JPH04207463A - Image forming device - Google Patents

Abstract

PURPOSE:To stably obtain high-grade images even with recording media of any kinds and characteristics by changing the computation algorithm to convert image signals to recording signals of respective hues according to the characteristics and kinds of the recording media. CONSTITUTION:The input image signals of red (R), green (G) and blue (B) are converted to the density signals (C0, M0, Y0) by a cyan/magenta/ yellow(CMY) conversion circuit 31. The density signals C0, M0, Y0 are inputted to an under-color removal(UCR) computing element 32. The density of the BK signal is determined in accordance with the min. value of the density signals C0, M0, Y0 and a medium signal PS by the UCR computing device 32. The medium signal PS is the output obtd. by an optical sensor which detects the transparency or translucency of the recording medium right after emission from a paper tray. The output characteristics are switched by the medium signal PS in such a manner and, therefore, the recording images having a good grade are obtd. at all times even if the kinds and characteristics of the recording media vary.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image forming apparatus such as a copying machine or a printer,
In particular, colorants of multiple different hues that are solid at room temperature (e.g.
The present invention relates to an image forming apparatus that forms an image on a recording medium using toner.

[Prior Art] In recent years, the demand for color recording has increased, and various image forming apparatuses have been proposed or commercialized. The electrophotographic recording method and the thermal transfer recording method are typical recording methods, and are excellent methods having many advantages.

[Problems to be Solved by the Invention] However, in the conventional apparatus described above, full-color recording usually uses four color materials: C (cyan), 1M (magenta), Y (yellow), and BK (black). However, the four-color separation algorithm to obtain the chromaticity (color tone) that the user wants depends on the surface smoothness, chromaticity, or whiteness of the recording medium, and whether it is used as a transmitted image or as a reflected image. Since the optimum value differs depending on the type and characteristics of the recording medium used, it has not always been possible to obtain high-quality images with any recording medium. Furthermore, in order to obtain an image for OHP (overhead projector) (hereinafter referred to as an OHP image), the transparency of the image must be high. Therefore, when the transparency of the coloring material differs depending on the hue, there is a problem that a high-quality image cannot be obtained unless this point is also taken into account.

In view of the above points, the purpose of the present invention is to
An object of the present invention is to provide an image forming apparatus that can always stably produce high-quality images even on recording media with special characteristics.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides an image forming apparatus that forms an image by depositing a plurality of colorants of different hues that are solid at room temperature on a recording medium. The present invention is characterized by comprising a signal processing means that changes an arithmetic algorithm for converting an input image signal into a recording signal of each hue in accordance with an instruction signal indicating the characteristics or type of the recording medium.

Further, in one embodiment of the present invention, the signal processing means varies the conditions for forming the black recording signal depending on the instruction signal.

Further, in another aspect of the present invention, the instruction signal indicates whether the recording medium is transparent or opaque, and the signal processing means changes the conditions for forming the black recording signal depending on whether the recording medium is transparent or opaque. It is characterized by

In another aspect of the present invention, the instruction signal indicates optical characteristics including the smoothness of the surface of the recording medium.

Further, in another aspect of the present invention, the instruction signal is a detection signal of a detection means for detecting the characteristics or type of the recording medium, or a signal of a human power means for inputting an instruction for the characteristics or type of the recording medium. It is characterized by

[Function] In the present invention, in an apparatus for obtaining an image by depositing colorants of a plurality of different hues in a solid state at room temperature on a recording medium in accordance with an image signal, the image signal is determined in accordance with the characteristics of the recording medium. Since an image is formed by determining an arithmetic algorithm for converting into a recording signal of each hue, a high-quality color image can always be stably obtained no matter what characteristics are recorded.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Δ-]shi11 formation FIG. 1 shows the basic configuration of an embodiment of the present invention.

In FIG. 1, A is an image forming apparatus that forms an image by depositing a plurality of colorants of different hues in a solid phase on a recording medium at room temperature, in response to an instruction signal indicating the characteristics or type of the recording medium. , is a signal processing means that changes the arithmetic algorithm for converting an input image signal into a recording signal of each hue.

The signal processing means A varies the conditions for forming a black recording signal, for example, depending on an instruction signal. Further, the instruction signal indicates, for example, whether the recording medium is transparent or opaque, and the signal processing means A changes the conditions for forming a black recording signal depending on whether the recording medium is transparent or opaque. Further, as another example, the indication signal indicates an optical characteristic including the smoothness of the surface of the recording medium. Specifically, the instruction signal is a detection signal from the detection means B that detects the characteristics or type of the recording medium, or a signal from the input means C that inputs an instruction about the characteristics or type of the recording medium.

