JPH06194753A - Document density detecting device - Google Patents

Abstract

PURPOSE:To provide a document density detecting device allowing a precise and stable document density detection regardless of the character density of a document. CONSTITUTION:In a document density detecting device for lighting a document surface 1 by a light source and receiving the reflected light to detect the density of the document surface 1, a light source for lighting the document surface 1 in a fine area A is set, a light receiver 2 allowing the collection of the reflected light from an area B wider than the fine area is arranged, and a lens 4 for collecting the light to the light receiver 2 is provided between the document surface 1 and the light receiver 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the density of an original in an office machine such as a copying machine.

[0002]

2. Description of the Related Art A conventional document density detecting device of this type is used in office machines such as copying machines. FIG. 8 shows a copying machine using a document density detecting device. In FIG. 8, 101 is a green fluorescent light source that illuminates the original, 102 is a reflective shade that efficiently irradiates the original 104 with the light flux from the light source, and 103 is the original placing glass. Reference numeral 105 is the reflected light of the original, and 106 is an imaging lens. 107 is a mirror, 108 is a document density detecting device,
Reference numeral 109 is a photosensitive drum, and 110 is a document feeder.

As a light source for illuminating a document, which is a conventional example of this copying machine, a green light-emitting fluorescent lamp which has high luminous efficiency and generates little heat is used.

FIG. 9 shows a first conventional example of the document density detecting device 108.

In this conventional example, the original surface 51 is illuminated with a tungsten bulb 55 from an oblique direction, the reflected light from the original surface 51 is received, and the density of the original is detected from the amount of light.

A light receiver 52 for receiving the reflected light from the document surface 51.
Between the document surface 51 and the light receiver 52.
Is arranged, and the color filter 53 is used as the original density detecting device 1.
The spectral sensitivity of 08 is set to a spectral characteristic that substantially matches the spectral sensitivity of the copying machine.

The reflected light from the document surface 51 was applied to a light receiver 52 arranged at a position facing the document surface 51. The light receiver 52 received the reflected light beam from the illuminated portion of the document. Therefore, the amount of light applied to the light receiver 52 is a reflected light flux from a wide range of the illumination portion of the document surface 51, and the amount of reflected light is a value related to the average reflection density for this illumination area.

To make a copy here, first, the original 10
4 is placed on the document feeder 110 to start copying. The original 104 is taken into the original feeding device 110,
Although it is directed to the original placing glass 103, it passes near the original density detecting device 108 immediately before this. At this time, the green fluorescent lamp light source 101 of the document density detecting device 108 is turned on, the reflected light from the document 104 is received by the light receiver 52 through the color filter 53, and the density of a part of the document 104 passing therethrough is detected. Then, the original 104 is further fed onto the original placing glass 103.

When it is fed onto the document placing glass 103, the green fluorescent lamp light source 101 of the document illumination system is turned on, and the luminous flux emitted from the light source 101 is condensed by the reflecting shade 102 and irradiates the document surface 104. At this time, the light amount of the light source 101 of the document illumination system is changed so that a copy having an appropriate density can be made depending on the size of the detected density of the document. The reflected light from the document passes through the imaging lens 106 and the mirror 107 and irradiates the photosensitive drum 109. Then, copying is performed at an appropriate density by an electrophotographic process (not shown).

The document density detection in this case will be described in detail.

When the original 104 passes near the density detecting device 108, the light flux emitted from the AE light source is emitted from the original 104.
Illuminates a part of the normal direction. The reflected light from the original 104 is applied to the light receiver 52 obliquely arranged at a position facing the original 104. The light receiver 52 is the original 104
It receives the reflected light flux from the illuminated part of the.
Therefore, the amount of light applied to the light receiver 52 is a reflected light flux from a wide range of the illumination unit of the document 104, and the amount of reflected light is a value related to the average reflection density for this illumination region.

A second conventional example is shown in FIG.

Also in the second conventional example, the AE illumination system is the same as in the first conventional example.

In the light receiving system, a light condensing lens 54 arranged between the document surface 51 and the light receiver 52 focuses a part of the document surface 51 illuminated on the light receiving portion of the light receiver 52. Therefore, it is possible to detect the density of a minute area of the document surface 51.

[0015]

However, in such a conventional technique, the density of the document surface is broadly read as in the first conventional example shown in FIG. When the background density of the paper is high, it cannot be distinguished, and when copying is performed, the density of the background reproduction of the copy may change depending on the character density of the document, which may cause deterioration of image quality.

Further, the temperature rise due to the light source may cause the exterior member to be deformed or the light receiver to be adversely affected by heat.

