TWI546633B - Method for calibrating the light amount of lighting elements of a printing head and testing equipment and printing equipment for the same - Google Patents

Description

Print head light quantity correction method, test equipment and printing equipment

The invention relates to a light quantity correction method, in particular to a light quantity correction method, a test device and a printing device of a print head.

Photocopiers, printers, fax machines, and multifunction machines use Electro-photography as the core technology for printing documents, meaning that the distribution of electrostatic charges is changed by light of a specific wavelength. Produce a photographic image.

FIG. 1 is a schematic view showing the light-emitting diode (LED) printer 100. As shown in Fig. 1, the LED printer 100 includes a photosensitive drum 110 and a print head. The print head 120 includes a plurality of linearly arranged light-emitting diodes 122, whereby a high DPI (Dots Per Inch) print resolution can be achieved. For example, to achieve a resolution of 1200 x 2400 DPI, it is necessary to arrange 1200 LEDs 122 per inch.

However, if the density of the printed documents is to be uniform, the amount of output light of each of the light-emitting diodes 122 in the printing head 120 needs to be accurately controlled to prevent the exposure area of the corresponding photosensitive drum 110 from being overexposed or underexposed. The general approach is to make the light output is low. The diode 122 raises its output light amount, and causes the light-emitting diode 122 having a higher output light amount to lower its output light amount, so that the output light amount of each of the light-emitting diodes reaches the tolerance range of the product specification. Herein, the output light amount refers to the product of the light intensity and the light-emitting time, that is, the exposure amount during the light-emitting time.

Figure 2 is a schematic diagram of the adjusted output light quantity and print quality. As shown in Fig. 2, it can be seen that even if the output light amount of the light-emitting diode 122 is corrected, if the image of the same density is to be printed, the print quality is difficult to achieve the uniformity of the image quality due to the difference in the light-sensitive intensity. Requirements. Therefore, how to accurately correct the output light amount of each of the light-emitting diodes is a problem that researchers in the field are trying to overcome.

In view of the above problems, the present invention provides a method for correcting the amount of light of a print head, the print head comprising a plurality of light-emitting elements, in addition to correcting the amount of output light of the light-emitting elements, together with the beam profile characteristics of the light-emitting elements To make corrections. First, the amount of light and the light profile of the light-emitting element are measured. For each of the light-emitting elements, a light amount correction value is generated according to the corresponding light amount and the corresponding light profile parameter. Further, for each of the light-emitting elements, the amount of light is adjusted according to the corresponding light amount correction value. Thereby, the amount of output light of each of the light-emitting elements can be accurately controlled so that the print quality (ink density) is uniform.

Here, the light profile parameter may be maximum brightness, maximum width, cross-sectional area, or modulation transfer function (MTF).

In an embodiment, the light amount correction value may be generated according to the following steps. First, an optical parameter curve is generated based on the light profile parameters of the light-emitting elements. Next, the light parameter curve is smoothed to produce a smooth curve. According to the light parameter curve and the smooth curve, each hair is generated. The optical parameter correction value of one of the optical elements is continued for each of the light-emitting elements to generate a light amount correction value based on the corresponding light parameter correction value and the corresponding amount of light.

In an embodiment, in addition to generating the light amount correction value for the individual light emitting elements, the light amount correction value may be generated in units of two or more light emitting elements.

In an embodiment, a ratio of a light profile of the light parameter to a light profile of the smooth curve may be calculated for each of the light-emitting elements, and a light amount correction value may be generated according to the ratio and the amount of light.

In one embodiment, a target value is calculated according to the amount of light of the light-emitting element, and the light quantity of the light-emitting element is adjusted according to the target value, and then the step of generating the light quantity correction value according to the corresponding light quantity and the corresponding light contour parameter is performed.

Here, the amount of light can be adjusted by adjusting the light-emitting time or the amount of current of the light-emitting element.

The present invention further provides a test apparatus that performs the above-described method of correcting the amount of light of the print head.

