JPH0949957A - Image reading device - Google Patents

Abstract

(57) [Summary] [Object] [Constitution] At normal temperature, the lens 15, the lens holding portion 30 of the lens barrel 17, and the fixing portion 31 are fixed on the reference member 18 so as to be in predetermined positions. When reading is started in this state, the CCD 16 generates heat, and this heat is transmitted to the reference member 18, and is further transmitted from the fixed portion 31 of the lens barrel 17 to the lens holding portion 30. After a lapse of a predetermined time, the temperature equilibrates,
The temperatures of the lens holder 30 of the lens barrel 17 and the reference member 18 are also in equilibrium. As the temperature rises, the lens barrel 17 thermally expands and the relative positional relationship between the lenses 15 changes, and the optical distance between the lens 15 and the reading unit focus and the depth of focus change. Further, since the lens barrel 17 and the reference member 18 also thermally expand, the distance between the rear end of the lens 15 and the CCD 16 also changes. here,
By using aluminum for the lens barrel 17 and steel having a smaller linear expansion coefficient than aluminum for the reference member 18, fluctuations in these distances are compensated, and C of the lens 15 is compensated.
The focus position with respect to CD16 does not change.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a scanner,
The present invention relates to an image reading device used in a fax machine, a copying machine, or the like.

[0002]

2. Description of the Related Art Conventionally, image reading apparatuses such as copying machines include an analog image reading apparatus and a digital image reading apparatus. FIG. 5 shows a sectional view of CCD peripheral parts of a digital image reading apparatus. The original on the original glass is irradiated with light from an illumination lamp, and the reflected light is guided to a plurality of lenses 1.
It is held by the lens holding part 3 and is fixed on the reference member 5 in a stable state by the fixing part 4.

As a result, the thrust position of the center of the lens 1 with respect to the optical axis is determined, the CCD 6 is fixed to the reference member 5, and the CCD 6 is connected to the driving CCD driver 7. The light flux passing through the lens 1 is imaged by the CCD 6 and image information is converted into an electric signal. The focus adjustment of the lens 1 and the CCD 6 is performed by moving the lens barrel 2 back and forth with respect to the optical axis, and the focus adjustment of the document on the document glass is performed by moving the reference member 5 forward and backward with respect to the optical axis. Adjusted by.

The electric signal of the image converted by the CCD 6 is
After the image is processed, it is converted into a laser signal, laser light is emitted from the laser light emitting element toward the polygon mirror, and a latent image is formed on the photosensitive drum.

In recent years, there has been a demand for digitization of office machines by networking with computers, and digitization of copy machines has also been emphasized. Against this background, scanners, fax machines, copiers, etc. equipped with digital image reading devices have become widespread.

[0006]

However, the digital image reading apparatus in the above-mentioned conventional example is a CCD.
Although the image is read by 6, the CCD 6 at the time of operation is improved by increasing the reading speed by improving the image processing capability.
The temperature rise is becoming severe. The temperature rise of the CCD 6 causes various harmful effects in addition to the destruction of the element, one of which is the problem of the temperature rise of peripheral parts.

To drive the CCD 6, a CCD driver 7 is connected to the CCD 6 and converts image information into an electric signal. At this time, the CCD 6 generates heat and this heat is transmitted to the reference member 5. Then, the light is transmitted from the fixed portion 4 of the lens barrel 2 to the lens holding portion 3. As a result, the lens barrel 2 thermally expands, and the relative positional relationship between the lenses 1 changes, so that the focal length of the lens 1 changes, which causes the CCD 6 to be out of focus. Further, since the reference member 5 also thermally expands, the relative positional relationship between the CC 5D and the lens 1 changes, and the CC
This may cause D6 to lose focus. This effect is C
The larger the calorific value of the CD 6, the more remarkable it is, and the larger the lens barrel 2 and the reference member 5 are, the more remarkable it is.

Therefore, in an image reading apparatus using a digital system, which has been used only in a field in which image processing is relatively slow, like a conventional product, this influence is offset by suppressing it within the depth of focus. . However, in realizing a super-high-speed digital monochrome copying machine having a high processing speed per image and a high-speed digital color copying machine having a large amount of information per image, the above-mentioned influence is caused by the depth of focus in the conventional configuration. It becomes difficult to keep the temperature within the range, and there arises a problem that the input image is out of focus when the temperature is raised.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide an image reading device in which the focus position of a lens does not change under the influence of temperature.

