JPH0470808A - Electrostatic image reproduction method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an electrostatic image reproduction method that visualizes an electrostatic image by utilizing the change in anisotropy of an electro-optic crystal depending on an electric field. It is related to.

[Prior Art] Conventionally, a photoreceptor having a photoconductive layer formed on a conductive layer and a charge holding medium having an insulating layer formed on the conductive layer are placed facing each other, and a voltage is applied between both groove conductive layers. BACKGROUND ART Imagewise exposure is performed, charges are accumulated on a charge holding medium according to the amount of exposure, and an electrostatic latent image is recorded.

The charge holding medium 5 shown in FIG. 4 has an electrostatic image recorded thereon in this manner. When the electro-optic crystal 4 is arranged to face the charge-holding medium 5 and the electrode 4a formed on the electro-optic crystal 4 and the electrode 5a of the charge-holding medium 5 are connected, the electro-optic crystal 4 is charged with the charged charge of the charge-holding medium 5. An electric field is applied according to the

Since the change in the optical anisotropy of the electro-optic crystal 4 is proportional to the magnitude of the electric field, it changes depending on the amount of electrostatic charge.

At this time, when light is irradiated from the light source 1 to the electro-optic crystal 4 through the polarizer 2, the plane of polarization of the polarized light from the polarizer 2 rotates according to the amount of electrostatic charge on the charge retention medium 5 due to the optical anisotropy of the electro-optic crystal 4. .

When this polarized light whose plane of polarization has been rotated is extracted through the analyzer 6, an amount of transmitted light corresponding to the amount of electrostatic charge on the charge holding medium 5 is obtained, and it is possible to visualize an electrostatic image.

That is, the change in retardation Δφ is expressed by the following equation, where n is the refractive index, T is the electro-optic constant, E is the electric field strength, and λ is the optical path length.

λ Now, the thickness and dielectric constant of the electro-optic crystal, void, and charge holding medium are (dl, εl), (d2.ε2), respectively.
(d3.ε3), and if the image potential of the charge retention medium is Vs, then ε 3 ε 2 . When the charge retention medium is in contact with the electro-optic crystal, d, = 0
), and when the charge retention medium is metallic (d3=0), V s = E d + .
...(3) That is, Eβ in equation (1) corresponds to the potential Vs and becomes 1, f = 2d in the case of a reflective type, f - d in the case of a transmission type, and by finding Δφ, The potential Vs on the surface of the charge holding medium, that is, the amount of charge can be determined.

[Problem to be solved by the invention]

FIG. 5 is a diagram showing the relationship between the surface potential of the latent image on the charge holding medium on the horizontal axis and the amount of transmitted light from the analyzer 6 on the vertical axis. The amount of transmitted light is sin” (Δφ/2),
As described above, since Δφ is proportional to the latent image surface potential, the amount of transmitted light draws a sine wave curve with respect to the latent image surface potential. Therefore, in the part A of FIG. 5 where the latent image surface potential is small, there is almost no change in the amount of transmitted light in response to a change in the surface potential, and therefore it could not be detected by the conventional method.

The present invention is intended to solve the above problems, and aims to provide an electrostatic image reproduction method that can obtain and detect a large change in the amount of transmitted light even in areas where the latent image surface potential is small. .

[Means to solve the problem]

In the present invention, a charge retention medium on which an electrostatic image is recorded and an electro-optic crystal whose optical anisotropy changes depending on the electric field are placed facing each other, and the optical properties of the electro-optic crystal are changed depending on the electrostatic image potential. In an electrostatic image reproduction method that reproduces an electrostatic image by changing the polarization state of polarized light transmitted through an electro-optic crystal, a phase compensator is placed behind the electro-optic crystal, and the electrostatic image potential O
The feature is that the point position is shifted.

[Effect]

The present invention irradiates polarized light with appropriate phase compensation onto an electro-optic crystal to which an electric field corresponding to an electrostatic latent image is applied, and detects changes in the polarization state, and uses a phase compensation device. By moving the O point position of the latent image surface potential, it is possible to reproduce an image in a portion where the amount of transmitted light changes largely with respect to a change in the latent image surface potential.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining image reproduction according to the present invention.
The same numbers as in the figure indicate the same contents.

In addition, 3 is a phase compensation device, 3a is an electro-optic crystal, 3b,
3c is a transparent electrode, and ■ is a variable DC power supply.

