Picture reading apparatus with flaring light elimination capability

A picture reading apparatus with flaring light elimination capability, which includes a light source for emitting light, a contact glass with which a document to be scanned comes in contact, a lens array in which a plurality of lenses for converging the light from the light source are arranged at equal intervals therebetween, a roof mirror array in which a plurality of roof-like reflection surfaces are arranged corresponding to the plurality of lenses, a restricting plate for eliminating undesired light between adjacent lenses of the lens array, a housing in which the roof mirror array and the lens array are accommodated, a sensor, and a separation mirror. The apparatus further includes a light shield layer provided on the contact glass, at a portion other than a reading portion through which the light from the light source passes to scan the document, for eliminating undesired light, other than the converged light effective in supplying a picture signal.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to a picture reading apparatus, and 
more particularly to a picture reading apparatus with flaring light 
elimination capability, which is applicable to a picture reading part of a 
facsimile machine, an image scanner or the like. 
2. Discussion of the Background 
Japanese Laid-Open Patent Application No. 1-265660 discloses a conventional 
picture reading apparatus in which a focusing lens array is used, as shown 
in FIG. 1. In FIG. 1, the picture reading apparatus includes a 
non-reduction type image pickup element 21, slit plates 22, a fluorescent 
lamp 23, a light converging lens 24, a focusing lens array 25, and a 
contact glass 28. Light that is emitted by the fluorescent lamp 23 is 
converged by the light converging lens 24 and this converging light is 
irradiated to a document 26 through the contact glass 28. The document 26 
is scanned in a main scanning direction, which is perpendicular to the 
sheet of FIG. 1, by the light from the fluorescent lamp 23. Because the 
document is transported in a direction indicated by an arrow A in FIG. 1, 
the scanning of the light from the fluorescent lamp 24 is also made in a 
sub scanning direction which is perpendicular to the main scanning 
direction. An irradiation width or length 27 of the light from the 
fluorescent lamp 23 in the sub scanning direction, where the light is 
irradiated to the document 26, is limited by the slit plates 22 the edge 
portions of which form a slit at a portion between the light converging 
lens 24 and the contact glass 28. This irradiation width is thus limited 
to less than 30 mm in the sub scanning direction, preferably to less than 
2 mm. 
On the other hand, light that is reflected from the document 26 is focused 
by the focusing lens array 25 on the non-reduction type image pickup 
element 21, and this image pickup element 21 supplies a picture signal 
indicative of a picture from the document 26. However, there appears 
irregular reflection light irregularly reflected by a document surface, 
where the scanning is not made by the emitted light from the light source, 
or by a portion of the contact glass 28, which irregular reflection light 
may enter directly the focusing lens array 25, thereby deteriorating the 
quality of a picture being reproduced from the picture signal supplied by 
the image pickup element 21. The conventional picture reading apparatus 
has no effective means for preventing such reflected light from entering 
directly the focusing lens array and from being led to the image pickup 
element. Therefore, there is a problem in that the conventional picture 
reading apparatus does not show enough image focusing performance, because 
it has no means for preventing undesired light, other than the converged 
light from the light source effective in supplying a picture signal, from 
entering directly inside of the focusing lens array. 
FIG. 2 shows another example of the conventional picture reading apparatus 
to which a roof mirror lens array (RMLA) is applied. This picture reading 
apparatus as shown in FIG. 2 includes an optical path separation mirror 
(SM) 31, a lens array (LA) 32, a roof mirror array (RMA) 33, a restricting 
plate (not shown) provided between the LA 32 and the RMA 33, and a housing 
(not shown) for holding the above mentioned component parts and shielding 
the inside of the apparatus from external light. Light from an object 34 
to be scanned is reflected by the SM 31 and this reflected light passes 
through the LA 32 and is irradiated to the RMA 33. The lens array 32 has a 
plurality of lenses arranged consecutively at equal intervals in the main 
scanning direction, as indicated by an arror Y in FIG. 2, and each lens of 
the lens array 32 converges the reflected light from the separation mirror 
31 into a converged light which is led to the RMA 33. The separation 
mirror 31 serves to separate an optical path of light, being led from the 
object 34 to the lens array 32, from an optical path of the converging 
light from the lens array toward the SM 31. The roof mirror array 33 which 
has a plurality of roof-like reflection surfaces arranged consecutively at 
equal intervals in the main scanning direction, as indicated by the arrow 
Y in FIG. 2. The converging light, being led from each lens of the lens 
array 32 to the SM 31, is again reflected by each roof-like reflection 
surface of the roof mirror array 33, and this reflected light is focused 
as an image 35 on a position symmetrical to the position of the object 34 
with respect to the plane of the picture reading apparatus. 
