image is formed in an LED printer or the like by the LEDs that are selectively turned on and driven to expose a photosensitive portion (not shown) to form a latent image. 1n are serially connected shift registers 2a, 2b, ..., 2n serially driven by serially inputting light emitting element selection data D by clock pulse CLK, and 2n are serially driven shift registers 1a, 1n, latches 3a, 3b, ..., 3n for taking out and holding data from the parallel output of 1n at a predetermined timing, and latches 2a, 2
b, ..., 2n LEDs for selectively driving the LEDs of the light emitting element rows 4a, 4b, ..., 4n based on the data held in 2n
A driver having a switching element such as a transistor arranged corresponding to each of them, 9 generates a strobe signal ST having a constant pulse width and controls the switching elements of the drivers 3a, 3b, ... 4b,
A constant pulse width generation circuit that outputs a drive pulse to 4n at a predetermined timing and controls the drive pulse width to a constant pulse width.

The operation of the above arrangement will be described below.

In the LED printer, the light emitting element array 4a,
4n are arranged in series in correspondence with a photosensitive portion for forming a latent image (not shown), and a line-shaped optical image is generated by selectively emitting light from each LED to generate a corresponding photosensitive portion. The area is exposed to form a latent image. on the other hand,
The photosensitive unit (not shown) is connected to the light emitting element arrays 4a, 4b, ..., 4
4n is moved in a direction perpendicular to the direction in which n is arranged, or conversely, while the light emitting element arrays 4a, 4b, ... This makes it possible to form a planar latent image pattern on the photosensitive portion. Incidentally, the photosensitive portion can visualize the latent image by a well-known electrophotographic process, silver salt photographic process, or the like, and finally a print result corresponding to the input data can be obtained.

The image to be printed is the shift register 1a, 1 in the form of serial data as the light emitting element selection data D.
b, ..., 1n, this data is input to the shift registers 1a, 1b, based on the clock pulse CLK.
... serially input to 1n. Latches 2a, 2
b, ..., 2n are shift registers 1a, 1b ,.
1n parallel outputs are used as shift registers 1a, 1b, ...
, The light emitting element arrays 4a, 4b are latched at an appropriate timing when the data for one line is prepared for 1n.
The data for making 4n emit light, that is, the signals for selectively driving the LEDs of the light emitting element arrays 4a, 4b, ..., 4n to form a linear optical image are held. On the other hand, the constant pulse width generation circuit 9 outputs a strobe signal ST having a constant pulse width to the drivers 3a, 3b, ..., 3n at a time corresponding to the latch timing of the latches 2a, 2b ,.
, 3n turn on the switching elements by the strobe signal ST to output drive signals based on the data of the latches 2a, 2b, ..., 2n to the light emitting element arrays 4a, 4b ,. Give to 4n. As a result, the LEDs of the light emitting element arrays 4a, 4b, ..., 4n are selectively driven to emit light in accordance with the data latched by the latches 2a, 2b ,.

Through the above operations, the light emitting element array 4
.., 4n generate a linear light image, and a latent image is formed on a photosensitive portion (not shown) based on the linear light image. Next, by giving new light emitting element selection data D to the shift registers 1a, 1b, ..., 1n and changing the relative position to the photosensitive portion to form a new linear latent image, the operation is repeated. Finally, a planar latent image can be formed on the photosensitive portion (not shown). Then, by making the latent image of the photosensitive portion visible, it is possible to obtain a print output in which a planar image is formed, and an operation as a printer is performed to obtain a print image output based on the light emitting element selection data D. Can be made.

[0008]

Since the conventional light emission control method and device are configured as described above, the light emitting element arrays 4a, 4b, ... Required for forming a line-shaped light image.
The number of light emitting elements of the 4n LED varies depending on the light emitting element selection data D for each line. However, since a plurality of light emitting element arrays 4a, 4b, ..., 4n are connected in series, and the number of LEDs contained therein is very large, it is necessary when the number of LEDs to be lit is large or small. The amount of current applied will be extremely different. That is, when the number of LEDs to be turned on is large, each light emitting element row 4
a, 4b, ..., 4n, current supply capacity and voltage drop of the wiring from the power supply to the LED cannot be ignored.
The current flowing through the two LED elements becomes small and the emission intensity decreases. FIG. 6 shows light emitting element arrays 4a and 4
b, ... 4n is a characteristic diagram in which the number of LEDs to be turned on at the same time and the amount of light emission per LED element correspond to each other. However, as the number of light emitting elements that emit light increases, The amount of light emission is decreasing. For this reason,
When a line-shaped optical image is collected to form a planar latent image, the number of LEDs that emit light differs for each line, so the exposure amount for forming the latent image varies for each line, There is a problem that the final image quality obtained as a print output is deteriorated.

