JP2709062B2 - Image density control method - Google Patents
Image density control methodInfo
- Publication number
- JP2709062B2 JP2709062B2 JP62252015A JP25201587A JP2709062B2 JP 2709062 B2 JP2709062 B2 JP 2709062B2 JP 62252015 A JP62252015 A JP 62252015A JP 25201587 A JP25201587 A JP 25201587A JP 2709062 B2 JP2709062 B2 JP 2709062B2
- Authority
- JP
- Japan
- Prior art keywords
- latent image
- image carrier
- reflectance
- toner
- signal corresponding
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/50—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control
- G03G15/5033—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control by measuring the photoconductor characteristics, e.g. temperature, or the characteristics of an image on the photoconductor
- G03G15/5041—Detecting a toner image, e.g. density, toner coverage, using a test patch
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G2215/00—Apparatus for electrophotographic processes
- G03G2215/00025—Machine control, e.g. regulating different parts of the machine
- G03G2215/00029—Image density detection
- G03G2215/00033—Image density detection on recording member
- G03G2215/00037—Toner image detection
- G03G2215/00042—Optical detection
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Color Electrophotography (AREA)
- Dry Development In Electrophotography (AREA)
- Control Or Security For Electrophotography (AREA)
Description
【発明の詳細な説明】
（技術分野）
本発明は、画像濃度制御方法に関する。
（従来技術）
潜像担持体表面の反射率に応じた信号と、定められた
条件で上記潜像担持体上に形成されたトナー像の反射率
に応じた信号を比較することにより、現像バイアス電圧
や帯電量、露光光量等の作像条件を制御し、画像濃度を
制御する方法は複写機やプリンターに関連して知られて
いる。
また、近来、カラー複写機やカラープリンター、多色
や２色の複写機やプリンターなどカラートナーを用いる
画像記録装置が増えてきている。
潜像担持体表面やトナー像の反射率に応じた信号を得
るには一般に、フォトセンサーを用いて行われる。フォ
トセンサーは、光源と受光素子とを一体的に組付けたも
のであり、光源からの光を潜像担持体表面やトナー像に
照射し、反射光を受光素子にて受光し光電変換して信号
化する。このようなフォトセンサーに関連して、検出角
を以下のように定義する。即ち、潜像担持体などの反射
率検出対象物に照射する光の入射角と、受光素子に受光
される反射光の反射角の和を以て検出角と称するのであ
る。
ところで、トナー像からの反射率を検出するのは、潜
像担持体上に一定の条件で形成されたトナー像の反射率
により、トナー像の濃度を知り、それに基づいて記録す
べき画像の濃度を制御するためであるが、トナー像がカ
ラートナーで形成されて居る場合、フォトセンサーの感
度は検出角に依存することが分かった。
例えば、第２図（Ａ）に示すフォトセンサーS1では、
光源20から潜像担持体10に照射される光と、受光素子22
に受光される反射光とのなす検出角は60゜であるが、潜
像担持体10上に赤色トナーが付着していると、その付着
量に応じて、フォトセンサーの出力信号電圧は第３図の
曲線３−２のように変化する。第３図の縦軸は出力電圧
信号、横軸は赤色トナー付着量である。しかるに、第２
図（Ｂ）に示すような、光源30から照射される光と受光
素子32の受光する反射光とのなす検出角が120゜のフォ
トセンサーＳを用いると出力信号電圧は赤色トナーの付
着量に応じて第３図の曲線３−１の如くに変化する。従
って、定められた条件で上記潜像担持体上に形成された
カラートナー像の濃度を検出するためには、検出角の大
きいフォトセンサーを用いて高感度の検出を行うのが好
ましい。一方、第３図で横軸のトナー付着量が０の時の
フォトセンサー出力信号電圧は潜像担持体10そのものの
反射率を与えるものであり、トナー像の濃度検出は、潜
像担持体表面自体の反射率による信号電圧を基準電圧v
refとし、トナー像の反射率による信号電圧Vspとの比V
sp/vrefによって行われ、その値に基づき画像濃度制御
が行われる。しかるに、フォトセンサーの感度が高くな
ると、潜像担持体表面に僅かな残留トナーが付着してい
ても、フォトセンサーはこれを検出し、基準電圧vrefが
変化することになる。
従来、現像部においては、常時、潜像担持体の表面が
現像剤と接触している。一方、潜像担持体の表面には、
若干の電荷が残留しているのが普通であり従って、クリ
ーニング後の潜像担持体表面にも若干のトナーが付着す
るのを避け難い。このような状態で潜像担持体表面の反
射率に従って基準電圧vrefを得ると付着トナーにより基
準電圧が正しい値から変化して本来のトナー濃度検出に
狂いが生じる。
潜像担持体の残留電荷は潜像担持体の疲労などにより
経時的に変化するので、それに応じて画像濃度制御が不
安定になる。そして、この不安定さはフォトセンサーの
感度が高い程著しくなるのである。
（目的）
本発明は、上述した事情に鑑みてなされたものであっ
て、その目的とするところは、フォトセンサーを用い
て、安定した画像濃度制御を行い得る、新規な画像濃度
制御方法の提供にある。
（構成）
以下、本発明を説明する。
本発明は、潜像担持体表面の反射率に応じた信号と、
定められた条件で上記潜像担持体上に形成されたトナー
像の反射率に応じた信号を比較することにより作像条件
を制御し、画像濃度を制御する方法であるが、その特徴
とするところは、潜像担持体表面の反射率に応じた信号
およびトナー像の反射率に応じた信号をフォトセンサー
を用いて得、上記潜像担持体表面の反射率に応じた信号
を得るとき、現像剤と潜像担持体表面とを非接触状態と
する点にある。
潜像担持体表面の反射率に応じた信号を得るとき、現
像剤と潜像担持体表面とを非接触状態とするので、上記
表面の反射率に応じた信号を得るとき、潜像担持体の表
面にはトナーの付着が無い。
潜像担持体表面の反射率に応じた信号を得るのは定期
的に行えばよく、各画像記録プロセスごとに行う必要は
必ずしもない。
現像剤と潜像担持体表面とを非接触状態にするとは、
現像手段において現像剤を保持している現像ローラー
を、現像部から退避せしめることにより、該現像ローラ
ーが保持する現像剤が潜像担持体表面に付着しないよう
にすることを意味する。なお、本発明は上の説明からも
理解されるようにカラートナーを用いる画像記録装置に
対して有効であるが、勿論通常の黒色トナーを用いるモ
ノクロ、カラー、多色、２色等の各種複写機、プリンタ
ー等にも有効に適用できる。