From the light from the light source 1, only the linearly polarized light with a predetermined polarization angle is extracted by the polarizer 2, and this linearly polarized light is sent to the variable DC power supply V.
As a result, the phase of the light changes by a predetermined angle through a phase compensator made of electro-optic crystal 3 to which a predetermined voltage is applied, and the electro-optic crystal 4 is irradiated in this state. The light transmitted through the electro-optic crystal 4 and the charge holding medium 5 is detected by an analyzer 6 for a change in the light.

As mentioned above, the component detected by the analyzer 6 is sin'' (Δφ/2+θ) where Δφ is the phase change caused by the electro-optic crystal 4 and θ is the phase change caused by the electro-optic crystal 3.As mentioned above, Δφ is Corresponding to the magnitude of the electric field applied to the electro-optic crystal 4, △φ-0, that is, the position of θ in FIG. 2 corresponds to the latent image surface potential OV. This means that it has moved to the position of
At this position, since the amount of transmitted light changes greatly with respect to potential changes, it is possible to sufficiently detect and visualize the electrostatic image. Note that if θ is too large, the total amount of light transmitted through the analyzer 6 will increase, and the amount of change in light amount relative to the total amount of transmitted light will become small, resulting in a decrease in detection sensitivity.
θ needs to be set to a value that is not too large.

In this example, even if there is a change in thickness in the electro-optic crystal 3 shown in FIG. The electric field becomes larger, and the larger the thickness, the smaller the electric field, so changes in thickness do not appear in the detection output, so electro-optic crystals have the advantage of not requiring precise processing accuracy.

In the above embodiment, an electro-optic crystal was used as the phase compensation device, but as shown in FIG. Phase compensation may be performed using a phase plate, and it is also possible to use a λ/n plate (n is an integer).

In addition, when the electro-optic crystal 3 shown in FIG. 1 has natural birefringence, if the refractive index of one axis is nl, the refractive index of the axis perpendicular to this is n2, and the thickness is d, then (2π /λ)(nl
-n2)d phase change occurs, and if this varies, it will be detected as shading of the image, so it is desirable to have as little natural birefringence as possible.

Such materials include KDP (KH, PO,),
KD2P○,,ADP (NH,H,PO,)CuCC
ZnS, ZnTe, CdTe, GaP, GaAs, BS
O(B i 125 i 020), BG○(Bi,,
G e O2, ), etc.

〔Effect of the invention〕

As described above, according to the present invention, by irradiating the electro-optic crystal with phase-compensated polarized light, the zero point position of the latent image surface potential is moved, and an output can be obtained at a location where the amount of transmitted light changes largely in response to a change in the latent image potential. , a large change in the amount of transmitted light can be obtained even for a small latent image surface potential, making it possible to visualize with high accuracy.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining image reproduction according to the present invention, Fig. 2 is a diagram for explaining in detail the present invention for shifting the zero point position of the latent image surface potential, and Fig. 3 is a diagram for explaining the variable phase plate. Figure shown, 4th
5 are diagrams for explaining a conventional latent image visualization method. DESCRIPTION OF SYMBOLS 1... Light source, 2... Polarizer, 3... Phase compensator, 3a... Electro-optic crystal, 3b, 3c... Transparent electrode, ■... Variable DC power supply, 4... Electricity optical crystal,
5... Charge retention medium, 6... Analyzer. 1vA Applicant Dai Nippon Printing Co., Ltd. Agent Patent Attorney Masanobu Hirukawa (7 others) (d) 4a...Home Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) A charge retention medium on which an electrostatic image is recorded and an electro-optic crystal whose optical anisotropy changes depending on the electric field are placed facing each other,
In an electrostatic image reproduction method that changes the optical properties of an electro-optic crystal according to the electrostatic image potential and reproduces an electrostatic image by changing the polarization state of polarized light transmitted through the electro-optic crystal, a phase compensation device is installed behind the electro-optic crystal. An electrostatic image reproduction method characterized in that the electrostatic image potential zero point position is shifted. (2) The electrostatic image reproducing system according to claim 1, wherein the phase compensation device includes transparent electrodes provided on both sides of an electro-optic crystal, and a variable DC power source connected between both electrodes. (3) The phase compensation device is a variable phase plate or a λ/n plate (
2. The electrostatic image reproducing method according to claim 1, wherein n is an integer.