JP2007118264A - Poor liquid discharge detecting device, and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify a structure, and to surely detect a poor liquid discharge, in a poor liquid discharge detecting device which detects the poor discharge of a liquid from a variation of the light receiving quantity of a light receiving element, being constituted in such a manner that light is emitted from a light emitting element in a direction being orthogonal to the discharging direction of the liquid, and the light is made to face the light receiving element. <P>SOLUTION: Light which goes to the light receiving side 40 from the light emitting side 30 by passing through a poor liquid discharge detecting region A is provided in a manner to be crossed to the liquid discharging direction n. On the light emitting side, the light emitting element 31 such as a semiconductor laser or an LED, a restricting member 32 such as a collimate lens or a slit which restricts the light beam emitted by the light emitting element, and a second polarizer 33 which is set by tilting the polarizing direction at approximately 45° to the liquid discharging direction when required are provided. On the light receiving side, a polarizer 41 which is set by tilting the polarizing direction at approximately 90° to the polarizing direction on the light emitting side, and the light receiving element 42 such as a photo diode are provided. Then, since the light receiving quantity on the light receiving side changes depending on the presence/absence of the discharged liquid such as ink droplets, the poor discharge of the liquid is detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention has a configuration in which light is emitted from a light emitting element in a direction intersecting a liquid ejecting direction such as ink droplets and the light is received by the light receiving element, and a liquid ejection failure is detected from a change in the amount of light received by the light receiving element. The present invention relates to a liquid discharge defect detection device. The present invention also relates to an ink jet recording apparatus that includes such a liquid discharge defect detection device and records an image on a recording medium with ink droplets discharged from an ink jet head.

  2. Description of the Related Art Conventional inkjet recording apparatuses include an inkjet head that ejects minute ink droplets from minute nozzles, and performs recording by ejecting ink droplets from the nozzles while relatively moving the inkjet head and a recording medium such as paper. An image was recorded on the medium. This type of ink jet recording apparatus is widely used because it has advantages such as high speed and low noise, few restrictions on the type of recording medium, and easy colorization.

  However, since ink droplets are ejected from fine nozzles, the ink is easy to dry when stopped, the nozzle surface gets wet with ink, and dust such as paper dust tends to adhere to the nozzle surface, and air enters from the nozzle. This causes problems such as non-ejection and bending of the ejection direction, resulting in defective ejection of ink droplets, resulting in missing dots and white streaks in the image, resulting in poor image quality. There was a bug.

  In order to prevent the occurrence of such problems, a conventional inkjet recording apparatus includes a light emitting element such as an LED and a light receiving element such as a photodiode, and a direction perpendicular to the ink droplet ejection direction from the light emitting element. Some of them include a liquid discharge defect detection device that optically detects a liquid discharge defect from a change in the amount of light received by the light receiving element.

  When detecting a liquid ejection failure, light is emitted from the light emitting element, then ink droplets are ejected in order from the nozzles at the end, and the ink droplet ejection is confirmed from the decrease in the amount of light received by the light receiving element. Insufficient ink droplet ejection was detected. When an ejection failure is detected, the inkjet head is moved to the recovery device position, and the recovery device recovers the ink by sucking ink from the nozzle that caused the ejection failure.

  Conventionally, there are ink jet recording apparatuses provided with such a liquid ejection defect detection apparatus, for example, those described in Patent Document 1 and Patent Document 2 below. In the ink jet recording apparatus described in Patent Document 1, in view of the fact that the longer the ink jet head becomes due to light diffraction or the like, the longer the ink jet head becomes, the more reliably non-ejection can be detected. It is made to detect by dividing.

  In addition, for example, in the inkjet recording apparatus described in Patent Document 2 below, since a recovery device that recovers by sucking ink from a nozzle when a discharge failure occurs is provided outside the recording area, the apparatus becomes larger, In view of wasteful consumption of ink, the inkjet head is supported rotatably around a support member to a position where the nozzles deviate from a predetermined angle from a position facing the recording medium.

