JP4355263B2 - Document illumination device, image reading device, color document reading device, image forming device, film scanner, and digital laboratory - Google Patents

Description

  The present invention relates to a document illumination device used for a reading device such as a digital copying machine, an image scanner, or a digital laboratory.

  In recent years, light emitting diodes (hereinafter referred to as LEDs) have been actively developed, and the brightness of LED elements has increased rapidly. LEDs generally have advantages such as long life, high efficiency, high G resistance, and monochromatic light emission, and are expected to be applied in many lighting fields. One of the applications is a document illumination device of an image reading device such as a digital copying machine or an image scanner.

FIG. 26 is a schematic diagram of an image forming apparatus having an image reading apparatus.
In the figure, reference numeral 100 denotes an image forming unit, and 200 denotes an image reading unit. Other symbols are directly cited in the description.
The image forming unit 100 includes a drum-shaped latent image carrier 111, and a charging roller 112 as a charging unit, a developing device 113, a transfer roller 114, and a cleaning device 115 are disposed around the image forming unit 100. A “corona charger” can also be used as the charging means. Further, an optical scanning device 117 that receives document information from the outside such as an image reading unit and performs optical scanning with the laser beam LB is provided, and “exposure by optical writing” is performed between the charging roller 112 and the developing device 113. To do.

  When forming an image, the image carrier 111, which is a photoconductive photosensitive member, is rotated at a constant speed in the clockwise direction, the surface thereof is uniformly charged by the charging roller 112, and the optical beam of the laser beam LB of the optical scanning device 117 is written. An electrostatic latent image is formed upon exposure to the image. The formed electrostatic latent image is a so-called “negative latent image”, and the image portion is exposed. The cassette 118 storing the transfer paper P is detachable from the main body of the image forming apparatus 100. When the transfer paper P is mounted as shown in the drawing, the uppermost sheet of the stored transfer paper P is fed by the paper supply roller 120. The leading edge of the fed transfer paper P is caught by the registration roller pair 119. The registration roller pair 119 feeds the transfer paper P to the transfer unit at the timing when the toner image on the image carrier 111 moves to the transfer position. The transferred transfer paper P is superimposed on the toner image at the transfer portion, and the toner image is electrostatically transferred by the action of the transfer roller 114. The transfer paper P to which the toner image is transferred is sent to the fixing device 116, where the toner image is fixed by the fixing device 116, passes through the conveyance path 121, and is discharged onto the tray 123 by the discharge roller pair 122. The surface of the image carrier 111 after the toner image has been transferred is cleaned by a cleaning device 115 to remove residual toner, paper dust, and the like. The latent image carrier 111 is a photoconductive photoconductor, and an electrostatic latent image is formed by uniform charging and optical scanning, and the formed electrostatic latent image is visualized as a toner image.

  In the image reading unit 200, the document 202 is placed on the contact glass 201, and the document 202 is illuminated by an illumination unit (not shown) mounted on the first traveling body 203 disposed below the contact glass 201. The reflected light from the document 202 is reflected by the first mirror 203 a of the first traveling body 203, and then reflected by the first mirror 204 a and the second mirror 204 b of the second traveling body 204 and guided to the reduction imaging lens 205. The image is formed on the line sensor 206.

When reading the longitudinal direction of the document, the first traveling body 203 moves to the right in the figure at a speed of V, and at the same time, the second traveling body 204 moves to the right at a speed 1/2 V that is half that of the first traveling body 203. To scan the entire document.
Normally, a document illumination device used for an image reading device requires a length substantially the same as the document width in order to illuminate a document. Therefore, as a method of using an LED as a document illumination device, a large number of LED elements are used. Use them in an array.
However, although LEDs have excellent characteristics as described above, since the absolute brightness of each element is insufficient for use as an illumination device of an image reading device, a low-speed reading device, It is mainly used for devices that emphasize compactness, and cold cathode fluorescent lamps are mainly used for high-speed reading devices and large devices.

In order to compensate for this problem, it is common to increase the amount of light in the LED array by using a large number of LED elements constituting the LED array. However, since the light diffuses widely, it is not very efficient. It goes against power saving. In addition, when a bullet-like LED with less diffusion is used, the efficiency is improved, but the directivity is high and unevenness occurs in the main scanning direction.
There is an example of a document illumination device that combines an LED array and a long lens for the purpose of improving light utilization efficiency (see, for example, Patent Document 1 and Patent Document 2). In these apparatuses, the efficiency of the light has been increased by converging the light of the LED on the sub-scan section of each LED.

However, when such a method is used, there is a problem that, as described in Patent Document 1, the central portion of the convergent light is bright, and light is diffused and rapidly darkened at a position off the center.
Of the light emitted from the LEDs, most of the light emitted at an angle with respect to the sub-scanning cross section is wasted. Therefore, if a large number of LEDs are not arranged, illuminance unevenness in the main scanning direction occurs.

