BACKGROUND

[0001] Print devices are commonly used in home and office environments for obtaining printed copies of digital documents. The print devices are provided with trays for handling a print medium during execution of a print job. For instance, a print device is provided with an input tray for holding and receiving print media that maybe of different sizes and types, thus allowing the user to print documents on different print medium. Further, the print device may include an output print tray to retain a printed medium.

BRIEF DESCRIPTION OF DRAWINGS

[0002] The detailed description is described with reference to the accompanying figures. It should be noted that the description and figures are merely example of the present subject matter and are not meant to represent the subject matter itself.

[0003] Figure 1 illustrates a print device having a light pipe with a surface of an input tray of the print device removed, according to an example of the present subject matter.

[0004] Figure 2 illustrates an imaging device having a light pipe, according to an example of the present subject matter.

[0005] Figure 3 illustrates a print device having a light pipe with a surface of an input tray of the print device removed, according to an example of the present subject matter.

[0006] Figure 4 illustrates a print device having a light pipe with a surface of an input tray of the print device removed, according to an example of the present subject matter.

[0007] Figure 5 illustrates a top view' and a side view of a light pipe, according to an example of the present sub _j ect matter. [0008] Figure 6 illustrates a top view and a side view of a light pipe, according to an example of the present subject matter.

[0009] Figure 7 illustrates a method of print medium detection m an input tray of a print device, according to an example of the present subject matter.

DETAILED DESCRIPTION

[0010] A pnnt device is provided with an input tray for holding print media that maybe of different sizes and types, thus allowing the user to print documents on different print media. To allow the print device to customize printing of a document in accordance to the print medium size and type, the print device may employ various mechanisms to detect the presence and size of the print medium in the input tray. One such mechanism uses multiple reflective optical detectors and printed circuit boards (PCBs) located in a print medium path within the print device. Using such reflective optical detectors increases the manufacturing cost associated with the print device owing to the high cost of the reflective optical detectors, PCBs, and the associated assembly. Another mechanism includes use of an assembly of reduced number of reflective optical detectors and multiple actuators, such as flags for detecting paper width. However, such assemblies are costly and complex to implement as the flags have to be precisely fitted with the correct orientation. Further, such flag assemblies may utilize a large space in the print devices for installation and may thus not be useful for small sized print devices.

[0011] Alternatively, a user may manually provide an input indicating the print medium size. However, manually providing the print medium size may be cumbersome for the user and may also be inaccurate as the user may not always be aware of the exact print medium size. Further, a control panel, having a display and input butons or a touch screen, may be provided on the printer to enable the user to enter the print medium size.

[0012] The subject matter relates to print medium detection, for example, detection of size and presence of a print medium on print devices. Example implementations for a light pipe for print medium detection in print devices are described. As per an example of the present subject matter, a light pipe may be disposed in the input tray to detect at least one of print medium size and presence of print medium on the input tray. In one example, a single set of a light emiting source and a phototransistor may be used to dissipate light through the light pipe and detect the intensity of light reflected back to detect the print medium presence and print medium size. The light pipe includes a plurality of branches to dissipate light through a corresponding slot in the input tray and receive light reflected back upon placement of print medium over the corresponding slot. The intensity of the light reflected back may vary based on the number of slots covered by the print medium and is thus indicative of the print medium size. The print device and the light pipe of the present subject matter thus facilitate print medium detection, for example, detection of print medium size and presence of a print medium with minimal hardware, thereby reducin costs of the print device.

[0013] In one example, the input tray of the print device includes a surface having a plurality of slots at different positions indicative of a different print medium size. For instance, a first slot may he provided at a position that can be covered by a print medium having a first size. Further, a first branch of the light pipe may be positioned within the first slot to dissipate light through the first slot and receive light reflected back upon placement of the print medium having the first size. A second slot may be provided at a position that may be covered by a print medium having size greater than or equal to second size. A second branch of the light pipe may be positioned within the second slot to dissipate light through the second slot and receive light reflected back upon placement of the print medium having the size greater than or equal to second size. A third slot may be provided at a position that may be covered by print media of all sizes. A third branch of the light pipe may be positioned within the third slot to dissipate light through the third slot and receive light reflected back upon placement of any print medium. Thus, detection of the light reflected from branch associ ated with the third slot may be used as a minimum light intensity to indicate the presence of print medium on the input tray. [0014] Further, as the print medium having the first size may cover all the three slots, the light intensity detected by the phototransistor may be maximum when a large print medium is placed m the input tray. The light intensity may reduce for a print medium having the second size as the print medium may cover two slots. Further, the light intensity ⁷ may be least when the print medium of third size is placed in the input tray. Tims, an output signal generated by the phototransistor may ^¬ be of varying voltage level in accordance to the detected intensity of light, thereby- indicating the print medium size. Therefore, the same phototransistor may he used to differentiate between different print medium sizes.

