JPS63294067A - Image reader - Google Patents

Abstract

PURPOSE:To prevent the variance of the quantity of light, to generate a stable image pickup condition, and to output image information of high quality by providing a cooling air shielding member between a lamp housing and an original platen glass to prevent the quick temperature change of a fluorescent lamp. CONSTITUTION:When a cooling fan 70 is operated because of the temperature rise of a device, a cooling air shielding member 4 provided in the space part between an original platen glass 1 and fluorescent lamps 5 and 6 which is the flow passage of cooling air acts so that cooling air does not directly act upon tube walls of lamps 5 and 6. Thus, A local temperature fall of tube walls of lamps 5 and 6 is prevented, and a temperature sensor 46 brought into contact with the tube wall of the lamp 5 can entirely manage the temperature of tube walls of lamps 5 and 6. Further, the variance of the quantity of light accompanied with the local temperature fall of tube walls of fluorescent lamps is prevented. Since the member 4 consisting of a shielding material line a fur brush is provided between the glass 1 and the upper part of a lamp housing 41 in this manner, the variance of the quantity of light is prevented and a stable image pickup condition is generated to output image information of high quality.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an image reading apparatus, such as a facsimile machine or a copying machine, in which an optical image of a document obtained by an exposure optical system that scans while illuminating the surface of the document is formed in an imaging unit.

[Background of the invention]

In image reading devices, an optical image of the document surface obtained by exposure scanning is generally formed on a solid-state imaging device such as an image sensor installed around the optical axis via an imaging lens system. There is. For example, in an image reading device of a multicolor image forming apparatus, the optical image of the document surface obtained by exposure scanning is passed through an imaging lens system, and then separated into lights by a light splitting means such as a prism installed behind the imaging lens system. after,
An image is formed on an image sensor that receives light in each channel. In an image reading device in which a document table is fixed and an optical system is moved, a document placed on a document table glass is illuminated in a strip shape by a moving light source. An optical image of the document obtained by being irradiated by the light source is transmitted to a first mirror that moves together with the light source, and tA2. It is reflected and guided by the third mirror. The reflected and guided original light image then passes through a fixed imaging lens and is imaged on an image sensor also fixed behind the imaging lens. A rod-shaped halogen lamp or fluorescent tube is used as a light source that illuminates the document surface. Fluorescent lamps are often used because halogen lamps generate a large amount of heat when continuously lit. FIG. 6 is a characteristic diagram showing the relationship between the light amount and temperature of a fluorescent lamp. In the figure, the horizontal axis indicates temperature, and the vertical axis indicates relative light amount. Generally, the amount of light of a fluorescent lamp changes as the temperature changes. Especially when the tube wall temperature is low at the beginning of lighting, the amount of light is noticeably small. As the tube wall temperature rises, the light intensity also increases and stabilizes at a constant value. As the tube wall temperature further increases, the amount of light gradually begins to decrease. In addition to the above-mentioned light source, heat sources that increase the ambient temperature within the image reading apparatus include a drive motor within the apparatus, and conductive heat and radiant heat from outside the apparatus. When the ambient temperature inside the device rises due to these various heat sources, the temperature rise is detected and a cooling fan is activated to prevent an excessive rise in temperature inside the device.

[Problems to be Solved by the Invention] However, when attempting to lower the ambient temperature inside the device by operating a cooling fan, the portions that are directly in contact with the cooling air near the cooling air ventilation path are compared to other areas. The temperature may drop suddenly. The space between the fluorescent lamp that illuminates the document and the document table glass also serves as this ventilation path. Moreover, since the spacing between these spaces is narrow, the speed of the cooling air increases. As a result, the cooling effect of the cooling air is further enhanced, and the portion of the fluorescent lamp that is directly exposed to the cooling air is locally cooled. In this case, the tube wall temperature distribution of the fluorescent lamp becomes uneven and the temperature W
Difficult to fill. Furthermore, since the temperature of the W wall of the fluorescent lamp fluctuates rapidly, the amount of light from the fluorescent lamp also fluctuates accordingly. The present invention has been made in view of the above-mentioned shortcomings of the prior art, and provides stable imaging conditions by preventing rapid temperature changes in fluorescent lamps and preventing fluctuations in the light amount of the fluorescent lamps due to temperature changes. The object of the present invention is to provide an image reading device that can create images and output high-quality image information.

