JPH01204745A - Printer - Google Patents

Abstract

PURPOSE:To simply and effectively adjust image quality, by inputting multivalue image data to correct the same and forming an image on the basis of the image data altered so as to have a desired gradation characteristic and altering an image forming condition. CONSTITUTION:Multivalue digital image data 25 is stored in a page memory 2. Each of the data arranged in the memory 2 as 8-bit multivalue video signals is successively read to be inputted to a line buffer 5 to take synchronism with respect to the video signals and subsequently receives digital-digital conversion by an RAM 6. The gradation data which has received correction by the RAM 6 is converted to an analogue signal of 256 levels by a D/A converter 8 while said analogue signal is compared with the triangle wave of a predetermined cycle outputted from a signal generator 9 by a comparator 10 to receive pulse width modulation. The output signal of the comparator 10 is inputted to a laser driver 11 to drive a look-up table, developing bias voltage 38 and a laser power controller 36. By this method, wide correction from large correction to fine correction can be performed on the basis of a laser beam quantity set value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printer device that inputs a multivalued image from an external device such as a host computer or an image league, and outputs a high-quality image including halftones. It is something.

[Conventional technology]

Conventionally, when outputting a halftone image using a laser beam printer that applies electrophotographic technology, the computer or controller that serves as the data source performs image processing such as halftone dot processing, dither processing, and PWM, and then converts it into a binary image before sending it to the printer. I was using the method of inputting.

According to this method, since it handles binary signals, it is possible to transfer halftone data with high efficiency by compressing the transferred data, etc., but on the other hand,
Regarding the depth direction of density, due to delays in the data transmission path, conditions of the electrophotographic process, variations between devices, etc., it is not possible to maintain the desired stable gradation even though the same halftone image data is sent from the host computer or controller. It was difficult to obtain.

Also, when using several different printers using the same host computer or controller, the correspondence between dither patterns and density differs depending on the printer, so connect the density correction (γ correction) table depending on the printer. A situation exists in which host computers or controllers are required for the number of printers, making it difficult to maintain compatibility between printers.

For example, as data for a figure with gradation, read the figure with an image reader, develop it into a dot image,
There is a method of giving each dot a value in the depth direction. In this case, as the image input section of the image reader, for example, a CCD
When a sensor or the like is used, the density information of the original image is converted into substantially linear voltage information by the reflected light from the original image at the sensor section, as shown in FIG. Since this has a logarithmic relationship with the density, the image changes greatly depending on whether or not this signal is corrected in the reader section, and to what extent the signal is corrected. In addition, the host computer itself has its own factors that cause image variations. For example, the font design itself varies from company to company, with some having a strong tendency to make the letters thicker, while others are designed to make the letters look thinner and neater.

Because of this situation, conventionally when one system was configured with a league, a host computer, a printer, etc.
Inconveniences occurred, such as the resulting image being overall pale and blurry, the letters being thin, and conversely, the overall image being dark and the letters being crushed. Furthermore, in severe cases, the text may be thin but the photographs and graphics are flattened and there is no gradation, or conversely, the characters may be thick and flattened but the photographs and graphics are faded.

[Means for solving problems]

According to the present invention, in a printer device that has a data input section for inputting multivalued image data and is capable of outputting a halftone image, a gradation correction means for correcting the inputted multivalued image data is provided. , a printer device comprising: a changing means for changing the characteristics of the correcting means; an image forming means for forming an image based on tone-corrected image data; and a means for changing image forming conditions of the image forming means. This makes it possible for the printer to respond to the characteristics of the host section or the user's preferences, and allows the operator to easily and effectively adjust the image quality. This is what I did.

A second object of the present invention is to provide practical and extremely effective implementation means for the gradation correction means and correction characteristic changing means.

〔Example〕

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

FIG. 1 shows a printer device according to the present invention,
1 shows a first embodiment of the present invention.