Japanese Patent Laid-Open No. 11-232912 (2nd page, FIGS. 1 and 9) JP-A-8-111545 (Page 4, FIG. 3)

  An object of the present invention is to solve these problems. A light source unit in which a plurality of LEDs having a predetermined light distribution is arranged and a long lens that does not converge in the sub-scanning cross-sectional direction are appropriately arranged so that each LED is output. By converging the incident light not on the document surface position on the sub-scan section of each LED but on the document surface position having an angle in the main scan direction with respect to this sub-scan section, the light converges in the sub-scan section. In the main scanning direction, there is provided a manuscript illuminating device that has little loss due to light diffusion in the main scanning direction and less illuminance unevenness in the main scanning direction.

In the first aspect of the present invention, when a surface to be illuminated having a length and a width, the length direction is a main scanning direction, and the width direction is a sub-scanning direction, a plurality of light emitting elements are arranged in the main scanning direction. In a document illuminating device having a light source unit arranged in a row and a long lens disposed between the surface to be illuminated and the light source unit, the longitudinal direction of which coincides with the main scanning direction, light emission of each light emitting element When the light incident surface of the long lens is disposed in the vicinity of the surface, the surface to be illuminated is disposed at a predetermined distance from the light emitting surface of the long lens , and each light emitting element is regarded as a point light source The emitted light from each light emitting element becomes substantially parallel light in the sub-scan section including each light-emitting element after being emitted from the long lens, and the light is emitted from the position on the illuminated surface included in the sub-scan section. In a position separated by a predetermined distance in the main scanning direction It is characterized by having a convergent point.
According to a second aspect of the present invention, in the original illuminating apparatus according to the first aspect, the convergence angle of the light beam to be converged on the illuminated surface with respect to the sub-scanning section is a half-value angle in the light distribution of the light emitting element. It is characterized by being set within.

According to a third aspect of the present invention, in the original illuminating device according to the first or second aspect, the distance between the centers of the light emitting elements at both ends of the light source unit is larger than the length of the illuminated surface.
According to a fourth aspect of the present invention, in the document illuminating device according to any one of the first to third aspects, an interval between the light emitting elements closest to the center is P0. , N ≧ 1, and when the interval between any light emitting elements up to the light emitting element closest to the end is Pn,
Pn-1 ≧ Pn
0.2 ≦ Pn / P0 ≦ 1
It shall be the said to satisfy the relationship simultaneously.

According to a fifth aspect of the present invention, in the document illuminating device according to any one of the first to fourth aspects, the long lens is a lens having different curvatures in the main scanning section and the sub-scanning section. And
According to a sixth aspect of the present invention, in the document illuminating device according to the fifth aspect , the long lens has a non-circular cross section at least one of the light incident surface and the light exit surface of the main scanning section and the sub-scanning section. It is characterized by being.

According to a seventh aspect of the invention, there is provided an image reading apparatus using the document illumination device according to any one of the first to sixth aspects.
In the invention according to claim 8, said image forming apparatus using the image reading apparatus according to claim 7.

  According to the illuminating device of the present invention, since the light flux has a convergence point on the illuminated surface at the main scanning position away from the sub-scanning section at the light source position, a substantially uniform illuminance distribution is obtained in the main scanning direction in the reading region. Can do.

FIG. 1 is a side sectional view showing the basic concept of the illumination device of the present invention.
FIG. 2 is a plan view showing the basic concept of the illumination device of the present invention.
In both figures, reference numeral 1 denotes a point light source, 2 denotes a long lens, and 3 denotes a contact glass placed in front of the illuminated surface.
The light incident surface 2a of the long lens 2 is disposed in the vicinity of the light emitting surface of the point light source 1, and the illuminated surface is disposed at a position away from the light emitting surface 2b of the lens by a predetermined distance. The surface to be illuminated is made to coincide with the surface 3b (hereinafter referred to as the back surface) of the contact glass 3 opposite to the point light source.
The point light source 1 is a light source having a very small light emission point, such as an LED, and the light emission point size can be regarded as a point as compared to the paper width when an A4 size or the like is considered as an illuminated surface. .

As shown in FIG. 2, the long lens 2 is long in one direction and the cross section orthogonal to the longitudinal direction has the same lens shape in all positions as shown in FIG. . However, the long lens is also included in the case where the longitudinal direction is not linear, and thus the cross-sectional shape changes depending on the position. Regardless of the specific lens shape, such a long lens is also called a cylinder lens or a cylindrical lens.
Such an illuminating device is used in a digital copying machine or an image scanner. In that case, one direction of the document is made to coincide with the longitudinal direction of the long lens 2 and is brought into close contact with the back surface 3b of the contact glass 3. Since the illumination light is condensed into a line along the longitudinal direction, the entire document surface cannot be read simultaneously. Therefore, the document surface and the illumination device must be moved relatively along the other direction of the document. Here, the linear direction of illumination light is called a main scanning direction, and the relative movement direction is called a sub-scanning direction. FIG. 1 shows a sub-scan section. In the present invention, the term “sub-scan section” means an infinite number of sub-scan sections.

