U.S. patent application number 09/773514 was filed with the patent office on 2002-08-08 for image forming apparatus with lamp burn-out detection.
This patent application is currently assigned to TOSHIBA TEC KABUSHIKI KAISHA. Invention is credited to Ozawa, Kazuyuki.
Application Number | 20020106218 09/773514 |
Document ID | / |
Family ID | 25098523 |
Filed Date | 2002-08-08 |
United States Patent
Application |
20020106218 |
Kind Code |
A1 |
Ozawa, Kazuyuki |
August 8, 2002 |
IMAGE FORMING APPARATUS WITH LAMP BURN-OUT DETECTION
Abstract
It is decided whether or not a light exposure lamp 5 burns out
by comparing a light receiving output of a CCD 10 involved when a
light exposing position of a light exposure lamp 5 corresponds to a
white color reference sheet 13 with an initially set value.
Inventors: |
Ozawa, Kazuyuki;
(Yokohama-shi, JP) |
Correspondence
Address: |
Foley & Lardner
Suite 500
3000 K Street, N.W.
Washington
DC
20007-5109
US
|
Assignee: |
TOSHIBA TEC KABUSHIKI
KAISHA
|
Family ID: |
25098523 |
Appl. No.: |
09/773514 |
Filed: |
February 2, 2001 |
Current U.S.
Class: |
399/220 ;
399/177 |
Current CPC
Class: |
H04N 1/00068 20130101;
H04N 1/00925 20130101; H04N 1/00055 20130101; H04N 1/00013
20130101; H04N 1/00002 20130101; H04N 1/00063 20130101; H04N
1/00031 20130101 |
Class at
Publication: |
399/220 ;
399/177 |
International
Class: |
G03G 015/04 |
Claims
What is claimed is:
1. An image forming apparatus comprising: a document glass on which
a document is placed; a light exposure lamp for exposing the
document glass with light; a color reference member for shading
correction which is provided at a non-document-placing area of the
document glass; moving means for moving the light exposure lamp
along the document glass; image signal outputting means for
receiving reflected light from the document glass under the light
exposure and movement of the light exposure lamp and outputting an
image signal corresponding to that receiving light amount; and
deciding means for deciding whether or not the light exposure lamp
burns out by comparing an output of the image signal outputting
means involved when a light exposure position of the light exposure
lamp corresponds to the color reference member with an initially
set value.
2. An apparatus according to claim 1, wherein the color reference
sheet is comprised of a black color reference sheet and white color
reference sheet, and the deciding means decides whether or not the
light exposure lamp burns out by comparing an output of the image
signal outputting means involved when the light exposure position
of the light exposure lamp corresponds to the white color reference
sheet with an initially set value.
3. An apparatus according to claim 1, further comprising printing
means for printing an image corresponding to the image signal
outputted from the image signal outputting means; and control means
for inhibiting printing by the printing means when the deciding
means decides that the light exposure lamp burns out.
4. An apparatus according to claim 1, further comprising notifying
means for, when the deciding means decides that the light exposure
lamp burns out, notifying this effect.
5. An image forming apparatus comprising: a document glass on which
a document is placed; an exposure lamp for exposing the document
glass with light; a color reference member for shading correction
which is provided at a non-document-placing area of the document
glass; moving means for moving the light exposure lamp from the
non-document-placing area toward a document placing area; image
signal outputting means for receiving reflected light from the
document glass under the light exposure and movement of the light
exposure lamp and outputting an image signal corresponding to that
light receiving amount; control means for retaining, as a reference
value for shading correction, an output of the image signal
outputting means involved when a light exposing position of the
light exposure lamp corresponds to the color reference member;
shading correction means for, when a light exposing position of the
light exposure lamp corresponds to the document placing area of the
document glass, correcting an output of the image signal outputting
means by a reference value retained by the control means to provide
a reading-out signal; and deciding means for deciding whether or
not the light exposure lamp burns out by comparing an output of the
image signal outputting means involved when the light exposure
position of the light exposure lamp corresponds to the color
reference member with an initially set value.
