Image recording apparatus having density correction of plural recording elements

An image recording apparatus for recording an image by using a plurality of recording elements which are driven an accordance with an image signal includes a first correction unit for correcting driving conditions of the recording element, and a second correction unit for correcting a level of the image signal, wherein a variation in the recording elements is corrected by a combination of the first and second correction units. A driving voltage or a width of drive pulse which is applied to each recording element is controlled as a driving condition, thereby making uniform an uneven image density.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an image recording apparatus for recording an 
image by using a plurality of recording elements. 
2. Related Background Art 
Hitherto, in such a kind of apparatus, a multi recording head in which a 
plurality of recording elements are arranged in one recording head to 
reduce the recording time as short as possible is mainly used as a 
recording head for use in a printer, a facsimile apparatus, a copying 
apparatus, or the like. Generally, however, in the case where the 
recording elements of one multi recording head have been driven under the 
same driving condition from a viewpoint of a manufacturing problem, an 
uneven image density occurs in a recording image due to a variation in 
recording characteristics by the recording elements, so that a recording 
image of good quality is not achieved. Therefore, an apparatus to prevent 
the above uneven image density has been proposed. The above apparatus has: 
memory means for printing a test pattern of a certain predetermined 
density for a recording head in the case where recording characteristics 
of recording elements are uneven and for calculating and storing data 
according to recording characteristics of the recording elements; and 
means for correcting input image data on the basis of the memory means and 
the stored data. 
For instance, a multinozzle head of the ink jet type has a multihead 61 
which is constructed by arranging recording elements 62 in a line as shown 
in FIG. 6A. In the case where input signals to the image recording 
elements are set to be uniform as shown in FIG. 6B, an uneven image 
density as shown in FIG. 6C occurs as an example. In this case, the input 
signals are corrected as shown in FIG. 6D, a large input signal is given 
to the image recording elements in the portion of low densities, and a 
small input signal is given to the image recording elements in the portion 
of high densities. In the case of a recording system which can modulate a 
dot diameter or a dot density, a diameter of dot which is recorded by each 
image recording element is modulated in accordance with the input signal. 
For instance, in the ink jet recording system of the piezoelectric type, a 
driving voltage or a pulse width which is applied to each piezoelectric 
element, while in the case of the thermal copy transfer recording system, 
a driving voltage or a pulse width which is applied to each heating 
element is changed in accordance with the input signal, thereby making 
uniform the dot diameters or dot densities by the recording elements. Thus 
a density distribution is made uniform as shown in FIG. 6E. On the other 
hand, in the case where it is impossible or difficult to modulate the dot 
diameter or dot density, the number of dots is modulated in accordance 
with the input signal. A larger number of dots are printed by the image 
recording elements in the low density portion and a small number of dots 
are printed by the image recording elements in the high density portion, 
so that a density distribution is made uniform as shown in FIG. 6E. 
A correction amount in the above cases is obtained, for instance, by the 
following method. 
The case of correcting an uneven image density of a multihead comprising 
256 nozzles will now be described as an example. FIG. 7 shows an uneven 
image density distribution which occurs when dots have been printed by a 
certain uniform image signal S. First, a mean density OD of the head is 
obtained. Then, densities OD.sub.1 to OD.sub.256 of the portions 
corresponding to the nozzles are measured. Subsequently, .DELTA.OD.sub.n 
=OD-OD.sub.n (n=1 to 256) are obtained. Now, assuming that the relation 
between the value of the image signal and the output density, that is, the 
tone characteristic is linear as shown in FIG. 8, it is proper to correct 
the image signal by only .DELTA.S in order to correct the density by only 
.DELTA.OD.sub.n. For this purpose, it is sufficient to execute a table 
conversion as shown in FIG. 9 to the image signal. In FIG. 9, reference 
numeral 301 denotes a straight line of an inclination of 1.0. An input 
signal is generated without being converted. On the other hand, reference 
numeral 302 denotes a straight line of an inclination of (S-.DELTA.S)/S 
and when an input signal of S is given, a signal of S-.DELTA.S is 
generated. 
Therefore, if the head is driven after executing a table conversion as 
shown by the straight line 302 in FIG. 9 for the image signal 
corresponding to the n-th nozzle, a density of the portion which is 
printed by the n-th nozzle is equal to OD. By performing such a process 
for all of the nozzles, the uneven image density is corrected and a 
uniform image is derived. That is, the uneven image density can be 
corrected by previously obtaining data indicating which table conversion 
should be optimally performed to the image signal corresponding to which 
nozzle. 
