BACKGROUND

[O0<H | The importance of the environment has increased, and industries related to image forming apparatuses are also investing in environmental protection. However, products such as developer cartridges are consumables discarded after consumption, and thus have a negative effect on the environment. Thus, technologies for reusing waste developer have been researched.

BRIEF DESCRIPTION OF DRAWINGS

[0002] The disclosure may be understood by the following detailed description and combinations of the accompanying drawings.

[00031 FIG. 1 is a schematic diagram showing a developing unit of an image forming apparatus and a process of reusing waste developer of the image forming apparatus according to some examples.

[0004] FIG. 2 is a diagram illustrating a configuration of an image forming apparatus according to some examples.

[0005] FIG. 3 is a diagram illustrating an example of the user interface of an image forming apparatus to receive a user command.

[0006] FIG. 4 is a diagram illustrating an example of the user interface of an image forming apparatus to receive input of a user command.

[0007] FIG. 5 is a diagram illustrating an example of the user interface of an image forming apparatus 200 to receive input of a user command.

[0008] FIGS. 6A to 6C are diagrams illustrating an example of the user interface of an image forming apparatus to receive input of a user command.

[0009] FIG. 7 is a flowchart of an example method of operating an image forming apparatus. [00101 FIG. 8 is a diagram describing a use ratio of waste developer for each of a plurality of modes according to some examples.

[00111 FIG. 9 is a flowchart of an example method of operating an image forming apparatus with a mode applied.

[0012] FIG. 10 is a diagram describing a threshold range and waste developer use ratio of each of the plurality of modes according to some examples.

10013] FIG. 11 is a diagram describing a threshold range for each of a plurality of modes of an image forming apparatus, according to some examples.

[0014] FIG. 12 is a diagram describing a number of available pages of an image forming apparatus according to some examples.

[00151 FIG. 13 is a diagram describing instructions stored in a memory of an image forming apparatus according to some examples.

DETAILED DESCRIPTION

[0016] A storage amount of waste developer in a developing unit depends on environment, such as temperature and humidity, and thus, an efficient use should be planned. Furthermore, even for such waste developer, a method and apparatus for waste developer use ratio that can vary according to a user's selection have been demanded.

[0017] According to some examples, an image forming apparatus may include an interface unit to display a plurality of modes regarding a waste developer use ratio and receive input of a user command to select one of the plurality of modes. The image forming apparatus may include a processor to control an image to be developed using the waste developer use ratio corresponding to the mode selected from the interface unit. The waste developer use ratio may be a ratio of a supply amount of waste developer to a supply amount of developer.

[0018] The image forming apparatus may include a waste developer sensor corresponding to the waste developer, wherein the processor is to, when a storage amount of the waste developer obtained from the waste developer sensor exceeds a threshold value, control an image to be developed by applying the waste developer use ratio corresponding to the mode selected from the interface unit.

[0019] The processor may be to control the interface unit to display the plurality of modes in response to receiving a power supply, and control receiving a user command.

[0020] The processor may be to, in response to recognizing a cartridge replacement, control the plurality of modes to be displayed on the interface unit so that the user command is received.

[0021] The processor may be to perform development by determining the waste developer use ratio according to the selected mode.

[00221 The processor may be to, control the interface unit to display information about an expected lifespan, a number of available pages, or an expected image quality, for the selected mode or the plurality of modes.

[0023] According to some examples, an image forming apparatus may include an interface unit to display a plurality of modes regarding a waste developer use ratio and receive input of a user command to select one of the plurality of modes. The image forming apparatus may include an image density sensor to measure an image density. The image forming apparatus may include a processor to apply the waste developer use ratio, a ratio range, and a threshold range of the image density corresponding to the mode selected from the interface unit, receive an image density value measured for a test pattern, and perform development by comparing the measured image density value and the threshold range and determining the waste developer use ratio. The waste developer use ratio may be a ratio of a supply amount of waste developer to a supply amount of developer.

[0024] The ratio range may vary in a maximum value or a minimum value of an amount of waste developer or an amount of developer in each of the plurality of modes.

[0025] The processor may be to, when the measured image density exceeds an upper limit of the threshold range, and the waste developer use ratio is within the ratio range, increase the use ratio. [00261 The processor may be to, when the measured image density is less than a lower limit of the threshold range and the waste developer use ratio is within the ratio range, decrease the use ratio.