6. An apparatus according to claim 5, wherein the color reference
sheet is comprised of a black color reference sheet and white color
reference sheet, and the deciding means decides whether or not the
light exposure lamp burns out by comparing an output of the image
signal outputting means involved when the light exposure position
of the light exposure lamp corresponds to the white color reference
sheet with an initially set value.
7. An apparatus according to claim 5, further comprising printing
means for printing an image corresponding to an image signal
outputted from the image signal outputting means onto an image
formation medium; and control means for inhibiting printing by the
printing means when the deciding means decides that the light
exposure lamp burns out.
8. An apparatus according to claim 5, further comprising notifying
means for, when the deciding means decides that the light exposure
lamp burns out, notifying this effect.
Description
BACKGROUND OF THE INVENTION
[0001] In an image forming apparatus such as a copying machine, a
light exposing means is reciprocably moved along a document glass
by the operation of a scanning motor, the document glass is scanned
with light during the forward movement to read out an image of a
document, and a read-out image is formed on a copying sheet as an
image formation medium. As a scan motor use is made of a pulse
motor.
[0002] The light exposure means includes, as constituent elements,
a light exposure lamp and a carriage with the light exposure light
mounted thereon. The carriage is reciprocably moved along the
document glass and coupled to a shaft of the scan motor through a
power transmission mechanism, such as a belt and wire, and moved in
reciprocatory motion upon receipt of a power of the scan motor.
[0003] The light exposure lamp has a limited service life and, upon
burning-out, cannot read out an image on the document in which case
a copying sheet emerges as a solid black image.
[0004] During a continuous copying operation performed in a
continuous copying mode in particular, there are sometimes the
cases where the light exposure lamp will burn out. If, in this
case, a printing operation is continued to a last end in spite of
the burning-out of the light exposure lamp, a developing agent and
copying sheet are consumed in a waste manner.
BRIEF SUMMARY OF THE INVENTION
[0005] The present invention is achieved with the above-mentioned
situation in mind and it is accordingly the object of the present
invention to provide an image forming apparatus and method of
controlling the apparatus which, when a light exposure lamp burns
out, can immediately detect it and avoid a waste consumption of a
developing agent and image formation medium.
[0006] An image forming apparatus of the present invention
comprises a document glass on which a document is placed, a light
exposure lamp for exposing the document glass with light, a color
reference member for shading correction which is provided at a
non-document-placing area of the document glass, moving means for
moving the light exposure lamp along the document glass, image
signal outputting means for receiving reflected light from the
document glass under the light exposure and movement of the
exposure lamp and outputting an image signal corresponding to that
light receiving amount, and deciding means for deciding whether or
not the light exposure lamp burns out by comparing an output of the
image signal outputting means involved when a light exposing
position of the light exposure lamp corresponds to the color
reference member with an initially set value.
[0007] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0008] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0009] FIG. 1 is a view showing an outer appearance of one
embodiment of the present invention;
[0010] FIG. 2 is a view showing an internal structure according to
the embodiment of the present invention;
[0011] FIG. 3 is a view showing a structure of a document glass and
its peripheral portion of the embodiment;
[0012] FIG. 4 is a view showing a light exposure lamp and its
peripheral portion of the embodiment;
[0013] FIG. 5 is a block diagram showing a control circuit of the
embodiment;
[0014] FIG. 6 is a block diagram showing a major section of FIG.
5;
[0015] FIG. 7 is a view showing a select condition of magnetic
excitation systems of a scan motor of the embodiment;
[0016] FIG. 8 is a view showing a pattern of each kind of signal
relative to the scan motor of the embodiment;
[0017] FIG. 9 is a flow chart for explaining the drive control of
the scan motor of the embodiment;
[0018] FIG. 10 is a flow chart for explaining the detection of the
burning-out of the light exposure lamp; and
[0019] FIG. 11 is a view showing a relation of the light receiving
output of a CCD to a set value.
DETAILED DESCRIPTION OF THE INVENTION
[0020] One embodiment of the present invention will be described
below with reference to the accompanying drawing.
