Apparatus for reading a film image with controllable illumination and threshold value

Claims

What is claimed is:

1. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading image recorded on the film illuminated by said illuminating means and for outputting image signals representing the image;

first detection means for detecting an image density of the image recorded on the film on the basis of the image signals from said reading means;

second detection means for detecting a base density of the film on the basis of the image signals from said reading means;

means for quantizing the image signals outputted from said reading means; and

means for determining a threshold value for quantizing the image signals on the basis of the thus detected image density and base density.

2. A film image reading apparatus according to claim 1, wherein said quantizing means is adapted to compare the image signals with the threshold value so as to generate binary image signals.

3. A film image reading apparatus according to claim 1, wherein said first detection means is adapted to detect the image density on the basis of a peak value of the image signals from said reading means.

4. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading line by line the image recorded on the film illuminated by said illuminating means and for outputting image signals representing the image;

means for dividing the image signals of each reading line, outputting from said reading means, into plural blocks, each block including a predetermined amount of the image signals;

means for detecting a respective peak value of the image signals in each block;

means for quantizing the image signals outputted from said reading means; and

means for determining a threshold value for quantizing the image signals on the basis of the the detected peak value of each blocks.

5. A film image reading apparatus according to claim 4, wherein said determining means is adapted to determine the threshold value on the basis of a frequency of the detected peak values.

6. A film image reading apparatus according to claim 4, wherein said detecting means is adapted to detect the peak value of image signals corresponding to a predetermined area of the film.

7. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading the image recorded on the film illuminated by said illuminating means and outputting image signals representing the image;

means for detecting an image density of an image corresponding to a predetermined partial area of the film on the basis of the image signals from said reading means;

means for quantizing the image signal outputted from said reading means; and

means for determining a threshold value for quantizing the image signals on the basis of the detected density of an image.

8. A film image reading apparatus according to claim 7, wherein said quantizing means is adapted to compare the image signals with the threshold value so as to generate binary image signals.

9. A film image reading apparatus according to claim 7, wherein said detecting means is adapted to detect the image density on the basis of the peak value of the image signal outputted from said reading means.

10. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading the image recorded on the film illuminated by said illuminating means and outputting image signals representing the image;

first detection means for detecting an output value of said reading means in a state where the film is not illuminated by said illuminating means;

second detection means for detecting an image density of the image recorded on the film on the basis of the image signals from said reading means in a state where the film is illuminated by said illuminating means;

means for quantizing the image signals outputted from said reading means; and

means for determining a threshold value for quantizing the image signals on the basis of the thus detected output value and image density.

11. A film image reading apparatus according to claim 10, wherein said quantizing means is adapted to compare the image signals with the threshold value so as to generate a binary image signal.

12. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading the image recorded on the film illuminated by said illuminating means and for outputting image signals representing the image;

first detection means for detecting a base density of the film on the basis of an output from said reading means when said reading means reads a non-image area of the film illuminated by said illuminating means; and

means for determining the amount of light for said illuminating means according to the thus detected base density; and

second detection means for detecting an image density of the image based on an output from said reading means when said reading means reads the image recorded on the film illuminated with the thus determined amount of light by said illuminating means.

13. A film image reading apparatus according to claim 12, wherein said second detection means is adapted to detect the image density on the basis of a peak value of the image signals from said reading means.

14. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading the image recorded on the film illuminated by said illuminating means and for outputting image signals representing the image;

first detection means for detecting an image density of the image recorded on the film on the basis of the image signals from said reading means;

second detection means for detecting a base density of the film on the basis of the image signals from said reading means; and

means for identifying an abnormality in said illuminating means on the basis of the thus detected image density and base density.

15. A film image reading apparatus according to claim 14, further comprising means for quantizing the image signals from said reading means on the basis of the thus detected image density and base density.

16. A film image reading apparatus according to claim 14, wherein said first detection means is adapted to detect the image density on the basis of a peak value of the image signals from said reading

17. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading the image recorded on the film illuminated by said illuminating means and for outputting image signals representing the image;

first detection means for detecting an image density of the image recorded on the film on the basis of an output from said reading means;

second detection means for detecting a base density of the film on the basis of an output from said reading means; and

means for identifying the position of the image on the film on the basis of the thus detected image density and base density, to determine whether the image is proper or not proper for reading.