The image 35 is an erect image with respect to the object 34 both in the 
main scanning direction Y and in the sub scanning direction as indicated 
by an arrow X in FIG. 2. In particular, this image is a non-reduction 
erect image having a scale factor equal to 1 in the sub scanning direction 
X. Therefore, the necessary scanning width is covered by overlapping an 
image formed by means of a lens of the LA and a roof mirror of the RMA in 
the sub scanning direction X. The lenses of the LA, the roof-like 
reflection surfaces of the RMA and the restricting plates must be 
respectively arranged at equal intervals therebetween, and each lens of 
the lens array 32 must show essentially the same light quantity 
distribution. For this reason, the distribution of light quantity of each 
lens in the LA 32 is predetermined to be uniform in the main scanning 
direction Y. 
However, in the case of the conventional picture reading apparatus as shown 
in FIG. 2, the emitted light from the light source passes through a 
transparent portion of the separation mirror, and such light is 
irregularly reflected or scattered in the RMLA optical system, resulting 
in a flaring light which particularly lowers the image focusing 
performance of the picture reading apparatus. In addition, the 
conventional picture reading apparatus described above employ a slit which 
is arranged between the light source and the document. However, the use of 
a slit by the picture reading apparatus requires an increase in the total 
number of parts needed, and also requires additional time to perform 
manufacturing steps of positioning and adjustment of a slit in the picture 
reading apparatus. 
SUMMARY OF THE INVENTION 
Accordingly, it is a general object of the present invention to provide an 
improved picture reading apparatus in which the above described problems 
of the conventional apparatus are eliminated. 
Another and more specific object of the present invention is to provide a 
picture reading apparatus which allows a high quality picture to be 
generated from a scanned document, by eliminating undesired light other 
than the converged light from the light source effective in supplying the 
picture signal. Still another object of the present invention is to 
provide a picture reading apparatus having a light shield layer formed 
integrally with a contact glass, ensuring good positioning accuracy for 
the parts of the apparatus and a reduction of manufacturing costs. The 
above mentioned objects can be achieved by a picture reading apparatus 
which comprises a light source for emitting light, a contact glass with 
which a document is placed in contact so that the document is scanned by 
the emitted light from the light source along a main scanning line, a lens 
array in which a plurality of lenses are arranged consecutively at equal 
intervals therebetween along the main scanning line, each of the plurality 
of lenses converging a reflected light which is reflected from the 
document through the contact lens, a roof mirror array in which a 
plurality of roof-like reflection surfaces for reflecting the converged 
light from the lens array back to the lens array are arranged, 
corresponding to the plurality of lenses, at equal intervals therebetween 
along the main scanning line, a restricting plate provided between the 
lens array and the roof mirror array for eliminating flaring light between 
adjacent lenses of the lens array, a housing in which the roof mirror 
array and the lens array are accommodated to form a roof mirror lens 
array, a sensor for receiving the converged light reflected by the roof 
mirror array so that the received light is converted into a picture signal 
indicative of a picture contained in the document, a separation mirror for 
reflecting the converged light from the lens array to the sensor 
separately from an optical path of the reflected light from the document 
and led to the lens array, and a light shield layer formed integrally with 
a surface of the contact glass, the light shield layer including a reading 
portion to which the emitted light from the light source is led to pass 
through the contact glass for scanning the document, the light shield 
layer being provided at a portion other than the reading portion on the 
surface of the contact glass. According to the present invention, it is 
possible for the integrally formed light shield layer to suitably 
eliminate undesired light, other than the converged light from the light 
source effective in supplying a picture signal. The picture reading 
apparatus with the light shield layer requires no need for positioning and 
adjustment of a slit which has been used within the conventional 
apparatus, thus facilitating the assembly and manufacture of the picture 
reading apparatus because only the contact glass with the integrally 
formed light shield layer is used. 