[0015] The present subject matter thus provides a cost effective and efficient mechanism for print medium detection including print medium size and presence detection. Using the light pipe with a plurality of branches to dissipate light and receive light reflected from print medium allows the use of a single set of light emitting source and phototransistor as the light reflected from all branches travels back in the same direction in the light pipe. Using a single set of light emitting source and phototransistor to detect all media sizes substantially reduces costs as compared to print devices using separate sets for each media size. Further, using a light pipe with branches further reduces costs in comparison to use of a flag assembly. Further, each of the plurality ⁷ of branches extends radially outward from the light pipe into the plurality of slots. Havin radial branches helps in ensuring that light reflected back into the branches does not dissipate in all directions in the light pipe and is optimally directed towards the phototransistor. Additionally, each branch may have a radius greater than or equal to the cross section of the light pipe to ensure total internal reflection within the light pipe. Making the radius of each branch greater than or equal to the cross section of the light pipe ensures that total internal reflection is affected within the light pipe to reduce leakage of light through the light pipe.

[0016] The present subject matter is further described with reference to

Figures 1 to 7. It should be noted that the description and figures merely illustrate principles of the present subject matter. V arious arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof

[0017] Figure 1 illustrates a print device 100 having a light pipe with a surface of an input tray of the print device removed, according to an example implementation of the present subject matter. Examples of the print device 100 include, but are not limited to, a printer, a multifunction printer, a home printer, and an office printer. In one example, the print device 100 includes an input tray 102 to receive a print medium of various sizes and types and a light pipe 104 for detection of a print medium on the input tray 102. Examples of the print medium incl ude, but are not limited to, paper, photopolymers, thermopolymers, plastics, composite, metal, w'ood, etc., and may include any suitable feature including the size, shape, material, thickness, or any other quality suitable for placement in the print device 100. The input tray 102 may include a surface 106 to receive the print medium. The input tray 102 may further include a plurality of slots 108-1, 108-2, and 108-n provided on the surface 106. The plurality of slots 108-1 , 108-2, and 108-n is hereinafter collectively referred to as slots 108 and individually referred to as slot 108. In one example, each slot 108 is provided at a different position and together the slots 108 indicate different print medium size. The print device 100 has been shown with th e surface 106 of the input tray 102 removed and illustrated separately to allow- the light pipe 104 to be visible inside the input tray 102.

[0018] The light pipe 104 may be defined as a guide or a physical structure to transport light from a source of light, provided at one end of the light pipe, to exit points or slots. The light pipe 104 allows the light generated by the source of light to travel across the light pipe and dissipate through the various exit points. In one example, the light pipe may have an internal reflective lining m an inner surface to affect total internal reflection to prevent leakage of light.

[0019] The light pipe 104 may be used for detection of print medium. In one example, the print medium detection includes detection of print medium presence and print medium size of a print medium, such as paper in the input tray 102. In accordance to an example implementation of the present subject matter, the light pipe 104 is disposed m the input tray and may include a plurality of branches 110-1, 110-2, and 110-n to guide light in the light pipe 104. The plurality of branches 110-1, 110-2, and 110-n is hereinafter collectively referred to as branches 110 and individually referred to as branch 110. Further, while the branches 110 are radially extending from the light pipe, as illustrated in Figures 5 and 6, the branches 110 appear to be straight and having the same profile as the light pipe 104 in the top view image, as illustrated in the Figure 1.