18. A film image reading apparatus according to claim 17, further comprising means for quantizing the image signals from said reading means on the basis of the thus detected image density and base density.

19. A film image reading apparatus according to claim 17, wherein said first detection means is adapted to detects the image density on the basis of a peak value of the image signals from said reading means.

20. A film image reading apparatus according to claim 1, wherein said first detection means is adapted to detect the image density of an image corresponding to a predetermined partial area of the film.

21. A film image reading apparatus according to claim 1, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by a film.

22. A film image reading apparatus according to claim 1, further comprising means for moving a reading position on the film of said reading means.

23. A film image reading apparatus according to claim 1, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

24. A film image reading apparatus according to claim 4, wherein said quantizing means is adapted to compare the image signals with the threshold value so as to generate binary image signals.

25. A film image reading apparatus according to claim 4, further comprising second detecting means for detecting a base density of the film, wherein said determining means is adapted to determine the threshold value in consideration of the detected base density.

26. A film image reading apparatus according to claim 4, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by a film.

27. A film image reading apparatus according to claim 4, further comprising means for moving a reading position of said reading means on the film.

28. A film image reading apparatus according to claim 4, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

29. A film image reading apparatus according to claim 7, further comprising second detecting means for detecting a base density of the film, wherein said determining means is adapted to determine the threshold value in consideration of the detected base density.

30. A film image reading apparatus according to claim 7, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by a film.

31. A film image reading apparatus according to claim 7 further comprising means for moving a reading position of said reading means on the film.

32. A film image reading apparatus according to claim 7, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

33. A film image reading apparatus according to claim 7, wherein said first detection means comprise means for extracting the image signals representing the image corresponding to a predetermined partial area of the film.

34. A film image reading apparatus according to claim 10, wherein said second detection means is adapted to detect the image density on the basis of a peak value of the image signals from said reading means.

35. A film image reading apparatus according to claim 10, wherein said second detection means is adapted to detect the image density of an image corresponding to a predetermined partial area of the film.

36. A film image reading apparatus according to claim 10, further comprising third detection means for detecting a base density of the film, wherein said determining means is adapted to determine the threshold value in consideration of the detected base density.

37. A film image reading apparatus according to claim 10, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by a film.

38. A film image reading apparatus according to claim 10, further comprising means for moving a reading position of said reading means on the film.

39. A film image reading apparatus according to claim 10, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

40. A film image reading apparatus according to claim 12, further comprising means for applying an electric power to said illuminating means in order to illuminate the film with the determine amount of light.

41. A film image reading apparatus according to claim 12, wherein said second detection means is adapted to detect the image density of an image corresponding to a predetermined partial area of the film.

42. A film image reading apparatus according to claim 12, further comprising means for quantizing the image signals outputted from said reading means and means for determining a threshold value for quantizing the image signals on the basis of the image density detected by said second detection means.

43. A film image reading apparatus according to claim 12, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by a film.

44. A film image reading apparatus according to claim 12, further comprising means for moving a reading position of said reading means on the film.

45. A film image reading apparatus according to claim 12, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

46. A film image reading apparatus according to claim 14, wherein said identifying means is adapted to identify the abnormality in said illuminating means on the basis of a differential between the detected image density and the detected base density.

47. A film image reading apparatus according to claim 14, further comprising means for displaying a result of identification by said identifying means.

48. A film image reading apparatus according to claim 14, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by a film.

49. A film image reading apparatus according to claim 14, further comprising means for moving a reading position of said reading means on the film.

50. A film image reading apparatus according to claim 14, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

51. A film image reading apparatus according to claim 17, wherein said identifying means is adapted to identify, whether or not the position of the image of the film is proper on the basis of a differential between the detected image density and the detected base density.

52. A film image reading apparatus according to claim 17, further comprising means for displaying a result of identification by said identifying means.