[0021] As shown in FIGS. 1 and 2, a transparent document glass
(glass plate) 2 is provided on the upper portion of a body 1 to
allow a document to be placed on it. An automatic document feeder
(ADF) 3 is provided over the document glass 2 in a way to be freely
openable and closable. The automatic document feeder 3 is adapted
to automatically feed document sheets one by one to allow the
document sheet to be set on the document glass.
[0022] As shown in FIG. 3, an indicator section 2a is provided on
one side section of the document glass 2. A stepped section between
the indicator section 2a and the document glass 2 provides a
reference position S for document setting. The document 11 is set
to align with the reference position S. That is, with the document
forward-end setting position S as a boundary, the indicator section
2 side (left side as indicated in Figure) provides a non-document
placing area and a remaining section (right side as indicated in
Figure) a document placing area.
[0023] A carriage 4 is provided below a lower surface side of the
document glass 2 and has an exposure lamp 5 mounted at the carriage
4. The carriage 4 and light exposure lamp 5 constitute a light
exposing means. The carriage 4 can be reciprocably moved along a
lower surface of the document glass 2. The carriage 4, while being
moved in forward motion from the non-document-placing area toward
the document placing area, allows the lower surface side of the
indicator section 2a, as well as the document glass 2, to be
scanned under the lighting of the light exposure lamp 5.
[0024] Through the light exposure scanning, a reflected light image
is obtained from the document on the document glass 2. The
reflected light image is projected onto an image signal outputting
means, such as a charge coupled device 10, through reflection
mirrors 8, 7, 8 and lens block for variable power. The CCD 10 has a
large number of photoelectric conversion elements and outputs an
image signal of a voltage level corresponding to a received light
amount. The image signal is amplified and converted to a digital
signal. The digital signal, after being properly processed by an
image processing section, is supplied to a laser unit 27. The laser
unit 27 emits a laser beam in response to an input signal.
[0025] The forward movement direction of the light exposure lamp 5
is referred to as a sub-scanning direction and a direction
perpendicular to the sub-scanning direction is referred to as a
main scanning direction.
[0026] A black color reference sheet 12 and white color reference
sheet 13 are sequentially arranged beneath the lower surface side
of the indicator section 2a, that is, the non-document-placing
area, and along the moving direction of the light exposure lamp 5
and provide a color reference member for shading correction. Both
the reference sheets have a dimensional shape corresponding to a
longitudinal length of the indicator section 2a.
[0027] As shown in FIG. 4, the carriage 4 is so set as to be
movable on a rail 51. The carriage 4 is coupled to a wire 52. The
wire 52 is spanned between a drive pulley 53a and a driven pulley
53b. The drive pulley 53a is coupled to a speed reducing pulley 54.
The speed reducing pulley 54 is connected to a pulley 56 of a scan
motor 57 through a timing belt 55. As the scan motor 57 use is made
of a pulse motor. The moving position of the carriage 4 is
controlled by the number of drive voltage pulses (the number of
steps) supplied to the scan motor 57.
[0028] The outer peripheral surface of the body 1 is formed by a
cover 58. A frame 59 is provided inside the cover 58 to retain the
rail 51. The home switch 61 is provided on the frame 59. The home
switch 61 has a slit for allowing an intrusion of a light shielding
plate 60 which is mounted on the carriage 4. The home switch
optically detects whether or not the light shielding plate 60
intrudes into the slit and it is turned ON when the plate 60
intrudes into the slit and is turned OFF when the plate 60 does not
intrude into the slit. When the home switch 61 is turned ON, it is
decided that the carriage 4 is located in a predetermined home
position.
[0029] A scanner section for image read-out is constituted by a
structure from the document glass to the home switch 61 heretofore
explained.
[0030] Within a substantially central area of the body 1, a
photosensitive drum 20 is so provided as to be rotatable. Around
the circumference of the photosensitive drum 20, a charger 21,
developing unit 22, transfer unit 23, separator 24, cleaner 25 and
discharger 26 are sequentially arranged. The laser beam emitted
from the above-mentioned laser unit 27 is directed to the surface
of the photosensitive drum 20 through an area between the charger
21 and the developing unit 22.
