JP2000043287A - Inkjet printing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer having a means for detecting the residual quantity of ink correctly. SOLUTION: Two optically reflective parts 4, 5 having different reflective surfaces are disposed in an ink tank body 1. Two optical sensors corresponding to the optically reflective parts 4, 5 are disposed on the bottom of the body. Residual quantity of ink is detected by detecting the level of ink using the optically reflective parts 4, 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printing apparatus which performs printing by discharging ink from a discharge port of a recording head.

[0002]

2. Description of the Related Art In an ink jet printing apparatus which performs printing by discharging ink from a discharge port of a recording head, printing is impossible if ink is exhausted due to its structure. Therefore, an ink remaining amount detecting means for knowing in advance whether printing is possible is often provided. In particular, in the case of a color ink jet printing apparatus having a plurality of inks, if even one color runs out of ink, not only can a correct print result be obtained, but also other ink that does not run out of ink can be wasted. It could be connected. For this reason, it is required to provide more accurate ink remaining amount detecting means. As a conventional technique for detecting the remaining amount of ink, there is a dot counting method for measuring ink droplets ejected from a recording head. This method measures the total number of ink droplets ejected based on print data and the number of ink droplets consumed in the recovery processing, and estimates the remaining amount of ink from the consumed ink amount. In the case of this method, although the ink remaining amount can be managed finely, the ink remaining amount is correctly set when the ink tank is replaced with an ink tank in use to clear the dot count of the ink droplet measured when replacing the ink tank. There was a problem that it could not be detected.

On the other hand, as a means for detecting the remaining amount of ink, there is a method using an optical sensor as disclosed in Japanese Patent Application Laid-Open No. 6-328717. This is a method in which a transparent member is used for a flow path for supplying ink from an ink tank to a recording head unit, and the flow of ink is detected by an optical sensor to determine whether or not ink is remaining. In this method, even if the ink tank is replaced during use, it is possible to correctly determine that the ink has run out. However, the remaining ink amount cannot be detected finely, and there is a possibility that the ink may run out during printing.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been developed to provide an ink jet printing apparatus having a means for correctly detecting the remaining amount of ink without being affected by ink tank replacement or the like. To provide.

[0005]

According to the present invention, there is provided an ink jet printing apparatus for performing printing by discharging ink from a discharge port of a recording head, wherein an ink tank portion for storing ink is formed by a light transmitting member. It has a plurality of optical reflectors having different shapes, and has a plurality of optical sensors that form a pair with the optical reflector, and the optical sensor includes a light emitting unit that irradiates light to the pair of optical reflectors and an optical sensor. And light receiving means for receiving the reflected light, and means for detecting the remaining amount of ink based on the light receiving state.

Alternatively, in an ink jet printing apparatus for performing printing by discharging ink from a discharge port of a recording head, an ink tank portion for storing ink has an optical reflection portion formed by a light transmissive member. Having an optical sensor consisting of a light emitting unit for irradiating the unit with light and a light receiving unit for reflected light of the optical reflecting unit, and moving one of the light receiving unit or the irradiation unit of the ink tank unit and the optical sensor,
A movement control unit that enables the state of the optical reflection unit to be detected by the optical sensor; and the remaining amount of ink is detected from the position information of the movement control unit and the detection state of the optical sensor. .

Further, there is provided an ink droplet measuring means for measuring ink droplets ejected from an ejection port of the recording head, and an ink remaining amount storing an ink remaining amount coefficient corresponding to a plurality of positional information of the movement control section. A coefficient storage unit, wherein a coefficient in the remaining ink coefficient storage unit is selected from the position information of the movement control unit and the detection state of the optical sensor, and the ink droplet measuring unit measures the ink droplet based on the selected coefficient. It is also characterized by detecting the remaining amount of ink.

According to the above configuration, the remaining amount of ink can be accurately detected by detecting the state of the plurality of optical reflection portions added to the ink tank portion by the optical sensor. Alternatively, by moving the ink tank unit and the optical sensor, it is possible to detect the remaining ink amount more finely.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic perspective view showing the overall configuration of an embodiment of an ink jet printing apparatus according to the present invention. In FIG. 1, reference numeral 130 denotes a carriage on which two ink jet heads and two ink cartridges can be mounted. Carriage 130
Are slidably supported by guide rails 132 and 133 extending at both ends of the chassis 131. A drive belt 134 for transmitting drive from a drive motor (not shown) is provided on the carriage 130.
And a flexible cable 135 for transmitting an image signal to the head 10 to be mounted. Thereby, printing can be performed by ejecting ink from each ink jet head 10 to, for example, recording paper as a recording medium.