53. A film image reading apparatus according to claim 17, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by a film.

54. A film image reading apparatus according to claim 17, further comprising means for moving a reading position of said reading means on the film.

55. A film image reading apparatus according to claim 17, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

56. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading the image recorded on the film illuminated by said illuminating means and for outputting image signals representing the image;

first detection means for detecting an image density of the image recorded on the film on the basis of the image signals form said reading means;

second detection means for detecting a base density of the film on the basis of the image signals from said reading means;

means for processing the image signals output from said reading means, for image reproduction; and

means for determining a parameter for processing the image signals on the basis of the thus detected image density and base density.

57. A film image reading apparatus according to claim 56, wherein said processing means comprises quantizing means for quantizing the image signals output from said reading means, and said determining means determines a threshold value for quantizing the image signals as the parameter.

58. A film image reading apparatus according to claim 57, wherein said quantizing means is adapted to compare the image signals with the threshold value to generate binary signals.

59. A film image reading apparatus according to claim 56, wherein said first detection means is adapted to detect the image density on the basis of a peak value of the image signals from said reading means.

60. A film image reading apparatus according to claim 56, wherein said first detection means is adapted to detect the image density of an image corresponding to a predetermined partial area of the film.

61. A film image reading apparatus according to claim 56, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by the film.

62. A film image reading apparatus according to claim 56, further comprising means for moving a reading position on the film of said reading means.

63. A film image reading apparatus according to claim 56, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

64. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading line by line the image recorded on the film illuminated by said illuminating means and/or outputting image signals representing the image;

means for dividing the image signals of each reading line, output from said reading means, into plurality blocks, each block including a predetermined amount of the image signals;

means for detecting a respective peak value of the image signals in each block;

means for processing the image signals output from said reading means, for image reproduction; and

means for determining a parameter for processing the image signals on the basis of the detected peak value of each block.

65. A film image reading apparatus according to claim 64, wherein said processing means comprises quantizing means for quantizing the image signals output from said reading means, and said determining means determines a threshold value for quantizing the image signals as the parameter.

66. A film image reading apparatus according to claim 64, wherein said determining means is adapted to determine the parameter on the basis of the frequency of the detected peak values.

67. A film image reading apparatus according to claim 64, wherein said detecting means is adapted to detect the peak, value of image signals corresponding to a predetermined area of the film.

68. A film image reading apparatus according to claim 65, wherein said quantizing means is adapted to compare the image signals with the threshold value to generate binary image signals.

69. A film image reading apparatus according to claim 64, further comprising second detecting means for detecting a base density of the film, wherein said determining means is adapted to determine the parameter in consideration of the detected base density.

70. A film image reading apparatus according to claim 64, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by the film.

71. A film image reading apparatus according to claim 64, further comprising means for moving a reading position of said reading means on the film.

72. A film image reading apparatus according to claim 64, further comprising means for displaying an enlarged image, which is an enlargement of the image recorded on the film.

73. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading the image recorded on the film illuminated by said illuminating means and outputting image signals representing the image;

means for detecting an image density of an image corresponding to as predetermined partial area of the film on the basis of the image signals from said reading means;

means for processing the image signal output from said reading means, for image reproduction; and

means for determining a parameter for processing the image signals on the basis of the detected density of an image.

74. A film image reading apparatus according to claim 73, wherein said processing means comprises quantizing means for quantizing the image signals output from said reading means, and said determining means determines a threshold value for quantizing the image signals as a parameter.

75. A film image reading apparatus according to claim 74, wherein said quantizing means is adapted to compare the image signals with the threshold value to generate binary image signals.

76. A film image reading apparatus according to claim 73, wherein said detecting means is adapted to detect the image density on the basis of the peak value of the image signal output from said reading means.

77. A film image reading apparatus according to claim 73, further comprising second detecting means for detecting a base density of the film, wherein said determining means is adapted to determine the parameter in consideration of the detected base density.

78. A film image reading apparatus according to claim 73, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by the film.

79. A film image reading apparatus according to claim 73, further comprising means for moving a reading position of said reading means on the film.

