JPS6151820B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a shading correction device.

Conventional shading correction devices include those with a mechanical configuration that corrects shading by using a plurality of shielding block pieces for illumination light, and those with a mechanical configuration that divides a scanning section into a plurality of small sections and corresponds to the amount of shading in each section. There are electrical configurations controlled by weighting circuits.

Such a conventional device uses a so-called static correction method in which a partial correction amount for each section is set in advance and correction is made based on this, so it is difficult to use when the shedding correction amount changes over time or when condensed illumination is performed using a line light source. There has been a problem in that it is not possible to make corrections in response to relatively short-time shading fluctuations that occur for each copy or during copying.

The present invention has been made to solve these conventional problems, and is capable of automatically making appropriate corrections even when shedding fluctuations occur over time or instantaneously. In other words, it is a shedding correction method that can perform dynamic corrections. The purpose is to provide equipment.

In order to achieve this object, the present invention provides a white diffuse reflection part in a parallel line close to the main scanning line of the solid-state scanner illumination system, and combines optical information of the imaged main scanning line and the document. Optical information from the white diffuse reflection sections having substantially the same light intensity distribution is detected by a photoelectric conversion section, and the ratio or difference between the two is calculated to obtain an effective read signal.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 and 2 are a front view and a plan view showing an optical section of an embodiment of a shading correction device according to the present invention. In these figures, manuscript 0
A slit 2 is disposed in front of the contact glass 1 on which the contact glass 1 is placed, and a white diffuse reflection section 10 is disposed in the slit 2 in a parallel line close to the main scanning line section as shown in FIG. It is being Manuscript 0
The optical information from
It is now readable by

Optical information from the white diffuse reflection section 10 is imaged by the imaging lens 3, and detected by the photoelectric conversion element groups ₆₁ to 6n via the half mirror 4. The half mirror 4 is provided because
Since the imaging positions of the optical information from the original 0 and the optical information from the white diffuse reflection unit 10 are extremely close to each other, that is, as shown in FIG.
The imaging light beam 5S for reading and the photoelectric conversion element group 6 ₁ ~
This is to separate the optical paths since the imaging light beam 6S for detecting the amount of light 6n will be in a state of being extremely close to each other. The photoelectric conversion element groups 6 ₁ to 6n are arranged so as to correspond to a specific main scanning portion of the solid state scanning element 5, as shown in FIG.

According to the embodiment with such a configuration, the white diffuse reflection section 10 and the main scanning line section are provided close to each other, so that the illuminance distribution on the document surface due to the illumination system is almost the same in the main scanning direction, and the imaging For lens 3 as well, the peripheral light amount reduction characteristics of both lenses are almost the same. Therefore, the shading of the surface of the solid state scanning element 5 and the shading of the photoelectric conversion elements 6 ₁ to 6n are almost the same.

Furthermore, in the above embodiment, when reading is performed in this state, the output V ₁ of the solid-state scanning element 5 is obtained as a composite output of the image information of the original 0 and the above-mentioned shading, as shown in FIG. Since the element groups 6 ₁ to 6 n will detect white uniform reflected light, they should output a series of average outputs (sample-held state) V ₂ of each part of the above-mentioned shading, as shown in FIG. 6b. becomes.

The reflected imaging light from the background of the document received by the solid-state scanning element 5 and the reflected imaging light from the white diffuse reflection section 10 received by the photoelectric conversion elements 6 ₁ to 6n are both white light, and the solid-state scanning element 5 and the photoelectric conversion elements 6 ₁
The light intensity distribution in the main scanning direction on the light receiving surface of ~6n has a similar proportional relationship with respect to the white level, so
As shown in FIG. 5, the output of the solid-state scanning element 5 for a particular bit in the main scanning line is
V ₁ i, photoelectric conversion elements 6 ₁ to 6n corresponding to this V ₁ i
If the j-th output of is V ₂ j and the series of maximum values of output V ₁ i is V _1inax , then V=V _1inax /V _2j is constant.

In order to set this V to an appropriate value as an output processing signal, it is sufficient to use the value V ₃ =αV ₂ instead of directly calculating V ₂ . In such processing,
The black level of V ₁ is near the ground level regardless of the main scanning position, but at this time, V = V ₁ / αV ₂ is V ₂
(or V ₃ ) has a value near the ground level regardless of the magnitude of the output due to a change in the main scanning position, and V has a waveform as shown in FIG. 6c as a whole. As a result, the level of V _2nax is converted into an output with uniformity, that is, shading is removed, the white level is corrected, and the black level is maintained near the ground level.

Since the value of V _1nax /V ₂ remains constant even if there is a local variation in light intensity, it is no longer possible to use a mechanical shading correction method that was conventionally performed for each shielding piece or block, or an electrical method that uses a weighting circuit to control the gain. In contrast, even if the shading characteristic fluctuates over time or instantaneously, it is possible to stably and appropriately correct the shading characteristics regardless of the state of the fluctuation.

FIG. 7 shows an example of the configuration of a drive control section for the solid-state scanning element 5 and the photoelectric conversion element groups 6 ₁ to 6n, and an arithmetic processing section for the above-mentioned V _1i and V _2j . In this figure, a drive counting circuit 71 drives and controls the solid-state scanning element 5 so that it reads optical information from a document 0 in a predetermined sequence, and sends a counting signal to a switching circuit 72. The switching circuit 72 receives the count signal and energizes one of the photoelectric conversion elements 6 ₁ to 6 n corresponding to the scanning location of the solid-state scanning element 5, and this photoelectric conversion element receives optical information from the white diffuse reflection section 10. and convert it into an electrical signal. The signal output processing circuit 73 determines a series of maximum values V _1inax of the output signal V _1i of the solid-state scanning element 5 and sends it to the composite signal processing circuit 76 .