In the second conventional example shown in FIG. 10, the amount of light incident on the light receiver is significantly reduced, the S / N is lowered, and the detection accuracy is lowered. In order to prevent this, there is a means for increasing the light amount of the light source, but the temperature rise of the device due to heat generation of the light source,
There is a drawback that a space for cooling is required and the device becomes large. As another means, there is a means for increasing the amplification factor of the amplifier in order to increase the detection sensitivity, but in this case, there is a drawback that the device (circuit) becomes expensive.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to detect a document density which enables highly accurate document density detection regardless of the character density of the document. To provide a device.

[0019]

In order to achieve the above-mentioned object, the document density detecting apparatus of the present invention illuminates the surface of a document with a minute area so that the surface of the document is wider than the minute area. It is characterized by having a condensing optical system capable of condensing reflected light.

The light source for illuminating the original is a tungsten light bulb, a pinhole (hole) and a lens are arranged between the original surface and the light bulb, and a color filter is arranged between the original surface and the light receiver. And

The light source for illuminating the original is an LED, a lens is arranged between the original surface and the LED, and a color filter is not interposed between the original surface and the light receiver.

The spot diameter for illuminating the original is about 2 mm or less.

The spot diameter for illuminating the original is about 0.3 mm
It is characterized by the following.

[0024]

Thus, the document density detecting device of the present invention illuminates a minute area with a spot diameter of 2 mm or less or 0.3 mm or less for illuminating a document in a spot-like manner, and the reflected light is a very small area. Since the light receiver is arranged so as to be able to receive light in an area wider than the area, it is possible to detect the document density with high accuracy regardless of the complicated character density. Moreover, since only a minute area is illuminated, a light source with a small amount of light and low power consumption can be used.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

In FIG. 1 showing a document density detecting apparatus according to the first embodiment of the present invention, 1 is a document surface, 2 is a light receiver, 3 is a color filter, 4 and 5 are lenses, and 6 is a pinhole. , 7 are tungsten bulbs.

The light flux emitted from the tungsten bulb 7 illuminates the document surface 1 in a minute area A by the action of the pinhole 6 and the lens 5. Further, the lens 4 receives the reflected light from the area B on the document surface 1 having a larger area than the minute area A, and receives the light by the light receiver 2 which is arranged substantially in the normal direction of the document surface 1.

Therefore, even if the position of the minute area A is deviated, the lens 4 capable of condensing light is arranged in the area B (the thick line portion in FIG. 1) which is a wider range than the minute area A. Since the reflected light from is taken in by the lens 4 and received by the light receiver 2, it is possible to constantly detect the original density.

Further, a color filter 3 is arranged on the front surface of the light receiver 2, and the color filter 3 is the original density detecting device 108.
The spectral characteristic of is set to a spectral characteristic that approximately matches the spectral sensitivity of the copying machine.

The reason for arranging the light receiver 2 in the normal direction of the original is to detect the original density because the light distribution reflection efficiency of the paper is higher in the normal direction and the light amount is larger than in the case of arranging it in a direction other than the normal direction. This is because a high S / N can be achieved.

The second embodiment is shown in FIG.

FIG. 2 shows an embodiment in which an LED light source 8 is used as a light source and a lens 5 is arranged between the light source 8 and the document surface 1.

By using the LED light source 8 as the light source, the light source and the device can be downsized, the power consumption can be reduced, and the light source can be obtained at low cost.

A third embodiment is shown in FIG.

FIG. 3 shows an embodiment in which an LED light source 9 with a lens is used as a light source. There is a ready-made LED light source 9 with a lens, which is available at low cost and easy to package.

A fourth embodiment is shown in FIG.

In FIG. 4, the light receiver is a light receiver 10 with a lens,
For example, it is an embodiment using a photodiode with a lens or the like.

The fifth embodiment (not shown) is an embodiment in which the spot diameter for irradiating a document is about 2 mm or less.

Since the distance between the characters on the original is usually about 2 mm, accurate accuracy of detecting the density of the paper surface can be obtained.

The sixth embodiment (not shown) is an embodiment in which the spot diameter for irradiating a document is set to about 0.3 mm or less.

The minimum line width of characters in a general manuscript is 0.3.
Since it is about mm, by setting the spot diameter to 0.3 mm or less, it is possible to detect the character density with higher accuracy.

The seventh embodiment is shown in FIG.

FIG. 5 shows an embodiment in which the light emitting color of the LED light source 9 with a lens is green.

By setting the emission color to green, the color filter 3
Need not be installed, resulting in downsizing and cost reduction.

The eighth embodiment is shown in FIG.

FIG. 6 shows an embodiment in which the light receiver and the illumination system are fixed to the package 11.

By making the package, the assembling work is easy, the manufacturing process is reduced, and the cost can be reduced.

FIG. 7 shows the ninth embodiment.

FIG. 7 shows the document density detecting device 108 and the document surface 1.
In this embodiment, a transparent dustproof glass 12 is disposed between the sheets to prevent the paper dust in the document passage area from adhering to the apparatus.