Japanese Patent No. 3501599 JP 2005-119268 A

  However, in the ink jet recording apparatus provided with the liquid discharge failure detection device that optically detects the liquid discharge failure described above, there is a sufficient amount of received light even when there is an ink drop. There is a problem that the difference in the amount of light received by the elements is small and the detection of ejection failure is uncertain.

  Further, as in the conventional liquid discharge failure detection device described in Patent Document 1, the ink droplet discharge from a plurality of nozzles is divided and detected in half, or the conventional liquid discharge failure detection device described in Patent Document 2 is detected. As described above, there is a problem that the structure becomes complicated when the inkjet head is rotatably supported around the support member.

  Accordingly, a first object of the present invention is to emit light from a light emitting element in a direction crossing the liquid ejection direction such as ink droplets and to direct the light to the light receiving element. From the change in the amount of light received by the light receiving element, In a liquid discharge failure detection device that detects a liquid discharge failure, the structure is simplified and the liquid discharge failure is reliably detected.

  A second object of the present invention is to provide an ink jet recording apparatus which can detect an ejection failure of an ink droplet reliably with a simple structure.

  For this reason, in order to achieve the above-described first object of the present invention, the first aspect of the present invention is provided by crossing the light from the light emitting side to the light receiving side with respect to the liquid ejection direction, such as ink droplets. Since the amount of light received by the light receiving element on the light receiving side, for example, a photodiode, changes depending on the presence or absence of the discharge liquid, in the liquid discharge failure detecting device that detects a liquid discharge failure, the light emitted from the light emitting side and the polarization direction are different. Different polarizers are provided on the light receiving side.

  When a liquid ejection failure is detected, the light emitted from the light emitting side is directed to the light receiving side, while the liquid is ejected from a nozzle or the like. In this case, when the liquid is normally discharged, the liquid is blocked by the discharged liquid to scatter light, and a part of the scattered light passes through the polarizer and enters the light receiving side. On the other hand, when the liquid is not normally ejected, the light is directly applied to the polarizer without blocking the light by the ejected liquid, and the light on the light emission side is prevented from entering the light receiving side by the polarizer. As a result, the scattered light is detected and the amount of received light on the light receiving side increases, so that liquid ejection is confirmed. On the other hand, since the amount of received light is small by blocking with a polarizer, liquid ejection failure is detected. That is, a liquid ejection failure is detected from the change in the amount of received light on the light receiving side.

  The light emitting side includes, for example, a light emitting element such as a semiconductor laser or an LED, and a diaphragm member such as a collimator lens or a slit for narrowing a light beam emitted from the light emitting element. In addition, the light emitting element is a semiconductor laser, and the polarization direction thereof is inclined at about 45 degrees with respect to the liquid discharge direction, while the polarizer provided on the light receiving side is set to have a polarization direction of about 90 degrees with respect to the polarization direction of the semiconductor laser. It should be installed at an angle.

  On the light emitting side, the second polarizer is installed with the polarization direction inclined at about 45 degrees with respect to the liquid ejection direction, while on the light receiving side, the polarizer is placed, and the polarization direction is the polarization direction of the second polarizer. It is good to install it at 90 degrees. Further, on the light receiving side, a polarizer and a light receiving element may be provided in one light shielding cylinder. Furthermore, a light stopper may be provided on the light receiving side to block the light beam focused by the diaphragm member. As the polarizer and the second polarizer, a polarizing plate, a mirror, a polarizing beam splitter, or the like is used.

  According to a second aspect of the present invention, in order to achieve the above-described second object of the present invention, an ink jet recording apparatus is provided with the above-described liquid discharge failure detecting device.

  According to the first aspect of the present invention, the light emission side emits light in a direction intersecting the liquid discharge direction and the light is received on the light reception side. In the liquid discharge failure detecting device for detecting the light, the structure is very simple because the light receiving side only includes a polarizer having a polarization direction different from that of the light emitted on the light emitting side.