（実施例）
以下、具体的な実施例に即して説明する。
第１図は、本発明の１実施例を説明するための図であ
る。図示されているのは、現像手段として回転式の多色
現像装置12を用いた静電複写装置の要部であり、符号10
は潜像担持体としての光導電性の感光体、符号14はクリ
ーニング装置、符号Ｓは第２図（Ｂ）に示す如き、検出
角120゜のフォトセンサーを示している。
第１図（Ａ）は通常の現像状態を示している。この図
では赤色トナーを用いる現像ローラーＡが現像部に配備
され、同ローラーＡの現像剤は潜像担持体10に接触して
いる。このように現像剤が潜像担持体表面に接触してい
る状態では、潜像担持体の表面をクリーニング装置14で
いくらきれいにクリーニングしても残留電位等により、
若干のトナーが潜像担持体に付着してしまうので、その
ような状態で潜像担持体表面の反射率に応じた信号を得
ても、基準電圧Vrefは正しい値を与えない。
そこで、潜像担持体表面の反射率に応じた信号を得る
とき、現像剤と潜像担持体表面とを非接触状態にするの
であるが、第１図の実施例では同図（Ｂ）の示すよう
に、現像装置12の現像ローラーA,B,Cのいずれも現像部
から退避させる。このようにすれば潜像担持体にトナー
が付着しないので潜像担持体表面自体の反射率に応じた
信号を正しく得ることができる。
潜像担持体の表面の反射率による信号Vrefは、定期的
にこれを検知し、所定のトナー像から得られる信号Vsp
との比Vsp/Vrefにより画像濃度の制御を行うのである。
通常の単色現像装置を用いるときは、潜像担持体に現
像剤を接触させないようにするために、現像装置を現像
位置から退避させるとか、あるいは現像部への現像剤の
汲上げを停止するとかすれば良い。
（効果）
以上、本発明によれば新規な画像濃度制御方法を提供
できる。この方法は上記の如き構成となっているので、
潜像担持体表面の反射率に応じた信号を得るとき、現像
剤と潜像担持体表面とが非接触状態であり、上記表面の
反射率に応じた信号を得るとき、潜像担持体の表面には
トナーの付着が無く、従って、基準電圧Vrefを常に正確
に検出できるので、常に安定した画像濃度制御を行うこ
とができる。
なお、フォトセンサーとして、検出角の大きいものを
用いると、トナー像の濃度を精度良く検出できるので、
画像濃度制御の精度を高めることが可能になる。
なお、上記検出角の大きいフォトセンサーは感度が高
いので、このセンサーを用いて潜像担持体表面の汚れ具
合を検知し、その値に応じて地肌汚れを取り除くように
現像バイアス電圧や露光量を変えるようにすることもで
きる。Description: TECHNICAL FIELD The present invention relates to an image density control method. (Prior Art) The developing bias is determined by comparing a signal corresponding to the reflectance of the surface of the latent image carrier with a signal corresponding to the reflectance of the toner image formed on the latent image carrier under predetermined conditions. A method of controlling an image density by controlling image forming conditions such as a voltage, a charge amount, and an exposure light amount is known in relation to a copying machine or a printer. In recent years, image recording apparatuses using color toner, such as color copying machines and color printers, multicolor and two-color copying machines and printers, have been increasing. A signal corresponding to the surface of the latent image carrier or the reflectance of the toner image is generally obtained using a photosensor. A photosensor is a device in which a light source and a light receiving element are integrally assembled, irradiating light from the light source onto the surface of the latent image carrier and the toner image, receiving reflected light by the light receiving element, and performing photoelectric conversion. Signal. In relation to such a photosensor, the detection angle is defined as follows. That is, the detection angle is defined as the sum of the incident angle of the light illuminating the reflectance detection target such as the latent image carrier and the reflection angle of the reflected light received by the light receiving element. Incidentally, the reflectance from the toner image is detected by determining the density of the toner image based on the reflectance of the toner image formed on the latent image carrier under a certain condition, and based on the density of the image to be recorded. It has been found that when the toner image is formed of color toner, the sensitivity of the photosensor depends on the detection angle. For example, in the photosensor S1 shown in FIG.
The light emitted from the light source 20 to the latent image carrier 10 and the light receiving element 22
The detection angle between the reflected light and the reflected light is 60 °, but if the red toner adheres to the latent image carrier 10, the output signal voltage of the photosensor is changed to the third signal in accordance with the amount of the adhered red toner. It changes like the curve 3-2 in the figure. The vertical axis in FIG. 3 is the output voltage signal, and the horizontal axis is the red toner adhesion amount. However, the second