The amplifier circuit 74 receives the output signal V of the photoelectric conversion elements 6 ₁ to 6n designated by the switching circuit 72.
The output signal processing circuit 75 multiplies _{the amplified V 2j by} α and sends it to the composite signal processing circuit 76. Combined signal processing circuit 7
6 performs the calculation V=V _1inax /V _2j and outputs the output processed signal V.

FIG. 8 shows a configuration example in which the above-described embodiment is applied to an actual solid-state scanner. In this figure, original 0
is irradiated by an illumination unit 81 through the contact glass 1 and transported by a document feed unit 82. The slit 2 is arranged close to the contact glass 1, and the above-mentioned white diffuse reflection section 10 is formed therein. A plurality of light shielding slits 83 are provided on the optical path of the optical information 5S from the original document 0 and the optical information 6S from the white diffuse reflection section 10.

The mirror 84 captures the original 0 and the white diffuse reflection section 10
It reflects the light from the mirror and sends it to the imaging unit 85. The imaging unit 85 is a scanner base 86.
The light from the document 0 and the light from the white diffuse reflection unit 10 are transmitted through the half mirror 4 to the solid-state scanning element 5 and the photoelectric conversion elements 6 _{1 to 6} , respectively.
The image is formed on the light receiving surface of 6n. The solid-state scanning element 5 is fixed to a sensor board 87, and the photoelectric conversion elements 6 ₁ to 6n are attached to a substrate 8 on which the amplifier circuit 74 and output signal processing circuit 75 shown in FIG. 7 are mounted.
It is fixed to 9. The positions of the photoelectric conversion elements 6 ₁ to 6 n can be adjusted by a position adjustment unit 88 .

The solid-state scanner with such a configuration operates in the same manner as the embodiments shown in FIGS. 1 and 7 above, and even if the shedding characteristics fluctuate over time or instantaneously, it can stably and appropriately correct the shading characteristics regardless of the state of the fluctuations. can be done.

In the above embodiment, the white diffuse reflection part 10 is provided in the slit 2, but as shown in FIG. A diffuse reflection section 10' may also be formed.

Furthermore, in the above embodiment, V ₁ and αV ₂ (=
Although the shedding correction was performed by taking the ratio with V ₃ ), by using the characteristics of V _2nax , _α′V
It may also be used as a reference level for value conversion (V _Ref in FIG. 6a). (Here, α' is a coefficient that gives V ₃ ' suitable for V _Ref .) In this case, the composite signal processing circuit 76 of FIG. 7 outputs V ₁ at the non-inverting input terminal as shown in FIG. is received at the inverting input terminal.
Preferably, the comparator 100 receives V ₃ ' and outputs a comparison reference value V for each block.

Further, the photoelectric conversion elements 6 ₁ to 6n, that is, the reference photodetection elements, may be constructed from a low-density solid-state scanning element in addition to a photodiode or the like.

As is clear from the above description, the present invention provides a white diffuse reflection section in a parallel line close to the main scanning line of a solid-state scanner illumination system, and outputs a photoelectric conversion output and a scanning output from this white diffuse reflection section. Since the effective read signal is obtained by determining the relationship between the two, even if shedding fluctuations occur over time or instantaneously, they can be automatically corrected.

[Brief explanation of the drawing]

1 and 2 are a front view and a plan view showing an embodiment of the optical system of the shedding correction device according to the present invention, FIG. 3 is an enlarged view showing the slit 2 in FIGS. 1 and 2, and FIG. is an explanatory diagram showing the arrangement relationship between the contact glass 1 and the slit in FIGS. 1 and 2 and the optical path of optical information, and _FIG .
6n is an explanatory diagram showing the correspondence between the solid-state scanning signal 5 and the photoelectric conversion elements 6 ₁ to 6n, and a waveform diagram showing the output signals of the photoelectric conversion elements 6 1 to 6n and the signals obtained by processing these signals. A block diagram showing one embodiment of the drive control section and the arithmetic processing section of the shedding correction device according to the invention, and FIG. 8 is a schematic configuration diagram showing the state in which the embodiments of FIGS. 1 and 7 are incorporated into an actual solid-state scanner. , FIG. 9 is an explanatory diagram showing another example of the structure of the white diffuse reflection section, and FIG. 10 is a block diagram showing another example of the structure of the composite signal processing circuit 76 of FIG. DESCRIPTION OF SYMBOLS 1...Contact glass, 2...Slit, 3...Imaging lens, 4...Half mirror, 5...Solid scanning element, _61-6n ...Photoelectric conversion element, 10, 10'...
White diffuse reflection section, 71... Drive counting circuit, 72... Switching circuit, 73... Signal output processing circuit, 74
...Amplification circuit, 75...Output signal processing circuit, 76...Composition signal processing circuit.

Claims (1)

[Scope of Claims] 1. An illumination unit that illuminates a document over the entire length of its main scanning line through a slit and a contact glass; an optical system that transmits optical information from reference white diffuse reflection sections that are arranged in parallel lines in close proximity and that have substantially the same light intensity distribution as the original; and a first photoelectric conversion section that detects optical information of the original. and a second photoelectric conversion section that detects optical information of the reference white diffuse reflection section; inputting the output signals of the first and second photoelectric conversion sections, and converting the output signals of the first and second photoelectric conversion sections using the difference or a predetermined ratio as a reference. A shading correction device comprising an arithmetic processing circuit for correcting an output signal of a photoelectric conversion unit. 2. The shedding correction device according to claim 1, wherein the reference white diffuse reflection section is formed on a slit. 3. The shading correction device according to claim 1, wherein the reference white diffuse reflection section is formed on a contact glass.