[0031] A plurality of sheet supply cassettes 30 are provided in a
bottom zone of the body 1. A plurality of mutually different sizes
of many copying sheets are held as an image formation medium in
these sheet supply cassettes 30. Copying sheets P are picked up one
by one from either one of the respective sheet supply cassettes 30
in accordance with an ON operation of a later-described printing
key 83. A pick-up roller 31 is provided for each sheet supply
cassette 30 to pick up the sheet. The picked-up sheet P is parted
by a parting unit 32 from the sheet supply cassette 30 and sent to
a register roller 33. The sheet P is sent to an area between the
photosensitive drum 20 and the transfer unit 20 at a considered
timing corresponding to the rotation of the photosensitive
drum.
[0032] The charger 21 applies a high voltage to the photosensitive
drum 20 to form an electrostatic charge on the surface of the
photosensitive drum 20. By directing a laser beam from the laser
unit 27 onto the resultant surface of the photosensitive drum 20,
an electrostatic latent image is formed on the surface of the
photosensitive drum 20.
[0033] The electrostatic latent image on the photosensitive drum 20
is developed by the developing unit 22 with a developing agent
(toner) to make it visible. This visible image is transferred by
the transfer unit 23 onto the copying sheet P. The sheet P with the
visible image formed thereon is separated by the separator 24 from
the photosensitive drum 20. The separated sheet P is sent by a belt
conveyor 41 to a fixing unit 42. The fixing unit 42 allows an image
which is transferred onto the sheet P to be thermally fixed. The
image-fixed sheet P is discharged by discharge rollers 43 onto a
discharge tray 44.
[0034] It is to be noted that, on the surface of the photosensitive
drum 20 where the sheet P is separated, the developing agent and
charge remain. The remaining developing agent is eliminated by the
cleaner 25 and the remaining charge is eliminated by the discharger
28.
[0035] By the structure from the photosensitive drum 20 to the
discharge tray 44 as heretofore explained, a printer section is
provided to allow an image which is read out by the scanner section
to be printed on the sheet.
[0036] A whole control circuit is shown in FIG. 5.
[0037] A system CPU 70, control panel CPU 80, scanner CPU 90 and
printer CPU 100 are connected to each other. The system CPU 70
coordinately controls the control panel CPU 80, scanner CPU 90 and
printer CPU 100.
[0038] To the system CPU 70, a ROM 71 for control program storage,
RAM 72 for data storage, NVM 73, image processing section 74 and
page memory control section 75 are connected. To the page memory
control section 75 a page memory 76 is connected to store image
data page by page.
[0039] To the control panel CPU 80 a keying-in section 81, liquid
crystal display section 82 and printing key 83 are connected. The
keying-in section 81 has a power source switch, document size
designation key, magnification designation key, etc. The liquid
crystal display section 82 displays information corresponding to
the operation of the keying-in section 81 and various kinds of
information to be notified to the user.
[0040] To the scanner CPU 90, a ROM 91 for control program storage,
RAM 92 for data storage, automatic document feeder (ADF) 3, shading
correction section (SHD) 93, CCD driver 94, scan motor driver 95,
above-mentioned light exposure lamp 5, etc., are connected. The CCD
driver 94 drives the above-mentioned CCD 10. The scan motor driver
95 drives the above-mentioned scan motor 57.
[0041] To the printer CPU 100, a ROM 101 for control program
storage, RAM 102 for data storage, laser driver 103, polygon motor
driver 104 and main motor driver 106 are connected. The laser
driver 103 drives the above-mentioned laser unit 27. The polygon
motor driver 104 drives a polygon motor serving as a drive source
for driving a polygon mirror for allowing the photosensitive drum
20 to be scanned with the laser beam. The main motor driver 106
drives the main motor 107 serving as a drive source for driving the
photosensitive drum 20, sheet conveying mechanism etc.
[0042] The above-mentioned shading correction section 93 has the
following means [1] and [2] as the main functions.
[0043] [1] A control means which, when the moving position of the
carriage 4, that is, the light exposure position of the light
exposure lamp 5, corresponds to the black color reference sheet 12
and white color reference sheet 13 in the non-document-placing
area, retains the light receiving output of the CCD 10 as a shading
correction reference value in an internal memory.