The present invention also provides a printing apparatus which performs the above-described method of correcting the amount of light of the printing head, wherein the printing head is one of the printing heads of the printing apparatus.

According to the light quantity correction method, the test device and the printing device of the print head according to the embodiment of the present invention, the light quantity and the light profile parameter are simultaneously considered for correction, so that the density of the printing can be more consistent.

100‧‧‧Lighting diode printer

110‧‧‧Photosensitive drum

120‧‧‧Print head

122‧‧‧Lighting diode

H‧‧‧Maximum brightness

W‧‧‧Maximum width

A‧‧‧ cross-sectional area

L1, L2, L1', L2'‧‧‧ light contours

S310‧‧‧Measure the light quantity and light profile parameters of complex light-emitting elements

S320‧‧‧ The light quantity is the same?

S330‧‧‧ Calculate the target value and adjust the amount of light of the light-emitting element

S340‧‧‧ For each illuminating element, a light quantity correction value is generated according to the corresponding amount of light and the corresponding light profile parameter

S341‧‧‧ Generate a light parameter curve based on the light profile parameters of the illuminating element

S342‧‧‧ Smoothing the light parameter curve to produce a smooth curve

S343‧‧‧According to the optical parameter curve and the smooth curve, the optical parameter correction value of one of the light-emitting elements is generated.

S344‧‧‧ For each light-emitting element, the light quantity correction value is generated according to the corresponding light parameter correction value and the corresponding light quantity

S350‧‧‧ For each light-emitting element, the amount of light is adjusted according to the corresponding light amount correction value

[Fig. 1] is a schematic view showing the light-sensing of a conventional LED printer.

[Fig. 2] is a schematic diagram of the adjusted output light amount and print quality.

[Fig. 3] A flow chart of a method for correcting the amount of light of a print head according to an embodiment of the present invention.

[Fig. 4] is a detailed flowchart of step S340 in Fig. 3.

[Fig. 5] is a schematic view of the light profile of the present invention.

[Fig. 6] is a schematic diagram of adjusting the amount of light using the light profile parameter of the present invention.

FIG. 3 is a flow chart of a method for correcting the amount of light of a print head according to an embodiment of the present invention. The print head has a plurality of light-emitting elements. The light emitting element may be a light emitting diode, a light thyristor or the like. The light emitting elements can be arranged in one or two dimensions.

As shown in Fig. 3, first, the light amount and the light profile parameter of the light-emitting element are measured (step S310). Herein, a light sensing device such as a charge coupled device (CCD) sensor, a CCD camera, or a contact image sensor (CIS) can be used to detect the amount of light emitted by each of the light emitting elements. Next, it is judged whether or not the amount of light emitted from each of the light-emitting elements is uniform (step S320). The term "consistent" means that the difference between the amount of output light of each of the light-emitting diodes is within an allowable range. This allowable range is the allowable error value of the product specification. Here, the parameters for confirming whether or not the amount of light is uniform may be the following two, but the embodiment of the present invention is not limited thereto. First, the light sensing device is used to measure the light intensity emitted by the light emitting diode. Secondly, the light sensing device can be used to measure the emitting of the light emitting diode. Judging by the dot size (Dot Size).

After the step S320, if the result of the determination is negative, a target value is calculated, and the amount of light emitted from each of the light-emitting elements is adjusted so that the light-emission amount of each of the light-emitting elements reaches the target value (step S330). Here, the target value may be, for example, an average value of the amount of light emitted by the light-emitting elements. However, embodiments of the invention are not limited thereto. If it is determined in step S320 that the amount of light is the same, the process proceeds to step S340. Therefore, at the time of proceeding to step S340, the amount of light of the light-emitting elements is uniform. Here, the amount of light (or amount of light emitted) is the cumulative light intensity during the light emission time.