A further object of the present invention is to provide a picture reading 
apparatus in which a light shield member is provided between a contact 
glass and a separation mirror for eliminating the undesired flaring light, 
ensuring good positioning accuracy for the parts of the apparatus and a 
reduction in the manufacturing cost thereof. The above mentioned object of 
the present invention can be achieved by a picture reading apparatus which 
comprises a light source for emitting light, a contact glass with which a 
document is placed in contact so that the document is scanned by the 
emitted light from the light source along a main scanning line, a lens 
array in which a plurality of lenses are arranged consecutively at equal 
intervals therebetween along the main scanning line, each of the plurality 
of lenses converging a reflected light which is reflected from the 
document through the contact lens, a roof mirror array in which a 
plurality of roof-like reflection surfaces for reflecting the converged 
light from the lens array back to the lens array are arranged, 
corresponding to the plurality of lenses, at equal intervals therebetween 
along the main scanning line, a restricting plate provided between the 
lens array and the roof mirror array for eliminating flaring light between 
adjacent lenses of the lens array, a housing in which the roof mirror 
array and the lens array are accommodated to form a roof mirror lens 
array, a sensor for receiving the converged light reflected by the roof 
mirror array so that the received light is converted into a picture signal 
indicative of a picture contained in the document, a separation mirror for 
reflecting the converged light from the lens array to the sensor 
separately from an optical path of the reflected light from the document 
and led to the lens array, and a light shield member provided between the 
light source and the separation mirror for preventing part of the emitted 
light from the light source from entering directly the interior of the 
roof mirror lens array. According to the present invention, it is possible 
for the light shield member to suitably eliminate flaring light, due to 
the irregular reflection and scattering of the light from the light 
source, which enters the transparent portion of the separation mirror and 
is led to the inside of the RMLA. In addition, it is possible for the 
present invention to prevent the image focusing performance of the picture 
reading apparatus from deteriorating due to such flaring light. 
Other objects and further features of the present invention will be more 
apparent from the following detailed description when read in conjunction 
with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First, a description will be given of an embodiment of a picture reading 
apparatus according to the present invention in which a focusing lens 
array is incorporated, with reference to FIG. 3. In FIG. 3, this picture 
reading apparatus generally has a housing 1 in which the focusing lens 
array is accommodated, a light source (LED) 2 for emitting light which is 
irradiated to a document to be scanned, a contact glass 3 with which the 
document is brought into contact, a light shield layer 4 formed integrally 
with the contact glass 3, a non-reduction type focusing lens element 5 
with a scale factor equal to 1, the focusing lens element 5 serving as the 
focusing lens array (or, a so-called rod lens array), and a non-reduction 
type sensor 6 with a scale factor equal to 1. In this apparatus as shown 
in FIG. 3, the light shield layer 4 is formed on a top surface of the 
contact glass 3 and includes a reading portion from which the emitted 
light from the light source 2 passes through the contact glass 3 to scan 
the document in a main scanning direction for supplying a picture signal 
for each scan. Thus, the reading portion of the light shield layer 4 has a 
width in the main scanning direction, which is necessary for the scanning 
by the emitted light from the light source. The light shield layer 4 shown 
in FIG. 3 is provided at a portion on the top surface of the contact glass 
3, other than the above described reading portion, which is opposed to the 
light source 2. The light shield layer 4 serves to eliminate undesired 
light reflected from the contact glass surface or light reflected from the 
document through the contact glass 3. The light shield layer 4 may be 
formed on a surface of the contact glass using a light absorbing material 
through an appropriate process such as photolithography, coating, or 
vacuum evaporation. Additionally, the light shield layer 4 may be formed 
by grinding a contact glass surface at the corresponding portion of the 
light shield layer 4 into a roughly ground glass surface and by applying a 
light absorbing material to the ground glass surface. 