However, in the above conventional example, actually, the tone 
characteristics of all of the nozzles are not expressed by the straight 
lines as shown in FIG. 8. Drawbacks in the case where the tone 
characteristics of the nozzles differ will now be explained. The case of 
correcting a difference of the image densities between two nozzles will 
now be considered for simplicity of explanation. 
In FIG. 10, reference numeral 401 denotes a tone characteristic of a 
nozzle-1 and 402 indicates a tone characteristic of a nozzle-2. Since an 
ink discharge amount of the nozzle-2 is larger than that of the nozzle-1, 
the nozzle-2 has such a tone characteristic. In the case of correcting the 
density difference for the input signal S as mentioned above, the image 
signal for the nozzle-2 is increased by (S-.DELTA.S)/S times. Thus, the 
tone characteristic 402 is extended in the X direction by only 
S/(S-.DELTA.S) times. The extended tone characteristic 402 is as shown at 
402' in FIG. 11. 
Although the density difference for the input signal S has been corrected, 
density differences still remain in the other regions. To correct the 
density differences for all of the regions, it is necessary that all of 
the tone characteristics of the nozzles are expressed by straight lines. 
However, since the ink emission amounts of the nozzles actually differ, the 
tone characteristics of the nozzles also differ. 
Therefore, there is a drawback such that even if an uneven image density 
could be corrected at a certain print duty, uneven image densities remain 
at the other duties and it is very difficult to correct the uneven image 
densities for the whole region. 
The above drawback is not limited to the foregoing ink jet system. Even in 
the other systems such as thermal copy transfer system, LED printer, and 
the like, there is a variation of dot diameters which are printed by the 
heating elements and there is also a variation of tone characteristics. It 
is, therefore, also similarly very difficult to correct the uneven image 
densities. 
SUMMARY OF THE INVENTION 
The invention is made in consideration of the above drawbacks and it is an 
object of the invention to provide an improved image recording apparatus. 
Another object of the invention is to provide an image recording apparatus 
which can stably obtain a uniform image having excellent tone 
characteristics. 
Still another object of the invention is to provide an image recording 
apparatus which can obtain an image without an uneven image density even 
for any print duty. 
In order to achieve the above objects, there is provided an image recording 
apparatus for recording an image in accordance with an input image signal 
by driving a plurality of recording elements with a driving energy, each 
of the recording elements having a recording characteristics, comprising: 
first storing means for storing a first set of correction data for 
correcting the driving energy for the plurality of recording elements; 
second storing means for storing a second set of correction data for 
correcting a level of the image signal for the plurality of recording 
elements; driving means for driving the recording elements with the 
driving energies corrected in accordance with the first set of correction 
data; and correcting means for correcting the input image signals in 
accordance with the second set of correction data. Control means controls 
the driving means, the control means being operable in a first mode in 
which the driving means is caused to drive the recording elements with 
uniform driving energies to produce the recorded image from which data for 
the first set of correction data can be collected, and a second mode in 
which the driving means is caused to drive the recording elements in 
accordance with a uniform image signal and with drive energies corrected 
in accordance with the first set of correction data to produce a recorded 
image from which data for the second set of correction data can be 
collected, and a third mode in which the driving means is caused to drive 
the recording elements in accordance with the input image signal corrected 
in accordance with the second set of correction data and with drive 
energies corrected in accordance with the first set of correction data to 
produce a recorded image represented by the input signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Preferred embodiments according to the present invention will be described 
in detail hereinbelow with reference to the drawings. 
&lt;First embodiment&gt; 
FIG. 1 is a block diagram showing a circuit construction of a copying 
apparatus of the first embodiment. FIG. 3 is a side sectional view showing 
the copying apparatus of the embodiment. 
In FIG. 1, reference numeral 1 denotes a CCD for collecting light which has 
been irradiated to an original image and reflected therefrom, for 
photoelectrically converting the reflected lights into the electric 
signals, and for generating the electric signals. Reference numeral 2 
denotes a masking unit for converting color components of R (red), G 
(green), and B (blue) into C (cyan), M (magenta), Y (yellow), and K 
(black) components. Reference numeral 3 denotes a gamma (.gamma.) 
correction unit for correcting an uneven image density of image signals 
generated from the masking unit 2 and for converting the image signals 
into density signals having tones. Reference numeral 4 denotes an ED unit 
for binarizing the .gamma. corrected image signals by an error diffusion 
method; 5 a head driver to control the printing operations of heads 6 to 
9; and 6 to 9 the recording heads for printing the C, M, Y, and K 
components, respectively. 
