JPH01204743A - Printer - Google Patents

Abstract

PURPOSE:To obtain interchangeability of the image quality between a host and a printer on the side of the printer, by inputting multivalue image data to correct the same and changing over the image data to a desired correction characteristic before modulating the multivalue image data by the modulation of the luminous intensity of an image exposing light source. CONSTITUTION:Multivalue digital image data 10 are stored in a page memory 2. Each of the image 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 receives digital/digital conversion by an RAM 6. The 8-bit 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 to be amplified by an amplifier 9 and the amplified signal is subsequently inputted to a laser driver circuit 11 to be converted to a drive current for directly driving semiconductor laser 11 and said laser 11 lights at laser beam intensity of 256 stages. An inputted current value determines the optimum quantity P1 of beam on a black level from an image and the gain and offset of the amplifier are regulated.

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 halftone images using a printer such as a laser beam printer that applies electrophotographic technology, the host computer or the like generally performs appropriate processing such as tint dot processing or dither processing before inputting the image signal to the printer. The conventional method was to go to the printer, convert the signal into a binary value, and then input it to the printer.

According to this method, a binary signal is transferred to handle it.

Although it is easy to compress data, it has the disadvantage that information in the depth direction of density is lost, and as a result, increasing the number of gradations deteriorates resolution. Additionally, the correspondence between dither patterns and densities generally differs depending on the printer. For example, even if the same dither pattern is input, some printers may have the white background blown out, while other printers may have the near black side blown out. This caused the inconvenience of being unable to do so. In particular, because of the latter drawback, there is a situation where it is difficult to achieve compatibility between printers, where the same host computer is used to use several different types of printers.

In addition, variations in gradation reproduction occur not only on the printer side, but also on the printer side.
In many cases, the cause is also on the host side that supplies graphic data. As data of a figure having gradation, for example, there is a method of reading the figure with an image reader, developing it into a dot image, and giving a value in the depth direction to each dot.

In this case, as the image input section of the image reader, for example,
When a COD 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. 3(a).

This has a logarithmic relationship with the density as shown in Figure 3(b), so the image may become larger depending on whether or not this signal is corrected in the reader section, and to what extent. Change. 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 reader, host computer, 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 photos and graphics are flattened and there is no gradation, or conversely, the letters may be thick (and flattened) but the photos and graphics are blurry.

[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. , a changing means for changing the characteristics of the correcting means, and a modulating means for modulating the brightness of the image exposure light source based on the gradation-corrected multivalued image data. This allows the printer device to respond to the characteristics of the host section and reader section, or the user's preferences, and allows easy and effective image quality adjustment by using the means for changing the gradation correction characteristics. This is what I did.

〔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,
This shows a first example.

In FIG. 1, multivalued digital image data 10 input from a host computer or the like to the printer device is stored in a page memory 2 in the printer through an I10 port 1.

The data arranged as a 5-bit multilevel video signal in the memory 2 is sequentially read out to the line buffer 5 at the start of printing, and after being synchronized with the video signal, it is digital-to-digital in the RAM 6, which is a look-up table. undergo transformation. FIG. 2 shows an example of the contents of the lookup table in the RAM 6. The look-up table shown in FIG. 2 inputs manual data to the address line of the RAM 6 and outputs the data written at that address from the data line. For example, if AOH (H is hexadecimal) is input as image density data in FIG. 2, it is converted to 90H and output. In Figure 1, 7 is the selector, and ROM3
This is a selection means for selecting an optimal one from a plurality of look-up tables stored in the RAM 6 and loading it into the RAM 6.

- As an example, assume that the ROM 3 stores look-up tables of a plurality of characteristics as shown in FIGS. 4(a) and 4(b). The characteristics in (a) in Figure 4 mainly take into account only the output characteristics of the printer, and if you select ■, machining, the output image becomes darker, and IV, V
If you select , you can adjust the output image to make it darker.In addition, the characteristic (b) in Figure 4 is the logarithmically corrected characteristic (a), which is a combination of the printer's output characteristic and the reader's COD input characteristic. Both are taken into account. Also in Figure 4(b),
In contrast to the characteristics of ■, II and I make the output image darker, and ■.

(2) adjusts the output image to make it lighter.