In the case of the picture reading apparatus shown in FIG. 3, instead of a 
conventional light source with bar a lens being used, a light source unit 
in which LED chips are arranged on a substrate to form a light emitting 
array has recently been used as the light source 2 of the picture reading 
apparatus in order to reduce the manufacturing cost. However, when such a 
new light source unit is used as the light source 2, the picture reading 
apparatus shows a slightly lower light converging performance when 
compared with that of the conventional apparatus, and light is emitted 
from the whole surface of a plastic coating which covers light emitting 
elements (for example, GaAsP or GaAlAs diodes) of the light source 2, 
which causes undesired light to appear, apart from the converged light 
being irradiated to the document through the reading portion of the light 
shield layer 4. 
FIG. 4 shows another example of the picture reading apparatus according to 
the present invention. In FIG. 4, those parts which are essentially the 
same as those corresponding parts of the apparatus shown in FIG. 3 are 
designated by the same reference numerals, and a description thereof will 
be omitted. The light shield layer 4 as shown in FIG. 4 is provided on a 
bottom surface of the contact glass 3 which is opposed to a document to be 
scanned. Similar to the embodiment shown in FIG. 3, the light shield layer 
4 shown in FIG. 4 serves to eliminate flaring light from from the document 
through the contact glass 3. The light shield layer 4 may be formed 
through the same process as in the above embodiment shown in FIG. 3. Also, 
the light shield layer 4 may be made of metal such as chromium or a 
metallic oxide such as chromium oxide, through an appropriate process 
including sputtering, vacuum evaporation and the like. Preferably, an 
opaque metallic film for preventing light reflection is formed through 
sputtering or a vacuum evaporation process on the top surface of the 
contact glass 3, opposed to the light source, in addition to the light 
shield layer 4 formed on the bottom surface as described above. In 
addition, it is a matter of course that the light shield layer 4 may be 
formed on both the top and bottom surfaces of the contact glass 3, 
respectively opposed to the light source 2 and to the document. 
FIG. 5 shows an embodiment of the picture reading apparatus of the present 
invention to which a roof mirror lens array (RMLA) is applied. This 
picture reading apparatus shown in FIG. 5 includes a housing 11 in which 
the RMLA is accommodated, a light source 12 (LED) for emitting light, a 
contact glass 13 with which a document to be scanned is placed in contact, 
a light shield layer 14, an optical path separation mirror (SM) 15, 
positioned substantially perpendicularly to the light source 12, for 
reflecting the converged light from the RMLA separately from an optical 
path of the reflected light from the document being led to the RMLA, a 
lens array (LA) 16 in which a plurality of lenses are arranged at equal 
intervals therebetween along a main scanning line, each of the lenses 
converging reflected light from the document through the contact lens 13, 
a restricting plate 17 for eliminating flaring light between adjacent 
lenses of the lens array 16, a roof mirror array (RMA) 18 in which a 
plurality of roof-like reflection surfaces for reflecting the converged 
light from the lens array 16 back to the lens array 16 are arranged, 
corresponding to the lenses of the LA 16, at equal intervals therebetween 
along the main scanning line, and a non-reduction type sensor 19 with a 
scale factor equal to 1, which receives the converged light reflected by 
the RMA 18 so that the received light is photoelectrically converted into 
a picture signal indicative of an image contained in the document. The 
separation mirror 15 has a transparent portion through which the reflected 
light from the document passes, and a mirror portion in which the 
converged light from the RMLA is reflected to the sensor 19. With the thus 
constructed RMLA used, it is possible to construct the picture reading 
apparatus so as to be of a smaller size as compared with the size of the 
above mentioned picture reading apparatus with the focusing lens array 
being used. Similar to the above embodiments shown in FIGS. 3 and 4, the 
light shield layer 14 formed on the contact glass 3 allows undesired 
light, different from the effective irradiation light from the light 
source 12 for supplying a picture signal, to be eliminated. In a case of 
the RMLA type apparatus, the optical path separation mirror 15 is provided 
for separating light being irradiated to a document from light being 
reflected from the document, and this optical path separation mirror is 
arranged at a portion different from a portion along the optical axis of 
the RMLA optical system including the lens array 16. The light that is 
reflected by the document with respect to an axis parallel to the optical 
axis of the RMLA and perpendicular to the contact glass and led to the 
RMLA is asymmetrical with respect to the optical axis L0. 