In step S340, for each of the light-emitting elements, a light amount correction value is generated according to the corresponding light amount and the corresponding light contour parameter. Further, in step S350, for each of the light-emitting elements, the amount of light is adjusted in accordance with the corresponding light amount correction value. The method of adjusting the amount of light may be, for example, adjusting the light-emitting time or the amount of current of the light-emitting element, or increasing the light-emitting time to increase the amount of light, shortening the light-emitting time, reducing the amount of light, increasing the amount of current, increasing the amount of light, or reducing the amount of current to reduce the amount of light. Thereby, in addition to correcting the amount of output light of the light-emitting element, the beam profile characteristics of the light-emitting element are also collectively considered for correction, and the output light amount of each of the light-emitting elements can be accurately controlled to make the print quality ( The ink density is consistent.

In an embodiment, the light amount correction value of step S340 can be generated according to the following steps. As shown in Fig. 4, Fig. 4 is a detailed flow chart of step S340. First, an optical parameter curve is generated based on the light profile parameters of the light-emitting elements (step S341). Next, the light parameter curve is smoothed to produce a smooth curve, and a smooth curve can be generated by using a commonly used smoothing algorithm (step S342). Further, in step S343, the light parameter correction values of the respective light-emitting elements are generated based on the light parameter curve and the smooth curve. Herein, for each of the light-emitting elements, a ratio of the light profile of the light parameter to the light profile of the smooth curve is calculated, and the light parameter correction value is generated according to the ratio and the amount of light. Further, for each of the light-emitting elements, a light amount correction value may be generated based on the corresponding light parameter correction value and the corresponding light amount (step S344).

In an embodiment, taking the adjustment time as an example, the product of the illumination time after the step S320, the ratio, and a constant may be used as the final correction time (ie, the amount of light). Correction value). Here, the constant can be a value between 0 and 1, for example 0.5.

Although the above description has been made by illuminating an individual light-emitting element as an example, the embodiment of the present invention is not limited thereto, and in some embodiments, the light amount correction value may be generated in units of two or more light-emitting elements. For example, a one-dimensional array (ie, a linear array) of light-emitting elements may be a group of N light-emitting elements, and N is a positive integer of 2 or more. If the light-emitting elements are two-dimensionally arranged, N and M may be positive integers per NxM light-emitting elements, and one of them is a positive integer of 2 or more, for example, 1x2, 2x1, 2x2, 2x3, 3x2, 3x3, and the like.

As shown in Figure 5, it is a schematic diagram of the light profile. The aforementioned light profile parameter may be a maximum brightness H, a maximum width W, a cross-sectional area A, or a modulation transfer function (MTF). The calculation of the modulation conversion function can calculate the modulation conversion function (ie, (luminance maximum - luminance minimum) / (luminance maximum + luminance minimum)) in units of the above two or more light-emitting elements.

Figure 6 is a schematic diagram of adjusting the amount of light using the light profile parameters. As shown in Fig. 6, the light contours L1, L2 before adjustment are indicated by solid lines, and it can be seen that the maximum brightness H of the light contour L1 is higher than the light contour L2, but the maximum width W of the light contour L1 is shorter than the light contour L2. Therefore, although the amount of light (the area under the solid line) is the same, the exposure amount of the photosensitive drum is actually higher than the light profile L2, so that the print density as shown in FIG. 2 is not The situation is the same. Through the above method, after considering the light quantity and the light profile parameters, the light profiles L1' and L2' indicated by the broken lines can be learned, and the cross-sectional area A of the specific light intensity can be the same, thereby enabling the two to act on The exposure amount of the photosensitive drum can be relatively uniform, so that the printing density is uniform.

In another embodiment, the aforementioned light amount correction method can also be applied to testing The device calibrates the aforementioned print head. The test device can have a sensing unit, a control unit, a storage unit, and an input and output unit. The sensing unit may be the aforementioned CCD sensor, CCD camera or contact type photosensitive device or the like. The control unit may be a controller (such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), an embedded controller, etc.), and performs the aforementioned light amount correction method. The storage unit can be a storage medium such as a memory or a memory card to store the program product of the light quantity correction method, and can store the foregoing light quantity, light contour parameter, optical parameter correction value and light quantity correction value. The input and output unit can be an input/output device such as a keyboard or/and a screen for the tester to operate the test device and output calibration or test results.