[0044] [2] A correcting means which, when the moving position of
the carriage 4, that is, the light exposure position of the light
exposure lamp 5, corresponds to the document placing area, corrects
the light receiving output of the CCD 10 by the retained reference
value to provide a read-out signal.
[0045] And the system CPU 70 and scanner CPU 90 have the following
means [11] to [13] as main functions.
[0046] [11] A detecting means which, out of a light receiving
output of the CCD 10 involved when the light exposure position of
the light exposure lamp 5 corresponds to the white color reference
sheet 13, reads out those light receiving outputs (image signals)
corresponding to one line of the main scanning from the internal
memory, calculates an average value of the light receiving outputs,
and compares the average value with a set value stored in the ROM
91 to see whether or not the light exposure lamp burns out. Stated
in more detail, the light exposure lamp 5 is decided as being
normal if the average value is larger than the set value and as
burning out if the average value is less than the set value.
[0047] [12] A control means for immediately stopping a printing
operation when it is decided that the light exposure lamp 5 burns
out. [13] A notifying means which, when a result is obtained to the
effect that the exposure light lamp 5 burns out, notifies this
effect as a character display or image pattern display to the
liquid crystal section 82.
[0048] Incidentally, as shown in FIG. 6, a gate array 96 and D/A
converter 97 are provided between the scanner CPU 90 and the scan
motor driver 95.
[0049] In response to instruction data from the scanner CPU 90, the
gate array 96 outputs a control signal H.multidot.OFF.multidot.1
for designating a magnetic excitation ON or magnetic excitation OFF
of the scan motor 57, a control signal CWCCW for designating a
normal rotation operation or reverse rotation operation of the scan
motor 57 and data signals DATA0, DATA1, DATA2, DATA3 for
designating a magnetic excitation system of the motor 57. These
signals are supplied to a scan motor driver 95. The D/A converter
97 converts current value designation data which is issued from the
scanner CPU 90 to a voltage signal SCNVREFA for phase current value
designation to the scan motor 57. This voltage signal SCNVREFA is
supplied to the scan motor driver 95.
[0050] Further, a reference clock signal SCCLK-0 is supplied from
the scanner CPU 90 to the scan motor driver 95. The scan motor
driver 95 outputs a drive voltage pulse synchronized with a leading
edge of a reference clock signal SCCLK.multidot.0. This drive
voltage pulse is supplied to the scan motor 57. The scanner CPU 90
varies the interval of the reference clock signal SCCLK.multidot.0
in response to a magnification set by the keying-in section 81. In
accordance with this variation, the interval of the drive voltage
pulse supplied to the scan motor 57 varies to change the rotation
speed of the scan motor 57, that is, the moving speed of the
carriage 4.
[0051] FIG. 7 shows a select condition under which, in response to
the above-mentioned 4-bit data signals DATA0, DATA1, DATA2, DATA3,
any given magnetic excitation system is selected in the case where
a 5-phse pulse motor is used as the scan motor 57. In the present
embodiment, any of the magnetic excitation systems A, B, C and D is
selected.
[0052] FIG. 8 shows a practical pattern of each signal relating to
the driving of the scan motor 57. In this example, the magnetic
excitation system C is selected.
[0053] At the time of the forward movement of the carriage 4, the
scan motor 57 first performs an acceleration operation toward a
target speed, then a uniform speed at a position in which the
target speed is reached, and finally a deceleration operation.
During a period in which the scan motor 57 operates at the uniform
speed, an image on the document 11 is read out. Even at a time of a
return movement of the carrier 4, the scan motor 57 first performs
an acceleration operation, then a uniform speed operation and
finally a deceleration operation. The switching of the acceleration
operation, uniform-speed operation and deceleration operation is
achieved by varying the interval of the reference clock signal
SCCLK-0.
[0054] Now the operation will be explained below.
[0055] The drive control of the scan motor 57 will be described
below with reference to the follow chart of FIG. 9.