[0050]

The present invention has the above-mentioned constitutions and operations, and the effects will be described in each claim below.

(Effect according to Claim 1) By illuminating the surface of the original with a minute area and having a condensing optical system capable of condensing the reflected light from the surface of the original having a larger area than the minute area,
It is possible to detect the document density with high accuracy regardless of the complicated character density.

Further, the problem of insufficient received light amount does not occur.

Further, even when the minute area to be irradiated is displaced, the reflected light is received by the light receiver, so that the stable document density detection can be always performed.

Since only a small area needs to be illuminated, a small light source with low power consumption can be used.

(Effect according to claim 2) Since the color filter is arranged between the document surface and the light receiver, it is possible to correspond to the light source color of the copying machine which is the conventional example of FIG. 8 and to correspond to various document colors. It is possible to detect the concentration with high accuracy. Further, there is no need to add a filter as a separate member, and the effects of cost reduction and downsizing can be obtained.

(Effect according to claim 3) Since the light source for illuminating the original is an LED light source, it is advantageous in space compared to a large light bulb, and is also advantageous in power consumption, and deformation of the exterior member due to temperature rise. No longer occurs and the receiver is not adversely affected by heat from the light source. Therefore, the emitted light flux can be efficiently emitted.

In general, many of the ready-made LEDs are equipped with a lens, and have the advantage of being “easy to obtain” and “cheap”.

Further, by coloring the lens, the emission color can be colored, the color filter need not be arranged, and the cost and size can be reduced. By packaging the LED light source, the light receiver, and the lens, it is possible to reduce the size, improve the assembly workability of the copying machine, and reduce the cost of the copying machine.

(Effect according to claim 4) Since the spot diameter for illuminating the original is about 2 mm or less, a high character density detection accuracy can be obtained, and an accurate paper surface density detection accuracy can be obtained. Further, the density detection accuracy is stable even when the document is misaligned in the direction normal to the document surface. In this case, a fog-free copy can be obtained by accurately detecting the paper surface.

(Effect of Claim 5) Since the spot diameter for illuminating the original is about 0.3 mm or less, a higher character density detection accuracy can be obtained.

As shown in the ninth embodiment of FIG. 7, since the transparent dustproof filter is arranged between the document density detecting device and the document surface, the adhesion of dust to the document density detecting device is reduced,
Effects such as obtaining stable performance over a long period of time can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing a document density detecting device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a document density detecting device according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram showing a document density detecting device according to a third embodiment of the present invention.

FIG. 4 is a schematic diagram showing a document density detecting device according to a fourth embodiment of the present invention.

FIG. 5 is a schematic view showing a document density detecting device according to a seventh embodiment of the present invention.

FIG. 6 is a schematic view showing a document density detecting device according to an eighth embodiment of the present invention.

FIG. 7 is a schematic view showing a document density detecting device according to a ninth embodiment of the present invention.

FIG. 8 is a schematic view showing a copying machine according to the present invention.

FIG. 9 is a schematic view showing a document density detecting device according to a first conventional example of the present invention.

FIG. 10 is a schematic view showing a document density detecting device according to a second conventional example of the present invention.

[Explanation of symbols]

 1 Original Surface 2 Light Receiver 3 Color Filter 4 Lens 5 Lens 6 Pinhole (Hole) 7 Tungsten Light Bulb 8 LED Light Source 9 LED Light Source with Lens 10 Light Receiver with Lens 11 Package 12 Dust-proof Glass 51 Original Surface 52 Light Receiver 53 Color Filter 54 Condensing lens 55 Tungsten light bulb 56 Box (case) 101 Green fluorescent light source 102 Reflector shade 103 Document placing glass 104 Document 105 Reflected light 106 Imaging lens 107 Mirror 108 Document density detector 109 Photosensitive drum 110 Document feeder

Claims (5)

[Claims] 1. A document density detecting device for illuminating a document surface with a light source, and collecting reflected light from the document surface on a light receiving element to detect the reflection density of the document surface. A document density detecting apparatus having a condensing optical system capable of condensing reflected light from a document surface having an area larger than the minute area described above by illuminating the area. 2. A light source for illuminating the document surface is a tungsten bulb, a pinhole (hole) and a lens are arranged between the document surface and the light bulb, and a color filter is arranged between the document surface and a light receiver. The document density detecting device according to claim 1, wherein 3. A light source for illuminating the document surface is an LED,
2. The document density detecting device according to claim 1, wherein a lens is arranged between the document surface and the LED, and a color filter is not interposed between the document surface and the light receiver. 4. The spot diameter for illuminating the document surface is about 2 mm.
4. The document density detecting device according to claim 1, wherein: 5. The spot diameter for illuminating the original surface is about 0.
It is 3 mm or less, Claim 1, 2 or 3 characterized by the above-mentioned.
The document density detecting device described.