WO2011122887A2

WO2011122887A2 - Defrosting system and method of refrigerator

Info

Publication number: WO2011122887A2
Application number: PCT/KR2011/002245
Authority: WO
Inventors: Seoyoung Kim
Original assignee: Lg Innotek Co., Ltd.
Priority date: 2010-04-02
Filing date: 2011-03-31
Publication date: 2011-10-06
Also published as: KR20110110984A; WO2011122887A3

Abstract

The present invention relates to a defrosting system of an evaporator in a refrigerator, comprising: a camera capturing a status of frost formed at the evaporator; a controller calculating a frost level value by receiving a captured image from the camera and outputting a defrosting operation control signal responsive to the calculated frost level value, wherein the camera captures the status of frost at a predetermined interval, and is turned on for pre-heat operation prior to start of image-capturing.

Description

DEFROSTING SYSTEM AND METHOD OF REFRIGERATOR

The teachings in accordance with the exemplary embodiments of this invention relate generally to a defrosting system and a method of refrigerator, and more particularly to a system monitoring generation of frost in an evaporator of a refrigerator using a camera and removing the frost, and a method using the system.

Generally, a refrigerator is a type of home appliance used for freshly storing foods in a refrigerated or frozen state. A typical refrigerator is configured to generate cold air generated by heat exchange with an evaporator, blow such cold air to an inner space, namely, in refrigerating chamber and a freezing chamber where foods are stored, thus to perform refrigerating and freezing functions.

The cold air that has circulated interiors of the refrigerating chamber and the freezing chamber is supplied to a heat exchange chamber where the evaporator is installed through a predetermined circulating route. The refrigerator is such that an outside air is introduced thereinto through opening/closing of a door to circulate thereinside along the circulating route.

At this time, since the surface temperature of the evaporator provided in the refrigerator is lower than the temperature of the air within the refrigerator, moisture mixed with the air inside the refrigerator is deposited on the surface of the evaporator in the form of frost. This frost causes a bad effect on the evaporator's capability for heat exchange and has a bad influence on a passage of air passing the evaporator, such that if the frost is solidified over a predetermined level, a defrosting operation is performed using a defrosting heater such as an electric heater to remove the frost deposited on the evaporator.

If the evaporator is covered with frost, it causes deterioration in the thermal efficiency of the evaporator. Therefore, there is a need for removal of the frost. An operation of the refrigerator to remove the frost is conventionally called a "defrosting operation".

The defrosting heater is typically installed underneath the evaporator, which is to conventionally heat the evaporator by allowing heat generated by the defrosting heater to move upstream.

Meanwhile, if the defrosting operation is performed, an electric power is applied to the defrosting heater to melt down the frost solidified on a surface of the evaporator positioned near to the defrosting heater, and the heat from the defrosting heater is gradually transmitted upwards by convention to gradually melt down the frost formed on the surface of the evaporator.

The defrosting heater controls operation only at preset intervals in consideration of opening/closing counts of a refrigerator door. However, in such a case the defrosting operation may be performed even when it is unnecessary.

That is, a frequent defrosting operation raises an interior temperature. If the defrosting heater is heated at a temperature higher than 360℃ due to inaccurate defrosting system, the refrigerating and freezing efficiency decreases. If the defrosting heater is not performed at an opportune time due to failure to cope with environment changes inside the refrigerator that fluctuate based on situations inside the refrigerator, the refrigerating and freezing efficiency also decreases.

Thus, if an opened time of a door is prolonged, the defrosting heater has to frequently operate to the disadvantage of decreasing the defrosting accuracy and efficiency.

The present invention is provided to solve the abovementioned problems, and it is an object of the present invention to provide a defrosting system of a refrigerator configured to accurately determine whether defrosting operation for removing frost formed on a refrigerator is performed by using a camera, and to prevent unnecessary defrosting operation by adequately coping with environments that fluctuate based on situations inside the refrigerator, and a method using the same.

Technical problems to be solved by the present invention are not restricted to the above-mentioned descriptions, and any other technical problems not mentioned so far will be clearly appreciated from the following description by skilled in the art.

An object of the invention is to solve at least one or more of the above problems and/or disadvantages in a whole or in part and to provide at least the advantages described hereinafter. In order to achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described, and in one general aspect of the present invention, there is provided a defrosting system of an evaporator in a refrigerator, comprising: a camera capturing a status of frost formed at the evaporator; a controller calculating a frost level value by receiving a captured image from the camera and outputting a defrosting operation control signal responsive to the calculated frost level value, wherein the camera captures the status of frost at a predetermined interval, and is turned on for pre-heat operation prior to start of image-capturing.

