JP2011161673A - Apparatus for detecting liquid poor delivery and inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for detecting liquid poor delivery, which conveniently detects the poor delivery of liquid droplets, and to provide an inkjet recording apparatus. <P>SOLUTION: The apparatus for detecting poor delivery of the liquid includes: a light emitting element 30 for irradiating a plurality of optical beams in which the optical intensity decreases toward the outside from the optical axis, and when observed from a nozzle delivering liquid droplets, the parts decreasing the optical intensity intersect mutually on the flying path of the liquid droplets; a light receiving element 103 for receiving a scattered light generated by colliding a plurality of the optical beams to the liquid droplets; and a detecting part 104 for detecting the poor delivery of the liquid droplets based on the optical intensity of the scattered light. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid ejection defect detection device and an ink jet recording apparatus.

  The ink jet recording apparatus includes an ink jet head of each color for ejecting minute ink droplets from minute nozzles, and ejects ink droplets while moving the ink jet head with respect to a recording medium such as paper. Perform image formation. In order to form a high-resolution image, it is necessary to reduce the size of the ink droplets by reducing the size of the nozzles. In this case, since the nozzles are fine, nozzle clogging occurs due to drying of the ink when printing is stopped, ink droplet ejection failure occurs, dot dropout occurs in the image, and the image quality is degraded.

  Conventionally, an ink jet recording apparatus has been provided with a liquid discharge failure detection device that detects a liquid discharge failure in order to prevent image quality deterioration due to nozzle clogging. For example, in Patent Document 1, the intensity of the light beam is changed by an optical filter, and the fact that the output of the light receiving element is different depending on the position where the droplet has passed among the portions where the intensity changes is used. Techniques have been proposed for detecting flight path bending.

JP 2006-184161 A

  However, since the method of Patent Document 1 is based on the premise that an optical filter and two light receiving elements are used, there is a problem that the configuration becomes complicated and the cost increases.

  The present invention has been made in view of the above, and an object of the present invention is to provide a liquid ejection defect detection device and an ink jet recording apparatus that can more easily detect a droplet ejection defect.

  In order to solve the above-described problems and achieve the object, the present invention provides a portion in which the light intensity decreases from the optical axis toward the outside, and the light intensity decreases when observed from a nozzle that discharges droplets. Light emitting means for irradiating a plurality of light beams intersecting each other on the flight path of the droplet, light receiving means for receiving scattered light generated when the plurality of light beams collide with the droplet, and light intensity of the scattered light And detecting means for detecting a discharge failure of the droplet based on the above.

  According to the present invention, it is possible to detect a droplet discharge failure more easily.

FIG. 1 is a front view of an ink jet printer (ink jet recording apparatus) provided with the liquid ejection failure detection apparatus according to the first embodiment. FIG. 2 is a block diagram illustrating an example of a functional configuration of the ink jet printer according to the first embodiment. FIG. 3 is a diagram illustrating an example of a positional relationship between a plurality of light emitting elements and a plurality of light receiving elements observed from the ejection direction of the nozzle nx. FIG. 4 shows an enlarged view of the vicinity of the intersection of the light beams. FIG. 5 is a diagram showing an intensity distribution of a light beam emitted from the light emitting element. FIG. 6 is a diagram showing an intensity distribution of a light beam emitted from the light emitting element. FIG. 7 is a diagram illustrating an output example of the light receiving element when the ink droplet passes through each of the positions a to i in FIG. 4. FIG. 8 is a block diagram illustrating an example of a functional configuration of the ink jet printer according to the second embodiment. FIG. 9 is a diagram illustrating an example of a positional relationship between a plurality of light emitting elements and one light receiving element observed from the ejection direction of the nozzle nx. FIG. 10 shows an enlarged view of the vicinity of the intersection of the light beams. FIG. 11 is a diagram illustrating a state in which a signal corresponding to scattered light is separated from an output signal of one light receiving element. FIG. 12 is a diagram illustrating an example of the frequency spectrum of the output signal. FIG. 13 is a diagram illustrating a modification including a mask.

  Exemplary embodiments of a liquid ejection failure detection apparatus and an ink jet recording apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a front view of an ink jet printer (ink jet recording apparatus) 100 including a liquid ejection defect detecting device according to the first embodiment.