Reference numeral 12 denotes a CPU to control the operation of the whole 
copying apparatus; 13 a ROM in which a control program, an error 
processing program, a program according to a flowchart of FIG. 2, and the 
like have been stored; 14 a RAM which is used as a work area of various 
programs; 10 a .gamma. correction data ROM in which .gamma. correction 
data to correct the input signals by the .gamma. correction unit 3 has 
been stored; and 11 a dot diameter correction data ROM in which correction 
data corresponding to dot diameters in the head driver 5 has been stored. 
In FIG. 3, reference numeral 31 denotes a recording head unit in which 
recording heads only for use of the respective colors of K, C, M, and Y 
are arranged in parallel in the conveying direction of a recording paper. 
Each of the recording heads is a full line head in which emission ports 
are arranged at a density of 400 dpi (dots per inch) in the direction 
(width direction) which is almost perpendicular to the conveying direction 
of the recording paper for a range corresponding to a length (297 mm) of 
short side of the recording paper of the A3 size. Reference numeral 32 
denotes a paper feed cassette; 33 a pickup roller which is rotated in the 
direction indicated by an arrow R; 34 a paper conveying belt; 35a to 35c 
paper feed rollers; 36 a discharge roller; 37 a cover of an image reading 
light source which is used for correction of an uneven image density; 38 a 
discharge tray; 39 a paper pressing roller to prevent a floating of the 
paper upon image reading; 40 a light source for reading; and 41 a sensor 
for reading. 
When an image recording command is generated, the pickup roller 33 is 
rotated in the R direction and the recording paper enclosed in the 
cassette 32 is picked up and conveyed by the pickup roller 33 onto the 
paper conveying belt 34. After that, a rotating roller 35 is rotated and 
the recording paper is conveyed in the direction indicated by an arrow E 
together with the paper conveying belt 34. At this time, the recording 
heads are driven, the image which has been read by a reader unit 50 is 
recorded onto the recording paper, and the recording paper is thereafter 
discharged onto the discharge tray 38 by the discharge roller 36. 
On the other hand, when an uneven image density correcting command is 
generated, the recording paper is fed out of the cassette 32 in a manner 
similar to the case of the image recording mentioned above. When the 
recording paper is conveyed by the conveying belt 34, a test pattern is 
formed onto the recording paper by the recording heads. After that, the 
recording paper on which the test pattern has been recorded is conveyed to 
a position of the sensor 41 to read an uneven image density. The test 
pattern formed on the recording paper is read by the reading sensor 41. An 
uneven image density correcting process is executed as will be explained 
hereinlater. 
A density correcting method of the first embodiment will now be described. 
In the first embodiment, dot diameter correction data is corrected every 
128 nozzles (as many as two IC.sub.s) which are simultaneously driven. The 
uneven image density correction data is provided for every nozzle. 
In the first embodiment, therefore, explanation will now be made as an 
example with respect to a copying apparatus using the ink jet system which 
can easily realize a plurality of nozzles and emits inks by using thermal 
energies. 
In the case of the ink jet system, it is difficult to largely modulate a 
dot diameter without changing a head shape. Therefore, a control by a dot 
print amount (the number of dots) is an effective means as means for 
correcting an uneven image density which is caused due to an unevenness of 
dot diameters. In the high density portion (particularly, paint printing 
portion of a print amount of 100%), however, a density of the printing 
portion corresponding to the recording element of a small dot diameter is 
smaller than densities of the other portions or a density of the high 
density portion needs to be reduced as a whole. That is, as also already 
described in the related background art, if data is generated at a density 
different from that of the test pattern upon correction of an uneven image 
density, tone characteristics of the image input signal when the original 
image has been read and of an image output signal are not always linear, 
so that a lack of correction of the uneven image density or an excessive 
correction of the uneven image density occurs. 
Therefore, before the uneven image density is corrected by controlling the 
number of dots, an energy which is applied to each recording element is 
modulated by a pulse width to thereby uniform the dot diameters. After 
that, the uneven image density is corrected by the half tone having a most 
conspicuous uneven image density. Due to this, a uniform output image is 
derived even at each tone. 