As is apparent from FIG. 6, the light source 12, the contact glass 13 and 
the lens array 16 are arranged to form an optical system, such that the 
light reflected from a document with respect to an axis L1, as indicated 
by a dotted line in FIG. 6, parallel to the optical axis L0, as indicated 
by a dot-dash line in FIG. 6 and perpendicular to the contact glass 13 and 
led to this optical system is asymmetrical with respect to the optical 
axis L0 of the optical system. Therefore, the emitted light from the light 
source 12 is reflected by the contact glass 13 in directions as indicated 
by lines E and E1, the picture reading apparatus is constructed such that 
the image focusing performance is not easily influenced by light regularly 
reflected by the contact glass 13. 
FIG. 7 shows another embodiment of the picture reading apparatus of the 
present invention in which the RMLA is incorporated. In this picture 
reading apparatus as shown in FIG. 7, an optical path separation mirror 
(SM) 20 is formed so as to have two reflection surfaces, a reflected light 
from a document being reflected by one of the two reflection surfaces of 
the SM 20 and a converged light from the lens array 16 is reflected by the 
other reflection surface thereof. The use of the SM 20 in the picture 
reading apparatus allows the contact glass 13 and the non-reduction type 
sensor 19 to be arranged substantially parallel to each other. Thus, the 
picture reading apparatus as shown in FIG. 7 can be constructed so as to 
have a smaller height or thickness in the vertical direction, and it is 
possible to construct a compact optical scanning unit including a 
facsimile, an image scanner or the like. 
FIG. 8 shows still another embodiment of the picture reading apparatus of 
the present invention. In this picture reading apparatus as shown in FIG. 
8, a plate-like light shield member 141 is provided between the light 
source 12 and the optical path separation mirror 15. This light shield 
member 141 serves to prevent undesired light from the light source 12 from 
entering the interior of the roof mirror lens array (RMLA). If the emitted 
light from the light source 12 enters a transparent portion (which is made 
of glass or plastic material) of the optical path separation mirror 15, 
the light is diffracted by the separation mirror 15 and scattered in the 
RMA 18, resulting in flaring light which will deteriorate the image 
focusing performance of the picture reading apparatus. The light emitted 
by the light source 12 may be diffracted, particularly on a surface of the 
transparent portion of the optical path separation mirror 15, toward the 
lens array (LA) 16, and such diffracted light may be led to the interior 
of the RMLA optical system. Thus, the light shield member 141 is effective 
in eliminating the undesired flaring light from entering the RMLA. Similar 
to the apparatus shown in FIG. 5, it is possible to form additionally the 
light shield layer 14, integrally with the contact glass 13, which is 
provided on a surface of the contact glass 13 in the picture reading 
apparatus shown in FIG. 8, for eliminating or shutting out undesired 
flaring light, different from the converging light used for the scanning 
of the document. This light shield layer 14 on the contact glass 13 serves 
to eliminate undesired light, including light reflected from a surface of 
the contact glass 13 which is opposed to the mirror 15 and light emitted 
by the light source 12 which is different from the converging light used 
for the scanning of the document. 