  As shown in FIG. 1, 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 casing 10 of the inkjet printer 100. The guide shaft 13 and the guide plate 14 are slidably penetrated through 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. Then, the driven pulley is driven to rotate along with the rotation of the driving pulley, and travels on the endless belt. As a result, the carriage 15 is moved to the left and right as indicated by the arrows in FIG.

  In the carriage 15, four color ink jet heads 16 y, 16 c, 16 m and 16 b (hereinafter simply referred to as the head 16) of yellow, cyan, magenta, and black are arranged in parallel in the moving direction of the carriage 15. Each head 16 has a nozzle row in which a plurality of nozzles are linearly arranged on a downward nozzle surface. Although not shown, the linear nozzle row is provided in a direction orthogonal to the moving direction of the carriage 15.

  When the carriage 15 is in the rightmost home position as shown in FIG. 1, each head 16 faces the single recovery device 18 installed on the bottom plate 17 in the housing 10. The single recovery device 18 is a device that sucks out ink from the nozzle that has detected the ink droplet discharge failure by the liquid discharge failure detection device 20 and recovers the liquid discharge failure independently by the inkjet printer 100 itself.

  The liquid discharge failure detection device 20 is disposed adjacent to the single recovery device 18 on the bottom plate 17 in the housing 10. Details of the liquid discharge failure detection device 20 will be described later.

  A plate-like platen 22 is installed at a position adjacent to the liquid discharge failure detection device 20. On the back side of the platen 22, a paper feed base 24 that supplies the paper 23, which is a recording medium, onto the platen 22 is provided in an oblique manner. Although not shown, a paper feed roller for feeding the paper 23 on the paper feed table 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.

  At the time of recording, the paper 23 is moved onto the platen 22 by being driven by the driving device 26 and positioned at a predetermined position. Further, the carriage 15 is moved and scanned on the paper 23, and ink droplets are sequentially ejected from the respective nozzles using the four-color heads 16y, 16c, 16m, and 16b while moving to the left. An image is recorded. After image recording, the carriage 15 is returned to the right and the paper 23 is conveyed by a predetermined amount.

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

  Next, the functional configuration of the inkjet printer 100 according to the first embodiment will be described. FIG. 2 is a block diagram illustrating an example of a functional configuration of the inkjet printer 100 according to the first embodiment. The inkjet printer 100 according to the first embodiment mainly includes a head 16, an ejection control unit 101, a light emission control unit 102, a light emitting element 30, a light receiving element 103, and a detection unit 104. .

  The inkjet printer 100 according to the first embodiment performs a liquid ejection failure detection process for detecting whether or not ink droplets are normally ejected from nozzles nx (1 ≦ x ≦ N, where N is the number of nozzles). In the liquid ejection failure detection process, a light beam is emitted from the light emitting element 30 to the flight path of the ink droplet, and the ink droplet is ejected from the nozzle nx to the emitted light beam to generate scattered light from the ink droplet. The light receiving element 103 receives the scattered light, and the detection unit 104 detects whether or not the ink droplet has been normally ejected based on an output voltage obtained by receiving the scattered light.

  In FIG. 2, components having functions mainly related to the liquid ejection failure detection process are shown, and components related to image recording are not shown.

  The ejection control unit 101 controls ejection processing for ejecting ink droplets from each nozzle of the head 16.

  The light emission control unit 102 controls light emission processing for causing the light emitting element 30 to emit light. For example, in the liquid discharge failure detection process, the light emission control unit 102 sends a light emission control signal having a constant voltage value to continuously light up the light emitting element 30.

  The light emitting element 30 is a light emitting element such as a semiconductor laser, for example, and is turned on according to a light emission control signal sent from the light emission control unit 102 to generate a light beam. The light emitting element 30 is preferably a laser diode that emits forward scattered light strongly when it touches an ink droplet. It is assumed that the width of the light beam is sufficiently larger than the ink droplets to be passed. When the head 16 is short, the cost can be reduced by using an LED as the light emitting element 30.