The present invention solves the problems of the prior art as described above, and in a light emitting device having a plurality of light emitting elements such as LEDs, the light emission intensity of each light emitting element is irrespective of the number of light emitting elements to be selectively turned on. It is an object of the present invention to provide a light emission control method and device capable of uniformly controlling light emission.

[0010]

In order to achieve the above object, the present invention provides a light emission control method according to claim 1.
A first step of giving the number of light emitting elements to be turned on by a light emitting means having a plurality of light emitting elements to be selectively turned on, and a drive signal formed corresponding to the number of light emitting elements to be emitted by the light emitting means. And a second step of driving the light emitting means according to the second step.

In order to achieve the above object, the present invention provides
The light emission control method according to claim 2, wherein a first step of giving the number of light emitting elements to be turned on by a light emitting means having a plurality of light emitting elements to be selectively turned on, and a light emitting element to be emitted by the light emitting means A second step of generating a drive signal having a pulse width corresponding to the number, and thereby driving the light emitting means;
The present invention provides a light emission control device.

In order to achieve the above object, the present invention provides
The light emitting control method according to claim 3, wherein a first step of giving the number of light emitting elements to be turned on by a light emitting means having a plurality of light emitting elements to be selectively turned on, and a light emitting element to be emitted by the light emitting means A second step of driving the light emitting means by generating a long drive signal when the number of light emitting elements is large and a short drive signal when the number of light emitting elements is small. A light emission control device having the same is provided.

In order to achieve the above object, the present invention provides
The light emitting control method according to claim 4, wherein a first step of calculating the number of light emitting elements of the light emitting means to be driven to be turned on from data for driving a light emitting means having a plurality of light emitting elements to be selectively turned on. And a second step of driving the light emitting means by generating a drive signal having a pulse width corresponding to the number of light emitting elements to be driven by the light emitting means, thereby providing a light emission control device. .

In order to achieve the above object, the present invention provides
The light emission control device according to claim 5, wherein a light emitting means having a plurality of light emitting elements which are selectively turned on, and a light emitting element number setting means for giving the number of light emitting elements turned on by the light emitting means,
A light emission control device comprising: a control unit that changes a drive signal given to the light emitting unit based on the number of light emitting units given by the light emitting unit number setting unit.

In order to achieve the above object, the present invention provides
The light emission control device according to claim 6, further comprising: a light emitting means having a plurality of light emitting elements which are selectively turned on; and a light emitting element number setting means for giving the number of light emitting elements turned on by the light emitting means.
And a pulse width changing means for changing the pulse width of a drive signal given to the light emitting means based on the number of light emitting elements given by the light emitting element number setting means.

In order to achieve the above object, the present invention provides
The light emission control device according to claim 7, wherein a light emitting means having a plurality of light emitting elements that are selectively turned on, a driving means that selectively drives the light emitting elements of the light emitting means, and a lighting drive by the driving means. A light emitting element number setting means for giving the number of light emitting elements of the light emitting means, and a pulse width variable for changing the pulse width of a drive signal given to the driving means based on the number of light emitting elements given by the light emitting element number setting means. And a light emission control device including the means.

In order to achieve the above object, the present invention provides
The light emission control device according to claim 8, wherein the light emitting means has a plurality of light emitting elements that are selectively turned on, a driving means that selectively drives the light emitting elements of the light emitting means, and the light emission provided to the driving means. The light emitting element number calculating means for calculating the number of light emitting elements of the light emitting means to be driven to be lighted by the driving means based on the data designating the light emitting element to be lighted by the means, and the light emitting element number calculating means. A light emission control device comprising: pulse width varying means for changing the pulse width of a drive signal given to the driving means based on the number of light emitting elements.