In this configuration, in the sub-scan section, the light emitted from the LED is made substantially parallel and illuminates the document surface. However, the light beam emitted in the direction shown by the broken line in FIG. 2 does not become a parallel light beam after being emitted from the long lens, but rather becomes a convergent light beam. This phenomenon is caused by the fact that the light beam crosses obliquely with respect to the long lens, so that the apparent curvature of the incident surface and the light exit surface for the light beam is increased and the distance between the light exit surfaces is increased. . In FIG. 2, θf is shown as the angle at which the convergence point exactly coincides with the surface to be illuminated (this angle is referred to as the convergence angle for convenience). Hereinafter, generally, an angle formed by a light beam emitted to a cross section perpendicular to the paper surface and the sub-scanning cross section is denoted by θ, and such a light beam is referred to as an oblique light beam.
As described above, according to this configuration, all the light beams emitted from the point light source are not substantially parallel to the document surface, but there are light beams that converge on the document surface. As the angle θ of the oblique light beam emitted from the point light source increases, the conjugate length with the point light source, which was initially infinity, gradually decreases, and finally converges on the original surface at θf. If θ becomes larger than the convergence angle θf, the convergence point enters the contact glass.

FIG. 3 is a diagram illustrating an example in which the light distribution of the point light sources is a uniform distribution.
FIG. 4 is a diagram showing the illuminance in the main scanning direction by a point light source with uniform distribution.
A distribution Q1 that emits uniform light energy in all solid angle directions within a range of 180 ° from the point light source is referred to as a uniform distribution.
The light emitted from the LED gradually changes to convergent light as the angle θ increases, in other words, as the distance from the front surface of the LED on the illuminated surface increases in the longitudinal direction. Assuming that the LED light distribution is uniform in all directions as shown in FIG. 3, the illuminance on the original surface gradually increases toward the end in the main scanning direction, and the convergence angle as shown in FIG. Two peaks such as corners are formed in the vicinity of θf. In this illuminance distribution, the flat part near the center part is narrow, and the width of the original that can be used as an illumination device cannot be made too large. However, such a light distribution Q1 cannot be obtained with a practical LED.

FIG. 5 is a diagram illustrating an example in which the light distribution of the point light source is a Lambertian distribution.
FIG. 6 is a diagram showing the illuminance in the main scanning direction by a Lambertian distribution point light source.
When the intensity distribution of the light energy emitted from the point light source is spherical Q2, it is called a Lambertian distribution. In the case of this distribution, the maximum energy is emitted in the direction normal to the surface of the light source. Assuming that the maximum energy radiation direction is θ = 0 °, the optical energy of the light beam emitted in the angular direction decreases as θ increases, and the maximum value is half (half value) at θh = 60 °. Decreases by a factor of four. θh = 60 ° is called a half-value angle of this distribution.
When a point light source having such a light distribution Q2 is used, the light intensity decrease due to the light distribution characteristic and the light intensity increase due to the convergence of the lens cancel each other, and the illuminance at the peak portion decreases compared to FIG. .
In this illuminance distribution, the flat portion near the center is further widened, and the emitted light of the LED is wide in the main scanning direction and can be used effectively.
When a plurality of such LEDs are arranged, since the effective illumination range of each LED is wide in the main scanning direction as described above, even with a small number of LEDs, illumination with less unevenness in the main scanning direction is possible.
Further, at this time, two peaks near both ends of each LED in the main scanning direction are connected to each other, and as a result, an illuminance distribution having high convergence in the sub scanning direction can be formed at any position in the main scanning direction. .
As another advantage of using the configuration of the present invention, the configuration of the present invention does not have a converging action on the sub-scan section as described above. For this reason, the curvature is gentler than that of a lens having a converging effect, and therefore the NA can be set large, so that the amount of light that can be taken in from the LED can be increased.