  Moreover, since the scattered light is received and the amount of light received on the light receiving side is large, liquid ejection is confirmed, while the light received by the polarizer is shielded and the amount of received light is small and close to zero, so liquid ejection failure is detected. The ratio of the amount of received light on the light receiving side with and without the discharge liquid can be increased, and the detection of liquid discharge failure can be ensured.

  In addition, if a diaphragm member is provided for narrowing the light beam emitted by the light emitting element, if the liquid is not ejected normally, the light throttled by the diaphragm member is applied to the polarizer, and the light on the light emission side is received by the polarizer. Provided with a liquid discharge defect detection device that reliably prevents the liquid from entering the side, clarifies the difference in the amount of light received on the light receiving side with and without the discharge liquid, and more reliably detects liquid discharge defects be able to. In addition, the semiconductor laser can cope with downsizing and cost reduction, has good coherence, is easy to make parallel light, and when a semiconductor laser is used as a light emitting element, for example, when a long inkjet head is used, An effective liquid discharge defect detection device can be provided.

  On the light emitting side, the second polarizer is installed with the polarization direction tilted at about 45 degrees with respect to the liquid ejection direction, while on the light receiving side, the polarizer is set to be the polarization direction of the second polarizer. If the projector is installed at an angle of approximately 90 degrees, the amount of scattered light can be detected efficiently, and the ratio of the amount of received light on the light receiving side with and without ejected liquid can be increased. Further, if the polarizer and the light receiving element are provided in one light shielding cylinder on the light receiving side, the entry of disturbance light can be prevented and the detection efficiency can be improved.

  By providing a beam stopper on the light receiving side and blocking the light beam focused by the diaphragm member, the light blocking performance of the main light component is improved and the detection gain can be increased. In addition, if a polarizer, a mirror, a polarizing beam splitter, etc. are used as the polarizer and the second polarizer, the degree of freedom in design can be improved, the size can be reduced, and the structure can be simplified and the cost can be reduced. It becomes.

  On the other hand, according to the second aspect of the present invention, since the liquid discharge failure detecting device according to any one of claims 1 to 7 is provided, the structure can be simplified and the discharge failure of the ink droplet can be reliably detected. An ink jet recording apparatus can be provided.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1A shows an ink jet printer provided with a liquid ejection failure detection device according to the present invention as seen from the front, and FIG.

  Reference numeral 10 in the figure denotes a housing. A guide shaft 13 and a guide plate 14 are provided in parallel on the left and right side plates 11 and 12 of the housing 10. The guide shaft 13 and the guide plate 14 support the carriage 15. An endless belt (not shown) is attached to the carriage 15. The endless belt is wound around a driving pulley and a driven pulley (not shown) provided on the left and right sides of the housing 10. The endless belt travels while the driven pulley rotates following the rotation of the driving pulley, and the carriage 15 is slidable left and right as indicated by arrows in the figure.

  On the carriage 15, four color ink jet heads 16 y, 16 c, 16 m, and 16 b of yellow, cyan, magenta, and black are arranged in the moving direction of the carriage 15. Each inkjet head 16 has a plurality of nozzles downward. Although not shown, the plurality of nozzles are formed side by side in a direction orthogonal to the moving direction of the carriage 15.

  When the carriage 15 is at the rightmost home position shown in the figure, each inkjet head 16 faces the recovery device 18 installed on the bottom plate 17 in the housing 10. The recovery device 18 is a device that sucks out ink from nozzles that have failed to eject ink droplets and recovers ejection failures.

  On the bottom plate 17 in the housing 10, the liquid ejection failure detection device 20 according to the present invention is provided next to the recovery device 18. The liquid discharge failure detection device 20 will be described later in detail with reference to FIG.