In order to achieve the above object, the present invention provides
The light emission control device according to claim 9, wherein the light emitting means has a plurality of light emitting elements that are selectively turned on, a driving means that selectively drives the light emitting elements of the light emitting means, and the light emission provided to the driving means. The light emitting element number calculating means for calculating the number of light emitting elements of the light emitting means to be driven to be lighted by the driving means based on the data designating the light emitting element to be lighted by the means, and the light emitting element number calculating means. A light emission control device comprising: a pulse width calculation means for calculating the pulse width of a drive signal to be given to the drive means based on the number of light emitting elements.

In order to achieve the above object, the present invention provides
The light emission control device according to claim 10, wherein a plurality of light emitting means having a plurality of light emitting elements that are selectively turned on and a light emitting element of the light emitting means are selectively provided corresponding to the input data. Driving means for driving the driving means, and the number of light emitting elements of the light emitting means to be driven for lighting is calculated based on input data given to each driving means, and the driving means drives the driving means based on the obtained number of light emitting elements. A light emission control device comprising: a control unit provided for each drive unit to change the pulse width of a signal.

In order to achieve the above object, the present invention provides
The light emission control device according to claim 11, wherein light emitting diode array means having a plurality of light emitting diodes that are selectively turned on, light emitting diode number setting means for giving the number of light emitting diodes to be turned on by the light emitting diode array means, The light emission control includes pulse width changing means for changing the pulse width of the drive signal given to the light emitting diode array means so as to become longer as the number of light emitting diodes increases, based on the number of light emitting diodes given by the light emitting diode number setting means. A device is provided.

[0021]

According to the above means, in the light emission control method according to the first aspect, in the first step, the number of light emitting elements to be turned on is given by the light emitting means having a plurality of light emitting elements to be turned on selectively, In the second step, drive signals are formed corresponding to the number of light emitting elements obtained in the first step, and the driving signals are generated to drive the light emitting means.

In the above means, in the light emission control method according to the second aspect, in the first step, the number of light emitting elements to be turned on by the light emitting means having a plurality of light emitting elements to be turned on selectively is given, In the second step, a drive signal having a pulse width corresponding to the number of the light emitting elements is generated corresponding to the number of the light emitting elements obtained in the first step, thereby driving the light emitting means.

In the above means, in the light emission control method according to the third aspect, in the first step, the number of light emitting elements to be turned on by the light emitting means having a plurality of light emitting elements to be turned on selectively is given, and In the process (1), a long drive signal is generated when the number of light emitting devices is large, and a short drive signal is generated when the number of light emitting devices is small according to the number of light emitting devices obtained in the first process. To drive the light emitting means.

In the above-mentioned means, in the light emission control method according to the fourth aspect, in the first step, the light emission to be driven to be turned on from data for driving the light emitting means having a plurality of light emitting elements which are selectively turned on. Driving a pulse width corresponding to the number of light emitting elements to be driven by the light emitting means in a second step according to the number of light emitting elements obtained in the first step A signal is generated, which drives the light emitting means. In the above means, in the light emission control device according to claim 5, the number of light emitting elements selectively turned on in the light emitting means is given by the light emitting element number setting means, and the control means emits light emitted from the light emitting element number setting means. The drive signal given to the light emitting means is changed based on the number of elements.

In the above-mentioned means, in the light-emission control device according to the sixth aspect, the number of light-emitting elements selectively turned on in the light-emitting means is given by the light-emitting element number setting means, and in the pulse width varying means, the light-emitting element number setting means. The pulse width of the drive signal given to the light emitting means is changed based on the number of the light emitting elements given from.

In the above-mentioned means, in the light-emission control device according to the seventh aspect, when the light-emitting elements of the light-emitting means are selectively driven by the drive means, the number of light-emitting elements to be driven to light by the drive means is set. The pulse width varying means changes the pulse width of the drive signal given to the driving means based on the number of the light emitting elements given by the means for setting the number of light emitting elements.

In the above-mentioned means, in the light-emission control device according to the eighth aspect, when the light-emitting element of the light-emitting means is selectively driven by the driving means, the light-emitting element number calculating means drives the lighting based on the data designating the light-emitting element. The number of light emitting elements to be calculated is calculated, and the pulse width varying means changes the pulse width of the drive signal given to the driving means based on the number of light emitting elements given by the light emitting element number calculating means.

