Image input system

Claim 2

An image input system for photoelectrically reading the image of an object and supplying electric signals representing the image to an image processing system, which image input system comprises: photoelectric conversion means (3) for photoelectrically reading the image to convert the image into electric analog signals analog-to-digital converter means (4) for converting the analog signals into N-bit digital signals; and digital data transformation means (6 or 8 to 11 and 16) for transforming the N-bit digital signals into M-bit digital signals indicating values in a prescribed linear relation to the optical density of the image and delivering the M-bit digital signals to the image processing system (7), N and M being integers satisfying N>M.

Claim 3

An image input system according to claim 1, wherein: the said linear relation is valid within a range of 0 D D 0 , D being the optical density of the image and D 0 being the optical density of the image and D 0 being the maximum value of reproducible optical density; and the digital data transformation means performs transformation means performs transformation on the basis of the following expression (a): where S N represents values indicated by the N-bit digital signals, S M represents values to be indicated by the M-bit digital signals in correspondence to the values S N , S NO represents a value S N corresponding to the value D 0 , and S M0 represents a value S M corresponding to the value D 0 .

Claim 4

An image input system according to claim 2, wherein: the digital data transformation means includes memory means (6) storing said values S w obtained on the basis of the expression (a) in respective addresses corresponding to the values S N as data respectively tp output corresponding said values S m as said M-bit digital signals every time said N-bit digital signals are inputted.

Claim 5

An image input system according to claim 1, comprising transformation characteristic specifying means (8, 9, 10, 11) inputting linear relation specifying data for selecting a desired linear relation thereby to supply transformation characteristics corresponding to the desired linear relation to the digital data transformation means (16).

Claim 6

An image input system according to claim 4, wherein the linear relation specifying data include two optical density values D min and D max indicating end points of the optical density range of the image and two values S min and S max indicating end points of range and values to be indicated by said M-bit digital signals; and digital data transformation means (16) performs transformation on the basis of the following expression (b) determined by said values D min , D max , S min and S max : where D represents the optical density of the image, D 0 represents the maximum value of reproducible optical density, S N represents values indicated by the N-bit digital signals, S M represents values to be indicated by the M-bit digital signals in correspondence to the values S N and S NO represents a value S N corresponding to the value D 0 , where and

Claim 7

An image input system according to claim 5, wherein the transformation characteristic specifying means includes operational means (11) for inputting data representing the values D min , D max , S min and S max to perform operation on the basis of the expression (b); and the digital data transformation means includes memory means storing the values S M in respective addresses corresponding to the values S N as data on the basis of outputs from the operationa 1 means to output corresponding values S M as said M-bit digital signals in response to inputting of the N-bit digital signals as address signals.

Claim 8

An image input system according to claim 4, wherein the linear relation specifying data is arbitrarily selectable from continuous values.

Claim 9

An image input system according to claim 4, wherein the linear relation specifying data is arbitrarily selectable from discrete values.

Claim 10

An image input device according to claim 4, wherein the linear relation is selected to limit transformation or boost transformation in the vicinity of respective ones of the maximum and minimum values of the optical density of the image.