At a home position HP provided at one end of the movement range of the carriage, a suction or protection cap (capping means) 136 is provided for the purpose of recovering the ejection of the ink jet head 10 mounted on the carriage 130. The space between the cap 136 and the head unit is set to a negative pressure by a pump (pump means) (not shown), or the head is discharged by idle discharge, or an ink outlet (nozzle) communicating with the discharge port of the head unit. C) can be positively eliminated. Although not shown, the cap 136 is provided with an ink tube which communicates with the inside of the cap 136 and guides the ink discharged from the head to a predetermined portion. On the other hand, a light-emitting unit 13 and a light-receiving unit 14 are provided on the other end of the moving range of the carriage 130. When the carriage 130 passes through this portion, it is possible to detect a non-discharge or the like.

In the present embodiment, an ink tank having the structure shown in FIGS. 2 and 3 will be described as an ink tank that can be suitably used in the ink jet printing apparatus having such a configuration.

FIG. 2 is a perspective view of the ink tank main body used in the first embodiment of the ink jet printing apparatus of the present invention, and FIG. 3 is a sectional view showing the relationship between the ink tank main body and the optical sensor. In the figure, reference numeral 1 denotes an ink tank main body. Reference numeral 2 denotes a supply port for sending ink to the recording head unit;
Denotes a recording head unit. Reference numeral 4 denotes a first optical reflecting portion formed of a light transmitting member made of a known material such as acrylic, and reference numeral 5 denotes a first optical reflecting portion 4 having a different shape from that of the first optical reflecting portion 4 and lower than the reflecting surface of the first optical reflecting portion 4. This is a second optical reflection portion having a reflection surface at a position. Reference numeral 6 denotes a part of the ink jet printing apparatus main body. Reference numeral 7 denotes a light emitting unit of the first optical sensor, and reference numeral 8 denotes a light receiving unit of the first optical sensor that is paired with the light emitting unit 7. This first optical sensor has an optical reflection portion 4.
Pair with. The light emitting section 7 to the first optical reflecting section 4 in FIG.
An arrow reaching the light receiving section 8 indicates a light path of the first optical sensor. When the first optical reflecting section 4 is entirely covered with ink, the light receiving section 8 receives the light of the light emitting section 7 to reflect the light. On the other hand, when the optical reflection unit 4 is not covered with the ink, the first optical reflection unit 4
The light receiving section 8 does not receive the light. Reference numeral 9 denotes a light-emitting unit of the second optical sensor similar to the light-emitting unit 7, and reference numeral 10 denotes a light-receiving unit of the second optical sensor similar to the light-receiving unit 7 that is paired with the light-emitting unit 9. Light emitting unit 9 and light receiving unit 1
For 0, the second optical reflection part 5 is paired. FIG.
From the light emitting section 9 to the second optical reflecting section 5 and the light receiving section 10
The arrow leading to indicates the light path of the second optical sensor. Also in this case, unless the optical reflection section 5 is covered with ink, the light of the light emitting section 9 is not reflected, and the light receiving section 10 cannot receive the light. Reference numeral 11 denotes the ink in the ink tank 1, and reference numeral 11a denotes its liquid level.

In this embodiment, as can be seen from the liquid surface 11a, the first optical reflector 4 is in the ink 11, and the second optical reflector 5 has its reflective surface above the liquid surface 11a. . Therefore, the first optical sensor including the light emitting unit 7 and the light receiving unit 8 determines that there is no ink, and the second optical sensor including the light emitting unit 9 and the light receiving unit 10 determines that there is ink. This makes it possible to detect the state before the ink runs out. That is, the liquid level of the ink in the ink tank 1 is between the liquid level detection position by the first optical sensor and the liquid level detection position by the second optical sensor. Thereby, the remaining amount of ink in the ink tank 1 can be generally known. The remaining amount of ink can be used to determine how many shots can be ejected from a single shot, so if you count ink droplets afterwards, you can effectively use up the ink and accurately determine when to use up the ink. You can know.