In the above-mentioned means, in the light-emission control device according to the ninth aspect, when the light-emitting element of the light-emitting means is selectively driven by the drive means, the light-emitting element number calculation means is driven to turn on based on the data designating the light-emitting element. The number of light emitting elements to be calculated is calculated, and the pulse width calculation means calculates the pulse width of the drive signal to be given to the driving means based on the number of light emitting elements given by the light emitting element number calculation means. give.

In the above-mentioned means, in the light-emission control device according to the tenth aspect, the drive means provided for each of the plurality of light-emitting means selectively drives the light-emitting element of the light-emitting means in response to input data. The number of light emitting elements to be driven for lighting is calculated based on the input data given by the control means provided for each driving means, and the pulse width of the drive signal by the driving means is changed based on the obtained number of light emitting elements. .

In the above-mentioned means, in the light-emission control device according to claim 11, the number of light-emitting diodes selectively turned on in the light-emitting diode array means is given by the light-emitting diode number setting means, and is given by the light-emitting diode number setting means. Based on the number of light emitting diodes, the pulse width varying means changes the pulse width of the drive signal given to the light emitting diode array means so as to become longer as the number of light emitting diodes increases.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an apparatus for realizing a light emission control method according to an embodiment of the present invention. In the figure, 5 is a light emitting element row 4a from the light emitting element selection data D given to the shift registers 1a, 1b, ..., 1n.
4b, ..., A lighting light emitting element number calculation circuit that calculates the number of lighting LEDs for one line in 4n and outputs lighting light emitting element number data NUM, and 6 is a lighting light emitting element number data NUM from the lighting light emitting element number calculation circuit 5. Driver 3 based on
.., 3n is a variable pulse width generation circuit having a function of changing the pulse width of the strobe signal ST. Incidentally, the variable pulse width generation circuit 6 has a function of lengthening the pulse width of the strobe signal ST as the lighting light emitting element number data NUM increases.

The operation of the above-described structure will be described below.

The light emitting element selection data D corresponding to the image to be printed is in the form of serial data in the shift registers 1a and 1a.
b, ..., 1n, this data is based on the clock pulse CLK, and the shift registers 1a, 1b,
... serially input to 1n. Latches 2a, 2
b, ..., 2n are shift registers 1a, 1b ,.
, 1n parallel outputs to shift registers 1a, 1b,
... The light emitting element arrays 4a and 4a are latched at appropriate timings when the data for one line is prepared for 1n.
4n, that is, data for causing 4n to emit light, that is, a signal for selectively driving the LEDs of the light emitting element arrays 4a, 4b, ..., 4n to form a linear optical image is held.

In parallel with the above-described operation, in the lighting light emitting element number calculation circuit 5, the light emitting element row is generated based on the light emitting element selection data D corresponding to the data secured in the latches 2a, 2b, ..., 2n. 4a, 4b, ... Calculate the number of LEDs to be driven by 4n. This corresponds to the number of parallel data "1" or "0" to be latched by the latches 2a, 2b, ..., 2n, for example, and the light emitting elements serially input to the shift registers 1a, 1b ,. It is obtained by counting the number of "1" or "0" of the selection data D. The number of lit light emitting elements obtained as described above is output to the variable pulse width generation circuit 6 as lit light emitting element number data NUM.

The signals for selecting the LEDs to be emitted in the light emitting element arrays 4a, 4b, ...
, 2n, the variable pulse width generation circuit 6 outputs the strobe signal ST to the drivers 3a, 3b, ..., 3n. This strobe signal S
In the variable pulse width generation circuit 6, T is controlled to a long pulse width when the number of light emitting elements indicated in the lighting light emitting element number data NUM is long, and to a short pulse width when the number of light emitting elements is small. The driver 3a, 3b, ..., 3n turns on the switching element by the strobe signal ST to give a drive signal based on the data of the latches 2a, 2b, ..., 2n to the light emitting element arrays 4a, 4b ,. 4n, a long drive signal is given when the number of light emitting elements in the light emitting element rows 4a, 4b, ..., 4n is large, and a short drive signal is provided when the number of light emitting elements in the light emitting element rows 4a, 4b ,. Will be given.