[0020] In one example implementation, the branches 110 are positioned within the plurality of slots 108, such that each branch 1 10 is positioned inside a corresponding slot 108. In said example, each branch 110 is to dissipate light through the corresponding slot 108 and to receive light reflected back upon placement of the print medium over the corresponding slot 108. The light pipe 104 may further include a sensor assembly 112 positioned at a first end 114 of the light pipe 104 to generate an output signal in accordance to the intensity of light reflected back in the light pipe 104. In one example, the output signal may indicate detection of the print medium.

[0021 ] Figure 2 illustrates an imaging device 202 having the light pipe 104, according to an example implementation of the present subject matter. Examples of the imaging device include, but are not limited to, printers, multi-functional printers, scanners, etc. In one example, the imaging device 202 includes the input tray 102 to receive print medium and the light pipe 104 disposed in die input tray 102 to detect the print medium. In one example, the input tray 102 may include the plurality of slots 108. Further, the light pipe 104 includes the plurality of branches 110 with each branch 110 positioned within a corresponding slot 108 from among the plurality of slots 108. Further, each branch 110 is to dissipate light through the corresponding slot 108 such that when the print medium covers a slot 108 on the input tray, the light is reflected back into the corresponding branch 110. [0022] In one example implementation, the branches 110 includes a first branch 1 10-1, a second branch 1 10-2, and a third branch 1 10-h The first branch 1 10-1 is positioned closest to the first end 114 of the light pipe 104. The second branch 110-2 is positioned in between the first end 114 and a second end 204 of the light pipe 104. The third branch 1 10-n is positioned at the second end 204 of the light pipe 104. The light pipe 104 further includes the sensor assembly 1 12 positioned at the first end 1 14 of the light pipe 104 to generate the output signal in accordance to the intensity of light reflected back in the light pipe 104 to indicate detection of the print medium.

[0023] The branch 1 10 may thus receive the light reflected back from the print medium and transmit the light to the sensor assembly 112 positioned inside the light pipe 104. The sensor assembly 112 may then generate the output signal accordance to the intensity of light reflected back in the light pipe 104 In one example, the output signal may indicate presence of the print medium and the print medium size. Further, while the branches 110 are radially extending from the light pipe, as illustrated in Figures 5 and 6, the branches 110 appear to be straight and having the same profile as the light pipe 104 in the top view image, as illustrated in the Figure 2.

[0024] Figure 3 illustrates the print device 100 having the light pipe 104 with the surface 106 of the input tray 102 of the print device 100 removed, according to an example implementation of the present subject matter. In one example, the print device 100 includes the input tray 102 to receive the print medium. The input tray 102 includes the plurality of slots 108 pro vided at different positions indicative of a different print medium size. The print device 100 further includes the light pipe 104 disposed in the input tray 102 to detect print medium. The light pipe 104 includes the plurality of branches 110 such that each branch is positioned within a corresponding slot 108 from among the plurality of slots 108.

[0025] In one example implantation, the plurality of branches 110 include the first branch 110-1 positioned closest to the first end 114 to dissipate light through the corresponding slot 108-1 and to receive light reflected back from the print medium upon placement of the print medium over the corresponding slot 108- 1. The branches 110 further include the second branch 1 10-2 positioned in between the first end 114 and the second end 204 to dissipate light through the corresponding slot 108-2 and to receive light reflected back from the print medium upon placement of the print medium over the corresponding slot 108-2. The branches 110 further include the third branch 110-n positioned at the second end 204 to dissipate light through the corresponding slot 108-n and to receive light reflected back from the print medium upon placement of the print medium over the corresponding slot 108- n.

[0026] The light pipe 104 may further include the sensor assembly 112 positioned at the first end 114 of the light pipe 104 to detect intensity of light reflected from a branch 110, from the plurality of branches 110. In one example, the intensity of light is related to the number of slots 108 covered by the print medium and may vary based on the print medium size. The sensor assembly 112 may subsequently generate the output signal in accordance to the detected intensity ⁷ of light to indicate detection of the print medium. Further, while the branches 110 are radially extending from the light pipe, as illustrated in Figures 5 and 6, the branches 110 appear to be straight and having the same profile as the light pipe 104 in the top view image, as illustrated in the Figure 3.

