Output method and apparatus

Abstract: An output apparatus including a memory for storing developed image data; a unit for identifying the capacity of the memory; a unit for identifying the record area on a recording medium on which the developed image data is recorded; and a unit for determining a resolution in accordance with the identified record area and the identified capacity of the storage means. An output method wherein the capacity for storing developed image data is identified; an output area for the data to be outputted is identified; and an output resolution is determined in accordance with the identified capacity and the identified output area.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an output method and apparatus allowing a variable resolution of output image data. Related Background Art Various recording apparatus having different printing processes are known, such as serial dot printers, thermal printers, LED printers, liquid crystal printers, and laser beam printers. Low cost and high resolution for better print quality are being achieved for print circuit portions of such recording apparatus, by introducing several techniques. Laser printers (hereinafter abbreviated as LBPs) are easier to improve the resolution because of their specific structure than other types of printers. Some of laser printers has a resolution of 300 dpi (dot per inch) to 600 dpi or higher. In a recording apparatus, bit image data is generated in accordance with code data supplied from a host computer or the like. For dealing with high resolution, bit image data is generated using a scalable font in place of a bit image font. A bit image font represents bit image data itself stored in a storage unit, whereas a scalable font has a variable font size such that character shape data is stored not as a bit image but as vector information, and the vector information is processed to obtain a bit image having a designated character size. The scalable font provides a smaller memory capacity and a better print quality of a magnified character than a bit map font which requires a memory capacity linearly increasing as the number of font sizes increases. The resolution of such conventional recording apparatus is however fixed. Therefore, even if a scalable font having the above-described advantages is used, a print quality is determined by the resolution specific to a recording apparatus. German Patent Specification No. DE-A-3931128 discloses an output apparatus as set forth in the preamble of claim 1 in which the output resolution can be set in accordance with an identified storage capacity. However this prior specification does not solve the problem of obtaining optimum resolution over different print areas. In accordance with one aspect of the present invention there is provided output apparatus as set out in claim 1. In accordance with a second aspect of the present invention there is provided an output method as set out in claim 9. In order that the present invention may be more readily understood, an embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 shows the relationship between a horizontal synchro signal of an LBP and a print area on a recording medium; Fig. 2 is a block diagram showing a printer according to an embodiment of this invention; Fig. 3 is a flow chart showing a control sequence of the printer according to an embodiment of this invention; and Fig. 4 shows an example of a print area for a resolution of 600 dpi relative to a print area for a resolution of 300 dpi. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following embodiments, the print process system of an LBP will be given by way of example for the discussion of this invention. The print process system of an LBP itself is well known in the art, so the description thereof will be omitted. The invention is not limited only to the following embodiments, but applicable to an apparatus constructed of a single apparatus unit and a system constructed of a plurality of apparatus units. The present invention is also applicable to the apparatus or system supplied with programs executing the concept of this invention. Fig. 1 shows the relationship between a horizontal synchro signal (a beam detect signal, hereinafter called BD) of an LBP and a print area on a recording medium on which image data is formed. Represented by a character t is a time required for a laser beam scanned by a polygon mirror to reach a print area after the falling edge timing of BD. X represents the length in the horizontal (main scan) direction of the print area, and Y represents the length in the vertical (sub scan) direction of the print area. Fig. 2 is a block diagram showing a recording apparatus according to an embodiment of this invention. In Fig. 2, an interface unit 201 (hereinafter referred to as I/F) receives data from a recording data source such as a host computer. A controller 202 controls the entire operation of the printing apparatus, analyzes command data supplied from I/F 201 to generate a bit image. A scalable font unit 203 stores, in the form of vector information, character image data corresponding to character code data sent from the data source. A calculator 204 calculates a print character bit image and an available resolution. The print character bit image is calculated from the vector information by means of interpolation for a predetermined curve such as a spline curve and a Bezier curve and by means of various algorithms. The available resolution is calculated from the memory capacity presently available. A bit map memory 205 stores bit image data to be printed. A resolution controller 206 executes physical control processes for attaining an objective resolution, such as controlling the rotation of a polygon mirror of the LBP, a paper feed speed in the sub scan direction, a laser stop, a development bias and the like. Such physical control processes are achieved by using devices well known in the art. An LBP engine 207 (hereinafter simply referred to as engine) is a printing system including the resolution controller 206. Next, the operation sequence of the LBP will be described with reference to the flow chart shown in Fig. 3. First, the LBP is powered on (step S301). The controller checks and clears each memory, initializes the I/F, and initializes circuit portions of the LBP by using user default values or the like stored in a non-volatile memory (step S302). The controller 202 determines the available capacity of the bit map memory 205 in accordance with a user default value or by calculating the size of a working area, buffer and the like used in the bit map memory. At step S304, a print area is determined by reading a designated