  In FIG. 2, only one light emitting element 30 is displayed, but in the present embodiment, a plurality of light beams are generated from the plurality of light emitting elements 30. Each of the light emitting elements 30 emits a light beam whose light intensity decreases from the optical axis toward the outside. Each of the light emitting elements 30 irradiates the light beam so that the portions where the light intensity of the light beam is reduced intersect each other on the flight path of the droplet when observed from the nozzle side.

  The light receiving element 103 is a light receiving element that receives scattered light generated when a light beam emitted from the light emitting element 30 collides with an ink droplet.

  The light receiving element 103 can be configured by a light receiving element such as a photodiode, for example. The light receiving element 103 generates a current proportional to the intensity of received light, converts the generated current into a voltage, and outputs a voltage value (hereinafter also referred to as an output signal) representing the received light intensity. In addition, you may comprise so that the function to convert an electric current into a voltage may be provided in the exterior of a light receiving element.

  In FIG. 2, only one light receiving element 103 is displayed, but in the present embodiment, a plurality of light receiving elements 103 respectively corresponding to the plurality of light emitting elements 30 are provided. The plurality of light receiving elements 103 respectively receive scattered light generated when the light beams emitted from the corresponding light emitting elements 30 collide with the ink droplets.

  The detection unit 104 detects an ink droplet ejection failure from the output signal output from the light receiving element 103. Details of the ejection failure detection processing by the detection unit 104 will be described later.

  Next, the positional relationship between the plurality of light emitting elements 30 and the plurality of light receiving elements 103 will be described. FIG. 3 is a diagram illustrating an example of a positional relationship between the plurality of light emitting elements 30 and the plurality of light receiving elements 103 observed from the ejection direction of the nozzle nx. FIG. 3 shows an example in which light beams 31a and 31b intersecting at substantially right angles are irradiated from two light emitting elements 30a and 30b, respectively.

  For example, the light emitting elements 30a and 30b irradiate the light beams 31a and 31b so as to intersect at a substantially right angle at the intersection with the flight path of the ink droplet on a plane that intersects the ejection direction of the ink droplet from the nozzle nx at a right angle. . Note that the light beams 31a and 31b may be irradiated on different planes as long as they cross each other on the flight path of the ink droplets when observed from the nozzle that ejects the ink droplets. Further, as long as at least the intersecting angle can be specified, the angle at which the light beams 31a and 31b intersect may not be a right angle.

  Scattered light generated when the light beams 31a and 31b collide with ink droplets are received by the two light receiving elements 103a and 103b, respectively. The light receiving elements 103a and 103 are arranged at positions outside the beam diameters of the light beams 31a and 31b, respectively. For example, the light receiving elements 103a and 103b are disposed as offset as possible near the center of the optical axis at positions where the light receiving surfaces do not overlap with the beam diameters of the light beams 31a and 31b. Thereby, efficient detection becomes possible.

  FIG. 4 shows an enlarged view of the vicinity of the intersection of the light beams. 5 and 6 are diagrams showing intensity distributions of light beams emitted from the light emitting elements 30a and 30b, respectively. As shown in FIGS. 5 and 6, hereinafter, it is assumed that the intensity distribution of the light beams 31a and 31b is a Gaussian distribution. 5 and 6 correspond to positions a to i in FIG. 4, respectively.

  A position e in FIG. 4 represents a position through which an ink droplet passes when ejected normally. As shown in FIGS. 5 and 6, the light beams 31a and 31b have an intensity distribution in which the light intensity decreases with increasing distance from the optical axis. In the present embodiment, the light beams 31a and 31b are irradiated so that the ink droplets land within a predetermined gradient portion (specific gradient portion) where the intensity distribution is reduced. In the example of FIG. 4, the ink droplets land in a region 401 including at least the positions a to i. When evaluating the nozzle nx, the nozzle nx is adjusted to a position corresponding to the position e.

  FIG. 5 shows positions on the optical axis of the light beam 31a, the approximate center between the optical axis and the outer peripheral portion, and positions a, d, g, positions b, e, h, and positions c, f, It shows that the voltage values output from the light receiving element 103a when the ink droplet passes through i are V1, V2, and V3, respectively.