[0027] Figure 4 illustrates the print device 100 having the light pipe 104 with the surface 106 of the input tray 102 of the print device 100 removed, according to another example of the present subject matter. As previously described, the print device 100 may be used to print documents on a print medium, such as paper. In accordance to an example implementation, the print device 100 may include processor(s) 402 and modules 404 to control the functionalities and different components or units of the print device 100. The processor(s) 402 may include microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any other devices that manipulate signals and data based on computer-readable instructions. Further, functions of the various elements shown in the figures, including any functional blocks labeled as“processor(s)”, may be provided through the use of dedicated hardware as well as hardware capable of executing computer- readable instructions.

[0028] The modules 404, amongst other things, includes routines, programs, objects, components, and data structures, winch perform particular tasks or implement particular abstract data types. The modules 404 may also be implemented as signal processor(s), state machine(s), logic circuitries, and/or any other device or component that manipulate signals based on operational instructions. Further, the modules 404 can be implemented by hardware, by computer-readable instructions executed by a processing unit, or by a combination thereof.

[0029] The modules 404 include a print medium management unit 406, a print unit 408, and other modules 410. In one example, the print medium management unit 406 and the print unit 408 may control the print customization and print operations for the print device 100 based at least on the output signal generated by the sensor assembly 112.

[0030] In accordance to an example implementation of the present subject matter, the print device 100 includes a plurality of print trays to handle the print medium during a print job. For instance, the print device 100 includes the input tray 102 to handle the print medium to be used for print j ob and an output print tray 412 to handle a printed medium for being collected by the user after the print job gets over. In one example implementation, the print device 100 may include multiple input trays to handle the print medium. In said example, each of the multiple input trays may include the light pipe 104 to detect the print medium.

[0031] In one example, the input tray 102 includes the top surface 106 to receive the print medium of varying sizes. In one implementation, the print medium size may be one of a first size, a second size, and a third size. The first size may be a large size, for example, a letter page of dimension 216 mm x 279 mm and an .44 page of dimensions 210 mm x 297 mm. The second size may be a medium size, for example, a B6 page of dimension 125 mm x 176 mm and 5x7 inch. The third size may be a small size, for example, an A6 page of dimension 105 mm x 148 mm and 4x6 inch. Further, in case of the print medium being a powder for 3D printer, the print medium size may correspond to size of a powder sheet.

[0032] The input tray 102 may further include the plurality of slots 108 provided on the surface. As previously described, the slots 108 may be provided at different positions indicative of the different print medium. In one example, a first slot 108-1 may be provided at a position that can be covered by a print medium having the first size. A second slot 108-2 may be provided at a position that may be covered by a print medium having a print medium size greater than or equal to the second size. A third slot 108-n may be provided at a position that may be covered by print medium of all print medium sizes. In another example, the first slot 108-1 may be provided at a position that can be covered by print medium of all print medium sizes. A second slot 108-2 may be provided at a position that may be covered by a print medium having a print medium size greater than or equal to the second size. A third slot 108-n may be provided at a position that may be covered by a print medium having the first size.

[0033] The print device 100 may further include the light pipe 104 disposed in the input tray 102 for prime medium detection. In one example, the light pipe 104 may be provided for print medium size detection. In another example, the light pipe 104 may be provided to detect presence of print medium on the input tray 102. In another example, the light pipe 104 may be provided for print medium size detection and to detect presence of print medium on the input tray 102.

[0034] As previously described, the light pipe 104 is to be placed inside the input tray 102 of the print device such that each of the plurality of branches 1 10 is positioned within a corresponding one of the plurality of slots 108. For instance, a first branch 110-1 of the light pipe 104 may be positioned within the first slot 108- 1. A second branch 110-2 of the light pipe 104 may be positioned within the second slot 108-2. A third branch 110-h of the light pipe 104 may be positioned within the third slot 108-n. In one example, each of the plurality of branches 110 is to dissipate light through the corresponding slot 108 and to receive light reflected back upon placement of the print medium over the corresponding slot on the input tray 102

[0035] Although, the current description has been described with regards to three slots and three branches, the input tray 102 may have varying number of slots based on the varying print medium sizes that the print device 100 may print on. Further, the number of slots 108 may also be varied to improve the accuracy of print medium size detection. The number of branches 110 may thus also van' in accordance to the number of slots 108.