[0027] According to some examples, a method of determining a mode of an image forming apparatus may include displaying a plurality of modes regarding a waste developer use ratio, receiving input of a user command to select one of the plurality of modes, and developing an image by applying the waste developer use ratio corresponding to the selected mode, wherein the developer use ratio is a ratio of a supply amount of waste developer to a supply amount of developer.

|0028] The developing the image may include identifying a storage amount of waste developer, and when the storage amount of the waste developer exceeds a threshold value, developing the image by applying the waste developer use ratio corresponding to the selected mode.

[0029| The displaying the plurality of modes may include displaying the plurality of modes in response to receiving a power supply.

[0030] The displaying the plurality of modes may include displaying the plurality of modes in response to recognizing a cartridge replacement.

|0031] According to some examples, a non-transitory computer-readable storage medium storing instructions executable by a processor may include instructions to display a plurality of modes regarding a waste developer use ratio, and instructions to, when a user command to select one of the plurality of modes is input, develop an image by applying the waste developer use ratio corresponding to the selected mode, wherein the waste developer use ratio is a ratio of a supply amount of waste developer to a supply amount of developer.

10032] When a certain example is implemented differently, a specific order may be performed differently. For example, two consecutively described processes may be performed substantially at the same time or performed in an order opposite to a previously described order. The term "-er/or" used in some examples may indicate a computer-readable component to perform certain roles. However, the term "-er/or" is not limited to such a computer-readable component. The term "-er/or" may be in an addressable storage medium or may be to reproduce a processor.

[0033] Although the terms first, second, etc. may be used to describe various elements, components, areas, layers, operations, and/or regions, such elements, components, areas, layers, operations, and/or regions should not be limited by these terms.

10034] In the disclosure below and accompanying drawings, the expression of greater than or less than is used to determine whether a specific condition is satisfied or fulfilled, but the expression is used in a descriptive manner to explain examples, and does not exclude description of greater than or equal to or less than or equal to. "Greater than or equal to" may be replaced with "exceeding," and "less than or equal to" may be replaced with "less than," and "greater than or equal to . . . and less than. . . " may be replaced with "exceeding. . . and less than or equal to. . . " Hereinafter, examples of the disclosure are described in detail with reference to the drawings such that one of skill in the art may carry out the examples. However, the disclosure may be achieved in many different forms and is not limited to the examples set forth herein.

[0035] An "image forming apparatus" may be any type of device to form an image, such as a printer, a scanner, a fax machine, a multi -function printer (MFP), or a display device.

[0036] A "mode" may be a mode to reuse waste developer, such as "Eco-mode" or "EconoMode". When such a mode is selected, the image forming apparatus may save toner usage and cost per page, while a print quality may degrade.

[0037] FIG. 1 is a schematic diagram showing a developing unit 100 of an image forming apparatus and a process of reusing waste developer of the image forming apparatus, according to some examples.

10038] Referring to FIG. 1, the developing unit 100 of the image forming apparatus for reusing the waste developer may include a hopper 101, a developer supply unit 103, a waste developer collection unit 105, a waste developer supply unit 107, and a developing chamber 109.

[0039] The waste developer generated in the developing unit 100 may be moved to a waste developer storage unit by the waste developer collection unit 105. During a development process, the developer located in the hopper 101 may be moved to the developing chamber 109 by the developer supply unit 103, and the waste developer located in the waste developer storage unit for reuse of the waste developer may be moved to the developing chamber 109 by the waste developer collection unit 105. In this case, a total developer supplied to the developing chamber 109 may be divided into developer supplied by the developer supply unit 103 and waste developer supplied by the waste developer supply unit 107.

[0040] The image forming apparatus may drive the developer supply unit 103 and the waste developer supply unit 107 based on a mode, to determine supply amounts of the developer and the waste developer.

[0041] FIG. 2 is a diagram illustrating a configuration of an image forming apparatus 200 according to some examples.

[00421 Referring to FIG. 2, the image forming apparatus 200 may include an interface unit 210, a developing unit 220, a waste developer sensor 230, a photoconductor 240, an image density sensor 250, a memory 260, and a processor 270. However, any of said elements may be omitted. The image forming apparatus 200 may be implemented with more elements than those illustrated, or the image forming apparatus 200 may be implemented with fewer elements. The elements are described in detail below.