[0010]

An image reading apparatus according to the present invention for achieving the above object includes a lens barrel having a linear expansion coefficient K1 for holding a plurality of lenses, an image reading member, and the lens barrel. In an image reading apparatus configured with a reference member having a linear expansion coefficient K2 that defines the relative positional relationship of the image reading member, the lens focal length X1 at a normal temperature T1 of T2 which is a temperature higher than normal temperature. When the lens is arranged so as to be longer (or shorter) than the distance X2 from the lens to the image reading member at the time, and the linear expansion coefficient K1 is larger (or smaller) than the linear expansion coefficient K2. And

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a sectional view of the first embodiment. An illumination lamp 12 is arranged below the original glass 11, light from the illumination lamp 12 illuminates an original on the original glass 11, and mirrors 13 and 14, a plurality of lenses 15 and a CCD 16 are provided in the reflected light direction. And the lens 15 is held by a cylindrical lens barrel 17,
Further, the lens barrel 17 and the CCD 16 are fixed on the reference member 18. The output of the CCD 16 is connected to the laser light emitting element 19, the polygon mirror 20 is arranged in the emitting direction of the laser light from the laser light emitting element 19, and the mirror 21 is arranged in the direction of the laser light deflected and scanned by the polygon mirror 20. , 22, 23, and the photosensitive drum 24 are arranged.

An illumination lamp 12 is provided on the original on the original glass 11.
The reflected light is reflected by the mirrors 13 and 14, and is imaged by the CCD 16 through the plurality of lenses 15 to be converted into an electric signal. The converted electric signal is converted into a laser signal after image processing, laser light is emitted toward the polygon mirror 20 by the laser light emitting element 19, and the laser light is reflected by the mirrors 21, 22, and 23 and is hidden on the photosensitive drum 24. Form an image.

FIG. 2 is a plan view of CCD peripheral components, and FIG. 3 is a sectional view. The lens 15 is the lens holder 30 of the lens barrel 17.
And is fixed on the reference member 18 by the fixing portion 31 of the lens barrel 17. The reference member 18 is biased against the image reading unit base 33 by the leaf spring 32, and is supported at three points by the height adjusting screw 34. Further, the reference member 18 is fitted with the reference pin 35 crimped on the base 33 into the round long hole,
The thrust position is fixed.

The lens holding portion 30 of the lens barrel 17 is the fixed portion 3
It is composed of a cylinder smaller than 1 and is not in contact with the reference member 18. Then, the protrusion 30a provided at the end of the lens holding portion 30 is brought into contact with the square hole 36 of the reference member 18 to prevent the tilt of the lens barrel 17, and
The thrust position of the lens barrel 17 with respect to the optical axis is determined. Further, when the lens barrel 17 expands and contracts due to a temperature change, the frictional resistance received from the reference member 18 is only the protrusion 30a, so that the expansion and contraction of the lens holding unit 30 is not hindered.

A CCD driver 37 for driving is connected to the CCD 16 fixed to the reference member 18 to convert image information into an electric signal. Reference member 1 for focus adjustment
Positioning of 8 in the front-rear direction with respect to the optical axis is performed by fitting the positioning pin 39 crimped to the positioning member 38 into the round long hole of the reference member 18 and fixing the positioning member 38 to the base 33. . This positioning member 38
Is attached to the base 33 by a step screw 40 and follows the movement of the reference member 18 in the front-rear direction with respect to the optical axis, and the reference member 18 is fixed by fixing the positioning member 38 with the screw 41. Has been made possible.

The positional relationship among the lens 15, the lens barrel 17, and the CCD 16 will be described. In FIG. 4, the lens 15 has a focal length X of X1 and a focal depth δX of δX1 at room temperature (t = T1). In addition, the lens holder 17 is held by the lens holding portion 30 of the lens barrel 17, and the distance Z from the fixed portion 31 of the lens barrel 17 to the rear end of the lens 15 at this time is Z1. The distance Y between the rear end of the lens 15 and the CCD 16 is fixed to the reference member 18 so as to be Y1, and X1 = Y1 is adjusted at room temperature.

