JPS62233979A - Picture processor - Google Patents

Abstract

PURPOSE:To simply adjust the level of picture data or the level of a reference signal by providing a data generating means for generating prescribed data and a level adjusting means for a signal. CONSTITUTION:A selector 10 selects either one of video data form a latch circuit 20 and data from a video data generator 11 and outputs. A switch 13 is connected to a contact (b) to select the B input of the selector 10 and the data 00 is outputted from the video data generator 11. The output of a D/A converter 22 at this time is compared with a chopping wave 15 and the bias value of the chopping wave 15 is changed by a variable resistance 34 so as to obtain a prescribed minimum pulse duration. The output of the video data generator 11 is made FF, the output voltage level of the D/A converter 22 is changed by a variable resistor 23 to adjust so as to have the prescribed value of a maximum pulse duration.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention compares a signal obtained by converting a digital image signal into an analog image signal with a reference signal of a predetermined period to obtain a binarized image signal which is pulse width modulated. The present invention relates to an image processing device that outputs images.

[Prior Art] When converting a digital image signal into a binary value and forming an image using a laser beam printer, the digital image signal is converted to an analog signal in order to obtain halftone gradation, and this converted signal is converted into an analog signal. For example, a method has been proposed in which a binarized signal subjected to pulse width modulation is generated by comparing it with a periodic pattern signal such as a triangular wave. In this method, in order to obtain high gradation, the D/A
The relationship between the level of the analog video signal 30.degree. 31, which is the output of the converter, and the level of the triangular wave 32 is such that the triangular wave 32 is preferably between the maximum analog video signal and the minimum analog video signal. FIG. 2 shows a conventional example proposed for this purpose.

A conventional example will be described below with reference to FIG.

The 8-bit digital video signal is latched by a latch circuit 20 using a video clock 21. This video clock 2
1 is a clock synchronized with a digital video signal sent from, for example, an image scanner (not shown). This video signal is converted into an analog video signal by the D/A converter 22. This analog video signal is converted into an arbitrary voltage by a variable resistor 23. This voltage is input to one input terminal of the comparator 24. On the other hand, the screen clock is frequency-divided by two by a frequency divider 25 to become a clock signal 26 with a duty ratio of 50%. This screen clock is also synchronized with the video clock 21, and is a signal sent from, for example, an image scanner (not shown). This clock signal 26
passes through a buffer 27, and a triangular wave is formed by an integrating circuit composed of a resistor 28 and a capacitor 29. Then, the bias amount is adjusted using a capacitor 33 and a variable resistor 34, and the signal is inputted to the other input terminal of the comparator 24 through a protective resistor 35 and a buffer amplifier 36, and is compared with the analog video signal from the D/A converter 22. Width modulated.

As mentioned above, in order to maintain high gradation, it is desirable to have the relationship between the analog signal and pattern signal as shown in Figure 3, but in reality, due to the responsiveness of the semiconductor laser and the sensitivity of the drum, the relationship shown in Figure 4 is desirable. A relationship between the minimum pulse and the maximum pulse as shown in is desired. This relationship is determined by the variable resistor 34 for offset adjustment of the integrating circuit and the D/A converter 22.
The output voltage is adjusted using the variable resistor 23 for adjusting the output voltage. That is, 8
A bit digital video signal is supplied from another input device (not shown), and first, OO is supplied and the minimum pulse width is determined by the offset adjustment variable resistor 34.

Next, input the hexadecimal number F from the input device (not shown) in the same way.
Adjust the variable resistor 23 so that the output voltage of the D/A converter 22 changes from a voltage value of 40 to a voltage value of 41 as shown in the figure, and adjust so that the desired maximum pulse width is obtained. .

[Problem to be Solved by the Invention 1] As mentioned above, in the conventional example, when adjusting the pulse width, it is necessary to provide digital data for adjustment from the outside, so it is necessary to prepare a separate jig etc. Moreover, there was a drawback that it took a long time for adjustment. Furthermore, if this device, which has been adjusted once, needs to be readjusted due to changes in the characteristics of the drum, laser, etc. over time, etc.
This has the disadvantage that a special device for inputting video data for adjustment is required.

The present invention has been made in view of the above-mentioned conventional example, and an object of the present invention is to provide an image processing device that is equipped with a generating means that can generate arbitrary digital data and can easily adjust the level of image data and the level of a reference signal. do.