record width from the setting of a record width designating switch. At step S305, a resolution is calculated in accordance with the bit map capacity and the print area. For example, if the capacity is 1012 K bytes and the print area is defined as shown in Fig. 1 by X = 200 mm and Y = 290 mm, then the resolution is calculated by: memory capacity (bits) ÷ X ÷ Y x 25.4 = resolution (dpi), i.e., 1012 x 1024 x8 ÷ 200 ÷ 290 x 25.4 ≃ 300 dpi. Next, the controller 202 supplies the resolution controller 206 with information that the image data to be sent is for 300 dpi, and sets the rotation speed of the polygon mirror, paper transport speed, laser spot system and the like (step S306). The controller 202 receives codes of print character data from the data source via the I/F 201 (step S307). In accordance with the vector information stored in the scalable font 203, the controller 202 develops the bit image data into the bit map memory 205 by using the calculator 204 while ensuring the designated size at the resolution of 300 dpi (step S308). After the bit image data of one page has been developed, the controller 202 actuates the printer engine 207 and sends the data in the bit map memory 205 to the printer engine 207, so that characters are printed at the designated resolution through the printing process of the LBP (step S309). The time t shown in Fig. 1 can be determined from the given rotation speed of the polygon mirror because the print area on a recording medium is definitely determined with respect to the timing when a beam detector detects a laser beam and generates a beam detector signal to generate a horizontal synchro signal. The controller 202 sends the bit image data to the printer engine 207 so as to start printing dots after the time t . Thereafter, dot data is sent at a clock speed suitable for the determined resolution. In generating clocks suitable for a determined resolution, a series of bit image transfer clocks may be selected from a plurality series of clocks stored in advance. Alternatively, it is preferable to use a programmable counter (electrically erasable programmable logics are now available in markets, with odd number division being allowed). Although not shown in Fig. 1, the number of BDs between a vertical synchro signal and the print area can be calculated from the determined resolution in the similar manner as above. In accordance with the calculated number, the controller 202 sends the bit image to the printer engine 207. In the above-described example, the whole area of the recording paper is used for printing. A user may sometimes wish to use a partial area thereof for printing. For example, as shown in Fig. 4, if a partial area defined by 100 mm x 145 mm of one page is intended to be used, the available resolution using the same bit map memory area (1012 K bytes) is given by: 1012 x 1024 x 8 ÷ 10 ÷ 145 x 25.4 ≃ 600 dpi The resolution is therefore doubled. After the resolution is determined, in the same manner as above, the controller 202 causes the resolution controller 206 to set the printing process system at 600 dpi. The controller 202 then generates image data for 600 dpi in accordance with the vector information stored in the scalable font 203, the image data being four times as much as that for 300 dpi because image data two times as much as that for 300 dpi are used in both the vertical and horizontal directions. In accordance with the determined resolution of 600 dpi and the information on the print position on a recording medium, there are calculated timings of video clocks for data transfer to the engine, a top margin, left margin, and line length of the recording medium. These calculated parameters are set in a video data transfer circuit so that characters can be printed at the resolution of 600 dpi. After the calculated parameters are set, character data for the partial record area on the recording medium is read and printed in a well known manner. In the above-described examples, characters are printed in one continuous area (in the examples, within one rectangular area). If there are provided a plurality of margin counters and a control system for the counters, characters can be printed in a plurality of separated areas. In the above embodiment, characters are printed on a partial area at a maximum resolution defined by the capacity of the bit map memory. A resolution lower than the maximum resolution may be set as desired. For example, if a resolution of 150 dpi is selected under the maximum resolution of 600 dpi, then the bit map memory can be used as four-page full bit map memories at 150 dpi. Further, the time required for bit image development per one page is shortened, thereby improving a throughput of the recording apparatus having a better flexibility in use. Instead of using the bit map memory as four-page full bit map memories at 150 dpi, it may be used for the case wherein a window is printed within one page, while ensuring a high resolution depending upon the area of the window. It is to be noted in this case that there is a tradeoff between the development time into the window and the resolution. The maximum resolution for the window is therefore determined in accordance with the memory capacity required for the window which depends on the complexity degree of image data and in accordance with the performance of development circuits. Selecting a resolution in the above-described mode may be entered from the operation panel 208 of the LBP, or may be effected by a command supplied from the data source. In the above embodiments, the same resolution is used for both in the vertical and horizontal directions. The same resolution is not necessarily required, but different resolutions may be set. For example, the present invention is applicable to printers having different resolutions between the vertical and horizontal directions, to printers having a variable resolution either in the vertical direction or in the horizontal direction, by incorporating a suitable algorithm. As described so far, according to the present invention, a print operation is executed by determining a resolution from a print area and a memory capacity, thereby providing a recording apparatus capable of changing a resolution while ensuring flexibility in use. Specifically, with a given memory capacity, a small print area and a large print area each can be printed at a maximum allowable resolution. Furthermore, if a resolution selection mode is provided, the recording apparatus more flexible in use can be realized. The capacity of the bit map memory in the above embodiments means the capacity of the memory itself or the capacity of an area of the memory allowing to store bit image.