[0036] For instance, the first branch 110-1 of the light pipe 104 may be positioned within the first slot 108-1 to dissipate light through the first slot 108-1 and receive light reflected back upon placement of the print medium having the first size. The second branch 110-2 of the light pipe 104 may be positioned within the second slot 108-2 to dissipate light through the second slot 108-2 and receive light reflected back upon placement of the print medium having print medium size greater than or equal to the second size. The third branch 110-n of the light pipe 104 may be positioned within the third slot 108-n to dissipate light through the third slot 108-n and receive light reflected back upon placement of any print medium. Thus, intensity of the light reflected from branch 1 10-n associated with the third slot 108-n may be used as a minimum light intensity' to indicate the presence of print medium on the input tray.

[0037] Further, while the branches 110 appear to be straight and having the same profile as the light pipe 104 in the top view' image, as illustrated in the Figure 4, the branches 110 are radially extending from the light pipe, as illustrated in Figures 5 and 6.

[0038] In one example, each of the plurality' of branches 110 extends radially outward from the light pipe 104 into the slot 108, as illustrated in Figures 5 and 6. Thus, the light reflected back into the branch 110 may travel m one direction and disperse in the entire light pipe 104. In one example, the branches 1 10 extend radially such that the reflected light travels back in the direction of the sensor assembly 112 placed inside the light pipe 104. F urther, each branch 110 has a radius greater than or equal to the cross section of the light pipe 104. In one example implementation, the third branch 1 10-h has a radius greater than the radius of the first branch 110-1 and the second branch 1 10-2. In another example implementation, all the branches 110 may have the same radius.

[0039] The light pipe 104 may further include the sensor assembly 112 to transmit light inside the light pipe 104 and detect the intensity of the light reflected back in the light pipe 104. In one example, the sensor assembly 112 is positioned at a first end of the light pipe 104, in the vicinity of the first branch 110. In said example, the first branch 1 10-1 is die shortest branch and the third branch 110-n is the longest branch, positioned at a second end of the light pipe 104. As aforementioned, the sensor assembly 112 is positioned such that the light transmitted by the sensor assembly 112 is dissipated in the direction of the branches 110. Further, the light reflected back from the print medium travels in the direction of the sensor assembly 112.

[0040] In one example implementation, the sensor assembly 112 includes a light emitting source 414 and a phototransistor 416 positioned proximate to the light emitting source 414. The light emitting source 414 is placed at the first end 114 of the light pipe 104 to emit the light of a certain intensity' within the light pipe 104 m the direction of the branches. In one example, the light emiting source 414 may be a light emitting diode. In another example, the light emiting source 414 may be a laser diode. Further, the photo transistor 416 is positioned alongside the light emiting source 414 at the first end 114 of the light pipe. The phototransistor 416 is provided to detect the intensity of light reflected back in the light pipe 104 from at least one branch 1 10 and generate the output signal in accordance to the detect intensity' of light. The phototransistor 416 is a light sensitive transistor that may be used to detect presence of light and also the intensity' of the detected may be a light emitting diode. In one example, the phototransistor 416 may convert the detected light into an electrical current.

[0041] In one example, the intensity of light reflected is related to the number of slots 108 covered by the print medium and varies based on the print medium size. For instance, the light intensity may be minimum for a print medium of the third size, i.e., small size as the print medium in such a case may cover a single slot, i.e., the third slot 108-n. ^' The light intensity may be higher for a print medium of the second size, i.e., medium size as the print medium in such a case may cover two slots, i.e., the second slot 108-2 and the third slot 108-n. The light intensity may he maximum for a print medium of the first size, i.e., large size as the print medium in such a case may cover all slots, i.e., the first slot 108-1, the second slot 108-2, and the third slot 108-n. Further, the detection of light intensity greater than or equal to the minimum light intensity may indicate presence of the print medium over the input tray 102.

[0042] In one example, for a light emitting source 414, such as an infrared

LED with operating current of 40mA, radiant intensity of 12 milliwatt per steradian (mW/sr), and wavelength 940 mm, the minimum light intensity corresponding to the third size may be around 0.4 mW/sr. The medium light intensity corresponding the second size may be around 0.55 mW/sr. The maximum light intensity' corresponding to the first size may be around 0.66 mW/sr.