In FIG. 1, multivalued digital image data 25 input to the printer from a host computer etc. is input to the I10 port l.
The data is stored in the page memory 2 in the printer through the printer. The data arranged as an 8-bit multilevel video signal in the memory 2 is sequentially read out to the line buffer 5 at the start of printing, synchronized with the video signal, and then digital-to-digital converted in the RAM 6, which is a look-up table. receive. FIG. 2 shows an example of the contents of the lookup table in the RAM 6. The lookup table shown in FIG. 2 inputs input data to the address line of the RAM 6 and outputs the data written at that address from the data line. For example, in FIG. 2, when AOH (H is hexadecimal) is input as image density data, it is converted to 90H and output. In Figure 1, 7 is a selector and RO
From multiple lookup tables stored in M3,
This is a selection means for selecting the optimum one and loading it into the RAM 6. - As an example, in ROM3, Figure 4(a), (
Assume that a lookup table of a plurality of characteristics as shown in b) is stored. In Figure 4, the characteristics in (a) mainly take into consideration only the output characteristics of the printer, and if you select II or I for the standard value ■, the output image will become darker (or IV).
, V can be selected to make the output image lighter. In addition, the characteristic shown in FIG. 4 (b) is obtained by logarithmically correcting the characteristic shown in (a), taking into account both the output characteristic of the printer and the input characteristic of the league's COD. In Fig. 4(b) as well, the characteristics of ■ are compared to the characteristics of ■.

(2) adjusts the output image to a darker direction, and IV and V adjust the output image to a lighter direction. Selector 7 in Figure 1
has a form as shown in FIG. In FIG. 5, switch 26. 27 is a switch mainly for responding to reader characteristics; when 26 is pressed, Fig. 4 (a) is selected, and when 27 is pressed, Fig. 4 (b) is shown.
A lookup table is selected from among. Also, 5
The fourth switch 28 is a switch for adjusting concentration.
This is to select one of the characteristics of ■ to V in figure (a) or (b), and in order from the left: V, IV, III,
n, corresponding to I. In this embodiment, a lookup table with 256 gradations = 8 bits x 8 bits was used, so a memory area of 256 bytes was required in the RAM 6. In addition, in ROMa, there are
(b) A memory area of approximately 2.5 Kbytes was used to store a total of 10 types of lookup tables. If more lookup tables are required, for example, prepare one logarithmic conversion table instead of the lookup table in Figure 4(b) and combine this with the one in Figure 4(a). Figure 4 (b) from the lookup table
) It is possible to save memory by combining tables.

The 8-bit gradation data corrected in the RAM 6 in this manner is then converted into a 256-level analog signal by the D/A converter 8. This analog signal is compared by a comparator 10 with a triangular wave of a predetermined period output from the signal generator 9, and is subjected to conversion from a depth direction signal to a length direction signal, that is, pulse width modulation. This situation will be explained with reference to FIG.

Signal A in FIG. 6(a) is an image signal output from the D/A converter 8, signal B is a triangular wave from the signal generator 9, and A and B are synchronized by the video clock as shown. is taken. FIG. 6(b) is a signal obtained by comparing and combining A and B in FIG. 6(a) using a comparator 1O, that is, a pulse width modulated signal (when A≦B, the output of the comparator 10 is ON). ). Note that the signal generator 9
The signal may be a repeating signal of a predetermined period, and a trapezoidal wave, a sawtooth wave, etc. other than a triangular wave may be used.The output signal of the comparator 10 is input to the laser driver 11, and drives the laser diode 12. .

The laser light from the laser diode 12 is converted into scanning light by the rotating polygon mirror 13 and scans over the photoreceptor 18. Note that a part of the scanning light is received by a beam detect device (not shown) to generate a video signal and a signal generator 9.
It is used as a synchronization signal. The photoreceptor 18 is connected to the charger 1
After being uniformly charged in step 5, a latent image is formed on the surface by the aforementioned laser scanning, and then the latent image is developed in developing device 17.

This developed pattern is transferred onto a transfer material 22 by a transfer charger 19, and then transferred to a heat fixing roller 23. It is fixed at 24. The developer remaining without being transferred to the surface of the photoreceptor 18 is collected by a cleaner 20, and the charge on the photoreceptor is erased by pre-exposure 21, and the same process is repeated again.