[0056] It is decided that the copying magnification designated at
the keying-in section 81 is any of .left brkt-top.25 to 47%.right
brkt-bot., .left brkt-top.48 to 95%.right brkt-bot., .left
brkt-top.96 to 194% .right brkt-bot. and .left brkt-top.195 to
400%.right brkt-bot. (steps 111, 112, 113). In the case where the
copying magnification is .left brkt-top.25 to 47%.right brkt-bot.
(YES of step 101), the magnetic excitation system A is selected
(step 114). In the case where the copying magnification is .left
brkt-top.48 to 95%.right brkt-bot. (NO of step 111, YES of step
112), the magnetic excitation system B is selected (step 115). In
the case where the copying magnification is .left brkt-top.96 to
194%.right brkt-bot. (NO of step 111, NO of step 112 and YES of
step 113), the magnetic excitation system C is selected (step 116).
In the case where the copying magnification is .left brkt-top.195
to 400%.right brkt-bot. (NO of step 111, NO of step 112 and NO of
step 113), the magnetic excitation system D is selected (step
117).
[0057] As shown under the select condition of FIG. 7, in the case
of the magnetic excitation system A, a rotation angle corresponding
to one step of the scan motor 57 is set to .left
brkt-top.0.72.degree..right brkt-bot.. In the case of the magnetic
excitation system B, a rotation angle corresponding to one step of
the scan motor 57 is set to .left brkt-top.0.36.degree..right
brkt-bot.. In the case of the magnetic excitation system C, a
rotation angle corresponding to one step of the scan motor 57 is
set to .left brkt-top.0.288.degree..right brkt-bot.. In the case of
the magnetic excitation system D, a rotation angle corresponding to
one step of the scan motor 57 is set to .left
brkt-top.0.09.degree..right brkt-bot.. That is, as the copying
magnification is greater, the rotation angle corresponding to one
step of the scan motor 57 is set smaller and the moving speed of
the carriage 4 becomes slower.
[0058] The number of reference steps necessary for the carriage 4
from a present position to the target position is calculated (step
118). The number of reference steps calculated is converted to the
number of actual steps corresponding to the selected magnetic
excitation system (step 119). The number of actual steps is sorted
into those for the acceleration operation, uniform speed operation
and deceleration operation (step 120). The scan motor 57 is driven
based on the numbers of sorted actual steps (step 121).
[0059] The control as to decide whether or not the light exposure
lamp 5 burns out will be explained below with reference to the flow
chart of FIG. 10.
[0060] When the power source of the body 1 is turned ON (YES of
step 201), an initializing operation is performed (step 202). The
initializing operation is so performed as to accurately set a
physical position of the carriage 4 relative to a one-step-unit
coordinate (hereinafter referred to as a management coordinate) by
which the moving position of the carriage 4 is controlled.
[0061] After the initializing operation has been completed, a peak
detection control is performed (step 203). Since, in general, the
voltage of the image signal outputted from the CCD 10 is very
small, it is amplified by an amplifier. The amplified image signal
is converted by the A/D converter to a digital signal to provide
image data. It is to be noted that, in the A/D converter, there is
an allowable voltage range relative to the input voltage and, if
the voltage of the image signal is outside the allowable voltage
range, any proper image data fails to be obtained. In order to
prevent such inconvenience, it is necessary to adjust the
amplification degree of the amplifier to a proper value and this
adjustment is performed by the peak detection control.
[0062] Under the peak detection control, the carriage 4 is moved to
a position corresponding to the white color reference sheet 13 and
the light exposure lamp is turned ON. In a state in which the light
of the light exposure lamp 5 is given onto the white color
reference sheet 13, the light receiving output of the CCD 10 is
retained, for example, in RAM 92. Out of the light receiving output
thus retained, a peak value is detected and, based on a result of
this detection, the amplification degree of the above-mentioned
amplifier is adjusted to a proper value.
[0063] Out of the light receiving output retained in the RAM 92
under the peak detection control, those light receiving outputs
(image signals) corresponding to one line of the main scanning are
read and an average value of the light receiving values is
calculated (step 204). And the calculated average value is compared
with a set value initially stored in ROM 91 (step 205).