When performing such a correction, two kinds of data such as dot diameter 
correction data and uneven image density correction data are necessary. 
However, as a countermeasure for the above case, either one of or both of 
those correction data are corrected for every predetermined number of 
recording elements (or blocks of recording elements), so that the number 
of memories can be reduced. In such a case as well, a correcting 
capability which is equivalent to that in the case of correcting every 
recording element can be obtained in accordance with a proper combination 
due to the kinds of recording heads. 
The operation of the first embodiment will now be described. 
FIG. 2 is a flowchart for explaining the density correcting operation by 
the CPU 12 in the first embodiment. 
FIG. 5 is a diagram for explaining uneven image density correction curves 
in the first embodiment. The following explanation relates to one color of 
a recording apparatus which can perform a color output. 
First, the recording medium is fed out of the cassette 32 by the pickup 
roller 33. A fundamental pulse of 7 .mu.sec is applied to the recording 
head unit 31. A test pattern of a 50% half tone of every color is recorded 
onto the recording medium (step S1). The test pattern formed on the 
recording medium is read by the reading sensor 41 (step S2). A pulse 
waveform is calculated in a manner such that after the sensor 41 has read 
the uneven image density, a long pulse can be applied to the high density 
portion so as to increase the dot diameter and that a short pulse can be 
applied to the low density portion so as to reduce a dot diameter. A pulse 
waveform (pulse width) which is considered to be optimum is selected from 
curves as shown in FIG. 5 which have been stored in the dot diameter 
correction data ROM 11 and is set into the RAM 14 (step S3). In FIG. 5, 
reference numeral 201 denotes a curve showing the relation between the 
pulse of the nozzle having a large dot diameter and the dot diameter and 
202 indicates a curve showing the relation between the pulse of the nozzle 
of a small dot diameter and the dot diameter. 
A test pattern of the 50% half tone is then recorded onto another recording 
medium on the basis of the set dot diameter correction data in a manner 
similar to step S1 (step S4). An uneven image density is read in a manner 
similar to step S2 (step S5). An uneven image density correcting process 
by the ordinary .gamma. curve is now executed on the basis of the image 
which has been read. The calculated uneven image density amount is set as 
uneven image density correction data into the RAM 14 (step S6). A tone 
pattern is recorded onto the recording medium on the basis of the uneven 
image density correction data calculated in step S6. If evenness of the 
uneven image density cannot be confirmed in step S8, the processing 
routine is returned to step S4 and the correcting process by the .gamma. 
curve is repetitively executed. 
As described above, according to the first embodiment, since a uniform 
output image of good tone characteristics can be obtained, an image of 
good quality can be also derived from the conventional recording head 
which cannot be used because of a remarkable uneven image density. 
Further, a manufacturing yield can be improved and the head manufacturing 
costs can be reduced. 
In the above embodiment, both of the dot diameter correction and the uneven 
image density correction by the .gamma. curve have been executed by 
actually forming test images and by reading the densities thereof. 
However, it is also possible to previously store the dot diameter 
correction data into the ROM upon shipping from the factory or the like 
and to execute the uneven image density correction by the .gamma. curve by 
reading the densities of the test images. Explanation will be further made 
hereinbelow. 
To stably obtain an image of a good quality after the recording head was 
manufactured, it is necessary to measure a discharge critical voltage 
(hereinafter, referred to as V.sub.th) of each nozzle for the fundamental 
pulse and to decide a recording head driving voltage (hereinafter, 
referred to as V.sub.op) in accordance with V.sub.th. Therefore, the 
uneven image density correction in the first embodiment is performed and 
the ROM in which the uneven image density correction data has been stored 
and the recording head are together shipped and, after that, they are 
installed to the copying apparatus shown in FIG. 3. In the case of 
applying the first embodiment, upon shipping, the dot diameter correction 
data obtained in step S3 in FIG. 2 is previously stored into the dot 
diameter correction data ROM 11 as a memory device and the ROM 11 is 
shipped. The uneven image density correction data which has been read in 
the apparatus is stored into the RAM 14 as a memory device provided in the 
apparatus. The density signal which has been read from the original is 
converted into the output binary signal in accordance with the data by the 
RAM 14 mentioned above. Further, the output binary signal is energy (pulse 
waveform) corrected in accordance with the data by the dot diameter 
correction data ROM 11 and the resultant corrected signal is supplied to 
the recording head. With the above construction, it is possible to realize 
an apparatus which can also cope with a change in uneven image density due 
to a state change of the recording head without making the conventional 
procedure complicated. 