Therefore, the present invention is advantageous in that an erroneous operation by the camera due to moisture, or frosting phenomenon of the camera can be removed in advance by the pre-heat operation.

Preferably, the controller converts the inputted captured image to a gray scale, calculates a ratio of a white area to an entire area of the converted gray scale image and determines the ratio as the frost level value.

Preferably, the ratio of white area to an entire area of the converted gray scale image is a ratio of number of white pixels to number of entire pixels of gray scale image.

Preferably, gray scale level of each pixel in the converted gray scale image is checked and if the gray scale level is higher than a predetermined value, a pixel corresponding thereto is determined as the white pixel.

Preferably, the defrosting system of an evaporator in a refrigerator is further comprising a light source for providing an illumination to the camera, wherein the light source has an ON/OFF period which is same as a capturing period of the camera.

Preferably, the controller outputs a defrosting start control signal if the frost level value is higher than the predetermined value, and outputs a defrosting stop control signal, if the frost level value calculated by input of a captured image of next period is less than the predetermined value.

Preferably, the camera is turned on prior to capturing time to thereby have a pre-heat time for pre-heating.

In another general aspect of the present invention, there is provided a defrosting method of an evaporator in a refrigerator, comprising: obtaining a captured image of an evaporator (first step); converting the image obtained in the first step to a gray scale image, and calculating a ratio of white area to the converted gray scale image (second step); and outputting a defrost start command if the ratio of white area calculated from the second step is higher than a predetermined threshold value (third step).

Preferably, the method is further comprising outputting a defrost stop command after the third step if the ratio of white area calculated by repeating the first and second steps is less than a predetermined threshold value (fourth step).

Preferably, the ratio of white area in the second step is calculated by a ratio of the number of white pixels to the number of entire pixels, where the white pixels are determined by gray level of each pixel of the gray scale image.

In still another general aspect of the present invention, there is provided a defrosting system of an evaporator in a refrigerator, comprising: a light source irradiating light to an evaporator of a refrigerator; a camera continuously capturing status of frost formed on the evaporator reflected by the light of the light source at a predetermined interval; and a controller calculating a frost level value by receiving a captured image from the camera and outputting a defrosting operation control signal responsive to the calculated frost level value.

Preferably, the light source has an ON/OFF period which is same as a capturing period of the camera.

In still further general aspect of the present invention, there is provided a defrosting method of an evaporator in a refrigerator, comprising: applying an electric power to a light source to illuminate the evaporator, and obtaining a captured image using a camera (first step); converting the image obtained in the first step to a gray scale image, and calculating a ratio of white area to the converted gray scale image (second step); and outputting a defrost start command if the ratio of white area calculated from the second step is higher than a predetermined threshold value (third step).

The defrosting system and method of refrigerator according to the present invention has an advantageous effect in that a start time and a finish time of defrosting operation can be precisely determined by a camera to prevent unnecessary defrosting operation in advance, and to prevent the refrigerating and freezing performances from being degraded that is caused by elapsed defrosting time resultant from failure to cope with fluctuating environments according to situations inside the refrigerator.

The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a pictorial view illustrating frost formed on an evaporator of a refrigerator;

FIG. 2 is a schematic view illustrating a refrigerator applied with a defrosting system according to an exemplary embodiment of the present invention;

FIG. 3 is a block diagram illustrating an operation of defrosting system of evaporator in a refrigerator according to an exemplary embodiment of the present invention;

FIG. 4 is flowchart illustrating a defrosting method of an evaporator in a refrigerator according to an exemplary embodiment of the present invention;

FIG. 5 shows schematic views illustrating processes for calculating a ratio of white area in a controller according to an exemplary embodiment of the present invention; and

FIG. 6 shows schematic views illustrating a ratio of white area based on frost level.

The exemplary embodiments described here in detail for illustrative purposes are subject to many variations in structure and design. It should be emphasized, however, that the present invention is not limited to a particular disclosure, as shown and described. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as "/".

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first region/layer could be termed a second region/layer, and, similarly, a second region/layer could be termed a first region/layer without departing from the teachings of the disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the general inventive concept. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," or "includes" and/or "including" when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

As to be noted, the following method descriptions and the process flow diagrams are provided merely as illustrative examples and are not intended to require or imply that the processes of the various aspects must be performed in the order presented. As will be appreciated by one of skill in the art the order of blocks and processes in the foregoing aspects may be performed in any order. Words such as "thereafter," "then," "next," etc. are not intended to limit the order of the processes; these words are simply used to guide the reader through the description of the methods. Further, any reference to claim elements in the singular, for example, using the articles "a," "an" or "the" is not to be construed as limiting the element to the singular.