Claims: An output apparatus for developing image data based on code data supplied from an external source and recording the developed image data on a recording medium, the apparatus comprising: storage means (205) for storing developed image data; means (S303 of Fig. 3) for identifying the capacity of said storage means; means (S306 of Fig. 3) for determining, prior to image data developing, the output resolution with which the developed image data is to be recorded in accordance with both the size of a record area on the recording medium and the identified capacity of said storage means; and means (206) for varying the output resolution of the apparatus correspondingly; characterised by means (S304 of Fig. 3) for setting the size of the record area with which the image data is to be recorded on the recording medium. Apparatus according to claim 1, wherein the means for determining the output resolution cause the output resolution to be as high as possible in accordance with the output of said identifying means. Apparatus according to claim 1 or claim 2, wherein the means for setting the size of the record area on the recording medium include means for calculating the timings of the margins in accordance with the information of the print position. Apparatus according to any preceding claim, wherein the storage means have a capacity of B kbytes, and when the record area has been set to an area of Xmm x Ymm, determining the output resolution set the output resolution as R dpi, in accordance with the following equation: R = Bx1024x8 XxY x 25.4 Apparatus according to any preceding claim, wherein the developed image data is obtained from a scalable font. Apparatus according to any preceding claim, wherein said apparatus is a laser beam printer. Apparatus according to any preceding claim, wherein said apparatus is incorporated in a system comprising a plurality of apparatuses. Apparatus according to any preceding claim, further comprising means for switching between a mode in which the output resolution is determined by said determining means and a mode in which a desired output resolution is designated in response to an instruction from outside said apparatus. A method of recording image data on a recording medium using an output apparatus for developing image data based on code data supplied from external source, storing the developed image data in storage means and recording the developed image data on a record area of the recording medium, and having a variable resolution the method comprising: setting (S304) the size of the record area with which the image data is to be recorded on the recording medium; identifying (S203) the capacity of said storage means; determining (S306) prior to image data developing, the output resolution with which the developed image data is to be recorded in accordance with both the set size of the record area and the identified capacity of said storage means; storing developed image data in the storage means (205). A method according to claim 9, wherein the output resolution is caused to be as high as possible in accordance with the identified capacity. A method according to claim 9 or claim 10 and including calculating the timings of the margins in accordance with information on the print position. A method according to any one of claims 9 to 11, wherein the storage means have a capacity of B kbytes, and when the record area has been set to an area of Xmm x Ymm, determining the output resolution set the output resolution as R dpi, in accordance with the following equation: R = Bx1024x8 XxY x 25.4 A method according to any one of claims 9 to 12, wherein the developed image data is obtained from a scalable font. A method according to any one of claims 9 to 13, wherein said apparatus is a laser beam printer. A method according to any one of claims 9 to 14, further comprising switching between a mode in which the output resolution is determined by said determining means and a mode in which a desired output resolution is designated in response to an instruction from outside said apparatus.

Inventors: IKEDA JUN, IKEDA, JUN, IKEDA, JUN, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1991
Main classification: G06K15
IPC codes: B41J2, G06K15