FIG. 7 is a cross-sectional view showing the configuration of the first embodiment. FIG. 4A shows the state of the light beam on the sub-scanning section, and FIG. 5B shows the state of the oblique light beam having the convergence angle θf = 45 °.
FIG. 8 is an irregular plan view showing the configuration of the first embodiment.
FIG. 9 is a diagram showing the illuminance distribution in the main scanning direction of the illuminated surface according to the configuration of the first embodiment.
The specification of a present Example is shown.
Long lens_A cross-sectional shape (sub-scanning cross-sectional radii are R1 on the incident surface 2a side and R2 on the outgoing surface 2b side)
R1 = 10
R2 = −2.887 (ellipsoidal, conical multiplier K = −0.837)
Center thickness: 7.2 (mm)
Width in the main scanning direction: 50 (mm)
Material: nd = 1.491, νd = 57.2
LED_A
Light distribution: Lambert distribution (Q2)
Light intensity distribution on the light emitting surface: Uniform Light emitting surface size: 1 (mm) x 1 (mm)
Quantity: 1 (piece)
Luminous efficiency: 1 (W)
Contact glass Center thickness: 3.2 (mm)
Material: nd = 1.517 νd = 64.2
Positional relationship LED-long lens 2a surface spacing: 1 (mm)
Long lens 2b surface-contact glass: 10 (mm)
Inclination of the optical axis of the long lens with respect to the normal of the contact glass surface: 30 degrees Illuminated surface (document surface): The back surface of the contact glass

As shown in FIGS. 7A and 7B, the light beam is set to be parallel light in the sub-scan section, and the lens and other specifications are selected so as to converge on the illuminated surface at θf = 45 °. . In this embodiment, θf <θh.
FIG. 8 shows a view of the long lens 2 and the luminous flux as seen from a direction perpendicular to the optical axis, and a contact glass 3 as seen from a direction perpendicular to the illuminated surface 3b.
In FIG. 7B, the oblique luminous flux converges from one point to one point, but the actual LED has a size of 1 mm square as shown in the specification. As can also be estimated from the figure, since the imaging magnification on the illuminated surface is larger than the same magnification, the width of the convergent light in the sub-scanning direction on the illuminated surface is larger than 1 mm.
In FIG. 8, the oblique light beam emitted at θf = 45 ° converged to a position 16.5 mm from the center position on the illuminated surface. When a region having a width of 1 mm in the sub-scanning direction on the surface to be illuminated is set as the reading region S, the illuminance distribution in this region is obtained as shown in the graph of FIG. The graph shows the result of integration in the sub-scanning direction with respect to the width of 1 mm. The unit of the portion expressed as the illuminance on the vertical axis is substituted by the energy unit mW / m ² . In the main scanning direction, a length of 45 mm is plotted with respect to a long lens having a length of 50 mm. It can be seen that the light emitted from the LED can be used without vainly diffusing in the main scanning direction.
In this example, an oblique light beam having a light beam incident angle of about 45 ° with respect to the long lens is used. In general, the larger the incident angle, the larger the light loss due to surface reflection. Although it is possible to add an antireflection film to compensate for this, high costs are inevitable. Moreover, since the radiant energy at the angle outside the half-value angle θh decreases rapidly, it is not a good idea to select the angle outside the half-value angle θh as the convergence angle θf.

FIG. 10 is an irregular plan view showing the configuration of the second embodiment.
FIG. 11 is a diagram showing the illuminance distribution in the main scanning direction of the illuminated surface according to the configuration of the second embodiment.
FIG. 12 is a diagram showing the illuminance distribution in the sub-scanning direction of the illuminated surface according to the configuration of the second embodiment.
The present embodiment has the same configuration as that of the first embodiment except that the length of the long lens in the main scanning direction is set to 100 (mm) and the number of light sources is increased. The number of LED_A was 15 and arranged at a pitch of 5 mm. Accordingly, the distance between the centers of both ends of the light source is 70 mm, and illumination is performed from the outside having a width of 45 mm in the main scanning direction.
The illuminance distribution in the main scanning direction is almost flat over the entire width, and can be used as it is as a reading width.
The illuminance distribution in FIG. 12 is obtained by plotting the center of the 45 mm width in the main scanning direction by 30 mm in the sub scanning direction. The reading area 1 mm in the sub-scanning direction is the peak position in FIG. 12, and it can be seen that the light is well collected.

FIG. 13 is a diagram showing an example in which the light distribution of the light source is a cosine square distribution.
FIG. 14 is a diagram showing an illuminance distribution in the main scanning direction by a point light source having a cosine square distribution.
The present embodiment is configured with the same specifications as in the first embodiment, except that the light distribution is changed from LED_A having a Lambertian distribution Q2 to LED_B having a cosine square distribution Q3.
The cosine square distribution Q3 is a distribution in which the light energy emitted in the direction inclined by the angle θ with respect to the normal line of the light emitting surface decreases at a ratio of cos ² θ with respect to that in the normal line direction. In the case of this distribution, the light energy at θh = 45 ° is one half (half value) of that in the normal direction. Therefore, in this embodiment, the convergence angle θf coincides with the half-value angle θh.
It can be seen that even when an LED having a strong central light intensity such as LED_B is used, the emitted light can be used effectively by matching the convergence effect and the light distribution of LED_B.