When a photosensor S having a detection angle of 120 ° formed by the light emitted from the light source 30 and the reflected light received by the light receiving element 32 as shown in FIG. Accordingly, it changes as shown by a curve 3-1 in FIG. Therefore, in order to detect the density of the color toner image formed on the latent image carrier under a predetermined condition, it is preferable to perform high-sensitivity detection using a photosensor having a large detection angle. On the other hand, in FIG. 3, the output signal voltage of the photosensor when the toner adhesion amount on the horizontal axis is 0 gives the reflectance of the latent image carrier 10 itself, and the density detection of the toner image is performed on the surface of the latent image carrier. The reference voltage v
ref and the ratio V to the signal voltage V sp based on the reflectance of the toner image
This is performed by sp / v ref , and image density control is performed based on the value. However, when the sensitivity of the photosensor increases, even if a small amount of residual toner adheres to the surface of the latent image carrier, the photosensor detects this and changes the reference voltage vref . Conventionally, in the developing section, the surface of the latent image carrier is always in contact with the developer. On the other hand, on the surface of the latent image carrier,
Normally, a small amount of charge remains, so that it is difficult to avoid that a small amount of toner adheres to the surface of the latent image carrier after cleaning. In such a state, if the reference voltage vref is obtained according to the reflectance of the surface of the latent image carrier, the reference voltage changes from a correct value due to the adhered toner, and the original toner density detection is disturbed. Since the residual charge of the latent image carrier changes over time due to fatigue of the latent image carrier, image density control becomes unstable accordingly. This instability becomes more significant as the sensitivity of the photosensor is higher. (Purpose) The present invention has been made in view of the above circumstances, and a purpose thereof is to provide a novel image density control method capable of performing stable image density control using a photosensor. It is in. (Configuration) Hereinafter, the present invention will be described. The present invention provides a signal according to the reflectance of the latent image carrier surface,
This method controls image forming conditions by comparing signals corresponding to the reflectance of a toner image formed on the latent image carrier under a predetermined condition, thereby controlling image density. However, when a signal corresponding to the reflectance of the latent image carrier and a signal corresponding to the reflectance of the toner image are obtained using a photosensor, and a signal corresponding to the reflectance of the latent image carrier is obtained, The point is that the developer and the surface of the latent image carrier are brought into a non-contact state. When a signal corresponding to the reflectance of the latent image carrier is obtained, the developer and the surface of the latent image carrier are brought into a non-contact state. There is no toner adhesion on the surface of. The signal corresponding to the reflectance of the surface of the latent image carrier may be obtained periodically, and need not always be obtained for each image recording process. To make the developer and the surface of the latent image carrier in a non-contact state,
