JP2547037B2 - Color reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A color reading device, in particular, a color reading device of a system that reads a color image in a time-division manner by switching filters, and an object thereof is to shorten a filter switching stroke, that is, to achieve a high speed. Synchronizing the driving of the line image sensor and the switching of three color filters vertically arranged in stripes on the same substrate that is vertically sinusoidally driven across the reading light of the line image sensor. In a filter switching type color reading device that reads color images in a time-sharing manner,
Of the three color filters arranged in parallel vertically, the moving distance of the substrate when switching the upper and central filters is equal to the moving distance of the substrate when switching the lower and central filters. Each filter is arranged at the same time, and the reading time for each color is made different in order to compensate for the difference in sensitivity for each color.

[Industrial applications]

The present invention relates to a color reading device, and more particularly to a color reading device of a type in which a color image is read in a time division manner by switching filters.

Color reading devices are widely used as image input devices for facsimiles and computers. Known as these color reading devices are those that read three colors of R (red), G (green), and B (blue) using a CCD image sensor or the like. There is a demand for further miniaturization, higher speed, lower price, etc. of this color reading device.

[Conventional technology]

FIG. 3 is a perspective view showing a main part of a conventional filter switching type color reading apparatus. In the figure, reference numeral 1 indicates a reading line on the original 100. The reading line 1 is illuminated by an illuminating means (not shown), and the image on this line is read as follows.

Reflected light (reading light) from the reading line 1 is imaged by a lens 2 on a line image sensor 3 such as a CCD line image sensor. In order to perform color reading, R, G and B three filters 4a, 4b and 4c are provided between the lens 2 and the sensor 3. The filters 4a, 4b, 4c are connected to the linear motors 5a, 5b, 5c, respectively, and can be moved to positions where the reading light from the reading line 1 to the sensor 3 is blocked. When reading the R component of the color image on the reading line 1, as shown in FIG. 4 (a), the R filter 4a of the three filters is placed in the optical path by driving the linear motor 5a. . The other two filters 4b and 4c are held at the retracted position where they do not block the optical path. As a result, the reading line 1
Only the red light of the reflected light from the light reaches the sensor 3, and the R component of the image is read. When reading the G and B components of the image, as shown in FIGS. 4 (b) and 4 (c), the filters 4b and 4c are inserted in the optical paths, respectively. 1 line R, G, B
When the reading is completed, the document 100 is fed by a predetermined amount in the arrow direction (sub-scanning direction) in FIG. 3 to read the next line.

In this color reading device, by combining a small and lightweight filter and a high-speed linear motor, high-speed color reading can be performed by switching the filter in a time almost equal to the one-line reading time (1 to 10 ms) of the sensor. Can be realized. Note that the filter insertion position is 100
The same effect can be obtained between the lens 2 and the lens 2.

The conventional color reading device having such a structure and operation has the following advantages.

(1) Compared to the conventional three-optical system type, one optical system is provided, and the device can be downsized.

(2) Black-and-white reading can be performed by removing all three filters from the reading optical path, and one device can be used for both color and black-and-white reading devices. Further, the filter switching mechanism can be unitized to be an option of the conventional monochrome reading device.

(3) Since there is only one optical system, there is no shift in the reading position for each of R, G, and B colors, and adjustment of the optical system is easy.

In the present invention, the insertion position of the filter is between the lens 2 and the sensor 3, but the same effect can be obtained even between the original 100 and the lens 2.