The combination of the dot counting method and the optical detection means in the present embodiment will be further described.
When the number of dots is counted from the start of use of the ink in the ink tank 1, when the first optical sensor including the light emitting unit 7 and the light receiving unit 8 detects that there is no ink for the first time, the dot counting method is used. If the count number is corrected, it is possible to more finely detect the remaining ink amount. If the number of dots has not been counted since the start of use of the ink in the ink tank 1, the dot count is started when the first optical sensor detects "no ink" for the first time. By predicting the number of dots corresponding to the remaining amount of ink detected by one optical sensor, it is also possible to know the exact ink use-out time.

FIG. 4 is a flowchart of a detection process when the number of dots is counted by a dot counter as an ink droplet measuring means from the start of use of the ink in the ink tank 1. Referring to FIG. 4, first, use of the ink tank is started (step S1), and immediately after that, dot counting is started (step S2). If the first optical sensor detects "no ink" (step S3), and if the second optical sensor detects "ink present" (step S4) in the next step, the remaining amount of ink is determined. (Step S)
5).

By combining with the dot counting method as described above, the accuracy of the remaining ink amount detection according to the present embodiment can be improved.

When the above-mentioned dot counting method is used, an ink remaining coefficient storage unit for storing ink remaining coefficients corresponding to a plurality of optical reflecting units is provided, and a plurality of optical sensors are provided. By selecting the coefficient in the ink remaining amount coefficient storage unit based on the light receiving state and measuring the ink droplets by the ink droplet measuring means based on the selected coefficient, it is possible to know exactly when the remaining ink is used up. Can be.

(Embodiment 2) In the above embodiment, an example was shown in which two optical sensors were provided, and two optical reflection portions corresponding to these sensors were also provided. An example in which one sensor is provided and this one sensor is applied to two optical reflection units will be described with reference to FIGS.

FIG. 5 is a perspective view of an ink tank body showing the configuration of the second embodiment of the present invention, and FIG. 6 is a cross-sectional view showing the relationship between the ink tank body and an optical sensor. In the figure,
21 is an ink tank main body. Reference numeral 22 denotes a supply port for sending ink to the print head unit, and reference numeral 23 denotes a print head unit. First optical reflector 24, second optical reflector 25
Is an optical reflecting portion formed of a light transmitting member made of a known material such as acrylic, for example, and the second optical reflecting portion 25 is different in shape from the first optical reflecting portion 24 in the first optical reflecting portion. The reflective surface has a reflective surface at a position lower than the reflective surface. 26 is a part of the inkjet printing apparatus main body. Reference numeral 27 denotes a light emitting unit of the optical sensor, and reference numeral 28 denotes a light receiving unit of the optical sensor that is paired with the light emitting unit 27. 30
Indicates the ink in the ink tank 21, and 30a indicates the liquid level of the ink 30.

The ink tank 21 moves in the main scanning direction indicated by the arrow in FIG. 6 during printing. Along the main scanning direction, the light emitting unit 27 and the light receiving unit 28 of the optical sensor, the state of the first optical reflecting unit 24 and the state of the second optical reflecting unit 25 are set within the movable range of the ink tank 21. Place it where it can be detected. FIG. 6A shows a state where the state of the second optical reflection unit 25 is detected by the light emitting unit 27 and the light receiving unit 28 of the optical sensor. Arrows from the light emitting unit 27 to the second optical reflecting unit 25 and the light receiving unit 28 in the drawing indicate the path of light of the optical sensor. FIG. 6B shows a state in which the ink tank 21 is moved and the state of the optical reflection unit 24 is detected by the light emitting unit 27 and the light receiving unit 28 of the optical sensor. Arrows from the light emitting unit 27 to the optical reflecting unit 24 and the light receiving unit 28 in the drawing indicate the light path of the optical sensor. When the optical reflecting portions 24 and 25 are both covered with ink, the light emitting portion 2 reflects light.
7 is received by the light receiving unit 28. On the other hand, when not covered with the ink, the optical reflecting portions 24 and 25 are
7, the light receiving unit 28 does not receive the light.