80. A film image reading apparatus according to claim 73, further comprising means for displaying an enlarged image which is an enlargement of the image recorded on the film.

81. A film image reading apparatus according to claim 73, wherein said first detection means comprises means for extracting the image signals representing the image corresponding to a predetermined partial area of the film.

82. A film image reading apparatus comprising:

means for illuminating a film on which an image is recorded;

means for reading the image recorded on the film illuminated by said illuminating means and outputting image signals representing the image;

first detection means for detecting an output value of said reading means in a state where the film is not illuminated by said illuminating means;

second detection means for detecting an image density of the image record on the film on the basis of the image signals from said reading means in a state where the film is illuminated by said illuminating means;

means for processing the image signals output from said reading means, for image reproduction; and

means for determining a parameter for processing the image signals on the basis of the thus detected output value and image density.

83. A film image reading apparatus according to claim 82, wherein said processing means comprises quantizing means for quantizing the image signals output from said reading means, and said determining means determines a threshold value for quantizing the image signals as a parameter.

84. A film image reading apparatus according to claim 83, wherein said quantizing means is adapted to compare the image signals with the threshold value to generate a binary image signal.

85. A film image reading apparatus according claim 82, wherein said second detection means is adapted to detect the image density on the basis of a peak value of the image signals from said reading means.

86. A film image reading apparatus according to claim 82, wherein said second detection means is adapted to detect the image density of an image corresponding to a predetermined partial area of the film.

87. A film image reading apparatus according to claim 82, further comprising third detection means for detecting a base density of the film, wherein said determining means is adapted to determine the parameter in consideration of the detected base density.

88. A film image reading apparatus according to claim 82, wherein said reading means comprises a linear image sensor capable of photoelectric conversion of light transmitted by the film.

89. A film image reading apparatus according to claim 82, further comprising means for moving a reading position of said reading means on the film.

90. A film image reading apparatus according to claim 82, further comprising means for displaying an enlarged image which is an enlargement of the image recorded on the film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image reading apparatus for illuminating a film bearing an image and reading said image from the light transmitted by the thus illuminated film.

2. Related Background Art

There has already been proposed an apparatus for high-density recording of the information generated in a large quantities, such as of documents, onto microfilms and for reading the recorded image on said microfilms, when required, for reproducing on a recording sheet.

In such apparatus the microfilm is exposed to light, and the density of the light transmitted by the microfilm is detected by an image sensor such as a CCD to obtain an electrical image signal.

For converting the thus obtained image signal for example into a binary signal representing black and white, there is generally conducted a comparison of said image signal with a predetermined threshold value. However the density of image recorded on the microfilm is variable according to the photographing condition, and the use of a fixed threshold value for binary encoding may result in a very dark or faint output image. It is therefore conceived to vary the threshold value according to the density of the recorded image.

Consequently, it is known to photoelectrically detect the amount of light transmitted by the microfilm, in order to determine the threshold value according to the density of recorded image. However, the size and position of the images recorded on the microfilm are not constant, so that, if the threshold value is determined, for example, by the light transmitted by the entire area of film, the exact image density cannot be detected as the transmitted light through a non-image area affects the determination of the threshold value.

On the other hand, it is also conceivable to determine the threshold value from the peak density of the recorded image. However, if characters and symbols of different sizes are present in an image, an image density corresponding to a large character is detected as the peak value, and small characters may be omitted in the reproduced image when binary encoding is conducted with a threshold value determined according to such peak value.

In addition, the background or base density varies according to the type of the microfilm, and the image contrast varies according to such base density even if the image density recorded on the film is constant. Consequently, a threshold value, which is determined solely by the image density recorded on the film, may not be able to achieve exact binary encoding of images close to the background or base density.

Also, the output of the image sensor may fluctuate due to time-dependent change or the circumferential condition of the light source and of the image sensor, thus affecting the determination of an appropriate threshold value.

The output image signal is influenced by the amount of light emitted from the light source for illuminating the microfilm. It is therefor conceivable to control the amount of light at a constant value. However, as explained above, the amount of light transmitted by the microfilm is governed by the base density thereof, which is variable according to the type of film and the developing conditions thereof. Consequently, a constant amount of light alone does not ensure satisfactory image reading from different films.