FIG. 15 is a diagram illustrating the illuminance distribution in the main scanning direction of the surface to be illuminated according to the configuration of the fourth embodiment.
FIG. 16 is a diagram showing the illuminance distribution in the sub-scanning direction of the illuminated surface according to the configuration of the fourth embodiment.
The present embodiment has the same configuration as that of the second embodiment, and uses LED_B as an arrayed LED.
The illuminance distribution in FIG. 16 is obtained by plotting the center of the 45 mm width in the main scanning direction by 30 mm in the sub scanning direction. The reading position of 1 mm in the sub-scanning direction is the peak position in FIG. 16, and it can be seen that light is well collected.

FIG. 17 is a perspective view of the configuration of the fifth embodiment.
FIG. 18 is a plan view of a long lens used in Example 5.
FIG. 19 is a diagram showing the illuminance distribution in the main scanning direction of the illuminated surface according to the configuration of the fifth embodiment.
FIG. 20 is a diagram showing the illuminance distribution in the sub-scanning direction of the illuminated surface according to the configuration of the fifth embodiment.
In this embodiment, the illuminance at the edge of the document surface is increased without increasing the number of LEDs. The basic configuration is the same as in Example 2, the light exit surface 2b of the long lens has a curvature of 500 mm in the main scanning direction, the main scanning direction cross section has a concave lens shape, and the sub scanning direction cross section is the same. A long lens_B that is a convex lens having a curvature was used.
In the illuminance distribution diagrams in the main scanning direction obtained in Example 2 and Example 4 (FIGS. 11 and 15), the illumination surface is illuminated with a plurality of light sources extending to 70 mm with respect to the illuminated surface width of 45 mm. Regardless, there is a slight decrease in illuminance at both ends of the width. This can be improved by changing the pitch of the array or electrically correcting it. This embodiment is shown as one method for the improvement. That is, by providing a curvature as shown in FIG. 18 in the longitudinal direction of the light exit surface of the long lens, the illuminance reduction portion can be pushed outward, and the entire range of a desired document width (45 mm in this example). An almost constant illuminance distribution can be obtained over a wide range.
As another method of the above improvement, a curved surface of the light incident surface or light exit surface in either the main scanning direction or the sub-scanning direction (or both) may be used, and a quadratic curve whose cross-section in each direction is other than a circle ( For example, it may be configured to be an ellipse, a parabola, or the like. When advanced design and manufacture are possible, a higher order even order curve such as a quartic curve can be used. Such a curve is called a non-circular curve for convenience.

FIG. 21 is a diagram showing the illuminance distribution in the main scanning direction of the illuminated surface according to the configuration of the sixth embodiment.
FIG. 22 is a diagram showing the illuminance distribution in the sub-scanning direction of the illuminated surface according to the configuration of the sixth embodiment.
The configuration of this example is the same as that of Example 1 except for the long lens. The specification of long lens _C used for a present Example is shown.
R1 = 20 (mm)
R2 = −3.8 (mm) (ellipsoidal, conical multiplier K = −0.484)
Center thickness: 10 (mm)
Width in the main scanning direction: 50 (mm)
Material: nd = 1.491, νd = 57.2
It is.
In FIG. 22, a curve G1 having a depression near the center of the two curves indicates the illuminance distribution in the sub-scanning direction at the center in the main scanning direction of FIG. A curve G2 having a peak near the center shows the illuminance distribution in the sub-scanning direction at the right peak position of the two peaks in FIG.

FIG. 23 is a diagram showing the illuminance distribution in the main scanning direction of the illuminated surface according to the configuration of the seventh embodiment.
FIG. 24 is a diagram showing the illuminance distribution in the sub-scanning direction of the illuminated surface according to the configuration of the seventh embodiment.
In this embodiment, the long lens _C shown in Embodiment 6 is applied to the configuration of FIG.
When the number of light sources is one, as shown in FIG. 21, peak values of about 1.5 times the central portion appeared near both ends, but by using a plurality of light sources, as shown in FIG. In other words, a plurality of peak values are connected and flattened as a whole.

FIG. 25 is a diagram illustrating an example of the interval between the light emitting elements of the light source unit.
In the same figure, the code | symbol P shows the light emitting element space | interval.
The arrangement interval of the plurality of light emitting elements is set such that the interval between the light emitting elements closest to the center is P0, n ≧ 1, and the interval between arbitrary light emitting elements to the light emitting element closest to the end is Pn.
Pn-1 ≧ Pn
0.2 ≦ Pn / P0 ≦ 1
It is configured to satisfy the above relationship at the same time.
Even in the illuminance distribution shown in FIG. 23, a slight decrease in illuminance is observed at both ends in the main scanning direction. This is considered to be because the main scanning direction end of the illuminated surface receives only the light beam from the center side of the position. In order to solve this problem, the above configuration is adopted.
In the embodiments so far, the target is to make the illuminance of the illuminated surface uniform. However, depending on the characteristics of the reading optical system, there may be a shortage of peripheral light amount called so-called shading. This configuration can also be used to obtain a lighting device that takes shading correction into account. As described above, by increasing the arrangement density of the light emitting elements toward the end in the main scanning direction, the peripheral light amount is made larger than the central portion, and as a result, the light amount that has passed through the reading optical system is made uniform.