When reading is started in this state, the CCD 16
Heats up, is transferred to the reference member 18, and the lens barrel 1
7 from the fixed portion 31 to the lens holding portion 30. After a lapse of a predetermined time, the temperature is in an equilibrium state, and the temperatures of the lens holding portion 30 of the lens barrel 17 and the reference member 18 are also in an equilibrium state at t = T2. With this temperature rise, the lens barrel 17 thermally expands,
Since the relative positional relationship between the lenses 15 changes, the optical distance X between the lens 15 and the reading unit focus becomes X2 (<X
1), the depth of focus δX changes to δX2. In addition, lens barrel 1
Since 7 and the reference member 18 also thermally expand, the distance Y between the rear end of the lens 15 and the CCD 16 changes to Y2.

In this embodiment, the lens barrel 17 is made of aluminum having a linear expansion coefficient K1 of about 23 × 10 ⁻⁶ , and the reference member 18 has a linear expansion coefficient K2 of about 11 × 1.
Using the 0 ^-6 steel, steel has a smaller coefficient of linear expansion than aluminum. Further, the optical distance X1 between the lens 15 and the focal point of the reading portion at room temperature (T1 = 20 ° C.) is 100, and the distance Z1 from the fixed portion 31 of the lens barrel 17 to the rear end of the lens 15 is 120. Rear end of lens 15 and CCD 16
The distance Y1 of is adjusted to 100.

When reading is started in this state, the CCD 1
6 heats up and heat is dissipated to the peripheral portion, so that the temperature T2 of the lens holding portion 30 of the lens barrel 17 and the reference member 18 is in an equilibrium state at 50 ° C. At this time, the optical distance X2 between the lens 15 and the focal point of the reading unit changes to X2 = 99.98, and the depth of focus δX2 changes to about 0.02 (20 μm). The distance Z2 from the fixed portion 31 of the lens barrel 17 to the rear end of the lens 15 is as follows. Z2 = {1 + K1 ・ (T2-T1)} ・ Z1 = {1 + 23 ・ 10 ^-6・ (50-20)} ・ 120 = 120.0828

The fixed portion 3 of the lens barrel 17 of the reference member 18
The distance (Z + Y) from 1 to the CCD 16 is as follows. (Z + Y) = {1 + K2. (T2-T1)}. (Z1 + Y1) = {1 + 11.10.sup.- ^6. (50-20)}. 220 = 220.0726

Therefore, the distance Y2 between the rear end of the lens 15 and the CCD 16 is as follows. Y2 = {1 + K2. (T2-T1)}. (Z1 + Y1)-{1 + K1. (T2-T1)}. Z1 = 220.0726-120.0828 = 99.9898

In order to obtain an in-focus input image even at the temperature t = T2, the rear end of the lens 15 and the CCD 16
Is the optical distance between the lens 15 and the focal point of the reading unit.
The focal depth of X2 must be within ΔX2. Therefore, the distance Y2 between the rear end of the lens 15 and the CCD 16 may be set to a value that satisfies the following expression. X2-δX2 / 2 ≤ Y2 ≤ X2 + δX2 / 2

In this embodiment, when numerical values are entered in X2, ΔX2, and Y2, the following relationship is established, and it is confirmed that a good input image in focus can be obtained. 99.98-0.02 / 2 ≦ 99.9898 ≦ 99.98 + 0.02 / 2 99.97 ≦ 99.9898 ≦ 99.99

Next, in the second embodiment, the lens barrel 17
The material used is brass with a linear expansion coefficient K1 of about 17 × 10 ^-6 , and the linear expansion coefficient K2 of the reference member 18 is about 23 × 10 ^-6.
Aluminum is used. At room temperature (T1 = 2
Optical distance X1 between lens 15 and reading unit focus at 0 ℃)
Is X1 = 60, and the distance Z1 from the fixed portion 31 of the lens barrel 17 to the rear end of the lens 15 is Z1 = 80. Therefore,
The distance Y1 between the rear end of the lens 15 and the CCD 16 is adjusted to Y1 = 60.

When reading is started in this state, the CCD 1
6 heats up and heat is dissipated to the peripheral portion, and the temperature T2 of the lens holding portion 30 of the lens barrel 17 and the reference member 18 is in an equilibrium state at, for example, = 50 ° C. The optical distance X2 between the lens 15 and the focal point of the reading unit is X2 = 60.045, and the depth of focus δX2 is about 0.03 (30 μm).