By retreating the developing roller holding the developer in the developing means from the developing section, it means that the developer held by the developing roller is prevented from adhering to the surface of the latent image carrier. Although the present invention is effective for an image recording apparatus using a color toner as understood from the above description, it is needless to say that various types of copying such as monochrome, color, multicolor, and two-color using a normal black toner can be used. It can be applied effectively to machines, printers, etc. (Example) Hereinafter, a description will be given according to a specific example. FIG. 1 is a diagram for explaining one embodiment of the present invention. Illustrated is a main part of an electrostatic copying apparatus using a rotary multicolor developing device 12 as a developing means.
Reference numeral 14 denotes a photoconductive photosensitive member as a latent image carrier, reference numeral 14 denotes a cleaning device, and reference numeral S denotes a photosensor having a detection angle of 120 ° as shown in FIG. 2 (B). FIG. 1A shows a normal developing state. In this figure, a developing roller A using red toner is provided in the developing section, and the developer of the roller A is in contact with the latent image carrier 10. In such a state where the developer is in contact with the surface of the latent image carrier, no matter how clean the surface of the latent image carrier is cleaned by the cleaning device 14, due to residual potential, etc.
Since a slight amount of toner adheres to the latent image carrier, even if a signal corresponding to the reflectance of the surface of the latent image carrier is obtained in such a state, the reference voltage Vref does not give a correct value. Therefore, when a signal corresponding to the reflectance of the surface of the latent image carrier is obtained, the developer and the surface of the latent image carrier are brought into a non-contact state. In the embodiment shown in FIG. As shown, all of the developing rollers A, B, and C of the developing device 12 are retracted from the developing section. In this case, since the toner does not adhere to the latent image carrier, a signal corresponding to the reflectance of the surface of the latent image carrier itself can be obtained correctly. A signal Vref based on the reflectance of the surface of the latent image carrier is periodically detected, and a signal Vsp obtained from a predetermined toner image is detected.
The image density is controlled by the ratio Vsp / Vref . When using a normal single-color developing device, in order to prevent the developer from coming into contact with the latent image carrier, it is necessary to retract the developing device from the developing position or stop pumping the developer to the developing section. Good. (Effects) As described above, according to the present invention, a novel image density control method can be provided. Since this method is configured as described above,
When obtaining a signal corresponding to the reflectance of the latent image carrier surface, the developer is in a non-contact state with the latent image carrier surface, and when obtaining a signal corresponding to the reflectance of the surface, the latent image carrier is Since no toner adheres to the surface and the reference voltage Vref can always be detected accurately, stable image density control can always be performed. If a photosensor having a large detection angle is used, the density of the toner image can be accurately detected.