  A plate-like platen 22 is installed upward at a position adjacent to the liquid ejection failure detection device 20. On the back side of the platen 22, a paper feed stand 24 for supplying a paper 23 as a recording medium is provided on the platen 22 in an oblique manner. Although not shown, a paper feed roller for feeding the paper 23 on the paper feed tray 24 onto the platen 22 is provided. Further, a transport roller 25 is provided for transporting the paper 23 on the platen 22 in the direction of the arrow and discharging it to the front side.

  On the bottom plate 17 in the housing 10, a driving device 26 is further installed at the left end. The driving device 26 drives a feed roller (not shown), a conveying roller 25, and the like, and drives the above-described driving pulley to travel the endless belt and move the carriage 15.

  During recording, the driving device 26 drives the paper 23 onto the platen 22, positions it at a predetermined position, moves the carriage 15 to scan the paper 23, and moves the four colors while moving in the left direction. The ink jet heads 16y, 16c, 16m, and 16b are used to sequentially eject ink droplets from the respective nozzles to record an image on the paper 23. After image recording, the carriage 15 is returned to the right and the sheet 23 is conveyed by a predetermined amount in the direction of the arrow.

  Next, while moving the carriage 15 to the left again, ink droplets are sequentially ejected from the respective nozzles using the four-color inkjet heads 16 y, 16 c, 16 m, and 16 b on the forward path to record an image on the paper 23. Similarly, after image recording, the carriage 15 is returned to the right and the paper 23 is conveyed by a predetermined amount in the direction of the arrow. Thereafter, the same is repeated, and an image is recorded on one sheet of paper 23.

  FIG. 2 shows a state in which an ejection failure of an ink droplet from a nozzle of one inkjet head 16 is detected using the liquid ejection failure detection device 20 as viewed from the left side in the axial direction of the guide shaft 13.

  In the figure, n 1, n 2, n 3, n 4, n 5,... Nx represents the direction of liquid ejection from each nozzle of one inkjet head 16 mounted on the carriage 15. The liquid ejection failure detection device 20 is configured to linearly provide an optical axis in a direction perpendicular to the liquid ejection direction and to direct light from the light emitting side 30 toward the light receiving side 40.

  The light emitting side 30 includes a light emitting element 31, a diaphragm member 32 for narrowing a light beam emitted from the light emitting element 31, and a second polarizer 33 using a polarizing plate. As the light emitting element 31, a semiconductor laser is used. In the semiconductor laser, although the emitted light is strongly linearly polarized, the polarization direction Pθ1 is inclined approximately 45 degrees with respect to the liquid ejection direction n as shown in FIG. As the diaphragm member 32, a collimator lens is used in which light emitted from the light emitting element 31 is parallel light having a beam diameter d. As shown in FIG. 3, the second polarizer 33 is installed with the polarization direction inclined to approximately 45 degrees with respect to the liquid ejection direction n in accordance with the polarization direction Pθ1 of the light emitting element 31.

  On the other hand, the light receiving side 40 includes a polarizer 41 using a polarizing plate and a light receiving element 42 using, for example, a photodiode. As shown in FIG. 3, the polarizer 41 is installed such that its polarization direction Pθ2 is inclined at approximately 45 degrees with respect to the liquid ejection direction n and is inclined at approximately 90 degrees with respect to the polarization direction Pθ1 of the light emitting element 31 made of a semiconductor laser. That is, (Pθ1 + Pθ2) is set to approximately 90 degrees. The light receiving element 42 is provided in a can package.

  Thereby, on the light emitting side 30, a light beam is emitted from the light emitting element 31, and the light beam is converted into parallel light by the diaphragm member 32, passes through the second polarizer 33 and passes through the liquid discharge defect detection area A, Although it strikes the polarizer 41 on the light receiving side 40, the light entering the light receiving element 40 is blocked by the polarizer 41 and completely blocked.

  In this example, a collimating lens is used as the diaphragm member 32 to convert the light beam from the light emitting element 31 into parallel light. However, the diaphragm member 32 may squeeze the light beam from the light emitting element 31, and the collimated lens is not necessarily converted into parallel light. It is not limited.