At this time, the distance Z2 from the fixed portion 31 of the lens barrel 17 to the rear end of the lens 15 is as follows. Z2 = {1 + K1 · ( T2-T1)} · Z1 = {1 + 17 · 10 -6 · (50-20)} · 80 = 80.041

Further, the fixed portion 3 of the lens barrel 17 of the reference member 18 is fixed.
The distance from 1 to the CCD 16 (Z + Y) is as follows. (Z + Y) = {1 + K2 · (T2-T1)} · (Z1 + Y1) = {1 + 23 · 10 -6 · (50-20)} · 140 = 140.097

Therefore, the distance Y2 between the rear end of the lens 15 and the CCD 16 is as follows. Y2 = {1 + K2 ・ (T2-T1)} ・ (Z1 + Y1)-{1 + K1 ・ (T2-T1)} ・ Z1 = 140.097-80.041 = 60.56

In order to obtain an in-focus input image even at the temperature t = T2, the rear end of the lens 15 and the CCD 16
It is necessary to keep the distance Y2 of within the focal depth ΔX2 of the optical distance X2 between the lens and the reading unit focus. Therefore, lens 1
The distance Y2 between the rear end of the CCD 5 and the CCD 16 should satisfy the following equation similar to the above. X2-δX2 / 2 ≤ Y2 ≤ X2 + δX2 / 2

In the present embodiment, when the numerical values are substituted, the following formula is obtained, and it is confirmed that a good input image in focus can be obtained. 60.045-0.03 / 2 ≦ 60.056 ≦ 60.045 + 0.03 / 2 60.03 ≦ 60.056 ≦ 60.06

[0031]

As described above, in the image reading apparatus according to the present invention, the linear expansion coefficient K1 of the lens barrel is set to a linear expansion coefficient K2 different from that of the reference member, and the lens up to the focal point of the reading unit at room temperature t = T1. The lens is arranged so that the optical distance X1 is longer (or shorter) than the optical distance X2 to the lens and the reading section focus when the temperature is t = T2 which is higher than room temperature, and the linear expansion coefficient K1 of the lens barrel is used as a reference. By making the linear expansion coefficient K2 larger (or smaller) than the member K2, an input image in focus can be obtained even if the temperature rises and the lens position changes.

[Brief description of drawings]

FIG. 1 is a sectional view of an example.

FIG. 2 is a plan view.

FIG. 3 is a cross-sectional view of a lens barrel.

FIG. 4 is an explanatory diagram of distances between respective parts.

FIG. 5 is a plan view of a conventional example.

[Explanation of symbols]

 11 Original Glass 12 Illumination Lamp 15 Lens 16 CCD 17 Lens Barrel 18 Reference Member 19 Laser Light Emitting Element 20 Polygon Mirror 24 Photosensitive Drum

Claims (6)

[Claims] 1. A linear expansion coefficient K1 for holding a plurality of lenses.
In the image reading device constituted by a lens barrel of (1), an image reading member, and a reference member having a linear expansion coefficient K2 that defines a relative positional relationship between the lens barrel and the image reading member, the lens at room temperature T1 The focal length X1 is arranged such that the lens is longer (or shorter) than the distance X2 from the lens to the image reading member when the temperature is T2 which is higher than room temperature, and the linear expansion coefficient K1 An image reading device having a coefficient of expansion larger (or smaller) than K2. 2. The focal length of the lens at temperature T2 is X
2, the distance from the lens to the image reading member Y2,
When the depth of focus is δX2, X2-δX2 / 2 ≤ Y2 ≤ X2 + δ
The image reading apparatus according to claim 1, wherein the lens barrel and the image reading member are fixed to the reference member so as to satisfy X2 / 2. 3. The lens barrel comprises a lens holding portion and a fixing portion to the reference member, and when the lens holding portion expands and contracts due to temperature change, the reference member causes the lens to pass through the fixing portion. Claim 1 which did not prevent expansion and contraction of a holding part.
The image reading apparatus described in 1. 4. The image reading apparatus according to claim 3, wherein the lens holding unit has a cylindrical shape smaller than the fixing unit. 5. The image reading apparatus according to claim 3, wherein the lens holding portion is provided with a protrusion for preventing the lens barrel from tilting with respect to the reference member. 6. The image reading device according to claim 1, wherein the image reading member is a CCD.