FIG. 2 shows a schematic internal configuration of a laser beam copying apparatus according to an embodiment of the present invention.

In FIG. 2, a photoconductive photosensitive drum 1 is exposed to a laser beam from a laser beam scanner 2 in accordance with an image signal, and a latent image formed on the photosensitive drum 1 is sequentially converted into a latent image by a developing device 3. cyan) 1M (magenta), Y (yellow), B
Develop with each color toner of K (black). Each developed toner image is sequentially transferred onto the recording medium 14 which is electrostatically attracted and held on the transfer drum 4, and then transferred to the recording medium 1.
4 is peeled off by a peeling claw 17, passes through a conveyor belt 18 and a fixing roller 8, and is discharged onto a discharge tray 19.

FIG. 3 shows image information R (red) of the document read by the image sensor (for example, a photoelectric conversion element such as a CCD sensor array) of the league section (image reading section) 11 in FIG.
From G (green) and B (blue) signals, C, M, Y
, shows the circuit configuration of an image processing circuit that converts into BK recording signals.

In FIG. 3, R, G, and B input image signals are converted into C, M, and Y density signals by a CMY conversion circuit 31.
This density signal is input to an 0CR (undercolor removal) calculation unit 32, and this calculation unit 32 determines the BK image signal density (output level) based on the minimum value of the density of Co, Mo, and Ya and a medium signal PS, which will be described later. is determined. Next, the output signals c, , M, , Y, , BK of the OCR calculator 32 are sent to the masking circuit 33
A predetermined masking process is performed at , and a pulse width modulation process is performed at a PWM (pulse width modulation) circuit 34 . The output signal of the PWM circuit 34 is input to an LD driver 35 and supplied to a laser diode (LD) 36 to become an ON/OFF laser beam signal.

FIG. 4 shows the characteristics of the calculation algorithm of the UCR calculation unit 32 shown in FIG. That is, in FIG. 4, curve A is the characteristic value selected for opaque media such as ordinary high-quality paper, and its horizontal axis is C8, cyan, magenta, and yellow.
The minimum value of the calculation signals of Ma and Yo is set to 255 levels (
It is a value expressed in gradation).

The vertical axis represents a value expressed as a density signal of the BK (black) signal generated at that time. On the other hand, curve B
is a characteristic value selected when forming an OHP image on a transparent recording medium, and the amount of BK is suppressed compared to one song liA.

Now, in FIG. 2, it is assumed that the developing device 3 uses two-component developers for each of the colors C, M, and Y, and BX uses a one-component developer using magnetic toner. Therefore, since BK has poor transparency, when forming a transparent image on a transparent medium, the amount of BK must be significantly reduced compared to when forming a reflective image. This is because BK toner mostly creates shadows and therefore forms the maximum density on a transparent image.

Therefore, as shown in FIG. 2, the recording medium is detected by the optical sensor 20 immediately after it leaves the transparent or opaque vapor tray, and the detection result is sent as a medium signal PS to the UCR calculator 32 as shown in FIG. The UCR calculator 32 calculates UC with output characteristics as shown in FIG. 4 according to the medium signal PS.
Performs R calculation processing. For example, data as shown in FIG. 4 is stored in advance in the internal memory (not shown) of the OCR calculator 32, and the
A black data signal BK is output from the memory (lookup table) in a lookup manner based on the minimum values of Mo and Yo. In this way, since the output characteristics are switched by the medium signal PS, a recorded image of good quality can always be obtained even if the type and characteristics of the recording medium are different.

look,! Presentation 11 As a second embodiment of the present invention, the UCR calculator 32 of FIG.
When using a transparent recording medium, a good image can be obtained even if the condition is set that the BK image signal is not output. Furthermore, a well-known black character extraction circuit (not shown) is used in the commercial shown in Figure 3.
A higher quality image can be obtained by connecting between the Y conversion circuit 31 and the OCR calculator 32, recognizing black character areas with this black character extraction circuit, and applying 8 BK times signals to only the recognized black character areas. can.

Dan-” Shishiku a hill Next, a third embodiment of the present invention will be described.