The disclosed embodiments and advantages thereof are best understood by referring to FIGS. 1-6 of the drawings, like numerals being used for like and corresponding parts of the various drawings. Other features and advantages of the disclosed embodiments will be or will become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional features and advantages be included within the scope of the disclosed embodiments, and protected by the accompanying drawings. Further, the illustrated figures are only exemplary and not intended to assert or imply any limitation with regard to the environment, architecture, or process in which different embodiments may be implemented. Accordingly, the described aspect is intended to embrace all such alterations, modifications, and variations that fall within the scope and novel idea of the present invention.

Furthermore, "exemplary" is merely meant to mean an example, rather than the best. It is also to be appreciated that features, layers and/or elements depicted herein are illustrated with particular dimensions and/or orientations relative to one another for purposes of simplicity and ease of understanding, and that the actual dimensions and/or orientations may differ substantially from that illustrated. That is, in the drawings, the size and relative sizes of layers, regions and/or other elements may be exaggerated or reduced for clarity. Like numbers refer to like elements throughout and explanations that duplicate one another will be omitted.

Now, the defrosting system and method of refrigerator according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a refrigerator is such that outside air is introduced thereinto by opening/closing of a door, and the introduced air circulates along an air circulation path inside the refrigerator. At this time, moisture included in the circulating air contacts an evaporator and forms frost by being solidified on a surface of the evaporator.

FIG. 2 is a schematic view illustrating a refrigerator applied with a defrosting system according to an exemplary embodiment of the present invention, where the system includes a camera (140) for monitoring frost level, and a light source (150) for providing a photographing light to the camera (140). Reference numeral 110 is a heat exchange chamber, and 120 is an evaporator and 130 is a defroster.

The heat exchange chamber (110) is formed at a rear side of a refrigerator body (100) and connected to the evaporator (120). The air infused into the refrigerator is blown to the evaporator (120) where the air is heat-exchanged and discharged into the refrigerator again. The heat exchange chamber (110) is formed therein with the evaporator (120). The evaporator (120) quickly reduces the ambient temperature by the heat exchange through movement of refrigerant.

The defroster (130) is disposed at a bottom side of the evaporator (120) to remove the frost formed at the evaporator (120). The defroster (130) may be formed by being repeatedly bent in a 'U' shape at both ends for enhancing the heating efficiency. The defroster (130) determines an operation start time based on image captured by the camera (140) to emit heat and remove the frost. An operation finish time may be determined by the captured image.

The heat generated by operation of the defroster (130) is transmitted upwards by convection as shown in FIG. 2. The defroster (130) may be embodied by a heater generating heat or a steam generator in which steam is generated by emission of heat and ejected to the evaporator (120) to remove the frost.

The frost monitoring camera (140) is formed at an upper surface of the refrigerator body to capture a frost level, and a control part (200, hereinafter referred to as controller) determines a defrosting start time of frost formed at the evaporator using the captured image. The controller (200) may determine the defrost finish time as well. The frost monitoring camera (140) may be formed at a place of the refrigerator body adequate for monitoring the frost status.

The controller (200) may control the defroster (130) by outputting a defrost start time or a defrost finish time to the defroster (130) using the captured image. The frost monitoring camera (140) performs a capturing operation at a predetermined time (i.e., equal-distance period) different from the turned-on status of electric power in the refrigerator. The operation period of the defrost monitoring camera (140) may be set up by a user.

A defrosting system and a defrosting method using the system according to the exemplary embodiment of the present invention will be described with reference to FIGS. 3 and 4.

First, the light source (150) for providing illumination light to the frost monitoring camera (140) for capturing images is operated (S11). The light source (150) may be a low power-consuming LED (Light Emitting Diode) for photographing of the camera (140), for example. The illumination may be so controlled as to be turned off the moment the capturing operation of the camera (140) is finished.

Furthermore, if the camera (140) is an infrared camera, the light source (150) may be an infrared light source emitting infrared. The camera (140) and the light source (150) may be controlled in operation thereof by a control signal from the controller (200, described later). The controller (200) may output an operation control signal to the camera (140) and the light source (150) at a predetermined interval using an inner timer (not shown).