  In the case of the short inkjet head 16, if an LED is used as the light emitting element 31, the cost can be reduced. Also in this case, the second polarizer 33 is installed on the light emitting side 30 with the polarization direction tilted at about 45 degrees with respect to the liquid discharge direction, while the polarizer 41 provided on the light receiving side 40 is set to the second polarization direction. It is installed at an angle of approximately 90 degrees with the polarization direction of the element 33.

  By the way, in the illustrated inkjet printer, recording is performed on a certain number of sheets of paper 23 when the power is turned on, when a certain time has elapsed since the previous detection of liquid discharge failure, or after the previous detection of liquid discharge failure. When it is performed, the detection of liquid discharge failure is automatically started. Further, when the user operates the detection switch, detection of liquid discharge failure is started.

  When a liquid discharge failure is detected, the light emitted from the light emitting element 31 is squeezed by the diaphragm member 32 on the light emitting side 30 and passed through the second polarizer 33 as parallel light, and then the liquid discharge failure detection area A , And directed toward the light receiving side 40, for example, ink droplets are ejected sequentially from the ends of a plurality of nozzles of the inkjet head 16y. In this case, when the ink droplets are ejected normally, the ejected liquid blocks the light beam 34 and scatters the light. Of the scattered light, only linearly polarized light that matches the polarizer 41 causes the polarizer 41 to be scattered. The light is transmitted and only a part of the light passes through the polarizer 41 on the light receiving side 40 and enters the light receiving element 42.

Here, when the ink droplet diameter is several μm to several tens of μm, for example, as shown in the figure, it is scattered like S1, S2, S3, S4, S5, S6, S7, S8, and the scattering intensity is
S1> S2, 3> S4, 5> S6, 7> S8
The forward scattered light (S1-5) becomes stronger than the backscattered light (S6-8).

  On the other hand, when the ink droplets are not ejected normally, the light beam 34 that has passed through the second polarizer 33 passes through the liquid ejection failure detection area A and is directly polarized without blocking the light beam 34 with the ejected liquid. The light from the light emitting element 31 is prevented from entering the light receiving element 42 by being applied to the child 41. As a result, the scattered light is detected and the amount of light received by the light receiving element 42 is increased, so that the ejection of the ink droplet is confirmed, while the light received by the polarizer 41 is shielded so that the amount of received light is almost small. Detect droplet ejection failure. That is, since the amount of light received by the light receiving element 31 on the light receiving side 40 changes depending on the presence or absence of the ejection liquid, the ink droplet ejection failure is detected.

  After detecting ink droplet ejection defects sequentially from the ends of the plurality of nozzles provided in the yellow inkjet head 16y, the carriage 15 is moved to make the cyan inkjet head 16c the position of the liquid ejection defect detection device 20. Similarly, ink droplet ejection defects are sequentially detected from the ends of a plurality of nozzles provided in the cyan inkjet head 16c, and then magenta inkjet head 16m and black inkjet head 16b are sequentially detected. I do.

  When there is an ink droplet ejection defect, in this example, the carriage 15 is returned to the home position, and the recovery device 18 sucks ink from the nozzles of the inkjet head 16 to eliminate clogging of the nozzles. At this time, wasteful consumption of ink can be prevented by sucking ink not from all nozzles but from a limited nozzle including nozzles that have detected ejection failure or surrounding nozzles.

  In the above-described example, the polarizer 41 and the second polarizer 33 are polarizing plates, so that the polarizer 41 and the second polarizer 33 can be arranged in a straight line on the optical axis, the structure is simple, and the cost can be reduced. If the intensity ratio of the polarization characteristics of the light emitting element 31 is good, the polarizer 41 can be arranged so that the direction of linearly polarized light and the light emitted from the light emitting side 30 are arranged orthogonally without needing to include the second polarizer 33. It may be provided only, and in that case, further cost reduction can be realized.