In this embodiment, as can be seen from the liquid surface 31a, the second optical reflection portion 25 is in the ink 30,
The optical reflecting portion 24 has a reflecting surface above the liquid surface 31a. Therefore, in the optical sensor including the light emitting unit 27 and the light receiving unit 28, in the case of FIG. 6B, it is determined that there is no ink, and in the case of FIG. 6A, it is determined that there is ink. This makes it possible to detect the state before the ink runs out. The position of the ink tank 21 can be determined by, for example, a linear encoder or the like as to which of the optical reflecting units 24 and 25 is being detected. Further, if the number of optical reflecting portions having different heights is increased, it becomes possible to know the detection of the remaining amount of ink in more detail.

Here, the combination of the dot counting method and the optical detecting means in the present embodiment will be further described. In the case where the number of dots has been counted from the start of using the ink in the ink tank 21, the optical sensor is used. By correcting the count number of the dot count method at the time when the ink absence is detected for the first time, it is possible to more finely detect the remaining ink amount. If the number of dots has not been counted since the start of use of the ink in the ink tank 21,
When the above optical sensor first detects that there is no ink, it starts dot counting and predicts the number of dots corresponding to the remaining amount of ink detected by the optical sensor, so that it is possible to know the exact ink exhaustion time. it can.

FIG. 7 is a flowchart of a detection process when the number of dots is counted from the start of use of the ink in the ink tank 21. Referring to FIG. 7, first,
The use of the ink tank is started (step S11), and immediately after that, the dot count is started (step S12). Then, when the optical sensor detects “no ink” using the first optical reflection unit 24 (step S13),
When the optical sensor detects “ink present” using the second optical reflection unit 25 in the next stage (Step S14)
Next, the dot count is corrected based on the remaining amount of ink (step S15).

By combining this with the dot counting method, the accuracy of the remaining ink amount detection according to the present embodiment can be improved.

(Embodiment 3) The feature of this embodiment is that the light emitting portion of the optical sensor can be reciprocated vertically, the light receiving portion is fixed to the bottom of the device, and the optical reflecting portion on the ink tank side has a stroke. It has a long slope.

FIG. 8 is a perspective view of an ink tank main body showing the configuration of the third embodiment of the present invention, and FIGS. 9A and 9B are cross-sectional views showing the relationship between the ink tank main body and an optical sensor. is there. In the figure, reference numeral 41 denotes an ink tank main body. 42 is a supply port for sending ink to the recording head unit,
43 is a recording head unit. Reference numeral 44 denotes an optical reflecting portion formed of a light transmitting member made of a known material such as acrylic. 45 is a part of the inkjet printing apparatus main body. 46 is a light emitting unit of the optical sensor,
Reference numeral 47 denotes a light receiving unit of the optical sensor that is paired with the light emitting unit 46. Reference numeral 50 denotes ink in the ink tank 41;
a is the liquid level of the ink 50. Arrows from the light emitting unit 46 to the optical reflecting unit 44 and the light receiving unit 47 in FIGS. 9A and 9B indicate the paths of light of the optical sensor.

During printing, the ink tank 41 moves in the main scanning direction (horizontal direction) indicated by the arrow in FIG. The light emitting unit 46
While irradiating light in the main scanning direction, the light can be reciprocated in the vertical direction within a range where the light can be irradiated to the optical reflecting portion 44 as shown in FIGS. 9A and 9B. Note that the light receiving section 47 is fixed. In accordance with the movement of the light emitting unit 46,
The light applied to the optical reflection unit 44 is correctly
The ink tank 41 is moved to a position where the ink can be transmitted. At this time, if the position of the optical reflecting section 44 irradiated by the light emitting section 46 is covered with ink, the light is reflected and reaches the light receiving section 47, and it is determined that there is ink. If not covered with ink, the light is transmitted through the optical reflection unit 44 and does not reach the light receiving unit 47, and it is determined that there is no ink. Therefore, in the case of this embodiment, there is no ink in FIG.
(B) has ink. The ink remaining amount is determined by the light emitting unit 46.
You can know by the position of.