In the manner described above, the output image quality of an image including halftones could be easily adjusted via the selector for image quality adjustment as shown in FIG. Of course, not only the midtone level,
The line width of the image is also adjusted at the same time. For example, when line drawings or characters with depth direction information are output as image data, it is also possible to adjust the line width of the output image. In this example, the lookup table is D/
Although it is arranged immediately before the A converting section, it may be arranged before the page memory 2 and after data correction is performed, the image data is stored in the page memory 2.

Next, in the correction method described above, a look-up table was selected and correction was performed digitally, but in order to further improve the gradation, the developing bias voltage 38 is changed to obtain a good output without background fog. Let's talk about.

FIG. 7 shows image data and output density when the developing bias is changed. Characteristic H in FIG. 7 has a low developing bias and causes fogging for image data of 00 manual effort. Further, i has a high developing bias, and when inputting image data near 00, whiteout occurs.

Therefore, the development bias is determined from the required density range (corresponding to 00 to FF), a control signal is sent to the high pressure unit 37, the optimal curve prepared in the lookup table is set, and the curve is loaded into the RAM. By performing image data processing, it is possible to obtain good printouts without fogging or overexposure.

In the above explanation, the developing bias was changed, but it is easily inferred that the same effect can be obtained by changing the primary charging voltage, so the explanation will be omitted.

[Second Example] In the first example, a look-up table was selected, digital processing was performed, and the developing bias and high voltage charging voltage of the image forming conditions were changed. A method for obtaining an image with high level adjustment will be explained.

FIG. 8 shows the relationship between image data input and output density when changing the amount of laser light as a parameter. Characteristic J in FIG. 8 is the characteristic when the amount of laser light is increased, and K is the characteristic when the amount of laser light is decreased.

In the second embodiment, the image data input value near FF is thickened (it can be changed), and the laser light amount set value can be changed by driving the lookup table, developing bias voltage, charging high voltage, etc. and the laser power controller 36. This makes it possible to perform a wide range of corrections, from major corrections to subtle corrections.

Furthermore, the operation section shown in FIG. 6 is configured as shown in FIG.
By incorporating the above-mentioned correction characteristics into various combinations according to the value of the γ volume, it is possible to obtain a better print output that is easier to use.

[Third Embodiment] In the first and second embodiments, the selection of gradation correction data was mainly performed from the operation unit, but it is also possible to select it by instructions from the host device. .

Furthermore, as a method that can be easily realized from the hardware structure described above, the gradation correction data prepared and generated by the host device is sent directly to the RAM via Ilo shown in FIG.
After that, by inputting multivalued image data and performing image processing, it became possible to freely select and manipulate the printer's gamma characteristics, density, etc. with easy processing on the host side.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the printer device according to the present invention; FIG. 2 is a diagram for explaining the contents of the lookup table in the RAM 5; FIG. 3 is a diagram showing an example of the characteristics of the image league; Figure 4 is a diagram for explaining the contents of ROM3, Figure 5 is a diagram for explaining the selector in Figure 1, Figure 6 is a diagram for explaining the pulse width modulation signal forming operation according to this embodiment, and Figure 7 is a diagram for explaining the development bias. FIG. 8 and FIG. 9 are diagrams for explaining the second embodiment. 1...Data input section 2...Page memory 3.
...Memory 4...Computer 5...
・Buffer 6...RAM7...Selector 8...D/A converter 9...Comparison wave generator 10...Comparator 11...Laser drive circuit 12...Semiconductor laser 13... Polygon mirror 14... f/θ lens 15... Charger 16... Laser beam 17... Developer 18... Photoreceptor 19... Transfer charger
20...Cleaner 21...Pre-exposure lamp 2
2... Transfer paper 23, 24... Fixing roller 25...
・Multi-valued image data 26 to 28...Switch 35・
...γ volume 36...laser power controller 37...high pressure unit

Claims (1)

[Claims] In a printer device having a data input section for inputting multivalued image data and capable of outputting a halftone image, a gradation correction means for performing gradation correction of input multivalued image data, and the correction means The image forming apparatus is characterized by comprising a changing means for changing the correction characteristics of the image forming apparatus, an image forming means for forming an image based on the gradation-corrected image data, and a means for changing the image forming conditions of the image forming means. printer device.