&lt;Second embodiment&gt; 
The second embodiment will now be described. 
The means for correcting an energy amount which is applied to each 
recording element is not always limited to the means for controlling a dot 
diameter as in the foregoing first embodiment. That is, the correcting 
means for the energy amount in the invention is not limited to the case of 
making correction data by reading the uneven image density but can be also 
applied to the case where the stabilization (realization of long life) of 
each of the recording elements provided in the recording head is 
considered. 
As described in the foregoing first embodiment, in the case of attaching 
the recording head unit 31 to the copying apparatus shown in FIG. 3, the 
proper driving voltage (V.sub.op) is determined from the emission critical 
voltage (V.sub.th) of the recording head. As already described in the 
conventional technique as well, this is because it is difficult to stably 
manufacture uniform recording heads in the same manner. 
FIG. 4 is a diagram for explaining the relations between the voltage and 
the pulse width for the recording element of a high V.sub.th and the 
recording element of a low V.sub.th in an ink jet multihead. In the 
diagram, reference numeral 101 denotes a curve showing the relation 
between the pulse and the voltage of the recording element of a high 
V.sub.th. Reference numeral 102 indicates a curve showing the relation 
between the pulse and the voltage of the recording element of a low 
V.sub.th. 
In general, when the recording elements are driven by a single pulse 
waveform of 7 .mu.sec, a variation of about 1V occurs in V.sub.th from 
FIG. 4. In the conventional technique, a value of V.sub.th is set to 23.6V 
in correspondence to the recording characteristic of low V.sub.th. For 
such V.sub.th, a value of V.sub.op is equal to 27.2V which is about 1.7 
times as high as V.sub.th. However, for the nozzle of high V.sub.th, the 
value of V.sub.op is about 1.12 times as high as the value of V.sub.th and 
a voltage which is applied to emit the ink decreases. ordinarily, in the 
ink jet head of the system which emits the ink by using a thermal energy 
as in the embodiment, a ratio (hereinafter, referred to as a k value) of 
V.sub.op /V.sub.th is equal to a numerical value which is proportional to 
an energy which is necessary to emit the ink. Therefore, in FIG. 4, if a 
wave form of a pulse width of 6.6 .mu.sec is applied to the recording 
element of low V.sub.th and a waveform of a pulse width of 7.5 .mu.sec is 
applied to the recording element of high V.sub.th and the value of 
V.sub.th is made uniform to 24V, every recording element can be driven 
with stable energy. Therefore, it is possible to prevent a situation such 
that an energy which is applied to only a certain recording element is too 
small (or too large). Even in the case of performing the above control, a 
dot diameter of the recording element having a characteristic of a 
relatively large dot diameter and a dot diameter of the recording element 
having a characteristic of a relatively small dot diameter are set to 
large dot diameters by the pulse widths as shown in FIG. 5. That is, since 
the dot diameter of the recording element of a high V.sub.th and a low k 
value (applied voltage) is also small, the pulse width modulation for the 
V.sub.th correction is also effective to an uneven image density. 
Although the above second embodiment has been described with respect to the 
case of correcting the energy amount by the pulse width, such a method has 
been used because it is possible to most easily control in the case of the 
multi nozzle head in which a plurality of heads are arranged. In the 
invention, only the pulse width has been made to correspond to the energy 
amount. For instance, however, it is also possible to control the k value 
(applied voltage) as mentioned above and to correct the dot diameter (or 
V.sub.th) and to correct the uneven image density by the dot number 
modulation. 
On the other hand, in order to make uniform a variation with respect to the 
recording characteristics (including the durability or the like) of the 
recording elements, the invention intends to comprise: the first 
correcting means for controlling an energy (pulse waveform) to be applied; 
and the second correcting means for making uniform the uneven image 
density upon recording by the image signal. The invention is not limited 
to only the ink jet system of the type which emits the ink by using a 
thermal energy as mentioned above but can be also applied to various kinds 
of systems such that a variation in recording element can be uniformed by 
correcting the applied energy amount and a variation in image can be 
modulated by correcting the image signal. Practically speaking, the 
invention can be also applied to the ink jet system of the piezoelectric 
type. In the case of the thermal recording system as well, a variation in 
resistance value in the head can be corrected by the first correcting 
means and an evenness of an image upon scanning or the like can be 
corrected by the second correcting means. It is also possible to correct 
the uneven image density by the first correcting means by an 
electrophotograph of the digital system (principle of the PWM) and, 
further, to use the second correcting means in the case where a correcting 
range is lacking. 