[00431 The interface unit 210 may be an interface with a separate input/output device. For example, the input device may be a device, such as an input button, a keyboard, or a mouse, and the output device may be provided in the form of a device, such as a display unit to display an image. In some examples, the interface unit 210 may be an interface with a device in which functions for input and output are integrated into one, such as a touch screen. Specifically, when the processor 270 of the image forming apparatus 200 processes a command of a loaded program, a service screen or content based on data provided by the image forming apparatus 200 may be displayed through the interface unit 210. In addition, the interface unit 210 may provide a user interface (UI) screen through the display or the like and change a screen of the UI in response to a user command.

[0044| The interface unit 210 may display a plurality of modes regarding a waste developer use ratio. In addition, the interface unit 210 may receive input of a user command to select at least one of the plurality of modes. For example, the plurality of modes may indicate a degree corresponding to a level of an eco-mode as an index. For example, in each of the plurality of modes, a waste developer use ratio, which is a ratio of a supply amount of waste developer to a supply amount of developer, may be set. In addition, the interface unit 210 may receive input corresponding to an output type for the plurality of modes, by a user command. For example, the output type may include types, such as graphic and text.

[00451 The developing unit 220 may correspond to the developing unit 100 of FIG. 1. The developing unit 220 may include the developing chamber 109 in which developer and waste developer may be stored, the developer supply unit 103 to supply the developer to the developing chamber 109, and the waste developer supply unit 107 to supply the waste developer to the developing chamber 109.

[0046| The waste developer sensor 230 may be a sensor related to a storage amount of the waste developer in the developing unit 220. For example, the waste developer sensor 230 may measure a storage amount of the waste developer in the waste developer storage unit. Alternatively, the waste developer sensor 230 may be a toner concentration (TC) sensor and may measure a mixing ratio (TC ratio) of a total developer in the developing chamber 109, and the mixing ratio may be determined by [Mathematical Formula 1] shown below. In this case, toner and carrier may be mixed in the total developer.

[0047] [Mathematical Formula 1]

[0048] TC ratio ⁼ C/Ttotal ^x 100% ⁼ C/(Tnormal "tTreuse) ^x 100%

[0049] In Mathematical Formula 1, C(g) is a weight of the carrier, Ttotai(g) is a weight of the total toner, Tnormai(g) is a weight of the toner, and Treuse(g) is a weight of the waste toner.

[0050] The processor 270 may obtain the storage amount of the waste developer based on a value measured by the waste developer sensor 230.

10051] The photoconductor 240 forms an electrostatic image on a surface thereof such that the toner included in the developer may be developed on the surface of the photoconductor 240. [00521 The image density sensor 250 may measure a density of an image formed on the photoconductor 240 or an intermediate transfer belt. Specifically, the image density sensor 250 may measure the image density of a test pattern formed on the photoconductor 240 and the intermediate transfer belt. Such a test pattern may indicate a pattern to measure an image density by transferring developer to the photoconductor 240 or the intermediate transfer belt. For example, the image density sensor 250 may be a color toner density (CTD) sensor.

[00531 The memory 260 may store programs, data, or files related to the image forming apparatus 200. The processor 270 may execute a program stored in the memory 260, read data or a file stored in the memory 260, or store a new file in the memory 260. The memory 260 may store program commands, data files, data structures, etc. alone or in combination. The memory 260 may store instructions executable by the processor 270. For example, the memory 260 may store instructions to display a plurality of modes regarding a waste developer use ratio, instructions to receive input of a user command to select one of the plurality of modes, and instructions to develop an image by applying the waste developer use ratio corresponding to the selected mode.

[0054] The processor 270 may control overall operations of the image forming apparatus 200. In addition, the processor 270 may control the image forming apparatus 200 to perform the operations shown in the drawings.

[0055] The processor 270 may identify the mode selected by the user command and apply the waste developer use ratio corresponding to the selected mode, so that an image is developed. The processor 270 may obtain a storage amount of waste developer based on a value measured by the waste developer sensor 230, develop an image by applying a mode when the waste developer storage amount exceeds a threshold value, and develop the image without applying the mode when the waste developer storage amount is less than or equal to the threshold value.

|0056] In addition, the processor 270 may develop an image by identifying a mode selected by a user command and applying a use ratio of the waste developer, a ratio range, and a threshold range corresponding to the selected mode. The ratio range may denote a maximum or minimum value of an amount of waste developer or developer used according to each of the plurality of modes, and the threshold range may denote an upper limit or a lower limit value of image density according to each of the plurality of modes. The ratio range and the threshold range are described in detail with reference to FIG. 10.