In still another embodiment, the aforementioned light amount correction method is also applicable to a printing apparatus such that the printing apparatus can self-correct the situation in which the amount of illuminating light is shifted due to aging of the illuminating element or other factors. Alternatively, the printing apparatus may adjust the gray scale density of the printing according to the aforementioned light amount correction method. Here, the printing device can be, for example, a printer, a photocopier, a transaction machine, and the like. The printing device may also include the foregoing sensing unit, control unit, storage unit, and input/output unit, and details are not described herein again.

In summary, according to the light quantity correction method, the testing device and the printing device of the printing head according to the embodiment of the present invention, the light quantity and the light contour parameter are simultaneously considered for correction, so that the printing density can be more consistent.

S310‧‧‧Measure the light quantity and light profile parameters of complex light-emitting elements

S320‧‧‧ The light quantity is the same?

S330‧‧‧ Calculate the target value and adjust the amount of light of the light-emitting element

S340‧‧‧ For each illuminating element, a light quantity correction value is generated according to the corresponding amount of light and the corresponding light profile parameter

S350‧‧‧ For each light-emitting element, the amount of light is adjusted according to the corresponding light amount correction value

Claims (9)

A method for correcting the amount of light of a print head, the print head comprising a plurality of light-emitting elements, the light quantity correction method of the print head comprising: measuring one light quantity and one light contour parameter of each of the light-emitting elements; for each of the light-emitting elements And a light quantity correction value is separately generated according to the corresponding light quantity and the corresponding light contour parameter; and for each of the light emitting elements, the light quantity of each of the light emitting elements is respectively adjusted according to the corresponding light quantity correction value. The light quantity correction method of the print head according to claim 1, wherein the light profile parameter is a maximum brightness, a maximum width, a cross-sectional area, or a modulation transfer function (MTF). The method for correcting the amount of light of the print head according to claim 1, wherein the step of generating a correction value according to the corresponding amount of light and the corresponding light profile parameter for each of the light-emitting elements comprises: according to the plurality of light-emitting elements The light profile parameter generates a light parameter curve; smoothing the light parameter curve to generate a smooth curve; generating, according to the light parameter curve and the smooth curve, a light parameter correction value of each of the light-emitting elements; and for each of the light-emitting parameters The component generates the light amount correction value according to the corresponding light parameter correction value and the corresponding light amount. The light quantity correction method of the print head according to claim 3, further comprising: calculating, for each of the light-emitting elements, a ratio of a light parameter curve thereof to a light profile parameter of the smooth curve; wherein the light parameter curve is The smoothing curve generates a light parameter correction value for each of the light-emitting elements, and the light amount correction value is generated based on the ratio and the light amount. The light quantity correction method of the print head according to claim 1, wherein the step of generating a light amount correction value according to the corresponding light quantity and the corresponding light contour parameter is further included according to the step of: The amount of light of the plurality of light-emitting elements calculates a target value; and the amount of light of the plurality of light-emitting elements is adjusted according to the target value. The method for correcting the amount of light of the print head according to claim 1, wherein the step of adjusting the amount of light according to the corresponding light amount correction value for each of the light-emitting elements adjusts a light-emitting time or a current amount of the light-emitting element to adjust Its amount of light. The method for correcting the amount of light of the print head according to claim 1, wherein the step of generating a light amount correction value according to the corresponding amount of light and the corresponding light profile parameter for each of the light-emitting elements is two or more The light amount correction value is generated in units of light emitting elements. A test apparatus is a light amount correcting method of the print head according to any one of claims 1 to 7. A printing apparatus is a light amount correcting method of the print head according to any one of claims 1 to 7.