The frost status of the evaporator (120) is captured by the frost monitoring camera (140) formed at the refrigerator body after the light source (150) is activated, and then the light source (150) is turned off (S12). The camera (140) may capture a stationary image at a predetermined time interval. Furthermore, in case of capturing moving pictures, the camera (140) can photograph the image and a ratio of white area (hereinafter referred to as white area ratio) to image can be calculated per frame of moving picture.

In a case the power of the camera (140) is turned off before photographing, the power is activated, and a self heat emitting time may be provided for a predetermined time to allow the camera (140) to go through a process of removing moisture and/or frost formed inside the camera (140).

The controller (200) receives the image obtained by the camera (140) to calculate a frost level value and to determine whether to operate the defroster (130) based on the calculated frost level value. As shown in FIG.5, the controller (200) converts an extreme left captured image of the camera (140) to a gray scale image located in the middle on the figure.

A conventional gray scale image is expressed within 0~255 gray levels based on contrast degree. The controller (200) checks gray level of each pixel of relevant image from the image converted to the gray scale, and determines as a white pixel if the gray level is greater than a set-up value, and determines as a black pixel if the gray level is less than the set-up value.

For example, if the gray level is set up at 80 in 0~255 gray levels, the gray level value of each pixel is compared with the set-up value of 80, and if the gray level value is greater than 80, the controller determines as white pixel and if less than 80, the controller determines as a black pixel.

Therefore, the image having gone through the abovementioned process is expressed in a binary image that is registered only as black or white, as shown in the extreme right side on FIG.5. The binary image is an image that can be easily recognized by the controller (200), white as "1", and black as "0".

Thereafter, ratio of number of pixels for white pixel against the entire number of pixels in the image can be easily calculated, and the ratio is taken by the controller (200) as the frost level value. As shown in FIG. 6, it can be noted that the bigger the frost formation level is the white area of each image is enlarged from the left side to the right side.

The controller (200) determines whether to activate the defroster (130) based on the thus-calculated frost level value (S14), and if the frost level value is greater than a set-up threshold value, the controller (200) outputs an operation start signal to the defroster (130) to allow the defroster (130) to be activated, and if the frost level value is smaller than the set-up threshold value, the controller (200) receives a captured image of next period to repeat the abovementioned operations.

If the frost level value is greater than the set-up threshold value, the defroster (130) performs the defrosting operation, and performs a process of comparing the frost level value with the set-up threshold value by performing the operations from S11 through S13 (S19). These processes are intended to grasp the frost removal level based on the operation of the defroster (130), and to deactivate the defroster (130) if the frost removal level reaches a satisfactory degree.

As apparent from the foregoing, the frost monitoring camera (130) is employed to accurately determine a defrost operation start time and a defrost operation finish time, whereby the generated frost can be effectively removed.

Thus, the term of part used in the exemplary embodiment of the present invention may be implemented in the form of a computer program product or similar object of manufacture comprising processor implementable instructions stored on a data carrier such as a floppy disk, optical disk, hard disk, PROM, RAM, flash memory or any combination of these or other storage media, or transmitted via data signals on a network such as an Ethernet, a wireless network, the Internet, or any combination of these of other networks, or realized in hardware as an ASIC (application specific integrated circuit) or an FPGA (field programmable gate array) or other configurable circuit suitable to use in adapting the conventional equivalent device.

It should be understood that the software components described may be configured separately or as a single software component, or as a different arrangement of components or modules configured to carry out the steps described. Those of skill will recognize that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware computer software or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CDROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.

That is, the above-described methods according to the present invention can be realized in hardware or as software or computer code that can be stored in a machine readable recording medium such as a CD ROM, a RAM, thumbnail drive, a floppy disk, a flash storage, a hard disk, or a magneto-optical disk or downloaded over a network and stored as a non-transitory data on one of the aforementioned mediums, so that the methods described herein can be executed by such software using a general purpose computer, or a special processor or in programmable or dedicated hardware, such as an ASIC or FPGA. As would be understood in the art, the computer, the processor or the programmable hardware include memory components, e.g., RAM, ROM, Flash, etc. that may store or receive software or computer code that when accessed and executed by the computer, processor or hardware implement the processing methods described herein. In addition, it would be recognized that when a general purpose computer accesses code for implementing the processing shown herein, the execution of the code transforms the general purpose computer into a special purpose computer for executing the processing shown herein.

