JPH061243B2 - Document density detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a document density detecting device in a copying machine.

2. Description of the Related Art Conventionally, in a copying machine, in order to improve copy quality, an automatic image density control mechanism that detects the reflection density of a document and automatically controls image forming conditions to obtain an optimum image. There are some with. At this time, there are various methods for detecting the document density, for example, Japanese Patent Laid-Open No. 56-1.
As disclosed in Japanese Unexamined Patent Publication No. 10961, a side wall of a reflecting plate is provided with an opening long in the circumferential direction thereof to illuminate a document with a lamp, and reflected light from the document is transmitted to a light receiving element via an optical fiber. There is a method for detecting the document density. However, in the case of such a system, since the hole (opening) of the reflection plate is large, the original reflection function at the time of copying as the reflection plate is impaired, which adversely affects the image. Moreover, the reason why the optical fiber is used is to prevent the light receiving element from being affected by the heat of the lamp because the heat resistance of the light receiving element is low, but a plurality of detection elements including such an optical fiber are required. However, the cost will be high.

The present invention has been made in view of such a point, and it is possible to reduce the cost without using an optical fiber, maintain the reflection efficiency of the reflection plate, and thermally affect the original density detection sensor of the lamp. The purpose is to obtain an original document density detection device.

In order to achieve the above-mentioned object, the present invention provides a copying machine using a halogen lamp having a partial light emission filament as a light source, and a document density detection sensor is provided at an oblique position with respect to the partial light emission filament. A small hole is formed at a position of a reflecting plate that linearly connects the detection sensor and the partial emission filament, and a cooling means for cooling the document density detection sensor is provided at a position where cooling air is not applied to the partial emission filament. It is characterized by that.

An embodiment of the present invention will be described below with reference to the drawings. First, the present embodiment is applied to a copying machine of a document table moving type in which the halogen lamp 1 is used as a light source and the contact glass 3 on which the document 2 is placed moves in the direction of arrow A. The light from the halogen lamp 1 is condensed and reflected by the reflection plate 4 to expose and illuminate the original 2 on the contact glass 3. The reflected light from the original 2 is imaged on the photoconductor by the first mirror 5, a mirror (not shown), and a lens optical system to form an electrostatic latent image, which is used for a developing process and the like.

Here, the halogen lamp 1 is of a general partial-emission filament type for a copying machine, and has a structure in which light-emitting portions (filaments) 1a are dispersed and arranged in a tube according to a light distribution as shown in FIG. It is said that. More specifically,
Disk-shaped supporters 1b are provided at both ends of the light emitting portion 1a, and the light emitting portions 1a are fixed at the center of the tube diameter. The light emitting portions 1a are connected by a simple conductor 1c so that this portion does not emit light. There is. Such a halogen lamp 1 is CP
Electric power is supplied via a ramp regulator 7 controlled by a main control unit 6 mounted on the U.

Thus, a document density detection sensor 8 including a photodiode or the like is provided at a position diagonally rearward of the light emitting unit 1a, not directly behind it. The document density detecting sensor 8 is arranged in the light-shielding cylinder 9 and faces the contact glass 3 (document 2) side. The document density detection sensor 8 reads the document information by receiving the reflected light from the document 2. The minute photocurrent received by the document density detection sensor 8 is converted into a current voltage by an amplifier 10 and the main control unit is operated. 6 is input to the A / D converter. The light emitting portion 1a is formed on the reflection plate 4.
A small hole 4a is formed which guides light from the document 2 to the document 2 and allows the reflected light to enter the document density detection sensor 8. The position of the small hole 4a is a position on a line that linearly connects the light emitting unit 1a and the document density detection sensor 8 as shown in FIG. Contact glass 3
A cooling fan 11 is provided as a cooling means for cooling the illumination system in order to suppress the temperature rise of the surface.

In such a configuration, first, consider a case where the device of this embodiment is not devised. First, halogen lamp 1
Is an incandescent light bulb, which heats a heating element to an incandescent state with an electric current and emits light, and heat is remarkably generated. On the other hand, since the photodiode type document density detection sensor 8 generally has low heat resistance, it is important to take measures against the heat. However, when the optical fiber is not used, a small hole is generally formed in the reflecting plate 4 directly behind the light emitting portion 1a to irradiate the document. In this case, the original irradiation light reaches the original density detecting sensor 8 at the shortest distance as shown by the one-dot chain line a in FIG. For this reason, although the detection accuracy of the document density detection is improved, heat generation on the irradiation surface is increased. At this time, the illumination system is cooled by the cooling fan 11, but if the small hole formed in the reflection plate 4 and the light emitting portion 1a are directly opposed to each other, the cooling air from the cooling fan 11 will make the small hole. It directly hits the light emitting portion 1a through the halogen lamp 1 and locally cools the halogen lamp 1, which is not preferable in terms of lamp life.

However, according to this embodiment, the document density detection sensor 8
Is not directly behind the light emitting portion 1a but is diagonally rearward, and the small hole 4a is formed at a position on a straight line connecting the light emitting portion 1a and the document density detection sensor 8. Therefore, the small hole 4a is formed through the small hole 4a. Thus, the document irradiation light can be guided as shown by the broken lines in FIGS. 1 and 2. As a result, the document density detection sensor 8 is separated from the light emitting unit 1a,
It is possible to reduce the influence of temperature on the document density detection surface. Further, with such an arrangement, the cooling air from the cooling fan 11 does not directly hit the light emitting portion 1a, and the lamp life is not adversely affected. According to the above-mentioned document surface irradiation, since the small hole 4a is not formed directly behind the light emitting portion 1a, the illuminance on the document surface is large and the output of the document density detection sensor 8 is sufficient. By performing such an operation when the contact glass 3 is moved in the direction of arrow A, the document density information is obtained and is used for controlling the image forming conditions.

In the present embodiment, the example of application to the platen moving system has been described, but the system in which the platen is fixed and the document density detection sensor 8 moves together with the halogen lamp 1, the first mirror 5 and the like is similarly applied. Applicable.

Effect As described above, according to the present invention, since the small hole of the document density detection sensor reflection plate and the cooling means are provided at predetermined positions for the partial light emission filament of the halogen lamp, it is not necessary to use the optical fiber, and the cost is reduced. The document density detection sensor is not affected by the thermal effect of the partial emission filament and the reflection efficiency of the reflector is not impaired, and the document surface is illuminated with a sufficient amount of light for reliable detection. Is something that can be done.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a plan view showing a contact glass omitted, and FIG. 2 is a longitudinal side view thereof. DESCRIPTION OF SYMBOLS 1 ... Halogen lamp, 1a ... Light emission part (partial light emission filament), 4 ... Reflector, 4a ... Small hole, 8 ... Original density detection sensor

Claims (1)

[Claims] 1. A copying machine using, as a light source, a halogen lamp having a partial light emission filament, a document density detection sensor is provided obliquely to the partial light emission filament, and a document density detection sensor and the partial light emission filament are provided. Document density, characterized in that a small hole is formed at the position of a reflection plate that linearly connects the and the cooling means for cooling the document density detection sensor is provided at a position where cooling air is not applied to the partial light emission filament. Detection device.