[Means for solving the problem 1] The above purpose is to expose and scan an original on the original platen glass using a fluorescent lamp in an optical system, and to form an optical image of the obtained original on an imaging unit. In the reading device, a lamp housing that houses the fluorescent lamp in a light-blocking state;
This is achieved by an image reading device characterized in that a means for generating cooling air is provided in the device facing the housing, and a cooling air shielding member is provided between the upper part of the housing and the document table glass. Ru. Embodiments Prior to a detailed description of the present invention, the general functions of an image reading device will first be described. FIG. 4 is a configuration diagram of the image reading device. In the same figure,
Reference numeral 1 denotes a document table glass, and the original M42 is placed on this document table glass. The original W42 includes fluorescent lamps 5 and 6 provided in an exposure light source unit 40 that moves on a slide rail 3.
irradiated by. The movable mirror unit 80 has mirrors 9a and 9b that move on the slide rail 3, and the first mirror 7 provided in the exposure light source unit 40
In combination with this, the optical image of the original fr 42 on the document table lath 1 is guided to the imaging unit 20. The exposure light source unit 40 and the movable mirror unit 80 are
They are driven in the same direction at speeds of 1 and 1/2v, respectively, by a driving device (not shown) consisting of a stepping motor, pulley, wire, etc. A standard white plate 16 is provided on the back side of the front end of the document table lath 1, and is configured so that a standard white signal can be obtained before the start of document reading scanning. The imaging unit 20 includes a lens 21 as an imaging lens system.
, a prism 22 as a photolysis means, a first reading board 24, a red channel (hereinafter referred to as R-ah) CCD 27 as a line image sensor, and a second reading board 26.
, cyan channel (hereinafter referred to as C-ch) CCD25
It consists of First mirror 7, mirror 9a, mirror 9
The original light image transmitted by b is focused by a lens 21 and separated into a C-ah image and a R-ah image by a gicroic mirror provided in a prism 22. Then, the C-ah image is formed on the light receiving surface of the C-ah CCD 25 provided on the first reading board 24, and the R
-ah image is R provided on the t52 reading board 26.
-ah Image is formed on the light receiving surface of CCD 2. As the fluorescent lamp 5.6 for illuminating the document, a commercially available warm white fluorescent lamp is used in order to prevent particular colors from being emphasized or discounted based on the light source when reading a color document. In addition, to prevent flickering, the lights are powered by a 40 K II z high frequency power source. The fluorescent lamps 5 and 6 are equipped with a heater 5e using Bonostar to maintain a constant temperature of the tube wall or promote heating up.
Warmed at 6c. Figure #1 is a side sectional view of an optical system showing an embodiment of the present invention;
The figure is a perspective view of the exposure light source unit 40 of the optical system.
The figure is a partial side sectional view of the exposure light source unit 40. In these figures, 4 is a cooling air shielding member, 41 is a lamp housing, 46 is a temperature sensor, 70 is a cooling 7 amp, and 90 is a cooling air shielding member.
is the frame. The cooling air shielding member 4 is a bristle brush-shaped shielding member. This bristle brush-shaped shielding member is made of a flexible fibrous material that does not cause any trouble to the document table glass 1 even if it comes into contact with the glass. This fibrous body is an organic or inorganic fibrous body having a diameter of 0.2 to 0.41 mm. This cooling air shielding member 4 has a fibrous body forming V# planted in a base cloth or base paper at its root portion, and this base cloth or base paper can be attached using double-sided adhesive tape or directly. Attach to the lamp housing by applying adhesive, etc. The cooling air shielding member 4 has a width of 2 to 3 inches, a fiber length of 6 to 7 inches, and has a length equivalent to the length of the fluorescent lamp. When the cooling air shielding member 4 is attached so as not to come into contact with the document table glass 1, the cooling air shielding member itself may be formed of a glass plastic molded product, a metal sheet metal product, or the like. The fluorescent lamps 5 and 6 are so-called aperture type fluorescent lamps having transparent portions 5m and 6a on which no fluorescent material is applied in the longitudinal direction. Since these fluorescent lamps 5.6 are directed toward the document to which the transparent portions 5a and 6a are to be illuminated, the surface of the document can be efficiently illuminated. The lamp housing 41 is made of a metal plate and holds the fluorescent lamps 5 and 6. The lamp housing 41 surrounds the fluorescent lamps 5, 6 below and on the sides.
This prevents light from leaking in directions other than the direction of the document. The upper surface of the lamp housing 41 is open so that the original 2 is irradiated with light emitted from the transparent lamps 15a and 6a of the fluorescent lamps 5 and 6. The lower surface has an elongated slit opening IB 41b for guiding the optical image of the original 2 to the optical system. This lamp housing 41 has black anti-reflection treatment applied to both the inner and outer surfaces. The cooling air shielding member 4 is attached to the upper part of the side surface 41c of the lamp housing 41 facing the cooling air of the cooling fan 70. This temperature sensor 46 is attached to a sensor mounting plate 47 provided with printed wiring. The sensor mounting plate 47 to which the temperature sensor 46 is attached is attached to the lamp housing 41.
On the upstream side of the optical system in the scanning/moving direction! ? ! It is fixed to the lamp housing 41 from the rear of the provided hole 41a. The temperature sensor 46 is loosely inserted into the lamp housing song through the hole 41a of the lamp housing 41, and is held in contact with the tube wall of the fluorescent lamp. The temperature sensor 46 detects the tube wall temperature of the fluorescent lamp and outputs an activation signal for the cooling fan 70 when the temperature exceeds a predetermined temperature. The output signal from the temperature sensor 46 is output from the sensor mounting plate 4.
The sensor lead wire 46a1 connected to the sensor is input to the tube wall temperature control section (not shown) via the energizing relay section 48 and the flexible wiring board 49. The cooling fan 70 is attached to a frame 90 of the image reading device, takes in air from outside the device through an opening 90a of the frame 90, circulates this air, and then passes the air through the opening 90a of the frame 90. 90b to the outside of the device. The embodiment of the present invention has the above configuration, and its operation will be explained below. When a fluorescent lamp for an image reading device is turned on, its tube wall temperature is low, so a heater 5 is used to raise the fluorescent lamp to a predetermined temperature.
Warm at 6c. As the image reading device operates, the ambient temperature inside the device gradually increases. When the ambient temperature rises above a certain temperature, the tube wall temperature of the fluorescent lamp 5.6 also rises, and the temperature sensor 46 detects this temperature and outputs an activation signal for the cooling fan 70. Cooling 7 tons 70
As a result of this operation, air from outside the device is taken into the device, and the ambient temperature inside the device decreases. When the cooling fan 70 is activated, the document table glass 1 and the fluorescent lamp 5 serve as a ventilation path for cooling air.
．． A cooling air shielding member 4 is provided in the space between the fluorescent lamps 5 and 6 to prevent the cooling air from acting directly on the tube walls of the fluorescent lamps 5 and 6. It is now possible to prevent temperature drops. By doing so, the temperature sensor 46 brought into contact with the tube wall of the fluorescent lamp 5 detects a representative value of the overall temperature distribution of the tube wall temperature of the fluorescent lamp, allowing accurate temperature control. It has also become possible to prevent fluctuations in the amount of light caused by local temperature drops on the tube wall of the fluorescent lamp. FIG. 5 is a block diagram of a tube wall temperature control circuit for the fluorescent lamps 5 and 6. A temperature signal 128 output from the temperature sensor 46 attached to the fluorescent lamp 5 is simultaneously supplied to two comparators 131 and 132. The comparator 131 compares the temperature signal 128 with a reference signal 137 supplied from a reference voltage generator 133 containing preset information. When the tube wall temperature of the fluorescent lamp 5 is lower than the set temperature, an H level signal is supplied to the heater drive circuit 135. Then, while the H level signal is output from the comparator 131, the heater drive circuit 135 controls the heaters 5c and 6c of the fluorescent lamps 5 and 6.
・Turn on the electricity and heat it. Fluorescent lamp 5! If the wall temperature is higher than or equal to the set temperature, an L level signal is supplied to the heater drive circuit. Then, while the L level signal is output from the comparator 131, the drive circuit 135 does not energize the heaters 5c and 6c. Further, the humpator 132 compares the temperature signal 128 with a reference signal 138 supplied from a reference voltage generator 134 containing preset information. If the tube wall temperature of the fluorescent lamp 5 is higher than the set temperature,
When the signal is supplied to the cooling fan drive circuit 136, the cooling fan is operated while the signal is output from the comparator 132, and the fluorescent lamps 5 and 6 are operated.
to cool down. In this way, the fluorescent lamps 5, 6 can maintain an appropriate temperature and generate a stable maximum amount of light. As explained above, by providing the cooling air shielding member 4, the cooling air from the cooling fan 70 is transmitted to the fluorescent lamps 5,
6 no longer acts directly on the tube wall. The cooling air from the cooling fan 70 first lowers the ambient temperature inside the device. The fluorescent lamps 5 and 6 are cooled down with uniform temperature distribution throughout in this atmosphere.
It is now possible to prevent the harmful effects that would otherwise occur due to the direct action of cooling air.