[0057] For example, when a measured image density is less than a lower limit of a threshold range, the processor 270 may decrease the waste developer use ratio. When a measured image density exceeds an upper limit of a threshold range, the processor 270 may increase the waste developer use ratio.

[0058] The processor 270 may adaptively determine the use ratio based on an image density and a ratio range. For example, when a measured image density is less than a lower limit of a threshold range and the waste developer use ratio is within the ratio range, the processor 270 may decrease the waste developer use ratio. When a measured image density exceeds an upper limit of a threshold range and the waste developer use ratio is within the ratio range, the processor 270 may increase the waste developer use ratio.

[0059] The processor 270 may control a plurality of modes to be displayed on the interface unit 210 in response to receiving a power supply, and control a user command to be received. In addition, in response to recognizing a cartridge replacement, the processor 270 may control the plurality of modes to be displayed on the interface unit 210 and control a user command to be received. The processor 270 may control the interface unit 210 to display at least one of information indicating an expected lifespan, a number of available pages, and an expected image quality corresponding to the selected mode.

[0060] The processor 270 may calculate the number of available pages. For example, the processor may calculate a second page number corresponding to the selected mode based on a first page number and the waste developer use ratio. The first page number may indicate the number of available pages when the mode is not applied, and the second page number may indicate the number of available pages when the mode is applied. An operation of the processor 270 to calculate the first page number and the second page number is described in detail with reference to FIG. 12.

10061] The processor 270 may be or include, but not limited to, a digital signal processor (DSP), which processes a digital signal, a microprocessor, or a time controller (TCON). The processor 270 may include a central processing unit (CPU), a micro controller unit (MCU), a micro processing unit (MPU), a controller, an application processor (AP), a communication processor (CP), or an Acorn RISC Machine (ARM) processor. The processor 270 may be defined by terms corresponding to those described above. In addition, the processor 270 may be or include a system on chip (SoC) having a built-in processing unit, and a large scale integration (LSI). The processor 270 may be or include a field programmable gate array (FPGA).

[00621 FIGS. 3 to 6C show various examples of a user interface of the interface unit 210 of an image forming apparatus to receive input of a user command. The interface unit 210 in FIGS. 3 to 6C may be divided into an input device and an output device, and the user interface may be implemented with the input device and the output device. A user interface screen (layer) may be displayed by the output device, and a mode may be selected by receiving a user command from the input device. The interface unit 210 may display output types along with a plurality of modes. The interface unit 210 may be to select one of the plurality of modes or to receive input corresponding to an output type.

[0063] FIG. 3 is a diagram illustrating an example of the user interface of the image forming apparatus 200 to receive a user command, according to some examples.

[0064] Referring to FIG. 3, the user interface may be implemented through an input/output device included in the image forming apparatus 200. A screen 310 of the user interface may display a plurality of modes or receive input corresponding to one of the plurality of modes based on an input button 320 of the user interface. For example, when a user presses the Eco Mode On button on the input button 320, the f screen 310 may display the plurality of modes. In addition, when the user presses the button 2 on the input button 320, the Mode Level 2 is selected, and the processor 270 may control an image to be developed by applying a waste developer use ratio corresponding to the Mode Level 2.

[0065[ FIG. 4 is a diagram illustrating an example of the user interface of the image forming apparatus 200 to receive input of a user command, according to some examples.

[0066] The user interface may be implemented through an input/output device included in a computer device. An example user interface screen may display a plurality of modes 410 and output types 420. A user may select a mode and an output type through the input/output device of the computer device, and the computer device may transmit the mode and output type to the image forming apparatus 200. [0067] FIG. 5 is a diagram illustrating an example of the user interface of the image forming apparatus 200 to receive input of a user command, according to some examples.

[0068] The user interface may be implemented by using a dial button of the image forming apparatus 200 as an input device and a display as an output device.

[0069] The user interface may include a menu through overlapping menus. The image forming apparatus 200 may display a menu and receive input of a dial button from a user, in operation 510, display a mode setting and receive input of the dial button from the user, in operation 520, display a plurality of modes and receive input of the dial button from the user, in operation 530, and display output types and receive input of the dial button from the user, in operation 540.

|0070] FIGS. 6A to 6C are diagrams illustrating an example of the user interface of an image forming apparatus to receive input of a user command, according to some examples.

[0071] The user interface may be implemented by using a control touch panel as an input/output device.