As a result, the light emitting element arrays 4a, 4b, ...
When the number of light emitting elements of 4n is large, a long drive signal is given to each light emitting element, so that the emission intensity is enhanced and the decrease in emission intensity due to the increase in the number of lighting is compensated. On the other hand, when the number of light emitting elements in the light emitting element rows 4a, 4b, ..., 4n is small, a short drive signal is given to each light emitting element, so that the light emission intensity is reduced as compared with the case where the pulse width is large. As a result, the increase in the emission intensity due to the decrease in the number of lightings is compensated. as a result,
The light emission intensity of each light emitting element is controlled uniformly, regardless of the number of light emitting elements in the light emitting element rows 4a, 4b, ..., 4n.

As described above, the light emitting element arrays 4a, 4b,
A line-shaped optical image is generated at 4n, a latent image is formed on a photosensitive portion (not shown) based on the line-shaped optical image, and then new light-emitting element selection data D is added to the shift registers 1a, 1
b, ..., 1n, by repeating the operation of changing the relative position to the photosensitive portion to form a new line-shaped latent image, finally a planar latent image is formed on the photosensitive portion (not shown). However, in this case, the number of light emitting elements to be turned on in the light emitting element rows 4a, 4b, ..., 4n corresponding to the light emitting element selection data D given as different data for each line is naturally different for each line. Come
Since the light emission intensity of each light emitting element can be made uniform regardless of the number of light emitting elements, the exposure amount of all lines can be kept constant. As a result, it is possible to reduce uneven density and improve print quality.

Now, the operation of the variable pulse width generating circuit 6 will be described in more detail.

As described above, the light emission intensity of each light emitting element decreases as the number of light emitting elements to be turned on in the light emitting element rows 4a, 4b, ..., 4n increases. It is well known that the light exposure amount of the light emitting element can be compensated by extending the time. In other words, the exposure dose is the emission intensity and exposure time,
That is, it is determined by the product of the lighting times. Here, it is assumed that the light emission intensity I can be expressed by I (N) as a function of the number N of light emitting elements that are simultaneously turned on. On the other hand, since the variable pulse width generation circuit 6 generates the strobe signal ST having the pulse width T corresponding to the number N of light emitting elements, the pulse width can be represented by T (N). On the other hand, the exposure amount E can be represented by the product of the emission intensity I (N) and the pulse width T (N) which is the exposure time, so that E = I (N) XT (N) (1)

Therefore, the pulse width T (N) is set so that T (N) = E / I (N) (2).
The exposure amount E can be made constant by changing in accordance with the number N of light emitting elements of b, ..., 4n. The variable pulse width generation circuit 6 generates a strobe signal ST having a pulse width corresponding to the number of light emitting elements of the light emitting element rows 4a, 4b, ..., 4n so as to satisfy the expression (2), which is variable in advance. It can be realized by the function set in the pulse width generating circuit 6 or by referring to a table. As a result, the light emitting element rows 4a, 4b, ...
In 4n, the resulting exposure amount can be kept constant by compensating the change in the light emission intensity by the change in the light emission time regardless of the number of light emitting elements that are simultaneously turned on.

FIG. 2 is a block diagram of an apparatus for realizing the light emission control method according to the second embodiment of the present invention. The difference between the configuration shown in FIG. 1 and the configuration shown in FIG. 1 is that instead of providing the lighting light emitting element number calculation circuit 5, the shift registers 1a, 1b,
The light emitting element number data NUM calculated in advance by a CPU or the like (not shown) in association with the light emitting element selection data D given to 1n or given to the variable pulse width generation circuit 6 is referred to in a table or the like. Is.

Even in the above-described structure, the light emitting element arrays 4a, 4b, ..., 4n are exactly the same as the structure shown in FIG.
Since the number of light emitting elements to be turned on is given to the variable pulse width generation circuit 6, the strobe signal ST having a pulse width corresponding to this is given to the drivers 3a, 3b ,.
3n, it becomes possible to compensate the change in the light emission intensity due to the change in the number of light emitting elements by the light emission time, and the exposure amount obtained by each light emitting element can be kept constant.

