JPH02284572A - Shading distortion correcting structure for lens reduction reading system scanner - Google Patents

Abstract

PURPOSE:To eliminate a douser and to eliminate needs for executing a troublesome adjustment such as the douser by installing an adjustment means for a point light source and permitting the adjustment means to adjust the light quantity of the point light source in such a way that the light quantity whose shading distortion is corrected is given to a reading means. CONSTITUTION:The light source 2 is arranged in parallel to the original surface 1a of an original 1, and the above scanner consists of an LED array 13 which is linearly arranged in a direction orthogonal to the moving direction of the original 1, and a diffusing/condensing lens 14 installed on the original 1-side of the LED array 13. In respective LED 12 arranged on the LED array 13, three are connected in serial and resistances Rn, Rn+1, Rn+2,..., are respectively connected to LED in serial. The luminous quantity of LED 12 is adjusted by setting the values of the resistances. Thus, the luminous quantity of LED 12 in the central part of the LED array 13 is reduced so that the shading distortion of a CCD image sensor 6 is corrected.

Description

Detailed Description of the Invention (a) Industrial Application Field This invention irradiates a document with light, reduces the reflected light from the document with an optical lens, and reads the reduced light with a sensor to generate electricity. The present invention relates to a lens reduction reading type scanner, such as a scanner used for facsimile, which converts signals into signals.

(B) Prior Art A conventional lens reduction reading scanner, as shown in the overall configuration of FIG. , the original 21 is irradiated with light H from a light source 22 using a light emitting element such as an LED.

Then, the light H reflected from the original 21 is transferred to the first mirror 23.
, the optical path is changed by a second mirror 24, etc., the light is reduced by a lens 25, and the reduced light is read by a reading sensor 26 such as a COD image sensor.

The light source 22 is a band-shaped linear light source that extends in a direction perpendicular to the moving direction of the document indicated by arrow G. Therefore, the first mirror 23 and the second mirror 24 are mirrors that extend in a direction parallel to the light source 22. .

The lens 25, which is the image reduction means of the optical system, is an axially symmetrical lens like that used in a normal camera lens, and reduces the entire incident image in the vertical and horizontal directions.

The reading sensor 26 has a structure in which light receiving elements are arranged in a direction parallel to the light source 22 in order to read the irradiated portion of the document illuminated by the light source 22.

For example, in the case of a CCD image sensor, 2
Approximately 000 light-receiving elements are arrayed, and each light-receiving element photoelectrically converts the amount of light it receives for 5 milliseconds, and serially outputs the signal from one side of the array to the other. ing.

Incidentally, such a lens reduction reading type scanner uses a lens 25 which is an image reduction means of the optical system. Therefore, the lens 25 after passing through the lens 25
The amount of light at the periphery, that is, the amount of light at the periphery of the reading sensor 26 decreases, resulting in a difference in the level of the output signal between the light receiving element located at the center of the reading sensor 26 and the light receiving element located at the periphery. So-called shading distortion occurs.

In order to correct this shading distortion, in a conventional lens reduction reading type scanner, a light shielding plate 27 for adjusting the amount of light is attached in front of the lens 25, as shown in FIG.

The light shielding plate 27 is provided symmetrically with respect to the optical axis of the light H, and is a semicylindrical opaque plate when viewed along the optical axis direction. Using this light shielding plate 27, the lens 25
By reducing the amount of light in the center, the reading sensor 2
The amount of light incident on the lens 6 is made uniform between the central portion and the peripheral portion.

FIG. 5 is a graph showing the relationship between time T and sensor output signal level S when the reading sensor 26 is, for example, a CCD image sensor.

In the case of a CCD image sensor, as mentioned above, the amount of accumulated light received by each light receiving element for 5 milliseconds is photoelectrically converted and output, so the output from the CCD image sensor is at 5 millisecond intervals. Since the output is performed serially from one side to the other side of each light receiving element arranged in a linear manner, the time axis T corresponds to the position on the arrangement of the light receiving elements.

The solid line in FIG. 5 is the output signal level S of the CCD image sensor before the shading distortion is corrected by the light shielding plate 27.
As shown in the figure, the output decreases around the sensor. Furthermore, the dotted line in the figure is the output signal level S of the CCD image sensor after reducing the output at the center of the sensor using the light shielding plate 27, that is, after correcting shading distortion.

When adjusting the position of the light shielding plate 27, for example, if the reading sensor 26 is the above-mentioned CCD image sensor, make adjustments by looking at the waveform of the output signal of the sensor as shown in FIG. I try to do it.

(C) Problems to be Solved by the Invention However, the position adjustment of the light shielding plate 27 as described above is
The adjustment is extremely delicate and complicated, and it also has the problem of being easily disturbed by vibrations of the equipment.

This invention was made in consideration of these circumstances,
To provide a shading distortion correction structure for a lens reduction reading type scanner, in which shading distortion is corrected without using a conventional light shielding plate 27 by reducing the amount of light emitted at the center of a band-shaped light source 22. It is.