[Means for Solving the Problems] The image processing apparatus of the present invention includes a converting means for converting an input digital image signal into an analog image signal, a means for generating a reference signal with predetermined synchronization, and a converting means for converting an input digital image signal into an analog image signal. An image processing device that outputs a binary image signal pulse-width modulated by comparing it with the reference signal, the device comprising: data generating means for generating predetermined data; and selecting the predetermined data and the digital image signal. and an adjusting means for adjusting the levels of the reference signal and the analog image signal.

[Operation] In the above configuration, the data generation means outputs predetermined data, and adjusts the levels of the image signal and reference signal corresponding to the data by the adjustment means, thereby adjusting the pulse width of the binarized image signal. .

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Description of Image Processing Section (FIGS. 1 and 4)] FIG. 1 is a block diagram of an image processing section of an image processing apparatus according to an embodiment of the present invention. In this figure, parts that are the same as those in FIG. 2 are indicated by the same symbols, and the explanations thereof will be omitted because they are the same as those in the conventional example.

A selector 10 selects and outputs either the 8-bit video data from the latch circuit 20 or the data from the video data generator 11. 11 is a video data generator, which can generate any 8-bit video signal, that is, 0 to 25;
A video signal with 5 (256) gray levels can be generated. In this embodiment, settings are made to output two types of data (00 and FF). Reference numeral 13 denotes a switch for selecting manual power A and B of the selector 10. When the switch 13 is connected to contact a, the select signal 14 becomes high level, and for example, manual power A is selected and is latched in the D/A converter 22. Digital video data from circuit 20 is output. Conversely, when switch 13 is connected to contact point B
The input is selected and the data from the video data generator 11 is output to the D/A converter 22.

In this configuration, first, the switch 13 is connected to the contact point so that the B input of the selector 10 is selected. Next, the video data generator 11 outputs data "00". The output of the D/A converter 22 at this time is compared with the triangular wave 15, and the bias value of the triangular wave 15 is changed by the variable resistor 34 so that a predetermined minimum pulse width is obtained. This refers to the determination of the minimum pulse width 43 obtained by the voltage value 42 and the triangular wave 15 in FIG. This minimum pulse width is determined by the image processing characteristics of the device.

Next, the output of the video data generator 11 is set to "FF'" and compared with the triangular wave 15 to obtain the maximum pulse width. If the voltage value when the human power of the D/A converter 22 is "FF" is 40, and the maximum pulse width does not reach the predetermined width, the output voltage level of the D/A converter 22 is set to 40 using the variable resistor 23. to 41. This adjusts the maximum pulse width to a predetermined value.

Note that the switch 13 and video data generator 11 of this embodiment are not limited to these, and may be configured to be set by, for example, a CPU.

As explained above, according to this embodiment, the image processing apparatus is provided with a normal image processing mode and a PWM modulation pulse width adjustment mode, and by making it possible to switch between the modes, the present apparatus This has the effect that there is no need to have a separate data setting device.

Furthermore, for example, when replacing the drum, readjustment of the laser and drum when they change over time can be easily performed. Furthermore, this has the effect that good image quality can be maintained for a long time.

[Effects of the Invention] As described above, according to the present invention, there is an effect that the level of image data and the reference signal to be compared with the image data can be easily adjusted.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the image processing unit of the image processing device according to the embodiment of the present invention, Fig. 2 is a block diagram of the image processing unit of the conventional example, and Fig. 3 is a diagram showing the level conditions of the analog video signal and the triangular wave. , FIG. 4 is a diagram showing an example of adjusting the pulse width. In the figure, 10...Selector, 11...Video data generator, 13...Switch, 14...Select signal,
20...Latch circuit, 21...Video clock, 2
2... D/A converter, 23.34... Variable resistor, 24... Comparator.

Claims (1)

[Claims] a conversion means for converting an input digital image signal into an analog image signal; a means for generating a reference signal with a predetermined cycle;
An image processing device that compares the analog image signal and the reference signal and outputs a pulse-width modulated binary image signal, the image processing device comprising: data generating means for generating predetermined data; and the predetermined data and the digital image. a selection means for selecting a signal and inputting the selected signal to the conversion means; and an adjustment means for adjusting the levels of the reference signal and the analog image signal,
An image processing device characterized in that the pulse width of the binarized image signal is adjusted based on the predetermined data.