[0043] The photo transistor 416 may thus generate the output signal indica ting presence of the print medium and the print medium size in accordance to the detected light intensity . In one example, the output signal may be an analog signal having a voltage level in accordance to the detected light intensity. The output signal in such a case may be converted to a digital signal by an analog to digital convertor coupled to the sensor assembly 112. In one example, the analog to digital convertor may be provided within the sensor assembly 112 to provide a digital output.

[0044] The sensor assembly 1 12 may subsequently provide the output signal to the print medium management unit 406 to determine the print medium size based on the output signal and a size mapping table. In one example, the size mapping table may indicate a predefined range of voltage levels for each print medium size such that voltage level of the output signal may fall wrthin any of the predefined ranges. In another example, the size mapping table may be a set of predefined ratios of voltage levels. In another example, the size mapping table may be calibrated individually, during manufacturing, for different media sizes to more precisely account for assembly variations.

[0045] The print medium management unit 406 may thus identify the corresponding print medium size from the size mapping in accordance to the voltage level of the output signal. The print medium management unit 406 may further display the determined print medium size on a display of the print device 100. In one example, the print medium management unit 406 may also provide the determined print medium size to the print unit 408 for customizing print data based on the print medium size. The print unit 408 may subsequently customize the print data and have the print data printed to obtain the printed media.

[0046] In operation, as the print device 100 is powered ON, the light emitting source 414 may start emitting light of the certain intensity within the light pipe 104 in the direction of the plurality of branches 110. In one example, the light emitting source 414 may continuously emit the light. In another example, the light emitting source 414 may emit the light at regular intervals. In another example, the light emitting source 414 may be switched ON or OFF for predetermined periods. For example, the light emitting source 414 may be kept in the OFF state when the print device 100 is m a sleep mode and may be switched ON when the print device 100 is brought to an active state of operation.

[0047] When a user of the print device 100 places a print medium, say of second size, the light from the corresponding slots 108 is reflected back in the branches. For instance, in the above example, the print medium of the second size may cover the second slot 108-2 and the third slot 108-n and thus the light may get reflected back in the second branch 110-2 and the third branch 110-h.

[0048] The reflected light may then travel back through the branches 110 and into the light pipe 104 in the direction of the sensor assembly 112 owing to the radial shape of the branches 110. The phototransistor 416 may then receive the refl ected light and detect the intensity of the reflected light. The phototransistor 416 may further generate the output signal in accordance to the detected intensify of light indicating presence of the print medium and the print medium size. The output signal is further transmitted to the print medium management unit 406 to determine the print medium size based on the output signal and a size mapping table and display the print medium size on a display of the print device 100.

[0049] Figure 5 illustrates a top view 502 and a side view 504 of the light pipe 104, according to another example of the present subject matter. In one example, the top view 502 depicts a view of the light pipe 104 in a direction perpendicular to the surface of the paper. Further, the side view 504 depicts a view of the light pipe 104 m a direction along die surface of the paper. The light pipe 104 includes the plurality of bra ches 1 10 and the sensor assembly 1 12, In said example, the light pipe 104 includes three branches 1 10, i.e., the first branch 110-1, the second branch 110-2, and the third branch 110-n. Each of the branch 110 in the top view 502 has been mapped to the corresponding branch 1 10 in the side view 504 to indicate how each branch 110 may look in the two views.

[0050] As illustrated in the side view 504, each of the branches 110 extends radially outward from the light pipe 104. As previously described, each of the plurality of branches 1 10 extends radially outward into the corresponding slot 108.

[0051 ] Further, as illustrated, the third branch 110-n in the present example is the longest branch positioned farthest from the sensor assembly 112, at the second end 204, and the first branch 110-1 is the shortest branch positioned closest to the sensor assembly 112, close to the first end 114 Further, the first branch 1 10-1 and the second branch 1 10-2 are positioned on opposite sides of the light pipe 104, as illustrated, with the third branch 110-n extending in between the first branch 110-1 and the second branch 1 10-2.