(d) Means for Solving the Problems This invention includes a light source that illuminates a document in a strip shape, a lens that reduces light reflected from the document, and a plurality of light receiving units arranged linearly to receive the light that has been reduced by the lens. The light source comprises a point light source array in which a plurality of point light sources are arranged linearly in the band-like direction, and the light source includes a reading means for converting the amount of light received by the element into an electric signal for each light receiving element and sequentially outputs the same. , adjustment means for adjusting the light emission amount of the point light source located at the center of the point light source array to reduce the light emission amount of the point light source located at the center of the point light source array so that the reading means is given a light amount for correcting shading distortion to the point light source of the point light source array. This is a shading distortion correction structure for a lens reduction reading type scanner, which is characterized by being provided.

In addition, the shading distortion referred to in this invention refers to a difference in the level of the output signal between the light receiving element located at the center of the reading means and the light receiving element located at the peripheral part, and it is difficult to correct the shading distortion. , means to minimize the difference as much as possible.

Further, the point light source array according to the present invention may be one in which a plurality of point light sources are arranged in a straight line so that the document can be irradiated in a band shape in a direction perpendicular to the document feeding direction, and each point light source For example, a light emitting element such as an LED is used.

Further, as the lens, an axially symmetrical lens such as a single lens or a compound lens, which is used in conventional facsimiles, is used.

The reading means may be any device that can arrange a plurality of light receiving elements in a linear manner, receive light with the light receiving elements, photoelectrically convert the amount of light received by each light receiving element in a predetermined time, and sequentially output the light. For example, it is preferable to use a sensor such as a COD image sensor used in conventional facsimiles.

Further, the adjusting means may be any means as long as it can be adjusted so as to reduce the amount of light emitted from the point light source, and for example, a resistor or the like may be used.

(Po) The light emitted from the action point light source array and reflected from the original is
The amount of light that is reduced by the lens is
The reading means converts each light-receiving element into an electrical signal and sequentially outputs it.

At this time, the point light source located at the center of the point light source array is
The amount of light emitted is adjusted by the adjusting means to decrease, so that the amount of light incident on the light receiving element located at the center of the reading means and the light receiving elements located at both ends of the reading means is made uniform.

Therefore, shading distortion can be corrected without using a conventional light shielding plate.

(f) Examples Hereinafter, the present invention will be described in detail based on examples shown in the drawings. Note that this invention is not limited to this.

FIG. 2 is an explanatory view of the overall configuration of an embodiment of the present invention.

In the figure, l is A4, B moving in the direction indicated by the arrow.
2 is a light source that illuminates the original; 3 and 4 are first mirrors for changing the optical path of light reflected from the original; and second mirror 5 is a lens for reducing light; 6
is a COD image sensor that reads the light reduced by the lens 5.

The light source 2, which will be described in detail later, is a strip-shaped linear light source in which LEDs are arranged in a direction perpendicular to the direction of the arrow. Further, the first mirror 3 and the second mirror 4 are mirrors placed parallel to the arrangement of the LEDs of the light source 2.

The lens 5 is an axially symmetrical lens like that used in a normal camera lens, and reduces the incident image in all the vertical and horizontal directions.

The COD image sensor 6 has a structure in which light receiving elements are linearly arranged in a direction parallel to the light source 2 in order to read the irradiated portion of the document irradiated by the light source 2. For example, B
In the case of a COD image sensor 6 that reads a document of size 4 by moving it in the vertical direction (longitudinal direction),
Light-receiving elements are arranged in a direction perpendicular to the document feeding direction.

For example, if 1 mm is divided into 8 pixels and read, the width of a B4 original is 25
If it is 6mm, then 256mm x 8 pixels = 2048 pixels, 20
48 pixels are required, and each pixel corresponds to one light-receiving element, so if the size of each light-receiving element is approximately 14 μm, then 14 μm x 2048 (light-receiving elements) - approximately 24 mm, resulting in a length of approximately 24 mm. This results in a linear array of shapes.

The overall size of the COD image sensor 6 is approximately 40 to 42 mm, which is the arrangement described above plus a peripheral device.

This COD image sensor 6 photoelectrically converts the amount of light received by each light receiving element for 5 milliseconds, transfers it to a shift register, and serially outputs the signal from one side of the array to the other side. The output is performed every time a transfer lock signal is applied from the outside.

FIG. 1(A) is a detailed explanatory diagram of the light source 2, and FIG. 1(B) is a detailed explanatory diagram of the light source 2.
A graph showing the relationship between the document reading position corresponding to the arrangement of the light receiving element of the CD image sensor 6 and the output signal level S of the light receiving element, and FIG. 3 is a circuit for adjusting the amount of light emitted by the LED of the light source 2. FIG. Figure 1 (B)
In order to simplify the explanation, the output signal level S of the light receiving element and the light amount of the light source 2, which are in a proportional relationship, are simultaneously displayed on the vertical axis, and the horizontal axis is shown as shown in FIG. 1(A). The reading position corresponding to the original reading range is shown.