Here, the combination of the dot counting method and the optical detection means in the present embodiment will be further described. In the case where the number of dots has been counted from the start of use of the ink in the ink tank 41, the optical sensor is used. By correcting the count number of the dot count method at the time when the ink absence is detected for the first time, it is possible to more finely detect the remaining ink amount. If the number of dots has not been counted since the start of use of the ink in the ink tank 41,
When the above optical sensor first detects that there is no ink, it starts dot counting and predicts the number of dots corresponding to the remaining amount of ink detected by the optical sensor, so that it is possible to know the exact ink exhaustion time. it can.

FIG. 10 is a flowchart of a detection process when the number of dots is counted from the start of use of the ink in the ink tank 41. Referring to FIG. 10, first, use of ink is started while moving the ink tank 41 in the main scanning direction (step S21), and immediately after that, dot counting is started (step S22). And
The light emitting unit 46 of the optical sensor is moved (Step S2
3). Next, the ink tank 41 is stopped at a position above the sensor light receiving section 47 (step S24). Next, when light is emitted from the sensor light emitting unit 46 to the optical reflecting unit 44 and the reflected light is directed to the sensor light receiving unit 47 to detect the remaining amount of ink, and when "no ink" is detected (step S25).
Next, the dot count is corrected based on the remaining amount of ink (step S26).

By combining with the dot counting method as described above, the accuracy of the remaining ink amount detection according to the present embodiment can be improved.

(Embodiment 4) This embodiment is characterized in that a plurality of light emitting portions of an optical sensor are provided.

FIGS. 11 (a) and 11 (b) are cross-sectional views showing the relationship between the ink tank body and the optical sensor according to the fourth embodiment of the present invention. Among the components of the present embodiment, the same components as those of the above-described third embodiment are denoted by the same reference numerals, and description of those portions is omitted.

Three light emitting portions 46a to 46c of the optical sensor
Is fixed to the wall of the device. The light receiving unit 47 is fixed to the bottom of the device as in the third embodiment. In the present embodiment, the ink tank 41 is moved so that light emitted from the light emitting units 46a to 46c to the optical reflecting unit 44 can be transmitted to the light receiving unit 47 correctly. At this time, as shown in FIG. 11A, the optical reflecting portion 44 irradiated by the light receiving portion 46a is used.
If the position is not covered with ink, the light is transmitted, does not reach the light receiving section 47, and it is determined that there is no ink. next,
When the ink tank 41 is moved to the position shown in FIG. 11B, since the position of the optical reflection unit 44 irradiated by the light emitting unit 46c is covered with ink, the light is reflected,
7, and it is determined that there is ink.

In short, in this embodiment, the ink level in the ink tank 41 can be searched and the remaining ink amount can be accurately detected by selectively using the plurality of light emitting units.

In the present embodiment, a plurality of light emitting units are used, but a long light emitting unit may be used. Further, it is possible to provide a plurality of light receiving sections, or it is possible to make the light receiving sections long.

In the present embodiment, a plurality of light-emitting units are fixed, but may be mounted on a mobile body. In that case, the ink level can be searched more quickly and the remaining ink amount can be accurately detected.

Further, the optical detecting means in this embodiment can be combined with the above-described dot counting method, and the combination is almost the same as in the previous embodiment, and the ink remaining amount can be accurately determined according to the flowchart shown in FIG. The amount can be detected.

In the above embodiments, various optical reflectors are provided to detect the remaining amount of ink. However, by applying a water-repellent treatment to the surface of such a reflector, the slope of the reflector is provided. It is possible to prevent an erroneous detection that may be caused by the attached layered ink beforehand. As the water repellent, a conventionally known water repellent can be used.

[0040]

As described above, according to the present invention,
By detecting the state of the optical reflector formed by a plurality of light-transmitting members with an optical sensor, or by moving the optical sensor and changing the state detection position of the optical reflector, more fine-grained It is possible to detect the remaining amount of ink.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing the overall configuration of an inkjet printing apparatus according to the present invention.

FIG. 2 is a perspective view of the ink tank body according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a relationship between an ink tank and an optical sensor according to the first embodiment of the present invention.

FIG. 4 is a flowchart of a detection process according to the first embodiment of the present invention.

