JPS61292472A - Light quantity adjusting structure - Google Patents

Abstract

PURPOSE:To make flat a waveform of shading and to eliminate an error in a difference of the gradation, specially in a half tone by hintercepting a part of irradiated light and successively providing slits inclined with a prescribed angle with respect to a longitudinal direction of a light shielding plate for making the quantity of irradiated light for an object uniform. CONSTITUTION:An optical reader consists of a fluorescent tube 2 for irradiating an original 1, a reading element 3, a lens 4 for collecting reflecting light on the original surface and forming an image on a reading element 3, a light shielding plate 7 which is disposed between the original 1 and the fluorescent tube 2 and intercepts a part of the quantity of light of the fluorescent tube 2 of the like. The light plate 7 has slits 8 for passing light which are inclined by a prescribed angle alpha in a longitudinal direction and successively disposed. The slits 8 are constituted so as to constantly pass straight lines L intersecting at right angles longitudinally of the light shielding plate 7 through two slits 8 and the light incressantly and successively passes through any slit 8 in the longitudinal direction of the light shielding plate 7. The slit 8 is constituted so as to have an aperture area large in both ends and small in a center section corresponding to the light quantity distribution of the fluorescent tube. By using the light shielding plate 7, a part of the light in the vicinity of the central section of the fluorescent tube 2 is intercepted and the irradiating light is made flat by a shading effect.

Description

[Detailed Description of the Invention] [Summary] A light shielding plate provided to equalize the amount of light irradiated from a light source to a subject is provided with continuous inclined slits.

[Industrial application field]

The present invention relates to the structure of a document reading section in an optical reading device such as a facsimile machine.

For example, in optical reading devices such as facsimile machines,
In addition to adjusting focus, document reading width, etc., shading is also available to equalize the amount of light irradiated onto the document.
) corrections are being made.

Such shading correction needs to be performed accurately, and there is a desire to establish a highly accurate method.

[Conventional technology]

FIG. 4 is a perspective view showing the basic configuration of an optical reading device, FIG. 5 is a graph showing the light intensity distribution of a fluorescent tube, FIG. 6 is a side view showing the configuration of a conventional optical reading device, and FIG. ) (b) is a plan view of a conventional light shielding plate and a graph showing the shading waveform, FIG. 8(C) (d+ is an enlarged view of part B in FIG. bl is a plan view showing another example of the light shielding plate.

゛ As shown in FIG. 4, an optical reading device such as a facsimile machine includes a fluorescent tube 2 that illuminates a document 1, a reading element 3,
It is composed of a lens 4 that condenses light reflected from the surface of the document and forms an image on the reading element 3.

As shown in Figure 5, the fluorescent tube 2 is high in the center (bright <)
, there is a light intensity distribution characteristic that becomes lower (darker) toward both ends.

When reading is performed in this state, the read image signal of the reading element 3 appears in a form similar to the light intensity distribution of the fluorescent tube 2.

Therefore, it is necessary to correct this amount of light and make the amount of light irradiated onto the original 1 uniform.

For this purpose, conventionally, as shown in FIG.
This was done by providing the lens between the document 1 and the fluorescent tube 2, or between the document 1 and the lens 4 (not shown).

The correction method shown in FIG. 6 will be explained below. As shown in FIG. 7(a), the light-shielding plate 5a is provided with a light-transmitting slit 6 having an opening area that is large at both ends and small at the center, corresponding to the light intensity distribution of the fluorescent tube. By using the light shielding plate 5a, a part of the light near the center of the fluorescent tube 2 is shielded, and the irradiated light is flattened by a shading effect as shown in FIG. 7(b). be.

Another example of a light-shielding plate is shown in FIG. 8. In the light-shielding plate 5b shown in FIG. The pitch is changed as follows (arrow a < arrow b).

The light-shielding plate 5C shown in FIG. 2B has a light-shielding portion 5c' formed in a shape opposite to the light intensity distribution of the fluorescent tube 2.

Like the light shielding plates 5b and 5a, the amount of light passing through the light shielding plates 5b and 5C can be decreased in the center and increased toward the ends.

In addition to such a mechanical correction method, there is also a correction method that automatically sets the read level (slice level treated as a signal) electrically, although detailed explanation will be omitted.

However, electrical methods require expensive electrical circuits for correction and are not often used.

[Problem that the invention seeks to solve]

As explained above, the amount of light is corrected, but in this case, as shown in FIG. It becomes convex and concave at the light blocking part.

For this reason, when a facsimile apparatus has a halftone reading function, a tone difference appears in the read signal even when there is no halftone tone difference in the document 1 with sawtooth irradiation light.

Then, when this read signal is recorded by the receiving section, there is a problem in that it appears as vertical stripes.

[Means for solving problems]

FIG. 1 is a perspective view showing the principle of the light amount adjustment structure of the present invention.