  Similarly, FIG. 6 shows positions i, h, g, positions f, e, d, and positions c existing on the optical axis of the light beam 31b, the approximate center between the optical axis and the outer peripheral portion, and the outer peripheral portion, respectively. , B, a indicate that the voltage values output from the light receiving element 103b when the ink droplets pass through are V1, V2, and V3, respectively.

  Next, a description will be given of a method in which the detection unit 104 detects the direction of bending (deviation) of the flight path of ink droplets and the distance of the bending. FIG. 7 is a diagram illustrating an output example of the light receiving elements 103a and 103b when the ink droplet passes through each of the positions a to i in FIG. In addition, the horizontal axis of each graph of FIG. 7 represents time.

  When the light passes through the position e in FIG. 4, the light receiving elements 103a and 103b output voltage values as shown in FIG. 7E, respectively. As shown in FIG. 7E, since the outputs of the light receiving elements 103a and 103b are both V2, the detection unit 104 can determine that the ink droplet has been ejected normally. When the ink droplet passes a point other than the position e, the detection unit 104 uses, for example, a voltage value output from each of the light receiving elements 103a and 103b as a reference value of the voltage value when the ink droplet is normally ejected (see FIG. 7 (e)), the position through which the ink droplet has passed is shifted in the direction of the optical axis side or the outer peripheral side of each light beam, and the amount of shift (distance). Can be specified. From these directions and distances obtained for the respective light beams 31a and 31b, the detection unit 104 can specify the bending direction and the bending distance of the flight path of the ink droplet with respect to the position e.

  4 to 7 show examples in which the positions corresponding to the voltage values output from the light receiving elements 103a and 103b correspond to nine points a to i, the correspondence between the voltage values and the coordinate points is shown. Further, the detection accuracy of the direction of the bend and the distance of the bend can be improved by taking it finer.

  As described above, in the liquid discharge failure detecting device according to the first embodiment, the liquid beam is limited to a region where the light beams emitted from the plurality of light emitting elements intersect and the specific gradient portions of the light beams overlap each other. By dropping the droplet, the output signal of the light receiving element can be changed according to the landing position of the droplet. Since the combination of the plurality of output signals for each light beam has a one-to-one relationship with the landing position of the droplet, it is possible to specify the direction and distance of the droplet bending.

(Second Embodiment)
The liquid discharge failure detection device of the second embodiment detects an ink droplet discharge failure using two light emitting elements and one light receiving element.

  FIG. 8 is a block diagram illustrating an example of a functional configuration of the inkjet printer 200 according to the second embodiment. The ink jet printer 200 according to the second embodiment mainly includes a head 16, an ejection control unit 101, a light emission control unit 102, a light emitting element 230, a light receiving element 203, and a detection unit 204. .

  In the second embodiment, the functions of the light emitting element 230, the light receiving element 203, and the detecting unit 204 are different from those of the first embodiment. Other configurations and functions are the same as those in FIG. 2 which is a block diagram showing the configuration of the ink jet printer 100 according to the first embodiment, and thus the same reference numerals are given and description thereof is omitted here.

  The light emitting element 230 includes a plurality of light emitting elements 230a and 230b as in the first embodiment, except that the beam diameters of the light beams emitted from the light emitting elements 230a and 230b are different from each other. Different from the first embodiment.

  The light receiving element 203 is different from the light receiving element 103 of the first embodiment in that the light receiving element 203 includes one element in the present embodiment. The light receiving element 203 receives both scattered light generated when the light beams emitted from the light emitting elements 230a and 230b collide with the ink droplets.

  The detection unit 204 separates the scattered light signal corresponding to the light beam emitted from each light emitting element 230a, 230b from the output signal output from the light receiving element 203, and detects an ejection failure of the ink droplet from the separated signal. To do. Details of the ejection failure detection processing by the detection unit 204 will be described later.

  Next, the positional relationship between the plurality of light emitting elements 230 and one light receiving element 203 will be described. FIG. 9 is a diagram illustrating an example of a positional relationship between the plurality of light emitting elements 230 and one light receiving element 203 observed from the ejection direction of the nozzle nx.