FIG. 3 is a block diagram of an apparatus for realizing a light emission control method according to the third embodiment of the present invention. In the figure, 7a, 7b, ..., 7n are light emitting element arrays 4
a, 4b, ..., 4n, the light emitting element selection data D is serially transferred based on the clock pulse CLK, and when the lighting data is prepared, the light emitting element selection data D is latched as parallel data and the light emitting element row 4a. 4b,
A light emitting element lighting control circuit for giving a driving signal to 4n, a light emitting element lighting control circuit 7a, 7b, ..., 7n
From the light emitting element selection data D given to
4n is a lighting time calculation circuit that calculates lighting time based on the number of light emitting elements that simultaneously emit light in a, 4b, ..., 4n, and supplies lighting time data TD to the light emitting element lighting control circuits 7a, 7b ,. Incidentally, the light emitting element lighting control circuits 7a, 7b, ...
4n has a function of controlling the pulse width of the drive pulse given to the light emitting element arrays 4a, 4b, ..., 4n. Further, the light emitting element lighting control circuits 7a, 7b, ..., 7n have lighting time data TD.
In addition to the strobe signal ST, a strobe signal ST is given as a signal having a constant pulse width as a signal instructing the drive timing of the light emitting elements of the light emitting element columns 4a, 4b, ..., 4n.

In the structure as described above, the light emitting element arrays 4a, 4b, ..., 4n are exactly the same as the structure shown in FIG.
The number of light emitting elements to be turned on is obtained from the light emitting element selection data D, and the lighting time of the corresponding light emitting element is calculated as the lighting time data TD in the lighting time calculation circuit 8, and this is calculated. 7a, 7b, ...
, 7n, so that in the light emitting element lighting control circuits 7a, 7b, ..., 7n, a lighting drive signal synchronized with the strobe signal ST with a pulse width corresponding to the lighting time data TD is arranged in the light emitting element rows 4a, 4b ,. 4n of light emitting elements to be lighted. As a result, it is possible to compensate the change in the light emission intensity of each light emitting element due to the change in the number of light emitting elements in the light emitting element rows 4a, 4b, ... It can be held constant.

In the configuration of FIG. 3, the lighting time calculation circuit 8
The lighting time data TD obtained in step 7 is used for the light emitting element lighting control circuit 7
, 7n, and a drive signal having a pulse width corresponding to this is given to the light emitting element lighting control circuits 7a, 7b ,.
, 7n, the lighting time data TD may be either a general data format or may be given in the form of a signal having a different time width. The light emitting element lighting control circuits 7a, 7b , 7n may be given as a signal form suitable when individually integrated with the light emitting element arrays 4a, 4b, ..., 4n.

By the way, the light emitting element lighting control circuits 7a, 7a, 7c, 7d, 7c, 7d are provided with the lighting time data TD as a signal of a format having a different time width.
b, ..., 7n, this element may be superimposed on the strobe signal ST, and signals having different time widths may be given as strobe signals. In this case, the strobe signal ST having a constant pulse width is input to the lighting time calculation circuit 8, and in the lighting time calculation circuit 8, the pulse width differs depending on the number of lighting light emitting elements and the lighting time data TD synchronized with the strobe signal ST is synthesized. Then, it is given to the light emitting element lighting control circuits 7a, 7b, ..., 7n as strobe signals.

FIG. 4 is a block diagram of an apparatus for realizing the light emission control method according to the fourth embodiment of the present invention. The configuration of FIG. 3 differs from that of FIG. 3 in that the lighting time calculation circuit 8 includes light emitting element lighting control circuits 7a, 7b, ..., 7n.
From the light emitting element selection data D given to
A lighting time based on the number of light emitting elements that simultaneously emit light in each of a, 4b, ..., 4n is individually calculated, and individual lighting time data TDa, TDb, ... Is assigned to the light emitting element lighting control circuits 7a, 7b ,. That is, it is configured to give TDn. Incidentally, the light emitting element lighting control circuits 7a, 7b, ...
Lighting time data TDa, TDb, ...
, TDn based on the light emitting element rows 4a, 4b, ...
It has a function of individually controlling the pulse width of the drive pulse given to 4n.

In the configuration as described above, the number of light emitting elements to be turned on by the light emitting element rows 4a, 4b, ..., 4n is obtained from the light emitting element selection data D, and the lighting time calculation circuit 8 is based on this. , TDn corresponding to each of the light emitting element arrays 4a, 4b, ..., 4n are calculated. Lighting time data TDa, T obtained in this way
, 7n are applied to the corresponding light-emitting element lighting control circuits 7a, 7b, ..., 7n, so that the light-emitting element lighting control circuits 7a, 7b ,. The light-emitting element rows 4a, 4b, which correspond to the synchronized lighting drive signals,
... 4n is applied to the light emitting element to be lighted. As a result, it is possible to compensate the change in the light emission intensity due to the change in the number of light emitting elements in each of the light emitting element rows 4a, 4b, ..., 4n by the light emitting time, and to keep the exposure amount obtained by each light emitting element constant. Can be held.