It is possible to increase the accuracy of image density control. Since the photosensor having a large detection angle has high sensitivity, the degree of dirt on the surface of the latent image carrier is detected using this sensor, and the developing bias voltage and the amount of exposure are adjusted so as to remove background dirt according to the value. It can be changed.
【図面の簡単な説明】
第１図は、本発明の１実施例を説明するための図、第２
図および第３図は、フォトセンサーとその検出角を説明
するための図である。
10……潜像担持体、12……回転式の多色現像装置、14…
…クリーニング装置、Ｓ……検出角120゜のフォトセン
サーBRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining one embodiment of the present invention, FIG.
FIG. 3 and FIG. 3 are diagrams for explaining the photosensor and its detection angle. 10 ... Latent image carrier, 12 ... Rotary multicolor developing device, 14 ...
... Cleaning device, S ... Photosensor with a detection angle of 120 °
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭57−195256（ＪＰ，Ａ) 特開 昭61−231572（ＪＰ，Ａ) 特開 昭59−48776（ＪＰ，Ａ) 特開 昭59−53869（ＪＰ，Ａ) 特開 昭62−15575（ＪＰ，Ａ) 実開 昭60−39055（ＪＰ，Ｕ) ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-57-195256 (JP, A) JP-A-61-231572 (JP, A) JP-A-59-48776 (JP, A) JP-A-59-53869 (JP, A) JP-A-62-15575 (JP, A) 60-39055 (JP, U)
Claims (1)
た条件で上記潜像担持体上に形成されたトナー像の反射
率に応じた信号とに基づいて画像濃度を制御する画像濃
度制御方法において、 潜像担持体表面の反射率に応じた信号およびトナー像の
反射率に応じた信号を、フォトセンサーを用いて得、 上記潜像担持体表面の反射率に応じた信号を得るとき、
現像手段の現像ローラーを現像部から退避せしめること
により、上記現像ローラーに保持された現像剤が上記潜
像担持体表面に付着しないようにすることを特徴とす
る、画像濃度制御方法。(57) [Claims] Image density control for controlling the image density based on a signal corresponding to the reflectance of the surface of the latent image carrier and a signal corresponding to the reflectance of the toner image formed on the latent image carrier under predetermined conditions In the method, a signal corresponding to the reflectance of the surface of the latent image carrier and a signal corresponding to the reflectance of the toner image are obtained using a photosensor, and a signal corresponding to the reflectance of the surface of the latent image carrier is obtained. ,
An image density control method, wherein a developing roller of a developing unit is retracted from a developing unit so that a developer held by the developing roller does not adhere to the surface of the latent image carrier.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62252015A JP2709062B2 (en) | 1987-10-06 | 1987-10-06 | Image density control method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62252015A JP2709062B2 (en) | 1987-10-06 | 1987-10-06 | Image density control method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0193754A JPH0193754A (en) | 1989-04-12 |
| JP2709062B2 true JP2709062B2 (en) | 1998-02-04 |
Family
ID=17231390
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62252015A Expired - Lifetime JP2709062B2 (en) | 1987-10-06 | 1987-10-06 | Image density control method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2709062B2 (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57195256A (en) * | 1981-05-27 | 1982-11-30 | Ricoh Co Ltd | Controlling method for toner density |
| JPS5948776A (en) * | 1982-09-13 | 1984-03-21 | Ricoh Co Ltd | Photo sensor output correction device |
| JPS6039055U (en) * | 1983-08-01 | 1985-03-18 | カシオ計算機株式会社 | Developing device for two-color reproduction |
| JPH0721673B2 (en) * | 1985-04-06 | 1995-03-08 | キヤノン株式会社 | Image forming device |
-
1987
- 1987-10-06 JP JP62252015A patent/JP2709062B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0193754A (en) | 1989-04-12 |
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