As shown in FIG. 4, on the light receiving side 40, for example, a metal beam is deposited on the center of the polarizer 41 to form a circular beam stopper 43 by aligning the optical axis. When blocked, the light blocking performance of the main light component is improved and the detection gain can be increased. At this time, if the diameter of the light beam 34 focused by the diaphragm member 32 is d and the outer diameter of the beam stopper 43 is ds,
d <ds
It is good to set so that.

  Similarly, on the light receiving side 40, if a polarizer 41 and a light receiving element 42 are provided in one light shielding cylinder 44 as shown in FIG. Can be prevented and detection efficiency can be improved.

  6 to 9 show cases where mirrors are used as the polarizer 41 and the second polarizer 33. 6 shows an overall schematic configuration of the liquid discharge failure detection device 20 in that case, FIG. 7 shows the liquid discharge failure detection device 20 as viewed from the side, and FIG. 8 shows the light emitting element 31 and the second structure. The positional relationship with the polarizer 33 is shown. FIG. 9 shows the positional relationship between the light receiving element 42 and the polarizer 41.

  In this example, the light emitting element 31 is provided on the optical axis a inclined approximately 45 degrees (θY1) with respect to the liquid ejection direction n of the inkjet head 16, and the optical axis a and the optical axis when passing through the liquid ejection failure detection area A are provided. A second polarizer 33, which is a mirror, is arranged at the intersection with b. On the other hand, a light receiving element 42 is provided on an optical axis c that is orthogonal to the optical axis a and inclined approximately 45 degrees (θY2) with respect to the liquid ejection direction n, and polarized light that is a mirror at the intersection of the optical axis c and the optical axis b. The child 41 is arranged.

  The direction Lθ1 in which the light emitting element 31 is strongly linearly polarized reflects the linearly polarized light S incident parallel to the reflecting surface of the second polarizer 33. On the other hand, the linearly polarized light P incident perpendicularly to the reflecting surface has zero reflectivity by setting the incident angle with the perpendicular M1 to the Brewster angle Bm1.

  Since the linearly polarized light S polarized on the optical axis b by the second polarizer 33 is orthogonal to the optical axis a and the optical axis c, it becomes P-polarized when viewed from the incident on the polarizer 41, and the incident angle is By setting the Brewster angle Bm2, the reflectance becomes zero and the light is not reflected by the reflection surface of the polarizer 41. The output value of the light receiving element 42 is in a none state. On the other hand, when ink droplets are ejected and scattered light is generated, the S-polarized light is reflected and detected by the light receiving element 42.

  10 to 13 show a case where a polarizing beam splitter is used as the polarizer 41 and the second polarizer 33. 10 shows an overall schematic configuration of the liquid discharge failure detection device 20 in that case, FIG. 11 shows the liquid discharge failure detection device 20 as viewed from the side, and FIG. The positional relationship with the polarizer 33 is shown, and FIG. 13 shows the positional relationship between the light receiving element 42 and the polarizer 41.

  In this example, the light emitting element 31 is provided on the optical axis a inclined approximately 45 degrees (θY1) with respect to the liquid ejection direction n of the inkjet head 16, and the optical axis a and the optical axis when passing through the liquid ejection failure detection area A are provided. A second polarizer 33, which is a polarization beam splitter, is disposed at the intersection with b. On the other hand, a light receiving element 42 is provided on an optical axis c that is orthogonal to the optical axis a and inclined approximately 45 degrees (θY2) with respect to the liquid ejection direction n. A polarizing beam splitter is provided at the intersection of the optical axis c and the optical axis b. A certain polarizer 41 is arranged.

  The direction Lθ1 in which the light emitting element 31 is strongly linearly polarized is incident perpendicularly to the incident surface NM of the second polarizer 33 and reflects the linearly polarized light S incident parallel to the reflecting surface RM. On the other hand, the linearly polarized light P incident perpendicularly to the reflecting surface RM is transmitted without being reflected.