Even when the surface smoothness of the recording medium differs, the influence is stronger even though the transparency of the coloring material is inferior. That is, when a recording medium with high surface smoothness and high light reflectance is used, the rate at which light passes through the coloring material, reflects on the surface of the recording medium, and then passes through the coloring material again and is emitted increases. Therefore, if the transparency of the coloring material is low when the surface smoothness is high, the output image will be dark and the saturation will be poor.

Therefore, an operation button (not shown) for selecting and instructing the surface smoothness of the recording medium is provided on the operation panel (not shown) provided in the apparatus shown in FIG. Depending on the characteristics, as described above in the first embodiment of the present invention, when the surface smoothness of the recording medium is high in the OCR calculator 32, the curve shown in FIG. Select the characteristics of B. As a result, an image of good quality can be obtained.

The present invention can be applied not only to laser beam recording devices but also, for example, to thermal transfer recording devices. FIG. 5 shows the main structure of a thermal transfer recording apparatus used in a fourth embodiment of the present invention. A roll vapor-shaped recording medium 51 is attached to the thermal head 5.
2 and an opposing roll 53, the coloring material of the color thermal transfer ribbon 54 is transferred by thermal transfer, and the ribbon is cut into sheets by a cutter 55. In the case of this example as well, since the transparency of the BK (black) color material is poor, the same UCR calculation processing as in the first to third embodiments of the present invention described above is performed by the OCR calculation unit 32. Images with good quality can be obtained.

In each of the above-described embodiments of the present invention, an example was shown in which the OCR calculation algorithm is changed when the transparency of the BK color material is lower than that of other color materials, but the present invention is not limited to this. C,M
, Y, and the optical characteristics of the recording medium, it is also effective to improve the image quality by changing the masking calculation algorithm in addition to OCR.

Furthermore, the same effect can be obtained by changing the scanning density using a calculation algorithm in a device that performs optical scanning using a laser beam or the like.

It goes without saying that the present invention is applicable not only to recording devices but also to display devices that use colorants, such as electrophotographic display devices.

It is also preferable to prepare a plurality of curves corresponding to the 8 curves shown in Fig. 4 and to be able to freely select them from the operation buttons.In this case, an image output with a color tone that matches the user's taste can be obtained. .

Furthermore, regarding the characteristics of the recording medium, the same effect can be obtained not only with the OHP film but also with a translucent back print film and the like.

[Effects of the Invention] As explained above, according to the present invention, the calculation algorithm for converting into a recording signal of each hue is changed depending on the characteristics and type of the recording medium. Even with any recording medium, it is possible to always stably obtain high-quality images by selecting the optimum combination ratio of colorants depending on the recording medium.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, FIG. 2 is a schematic sectional view showing the internal structure of an image forming apparatus according to an embodiment of the present invention, and FIG. A block diagram showing the circuit configuration of the image processing circuit, FIG. 4 is a graph showing an example of the output characteristics of the OCR calculator shown in FIG. 3, and FIG. 5 is a schematic main part of an image forming apparatus according to another embodiment of the present invention. FIG. 3 is a plan view showing the configuration. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Laser beam scanner, 3... Developing device, 4... Transfer drum, 14... Recording medium, 20... Paper quality detection sensor, 31... CMY conversion circuit, 32... OCR calculator, 33... Masking circuit, 34... PWM circuit, 35... LD driver, 36... Laser diode, 51... Recording medium, 52... - Thermal head, 54... Color thermal transfer ribbon. Figure 1 I Figure 2

Claims (1)

[Claims] 1) In an image forming apparatus that forms an image by depositing a plurality of colorants of different hues that are solid at room temperature on a recording medium, an instruction signal indicating the characteristics or type of the recording medium is provided. An image forming apparatus characterized by comprising a signal processing means for changing an arithmetic algorithm for converting an input image signal into a recording signal of each hue accordingly. 2) The image forming apparatus according to claim 1, wherein the signal processing means changes conditions for forming a black recording signal depending on the instruction signal. 3) The instruction signal indicates whether the recording medium is transparent or opaque, and the signal processing means changes the conditions for forming a black recording signal depending on whether the recording medium is transparent or opaque. The image forming apparatus described above. 4) The image forming apparatus according to claim 1, wherein the instruction signal indicates optical characteristics including surface smoothness of the recording medium. 5) The instruction signal is a detection signal of a detection means for detecting the characteristics or type of the recording medium, or a signal of an input means for inputting an instruction of the characteristics or type of the recording medium. The image forming apparatus described in .