In the present invention, light emitted from a light source (fluorescent tube) 2 is irradiated onto a subject (original) 1, and reflected light from the subject 1 is collected through an optical system including a lens 4 and read. A light shielding plate is provided between the light source 2 of the optical reading device equipped with a reading means for forming an image on the element 3 and the subject 1, and blocks part of the irradiated light to equalize the amount of irradiated light to the subject. A slit 8 is continuously provided which is inclined at a predetermined angle with respect to the longitudinal direction of the slit 7.

[Effect]

In other words, the light-transmitting slits of the light-shielding plate are inclined at a predetermined angle in the longitudinal direction of the light-shielding plate and are provided continuously, so that a portion of the light is always irradiated onto the document surface no matter where the light-shielding plate is located. The shading waveform becomes smooth and uneven.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

Figure 2(a) +b+Vt is a graph showing a plan view and shading waveform of the light shielding plate applied to the light amount adjustment structure of the present invention, and Figure 2(C) is an enlarged view of part A in Figure 2(a) and a graph showing the shading waveform. FIG. 3 is a graph showing a plan view of a light shielding plate and a shading waveform of another example.

In the figure, 7.9 is a light shielding plate, and 8.10 is a slit. Identical parts are designated by the same reference numerals throughout the figures.

As explained in FIG. 1, the optical reading device includes a fluorescent tube 2 that irradiates the document l, a reading element 3, a lens 4 that collects light reflected from the surface of the document and forms an image on the reading element 3. The light shielding plate 7 is provided between the document 1 and the fluorescent tube 2 to block part of the light from the fluorescent tube 2.

As shown in FIG. 2(a), the light shielding plate 7 is provided with a series of slits 8 for passing light that are inclined at a predetermined angle (arrow α) in the longitudinal direction thereof.

The slits 8 are configured so that a line perpendicular to the longitudinal direction of the light shielding plate 7 always passes through two slits 8, as shown in the same figure (C1).

In other words, the light passes through one of the slits 8 continuously without any break in the longitudinal direction of the shielding plate 7.

The slit 8 has an opening area that is large at both ends and small at the center, corresponding to the light intensity distribution of the fluorescent tube, as shown in FIG. By using the light blocking plate 7, a part of the light near the center of the fluorescent tube 2 is blocked, and the irradiated light is flattened by a shading effect as shown in FIG.

In this case, as explained in FIG.
Since the shading waveform passes through any of the slits 8 continuously without any break in the longitudinal direction, the shading waveform as shown in the same figure is an extremely flattened waveform compared to the conventional waveform explained in Fig. 7 etc. Become.

Another example of a light shielding plate is shown in FIG. 3, but the light shielding plate 9 shown in this example has slits 10 with the same opening area, similar to the light shielding plate 5b described in FIG. 8(a). The slits IO are provided at different pitches (arrow a and arrow b) so that both ends are thick and the center is coarse, and the shading waveform is as shown in figure 2 (b ) is the same as
It has the same effect.

Although the above explanation was made by providing a light shielding plate between the fluorescent tube and the original, it goes without saying that the same effect can be achieved even if the light shielding plate is provided between the original and the lens.

〔Effect of the invention〕

As explained above, by applying the light amount adjustment structure of the present invention to an optical reading device, the shading waveform is flattened, errors in gradation differences in halftones in particular are eliminated, and image signals are stabilized, etc. The effect on the top is extremely large.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the principle of the light amount adjustment structure of the present invention, FIG. (C1 is an enlarged view of part A in the same figure (al) and a graph showing the shading waveform. Figure 3 is a plan view of the light shielding plate of another embodiment and a graph showing the shading waveform. Figure 4 is the basic configuration of the optical reading device. FIG. 5 is a graph showing the light intensity distribution of the fluorescent tube. FIG. 6 is a side view showing the configuration of a conventional optical reader. FIGS. Graphs showing the top view and shading waveforms, Figures 7(C) and 7(d) are graphs showing an enlarged view of part B of the same figure (al) and shading waveforms, and Figures 8(a) and (b) are graphs showing the shading waveforms of other light shielding plates. 1 is a plan view showing an example. In the figure, 1 is a document, 2 is a fluorescent tube, 3 is a reading element,
4 is a lens, 5a to 5c, 7.9 is a light shielding plate, and 6.8.10 is a slit. Figure 2 The sound of the same figure (of) and the figure and side L-de A 7; Pseudo" Li ■ 4 and j and see 7° force Shiba W Shi L hanging 1 dare 7th 3rd rod 4 Kurafu Kaya that shows this part of the attack power W 5 Figure Fushiki Izumi 0 尤竿舒" Toilet Meditation Exhibition Appeal 1 Toilet 1 Figure 6 Town

Claims (1)

[Scope of Claims] Light emitted from a light source (2) is irradiated onto a subject (1), reflected light from the subject (1) is focused through an optical system including a lens (4), and a reading element is provided. (3) is provided between the light source (2) of the optical reading device equipped with a reading means for forming an image on the object (1) and the object (1), and blocks a part of the irradiated light to A light intensity adjustment structure, in which a light shielding plate (7) that equalizes the amount of irradiated light is provided with continuous slits (8) that are inclined at a predetermined angle with respect to the longitudinal direction of the light shielding plate (7). .