[0072] In FIGS. 6A to 6C, the user interface may display information indicating each of a plurality of modes on a first screen area 610 and display output types on a second screen area 620. In addition, setting information for each mode may be displayed. For example, the user interface may display an increase rate of a number of available pages on a third screen area 630, display the number of available pages in a fourth screen area 640, and display an expected image quality on a fifth screen area 650 with a different contrast for each mode.

[0073 [ For example, referring to FIG. 6A, the user interface may display information on the Mode Level 1 in the first screen area 610, display no output type in the second screen area 620, display 5% increase in the number of available pages and 15800 sheets available, in the third screen area 630, and display the expected image quality in contrast in the fourth screen area 640.

[0074] The image forming apparatus 200 in FIGS. 3 to 6C may display an alarm to receive input of a user command. For example, an alarm and a plurality of modes may be displayed so that a user command is input, in response to at least one of when a printer is installed for the first time and a power is supplied, when a toner cartridge has reached the end of its lifespan and a new toner cartridge is installed, when the lifespan of the toner cartridge has reached a certain area (e.g., alarm by 10 % or alarm at 50 % or less), when a number of print jobs exceeds a certain number, when there are more than a certain number of graphic images (e.g., greater than or equal to 100 or greater than or equal to 10 graphic images regardless of an image type).

[00751 FIG. 7 is a flowchart of an example method of operating an image forming apparatus, according to some examples, and FIG. 8 is a diagram describing a use ratio of waste developer for each of a plurality of modes, according to some examples.

[0076] Referring to FIG. 7, the image forming apparatus 200 may display a plurality of modes regarding a waste developer use ratio, in operation S701. For example, an alarm and the plurality of modes may be displayed so that a user command may be input, in response to at least one of when a printer is installed for the first time and a power is supplied, when a toner cartridge has reached the end of its lifespan and a new toner cartridge is installed, when the lifespan of the toner cartridge has reached a certain area (e.g., alarm by 10 % or alarm at 50 % or less), when a number of print jobs exceeds a certain number, when there are more than a certain number of graphic images (e.g., greater than or equal to 100 or greater than or equal to 10 graphic images regardless of an image type).

[0077] The image forming apparatus 200 may receive input of a user command, in operation S703. The image forming apparatus 200 may receive input of one of the plurality of displayed modes as a user command or may receive input corresponding to an output type as a user command.

[0078] The image forming apparatus 200 may identify a storage amount of waste developer to apply a mode selected by the user command, in operation S705. For example, the image forming apparatus 200 may obtain the storage amount of the waste developer based on a value measured by the waste developer sensor 230. For example, when the waste developer sensor 230 measures the storage amount of the waste developer in the waste developer storage unit, a measured value of the storage amount of the waste developer may be obtained. Alternatively, when the waste developer sensor 230 measures a mixing ratio of a total developer in the developing chamber 109, the storage amount of the waste developer may be calculated based on the mixing ratio. [00791 The image forming apparatus 200 may determine whether a mode is to be applied, based on the storage amount of the waste developer, in operation S707. The image forming apparatus 200 may identify whether the storage amount of the waste developer is less than or equal to a threshold value.

[0080] When the storage amount of the waste developer is less than or equal to the threshold value, the image forming apparatus 200 may proceed to operation S709 and may not apply the mode. When the storage amount of the waste developer exceeds the threshold value, the image forming apparatus 200 may proceed to operation S711.

[0081] The image forming apparatus 200 may obtain an output type and identify whether the output type corresponds to a current output, in operation S711. When the output type does not correspond to the current output, the image forming apparatus 200 may proceed to operation S709 and may not apply the mode. In addition, when the output type corresponds to the current output, the image forming apparatus 200 may proceed to operation S713 and apply the mode.

[0082] The image forming apparatus 200 may apply a waste developer use ratio corresponding to the selected mode, in operation S713.

10083] For example, referring to FIG. 8, each of the plurality of modes represents a waste developer use ratio of each of the plurality of modes. In this case, the plurality of modes may be divided into Off, Level 1, Level 2, and Level 3. The waste developer use ratio may be 0 % at Off, 5 % at Level 1, 10 % at Level 2, and 15 % at Level 3. An expected image quality and expected image density degradation level according to the waste developer use ratio may be set differently in each of the plurality of modes.

10084] The image forming apparatus 200 may develop an image by applying or not applying the mode, in operation S715.