The selector 7 in FIG. 1 has a form as shown in FIG. Switches 25 and 26 in Fig. 5 are mainly switches for supporting reader characteristics, and when 25 is pressed, Fig. 4 (a) and 26
When you press , a lookup table is selected from (b). Further, the switch 27 is a switch for adjusting the concentration, and is used to select one of the characteristics of ■ to V in FIG. ,
Corresponds to n and I. In this embodiment, a look-up table with 256 gradations = 8 bits x 8 bits was used, so a 256-byte memory area was required in the RAMG. Also, inside ROMa, there are
) 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, instead of the lookup table in Figure 4(b), prepare one logarithmic conversion table and combine this with the lookup table in Figure 4(a). ) from the lookup table in Figure 4 (b
) 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 by the D/A converter 8 into a 256-level analog signal. This analog multilevel signal is amplified by an amplifier 9 and then input to a laser drive circuit 11, where it is converted into a drive current for directly driving the semiconductor laser 11. As a result, the laser light is turned on at 256 levels of intensity. FIG. 6 shows the relationship between the light intensity of the semiconductor laser and the input current. In FIG. 6, io is the threshold current for laser emission, and Pmax is the maximum power of the laser (the limit without damage). Therefore, the input current value is within the range of io - imax. In this example, the black level (
= 256 levels) was determined, and the gain and offset of the amplifier 9 were adjusted. In addition, at the complete white level (=0 level), instead of setting the current to io, the laser is forced to Om A.
FF L, good. Next, the laser light from the laser diode 12 is converted into scanning light by a rotating polygon mirror 13, and scans over the photoreceptor 18. Note that a portion of the scanning light is received by a beam detect device (not shown) and used as a video signal and a synchronization signal for the signal generator 9. After being uniformly charged by the charger 15, the photoreceptor 18 is subjected to the laser scanning described above to form a latent image on its surface, and is then transferred to the developer 17.
Develop the latent image.

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 halftone level (but also the line width of the image is adjusted at the same time. For example, when line drawings or characters with depth information are output as image data, it is necessary to adjust the line width of the output image. In addition, in this embodiment, 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.

[Second Embodiment] In the first embodiment, the light intensity of the semiconductor laser 12 was adjusted by changing the gain and offset of the amplifier 9 shown in FIG. 1, but the maximum and minimum outputs of the amplifier 9 were fixed, and the laser drive By controlling the circuit 11, the amount of laser light may be adjusted. An example of this is shown in FIG. When adjusting the amplifier 9
First, a drive voltage corresponding to the black level is input to the laser drive circuit 28. Accordingly, the laser 29 emits light, and a portion of the light is received by the light receiving element 30. This is detected by the monitor 31, and compared by the controller 32 with the reference level signal at the black level from the reference signal generator 33.

By feeding this result back to the laser drive circuit 28, the amount of light emitted at the black level can be adjusted. Next, the amount of light emitted at the white level is
Since the laser output is turned off and control is difficult, a drive voltage corresponding to a light gray signal (for example, 16 levels) is input to the laser drive circuit 28, and this is used as the gray level reference signal of the reference signal generator 33. The white level is adjusted by comparing and setting the optimum light amount. In this way,
The gain and offset of the laser drive circuit can be automatically adjusted (note that whether the white or black drive signal level is adjusted first depends on the circuit configuration). At this time, black level adjustment may be used as an image adjustment means. This can be done by making it possible to change the reference signal value of the reference signal generator 33 at the black level from the outside.

In the above embodiments, a laser beam printer has been described, but the present invention is also applicable to an LED printer using an LED array as a light source, an LCD printer using a liquid crystal shutter, and the like.

〔Effect of the invention〕

As explained above, there is a receiver for inputting multivalued image data, a correction means for correcting this data, a changing means for switching to a desired correction characteristic, and a brightness modulation of an image exposure light source. By configuring a printer device using a modulation means that modulates multilevel image data by
In addition to being able to obtain fine-grained halftone images that could not be obtained with printer devices that input and output data using value data,
This has traditionally been a problem. This allows the printer to solve the problem of incompatible image quality between hosts and printers due to differences in the characteristics of the host section and printer section, resulting in varying halftone images and line widths. became.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the printer device in this embodiment, Figure 2 is a diagram showing an example of the contents of a lookup table in RAMQ, Figure 3 is a diagram showing an example of the characteristics of the image reader, and Figure 4 is a diagram showing an example of the characteristics of the image reader. A diagram showing the contents of the lookup table in ROMa, Figure 5 is an explanatory diagram of the selector, Figure 6 is a diagram showing the relationship between the light intensity of the semiconductor laser and the input current, and Figure 7 is an explanation of the second embodiment. It is a diagram. l...Data human resources department, 2...Page memory,
3...Memory, 4...Computer,
5...Buffer, 6...RAM. 7... Selector, 8... D/A converter,
9...Amplifier, 10...Image data, 1
DESCRIPTION OF SYMBOLS 1... Laser drive circuit, 12... Semiconductor laser, 13... Polygon mirror, 14... f/
θ lens, 15... Charger, 16... Laser light, 17... Developer, 18... Photoreceptor, 19... Transfer charger, 20... Cleaner, 21... Front Exposure lamp, 22... Transfer paper, 2
3, 24...Fixing roller, 25-27...Switch.

Claims (1)

[Claims] A printer device having a data input section for inputting multivalued image data and capable of outputting a halftone image includes a gradation correction means for performing gradation correction of the inputted multivalued image data; It has a changing means for changing the correction characteristics of the means, and a modulating means for modulating the brightness of the image exposure light source based on the gradation-corrected multivalued image data, and the image quality is adjusted by the changing means. A printer device characterized by performing the following.