JP3301783B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for illuminating an original with a light source and reading the original with light reflected from the original.

[0002]

2. Description of the Related Art Conventionally, in an image reading apparatus, as a light source,
A tubular light source such as a fluorescent tube is often used. However, since the light output of the tubular light source varies depending on the tube wall temperature and the light amount fluctuates, reading is performed after the light amount is stabilized. However, it is necessary to wait until the light amount becomes stable before reading an image, and the image cannot be read immediately. Thus, Japanese Patent Laid-Open Publication No. Sho 62-164342 discloses a method in which a fluorescent lamp is previously heated to a temperature at which the amount of light emitted from the fluorescent lamp is stabilized using a heating means such as a heater.

Further, in the conventional image reading apparatus, fine control of the amount of light emitted from the fluorescent lamp cannot be performed only by controlling the tube wall temperature of the fluorescent lamp. Lights the inverter PWM (Pulse
The light emitted from the fluorescent lamp is controlled to have a constant light amount by Width Modulation (pulse width modulation) control. As shown in FIG. 1, since the fluorescent light 2 is provided with a heater 3 at the installation location of the conventional light amount detection sensor 1, when the light emitted from the fluorescent lamp 2 is to be detected, the heater 3 is opened. The part that does
The fluorescent light 2 must be provided in the vicinity of a portion of the document 4 where the fluorescent lamp 2 emits light.

[0004]

In the conventional image reading apparatus, if a light amount detection sensor is provided near a portion of the original 4 where the fluorescent lamp 2 irradiates light, the light directly illuminated by the fluorescent lamp 2 and the original 4 Since the light including the light irregularly reflected by the light is detected by the light amount detection sensor 1, the light amount emitted from the fluorescent lamp 2 cannot be controlled normally.
Further, since the reflectance varies depending on the type and color of the document, the amount of reflected light for the document cannot be deleted by the arithmetic processing.

The present invention has been made in view of the above problems, and has as its object to detect only light emitted from a fluorescent lamp without being affected by light irregularly reflected by a document.

[0006]

In an image reading apparatus for illuminating an original with a light source and reading the original with reflected light from the light source, a heat source is provided along the outer shape of the light source and heats the light source. An opening in the center of the heat source for guiding light emitted from the light source to the back of the heat source; and detecting only light directly disposed on the heat source opening and emitted from the heat source opening. And a control unit for controlling the light source by the light amount detection sensor.

[0007]

According to the present invention, by providing a light quantity sensor near the heat source opening leading to the back of the heat source, light diffusely reflected by the document is not received.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to the present invention will be described with reference to FIGS. 2, 3, 4, and 5. FIG. FIG. 2, FIG.
1 is a diagram showing an embodiment of the image reading apparatus of the present invention. 2 and 3, the light illuminated from the fluorescent lamp 21 is reflected by the original 22 and is reflected by the first mirror 2 as reflected light.
3, second mirror 24, third mirror 25, lens 26
, Image data in the main scanning direction is read by a photoelectric conversion element 27 such as a CCD. The image data in the sub-scanning direction includes an illumination unit formed by the fluorescent lamp 21 and the first mirror 23 and a reflection unit formed by the second mirror 24 and the third mirror 25 along the document surface. The image is read by relatively moving in the sub-scanning direction.

A heater 28 as shown in FIG. 4 is attached to the fluorescent lamp 21 so that the tube wall temperature of the fluorescent lamp 21 is set to a predetermined temperature (the maximum light amount is obtained when the tube wall temperature is set to about 40 ° C.). It is known to play a role in keeping). 4 and 5, reference numeral 41 denotes a heater wire, which is fixed to the same shape as the fluorescent tube wall shape by an insulating material.
We use as. Reference numeral 42 denotes a temperature sensor provided on the rear wall surface of the heater 28 and detecting a heating temperature heated by the heater wire 41. An opening 43 is provided in a part of the insulating material that fixes the heater wire 41 to the fluorescent tube wall shape, and a heat source opening that guides light emitted from the fluorescent lamp 21 to the back of the heater 28. In this embodiment, the heat source opening 4
3 has only one small round hole, but is not limited to this embodiment, and may have any shape as long as it can guide light emitted from the fluorescent lamp 21 to the back of the heater 28. Or more than one. Reference numeral 29 denotes a light amount detection sensor that detects light guided by the heat source opening 43. The light quantity detection sensor 29 is provided on the heater 28 such that the reflected light from the document is not mixed as shown in FIG. 3 even if it is directly disposed on the heat source opening 43 provided on the heater 28 as shown in FIG. Even if it is arranged near the heat source opening 43,
either will do.

A control unit (not shown) comprises a CPU and the like. Based on the temperature information detected by the temperature sensor 42, the heater 28 controls the temperature of the tube wall of the fluorescent lamp 21 to a predetermined temperature. Is controlled. In addition, based on the light amount information emitted from the fluorescent lamp 21 detected by the light amount detection sensor 29, a PWM (Pulse Width Modulation) is performed by an inverter unit (not shown).
(ion: pulse width modulation) control to keep the amount of light emitted from the fluorescent lamp 21 constant.

With the above arrangement, only the amount of light emitted from the fluorescent lamp can be detected, so that accurate control of the amount of light of the fluorescent lamp becomes possible.

[0012]

According to the present invention, only the amount of light emitted from the fluorescent lamp can be detected, so that it is possible to control the amount of light of the fluorescent lamp accurately, and to obtain a highly accurate image signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a conventional image reading apparatus.

FIG. 2 is a diagram showing an embodiment of the image reading apparatus of the present invention.

FIG. 3 is a diagram showing an embodiment of the image reading apparatus of the present invention.

FIG. 4 is a view showing one embodiment of a heater portion of the present invention.

FIG. 5 is a diagram showing an embodiment of an arrangement relationship among a fluorescent lamp, a heater, and a light amount detection sensor.

[Description of Signs] 1, 29 Light intensity detection sensor 2, 21 Fluorescent lamp 3, 28 Heater 4, 22 Document 41 Heater wire 43 Heat source opening

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Takayuki Sugitani 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-61-195072 (JP, A) JP-A Sho 59-44796 (JP, A)

Claims (1)

(57) [Claims] 1. An image reading apparatus for illuminating an original with a light source and reading the original with reflected light from the light source, comprising: a heat source provided along the outer shape of the light source to heat the light source; An opening is provided at the center, and a heat source opening that guides light emitted from the light source to the back of the heat source, and only light that is arranged directly at the heat source opening and emitted from the heat source opening is detected. An image reading apparatus, comprising: a light amount detection sensor that emits light; and a control unit that controls the light source using the light amount detection sensor.