【Effect of the invention】

According to the present invention, the cooling air inside the device does not directly act on the tube wall of the fluorescent lamp, so that local cooling of the lamp tube wall can be prevented. Therefore, according to the present invention, it is possible to prevent rapid temperature changes in the fluorescent lamp, prevent fluctuations in the light amount of the fluorescent lamp due to temperature changes, create stable imaging conditions, and output high-quality image information. We are now able to provide a new image reading device.

[Brief explanation of drawings]

FIG. 1 is a sectional side view of an optical system of an image reading apparatus showing an embodiment of the present invention, FIG. 2 is a perspective view of an exposure light source unit of the optical system, and FIG. 3 is a partial side view of the exposure light source unit. 4 is a cross-sectional view of the image reading device, and FIG. 5 is the tube wall temperature i! of the fluorescent lamp. FIG. 6, a block diagram of the ill 11 portion, is a characteristic diagram showing the relationship between light amount and temperature in a fluorescent lamp. 1... Original table glass 2... Original 4... Cooling air shielding member 5.6... Fluorescent lamp 20... Imaging unit 40... Exposure light source unit (optical system) 41... Lamp Housing 46...Temperature sensor 7
0... Cooling fan 80... Movable mirror 1 knit (optical system) Applicant Roku Konishi Photo Industry Co., Ltd. Figure 5 Figure 6 5 degrees ji0]

Claims (1)

[Claims] In an image reading device that exposes and scans a document on a document platen glass using a fluorescent lamp in an optical system, and forms an optical image of the document on an imaging unit, the lamp accommodates the fluorescent lamp in a light-shielded state. A housing and a means for generating cooling air in the device facing the housing,
An image reading device characterized in that a cooling air shielding member is provided between an upper part of the housing and the document table glass.