The specific example of arrangement | positioning which makes the illumination intensity distribution in a to-be-illuminated surface uniform is shown.
The total number of light emitting elements is 15, and the arrangement interval P0 of the light sources closest to the center is 6.2 mm.
From the next light emitting element toward the end, the interval is reduced by 0.3 mm each up to the second one, and the outside is successively narrowed by 0.4 mm. Therefore, the distance between the outermost (seventh) light emitting element and the innermost light emitting element is 4 mm, and the distance between the centers of the outermost light emitting elements is 72.2 mm, which is longer than the length of the illuminated surface (45 mm). . As a result, the edge in the main scanning direction of the surface to be illuminated receives light from a light source having a high arrangement density and also receives light from the outside as well as from the center, thereby eliminating peripheral illuminance reduction. The
In the above description, the length of the surface to be illuminated has been discussed as 45 mm. However, when actually applied to a reading device or the like, measures such as increasing the number of light emitting elements so as to correspond to a desired document width. Take.

Next, a light source that can be used in the present invention will be described.
In the present invention, the light source is most suitably a light emitting diode (LED). Among them, it is preferable to use a white LED in order to be able to handle reading of any document.
There are several types of white LEDs. One of them is a one-chip type white LED using a phosphor. A light emitting unit called a chip is sealed in a transparent enclosing member mixed with a YAG phosphor. The chip emits blue light made of InGaN. Thereby, when the chip emits blue light, the phosphor is simultaneously excited to emit yellow fluorescence. Since blue and yellow are complementary to each other, when both go out together, they are recognized as white light.
As another type, there is a white light-emitting diode that does not use a phosphor and uses two or more chips that emit different colors and emits white light by color mixture. The plurality of chips are arranged on the same surface, and are combined to be recognized as white when all the emission colors are mixed.
For example, in the case of two chips, chips that emit blue and yellow light are used as described above. In the case of three chips, chips that emit red, green, and blue corresponding to so-called three primary colors are used.

FIG. 27 is a diagram for explaining a transmissive document reading apparatus.
In the figure, reference numeral 5 denotes an image pickup optical system, 6 denotes a CCD line sensor as an image pickup element, 7 and 7 'denote first and second field lenses, and 8 denotes a flare cut plate.
In the above description, the image forming apparatus shown in FIG. 26 has been taken as an example. However, as shown in the description of the technical field, the present invention is a technique that can be applied to a digital laboratory.
In general, in an image forming apparatus, a sheet-like original or a book-like original is used as an original, and is usually read by a reflection method. In some cases, a transparent original for OHP may be copied, but in this case as well, it is common to read the reflection with a white reflector on the back of the original.
On the other hand, in a digital laboratory, a transparent film-like document is usually read in a transparent manner.
FIG. 27 shows a cross section in the main scanning direction. In the figure, the luminous flux from the LED 1 passes through a long lens 2 and reaches a film 3 as a document surface. The film 3 is a manuscript in a format in which a photographic film is mainly used, such as a negative color film, and a color image is obtained as transmitted light.

The light beam that has passed through the film is finally incident on a CCD line sensor 6 as an image pickup device and recorded as image data or transferred to another. The image sensor is not limited to a CCD, and any element known as a line sensor can be used.
In order to read an image accurately, a lens called a field lens having the same positive power in both the main scanning direction and the sub-scanning direction is usually placed in front of the film 3. Since the field lens only needs to cover the length in the main scanning direction, the sub-scanning direction need only be large enough to cover the reading width as long as it includes the optical axis.
The light beam reaching the first field lens 7 is subjected to an action such that the field lens 7 becomes a parallel light beam perpendicular to the surface of the film 3.
The parallel light beam transmitted through the film 3 enters the second field lens 7 ′. This parallel light beam is subjected to the action of converging at the center of the entrance pupil of the imaging optical system 5 by the field lens 7 '. The light beam that has passed through the imaging optical system becomes divergent light, enters the CCD line sensor 6, and is read in the main scanning direction.
The power of the field lenses 7 and 7 'can be designed to be equal to each other, but basically they need not be the same.