FIG. 5 is a perspective view of an ink tank body according to a second embodiment of the present invention.

FIGS. 6A and 6B are cross-sectional views illustrating a relationship between an ink tank and an optical sensor according to a second embodiment of the present invention.

FIG. 7 is a flowchart of a detection process according to the second embodiment of the present invention.

FIG. 8 is a perspective view of an ink tank body according to a third embodiment of the present invention.

FIGS. 9A and 9B are cross-sectional views illustrating a relationship between an ink tank and an optical sensor according to a third embodiment of the present invention.

FIG. 10 is a flowchart of a detection process according to the third embodiment of the present invention.

FIG. 11 is a cross-sectional view illustrating a relationship between an ink tank and an optical sensor according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1,21,41 Ink tank 2,22,42 Ink supply port 3,23,43 Recording head 4,5,24,25,44 Optical reflector 6,26,45 Part of printer body 7,9 , 27, 46 Light emitting unit 8, 10, 28, 47 Light receiving unit 11, 30, 50 Ink 11a, 30a, 50a Ink liquid level

Claims (9)

[Claims] 1. An ink jet printing apparatus which performs printing by discharging ink from a discharge port of a recording head, wherein a plurality of optical reflection members formed of a light transmitting member and having different shapes are formed in an ink tank portion for storing the ink. Having a plurality of optical sensors that are paired with the plurality of optical reflection units, the plurality of optical sensors are a light emitting unit that emits light to the plurality of optical reflection units that are a pair. An ink-jet printing apparatus, comprising: a light-receiving unit that receives light reflected by the plurality of optical reflection units as a pair, and detects a remaining amount of ink based on a light-receiving state of the plurality of optical sensors. 2. The apparatus according to claim 1, further comprising: an ink droplet measuring unit configured to measure an ink droplet ejected from an ejection port of the recording head, wherein an ink remaining amount coefficient corresponding to the plurality of optical reflection units is stored. A coefficient coefficient storage unit, and selects a coefficient in the ink remaining amount coefficient storage unit based on a light receiving state of the plurality of optical sensors, and the ink droplet measuring unit determines an ink droplet based on the selected coefficient. 2. The ink jet printing apparatus according to claim 1, wherein the remaining amount of the ink is detected by measuring. 3. The ink-jet printing apparatus according to claim 1, wherein the plurality of optical reflection portions have reflection surfaces having different heights. 4. The ink-jet printing apparatus according to claim 1, wherein a water-repellent treatment is applied to the optical reflection portion. 5. An ink jet printing apparatus which performs printing by discharging ink from a discharge port of a recording head, comprising: an ink tank portion storing the ink, an optical reflection portion formed by a light transmitting member; An optical sensor including a light emitting unit that irradiates the optical reflecting unit with light and a light receiving unit that receives light reflected by the optical reflecting unit; the ink tank unit and a light receiving unit or an irradiating unit of the optical sensor Has a movement control unit that enables the optical sensor to detect the state of the optical reflection unit, and detects the remaining amount of ink from the position information of the movement control unit and the detection state of the optical sensor. An ink jet printing apparatus characterized by the above-mentioned. 6. The ink tank section has a plurality of optical reflection sections having different shapes, the movement control section moves only the ink tank section, and the plurality of optical reflection sections are moved by the optical sensor. 6. The ink jet printing apparatus according to claim 5, wherein a state of the ink is detected, and a remaining amount of ink is detected from position information of the movement control unit and a detection state of the optical sensor. 7. The ink jet printing apparatus according to claim 5, wherein the plurality of optical reflection portions have reflection surfaces having different heights. 8. An ink which has an ink droplet measuring means for measuring an ink droplet ejected from an ejection port of the recording head, and stores an ink remaining amount coefficient corresponding to a plurality of pieces of position information of the movement control unit. A remaining coefficient storage unit, for selecting a coefficient in the ink remaining coefficient storage unit from position information of the movement control unit and a detection state of the optical sensor, and determining the ink droplet measuring means based on the selected coefficient; Detecting the remaining amount of ink by measuring ink droplets.
An inkjet printing apparatus according to any one of the above items. 9. The ink-jet printing apparatus according to claim 5, wherein a water-repellent treatment is applied to the optical reflection portion.