It is therefore conceivable to detect the amount of light transmitted by the film and to regulate said amount of light to be always to an optimum value regardless of the base density. However, such method of control with the transmitted light is unable to achieve appropriate control in the case that film has a local smear or scar.

Also, in such conventional apparatus, the image reading of microfilm has required an operator for confirming that an image frame on the microfilm is projected in a correct position, through inspection of a projection screen, since otherwise a non-image area between image frames on the film may be erroneously read.

SUMMARY OF THE INVENTION

In consideration of the foregoing, an object of the present invention is to enable satisfactory reading of an image recorded on a microfilm or the like.

Another object of the present invention is to enable, in reading an image recorded on a film such as a microfilm, appropriate determination of a threshold value for digitizing of image signal according to the image density.

Still another object of the present invention is to enable satisfactory reading of an image recorded on a film and containing characters and symbols of different sizes.

Still another object of the present invention is to enable, in reading an image recorded on a film such as microfilm satisfactory image reading by suitably regulating the amount of light to which the film is exposed.

Still another object of the present invention is to provide a film exposing apparatus capable of efficiently and securely an abnormality in a light source for illuminating a film.

Still another object of the present invention is to be exposed of a film is securely exposed in a correct exposing position.

According to the present invention, these objects are attained by provision of a film image reading apparatus having, according to one aspect of the invention, first and second detection means, which are respectively for detecting an image density of an image recording on an illuminated film, on the basis of image signals from a reading means, and for detecting a base density of the film on the basis of the image signals. The image signals are then quantized, using a threshold value determined on the basis of the detected image density and the base density. The image density may be determined using a peak value of the image signals.

According to another aspect of the invention, the image signals for each reading line are divided into plural block, each of which includes a predetermined amount of image signal, and a peak value of each block is detected. The image signals are then quantized using a threshold value determined on the basis of the detected peak value for each block.

According to another aspect of the invention, quantization is performed using a threshold value determined on the basis a detected density of an image corresponding to a predetermined partial area of an illuminated film.

According to still another aspect of the invention, an output value from a reading means is detected while a film bearing an image is not illuminated, and a second detection means detects image density of the image from signals from the reading means, while the film is illuminated. A quantization threshold value is determined on the basis of the thus detected up value and image density.

According to another aspect of the invention, a first detection means detects a base density of a film output during reading of a non-image area of the film illuminated by an illuminating means, the amount of light of the illuminating means is determined according to the detected base density, and a second detection means detects image density of the image based on an output from the reading means during reading of the image illuminated with the thus determined amount of light.

The foregoing and still other objects of the present invention, and the advantages thereof, will become fully apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a microfilm reading apparatus embodying the present invention;

FIG. 2, consisting of FIGS. 2A and 2B, is a block diagram showing an example of a circuit for processing an image signal;

FIG. 3 is a view showing a threshold determining area;

FIG. 4 is a block diagram of a line address setting circuit;

FIG. 5 is a block diagram of a block address setting circuit;

FIG. 6 is a chart showing a scanning line dividing operation;

FIG. 7 is a chart showing a peak value fetching operation;

FIG. 8 is a block diagram of a base density detecting circuit;

FIG. 9 is a chart showing the function of said base density detecting circuit;

FIG. 10 is a view showing the mode of data fetching from the threshold determining area;

FIGS. 11 (I), (II), and (III) are charts showing examples of histograms;

FIG. 12 is a chart showing the relation between the base density and correction coefficient;

FIG. 13 is a chart showing the relation between the spatial frequency and contrast;

FIG. 14, which consists of FIGS. 14A and 14B is a flow chart showing the procedure of determining the threshold value;

FIG. 15, which consists of FIGS. 15A and 15B, is a flow chart showing the procedure of determining the amount of light;

FIG. 16 is a charts showing examples of histograms relating to detection of a lamp failure;

FIG. 17 is a flow chart showing the procedure of detecting a lamp failure;

FIG. 18 is charts showing example of histograms relating to film position; and

FIG. 19 is a flow chart show