The imaging optical system 5 is set so that the film 3 and the CCD line sensor 6 are in a conjugate relationship.
Usually, the optical axes of the two field lenses 7 and 7 ′ and the imaging optical system 5 are matched. And LED1 is arrange | positioned on the optical axis. The central portion of the CCD line sensor 6 is also substantially coincided with the same optical axis.
Although not shown, the film 3 includes a portion that is desired to be illuminated (temporarily called an effective portion) and a portion that is not desired to be illuminated (temporarily called an unnecessary portion). In general, in the case of a negative film, the amount of transmitted light in unnecessary portions is large. If this is incident on the field lenses 7 and 7 ′ or the image pickup optical system 5 as it is, stray light (so-called flare light) is generated and a desired image is obtained. May overlap. In order to avoid this problem, a flare cutting means 8 for blocking a light beam (referred to as an unnecessary light beam) that should go to an unnecessary portion is provided on the exit surface of the long lens 2. That is, an unnecessary light beam is blocked as much as possible within a range that does not block an effective portion of a light beam (referred to as an effective light beam) even if an installation error occurs in the vicinity of both ends in the longitudinal direction (main scanning direction) of the long lens 2. The flare cutting means 8 is installed in

The flare cutting means 8 includes a front surface and a rear surface of the field lens 7, a front surface and a rear surface of the film 3, a front surface and a rear surface of the field lens 7 ′, a front surface and a rear surface of the imaging optical system 5, and a front surface of the CCD line sensor 6. (Indicated by a one-dot chain line and a dotted line) is the same in principle in that the effective light flux is guided to the effective area of the line sensor, but is greatly different in terms of generation of flare light. If importance is attached to accuracy, it is preferable to place the light flux as large as possible, that is, in the range from the front surface of the lens 7 to the rear surface of the field lens 7 ′. However, since flare light is often generated by irregular reflection in the lens or the like, it can be said that the position before entering the first field lens as much as possible, that is, the front surface of the field lens 7 (shown by a broken line in the figure) is the best position. The flare cutting means is not limited to any one of the above, and the light shielding effect can be further enhanced by placing it at a plurality of places.
At each position, as in the case described above, the arrangement positions are arranged so as to block the unnecessary light beam as much as possible within a range that does not block the effective light beam even if an installation error or the like occurs.

As the flare-cut means 8, a plate-like member may be disposed when it is installed at the position of the long lens, and the light exit surface (the sub-scanning direction becomes a curved surface) of the long lens is flexible. An opaque material may be pasted or painted with a light-shielding opaque material. The same applies to the field lenses 7 and 7 '.
When installing at the position of the film 3, for example, a holding frame (not shown) for holding the film 3 is also used as a so-called mask to shield unnecessary light flux. Good.
It is not preferable to install flare cutting means on the front and rear surfaces of the imaging optical system or just before the line sensor. This is because the size of the light beam is small and after the flare has already occurred in the field lens or the like. The case where it is placed on the rear surface of the second field lens is also not preferable because it will be after the flare has already occurred.

The use of Example 8 is shown.
Long lens R1 = 10mm
R2 = −2.88 (ellipsoidal, conical multiplier K = −0.837)
Center thickness: 7.2mm
Main scanning direction width: 15mm
Material: nd = 1.491 νd = 57.2
LED
Light distribution: Lambert distribution Intensity distribution on light emitting surface: Uniform Light emitting surface size: 1 mm x 1 mm
Quantity: 1 piece Efficiency: 1W
Contact glass Center thickness: 3.2 mm
Material: nd = 1.517 νd = 64.2
Positional relationship LED-long lens R1 surface spacing: 1mm
Long lens R2 surface-film surface: 13 mm
Illuminated surface (film surface) size 24mm (main scanning direction) x 36mm (sub-scanning direction)
With respect to the above configuration, the flare-cut plate 8 is sized so as to cut a light beam outside the surface of 24 mm on the illuminated surface.

28 and 29 are diagrams showing the illuminance distribution according to the eighth embodiment. FIG. 28 shows the distribution in the sub-scanning direction, and FIG. 29 shows the distribution in the main scanning direction.
These illuminances are calculated by subdividing the effective range of the illuminated surface into 1 mm meshes in the main scanning direction and the sub-scanning direction, tracing 1 million rays, and calculating the illuminance with the number of rays incident on each mesh. It is what. 9 shows the illuminance distribution in the sub-scanning direction in the sub-scanning section including the light source, and FIG. 10 shows the illuminance distribution in the main scanning section passing through the peak value of the graph in FIG. It can be seen that there is almost no illuminance unevenness in the main scanning direction.