  The positional relationship between the light emitting elements 230a and 230b is the same as that in FIG. 3 showing the positional relationship in the first embodiment. In this embodiment, the light receiving element 203 is installed in the vicinity of the intersection of the light beams. As a result, the single light receiving element 203 can receive the scattered light generated when the plurality of light beams 231a and 231b collide with the ink droplets.

  FIG. 10 shows an enlarged view of the vicinity of the intersection of the light beams. Note that the intensity distributions of the light beams 231a and 231b in the second embodiment are the same as those in FIGS. 5 and 6 showing the intensity distributions of the light beams 31a and 31b in the first embodiment, respectively, and are therefore omitted.

  As shown in FIG. 10, in the present embodiment, the light emitting elements 230a and 230b have a light beam length (width) (RW1, RW2) and a length in the ink droplet ejection direction (high) as observed from the nozzle. E) Irradiate light beams 231a and 231b with different (RH1, RH2). The width of the light beam may be the same as long as at least the length (diameter) in the ejection direction is different.

  Thereby, the periods (frequency components) of the output signals obtained when the light receiving element 203 individually receives the scattered light corresponding to the light beams 231a and 231b can be made different from each other. FIG. 11 is a diagram illustrating a state in which a signal corresponding to scattered light with respect to each of the light beams 231a and 231b is separated from an output signal of one light receiving element 203. FIG.

  As shown in the upper left graph of FIG. 11, the output signal obtained when the ink droplet passes the position e with respect to the light beam 231 a emitted from the light emitting element 230 a with the light emitting element 230 b off is W <b> 1. As shown in the lower left graph of FIG. 11, the output signal obtained when the ink droplet passes through the position e with respect to the light beam 231b emitted from the light emitting element 230b with the light emitting element 230a turned off is W2. Become. As described above, in the present embodiment, output signals having different periods (frequency components) can be obtained for the light beams irradiated by the plurality of light emitting elements 230.

  With respect to the light beams 231a and 231b emitted by illuminating both the light emitting element 230a and the light emitting element 230b, the output signal W12 obtained when the ink droplet passes the position e is an output signal W1 and an output signal W2. It becomes the sum (graph in the center of FIG. 11).

  The detection unit 204 separates the output signal W12 into two signals W1 'and W2' using the bandpass filter 1 (BPF1) and the bandpass filter 2 (BPF2). BPF1 and BPF2 are configured to pass the frequencies of output signals W1 and W2, respectively.

  FIG. 12 is a diagram illustrating an example of the frequency spectrum of the output signals W1 and W2. In the present embodiment, the light emitting element 230 emits a light beam whose beam diameter is adjusted so that the frequency spectra WS1 and WS2 of the output signals W1 and W2 do not interfere with each other.

  As a result, the output signals W1 'and W2' taken out by BPF1 and BPF2 are equivalent to the output signals W1 and W2. That is, the detection unit 204 uses the output signals W1 ′ and W2 ′ after separation as output signals representing the light intensities of scattered light corresponding to the light beams 231a and 231b, respectively, by the same method as in the first embodiment. Ink droplet ejection failure can be detected. In other words, the detection unit 204 identifies the position through which the ink droplet has passed by associating each point from position a to position i in FIG. 10 with the amplitude value of the output signal after filter separation when passing through each point. it can.

  As described above, in the liquid ejection failure detection device according to the second embodiment, the diameters of the ejection directions of the ink droplets of the light beams emitted from the plurality of light emitting elements are mutually changed. This makes it possible to change the period (frequency component) of the output signal of the light receiving element when the ink droplet passes through each light beam. One light receiving element installed near the intersection of light beams emitted from a plurality of light emitting elements outputs the sum of output signals of scattered light when ink droplets pass through the plurality of light beams emitted from the plurality of light emitting elements. Since the frequency components of output signals corresponding to a plurality of light beams are different, they can be separated and extracted by a filter. Since the amplitude value of the output signal after separation by the filter is equivalent to the signal obtained in the first embodiment, it is possible to detect an ejection failure of the ink droplet by the same method as in the first embodiment. In the second embodiment, since it is not necessary to provide a light receiving element for each light beam, the configuration can be further simplified and the cost can be reduced.