In the configuration of FIG. 4, the lighting time calculation circuit 8
Lighting time data TDa, TDb, ..., TDn obtained in
, 7n are given to the light emitting element lighting control circuits 7a, 7b, ..., 7n, and drive signals having a pulse width corresponding to each are generated in the light emitting element lighting control circuits 7a, 7b ,. , Lighting time data TDa, T
The format of Db, ..., TDn may be a general data format or may be given in the form of a signal having a different time width, and the light emitting element lighting control circuits 7a, 7b ,. .. may be given as a signal form suitable for the case where 4n is individually integrated into an integrated circuit.

Incidentally, the lighting time data TDa, TD
When TDn is given to the light-emitting element lighting control circuits 7a, 7b, ..., 7n as signals having different time widths, this element is superimposed on the strobe signal ST to give signals having different time widths as strobe signals. You may do it. In this case, the strobe signal ST having a constant pulse width is input to the lighting time calculation circuit 8, and the lighting time calculation circuit 8 changes the pulse width according to the number of lighting light emitting elements and lighting time data TDa synchronized with the strobe signal ST,
, TDn are combined and applied to the light emitting element lighting control circuits 7a, 7b, ..., 7n as strobe signals.

Further, in the configuration of FIG. 4, in one lighting time calculation circuit 8, the light emitting element lighting control circuits 7a, 7b, ...
, 7n, the number of light-emitting elements for each light-emitting element is calculated collectively, but a plurality of lighting-time calculation circuits 8 are arranged corresponding to each light-emitting element lighting control circuit 7a, 7b, ..., 7n. It may have any configuration. in this case,
When the light emitting element lighting control circuits 7a, 7b, ..., 7n are individually integrated into a single integrated circuit, the functions of the lighting time calculation circuit 8 can be combined into an integrated circuit, which has the advantage of reducing the number of chips.

In each of the above embodiments, the light emitting element array 4a,
4b, ..., 4n has been exemplified in which the change in the light emission intensity of each light emitting element due to the change in the number of lighting elements is compensated for by changing the lighting time, and the obtained exposure amount is held constant. 4n by changing the drive voltage or drive current of the light emitting element rows 4a, 4b, ..., 4n.
It is also possible to have a configuration in which the individual light emission intensities of the light emitting elements a, 4b, ..., 4n are kept constant, and similar effects can be obtained. In this case, it is possible to employ a known configuration in which the drive voltage applied to the drive circuits of the light emitting element arrays 4a, 4b, ..., 4n is switched or the drive current of the drive circuits is switched based on the number of lights.

Although the above embodiments have been described on the premise that the light emission control method and apparatus are applied to the LED printer, the embodiment of the present invention is not limited to this. It can also be effectively applied in the field of displays and the like.

[0055]

As described above, according to the light emission control method and apparatus of the present invention, when a light emitting element is selectively turned on from among a plurality of light emitting elements, the number of light emitting elements to be turned on at the same time is changed. While the light emission intensity of each light emitting element changes, the light exposure amount by the light emitting element, that is, the product of the light emission intensity and the light emission time is dynamically compensated so as to be constant. A uniform exposure amount can be obtained without depending on
This is effective in obtaining high-quality print output.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus for realizing a light emission control method according to an embodiment of the present invention.

FIG. 2 is a block diagram of an apparatus that realizes a light emission control method according to a second embodiment of the present invention.

FIG. 3 is a block diagram of an apparatus for realizing a light emission control method according to a third embodiment of the present invention.

FIG. 4 is a block diagram of an apparatus for realizing a light emission control method according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of an apparatus that realizes a conventional light emission control method.

FIG. 6 is a characteristic diagram showing a relationship between the number of light emitting elements and light emission intensity.