It is a sectional side view which shows the basic concept of the illuminating device of this invention. It is a top view which shows the basic concept of the illuminating device of this invention. It is a figure which shows the example whose light distribution of a point light source is uniform distribution. It is a figure which shows the illumination intensity of the main scanning direction by the point light source of uniform distribution. It is a figure which shows the example whose light distribution of a point light source is a Lambert distribution. It is a figure which shows the illumination intensity of the main scanning direction by the point light source of Lambert distribution. 1 is a cross-sectional view showing a configuration of Example 1. FIG. 3 is an irregular plan view showing the configuration of Example 1. FIG. FIG. 3 is a diagram illustrating an illuminance distribution in a main scanning direction of an illuminated surface according to the configuration of the first embodiment. 6 is an irregular plan view showing the configuration of Example 2. FIG. FIG. 10 is a diagram illustrating an illuminance distribution in a main scanning direction of an illuminated surface according to the configuration of Example 2. FIG. 6 is a diagram showing an illuminance distribution in a sub-scanning direction of a surface to be illuminated with the configuration of Example 2. It is a figure which shows the example in which the light distribution of a light source is a cosine square distribution. It is a figure which shows the illumination intensity distribution of the main scanning direction by the point light source of cosine square distribution. It is a figure which shows the illumination intensity distribution of the main scanning direction of the to-be-illuminated surface by the structure of Example 4. FIG. It is a figure which shows the illumination intensity distribution of the subscanning direction of the to-be-illuminated surface by the structure of Example 4. FIG. 10 is a perspective view of a configuration of Example 5. FIG. 6 is a plan view of a long lens used in Example 5. FIG. FIG. 10 is a diagram showing an illuminance distribution in the main scanning direction of an illuminated surface with the configuration of Example 5. FIG. 10 is a diagram illustrating an illuminance distribution in a sub-scanning direction of a surface to be illuminated with the configuration of Example 5. It is a figure which shows the illumination intensity distribution of the main scanning direction of the to-be-illuminated surface by the structure of Example 6. FIG. It is a figure which shows the illumination intensity distribution of the subscanning direction of the to-be-illuminated surface by the structure of Example 6. FIG. It is a figure which shows the illumination intensity distribution of the to-be-illuminated surface by the structure of Example 7 in the main scanning direction. It is a figure which shows the illumination intensity distribution of the subscanning direction of the to-be-illuminated surface by the structure of Example 7. FIG. It is a figure which shows the example of the space | interval of the light emitting element of a light source unit. 1 is a schematic diagram of an image forming apparatus having an image reading apparatus. It is a figure for demonstrating a transmissive | pervious original reading device. It is a figure which shows the illumination intensity distribution by Example 8. FIG. It is a figure which shows the illumination intensity distribution by Example 8. FIG.

Explanation of symbols

1 Light source 2 Long lens 3 Contact glass (film)
5 Imaging optical system 6 CCD line sensor 7, 7 'Field lens 8 Flare cut means

Claims (8)

A surface to be illuminated having a length and a width; a light source unit in which a plurality of light emitting elements are arranged in the main scanning direction when the length direction is a main scanning direction and the width direction is a sub scanning direction; In a document illumination device having a long lens arranged between an illuminated surface and the light source unit and having a longitudinal direction coincident with the main scanning direction,
The light incident surface of the long lens is disposed in the vicinity of the light emitting surface of each light emitting element, and the illuminated surface is disposed at a predetermined distance from the light emitting surface of the long lens ,
When each light emitting element is regarded as a point light source, the light emitted from each light emitting element becomes substantially parallel light in the sub-scan section including each light-emitting element after being emitted from the long lens , document illumination apparatus characterized by comprising a converging point at a position a predetermined distance away in the main scanning direction from the position on the surface to be illuminated included.   2. The document illuminating apparatus according to claim 1, wherein a convergence angle of the light beam to be converged on the illuminated surface with respect to the sub-scanning section is set within a half-value angle in a light distribution of the light emitting element. Document illumination device.   3. The document illumination device according to claim 1, wherein a distance between centers of light emitting elements at both ends of the light source unit is larger than a length of the illuminated surface. 4. The document illumination device according to claim 1, wherein an interval between the plurality of light emitting elements is P 0, an interval between the light emitting elements closest to the center is set to n ≧ 1, and is at the end. When the interval between any light emitting elements up to a near light emitting element is Pn,
Pn-1 ≧ Pn
0.2 ≦ Pn / P0 ≦ 1
A document illumination device characterized by satisfying the above relationship at the same time. 5. The document illuminating apparatus according to claim 1, wherein the long lens is a lens having different curvatures in a main scanning section and a sub-scanning section . 6. The document illuminating apparatus according to claim 5 , wherein the long lens has a non-circular cross section at least one of a light incident surface and a light exit surface of a main scanning section and a sub-scanning section. . An image reading apparatus using the document illumination device according to any one of claims 1 to 6. An image forming apparatus using the image reading apparatus according to claim 7 .

Images