FIG. 9 shows a further embodiment of the picture reading apparatus of the 
present invention in which a light shield plate 141 is provided between 
the light source 12 and the optical path separation mirror 15. This light 
shield plate 141 has a light absorbing layer 14a which is formed on a 
surface of the light shield plate 141. With this light absorbing layer 14a 
formed on the light shield plate 141, it is possible to eliminate 
effectively undesired flaring light irregularly reflected or scattered by 
the surface of the light shield plate 141. This light absorbing layer 14a 
may be formed on a surface of the light shield plate 141 using a light 
absorbing material through an appropriate process such as 
photolithography, coating, vacuum evaporation or the like. The light 
absorbing layer 14a may be also formed by grinding the surface of the 
light shield plate 141 into a roughly ground surface and by applying a 
light absorbing material to the ground surface. In addition, there are 
several methods of forming the light shield plate 141 with the light 
absorbing layer 14a. One method is that the light shield plate 141 is made 
of aluminum alloy and a surface of the light shield plate 141 is 
chemically processed by etching using acid or alkali to form a black film 
of aluminum oxide Al.sub.2 O.sub.3 on the surface of the light shield 
plate 141. Another method is that the light shield plate 141 is made of 
copper alloy and a surface of the light shield plate 141 is processed to 
deposit a black light absorbing layer thereon. 
The light source which is used in the picture reading apparatus shown in 
FIGS. 8 and 9 may be a light source unit in which LED chips are linearly 
arranged on a substrate to form a light emitting array. The use of this 
light source unit will enable a reduced quantity of undesired flaring 
light, a low manufacturing cost, easy assembly and adjustment for the 
manufacture, and so on. However, it is a matter of course that a 
fluorescent lamp, a cold cathode fluorescent lamp, a LED with bar lens, or 
a halogen lamp can be used instead of the above described light source 
unit in the picture reading apparatus shown in FIGS. 8 and 9. 
FIGS. 10 through 12 show further embodiments of the picture reading 
apparatus of the present invention. In the picture reading apparatus as 
shown in FIG. 10, a light shield plate 142 which is provided between the 
light source 12 and the optical path separation mirror 15 is placed in 
contact with a reverse surface of the separation mirror 15. This light 
shield plate 142 serves to eliminate undesired light, which is different 
from the effective irradiation light from the light source 12 for 
supplying a picture signal. The undesired light includes light that is 
irregularly reflected by the top surface of the contact glass 13 and led 
to the separation mirror 15, and light that is emitted by the light source 
12 and led directly to the separation mirror 15. With this light shield 
plate 142 being used, the picture reading apparatus can suitably eliminate 
such undesired light, thereby preventing the flaring light from entering 
the separation mirror 15. 
In the picture reading apparatus shown in FIG. 11, a L-shaped light shield 
plate 143 with a light absorbing layer formed on a surface thereof, which 
is provided between the light source 12 and the optical path separation 
mirror 15, is placed at one half portion thereof in contact with a reverse 
surface of the separation mirror 15. This light shield plate 143 is bent 
at the middle portion thereof, such that the other portion of the light 
shield plate 143 is faced to the contact glass 13. This light shield plate 
143 serves to eliminate undesired light, which is different from the 
effective irradiation light from the light source 12 for supplying a 
picture signal. The undesired light includes light that is irregularly 
reflected by the top surface of the contact glass 13 and led to the 
separation mirror 15, and light that is emitted by the light source 12 and 
led directly to the separation mirror 15. In addition, this L-shaped light 
shield plate 143 on which a light absorbing layer is formed serves to 
eliminate effectively undesired light that is emitted by the light source 
12 and reflected or scattered on the surface of the light shield plate 
143. 
In the picture reading apparatus shown in FIG. 12, a L-shaped light shield 
plate 143, similar to that shown in FIG. 11, is placed at one half portion 
thereof in contact with a reverse surface of an optical path separation 
mirror 151 which is different from the optical path separation mirror 15 
shown in FIG. 11. The separation mirror 151 shown in FIG. 12 has only a 
mirror portion for reflecting the converged light from the RMLA to the 
sensor 19 and it has no transparent protion. The reason for this 
half-sized separation mirror is to reduce the manufacturing cost. 
Further, the present invention is not limited to the above described 
embodiments, and variations and modifications may be made without 
departing from the scope of the present invention.