[0085] FIG. 9 is a flowchart of an example method of operating the image forming apparatus 200 with a mode applied, according to some examples, and FIG. 10 is a diagram describing a threshold range and waste developer use ratio of each of the plurality of modes, according to some examples. An operation of the image forming apparatus 200 in FIG. 9 may be independent of or linked to the operation of the image forming apparatus 200 in

FIG. 7.

[0086] Referring to FIG. 9, operations S901 to S903 of the image forming apparatus 200 may correspond to operations S701 to S703 in FIG. 7.

[0087] The image forming apparatus 200 may measure an image density of a test pattern formed on the photoconductor 240 or the intermediate transfer belt. Such a test pattern may indicate a pattern to measure an image density by transferring developer to the photoconductor 240 or the intermediate transfer belt.

[0088| The image forming apparatus 200 may apply a waste developer use ratio, a ratio range, and a threshold range corresponding to the selected mode. The ratio range may denote a maximum or minimum value of an amount of waste developer or developer used according to each of the plurality of modes, and the threshold range may denote an upper limit or a lower limit value of the image density according to each of the plurality of modes. For example, referring to FIG. 10, in the Mode Level 1, the image forming apparatus 200 may apply a mode by setting an initial waste developer use ratio to 10 %, a waste developer ratio range to 0 to 15 %, and a development density threshold range to 1.13 to 1.38. When a mode is applied, the image forming apparatus 200 may perform adaptive determination based on the initial waste developer use ratio, ratio range, and threshold range corresponding to the selected mode, such as increasing or decreasing a waste developer use ratio.

[0089] The image forming apparatus 200 may determine whether the measured image density is within a threshold range included in the mode, in operation S907. Specifically, the image forming apparatus 200 is either to increase the waste developer use ratio or to decrease the waste developer use ratio.

[0090] When the image forming apparatus 200 increases the waste developer use ratio is described below.

[0091] When a measured image density exceeds an upper limit of a threshold range, the image forming apparatus 200 may proceed to operation S909. When the waste developer use ratio is within a ratio range in operation S909, the image forming apparatus 200 may proceed to operation S911 and increase the waste developer use ratio.

[0092] When the image forming apparatus 200 decreases the waste developer use ratio is described below.

[0093] When the image density is less than a lower limit of a threshold range in operation S915, the image forming apparatus 200 may proceed to operation S917. When the waste developer use ratio is within a ratio range in operation S917, the image forming apparatus 200 may proceed to operation S919 and decrease the waste developer use ratio.

[00941 When a measured image density is less than or equal to an upper limit of a threshold range and greater than or equal to a lower limit of a threshold range, the image forming apparatus 200 may proceed to operation S913 and apply a mode without changing the waste developer use ratio.

[0095] When the waste developer use ratio is out of a ratio range in operation S909, the image forming apparatus 200 may proceed to operation S921 and process as an exception, and when the waste developer use ratio is out of a ratio range in operation S917, the image forming apparatus 200 may proceed to operation 921 and process as an exception.

[0096] In operation S921, the image forming apparatus 200 may not apply a mode or may apply a mode differing in the threshold range and the ratio range from the threshold range.

[0097] FIG. 11 is a diagram describing a threshold range for each of a plurality of modes of the image forming apparatus 200, according to some examples.

[0098] As described above, the image forming apparatus 200 may determine an initial waste developer use ratio, ratio range, and threshold range according to a mode. In addition, the image forming apparatus 200 may perform adaptive determination, such as increasing or decreasing a waste developer use ratio, based on the initial waste developer use ratio, ratio range, and threshold range.

[0099] Referring to FIG. 11, a threshold range of an image density is shown for each mode. For example, when the mode is the Mode Level 1 and the image density is less than 1.13, the image forming apparatus 200 may identify whether the waste developer use ratio is within the ratio range, and decrease the waste developer use ratio.

[01001 When the mode is the Mode Level 1 and the image density is greater than 1.38, the image forming apparatus 200 may identify whether the waste developer use ratio is within the ratio range, and increase the waste developer use ratio.

[0101] The image density increases as the waste developer use ratio decreases, and the image density decreases as the waste developer use ratio increases.

[0102] FIG. 12 is a diagram describing a number of available pages of the image forming apparatus 200 according to some examples.