As shown in FIG. 1(A), the light source 2 is installed parallel to the original surface 1a of the original l, and a large number of LE lights are placed on the substrate il.
An LED array 13 arranged linearly in a direction perpendicular to the moving direction K of the document l (see FIG. 2);
It consists of a diffusing/condensing lens 14 provided on the document l side of the array I3.

In the case of standard LEDs, the arrangement pitch of the LEDs 12 in the LED array 13 is 2 to 2.5 m in diameter.
m, so the intervals are approximately 3 mm. Therefore, when irradiating a B4 original, the width of the B4 should be set to 256mm.
Then, it becomes 256 ÷ 3 - about 85 pieces, and since it is irradiated a little wider than the width of the paper,
The LED array 13 includes approximately 90 to 90 LEDs linearly arranged.
The configuration includes approximately 100 pieces.

Moreover, each LED 12 arranged in the LED array 13 is
As shown in Fig. 3, three LEs are connected in series, and each of these three LE:DI2 has resistors Rn, Rn,
,,R,,t,-,are connected in series. Therefore, by setting the values of these resistors R, , R11, . . . , Rn, 2°, etc., it is possible to adjust the amount of light emitted from the LED 12.

As a result, the amount of light emitted from the LED 12 in the center of the LED array 13 is reduced so that the shading distortion of the CCD image sensor 6 is corrected.

That is, the resistors Rn, Rn, l are set so that the light quantity characteristics of the light source 2 are opposite to the shading distortion.

Rn+2.　　　・、Set the value of.

Note that in the above example, LED l 2 is connected to 3 arrays and resistor R is connected, but it is also possible to connect one resistor R to one LED 12, or , four or more LEDs may be connected in series L, and a resistor R may be connected thereto. However, if one resistor R is provided for each LED l2, a large number of resistors R will be required, and a problem will arise in the space for their arrangement. Also, LED 12 is 1
In order to light up with about 1.4μ DC per unit, if 3 units are connected in series, the voltage drop will be approximately 4.2μ, which is 5μ
A supply voltage Vcc higher than that is required. On the other hand, the supply voltage V
Since cc is usually a DC voltage of about 5 - 12V, it generally has 3 to 6 to 8 LEDs at most.
are connected in series, and one resistor R is provided for it.

With such a configuration, as shown in FIG. 1(B),
Even if the shading distortion characteristic of the output signal level S in the CCD image sensor 6 is a "mountain-shaped" curve, the light amount characteristic from the light source 2 is a "shading distortion characteristic" that is the opposite of the shading distortion characteristic.
Because the curve is “valley-shaped”, both characteristics cancel each other out, and CC
The output waveform from the D image sensor 6 has a flat output signal level S as shown by the dotted line in the figure.

In this way, the value of the resistor R is set to reduce the amount of light emitted from LED l2 located in the center of the LED array 13, and the characteristics of the amount of light emitted from the LED array 13 are changed to
By correcting the shading distortion by making the characteristics opposite to the shading distortion, a light shielding plate becomes unnecessary.

(g) Effects of the Invention According to the present invention, the point light source is provided with an adjustment means, and the light emission amount of the point light source is adjusted by the adjustment means so that the light amount that corrects shading distortion is given to the reading means. This eliminates the need for a light-shielding plate and eliminates the need for complicated adjustments such as those for light-shielding plates.

Furthermore, since there is no adjustment part such as a light shielding plate, it is possible to provide the reading means with an extremely stable amount of light even in the face of vibrations.

[Brief explanation of drawings]

FIG. 1(A) is a detailed explanatory diagram of the light source of the present invention, FIG.
B) is a graph showing the relationship between the document reading position and the output signal level of the light receiving element, FIG. 2 is an explanatory diagram of the overall configuration of an embodiment of the present invention, and FIG. An electric circuit diagram showing the circuit, FIG. 4 is an explanatory diagram of the overall configuration of a conventional lens reduction reading type scanner, and FIG. 5 is a graph showing the relationship between time and output signal level in a conventional reading sensor. 1...Original, la...Document surface, 2...Light source, 3...First mirror 4...
...Second mirror 5...Lens, 6...
- COD image sensor - 11... board, 12... LED. 13...LED array, 14...Diffusing/condensing lens, K...Document movement direction, L...Light, R...
··resistance. -15=

Claims (1)

[Claims] 1. A light source that illuminates the original in a strip shape, a lens that reduces the light reflected from the original, and a plurality of light receiving elements arranged in a straight line to receive the light reduced by the lens and convert the amount of light into electricity for each light receiving element. The light source comprises a point light source array in which a plurality of point light sources are linearly arranged in the band-like direction, and the point light sources of the point light source array are subjected to shading distortion. Lens reduction reading characterized in that adjustment means is provided for adjusting to reduce the amount of light emitted from a point light source located at the center of the point light source array so that the amount of light that is corrected is given to the reading means. Shading distortion correction structure of the method scanner.