(Modification)
In each of the above-described embodiments, if an ink droplet is ejected outside the region where the specific gradient portion of the light beam overlaps, there may be a case where ejection failure cannot be determined normally. For example, when an ink droplet passes near a position that is symmetrical to the position e with respect to the optical axis of the light beam 31a in FIG. 4, an output signal equivalent to the position e is obtained, and it is erroneously determined that the ink has been ejected normally. there's a possibility that.

  Therefore, a mask (blocking member) may be provided that blocks the flight path of ink droplets before they collide with a light beam so that the ink droplets do not pass outside a desired region. FIG. 13 is a view showing a modified example provided with such a mask 301. By providing such a mask 301, it is possible to prevent an output signal from ink droplets ejected outside the range of the region where the light beams intersect with each other from being output.

  FIG. 13 shows an example in which the ink droplet is further charged, the mask 301 is grounded to the ground 302, and the detection unit 104 (detection unit 204) detects the current flowing through the mask 301. .

  Simply providing the mask 301 makes it impossible to distinguish whether ink droplets were not ejected or whether ink droplets were ejected but the ink droplets bent significantly and went out of range. This distinction is possible if the current is detected. That is, the detection unit 104 (detection unit 204) detects that an ink droplet is bent and discharged out of the range when a current generated when an ink droplet having a charge collides with the mask 301 is detected.

DESCRIPTION OF SYMBOLS 10 Case 11, 12 Side plate 13 Guide shaft 14 Guide plate 15 Carriage 16y, 16c, 16m, 16b Inkjet head 17 Bottom plate 18 Single recovery device 20 Liquid discharge failure detection device 22 Platen 23 Paper 24 Paper feed table 25 Transport roller 26 Drive device 30, 230 Light emitting element 100, 200 Inkjet printer 101 Discharge control unit 102 Light emission control unit 103 Light receiving element 104 Detection unit 203 Light receiving element 204 Detection unit 301 Mask 302 Ground

Claims (7)

Light emission in which light intensity decreases outward from the optical axis, and a portion where the light intensity decreases when observing from a nozzle that discharges a droplet emits a plurality of light beams that intersect each other on the flight path of the droplet Means,
A light receiving means for receiving scattered light generated when a plurality of the light beams collide with the droplet;
Detecting means for detecting defective ejection of the droplet based on the light intensity of the scattered light;
A liquid discharge defect detection device comprising: The light emitting means irradiates the light beam that passes through the substantial center of a portion where the light intensity of the light beam decreases when the liquid droplet is ejected normally,
The detection means includes a predetermined reference value representing the light intensity of the scattered light received when the light beam passes through the approximate center, and the light intensity of the scattered light received by the light receiving means. And detecting the direction and distance of the deviation of the flight path based on the comparison result,
The liquid discharge defect detection device according to claim 1. The light emitting means irradiates a plurality of the light beams having different lengths in the discharge direction of the droplets,
The light receiving means outputs an output signal corresponding to the light intensity of the scattered light generated when a plurality of the light beams collide with the droplet,
The detection means separates the output signal into a plurality of signals representing the light intensities of the plurality of light beams using a filter, and compares the reference value with each of the light intensities represented by the separated signals, Detecting the direction and distance of the deviation of the flight path based on the comparison result;
The liquid discharge defect detection device according to claim 2. A plurality of the light receiving means are provided corresponding to each of the plurality of light beams,
Each of the plurality of light receiving means receives the scattered light generated when the corresponding light beam collides with the droplet,
The detection means compares the reference value with each of the light intensities of the plurality of scattered lights received by the plurality of light receiving means, and detects the direction and distance of the flight path deviation based on the comparison result. To do,
The liquid discharge defect detection device according to claim 2. Further comprising a blocking member that blocks a flight path of the droplets ejected outside a region where a plurality of the light beams intersect before the collision with the plurality of the light beams;
The liquid discharge defect detection device according to claim 1. The detection means further detects a current generated when the droplet having electric charges collides with the blocking member, and detects that a discharge failure of the droplet has occurred when the current is detected. thing,
The liquid discharge defect detection device according to claim 5.   An ink jet recording apparatus comprising the liquid ejection defect detection device according to claim 1.

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