  Since the linearly polarized light S polarized on the optical axis b by the second polarizer 33 is orthogonal to the optical axis a and the optical axis c, it is P-polarized when viewed from the incident on the polarizer 41 and is not reflected. To Penetrate. The output value of the light receiving element 42 is in a none state. On the other hand, when ink droplets are ejected and scattered light is generated, the S-polarized light is reflected and detected by the light receiving element 42.

(A) is a front view of an ink jet printer provided with a liquid discharge defect detection device according to the present invention, and (B) is a perspective view showing a part thereof obliquely from above. It is a figure which shows the state which has detected the discharge failure of the ink droplet from the nozzle of one inkjet head using the liquid discharge failure detection apparatus from the left side in the axial direction of a guide shaft. FIG. It is a description perspective view in the case of providing a beam stopper in the polarizer. It is a description perspective view in the case of providing a light shielding cylinder on the light receiving side. It is a whole schematic block diagram of the liquid discharge defect detection apparatus at the time of using a mirror as the polarizer and the 2nd polarizer. It is the figure which looked at the liquid discharge defect detection device from the side. It is a positional relationship figure of the light emitting element and the 2nd polarizer. FIG. 4 is a positional relationship diagram between the light receiving element and a polarizer. It is a whole schematic block diagram of the liquid discharge defect detection apparatus at the time of using a polarization beam splitter as a polarizer and a 2nd polarizer. It is the figure which looked at the liquid discharge defect detection device from the side. It is a positional relationship figure of the light emitting element and the 2nd polarizer. FIG. 4 is a positional relationship diagram between the light receiving element and a polarizer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Liquid discharge defect detection apparatus 30 Light receiving side 31 Light receiving element 32 Diaphragm member 33 2nd polarizer 34 Light beam 40 Light receiving side 41 Polarizer 42 Light receiving element 43 Beam stopper 44 Light-shielding cylinder n, n1, n2, n3, ..., nx Liquid discharge direction A Liquid discharge failure detection area

Claims (10)

In the liquid discharge failure detection device for detecting a liquid discharge failure because light traveling from the light emitting side to the light receiving side is provided crossing the liquid discharge direction, and the amount of light received on the light receiving side changes depending on the presence or absence of the discharge liquid. ,
A liquid ejection defect detecting device comprising a polarizer on the light receiving side having a polarization direction different from that of light emitted on the light emitting side.   The liquid discharge defect detection device according to claim 1, further comprising: a light emitting element and a diaphragm member that narrows a light beam emitted from the light emitting element on the light emitting side.   The light emitting element is a semiconductor laser and the polarization direction thereof is inclined at about 45 degrees with respect to the liquid ejection direction, while the polarizer provided on the light receiving side is defined as the polarization direction of the semiconductor laser. 3. The liquid discharge failure detection device according to claim 2, wherein the liquid discharge failure detection device is installed at an angle of approximately 90 degrees.   The second polarizer is installed on the light emitting side with the polarization direction tilted at about 45 degrees with respect to the liquid ejection direction, while the polarizer provided on the light receiving side is set to the polarization direction of the second polarizer. 4. The liquid discharge failure detection device according to claim 1, wherein the liquid discharge failure detection device is installed at an angle of approximately 90 degrees to the direction.   5. The liquid ejection defect detection device according to claim 1, wherein the polarizer and the light receiving element are provided in one light shielding tube on the light receiving side.   6. The liquid ejection defect detection device according to claim 2, wherein a beam stopper is provided on the light receiving side, and the light beam focused by the aperture member is blocked.   The liquid ejection defect detection device according to claim 4, wherein a polarizing plate is used as the polarizer and the second polarizer.   The liquid discharge defect detection device according to claim 4, wherein a mirror is used as the polarizer and the second polarizer.   The liquid ejection defect detection device according to claim 4, wherein a polarizing beam splitter is used as the polarizer and the second polarizer.   An ink jet recording apparatus comprising the liquid discharge failure detecting device according to claim 1.

Images