The various illustrative logical blocks, modules, circuits, and algorithm processes described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and algorithms have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

Again, in one or more exemplary aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. The processes of a method or algorithm disclosed herein may be embodied in a processor-executable software module executed which may reside on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to carry or store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and/or instructions stored on a machine readable medium and/or computer-readable medium, which may be incorporated into a computer program product.

The previous description of the present invention is provided to enable any person skilled in the art to make or use the invention. Various modifications to the invention will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the invention. Thus, the invention is not intended to be limited to the examples and a design described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

A defrosting system of an evaporator in a refrigerator, comprising: a camera capturing a status of frost formed at the evaporator; a controller calculating a frost level value by receiving a captured image from the camera and outputting a defrosting operation control signal responsive to the calculated frost level value, wherein the camera captures the status of frost at a predetermined interval, and is turned on for pre-heat operation prior to start of image-capturing.
The system of claim 1, comprising the controller converts the inputted captured image to a gray scale, calculates a ratio of a white area to an entire area of the converted gray scale image and determines the ratio as the frost level value.
The system of claim 2, comprising the ratio of white area to an entire area of the converted gray scale image is a ratio of number of white pixels to number of entire pixels of gray scale image.
The system of claim 3, comprising gray scale level of each pixel in the converted gray scale image is checked and if the gray scale level is higher than a predetermined value, a pixel corresponding thereto is determined as the white pixel.
The system of claim 1, further comprising a light source for providing an illumination to the camera, wherein the light source has an ON/OFF period which is same as a capturing period of the camera.
The system of claim 1, comprising the controller outputs a defrosting start control signal if the frost level value is higher than the predetermined value, and outputs a defrosting stop control signal, if the frost level value calculated by input of a captured image of next period is less than the predetermined value.
The system of claim 1, comprising the camera is turned on prior to capturing time to thereby have a pre-heat time for pre-heating.
A defrosting method of an evaporator in a refrigerator, comprising: obtaining a captured image of an evaporator (first step); converting the image obtained in the first step to a gray scale image, and calculating a ratio of white area to the converted gray scale image (second step); and outputting a defrost start command if the ratio of white area calculated from the second step is higher than a predetermined threshold value (third step).
The defrosting method of claim 8, further comprising outputting a defrost stop command after the third step if the ratio of white area calculated by repeating the first and second steps is less than a predetermined threshold value (fourth step).
The defrosting method of claim 9, comprising the ratio of white area in the second step is calculated by a ratio of the number of white pixels to the number of entire pixels, where the white pixels are determined by gray level of each pixel of the gray scale image.
A defrosting system of an evaporator in a refrigerator, comprising: a light source irradiating light to an evaporator of a refrigerator; a camera continuously capturing status of frost formed on the evaporator reflected by the light of the light source at a predetermined interval; and a controller calculating a frost level value by receiving a captured image from the camera and outputting a defrosting operation control signal responsive to the calculated frost level value.
The system of claim 11, comprising the controller converts the inputted captured image to a gray scale, calculates a ratio of a white area to an entire area of the converted gray scale image and determines the ratio as the frost level value.
The system of claim 12, comprising the ratio of white area to an entire area of the converted gray scale image is a ratio of number of white pixels to number of entire pixels of gray scale image.
The system of claim 13, comprising gray scale level of each pixel in the converted gray scale image is checked and if the gray scale level is higher than a predetermined value, a pixel corresponding thereto is determined as the white pixel.
The system of claim 11, comprising the light source has an ON/OFF period which is same as a capturing period of the camera.
The system of claim 11, comprising the controller outputs a defrosting start control signal if the frost level value is higher than the predetermined value, and outputs a defrosting stop control signal, if the frost level value calculated by input of a captured image of next period is less than the predetermined value.
The system of claim 11, comprising the camera is turned on prior to capturing time to thereby have a pre-heat time for pre-heating.
A defrosting method of an evaporator in a refrigerator, comprising: applying an electric power to a light source to illuminate the evaporator, and obtaining a captured image using a camera (first step); converting the image obtained in the first step to a gray scale image, and calculating a ratio of white area to the converted gray scale image (second step); and outputting a defrost start command if the ratio of white area calculated from the second step is higher than a predetermined threshold value (third step).
The defrosting method of claim 18, further comprising outputting a defrost stop command after the third step if the ratio of white area calculated by repeating the first and second steps is less than a predetermined threshold value (fourth step).
The defrosting method of claim 19, comprising the ratio of white area in the second step is calculated by a ratio of the number of white pixels to the number of entire pixels, where the white pixels are determined by gray level of each pixel of the gray scale image.