Further, although each filter is a separate plate in the above description, as shown in FIG. 5, each filter 4a, 4b, 4c is a single plate and is reciprocated vertically in the optical path. The same applies to the case. FIG. 5 (a) is a side view showing the filter in the optical path, and FIG. 5 (b) is a perspective view of the filter.
FIG. 6 is a perspective view showing the details of the filter switching mechanism of FIG. 5, and the filters 4a, 4b, 4c are fixed to a common substrate 6. The substrate 6 has a tip portion 7b of a leaf spring 7 to which a base portion 7a is fixed.
It is fixed by a screw 8. This filter switching mechanism has already been proposed by the present applicant (Japanese Patent Application No. 61-136901; application date Jun. 12, 1986).
Is driven by a driving means (not shown) composed of a coil and a magnet, and is driven in a sinusoidal shape in the vertical direction, whereby filter switching is performed. At the time of this switching, since the time for the center filter to pass through the optical path is shorter than that at the vertically inverted position, the width of the center filter is widened or the color with the highest sensitivity among the three colors is set to the center. The sine wave driving procedure is as shown in FIG. In this reading method, the width of the filter is determined by the width of the light flux passing through the filter, the necessary reading time (accumulation time) and margin, and the driving cycle. For example, the seventh showing a sine wave drive waveform
The reading in Fig. (A) is the accumulation time (FE), and the filter movement distance at that time is Is. T is the period. As shown in FIG. 7 (b), if the width of the light flux is K and the margin is Ma, the width of the filter is Becomes If the width of this filter is reduced, the driving stroke can be shortened, and high-speed driving and low power consumption can be achieved. In FIG. 7 (a), read, With the same accumulation time,
The moving distance of the filter is minimized and the width of the filter is reduced.

[Problems to be solved by the invention]

By the way, in the case of reading three colors, the sensitivities of the sensors for the respective colors are different, so that it is necessary to change the accumulation time to obtain the same level of sensor output. The sensitivity of the sensor is
For example, in reading R, G and B, R has the highest sensitivity and B has the worst. The ratio of B, G, and R storage times is about 3: 2: 1. Therefore,
In the reading as shown in FIG. 7 (a), the R reading having the shortest accumulation time is read so as to reduce the width of the center, and the B reading is read and the G reading is read.

In this case, t = B to t = C and t = D to t =
Since the light flux 10 passes through the boundary 9 of the filter between E as shown in FIG. 8, this portion cannot be used for reading. This boundary 9 is x (B) -x in FIG. 7 (a).
(C) or x (D) -x (E), and x (B) -x
It must be (C) K and x (D) -x (E) K. However, since the switching drive is a sine wave drive and the upper and lower strokes are the same, x for reading with long storage time
(B) -x (C) K is a necessary condition. In this case x
Since (D) -x (E) is larger than K than necessary, the movement of the filter in this portion is wasted, and the shortening of the stroke, that is, the speedup is prevented.

It is an object of the present invention to provide a color reading device that can realize a shortened filter switching stroke, that is, a higher speed.

[Means for solving problems]

The color reading device of the present invention is configured to drive a line image sensor and to drive three lines of three colors vertically arranged in stripes on the same substrate which is driven in a sine wave shape in the vertical direction across the reading light of the line image sensor. In a filter-switching color reading device that reads color images in a time-sharing manner in synchronization with switching of filters, movement of the substrate when switching between upper and center of the filters of the three colors arranged in parallel vertically The distance is equal to the moving distance of the substrate when switching the lower and central filters, and the midpoint between the reading start position X (C) and the reading end position X (D) of the central filter is Half cycle (t =
Each filter is arranged so that the position corresponding to T / 2), that is, the position of X (T / 2) = 0, is different, and the reading time for each color is set to compensate for the difference in sensitivity for each color. Configured differently.

[Action]

Since the filters are arranged as described above, the motion of the filters, which has been a problem in the past, is not wasted.

Therefore, it is possible to shorten the substrate stroke and increase the speed.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a perspective view showing a main structure of a color reading apparatus according to the present invention. In the figure, 11a, 11b and 11c are filters of three colors R, G and B. It should be noted that the same members as those in the related art are denoted by the same reference numerals as those in the related art.

The filters 11a, 11b, 11c are vertically arranged in stripes on the same substrate 12, and the substrate 12 is driven in a vertical sine wave shape across the reading light of the line image sensor 3. The base of each leaf spring 7 is fixed to a holding member 13 that holds the lens 2. In addition, the substrate 12 includes a magnet 14 arranged on both sides of the substrate 12 and a coil fixed to the substrate 12.
It is driven by the drive means consisting of 15.

In the present invention, the moving distance of the substrate 12 when switching the upper and central filters and the moving distance of the substrate 12 when switching the lower and central filters of the filters of three colors arranged in parallel vertically. The filters are arranged so that they are equal. This will be described below with reference to the filter sine wave drive waveform diagram shown in FIG.