[Explanation of symbols]

 1a 1b, ..., 1n shift register 2a, 2b, ..., 2n latch 3a, 3b, ..., 3n driver 4a, 4b, ..., 4n light emitting element row 5 lighting light emitting element number calculation circuit 6 variable pulse width generating circuit 7a, 7b, ..., 7n Light emitting element lighting control circuit 8 Lighting time calculation circuit 9 Constant pulse width generation circuit

Claims (11)

[Claims] 1. Corresponding to the first step of giving the number of light emitting elements to be turned on by a light emitting means having a plurality of light emitting elements to be selectively turned on, and the number of light emitting elements to be emitted by the light emitting means. A second step of generating a drive signal to be formed, thereby driving the light emitting means. 2. A first process for giving the number of light emitting elements to be turned on by a light emitting means having a plurality of light emitting elements to be selectively turned on, and a pulse corresponding to the number of light emitting elements to be emitted by the light emitting means. A second step of generating a width drive signal and driving the light emitting means according to the second drive signal. 3. A first step of giving the number of light emitting elements to be turned on by a light emitting means having a plurality of light emitting elements to be selectively turned on, and corresponding to the number of light emitting elements to be emitted by the light emitting means. A second process of generating a drive signal having a long time when the number of light emitting elements is large and generating a drive signal having a short time when the number of light emitting elements is small, thereby driving the light emitting means. Emission control device. 4. A first step of calculating the number of light emitting elements of said light emitting means to be driven to be turned on from data for driving a light emitting means having a plurality of light emitting elements which are selectively turned on, and said light emitting means. And a second step of generating a drive signal having a pulse width corresponding to the number of light emitting elements to be driven, and thereby driving the light emitting means. 5. A light emitting means having a plurality of light emitting elements which are selectively turned on, a light emitting element number setting means for giving the number of light emitting elements turned on by the light emitting means, and a light emitting element number setting means. A light emission control device, comprising: a control unit that changes a drive signal given to the light emitting unit based on the number of light emitting elements. 6. A light emitting means having a plurality of light emitting elements which are selectively turned on, a light emitting element number setting means for giving the number of light emitting elements turned on by the light emitting means, and a light emitting element number setting means. And a pulse width changing means for changing the pulse width of a drive signal given to the light emitting means based on the number of light emitting elements. 7. A light emitting means having a plurality of light emitting elements which are selectively turned on, a driving means which selectively drives the light emitting elements of the light emitting means, and a light emission of the light emitting means which is to be turned on by the driving means. The light emitting element number setting means for giving the number of elements, and the pulse width changing means for changing the pulse width of the drive signal given to the driving means based on the number of light emitting elements given by the light emitting element number setting means are provided. A light emission control device characterized in that. 8. A light emitting means having a plurality of light emitting elements which are selectively turned on, a driving means for selectively driving the light emitting elements of the light emitting means, and the light emitting means provided to the driving means should be turned on. The number of light emitting elements for calculating the number of light emitting elements of the light emitting means to be driven by the driving means based on the data designating the light emitting elements, and the number of light emitting elements given by the number of light emitting elements And a pulse width changing means for changing the pulse width of the drive signal given to the driving means based on the light emission control device. 9. A light emitting means having a plurality of light emitting elements which are selectively turned on, a driving means for selectively driving the light emitting elements of the light emitting means, and the light emitting means provided to the driving means should be turned on. The number of light emitting elements for calculating the number of light emitting elements of the light emitting means to be driven by the driving means based on the data designating the light emitting elements, and the number of light emitting elements given by the number of light emitting elements A pulse width calculation means for calculating a pulse width of a drive signal to be given to the drive means based on the light emission control device. 10. A plurality of light emitting means having a plurality of light emitting elements which are selectively turned on, and a driving means which is provided for each of the light emitting means and selectively drives the light emitting elements of the light emitting means in accordance with input data. And the number of light emitting elements of the light emitting means to be driven for lighting is calculated based on the input data given to each of the driving means, and the pulse width of the drive signal by the driving means is calculated based on the obtained number of light emitting elements. A light emission control device, comprising: a control unit provided for each of the drive units so as to be changed. 11. A light emitting diode array means having a plurality of light emitting diodes which are selectively turned on, a light emitting diode number setting means for giving the number of light emitting diodes to be turned on by the light emitting diode array means, and the light emitting diode number setting means. The pulse width changing means for changing the pulse width of the drive signal given to the light emitting diode array means so as to become longer as the number of light emitting diodes increases based on the number of light emitting diodes given by apparatus.