Although the embodiments have been described with respect to the recording 
apparatus using the recording head of the bubble jet system among the ink 
jet recording systems, as typical construction and principle, the 
fundamental principle disclosed in., for instance, the specifications of 
U.S. Pat. Nos. 4,723,129 and 4,740,796 is used. The above system can be 
applied to both of what are called on-demand type and continuous type 
systems. Particularly, in the case of the on-demand type, at least one 
drive signal which corresponds to recording information and causes a 
sudden temperature increase exceeding nucleate boiling is applied to an 
electrothermal converting element arranged in correspondence to a sheet or 
a liquid channel in which a liquid (ink) is held, thereby causing a 
thermal energy in the electrothermal converting element and causing 
nucleate boiling on a heat acting surface of the recording head, so that 
an air bubble can be formed in the liquid (ink) corresponding to the drive 
signal in a one-to-one corresponding relation. Therefore, the above method 
is effective. The liquid (ink) is emitted through a discharge opening by 
the growth and contraction of the air bubble, thereby forming at least one 
liquid droplet. By using a pulse-like signal as such a drive signal, the 
growth and contraction of the bubble are quickly properly performed. 
Therefore, particularly, the emission of the liquid (ink) having an 
excellent response speed can be accomplished and it is more preferable. 
The signals as disclosed in the specifications of U.S. Pat. Nos. 4,463,359 
and 4,345,262 are suitable as such a pulse-like drive signal. Further 
excellent recording can be performed by using the conditions disclosed in 
the specification of U.S. Pat. No. 4,313,124 of the invention regarding a 
temperature increasing rate of the heat acting surface. 
The construction of the recording head is not limited to the construction 
(linear liquid channels or right-angled liquid channels) of a combination 
comprising the emission port, liquid channel, and electrothermal 
converting element as disclosed in each of the above specifications but 
can also use the constructions in which heat acting portions are arranged 
in a bending region as disclosed in the specifications of U.S. Pat. Nos. 
4,558,333 and 4,459,600. In addition, it is also possible to use the 
construction disclosed in Japanese Laid-Open Patent Application No. 
59-123670 in which a slit common to a plurality of electrothermal 
converting elements is used as an emission port of the electrothermal 
converting element or the construction as disclosed in Japanese Laid-Open 
Patent Application No. 59-138461 in which an opening which absorbs a 
pressure wave of a thermal energy is made corresponding to the emission 
port. That is, even if the recording head has any construction, the 
recording can be certainly efficiently performed. 
Further, the invention can be also applied to the recording head of the 
full line type having a length corresponding to the maximum width of the 
recording medium which can be recorded by the recording apparatus as 
mentioned above. As such a recording head, it is possible to use a 
construction in which such a length is realized by a combination of a 
plurality of recording heads or a construction as a single recording head 
which is integratedly formed. Further, among the recording heads of the 
serial type, it is also possible to use a recording head of the 
exchangeable chip type in which by installing the apparatus main body, an 
electrical connection with the apparatus main body and the supply of the 
ink from the apparatus main body can be performed. 
By adding recovery means, spare auxiliary means, and the like for the 
recording head which are provided as components constructing the recording 
apparatus, the recording operation can be further stabilized. Therefore, 
such a construction is preferable. Practically speaking, by providing 
capping means for the recording head, cleaning means, pressurizing or 
attracting means, spare heating means comprising electrothermal converting 
elements or heating elements different therefrom or a combination thereof, 
and means for executing a spare emitting mode to perform an emission 
different from the emission for recording, the stable recording is 
effectively executed. 
On the other hand, with respect to the kinds and the number of recording 
heads which are installed as well, the invention is not limited to the 
case where only one recording head is provided in correspondence to a 
single color ink but can be also applied to the case where a plurality of 
recording heads are provided in correspondence to a plurality of inks of 
different recording colors or different densities. 
As described above, according to the invention, a uniform image having 
excellent tone characteristics can be stably obtained.