The difference x (B) −x between the filter position x (B) at the reading end time point B and the filter position x (C) at the reading start time point C
(C) is the filter position x (D) at the time D when reading is completed.
And the difference x between the filter position x (E) at the start point E of reading
(D) −x (E) and the width K of the light flux. That is, in the present invention, the reading is not performed by the central distribution of t = T / 2 as in the conventional case, and x (B) and x
It is located in the center of (E). That is, the position to which the reading by the central filter is distributed becomes different from the position of the half cycle of the sine wave driving the filter (t = T / 2). As a result, there is no useless portion in the movement of the filter, so that the stroke can be minimized and the speedup can be realized.

The relationship among the accumulation time, the cycle T, the stroke St, and the width of the filter in this case will be described mathematically as follows.

x (t) = St · sin (2π · t / T) (1) On the other hand, the following equation holds as described above.

x (B) -x (C) = x (D) -x (E) (2) From the above, the following equation is obtained.

sin (2π ・ B / T) -sin (2π ・ C / T) = sin (2π ・ D / T) -sin (2π ・ E / T) (3) However, B = T / 4 + tR1 / 2 ... (4) E = 3 · T / 4−tR3 / 2 (5) DC = tR2 (6) Note that tR1, tR2, and tR3 are the storage times of reading and, respectively.

 D and C can be obtained from the equations (3) to (6).

Further, the expression (3) is as follows, where K is the width of the light flux.

St ・ (sin (2π ・ B / T) −sin (2π ・ C / T)) = K + 2Ma …… (7) 2 ・ Ma is the operating margin between the filters and is Ma for each color.
Is. From the equation (7), the stroke St is obtained as follows.

The filter widths F1, F2, and F3 for scanning are (distance traveled by the filter during scanning) + (light flux width K) + (margin
2Ma), and is as follows.

F1 = St (1-sin (2π ・ B / T) + K + 2Ma …… (9) F2 ＝ St (sin (2π ・ C / T)) − sin (2π ・ D / T) ＋ K + 2Ma …… (10) F3 = St (1 + sin (2π · D / T ₀ )) + K + 2Ma ... (11).

From the above relationships, the filter width, stroke, period, etc. can be designed.

〔The invention's effect〕

As described above, according to the present invention, unnecessary movement in the filter switching operation can be eliminated, so that the stroke can be shortened and the reading speed can be increased.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main structure of a color reading apparatus of an embodiment of the present invention, FIG. 2 is a filter sine wave driving waveform diagram of an embodiment of the present invention, and FIG. 3 is a conventional filter switching type color reading. FIG. 4A, FIG. 4B, and FIG. 4C are explanatory views of the color reading operation of the apparatus of FIG. 3, and FIG. 5A and FIG. Of the filter switching mechanism of FIG. 6, FIG. 6 is a perspective view showing the details of the filter switching mechanism of FIG. 5, and FIGS. 7 (a) and 7 (b) are explanatory diagrams of the sine wave driving procedure of the filter of FIG. FIG. 8 is a diagram for explaining the problems of the filter switching mechanism of FIG. 6, in which 3 is a line image sensor, 11a, 11b and 11c are filters of each color, 12 is a substrate, and 100 is an original.

Claims (1)

(57) [Claims] 1. A line image sensor (3) is driven, and stripes are vertically arranged on the same substrate (12) which is vertically sinusoidally driven across the reading light of the line image sensor (3). Three color filters (11a, 11b, 11)
In a filter-switching type color reading device for reading a color image in a time-sharing manner in synchronization with the switching of c), in the three color filters (11a, 11b, 11c) arranged in parallel in the upper and lower sides, the upper and middle ones are provided. The moving distance of the substrate (12) when switching the filters is equal to the moving distance of the substrate (12) when switching the lower and center filters, and
Each filter is arranged such that the midpoint between the reading start position and the reading end position of the central filter is different from the position corresponding to the half cycle of the sine wave of the three color filters (11a, 11b, 11c), and A color reading device, wherein different reading times are set for the respective colors in order to compensate for the difference in sensitivity for the respective colors.