[0064] In the case where the light exposure lamp 5 burns out, the
light receiving output of the CCD 10 is less than a set value as
shown in FIG. 11. In this case (YES of step 205), it is decided
that the light exposure lamp 5 burns out (step 206). And a
subsequent printing operation is inhibited (step 207) and the
burning-out of the light exposure lamp 5 is notified as a character
display or image pattern display on the liquid crystal section 82
(step 208). By the inhibiting of the printing operation, a waste
consumption of the developing agent and copying sheet is
prevented.
[0065] In the case where the light exposure lamp 5 is normally
lighted, the light receiving output of the CCD 10 becomes larger
than the set value. In this case (NO of step 205), it is decided
that the light exposure lamp 5 is normal (step 209) and a
subsequent printing operation is allowed (step 210).
[0066] When the printing key 83 is rendered ON (YES of step 211)
with the power source already in an ON state (NO of step 201), the
carriage 4 is moved to a home position (step 212). By the lighting
of the exposure lamp 5 and forward movement of the carriage 4,
scanning is started (step 213) and, when the light exposure
position of the light exposure lamp 5 corresponds to the black
color reference sheet and white color reference sheet 13, the
shading correction is performed (step 214). That is, the light
receiving output (black color signal level and white color signal
level) of the CCD 10 is retained as a reference value in the
internal memory of the shading correction section 93.
[0067] When the light exposure position of the exposure lamp 5
corresponds to the document placing area of the document glass 2,
the light receiving output of the CCD 10 is corrected by the
above-mentioned retained reference value to provide a read-out
signal.
[0068] By reading out the black and white color reference sheets
and, by doing so, initially setting the references of the upper and
lower values of the image data, image data obtained by reading out
the actual document 11 can be represented as a ratio of the black
and while colors. This is a shading correction and it is possible
to obtain a stable read-out signal without considering an uneven
light amount of the light exposure lamp 5, lens accuracy, output
error levels of respective elements of the CCD 10, etc. This
provides a better finished image formation.
[0069] Out of the light receiving output retained in the internal
memory of the shading correction section 93 at the shading
correction, those light receiving outputs (image signals)
corresponding to one line of the main scanning are read and an
average value of the light receiving outputs is calculated (step
204). And the calculated average value is compared with a set value
initially stored in the ROM 91 (step 205).
[0070] In the case where the light exposure lamp burns out, the
light receiving output of the CCD 10 becomes less than the set
value as shown in FIG. 11. In this case (YES of step 205), it is
decided that the light exposure lamp 5 burns out (step 206). And a
subsequent printing operation is inhibited (step 207) and the
burning-out of the light exposure lamp 5 is notified as a character
display or image pattern display on the liquid crystal display
section 82 (step 208).
[0071] In the case where the light exposure lamp 5 is normally
lighted, the light receiving output of the CCD 10 becomes larger
than the set value. In this case (NO of step 205), it is decided
that the light exposure lamp 5 is normal (step 209) and a
subsequent printing operation is allowed (step 210).
[0072] In a continuous copying for continuously performing the
copying of many sheets, the operation of the carriage 4 and
scanning of the light exposure lamp 5 are performed for each
copying. And the shading correction is performed for each scanning
and it is decided whether or not the light exposure lamp 5 burns
out for each performance of the shading correction.
[0073] In the case where, as set out above, the light exposure lamp
5 burns out during a continuous copying operation, the printing
operation is immediately inhibited, thus preventing a waste
consumption of the developing agent and copying sheet P. Further,
since the present apparatus detects the burning-out of the light
exposure lamp through the utilization of the white color reference
sheet 13 for shading correction, no special component parts for
detection is necessary and it is possible to avoid a rise in
cost.
[0074] Although, in the above-mentioned embodiment, the burning-out
of the light exposure lamp has been explained as being detected by
calculating an average value of the light receiving outputs
corresponding to one line of the main scanning of the CCD 10 and
comparing the average value with the set value, it is not
necessarily required that the average value be calculated. It may
be possible to sequentially compare the light receiving output
corresponding to one line of the main scanning of the CCD 10 with
the set value and detect the burning-out of the light exposure lamp
in accordance with a result of comparison.
[0075] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
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