[0052] As previously described, the light pipe 104 is to be placed inside the input tray 102 of the print device such that the first branch 110-1 may be positioned within the first slot 108-1 to dissipate light through the first slot 108-1 and receive light reflected back upon placement of the print medium having the first size. The second branch 110-2 may be positioned within the second slot 108-2 to dissipate light through the second slot 108-2 and receive light reflected back upon placement of the print medium having one of a second size and the first size. The third branch 1 10-n may be positioned within the third slot 108-n to dissipate light through the third slot 108-n and receive light reflected back upon placement of any print medium. Further, the sensor assembly 112 includes the light emitting source 414 to emit light in the light pipe 104 and the photo transistor 416 positioned proximate to the light emitting source 414 to determine intensity of the light reflected back in the light pipe 104.

[0053] Figure 6 illustrates a top view 602 and a side view 604 of the light pipe 104, according to yet another example of the present subject matter. In one example, the top view' 602 depicts a view of the light pipe 104 in a direction perpendicular to the surface of the paper. Further, the side view' 604 depicts a view' of the light pipe 104 in a direction along the surface of the paper. The light pipe 104 includes the plurality of branches 1 10 and the sensor assembly 1 12, In Figure 6, each of the branch 110 in the top view' 602 has been mapped to the corresponding branch 110 in the side view 604 to indicate how each branch 110 may look in the two views.

[0054] As illustrated in the side view' 604, each of the branches 110 extends radially outward from the light pipe 104. As previously described, each of the plurality' of branches 110 extends radially outward into the corresponding slot 108. Further, in said example, the third branch 110-n is the longest branch positioned farthest from the sensor assembly 112, at the second end 204. Further, the first branch 110-1 is the shortest branch positioned closest to the sensor assembly 112, proximate to the first end 1 14 than the second end 204. Further, as illustrated, the first branch 110-1 and the second branch 1 10-2 are positioned one same side of the third branch 1 10-n.

[0055] Figure 7 illustrates example method 700 of detecting at least one of print medium size and presence of print medium in an input tray of a print device, according to another example of the present subject matter. The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the aforementioned methods, or an alternative method. Furthermore, the method 700 may be implemented by processing resource or computing device(s) through any suitable hardware, non-transitory machine readable instructions, or combination thereof.

[00S6] It may also be understood that the method 700 may be performed by light pipes, such as the light pipe 104 installed in printing devices, such as the print device 100. Furthermore, the method 700 may be executed based on instructions stored in a non-transitory computer readable medium, as will be readily understood. The non-transitory computer readable medium may include, for example, digital memories, magnetic storage media, such as one or more magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media.

[00S7] At block 702, light of a certain intensity is emitted within a light pipe disposed in an input tray of a print device. In one example, the light is emitted by a light emitting source, such as LED in the direction of a plurality of branches of the light pipe, opening into a plurality of slots provided on the input tray. In one example, each slot is provided at different positions indicative of a different print medium size. Further, in one example, the light emitting source may continuously emit the light. In another example, the light emitting source may emit the light at regular intervals. Further, the light emitting source is placed at a first end of the light pipe.

[0058] At block 704, light reflected back from at least one branch is received by a phototransistor positioned alongside the light emitting source at a first end of the light pipe. In one example, the photo transistor, such as the phototransistor 416 receives the light reflected back from the at least one branch upon placement of the print medium over the corresponding slot on the input tray. In one example, the light is reflected back in the light pipe from all the branches for which the corresponding slot is covered by the print medium.

[0059] At block 706, intensity of light reflected from the at least one branch within the light pipe is detected. In one example, the intensity of light is detected by the phototransistor, such as the phototransistor 416. The intensity of light is related to the number of slots 108 covered by the print medium and may vary based on the print medium size.

[0080] At block 708, an output signal is generated in accordance to the detected intensity of light. In one example, the output signal is generated may be generated by the phototransistor to indicate presence of the print medium and the print medium size. A voltage level of the output signal, in one example, may vary in accordance to the print medium size to indicate the presence of the print medium and the print medium size.

[0061] Although examples for the present subject matter have been described in language specific to structural features and/or methods, it should be understood that the appended claims are not limited to the specific features or methods described. Rather, the specific features and methods are disclosed and explained as examples of the present subject matter.