[0103] The image forming apparatus 200 calculates the number of available pages, according to some examples, depending on whether a mode is not applied and the waste developer is not used, and whether the mode is applied and the waste developer is used. Hereinafter, operations include calculating a first page number when the image forming apparatus 200 does not apply a mode, and calculating a second page number when the image forming apparatus 200 applies a mode.

[0104] For example, when a mode is not applied, the image forming apparatus 200 may calculate a toner remaining gauge by counting motor slits of a developer supply unit. This may be expressed by [Mathematical Formula 2],

10105] [Mathematical F ormula 2]

[0106] G is a toner remaining gauge, Nmax is a maximum number of slit counts, and Ncount is a number of slit counts.

[0107] In this case, the number of available pages may be expressed by [Mathematical Formula 3] shown below.

[0108] [Mathematical Formula 3]

Npage — a X G [0109| Npage is a number of available pages, G is a toner remaining gauge, and a is a predetermined constant. As shown in [Mathematical Formula 3], the number of available pages may be determined by the toner remaining gauge.

[0110] Referring to FIG. 12, there is a difference in a change rate of the toner gauge according to each mode. Accordingly, when the image forming apparatus 200 uses waste developer by using an Eco mode, a method of estimating the number of available pages may change.

[01H | The image forming apparatus 200 may calculate the toner remaining gauge by counting the motor slits of the developer supply unit. The toner remaining gauge is a value based on the motor slits of the developer, regardless of whether the waste developer is used. Accordingly, the toner remaining gauge may be expressed by [Mathematical Formula 2] as before.

[0112| The number of available pages has a different gauge change rate for each level setting of an Eco mode. Specifically, the number of available pages may be expressed by [Mathematical Formula 4] shown below.

[0113] [Mathematical Formula 4]

N _Daee = a X (1 + b) X G

1 114] Npage is the number of available pages, G is a toner remaining gauge, a is a predetermined constant, and b is a waste developer use ratio. For example, assuming that a waste developer use ratio in the Mode Level 2 is 10 %, the number of available pages may

[0115| The image forming apparatus according to some examples may determine a waste developer use ratio according to level settings, so that output cost or degree of environmental protection may vary according to a user's selection.

[0116] FIG. 13 is a diagram describing instructions stored in a memory of an image forming apparatus, according to some examples. [0117] Referring to FIG. 13, the image forming apparatus 200 may include the memory 260 and the processor 270. In this regard, descriptions overlapping those of FIG. 2 may be omitted below.

[0118] The memory 260 may store a computer executable instruction. The processor 270 of the image forming apparatus 200 corresponds to some examples of a computer executing a computer executable instruction.

[0119j The memory 260 may store instructions 261 to display a plurality of modes regarding a waste developer use ratio, or instructions 263 to, in response to receiving a user command to select one of the plurality of modes, develop an image by applying the waste developer use ratio corresponding to the selected mode.

|0120] Meanwhile, the operating method of the image forming apparatus 200 described above may be implemented in the form of a computer-readable storage medium that stores instructions or data executable by a computer or processor. The operating method may be written as a program that may be executed on a computer, and may be implemented in a general-purpose digital computer that operates such a program by using a computer- readable storage medium. Such a computer-readable storage medium may be read-only memory (ROM), random-access memory (RAM), flash memory, CD-ROMs, CD-Rs, CD+Rs, CD-RWs, CD+RWs, DVD-ROMs, DVD-Rs, DVD+Rs, DVD-RWs, DVD+RWs, DVD-RAMs, BD-ROMs, BD-Rs, BD-R LTHs, BD-REs, magnetic tape, floppy disks, magnet optical data storage devices, optical data storage devices, hard disks, solid-state disks (SSDs), and any device that is capable of storing instructions, related data, data files, and data structures, and providing instructions, related data, data files, and data structures to a processor or computer such that the processor or computer may execute the instructions.

[0121 [ As described above, although the examples have been described with respect to limited examples and drawings, those skilled in the art may make various modifications and variations from the above description. For example, appropriate results may be achieved even when the described techniques are performed in an order different from the order of the described method, or when elements of the described system, structure, device, circuit, etc. are combined differently from the described method, replaced with or substituted by other elements or equivalents. [0122| Therefore, the scope of the disclosure should not be limited to any of the abovedescribed examples.

[0123] It should be understood that examples described herein should be considered in a descriptive manner, not for purposes of limitation. Descriptions of features or aspects within each example should be considered as available for other similar features or aspects in other examples. While examples have been described with reference to the drawings, it would be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure.